Lidé

Ing. Karel Fliegel, Ph.D.

Všechny publikace

Regarding the quality of disparity estimation from distorted light fields

  • Autoři: Zizien, A., Ing. Karel Fliegel, Ph.D.,
  • Publikace: Signal Processing: Image Communication. 2022, 109 1-18. ISSN 0923-5965.
  • Rok: 2022
  • DOI: 10.1016/j.image.2022.116867
  • Odkaz: https://doi.org/10.1016/j.image.2022.116867
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Recent developments in the field of plenoptic imaging have directly coincided with standardisation efforts. Such efforts are in no small part reliant on quality evaluations. For traditional imaging modalities, such as static images and videos, subjective evaluations have played a very important part. The goal of most objective quality evaluations has been the correlation performance with subjective results. However, plenoptic modalities enable applications that rely more on the objective rather than subjective quality. As such, it is necessary to examine the performance of currently used objective quality metrics. The paper provides a study on the predictive abilities of objective quality metrics on the quality of light field disparity map estimation. The study measures the influence of distortions on light field disparity estimations; furthermore, the study examines how well can objective quality metrics predict the quality of the resulting disparity maps. None of the tested metrics showed satisfactory prediction performance. Thus, two metric fusion algorithms were also examined to see if either can further improve prediction accuracy. The metric fusion algorithms showed that the prediction can be significantly improved. A novel objective quality metric that would correlate well with both subjective and objective results could thus be introduced.

Cross-Content Evaluations in the Subjective Quality Assessment of Light Field Images

  • Autoři: Zizien, A., Ing. Karel Fliegel, Ph.D.,
  • Publikace: 2021 31st International Conference Radioelektronika (RADIOELEKTRONIKA). IEEE (Institute of Electrical and Electronics Engineers), 2021. ISBN 978-1-6654-1474-6.
  • Rok: 2021
  • DOI: 10.1109/RADIOELEKTRONIKA52220.2021.9420203
  • Odkaz: https://doi.org/10.1109/RADIOELEKTRONIKA52220.2021.9420203
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Plenoptic modalities, in general, have seen a steady increase in research activity in recent years. Advances in this field pose additional demands on the development of new compression algorithms, which could be used for efficient delivery and storage of the acquired data. Subjective assessments are a key part of the development process. In this work, we examine the differences between two passive methodologies for the subjective assessment of light field images; a rating methodology, introduced in our previous work, and a ranking methodology. Additionally, we analyse the impact and viability of cross-content evaluations on the results of the assessment. The resulting data are made publicly available and can be used to design new compression algorithms, subjective assessment methodologies, or objective quality metrics.

Highly compact and cost-effective 2-beam super-resolution structured illumination microscope based on all-fiber optic components

  • DOI: 10.1364/OE.420592
  • Odkaz: https://doi.org/10.1364/OE.420592
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Current super-resolution structured illumination microscopes (SR-SIM) utilize relatively expensive electro-optic components and free-space optics, resulting in large setups. Moreover, high power laser sources are required to compensate for the losses associated with generating the illumination pattern by diffractive optics. Here, we present a highly compact and flexible 2D SR-SIM microscope based on all-fiber optic components (fiberSIM). Fiber-splitters deliver the laser light to the sample resulting in the interference illumination pattern. A microelectromechanical systems (MEMS) based fiber switch performs rapid pattern rotation. The pattern phase shift is achieved by the spatial displacement of one arm of the fiber interferometer using a piezoelectric crystal. Compared with existing methods, fiberSIM is highly compact and significantly reduces the SR-SIM component cost while achieving comparable results, thus providing a route to making SR-SIM technology accessible to even more laboratories in the life sciences.

Activity profile, mass distribution index, radiants, and orbits of the 2018 Draconid meteor shower outburst

  • DOI: 10.1016/j.pss.2020.104871
  • Odkaz: https://doi.org/10.1016/j.pss.2020.104871
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    An outburst of Draconid meteor shower was predicted for October 8 to 9, 2018. Using a variety of video and photographic cameras covering a broad range of magnitudes, the shower activity profile was measured. The main peak was observed at the solar longitude , what is equivalent to UT. This result is in good agreement with other reports as well as with the predictions. Two other sub-peaks or enhancements of the activity were detected later in the night. The analysis of the mass distribution index evolution and the comparison with other experiments suggests that the later activity was probably caused by the mixture of the different trails of the stream which were more dispersed. The flux of the meteoroids was three to four times smaller in comparison with the 2011 Draconid outburst. When comparing the radiants and velocities of the observed meteors with the model data, good agreement was found for the right ascension and velocity but a small offset of about +0.5∘ was observed in declination. On the other hand, the mean main peak radiant fits well the model of Maslov (2011).

FFTMI: Features Fusion for Natural Tone-Mapped Images Quality Evaluation

  • Autoři: Krasula, L., Ing. Karel Fliegel, Ph.D., Le Callet, P.
  • Publikace: IEEE Transactions on Multimedia. 2020, 22(8), 2038-2047. ISSN 1520-9210.
  • Rok: 2020
  • DOI: 10.1109/TMM.2019.2952256
  • Odkaz: https://doi.org/10.1109/TMM.2019.2952256
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Tone-mapping is a crucial step in the task towards displaying high dynamic range (HDR) images on standard displays. Given the number of possible ways to tone-map such images, a development of an objective quality criterion, enabling selection of the most suitable tone-mapping operator (TMO) and setting its parameters in order to maximize the quality of the reproduction, is of high interest. In this paper, a new objective metric for natural tone-mapped images is proposed. It is based on fusion of several perceptually relevant features that have been carefully selected using an appropriate feature selection procedure. The outcome of the selection also provides a valuable insight into the importance of particular perceptual aspects when judging the quality of tone-mapped HDR content. The performance of the resulting features combination is thoroughly evaluated with respect to three publicly available databases and compared to several relevant state-of-the-art criteria. The proposed approach is shown to significantly outperform the tested metrics and can therefore be considered a competitive alternative for tone-mapped images evaluation.

LFDD: Light field image dataset for performance evaluation of objective quality metrics

  • Autoři: Zizien, A., Ing. Karel Fliegel, Ph.D.,
  • Publikace: Proceedings Volume 11510 - Applications of Digital Image Processing XLIII. Bellingham: SPIE, 2020. p. 115102U-1-115102U-13. SPIE PROCEEDINGS. vol. 11510. ISSN 0277-786X. ISBN 978-1-5106-3827-3.
  • Rok: 2020
  • DOI: 10.1117/12.2568490
  • Odkaz: https://doi.org/10.1117/12.2568490
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    An increase in research activity around plenoptic content can be seen in recent years. As the communities around the different modalities grow, so does the demand for publicly available annotated datasets of suitable content. The datasets can be used for a multitude of purposes, such as to design novel compression algorithms, subjective evaluation methodologies or objective quality metrics. In this work, a new publicly available annotated light field image dataset is presented. The dataset consists of scenes corrupted by state-of-the-art image and video compression algorithms (JPEG, JPEG 2000, BPG, VP9, AV1, AVC, HEVC), noise, and geometric distortion. For the subjective evaluation of the included scenes, a modified version of the Double Stimulus Impairment Scale (DSIS) methodology was adopted. The views of each scene were organized into a pseudo-sequence and played to the observers as animations. The resulting subjective scores, together with additional data, are included in the dataset. The data can be used to evaluate the performance of currently used visual quality metrics as well as for the design of new ones.

3D Visual Content Datasets

  • Autoři: Ing. Karel Fliegel, Ph.D., Battisti, F., Carli, M., Gelautz, M., Krasula, L., Le Callet, P., Zlokolica, V.
  • Publikace: 3D Visual Content Creation, Coding and Delivery. Cham: Springer International Publishing AG, 2019. p. 299-325. Signals and Communication Technology. ISSN 1860-4862. ISBN 978-3-319-77842-6.
  • Rok: 2019
  • DOI: 10.1007/978-3-319-77842-6_11
  • Odkaz: https://doi.org/10.1007/978-3-319-77842-6_11
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Development and performance evaluation of efficient methods for coding, transmission, and quality assessment of 3D visual content require rich datasets of a suitable test material. The use of these databases allows a fair comparison of systems under test. Moreover, publicly available and widely used datasets are crucial for experimentation leading to reproducible research. This chapter presents an overview of 3D visual content datasets relevant to research in the field of coding, transmission, and quality assessment. Description of regular stereoscopic or multiview image and video datasets is presented. Databases created using emerging technologies, including light-field imaging, are also addressed. Moreover, there are databases of multimedia content annotated with ratings from the subjective experiment, which are a necessary resource for understanding the complex problem of quality of experience while consuming the 3D visual content.

Evaluation resolution in live cell structured illumination microscopy

  • DOI: 10.1117/12.2527885
  • Odkaz: https://doi.org/10.1117/12.2527885
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In the last decade, several different structured illumination microscopy (SIM) approaches have been developed. Precise determination of the effective spatial resolution in a live cell SIM reconstructed image is essential for reliable interpretation of reconstruction results. Theoretical resolution improvement can be calculated for every SIM method. In practice, the final spatial resolution of the cell structures in the reconstructed image is limited by many different factors. Therefore, assessing the resolution directly from the single image is an inherent part of the live cell imaging. There are several commonly used resolution measurement techniques based on image analysis. These techniques include full-width at half maximum (FWHM) criterion, or Fourier ring correlation (FRC). FWHM measurement requires fluorescence beads or sharp edge/line in the observed image to determine the point spread function (PSF). FRC method requires two stochastically independent images of the same observed sample. Based on our experimental findings, the FRC method does not seem to be well suited for measuring the resolution of SIM live cell video sequences. Here we show a method based on the Fourier transform analysis using power spectral density (PSD). In order to estimate the cut-off frequency from a noisy signal, we use PSD estimation based on Welch’s method. This method is widely used in non-parametric power spectra analysis. Since the PSD-based metric can be computed from a single SIM image (one video frame), without any prior knowledge of the acquiring system, it can become a fundamental tool for imaging in live cell biology.

Imaging tissues and cells beyond the diffraction limit with structured illumination microscopy and Bayesian image reconstruction

  • Autoři: Pospíšil, J., Lukeš, T., Bendesky, J., Ing. Karel Fliegel, Ph.D., Spendier, K., Hagen, G.M.
  • Publikace: GigaScience. 2019, 8(1), 1-12. ISSN 2047-217X.
  • Rok: 2019
  • DOI: 10.1093/gigascience/giy126
  • Odkaz: https://doi.org/10.1093/gigascience/giy126
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Background Structured illumination microscopy (SIM) is a family of methods in optical fluorescence microscopy that can achieve both optical sectioning and super-resolution effects. SIM is a valuable method for high-resolution imaging of fixed cells or tissues labeled with conventional fluorophores, as well as for imaging the dynamics of live cells expressing fluorescent protein constructs. In SIM, one acquires a set of images with shifting illumination patterns. This set of images is subsequently treated with image analysis algorithms to produce an image with reduced out-of-focus light (optical sectioning) and/or with improved resolution (super-resolution). Findings Five complete, freely available SIM datasets are presented including raw and analyzed data. We report methods for image acquisition and analysis using open source software along with examples of the resulting images when processed with different methods. We processed the data using established optical sectioning SIM and super-resolution SIM methods, and with newer Bayesian restoration approaches which we are developing. Conclusion Various methods for SIM data acquisition and processing are actively being developed, but complete raw data from SIM experiments is not typically published. Publically available, high quality raw data with examples of processed results will aid researchers when developing new methods in SIM. Biologists will also find interest in the high-resolution images of animal tissues and cells we acquired. All of the data was processed with SIMToolbox, an open source and freely available software solution for SIM

Influence of artificially generated interocular blur difference on fusion stability under vergence stress

  • Autoři: Dostálek, M., Hejda, J., Ing. Karel Fliegel, Ph.D., Ducháčková, M., Dušek, L., Hozman, J., Lukeš, T., Autrata, R.
  • Publikace: Journal of Eye Movement Research. 2019, 12(4), ISSN 1995-8692.
  • Rok: 2019
  • DOI: 10.16910/jemr.12.4.4
  • Odkaz: https://doi.org/10.16910/jemr.12.4.4
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The stability of fusion was evaluated by its breakage when interocular blur differences were presented under vergence demand to healthy subjects. We presumed that these blur differences cause suppression of the more blurred image (interocular blur suppression, IOBS), disrupt binocular fusion and suppressed eye leaves its forced vergent position. During dichoptic presentation of static grayscale images of natural scenes, the luminance contrast (mode B) or higher-spatial frequency content (mode C) or luminance contrast plus higher-spatial frequency content (mode A) were stepwise reduced in the image presented to the non-dominant eye. We studied the effect of these types of blur on fusion stability at various levels of the vergence demand. During the divergence demand, the fusion was disrupted with approximately half blur than during convergence. Various modes of blur influenced fusion differently. The mode C (isolated reduction of higher-spatial frequency content) violated fusion under the lowest vergence demand significantly more than either isolated or combined reduction of luminance contrast (mode B and A). According to our results, the image´s details (i.e. higher-spatial frequency content) protects binocular fusion from disruption by the lowest vergence demand.

Methodology and tools for quality verification and measurement interpretation in a digital cinema environment

  • Autoři: Novák, M., Ing. Karel Fliegel, Ph.D.,
  • Publikace: Archiving 2019 Final Program and Proceedings. Society for Imaging Science and Technology, 2019. p. 31-38. ISSN 2168-3204. ISBN 978-0-89208-339-8.
  • Rok: 2019
  • DOI: 10.2352/issn.2168-3204.2019.1.0.8
  • Odkaz: https://doi.org/10.2352/issn.2168-3204.2019.1.0.8
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In this paper, we present a set of methodologies for Digital Cinema projector calibration, quality verification and evaluation by application of the international visual test SMPTE Digital Projection Verifier (DProve) as well as related SMPTE and ISO standards. We demonstrate modified SMPTE guidelines for faster, simpler and more precise measurements in practical conditions and introduce several tools for illustrative quality evaluation. The measurement interpretation is based on both, absolute tolerances defined by the SMPTE standards, as well as relative assessment calculated by the CIEDE2000 color difference formula. The latter approach is intended to better understand the importance of the color and tonality error for viewer’s perception in the specific cinema low light levels. On the examples of selected D-Cinema projector and display measurements, we introduce possible strengths and weaknesses of various projection technologies, used in Czech and Slovak commercial cinema or review rooms, which differs by the specific manufacturer’s technology or type of light source.

Stationarity testing in 2D image analysis

  • Autoři: Kukal, J., Nachtigalová, I., Krbcová, Z., doc. Ing. Jan Švihlík, Ph.D., Ing. Karel Fliegel, Ph.D.,
  • Publikace: Proceedings Volume 11137 - Applications of Digital Image Processing XLII. Bellingham: SPIE, 2019. SPIE PROCEEDINGS. vol. 11137. ISSN 0277-786X. ISBN 978-1-5106-2967-7.
  • Rok: 2019
  • DOI: 10.1117/12.2529346
  • Odkaz: https://doi.org/10.1117/12.2529346
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Signal and image stationarity is the basic assumption for many methods of their analysis. However this assumption is not true in a lot of real cases. The paper is focused on local stationary testing using a small symmetric neighbourhood. The neighbourhood is split into two parts which should have the same statistical properties when the hypothesis of image stationarity is valid. We apply various testing approaches (two-sampled F-test, t-test, WMW, K-S) to obtain adequate p-values for given pixel, mask position, and test type. Finally, using battery of masks and tests, we obtain the series of p-values for every pixel. Applying False Discovery Rate (FDR) methodology, we localize all the pixels when any hypothesis falls. Resulting binary image is an alternative to traditional edge detection but with strong statistical background.

Variational approach to semi-automated 2D image segmentation

  • Autoři: Kukal, J., Krbcová, Z., Nachtigalová, I., doc. Ing. Jan Švihlík, Ph.D., Ing. Karel Fliegel, Ph.D.,
  • Publikace: Proceedings Volume 11137 - Applications of Digital Image Processing XLII. Bellingham: SPIE, 2019. SPIE PROCEEDINGS. vol. 11137. ISSN 0277-786X. ISBN 978-1-5106-2967-7.
  • Rok: 2019
  • DOI: 10.1117/12.2529374
  • Odkaz: https://doi.org/10.1117/12.2529374
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The segmentation of 2D biomedical images is very complex problem which has to be solved interactively. Original MRI, CT, PET, or SPECT image can be enhanced using variational smoother. However, there are Regions of Interest (ROI) which can be exactly localized. The question is how to design human interaction with computer for user friendly biomedical service. Our approach is based on user selected points which determine the ROI border line. The relationship between point positions and image intensity is subject of variational interpolation using thin plate spline model. The general principle of segmentation is demonstrated on biomedical images of human brain.

Comparison of resolution estimation methods in optical microscopy

  • DOI: 10.1117/12.2321301
  • Odkaz: https://doi.org/10.1117/12.2321301
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Super-resolution (SR) microscopy is a powerful technique which enhances the resolution of optical microscopes beyond the diffraction limit. Recent SR methods achieve the resolution of 100 nm. Theoretical resolution enhancement can be mathematically defined. However, the final resolution in the real image can be influenced by technical limitations. Evaluation of resolution in a real sample is essential to assess the performance of an SR technique. Several image based resolution limit evaluation methods exist, but the determination of cutoff frequency is still a challenging task. In order to compare the efficiency of assessing resolution methods, the reference estimation technique is necessary. There exist several conventional methods in digital image processing. In this paper, the most common resolution measurement techniques used in the optical microscopy imaging are presented and their performance compared.

Interpolation methods for the improvement of the point spread function estimation

  • DOI: 10.1109/RADIOELEK.2018.8376375
  • Odkaz: https://doi.org/10.1109/RADIOELEK.2018.8376375
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Interpolation methods face the issue of the specific content of the images. This paper is devoted to a comparison of interpolation methods suitable for small image content and its influence on improvement in the PSF estimation. The issue is that when the PSF is represented by only several pixels, the model of the system is not correctly optimized. Selection of the suitable interpolation method represents the main aim with consequences to the PSF model estimation.

Overview of the JPEG XS core coding system subjective evaluations

  • Autoři: Willème, A., Mahmoudpour, S., Viola, I., Ing. Karel Fliegel, Ph.D., Pospíšil, J., Ebrahimi, T., Schelkens, P., Descampe, A., Macq, B.
  • Publikace: Proceedings Volume 10752 - Applications of Digital Image Processing XLI. Bellingham: SPIE, 2018. SPIE PROCEEDINGS. vol. 10752. ISSN 0277-786X. ISBN 9781510620759.
  • Rok: 2018
  • DOI: 10.1117/12.2323435
  • Odkaz: https://doi.org/10.1117/12.2323435
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The JPEG committee (Joint Photographic Experts Group, formally known as ISO/IEC SC29 WG1) is currently in the process of standardizing JPEG XS, a new interoperable solution for low-latency, lightweight and visually lossless compression of image and video. This codec is intended to be used in applications where content would usually be transmitted or stored in uncompressed form such as in live production, display links, virtual and augmented reality, self driving vehicles or frame buffers. It achieves bandwidth and power reduction for transparent and low latency coding for compression ratios ranging from 2:1 to 6:1. The subjective assessment of the impact of visually lossless compression poses particular challenges. This paper describes the subjective quality evaluation conducted on the JPEG XS core coding system. In particular, it details the test procedures and compares the results obtained by the different evaluation laboratories involved in the standardization effort.

Performance comparison of perceived image color difference measures

  • DOI: 10.1117/12.2321644
  • Odkaz: https://doi.org/10.1117/12.2321644
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper deals with techniques for analysis of perceived color differences in images. Impact of color artifacts in image processing chain is a critical factor in the assessment of overall Quality of Experience (QoE). At first, an overview of color difference measures is presented. The performance of the methods is compared based on the results from subjective studies. Possible utilization of publicly available datasets with associated subjective scores is discussed. Majority of the datasets contain images distorted by various types of distortions not necessarily with controlled color impairments. Dedicated database of images with common color distortions and associated subjective scores is introduced. Performance evaluation and comparison of objective image color difference measures is presented using conventional correlation performance measures and robust receiver operating characteristic (ROC) based analyses.

Quantitative super-resolution single molecule microscopy dataset of YFP-tagged growth factor receptors

  • Autoři: Lukeš, T., Pospíšil, J., Ing. Karel Fliegel, Ph.D., Lasser, T., Hagen, G.M.
  • Publikace: GigaScience. 2018, 7(3), ISSN 2047-217X.
  • Rok: 2018
  • DOI: 10.1093/gigascience/giy002
  • Odkaz: https://doi.org/10.1093/gigascience/giy002
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Background: Super-resolution single molecule localization microscopy (SMLM) is a method for achieving resolution beyond the classical limit in optical microscopes (approx. 200 nm laterally). Yellow fluorescent protein (YFP) has been used for super-resolution single molecule localization microscopy, but less frequently than other fluorescent probes. Working with YFP in SMLM is a challenge because a lower number of photons are emitted per molecule compared to organic dyes which are more commonly used. Publically available experimental data can facilitate development of new data analysis algorithms. Findings: Four complete, freely available single molecule super-resolution microscopy datasets on YFP-tagged growth factor receptors expressed in a human cell line are presented including both raw and analyzed data. We report methods for sample preparation, for data acquisition, and for data analysis, as well as examples of the acquired images. We also analyzed the SMLM data sets using a different method: super-resolution optical fluctuation imaging (SOFI). The two modes of analysis offer complementary information about the sample. A fifth single molecule super-resolution microscopy dataset acquired with the dye Alexa 532 is included for comparison purposes. Conclusion: This dataset has potential for extensive reuse. Complete raw data from SMLM experiments has typically not been published. The YFP data exhibits low signal to noise ratios, making data analysis a challenge. These data sets will be useful to investigators developing their own algorithms for SMLM, SOFI, and related methods. The data will also be useful for researchers investigating growth factor receptors such as ErbB3.

Stabilization of median smoother via variational approach

  • Autoři: Krbcová, Z., Sireis, A., Kukal, J., doc. Ing. Jan Švihlík, Ph.D., Ing. Karel Fliegel, Ph.D.,
  • Publikace: Proceedings Volume 10752 - Applications of Digital Image Processing XLI. Bellingham: SPIE, 2018. SPIE PROCEEDINGS. vol. 10752. ISSN 0277-786X. ISBN 9781510620759.
  • Rok: 2018
  • DOI: 10.1117/12.2321226
  • Odkaz: https://doi.org/10.1117/12.2321226
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Traditional median smoother for 2D images is insensitive to impulse noise but generates flat areas as unwanted artifacts. The proposed approach to overcome this issue is based on the minimization of the regularized form of total variation functional. At first the continuous functional is defined for n-dimensional signal in an integral form with regularization term. The continuous functional is converted to the discrete form using equidistant spatial sampling in point grid of pixels, voxels or other elements. This approach is suitable for traditional signal and image processing. The total variance is then converted to the sum of absolute intensity differences as a minimization criterion. The functional convexity guarantees the existence of global minimum and absence of local extremes. Resulting non-linear filter iteratively calculates local medians using red-black method of Successive Over/Under Relaxation (SOR) scheme. The optimal value of the relaxation parameter is also subject to our study. The sensitivity to regularization parameter enables to design high-pass and nonlinear band-pass filters as the difference between the image and low-pass smoother or as the difference between two different low-pass smoothers, respectively. Various median based approaches are compared in the paper.

Stochastic and analytic modeling of atmospheric turbulence in image processing

  • Autoři: Krbcová, Z., Kukal, J., Tran, Q., doc. Ing. Jan Švihlík, Ph.D., Ing. Karel Fliegel, Ph.D.,
  • Publikace: Proceedings Volume 10752 - Applications of Digital Image Processing XLI. Bellingham: SPIE, 2018. SPIE PROCEEDINGS. vol. 10752. ISSN 0277-786X. ISBN 9781510620759.
  • Rok: 2018
  • DOI: 10.1117/12.2321199
  • Odkaz: https://doi.org/10.1117/12.2321199
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Modeling of atmospheric turbulence through Kolmogorov theorem belongs to traditional applications of 2D Fourier Transform (2D FT). It is based on Point Spread Function (PSF) in the spatial domain and its frequency domain image known as Optical Transfer Function (OTF). The latter is available in the explicit form. It enables to create an artificial fog effect in traditional image processing using 2D Discrete Fourier Transform (2D DFT). Exact knowledge of the Optical Transfer Function allows performing the image deblurring as deconvolution through Wiener method. The difference between the reference image and the deconvolution outcome can be quantified using SNR in traditional and rank modification. However, the real star image is a result of a stochastic process which is driven by 2D alpha-stable distribution. There is an efficient method how to generate a pseudorandom sample from the alpha-stable distribution. The distribution then enables to simulate the photon distribution following the theoretical PSF, i.e. convergence according to distribution is guaranteed. The comparison of both models and optimal parameter setting of Wiener deconvolution are studied for various exposure times and CCD camera noise levels. Obtained results can be generalized and applied to turbulent noise suppression.

Analysis of image reconstruction artifacts in structured illumination microscopy

  • DOI: 10.1117/12.2274418
  • Odkaz: https://doi.org/10.1117/12.2274418
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Structured Illumination Microscopy (SIM) is a super-resolution technique which enables to enhance the resolution of optical microscopes beyond the diraction limit. The nal super-resolution image quality strongly depends on the performance of SIM image reconstruction. Standard SIM methods require precise knowledge of the illumination pattern and assume the sample to be stationary during the acquisition of illumination patterned images. In the case of imaging live cells, the movements of the cell result in the occurrence of image reconstruction artifacts. To reduce this kind of artifacts the short acquisition time is needed. However, short exposure time causes low signal-to-noise ratio (SNR). Moreover, a drift of the specimen may distort the illumination pattern properties in each image. This issue together with the low SNR makes the estimation of reconstruction parameters a challenging task. Inaccurate assessment of spatial frequency, phase shift or orientation of the illumination pattern leads to incorrect separation and shift of spectral components in Fourier space. This results in unwanted image reconstruction artifacts and hampers the resolution enhancement in practice. In this paper, we analyze possible artifacts in super-resolution images reconstructed using super-resolution SIM technique (SR-SIM). An overview of typical image reconstruction artifact types is presented. Distinguishing image artifacts from newly resolved sample features is essential for future SIM applications in cell biology.

Assessing resolution in live cell structured illumination microscopy

  • DOI: 10.1117/12.2292793
  • Odkaz: https://doi.org/10.1117/12.2292793
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Structured Illumination Microscopy (SIM) is a powerful super-resolution technique, which is able to enhance the resolution of optical microscope beyond the Abbe diffraction limit. In the last decade, numerous SIM methods that achieve the resolution of 100 nm in the lateral dimension have been developed. The SIM setups with new high-speed cameras and illumination pattern generators allow rapid acquisition of the live specimen. Therefore, SIM is widely used for investigation of the live structures in molecular and live cell biology. Quantitative evaluation of resolution enhancement in a real sample is essential to describe the efficiency of super-resolution microscopy technique. However, measuring the resolution of a live cell sample is a challenging task. Based on our experimental findings, the widely used Fourier ring correlation (FRC) method does not seem to be well suited for measuring the resolution of SIM live cell video sequences. Therefore, the resolution assessing methods based on Fourier spectrum analysis are often used. We introduce a measure based on circular average power spectral density (PSDca) estimated from a single SIM image (one video frame). PSDca describes the distribution of the power of a signal with respect to its spatial frequency. Spatial resolution corresponds to the cut-off frequency in Fourier space. In order to estimate the cut-off frequency from a noisy signal, we use a spectral subtraction method for noise suppression. In the future, this resolution assessment approach might prove useful also for single-molecule localization microscopy (SMLM) live cell imaging.

Estimation of Poisson noise in spatial domain

  • DOI: 10.1117/12.2274149
  • Odkaz: https://doi.org/10.1117/12.2274149
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper deals with modeling of astronomical images in the spatial domain. We consider astronomical light images contaminated by the dark current which is modeled by Poisson random process. Dark frame image maps the thermally generated charge of the CCD sensor. In this paper, we solve the problem of an addition of two Poisson random variables. At first, the noise analysis of images obtained from the astronomical camera is performed. It allows estimating parameters of the Poisson probability mass functions in every pixel of the acquired dark frame. Then the resulting distributions of the light image can be found. If the distributions of the light image pixels are identified, then the denoising algorithm can be applied. The performance of the Bayesian approach in the spatial domain is compared with the direct approach based on the method of moments and the dark frame subtraction.

Phase estimation of illumination pattern in structured illumination microscopy

  • DOI: 10.1109/RADIOELEK.2017.7937590
  • Odkaz: https://doi.org/10.1109/RADIOELEK.2017.7937590
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Conventional structured illumination microscopy (SIM) methods require precise knowledge of the illumination pattern and assume the sample to be stationary during the acquisition. Fulfilling these two conditions in practice is difficult. Therefore, the estimation of illumination pattern from acquired images is necessary. Inaccurate estimation of spatial frequency, angular orientation or phase shift of the illumination pattern leads to unwanted image reconstruction artifacts. In this paper, we analyze the performance of different phase estimation approaches using simulated SIM data from a synthetic sample.

Preference of Experience in Image Tone-Mapping: Dataset and Framework for Objective Measures Comparison

  • Autoři: Krasula, L., Narwaria, M., Ing. Karel Fliegel, Ph.D., Le Callet, P.
  • Publikace: IEEE Journal of Selected Topics in Signal Processing. 2017, 11(1), 64-74. ISSN 1932-4553.
  • Rok: 2017
  • DOI: 10.1109/JSTSP.2016.2637168
  • Odkaz: https://doi.org/10.1109/JSTSP.2016.2637168
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The popularity of high dynamic range (HDR) imaging has grown in both academic and private research sectors. Since the native visualization of HDR content still has its limitations, the importance of dynamic range compression (i.e., tone-mapping) is very high. This paper evaluates observers' preference of experience in context of image tone-mapping. Given the different nature of natural and computer-generated content, the way observers perceive the quality of tone-mapped images can be fundamentally different. In this paper, we describe a subjective experiment attempting to determine users' preference with respect to these two types of content in two different viewing scenarios-with and without the HDR reference. The results show that the absence of the reference can significantly influence the subjects' preferences for the natural images, while no significant impact has been found in the case of the synthetic images. Moreover, we introduce a benchmarking framework and compare the performance of selected objective metrics. The resulting dataset and framework are made publicly available to provide a common test bed and methodology for evaluating metrics in the considered scenario.

Quality Assessment of Sharpened Images: Challenges, Methodology, and Objective Metrics

  • DOI: 10.1109/TIP.2017.2651374
  • Odkaz: https://doi.org/10.1109/TIP.2017.2651374
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Most of the effort in image quality assessment (QA) has been so far dedicated to the degradation of the image. However, there are also many algorithms in the image processing chain that can enhance the quality of an input image. These include procedures for contrast enhancement, deblurring, sharpening, up-sampling, denoising, transfer function compensation, and so on. In this paper, possible strategies for the QA of sharpened images are investigated. This task is not trivial, because the sharpening techniques can increase the perceived quality, as well as introduce artifacts leading to the quality drop (over-sharpening). Here, the framework specifically adapted for the QA of sharpened images and objective metrics comparison in this context is introduced. However, the framework can be adopted in other QA areas as well. The problem of selecting the correct procedure for subjective evaluation was addressed and a subjective test on blurred, sharpened, and over-sharpened images was performed in order to demonstrate the use of the framework. The obtained ground-truth data were used for testing the suitability of the state-of-the-art objective quality metrics for the assessment of sharpened images. The comparison was performed by novel procedure using rank order correlation analyses, which is found more appropriate for the task than standard methods. Furthermore, seven possible augmentations of the no-reference S3 metric adapted for sharpened images are proposed. The performance of the metric is significantly improved and also superior over the rest of the tested quality criteria with respect to the subjective data.

Resolution analysis of archive films for the purpose of their optimal digitization and distribution

  • DOI: 10.1117/12.2274095
  • Odkaz: https://doi.org/10.1117/12.2274095
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    With recent high demand for ultra-high-definition (UHD) content to be screened in high-end digital movie theaters but also in the home environment, film archives full of movies in high-definition and above are in the scope of UHD content providers. Movies captured with the traditional film technology represent a virtually unlimited source of UHD content. The goal to maintain complete image information is also related to the choice of scanning resolution and spatial resolution for further distribution. It might seem that scanning the film material in the highest possible resolution using state-of-the-art film scanners and also its distribution in this resolution is the right choice. The information content of the digitized images is however limited, and various degradations moreover lead to its further reduction. Digital distribution of the content in the highest image resolution might be therefore unnecessary or uneconomical. In other cases, the highest possible resolution is inevitable if we want to preserve fine scene details or film grain structure for archiving purposes. This paper deals with the image detail content analysis of archive film records. The resolution limit in captured scene image and factors which lower the final resolution are discussed. Methods are proposed to determine the spatial details of the film picture based on the analysis of its digitized image data. These procedures allow determining recommendations for optimal distribution of digitized video content intended for various display devices with lower resolutions. Obtained results are illustrated on spatial downsampling use case scenario, and performance evaluation of the proposed techniques is presented.

Set of Methodologies for Archive Film Digitization and Restoration with Examples of Their Application in ORWO Region

  • DOI: 10.2352/issn.2168-3204.2017.1.0.62
  • Odkaz: https://doi.org/10.2352/issn.2168-3204.2017.1.0.62
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In this paper; we present a set of verified methodologies suitable for application to a particular problem of archive films' restoration and digitization, especially when a nonstandard laboratory or creative techniques were used, which is typical for so-called ORWO region. The umbrella of the presented techniques is formed by established Digitally Restored Authorizate (DRA) methodology, with its aim to achieve the appearance of the audio and visual components of the digitized film as close as possible to the original author's concept. Among the methodologies, we present tools for objective assessment of perceived differences in the outcomes of the color grading process. These techniques are suitable for evaluation of appearance match among various available versions of the digitized film in respect to the DRA outcome.

Smoothing of astronomical images with Poisson distribution

  • Autoři: Krbcová, Z., Kukal, J., Švihlík, J., Ing. Karel Fliegel, Ph.D.,
  • Publikace: Applications of Digital Image Processing XL. Bellingham: SPIE, 2017. p. 103962V-1-103962V-6. Proceedings of SPIE. ISSN 0277-786X. ISBN 978-1-5106-1249-5.
  • Rok: 2017
  • DOI: 10.1117/12.2274121
  • Odkaz: https://doi.org/10.1117/12.2274121
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Images obtained from an astronomical digital camera are of integer nature as event counters in every pixel of its image sensor. The quality of the captured images is in uenced mostly by the camera characteristics and photon noise caused by natural random uctuation of observed light. We suppose the image pixel intensity as a mean value of the signal with Poisson distribution. The application of maximum likelihood method with image gradient regularization leads to variational task in discrete formulation. This variational task has only one unique solution on which the novel numerical method of image smoothing is based. The performance of the proposed smoothing procedure is tested using real images obtained from the digital camera in Meteor Automatic Imager and Analyzer (MAIA).

Application of field dependent polynomial model

  • DOI: 10.1117/12.2237310
  • Odkaz: https://doi.org/10.1117/12.2237310
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Extremely wide-field imaging systems have many advantages regarding large display scenes whether for use in microscopy, all sky cameras, or in security technologies. The Large viewing angle is paid by the amount of aberrations, which are included with these imaging systems. Modeling wavefront aberrations using the Zernike polynomials is known a longer time and is widely used. Our method does not model system aberrations in a way of modeling wavefront, but directly modeling of aberration Point Spread Function of used imaging system. This is a very complicated task, and with conventional methods, it was difficult to achieve the desired accuracy. Our optimization techniques of searching coefficients space-variant Zernike polynomials can be described as a comprehensive model for ultra-wide-field imaging systems. The advantage of this model is that the model describes the whole space-variant system, unlike the majority models which are partly invariant systems. The issue that this model is the attempt to equalize the size of the modeled Point Spread Function, which is comparable to the pixel size. Issues associated with sampling, pixel size, pixel sensitivity profile must be taken into account in the design. The model was verified in a series of laboratory test patterns, test images of laboratory light sources and consequently on real images obtained by an extremely wide-field imaging system WILLIAM. Results of modeling of this system are listed in this article.

Evaluation of color grading impact in restoration process of archive films

  • DOI: 10.1117/12.2237558
  • Odkaz: https://doi.org/10.1117/12.2237558
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Color grading of archive films is a very particular task in the process of their restoration. The ultimate goal of color grading here is to achieve the same look of the movie as intended at the time of its first presentation. The role of the expert restorer, expert group and a digital colorist in this complicated process is to find the optimal settings of the digital color grading system so that the resulting image look is as close as possible to the estimate of the original reference release print adjusted by the expert group of cinematographers. A methodology for subjective assessment of perceived differences between the outcomes of color grading is introduced, and results of a subjective study are presented. Techniques for objective assessment of perceived differences are discussed, and their performance is evaluated using ground truth obtained from the subjective experiment. In particular, a solution based on calibrated digital single-lens reflex camera and subsequent analysis of image features captured from the projection screen is described. The system based on our previous work is further developed so that it can be used for the analysis of projected images. It allows assessing color differences in these images and predict their impact on the perceived difference in image look.

Fast Estimate of Hartley Entropy in Image Sharpening

  • DOI: 10.1117/12.2237743
  • Odkaz: https://doi.org/10.1117/12.2237743
  • Pracoviště: Katedra radioelektroniky, Algoritmy pro biomedicínské zobrazování
  • Anotace:
    Two classes of linear IIR filters: Laplacian of Gaussian (LoG) and Difference of Gaussians (DoG) are frequently used as high pass filters for contextual vision and edge detection. They are also used for image sharpening when linearly combined with the original image. Resulting sharpening filters are radially symmetric in spatial and frequency domains. Our approach is based on the radial approximation of unknown optimal filter, which is designed as a weighted sum of Gaussian filters with various radii. The novel filter is designed for MRI image enhancement where the image intensity represents anatomical structure plus additive noise. We prefer the gradient norm of Hartley entropy of whole image intensity as a measure which has to be maximized for the best sharpening. The entropy estimation procedure is as fast as FFT included in the filter but this estimate is a continuous function of enhanced image intensities. Physically motivated heuristic is used for optimum sharpening filter design by its parameter tuning. Our approach is compared with Wiener filter on MRI images.

Long-Term Continuous Double Station Observation of Faint Meteor Showers

  • DOI: 10.3390/s16091493
  • Odkaz: https://doi.org/10.3390/s16091493
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Meteor detection and analysis is an essential topic in the field of astronomy. In this paper, a high-sensitivity and high-time-resolution imaging device for the detection of faint meteoric events is presented. The instrument is based on a fast CCD camera and an image intensifier. Two such instruments form a double-station observation network. The MAIA (Meteor Automatic Imager and Analyzer) system has been in continuous operation since 2013 and has successfully captured hundreds of meteors belonging to different meteor showers, as well as sporadic meteors. A data processing pipeline for the efficient processing and evaluation of the massive amount of video sequences is also introduced in this paper.

Meteor tracking via local pattern clustering in spatio-temporal domain

  • DOI: 10.1117/12.2237649
  • Odkaz: https://doi.org/10.1117/12.2237649
  • Pracoviště: Katedra radioelektroniky, Algoritmy pro biomedicínské zobrazování
  • Anotace:
    Reliable meteor detection is one of the crucial disciplines in astronomy. A variety of imaging systems is used for meteor path reconstruction. The traditional approach is based on analysis of 2D image sequences obtained from a double station video observation system. Precise localization of meteor path is difficult due to atmospheric turbulence and other factors causing spatio-temporal fluctuations of the image background. The proposed technique performs non-linear preprocessing of image intensity using Box-Cox transform as recommended in our previous work. Both symmetric and asymmetric spatio-temporal differences are designed to be robust in the statistical sense. Resulting local patterns are processed by data whitening technique and obtained vectors are classified via cluster analysis and Self-Organized Map (SOM).

On the accuracy of objective image and video quality models: New methodology for performance evaluation

  • DOI: 10.1109/QoMEX.2016.7498936
  • Odkaz: https://doi.org/10.1109/QoMEX.2016.7498936
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    There are several standard methods for evaluating the performance of models for objective quality assessment with respect to results of subjective tests. However, all of them suffer from one or more of the following drawbacks: They do not consider the uncertainty in the subjective scores, requiring the models to make certain decision where the correct behavior is not known. They are vulnerable to the quality range of the stimuli in the experiments. In order to compare the models, they require a mapping of predicted values to the subjective scores, thus not comparing the models exactly as they are used in the real scenarios. In this paper, new methodology for objective models performance evaluation is proposed. The method is based on determining the classification abilities of the models considering two scenarios inspired by the real applications. It does not suffer from the previously stated drawbacks and enables to easily evaluate the performance on the data from multiple subjective experiments. Moreover, techniques to determine statistical significance of the performance differences are suggested. The proposed framework is tested on several selected metrics and datasets, showing the ability to provide a complementary information about the models' behavior while being in parallel with other state-of-the-art methods.

SIMToolbox: a MATLAB toolbox for structured illumination fluorescence microscopy

  • Autoři: Křížek, P., Lukeš, T., Ovesný, M., Ing. Karel Fliegel, Ph.D., Hagen, G. M.
  • Publikace: Bioinformatics. 2016, 32(2), 318-320. ISSN 1367-4803.
  • Rok: 2016
  • DOI: 10.1093/bioinformatics/btv576
  • Odkaz: https://doi.org/10.1093/bioinformatics/btv576
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    SIMToolbox is an open-source, modular set of functions for MATLAB equipped with a user-friendly graphical interface and designed for processing two-dimensional and three-dimensional data acquired by structured illumination microscopy (SIM). Both optical sectioning and super-resolution applications are supported. The software is also capable of maximum a posteriori probability image estimation (MAP-SIM), an alternative method for reconstruction of structured illumination images. MAP-SIM can potentially reduce reconstruction artifacts, which commonly occur due to refractive index mismatch within the sample and to imperfections in the illumination.

Simultaneous analogue and digital observations and comparison of results

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Double station observations using analogue video cameras are carried out at the Ondřejov observatory since 1998. Recently new digital cameras MAIA were developed and introduced. Both systems are based on the same type of image intensifier. To evaluate the enhanced properties of the new cameras several simultaneous campaigns with both systems were accomplished.

Živý film: Digitalizace filmu Metodou DRA

  • Autoři: Černíček, J., Ing. Karel Fliegel, Ph.D., Folvarčný, J., Frouz, M., Fuxjager, K., Gloc, J., Hendrich, V., Hubička, J., Hyťha, L., Jakubisko, J., Mathé, I., Menzel, J., Michalovič, P., Myslík, P., Novák, M., Novotný, J., prof. Mgr. Petr Páta, Ph.D., Pecák, J., Piškula, M., Rejholec, P., Savický, N., Souček, D., Stuchlík, Z., Šimunek, J., Štoll, M., doc. Ing. Stanislav Vítek, Ph.D., Weigl, P., Weiser, A., Winston, B., Zuska, V.
  • Publikace: Praha: Lepton studio, 2016. ISBN 978-80-904503-4-9.
  • Rok: 2016
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Stejně jak jiná umělecká díla, i díla filmového umění časem stárnou a postupně degradují. V současné době navíc dochází k masové digitalizaci projekčních prostor a tak ještě více nabývá na důležitosti otázka vzniku digitálně restaurované podoby filmového díla, která může divákovi nabídnout autentický vjem díla během jeho premiérové projekce. Kolektivní monografie, která shrnuje zkušenosti z dosavadních digitalizací národního filmového fondu a výsledky pětiletého výzkumného projektu, hledajícího metodiku jeho digitalizace v rámci programu NAKI, seznamuje v širších souvislostech s Metodou digitálně restaurovaného autorizátu (DRA), s otázkami a úskalími, které převod filmu do digitální podoby přináší a shrnuje pohled a zkušenosti svých autorů na vývoj digitalizace filmu v ČR v posledním desetiletí. Kniha také řeší otázky zachování autorské, obrazové i zvukové autenticity díla během digitalizace a následné projekce a distribuce filmového díla. Vedle statí jednotlivých expertů a tvůrců (zejména filmoví kameramané a režiséři – profesoři FAMU) knihu doplňují rozhovory s našimi i zahraničními archiváři a filmaři (Vladimír Opěla, Jurij Norštejn, Willy Kurant, Ivo Špalj, James Mockski), zásadní dokumenty (deklarace, kodexy, výzvy, prohlášení, memoranda a korespondence), seznam odborné literatury a obsáhlé anglické resumé. Kniha obsahuje na 190 fotografií, filmových záběrů a grafů.

GPU accelerated processing of astronomical high frame-rate videosequences

  • DOI: 10.1117/12.2188610
  • Odkaz: https://doi.org/10.1117/12.2188610
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Astronomical instruments located around the world are producing an incredibly large amount of possibly interesting scientific data. Astronomical research is expanding into large and highly sensitive telescopes. Total volume of data rates per night of operations also increases with the quality and resolution of state-of-the-art CCD/CMOS detectors. Since many of the ground-based astronomical experiments are placed in remote locations with limited access to the Internet, it is necessary to solve the problem of the data storage. It mostly means that current data acquistion, processing and analyses algorithm require review. Decision about importance of the data has to be taken in very short time. This work deals with GPU accelerated processing of high frame-rate astronomical video-sequences, mostly originating from experiment MAIA (Meteor Automatic Imager and Analyser), an instrument primarily focused to observing of faint meteoric events with a high time resolution. The instrument with price bellow 2000 euro consists of image intensifier and gigabite ethernet camera running at 61 fps. With resolution better than VGA the system produces up to 2TB of scientifically valuable video data per night. Main goal of the paper is not to optimize any GPU algorithm, but to propose and evaluate parallel GPU algorithms able to process huge amount of video-sequences in order to delete all uninteresting data.

Influence of HDR reference on observers preference in tone-mapped images evaluation

  • Autoři: Krasula, L., Narwaria, M., Ing. Karel Fliegel, Ph.D., Le Callet, P.
  • Publikace: 2015 Seventh International Workshop on Quality of Multimedia Experience (QoMEX). New Jersey: IEEE Signal Processing Society, 2015. pp. 1-6. ISBN 978-1-4799-8958-4.
  • Rok: 2015
  • DOI: 10.1109/QoMEX.2015.7148103
  • Odkaz: https://doi.org/10.1109/QoMEX.2015.7148103
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The most reliable way to assess the quality of images after a dynamic range compression (i.e. tone-mapping) is a subjective study. The goal of this paper is to determine, whether the preference of the participating subjects is significantly affected by the presence of the original high dynamic range (HDR) image displayed on the HDR screen or if we can obtain equivalent results from the test without the reference. For that, an extensive experiment using two different setups has been performed. The statistical analysis showed significant difference between evaluations and a Monte Carlo simulation proved that the absence of the reference is the factor of influence.

Meteor localization via statistical analysis of spatially temporal fluctuations in image sequences

  • DOI: 10.1117/12.2188186
  • Odkaz: https://doi.org/10.1117/12.2188186
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Meteor detection is one of the most important procedures in astronomical imaging. Meteor path in Earth's atmosphere is traditionally reconstructed from double station video observation system generating 2D image sequences. However, the atmospheric turbulence and other factors cause spatially-temporal fluctuations of image background, which makes the localization of meteor path more difficult. Our approach is based on nonlinear preprocessing of image intensity using Box-Cox and logarithmic transform as its particular case. The transformed image sequences are then differentiated along discrete coordinates to obtain statistical description of sky background fluctuations, which can be modeled by multivariate normal distribution. After verification and hypothesis testing, we use the statistical model for outlier detection. Meanwhile the isolated outlier points are ignored, the compact cluster of outliers indicates the presence of meteoroids after ignition.

Performance evaluation of image deconvolution techniques in space-variant astronomical imaging systems with nonlinearities

  • DOI: 10.1117/12.2187888
  • Odkaz: https://doi.org/10.1117/12.2187888
  • Pracoviště: Katedra kybernetiky, Katedra radioelektroniky
  • Anotace:
    There are various deconvolution methods for suppression of blur in images. In this paper a survey of image deconvolution techniques is presented with focus on methods designed to handle images acquired with wide-field astronomical imaging systems. Image blur present in such images is space-variant especially due to space-variant point spread function (PSF) of the lens. The imaging system can contain also nonlinear electro-optical elements. Analysis of nonlinear and space-variant imaging systems is usually simplified so that the system is considered as linear and space-invariant (LSI) under specific constraints. Performance analysis of selected image deconvolution methods is presented in this paper, while considering space-variant nature of wide-field astronomical imaging system. Impact of nonlinearity on the overall performance of image deconvolution technique is also analyzed. Test images with characteristics obtained from the real system with space-variant wide-field input lens and nonlinear image intensifier are used for the performance analysis.

Rendering of HDR content on LDR displays: an objective approach

  • Autoři: Krasula, L., Narwaria, M., Ing. Karel Fliegel, Ph.D., Le Callet, P.
  • Publikace: Applications of Digital Image Processing XXXVIII. Bellingham: SPIE, 2015. p. 95990X-1-95990X-9. Proceedings of SPIE. ISSN 0277-786X. ISBN 978-1-62841-765-4.
  • Rok: 2015
  • DOI: 10.1117/12.2186388
  • Odkaz: https://doi.org/10.1117/12.2186388
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Dynamic range compression (or tone mapping) of HDR content is an essential step towards rendering it on traditional LDR displays in a meaningful way. This is however non-trivial and one of the reasons is that tone mapping operators (TMOs) usually need content-specific parameters to achieve the said goal. While subjective TMO parameter adjustment is the most accurate, it may not be easily deployable in many practical applications. Its subjective nature can also influence the comparison of different operators. Thus, there is a need for objective TMO parameter selection to automate the rendering process. To that end, we investigate into a new objective method for TMO parameters optimization. Our method is based on quantification of contrast reversal and naturalness. As an important advantage, it does not require any prior knowledge about the input HDR image and works independently on the used TMO. Experimental results using a variety of HDR images and several popular TMOs demonstrate the value of our method in comparison to default TMO parameter settings.

Současný vývoj obrazových kompresních metod

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: XXV. konference Radiokomunikace - Sborník přednášek. Pardubice: UNIT, 2015. pp. 63-72. ISBN 978-80-905345-6-8.
  • Rok: 2015
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Dvě nejvýznamnější standardizační skupiny zabývající se vývojem obrazových kompresních metod jsou JPEG (Joint Photographic Experts Group) a MPEG (Moving Picture Experts Group). JPEG je společná skupina ISO/IEC JTC1 (Joint Technical Committee 1, Subcommittee 29, Working Group 1 – JTC 1/SC 29/WG 1) a ITU-T (ITU-T Study Group 16), která byla u zrodu standardů pro kódování statických obrazů, zejména pak JPEG, JPEG 2000 a JPEG XR. MPEG je pracovní skupina ISO/IEC JTC1 (Joint Technical Committee 1, Subcommittee 29, Working Group 1 – JTC 1/SC 29/WG 11), která byla založena organizacemi ISO a IEC s cílem vývoje standardů pro kódování audiovizuálních signálů a jejich přenos. V tomto příspěvku se zaměříme na stručný popis vlastností v současnosti nejrozšířenějších standardů a předpokládaný krátkodobý vývoj v této oblasti.

2D Iterative MAP Detection: Principles and Applications in Image Restoration

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper provides a theoretical framework for the two-dimensional iterative maximum a posteriori detection. This generalization is based on the concept of detection algorithms BCJR and SOVA, i.e., the classical (one-dimensional) iterative detectors used in telecommunication applications. We generalize the one-dimensional detection problem considering the spatial ISI kernel as a two-dimensional finite state machine (2D FSM) representing a network of the spatially concatenated elements. The cellular structure topology defines the design of the 2D Iterative decoding network, where each cell is a general combination-marginalization statistical element (SISO module) exchanging discrete probability density functions (information metrics) with neighboring cells. In this paper, we statistically analyse the performance of various topologies with respect to their application in the field of image restoration. The iterative detection algorithm was applied on the task of binarization of images taken from a CCD camera. The reconstruction includes suppression of the defocus caused by the lens, CCD sensor noise suppression and interpolation (demosaicing). The simulations prove that the algorithm provides satisfactory results even in the case of an input image that is under-sampled due to the Bayer mask.

Binarization of noisy microscopy images through signal reconstruction using iterative detection network

  • DOI: 10.1109/ICIP.2014.7025802
  • Odkaz: https://doi.org/10.1109/ICIP.2014.7025802
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    We propose a novel binarization method based on a signal reconstruction using an iterative detection network. The algorithm simulates the whole image acquisition process taking into account a point spread function of the imaging system and its noise characteristics. The negative influence of image blur and noise is effectively suppressed by iterative detection network based on the criterion of maximum a posteriori probability. The proposed method was successfully applied to noisy microscopy images. Experiments show that the proposed method due to the noise suppression and deconvolution properties provides for noisy images significantly better results compared to common thresholding techniques. Binarized images obtained by the proposed method can be particularly useful for particle detection and analysis of cell samples.

Comparison of image reconstruction methods for structured illumination microscopy

  • Autoři: Lukeš, T., Hagen, G. M., Křížek, P., Švindrych, Z., Ing. Karel Fliegel, Ph.D., prof. Ing. Miloš Klíma, CSc.,
  • Publikace: Biophotonics: Photonic Solutions for Better Health Care IV. Bellingham: SPIE, 2014. p. 91293J-1-91293J-13. Proceedings of SPIE. ISSN 0277-786X. ISBN 978-1-62841-077-8.
  • Rok: 2014
  • DOI: 10.1117/12.2052621
  • Odkaz: https://doi.org/10.1117/12.2052621
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Structured illumination microscopy (SIM) is a recent microscopy technique that enables one to go beyond the diffraction limit using patterned illumination. The high frequency information is encoded through aliasing into the observed image. By acquiring multiple images with different illumination patterns aliased components can be separated and a high-resolution image reconstructed. Here we investigate image processing methods that perform the task of high-resolution image reconstruction, namely square-law detection, scaled subtraction, super-resolution SIM (SR-SIM), and Bayesian estimation. The optical sectioning and lateral resolution improvement abilities of these algorithms were tested under various noise level conditions on simulated data and on fluorescence microscopy images of a pollen grain test sample and of a cultured cell stained for the actin cytoskeleton. In order to compare the performance of the algorithms, the following objective criteria were evaluated: Signal to Noise Ratio (SNR), Signal to Background Ratio (SBR), circular average of the power spectral density and the S-3 sharpness index. The results show that SR-SIM and Bayesian estimation combine illumination patterned images more effectively and provide better lateral resolution in exchange for more complex image processing. SR-SIM requires one to precisely shift the separated spectral components to their proper positions in reciprocal space. High noise levels in the raw data can cause inaccuracies in the shifts of the spectral components which degrade the super-resolved image. Bayesian estimation has proven to be more robust to changes in noise level and illumination pattern frequency.

Estimation and measurement of space-variant features of imaging systems and influence of this knowledge on accuracy of astronomical measurement

  • DOI: 10.1117/12.2061736
  • Odkaz: https://doi.org/10.1117/12.2061736
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Additional monitoring equipment is commonly used in astronomical imaging. This electro-optical system usually complements the main telescope during acquisition of astronomical phenomena or supports its operation e.g. evaluating the weather conditions. Typically it is a wide-field imaging system, which consists of a digital camera equipped with fish-eye lens. The wide-field imaging system cannot be considered as a space-invariant because of space-variant nature of its input lens. In our previous research efforts we have focused on measurement and analysis of images obtained from the subsidiary all-sky monitor WILLIAM (WIde-field aLL-sky Images Analyzing Monitoring system). Space-variant part of this imaging system consists of input lens with 180 fi angle of view in horizontal and 154 fi in vertical direction. For a precise astronomical measurement over the entire field of view, it is very important to know how the optical aberrations affect characteristics of the imaging system, especially its PSF (Point Spread Function). Two methods were used for characterization of the space-variant PSF, i.e. measurement in the optical laboratory and estimation using acquired images and Zernike polynomials. Analysis of results obtained using these two methods is presented in the paper. Accuracy of astronomical measurements is also discussed while considering the space-variant PSF of the system.

Evaluation of privacy in high dynamic range video sequences

  • Autoři: Řeřábek, M., Yuan, L., Krasula, L., Korshunov, P., Ing. Karel Fliegel, Ph.D., Ebrahimi, T.
  • Publikace: Applications of Digital Image Processing XXXVII. Bellingham: SPIE, 2014. pp. 92170E-1-92170E-13. Proceedings of SPIE. ISSN 0277-786X. ISBN 978-1-62841-244-4.
  • Rok: 2014
  • DOI: 10.1117/12.2065559
  • Odkaz: https://doi.org/10.1117/12.2065559
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The ability of high dynamic range (HDR) to capture details in environments with high contrast has a significant impact on privacy in video surveillance. However, the extent to which HDR imaging affects privacy, when compared to a typical low dynamic range (LDR) imaging, is neither well studied nor well understood. To achieve such an objective, a suitable dataset of images and video sequences is needed. Therefore, we have created a publicly available dataset of HDR video for privacy evaluation PEViD-HDR, which is an HDR extension of an existing Privacy Evaluation Video Dataset (PEViD). PEViD-HDR video dataset can help in the evaluations of privacy protection tools, as well as for showing the importance of HDR imaging in video surveillance applications and its influence on the privacy-intelligibility trade-off. We conducted a preliminary subjective experiment demonstrating the usability of the created dataset for evaluation of privacy issues in video. The results confirm that a tone-mapped HDR video contains more privacy sensitive information and details compared to a typical LDR video.

Objective evaluation of naturalness, contrast, and colorfulness of tone-mapped images

  • Autoři: Krasula, L., Ing. Karel Fliegel, Ph.D., Le Callet, P., prof. Ing. Miloš Klíma, CSc.,
  • Publikace: Applications of Digital Image Processing XXXVII. Bellingham: SPIE, 2014. p. 92172D-1-92172D-10. Proceedings of SPIE. ISSN 0277-786X. ISBN 978-1-62841-244-4.
  • Rok: 2014
  • DOI: 10.1117/12.2075270
  • Odkaz: https://doi.org/10.1117/12.2075270
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The main obstacle preventing High Dynamic Range (HDR) imaging from becoming standard in image and video processing industry is the challenge of displaying the content. The prices of HDR screens are still too high for ordinary customers. During last decade, a lot of effort has been dedicated to finding ways to compress the dynamic range for legacy displays with simultaneous preservation of details in highlights and shadows which cannot be achieved by standard systems. These dynamic range compression techniques are called tone-mapping operators (TMO) and introduce novel distortions such as spatially non-linear distortion of contrast or naturalness corruption. This paper provides an analysis of objective no-reference naturalness, contrast and colorfulness measures in the context of tone-mapped images evaluation. Reliable measures of these features could be further merged together into single overall quality metric. The main goal of the paper is to provide an initial study of the problem and identify the potential candidates for such a combination.

Performance evaluation of the emerging JPEG XT image compression standard

  • Autoři: Pinheiro, A., Ing. Karel Fliegel, Ph.D., Korshunov, P., Krasula, L., Bernardo, M., Pereira, M., Ebrahimi, T.
  • Publikace: 2014 IEEE 16th International Workshop on Multimedia Signal Processing (MMSP). Piscataway: IEEE, 2014. ISBN 978-1-4799-5896-2.
  • Rok: 2014
  • DOI: 10.1109/MMSP.2014.6958834
  • Odkaz: https://doi.org/10.1109/MMSP.2014.6958834
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The upcoming JPEG XT is under development for High Dynamic Range (HDR) image compression. This standard encodes a Low Dynamic Range (LDR) version of the HDR image generated by a Tone-Mapping Operator (TMO) using the conventional JPEG coding as a base layer and encodes the extra HDR information in a residual layer. This paper studies the performance of the three profiles of JPEG XT (referred to as profiles A, B and C) using a test set of six HDR images. Four TMO techniques were used for the base layer image generation to assess the influence of the TMOs on the performance of JPEG XT profiles. Then, the HDR images were coded with different quality levels for the base layer and for the residual layer. The performance of each profile was evaluated using Signal to Noise Ratio (SNR), Feature SIMilarity Index (FSIM), Root Mean Square Error (RMSE), and CIEDE2000 color difference objective metrics. The evaluation results demonstrate that profiles A and B lead to similar saturation of quality at the higher bit rates, while profile C exhibits no saturation. Profiles B and C appear to be more dependent on TMOs used for the base layer compared to profile A.

Segmentation of astronomical images

  • DOI: 10.1117/12.2062009
  • Odkaz: https://doi.org/10.1117/12.2062009
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Object detection is one of the most important procedures in astronomical imaging. This paper deals with segmentation of astronomical images based on random forrest classifier. We consider astronomical image data acquired using a photometric system with B, V, R and I filters. Each image is acquired in more realizations. All image realizations are corrected using master dark frame and master flat field obtained as an average of hundreds of images. Then a profile photometry is applied to find possible position of stars. The classifier is trained by B, V, R and I image vectors. Training samples are defined by user using ellipsoidal regions (20 selections for both classes: object, background). A number of objects and their positions are compared with astronomical object catalogue using Euclidean distance. We can conclude that the performance of the presented technique is fully comparable to other SoA algorithms.

System for objective assessment of image differences in digital cinema

  • Autoři: Ing. Karel Fliegel, Ph.D., Krasula, L., prof. Mgr. Petr Páta, Ph.D., Myslík, J., Pecák, J., Jícha, M.
  • Publikace: Applications of Digital Image Processing XXXVII. Bellingham: SPIE, 2014. pp. 92170I-1-92170I-14. Proceedings of SPIE. ISSN 0277-786X. ISBN 978-1-62841-244-4.
  • Rok: 2014
  • DOI: 10.1117/12.2061016
  • Odkaz: https://doi.org/10.1117/12.2061016
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    There is high demand for quick digitization and subsequent image restoration of archived film records. Digitization is very urgent in many cases because various invaluable pieces of cultural heritage are stored on aging media. Only selected records can be reconstructed perfectly using painstaking manual or semi-automatic procedures. This paper aims to answer the question what are the quality requirements on the restoration process in order to obtain acceptably close visual perception of the digitally restored film in comparison to the original analog film copy. This knowledge is very important to preserve the original artistic intention of the movie producers. Subjective experiment with artificially distorted images has been conducted in order to answer the question what is the visual impact of common image distortions in digital cinema. Typical color and contrast distortions were introduced and test images were presented to viewers using digital projector. Based on the outcome of this subjective evaluation a system for objective assessment of image distortions has been developed and its performance tested. The system utilizes calibrated digital single-lens reflex camera and subsequent analysis of suitable features of images captured from the projection screen. The evaluation of captured image data has been optimized in order to obtain predicted differences between the reference and distorted images while achieving high correlation with the results of subjective assessment. The system can be used to objectively determine the difference between analog film and digital cinema images on the projection screen.

Three-dimensional super-resolution structured illumination microscopy with maximum a posteriori probability image estimation

  • DOI: 10.1364/OE.22.029805
  • Odkaz: https://doi.org/10.1364/OE.22.029805
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    We introduce and demonstrate a new high performance image reconstruction method for super-resolution structured illumination microscopy based on maximum a posteriori probability estimation (MAP-SIM). Imaging performance is demonstrated on a variety of fluorescent samples of different thickness, labeling density and noise levels. The method provides good suppression of out of focus light, improves spatial resolution, and allows reconstruction of both 2D and 3D images of cells even in the case of weak signals. The method can be used to process both optical sectioning and super-resolution structured illumination microscopy data to create high quality super-resolution images.

Using full-reference image quality metrics for automatic image sharpening

  • Autoři: Krasula, L., Ing. Karel Fliegel, Ph.D., Le Callet, P., prof. Ing. Miloš Klíma, CSc.,
  • Publikace: Optics, Photonics, and Digital Technologies for Multimedia Applications III. Bellingham: SPIE, 2014. pp. 913807-1-913807-11. Proceedings of SPIE. ISSN 0277-786X. ISBN 978-1-62841-086-0.
  • Rok: 2014
  • DOI: 10.1117/12.2052275
  • Odkaz: https://doi.org/10.1117/12.2052275
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Image sharpening is a post-processing technique employed for the artificial enhancement of the perceived sharpness by shortening the transitions between luminance levels or increasing the contrast on the edges. The greatest challenge in this area is to determine the level of perceived sharpness which is optimal for human observers. This task is complex because the enhancement is gained only until the certain threshold. After reaching it, the quality of the resulting image drops due to the presence of annoying artifacts. Despite the effort dedicated to the automatic sharpness estimation, none of the existing metrics is designed for localization of this threshold. Nevertheless, it is a very important step towards the automatic image sharpening. In this work, possible usage of full-reference image quality metrics for finding the optimal amount of sharpening is proposed and investigated. The intentionally over-sharpened "anchor image" was included to the calculation as the "anti-reference" and the final metric score was computed from the differences between reference, processed, and anchor versions of the scene. Quality scores obtained from the subjective experiment were used to determine the optimal combination of partial metric values. Five popular fidelity metrics - SSIM, MS-SSIM, IW-SSIM, VIF, and FSIM - were tested. The performance of the proposed approach was then verified in the subjective experiment.

Analysis of images obtained from space-variant astronomical imaging systems

  • DOI: 10.1117/12.2023904
  • Odkaz: https://doi.org/10.1117/12.2023904
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Most of the classical approaches to the measurement and modeling of electro-optical imaging systems rely on the principles of linearity and space invariance (LSI). In our previous research efforts we have focused on measurement and analysis of images obtained from a double station video observation system MAIA (Meteor Automatic Imager and Analyzer). The video acquisition module of this system contains wide-field input lens which contributes to space-variability of the imaging system. For a precise astronomical measurement over the entire field of view, it is very important to comprehend how the characteristics of the imaging system can affect astrometric and photometric outputs. This paper presents an analysis of how the space-variance of the imaging system can affect precision of astrometric and photometric results. This analysis is based on image data acquired in laboratory experiments and astronomical observations with the wide-field system. Methods for efficient calibration of this system to obtain precise astrometric and photometric measurements are also proposed.

Distributed DASH dataset

  • Autoři: Lederer, S., Mueller, C., Timmerer, C., Concolato, C., Le Feuvre, J., Ing. Karel Fliegel, Ph.D.,
  • Publikace: Proceedings of the 4th ACM Multimedia Systems Conference. New York: ACM, 2013. pp. 131-135. ISBN 978-1-4503-1894-5.
  • Rok: 2013
  • DOI: 10.1145/2483977.2483994
  • Odkaz: https://doi.org/10.1145/2483977.2483994
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The delivery of multimedia content over HTTP and on top of existing Internet infrastructures is becoming the preferred method within heterogeneous environment. The basic design principle is having an intelligent client which selects given and applicable media representations by issuing HTTP requests for individual segments based on the users' context and current conditions. Typically, this client behavior differs between implementations of the same kind and for the objective evaluations thereof appropriate datasets are needed. This paper presents a distributed dataset for the recently published MPEG-DASH standard which is mirrored at different sites across Europe, namely Klagenfurt, Paris, and Prague. A client implementation may choose to request segments from these sites and dynamically switch to a different location, e.g., in case the one currently used causes any issues. Thus, this distributed DASH dataset can be used for real-world evaluations enabling the simulation of switching between different content delivery networks.

Modeling of quantization noise in linear analog-to-digital converter

  • DOI: 10.1117/12.2023048
  • Odkaz: https://doi.org/10.1117/12.2023048
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Quantization noise is present in all the current digital imaging systems, therefore its understanding and modeling is crucial for optimization of image reconstruction techniques. Hence, this paper deals with modeling of the quantization noise. We exploit the undecimated wavelet transform (UWT) for signal representation. We assume that the quantization noise in the spatial domain can be seen as additive, white and uniformly distributed. Hence, the UWT causes the transform of noise distribution due to weighted sum of noise samples and filter coefficients. From the known quantization step we are able to estimate suitable moments of noise uniform probability density function (PDF). These moments then could be directly evaluated in the undecimated wavelet domain using the derived equations. The presented algorithm gives the a priori information about the quantization noise and can be used for the suppression of it.

Objective image quality assessment of multiframe super-resolution methods

  • DOI: 10.1109/RadioElek.2013.6530929
  • Odkaz: https://doi.org/10.1109/RadioElek.2013.6530929
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Super-resolution (SR) represents a class of signal processing methods allowing to create a high resolution image (HR) from several low resolution images (LR) of the same scene. Therefore, high spatial frequency information can be recovered. Applications may include but are not limited to HDTV, biological imaging, surveillance, forensic investigation. In this paper, a survey of SR methods is provided with focus on the non-uniform interpolation SR approach because of its lower computational demand. Based on this survey eight SR reconstruction algorithms were implemented. Performance of these algorithms was evaluated by means of objective image quality criteria PSNR, MSSIM and computational complexity to determine the most suitable algorithm for real video applications. The algorithm should be reasonably computationally efficient to process a large number of color images and achieve good image quality for input videos with various characteristics. This algorithm has been successfully applied and its performance illustrated on examples of real video sequences from different domains.

Performance evaluation of image quality metrics with respect to their use for super-resolution enhancement

  • DOI: 10.1109/QoMEX.2013.6603205
  • Odkaz: https://doi.org/10.1109/QoMEX.2013.6603205
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Super-resolution (SR) methods enable to obtain high resolution image (HR) from multiple low resolution input images (LR) of the same scene. Development of SR algorithms for real applications require reliable image quality metrics for performance comparison of various SR methods. In this paper, six standard SR methods were implemented and subjective image quality assessment was performed to evaluate the visual quality of the enhanced images. Nine image quality metrics were examined with respect to their ability to characterize the observed subjective image quality of SR enhancement.

Comparison of stereoscopic technologies in various configurations

  • DOI: 10.1117/12.929237
  • Odkaz: https://doi.org/10.1117/12.929237
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The aim of this paper is twofold. In the first part of the paper we present results of subjective quality assessment based comparison of stereoscopic technologies in various configurations. Subjective assessment has been done on a limited set of observers while using a database of stereoscopic test videos of various source types. There is also comparison of results obtained with the same stereoscopic content from the two cooperating test laboratories. The results can be used to address different aspects of viewing experience, especially comparing passive and active stereoscopic display technologies. The second part of the paper is focused on preliminary experimental results analyzing the vergence-accommodation conflict present in current stereoscopic systems. Simultaneous measurement of the vergence and accommodation has been done with observers viewing a real scene and its stereoscopic reproduction.

Comparison of the astronomical and multimedia image quality criteria

  • DOI: 10.1117/12.923586
  • Odkaz: https://doi.org/10.1117/12.923586
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper deals with the criteria definition of image quality in astronomy and their comparison with common multimedia approaches. Astronomical images have typical specific properties - high grayscale bit depth, size, high noise occurrence, sensitivity to point spread function deformation and special processing algorithms. They belong to the class of scientific images as well as medical or similar. Their processing and compression is quite different from the classical approach of multimedia image processing. The new compression algorithm based on JPEG2000 is selected as a distortion source in this paper. Selected image quality criteria (multimedia and optimized for astronomical images) are tested on the set of images from the DEIMOS image database with miscellaneous level of the thermally generated CCD noise. The deformation of the point spread function (PSF) is also measured for chosen compression approach.

Estimation of non-Gaussian noise parameters in the wavelet domain using the moment-generating function

  • DOI: 10.1117/1.JEI.21.3.039802
  • Odkaz: https://doi.org/10.1117/1.JEI.21.3.039802
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    We discuss methods for modeling and removal of noise in astronomical images. For its favorable properties, we exploit the undecimated wavelet representation and apply noise suppression in this domain. Usually, the noise analysis of the studied imaging system is carried out in the spatial domain. However, noise in astronomical data is non-Gaussian, and thus the noise model parameters need to be estimated directly in the wavelet domain. We derive equations for estimating the sample moments for non-Gaussian noise in the wavelet domain. We consider that the sample moments in the spatial domain are known from the noise analysis and that the model parameters are estimated by using the method of moments.

Estimation of non-Gaussian noise parameters in the wavelet domain using the moment-generating function

  • DOI: 10.1117/1.JEI.21.2.023025
  • Odkaz: https://doi.org/10.1117/1.JEI.21.2.023025
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    We discuss methods for modeling and removal of noise in astronomical images. For its favorable properties, we exploit the undecimated wavelet representation and apply noise suppression in this domain. Usually, the noise analysis of the studied imaging system is carried out in the spatial domain. However, noise in astronomical data is non-Gaussian, and thus the noise model parameters need to be estimated directly in the wavelet domain. We derive equations for estimating the sample moments for non-Gaussian noise in the wavelet domain. We consider that the sample moments in the spatial domain are known from the noise analysis and that the model parameters are estimated by using the method of moments.

Measurement and Analysis of Real Imaging Systems

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper is devoted to statistical analysis of noise generated in real imaging systems and noise suppression methods. The introductory part is focused on description of imaging systems, image degradations, and noise types present in them. The noise analysis section includes determination of basic noise characteristics, the probability distribution and dependence on the signal. The described methods are used to compare properties of two digital still cameras: Nikon D70 and Canon EOS 500D and video camera: JAI CM-040GE. The section devoted to noise suppression discusses different methods of wavelet coefficients thresholding and threshold estimation. The wavelet coefficients are produced by two forms of the wavelet transform: the discrete wavelet transform and the dual-tree complex wavelet transform. The described noise suppression methods are applied to the data sets which were acquired by the analyzed systems under poor lighting conditions.

Utilization of Image Intensifiers in Astronomy

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In this paper we present the properties of image intensifiers, used together with fast TV cameras for astronomical purposes within the MAIA project(Meteor Automatic Imager and Analyser, primarily focused on observing meteoric events with high time resolution). The main objective of our paper is to evaluate the suitability of these devices for astronomical purposes in terms of noise, temporal and spectral analysis.

Wiener filtering in the process of dark current suppression

  • Autoři: Švihlík, J., Mojžíš, F., Ing. Karel Fliegel, Ph.D., Kukal, J.
  • Publikace: Applications of Digital Image Processing XXXV. Bellingham (stát Washington): SPIE, 2012. pp. 849925-1-849925-6. ISSN 0277-786X. ISBN 9780819492166.
  • Rok: 2012
  • DOI: 10.1117/12.928652
  • Odkaz: https://doi.org/10.1117/12.928652
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper is devoted to the dark current suppression in astronomical images using the wiener filtering. We consider dark current represented by dark frame as a white impulsive noise generated in CCD sensor. The wiener filter is then set up accordance to measured second sample moments at CCD at chosen temperature range 268K to 293K. Furthermore, the temperature dependency of the second sample moments was fit by exponential regression. Hence, we are able to find sample moment and suppress dark current at given temperature. The measurement was done at SBIG ST8 camera.

Analysis and suppression of noise in astronomical video

  • DOI: 10.1109/RADIOELEK.2011.5936386
  • Odkaz: https://doi.org/10.1109/RADIOELEK.2011.5936386
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper is devoted to noise suppression in systems for double station observation of meteors, nowadays known as MAIA (Meteor Automatic Imager and Analyzer). The noise analysis based on acquisition of testing video sequences at different lighting conditions and their statistical evaluation were described in our previous paper. The measurement showed that the type of noise generated by the system is signal-independent in a certain illumination range. The noise and image models in the wavelet domain are based on the Generalized Laplacian Model (GLM) and it is the most convenient to estimate the model parameters using the moment method. Furthermore, the noise component may be modeled by the GLM also in the space domain. Overall, we verified that the GLM allows for modeling various types of probability density functions. In the final section of this paper, the performance of the proposed advanced de-noising algorithm is verified on the real data, which were acquired in the Astronomical Institute.

Astronomical Image Compression Techniques Based on ACC and KLT Coder

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper deals with a compression of image data in applications in astronomy. Astronomical images have typical specific properties - high grayscale bit depth, size, noise occurrence and special processing algorithms. They belong to the class of scientific images. Their processing and compression is quite different from the classical approach of multimedia image processing. The database of images from BOOTES (Burst Observer and Optical Transient Exploring System) has been chosen as a source of the testing signal. A comparison of two irrelevancy reduction methods is presented from a scientific (astrometric and photometric) point of view. The first method is based on a statistical approach, using the Karhunen-Loeve transform (KLT) with uniform quantization in the spectral domain. The second technique is derived from wavelet decomposition with adaptive selection of used prediction coefficients. Finally, the comparison of three redundancy reduction methods is discussed.

Automatic Video System for Continues Monitoring of the Meteor Activity

  • DOI: 10.1007/s11038-011-9380-9
  • Odkaz: https://doi.org/10.1007/s11038-011-9380-9
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In this paper we present current progress in development of new observational instruments for the double station video experiment. The Meteor Automatic Imager and Analyser (MAIA) system is based on digital monochrome camera JAI CM-040 and well proved image intensifier XX1332. Both the observations as well as the data processing will be fully automatic. We are expecting the recorded data of better quality and both spatial and time resolution in comparison with currently used analogue system. The main goal of the MAIA project is to monitor activity of the meteor showers and sporadic meteor each night for the period of at least 3 years. First version of the system was already assembled and has been intensively tested in the optical laboratory. Optical properties were measured and the result confirmed our expectations according to image quality and resolution. First night sky observation was already carried out.

DEIMOS - an Open Source Image Database

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The DEIMOS (DatabasE of Images: Open Source) is created as an open-source database of images and videos for testing, verification and comparing of various image and/or video processing techniques such as enhancing, compression and reconstruction. The main advantage of DEIMOS is its orientation to various application fields - multimedia, television, security, assistive technology, biomedicine, astronomy etc. The DEIMOS is/will be created gradually step-by-step based upon the contributions of team members. The paper is describing basic parameters of DEIMOS database including application examples.

Enhancement of the accuracy of the astronomical measurements carried on the wide-field astronomical image data

  • DOI: 10.1117/12.894117
  • Odkaz: https://doi.org/10.1117/12.894117
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The properties of wide-field astronomical systems along with specific visual data in astronomical images contribute to complicated evaluation of acquired image data. The main goal of this paper is to present the advanced processing of the images obtained from wide-field astronomical systems and to introduce the way how to enhance the accuracy of astronomical measurements on these systems. The paper also deals with the modelling of the space variant high order optical aberrations which increase towards margins of the field of view and which distort the point spread function of optical system and negatively affect the image quality.

MAIA: Technical Development of a Novel System for Video Observations of Meteors

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    A system for double station observation of meteors now known as MAIA (Meteor Automatic Imager and Analyzer) is introduced in this paper. The system is based on two stations with gigabite ethernet cameras, sensitive image intensifiers and automatic processing of the recorded image data. This paper presents the measured electrooptical characteristics of the components and the overall performance of the new digital system in comparison with the current analog solution.

Meteor automatic imager and analyzer: current status and preprocessing of image data

  • DOI: 10.1117/12.893700
  • Odkaz: https://doi.org/10.1117/12.893700
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In this paper we present current progress in development of new observational instruments for the double station video experiment called MAIA (Meteor Automatic Imager and Analyzer). The main goal of the MAIA project is to monitor activity of the meteor showers and sporadic meteors. This paper presents detailed analysis of imaging parameters based on acquisition of testing video sequences at different light conditions. Among the most important results belong the analysis of opto-electronic conversion function and noise characteristics. Based on these results, requirements for image preprocessing algorithms are proposed.

Noise Analysis of MAIA System and Possible Noise Suppression

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper is devoted to the noise analysis and noise suppression in a system for double station observation of the meteors now known as MAIA (Meteor Automatic Imager and Analyzer). The noise analysis is based on acquisition of testing video sequences in different light conditions and their further statistical evaluation. The main goal is to find a suitable noise model and subsequently determine if the noise is signal dependent or not. Noise and image model in the wavelet domain should be based on Gaussian mixture model (GMM) or Generalized Laplacian Model (GLM) and the model parameters should be estimated by moment method. Furthermore, noise should be modeled by GMM or GLM also in the space domain. GMM and GLM allow to model various types of probability density functions. Finally the advanced denoising algorithm using Bayesian estimator is applied and its performance is verified.

Open source database of images DEIMOS: high dynamic range and stereoscopic content

  • DOI: 10.1117/12.893786
  • Odkaz: https://doi.org/10.1117/12.893786
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In this paper we present current progress in the project DEIMOS (Database of Images: Open Source). The DEIMOS database is an open-source database of images and videos for testing, verification and comparison of various image and/or video processing techniques. This paper presents additionally measured camera data available with high dynamic range image content and description of stereoscopic content available in the database. The database of stereoscopic images with various parameters in acquisition and image processing is intended for testing and optimization of metrics for objective image quality assessment. An example experiment of perceived image quality assessment depending on particular testing condition in stereoscopic image acquisition is presented. The database will be gradually annotated with mean opinion scores of perceived image quality from human observes for each testing condition.

Wavelet Transform for Processing of Video from MAIA System

  • DOI: 10.1117/12.912324
  • Odkaz: https://doi.org/10.1117/12.912324
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This article will present the use of wavelet transforms for image processing system of MAIA (Meteor Automatic Imager and Analyser). The main objective of these algorithms is the ob- ject detection with a high proportion of background noise and complicated imaging function. This noise is generated high brightness of the sky, an image intensifier and CCD sensor used. Analyzed images contain a large number of objects, which have dimensions of only a few pix- els. In such cases, it is very difficult to use conventional methods of analysis images that are failing. Application of wavelet transform allows the use of specific features of image function and effectively detect objects.

Advances in 3D imaging systems: Are you ready to buy a new 3D TV set?

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Proceedings of 20th International Conference Radioelektronika 2010. Brno: VUT v Brně, FEKT, Ústav radioelektroniky, 2010. pp. 3-8. ISBN 978-1-4244-6319-0.
  • Rok: 2010
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    There is a growing interest in the media industry towards stereoscopic television (3DTV). This attention is caused by the content producers but also by the consumer sector. At first the article presents an overview of development in the area of 3D presentation of moving images which actively started more than 60 years ago. The article aims to summarize the phenomena on which the 3D technologies are based but also presents the latest trends in this area. Diverse 3D display technologies are briefly explained, e.g. projection with special polarizing or colored glasses, flat displays combined with shutter glasses, autostereoscopic systems and other systems including volumetric imaging techniques. Stereoscopic systems have already settled firmly in public movie theaters. On the other hand the development in TV industry is still in its infancy. The article presents some recent recommendations for stereo TV systems and gives a prediction of 3D application spread into our homes.

Double-Station Automatic Video Observation of the Meteors

  • DOI: 10.1155/2010/943145
  • Odkaz: https://doi.org/10.1155/2010/943145
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The double station observation of the meteors by means of sensitive image intensifier technique started at the Ondrejov Observatory 10 years ago. The sensitivity of such instrumentation allows detection of the meteors down to masses of fractions of gram. Moreover, video technique provides us with a time resolution of the meteor events. On the other side, the precision of the video data is lower in comparison with the photographic data. We are introducing technological progress on the project-replacing of the S-VHS camcorders with gigabite, ethernet cameras and making the whole process of video observation automatic.

Meteor automatic imager and analyzer: analysis of noise characteristics and possible noise suppression

  • DOI: 10.1117/12.859685
  • Odkaz: https://doi.org/10.1117/12.859685
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper is devoted to the noise analysis and noise suppression in a system for double station observation of the meteors now known as MAIA (Meteor Automatic Imager and Analyzer). The noise analysis is based on acquisition of testing video sequences at different light conditions and their further analysis. The main goal is to find a suitable noise model and subsequently determine if the noise is signal dependent or not. Noise and image model in the wavelet domain should be based on Gaussian mixture model (GMM) or Generalized Laplacian Model (GLM) and the model parameters should be estimated by moment method. GMM and GLM allow to model various types of probability density functions. Finally the advanced de-noising algorithm using Bayesian estimator will be applied.

Meteor automatic imager and analyzer: system design and its parameters

  • DOI: 10.1117/12.859935
  • Odkaz: https://doi.org/10.1117/12.859935
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    A system for double station observation of the meteors now known as MAIA (Meteor Automatic Imager and Analyzer) is introduced in the paper. This system is an evolution of current analog solution. The system is based on the two stations with the gigabite ethernet cameras, sensitive image intensifiers and automatic processing of the recorded image data. The aim of such design is to capture and analyze images of meteors down to masses of fractions of gram. This paper presents the measured electrooptical characteristics of the particular components and the overall performance of the new digital system in the comparison to the current analog solution. At first the optimal settings of various parameters for each subsystem (primary lens, image intensifier, secondary lens and camera) are determined. Then the set of test images is captured and analyzed. The analysis of the images captured with both artificial and real targets verifies the suitability of the selected system design.

New open source image database for testing and optimization of image processing algorithms

  • DOI: 10.1117/12.854465
  • Odkaz: https://doi.org/10.1117/12.854465
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Development, testing, verification and comparison of various image processing techniques require suitable database of test images. In this paper the DEIMOS, an open-source database, is introduced. This database is aiming various application fields of image processing such as enhancement, compression and reconstruction. At first requirements on different image classes are defined in respect to the specific area of application. The paper also describes basic parameters of the database. There are selected application examples to illustrate extensive database content. The DEIMOS database is created gradually step-by-step based upon the contributions of team members.

Open source database of images DEIMOS: high dynamic range images

  • DOI: 10.1117/12.859940
  • Odkaz: https://doi.org/10.1117/12.859940
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Efficient development of image processing techniques requires a database of suitable test images for verification of the performance, optimization and other related purposes. In this paper, the DEIMOS, an open-source database, is described including its structure and interface. There is a selected application example on high dynamic range content to illustrate the database features. This HDR image database contains a variety of natural scenes captured with a digital single-lens reflex camera (DSLR) under different conditions. The important capture parameters as well as the important characteristics of the camera are part of the database to ensure that the creation of each image is well documented. The DEIMOS database is created gradually step-by-step based upon the contributions of team members.

Prostorové zobrazování a 3DTV

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Tento článek ve své první části uvádí přehled vývoje v oblasti prezentace 3D obrazu, který aktivně započal před více než 60 lety. Dále jsou zde shrnuty nejdůležitější jevy, na kterých jsou 3D technologie založeny. Článek představuje také nejnovější trendy v této oblasti. Stručně jsou zde vysvětleny základy různých 3D zobrazovacích technologií, např. projekce se speciálními polarizačními či barevnými brýlemi, technologie plochých displejů s přepínanými brýlemi, autostereoskopických systémů a dalších systémů, včetně objemové zobrazovací techniky. V článku jsou prezentována vybraná doporučení pro stereoskopické televizní systémy a rovněž i perspektiva pro rozšíření 3D technologií v našich domovech.

Utilization of consumer level digital cameras in astronomy

  • DOI: 10.1117/12.860981
  • Odkaz: https://doi.org/10.1117/12.860981
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper presents a study of possible utilization of digital single-lens reflex (DSLR) cameras in astronomy. The DSLRs have a great advantage over the professional equipments in better cost efficiency with comparable usability for selected purposes. The quality of electro-optical system in the DSLR camera determines the area where it can be used with acceptable precision. At first a set of important camera parameters for astronomical utilization is introduced in the paper. Color filter array (CFA) structure, demosaicing algorithm, image sensor spectral properties, noise and transfer characteristics are the parameters that belong among the very important ones and these are further analyzed in the paper. Compression of astronomical images using the KLT approach is also described below. The potential impact of these parameters on position and photometric measurement is presented based on the analysis and measurements with the wide-angle lens.

A utilization of GMM for scientific images modeling

  • Autoři: Ing. Karel Fliegel, Ph.D., Švihlík, J.
  • Publikace: Applications of Digital Image Processing XXXII. Bellingham (stát Washington): SPIE, 2009. p. 74431R-1-74431R-12. ISSN 0277-786X. ISBN 978-0-8194-7733-0.
  • Rok: 2009
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper deals with modeling of scientific and multimedia images in the wavelet domain. Images transformed into wavelet domain have a special shape of probability density function (PDF). Thus wavelet coefficients PDFs are usually modeled using generalized Laplacian PDF model (GLM), which is characterized by two parameters. The wavelet coefficients modeling can be more efficient, while the Gaussian mixture model (GMM) is utilized. GMM model is given by addition of at least two Gaussian PDFs with different standard deviations. There will be presented equation system derived by moment method for GMM models parameters estimation. The equation system was derived for an addition of two GMM models. So it is suitable for advanced denoising systems, where an addition of two GMM random variables is considered (e.g. dark current in astronomical images).

Aktuální trendy ve velkoplošném zobrazování a prostorovém zvuku

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Příspěvek podává přehled o aktuálních trendech ve velkoplošném zobrazování a prostorovém zvuku.

Image Quality and QoE in Multimedia Systems

  • Autoři: prof. Ing. Miloš Klíma, CSc., Ing. Karel Fliegel, Ph.D., Kekrt, D., Dostál, P., Podgorný, R.
  • Publikace: Proceedings of 19th International Conference Radioelektronika 2009. Bratislava: FEI, Slovak University of Technology, 2009. pp. 3-10. ISBN 978-80-214-3865-1.
  • Rok: 2009
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The image and video sensing and processing systems are of high importance nowadays. The crucial parameter is image quality as a part of QoS or more recently QoE (Quality of Experience) as a subjective impact (perception). This invited paper deals with various qualitative aspects in imaging systems. The first part is devoted to the modeling of HVS and image quality evaluation. A model for prediction of perceived quality of degraded images is presented. This model is optimized while incorporating visual attention coordinates. In the following parts four different examples of qualitative impacts (distortions and artifacts) of image postprocessing are listed and shown. The first one is the image enhancement, second one image restoration by iterative detectors based on the maximum a posteriori probability criterion, third one image interpolation and finally fourth one image compression and transmission.

Imaging photometer with a non-professional digital camera

  • Autoři: Ing. Karel Fliegel, Ph.D., Havlín, J.
  • Publikace: Applications of Digital Image Processing XXXII. Bellingham (stát Washington): SPIE, 2009. p. 74431Q-1-74431Q-8. ISSN 0277-786X. ISBN 978-0-8194-7733-0.
  • Rok: 2009
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In this paper we present a simple way how to use a consumer level digital camera as a 2D luminance meter or imaging photometer. Our approach is based mostly on measurement of spectral response curves of photosensitive elements and evaluation of output response from the raw image data captured by the camera. Utilization of these characteristics leads to a better calibration of the camera as a luminance meter. The performance improvement while using the image calibration data of the image sensor and objective lens is verified. The potential utilization of a consumer level digital camera as a substitute for expensive measuring devices is discussed.

Processing and Compression of Astronomical Images from optical All-Sky System

  • Autoři: Řeřábek, M., prof. Mgr. Petr Páta, Ph.D., Ing. Karel Fliegel, Ph.D., Koten, P.
  • Publikace: 4th EOS Topical Meeting on Advanced Imaging Techniques. Hannover: European Optical Society Coherence for Europe, 2009. pp. 66-67. ISBN 978-3-00-024189-5.
  • Rok: 2009
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper is aimed at a scientific image data processing and compression. The analyzed data is obtained from all-sky optical systems. An alternative low-cost optical all-sky system for astronomical observing will be briefly described. The study also deals with possibility of Karhunen - Loève Transform (KLT) application for astronomical data compression.

Restoration of dichromatic images gained from CCD/CMOS camera by iterative detection networks with fragmented marginalization at the symbol block level

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The IDNs are composed of certain, as simple as possible, statistical devices (SISO modules) and can be separated into two basic groups with variable topology (exactly matched to the blurring kernel) and with fixed topology, same for all possible kernels. The paper deals with second group of IDNs, concretely with IDNs whose SISO modules are concatenated in three directions (horizontal, vertical and diagonal). Advantages of such ordering rests in the application flexibility (can be comfortable applied to many irregular cores) and also in the low exigencies to number of memory devices it the IDN. The mentioned IDN type will be implemented in the two different variants suppressing defocusing in the lens of CCD/CMOS sensing system and will be verified in the sphere of a dichromatic 2D barcode detection.

Spatially adaptive image quality metrics for perceptual image quality assessment

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Mathematics for Signal and Information Processing. Bellingham: SPIE, 2009. pp. 744406-1-744406-8. ISSN 0277-786X. ISBN 978-0-8194-7734-7.
  • Rok: 2009
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The problem of objective image quality assessment has been known for couple of decades but with emerging multimedia technologies it becomes very important. This paper presents an approach to predict perceived quality of compressed images while incorporating real visual attention coordinates. Information about the visual attention is not usually taken into account in models for image quality assessment. Impact of the region of interest on estimation accuracy of a simple image quality metric has been investigated in our previous papers. The gaze coordinates were calculated using calibrated electro-oculogram records of human observers while watching a number of test images. This paper further investigates this idea using data from more observers. Obtained mean opinion scores of perceived image quality and eye tracking data were used to verify potential improvement of assessment accuracy for a simple image quality metric.

Eyetracking based approach to objective image quality assessment

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Proceedings of 42nd Annual 2008 IEEE International Carnahan Conference on Security Technology. Piscataway: IEEE, 2008. p. 371-376. ISBN 978-1-4244-1816-9.
  • Rok: 2008
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper presents an approach to predict perceived quality of compressed images while incorporating real visual attention coordinates. Information about the visual attention is not usually taken into account in models for image quality assessment. The idea of implementing gaze information into the image quality assessment system lies in that the artefacts are more disturbing to human observer in the region with higher saliency than in other parts of an image. Impact of the region of interest on estimation accuracy of a simple image quality metric is investigated. The gaze coordinates were calculated using calibrated electro-oculogram records of human observers while watching a number of test images. The same images were used for subjective image quality assessment. Obtained mean opinion scores of perceived image quality and eye tracking data were used to verify potential improvement of assessment accuracy for a simple image quality metric.

Optimization of HVS based objective image quality assessment with eye tracking

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Mathematics of Data/Image Pattern Recognition, Compression, and Encryption with Applications XI. Bellingham: SPIE, 2008. pp. 707506-1-707506-12. ISSN 0277-786X. ISBN 978-0-8194-7295-3.
  • Rok: 2008
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In this paper, we present an approach to predict perceived quality of compressed images while incorporating real visual attention coordinates. The idea of implementing gaze information into the image quality assessment system lies in that the artefacts are more disturbing to human observer in the region with higher saliency than in other parts of an image. Impact of the region of interest on estimation accuracy of a simple image quality metric is investigated. The gaze coordinates were calculated using calibrated electro-oculogram records of human observers while watching a number of test images. Obtained mean opinion scores of perceived image quality and eye tracking data were used to verify potential improvement of assessment accuracy for a simple image quality metric. Based on the proven effect, our previously developed system for still image quality assessment has been adapted while utilizing information about the visual attention.

Pokroky v digitálním zpracování audio a video signálů - uživatelské hledisko

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Digitální zpracování audio a video signálů je v dnešní době již téměř samozřejmostí a analogové zpracování je již na ústupu. Příspěvek je rozdělen na dvě části, kde první se zabývá zpracováním audiosignálu a druhá část zpracováním obrazového signálu a videosignálu. Úvodní odstavce v obou částech přibližují čtenáři problematiku zpracování audiovisuální informace obecně. Dále je vyjmenováno a popsáno několik zajímavých metod zpracování zvuku a obrazu.

The iterative detection network based suppression of the thermal noise and blurring due to object moving in black and white pictures shot by a camera with CCD/CMOS sensor

  • DOI: 10.1117/12.794224
  • Odkaz: https://doi.org/10.1117/12.794224
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper deals with elimination of blurring caused by the object moving and thermal noise in black & white pictures captured by a CCD/CMOS camera. This problem can be also interpreted like image passage through some kind of ISI channel with specific 2D impulse response. Hence for purposes of image recovery we can use the MAP criterion based iterative detection network (IDN) containing a number of mutually concatenated functional blocks so-called soft inversions (SISOs). This cellular structure makes IDN suboptimal but also numerically very simple and practically applicable in contrast to an unviable optimal (single-stage) MAP detector. The image reconstruction example is presented.

An Efficient Method of Noise Suppression in Security Systems

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper is devoted to denoising technique for video noise removal and deals with advanced WT (Wavelet Transform) based method of noise suppression for security purposes. Our goal was to optimize the WT based algorithm to be applicable for the noise suppression in security videos with high computational efficiency. Preprocessing is applied to the output of the sensing system to make the video data more suitable for further denoising. Then a WT based statistical denoising method is applied. The method uses BLSE (Bayesian Least Square Error Estimator) of WT coefficients while utilizing generalized Laplacian PDF modeling and optimized moment method for parameters estimation. Several tests have been done to verify high noise suppression performance, computational efficiency and low distortion of important features.

Examples of Subjective Image Quality Enhancement in Multimedia

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper presents an experimental testing of three different digital techniques for the subjective image quality enhancement - color saturation, edge enhancement, denoising operators and noise addition - well known from both the digital photography and video. The evaluation has been done for extensive operator parameterization and the results are summarized and discussed. It has been demonstrated that there are relevant types of image corrections improving to some extent the subjective perception of the image. The above mentioned techniques have been tested for five image tests with significantly different image characteristics (fine details, large saturated color areas, high color contrast, easy-to-remember colors etc.). The experimental results show the way to optimized use of image enhancing operators. Finally the concept of impressiveness as a new possible expression of subjective quality improvement is presented and discussed.

Experimental Verification of a Posteriori Quality Enhancement of Security Images

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The security imaging systems have special qualitative requirements - the general perceptive image quality is not so important compared to the preservation of selected security image characteristics such as an identification or classification. In the first part we have tested the impact of image enhancing algorithms on the display readability in presence of noise. We have chosen the registration plate as an example and two noise types have been added in order to find the readability threshold. The second part has been devoted to de-noising techniques for image noise removal and deals with advanced WT based method of noise suppression for security purposes. Specific requirements on the proposed noise suppression technique can be stated. It should be efficient, both in the sense of low computational complexity but also by means of high noise suppression performance. Moreover, the system must preserve all the important features of the scene being watched.

Image Quality Evaluation in Security Imaging Systems

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In the paper we discuss selected important facts related to the subjective image quality evaluationand we present some anomalous experimental behavior of image compression techniques.

Perceptual Assessment of Image Quality in Multimedia Technology

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Mathematics of Data/Image Pattern Recognition, Compression, Coding, and Encryption X, with Applications. Bellingham: SPIE, 2007. pp. 670008-01-670008-08. ISBN 978-0-8194-6848-2.
  • Rok: 2007
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    A model for perceptual assessment of image quality in multimedia technology is presented in this paper. The model exploits properties of the human visual system (HVS) while utilizing steerable pyramidal decomposition. Image distortion features are based on Jeffrey divergence (JD) as a metric between probability distributions of original and distorted image signal values in each subband of steerable pyramid. Mean square error (MSE) is also computed. Data preprocessing using mutual information (MI) approach has been used to get a smaller set of objective distortion features describing the perceived image quality with reasonable precision. The impairment feature vector is processed by the radial basis function (RBF) artificial neural network (ANN) to allow simple adaptation of the model in respect to the required mode of operation, fidelity or impressiveness based. The presented system mimics an assessment process with human subjects.

Počítačově podporovaná výuka v oblasti multimediální techniky

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Oblast multimediální techniky je široká, spadá do ní vše, co se dotýká lidských smyslů, především zraku a sluchu. V užším významu se pod touto oblastí rozumí oblast audiovizuální techniky, rozhlasu a televize, která přináší rozsáhlé a rychlé změny technologie. Pro výuku předmětů ze zmiňovaných oblastí byla na našem pracovišti vybudována nová multimediální počítačová laboratoř, jejíž vybavení umožňuje vytvoření nových a moderních úloh. Vybavení laboratoře zahrnuje technické prostředky pro snímání, zdrojové kódování, záznam, zpracování a reprodukci zvukové a obrazové informace. Pro výuku ve vyjmenovaných oblastech lze s výhodou využít programové prostředí Matlab, jak ukazuje tento článek.

Potlačení obrazového šumu ve videozáznamu z bezpečnostních kamer

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    V tomto příspěvku je popsána metoda pro potlačení obrazového šumu ve videozáznamu. Tato metoda využívá pokročilých algoritmů založených na vlnkové transformaci (Wavelet Transform - WT) zejména s ohledem na použití v bezpečnostních kamerových systémech. V reálném kamerovém systému se vyskytuje řada nežádoucích zkreslení obrazu, zejména pokud je videozáznam snímán za zhoršených světelných podmínek. Naším cílem bylo optimalizovat rekonstrukční algoritmy založené na WT, tak aby je bylo možno použít pro potlačení šumu v záznamu z bezpečnostní kamery při zachování vysoké účinnosti a přijatelných výpočetních nároků.

Space Variant Point Spread Function Modeling for Astronomical Image Data Processing

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper deals with evaluation and processing of astronomical image data, which are obtained by WFC (Wide-Field Camera) or UWFC (Ultra Wide-Field Camera) systems. Precision of astronomical image data post-processing and analyzing is very important. Large amount of different kinds of optical aberrations and distortions is included in these systems. The amplitude of wavefront aberration error increases towards margins of the FOV (Field of View). Relation between amount of high order optical aberrations and astrometry measurement precision is discussed in this paper. There are descriptions of the transfer characteristics of astronomical optical systems presented in this paper. Spatially variant (SV) optical aberrations negatively affect the transfer characteristics of all system and make it spatially variant as well. SV model of optical system is presented in this paper. Partially invariant model of optical systems allows using Fourier methods for deconvolution.

A Method for Objective Image Quality Assesment Utilizing Artificial Neural Network with Enhanced Data Preprocessing

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Radioelektronika 2006 - Conference Proceedings. Bratislava: Slovak University of Technology, 2006. pp. 230-233. ISBN 80-227-2388-6.
  • Rok: 2006
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Possible enhancement of our novel approach to image quality evaluation utilizing Artificial Neural Network is presented. Advanced method of data preprocessing is applied to obtain good prediction of the image quality close to subjective results.

A model utilizing artificial neural network for perceptual image quality assessment in image compression algorithms

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Mathematics of Data/Image Pattern Recognition, Compression, and Encryption with Applications IX. Bellingham: SPIE, 2006. pp. 631507-1-631507-10. ISSN 0277-786X. ISBN 0-8194-6394-9.
  • Rok: 2006
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In this paper, we present a novel approach to predict the perceived image quality. Properties of the Human Visual System (HVS) were exploited to select a set of suitable metrics. These metrics are extracted while comparing the reference and distorted image. Mutual Information (MI) and Principal Component Analysis (PCA) were used to obtain an optimal set of objective features that best describe the perceived image quality in respect to subjective scores from human observers. The impairment feature vector is for¬warded to the Artificial Neural Network (ANN) where the features are combined and the predicted quality score is computed. Parameters of the ANN are adjusted using Mean Opinion Scores (MOS) obtained from the group of assessors. It is shown that the proposed image quality assessment model can achieve high correlation with the subjective image quality ratings. Possible incorporation of the model into a perceptual image-coding algorithm is proposed.

Advanced HVS model for perceptually optimized video encoder

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Seminář o řešení projektu GA ČR 102/03/H109 v roce 2006. Brno: VUT v Brně, Fakulta elektrotechniky a komunikačních technologií, 2006. pp. 41-44. ISBN 80-214-3304-3.
  • Rok: 2006
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper summarizes results achieved in the frame of the research program 102/03/H109 Methods, structures and components of electronic wireless communication of the Grant Agency of the Czech Republic (GACR) in 2006.

Advanced Image Quality Assessment Approach using Multiple Quality Measures with the Artifical Neural Network Data Processing Support

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Photonics, Devices, and Systems III. Bellingham: SPIE, 2006. p. 1Z-1-1Z-6. Proceedings of SPIE. ISSN 0277-786X. ISBN 0-8194-6236-5.
  • Rok: 2006
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper deals with subjective ane objective image quality evaluation.Possible enhancement of the performance in existent image quality assessment approaches using multiple quality measures with the support of the artifical neural network data processing is proposed.

Design of CMOS-APS Smart Imagers with Mixed Signal Processing and Analysis of their Transfer Characteristics

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    In this paper, the concept of Modulation Transfer Function (MTF) analysis is generalized to be applicable to the sampled structures of CMOS APS. Recalling theoretical results, we have analytically derived the detector MTF in the closed form for some special active area shapes. The paper also deals with the method based on pseudorandom image pattern with uniform power spectral density (PSD). This method allows to evaluate (in contrast to other methods) spatial invariant MTF including sampling MTF. It is generally known that a signal acquired by image sensor contains different types of noises. The superposition of these noises produces noise with a Gaussian distribution. The denoising method based on Bayesian estimator for implementation into the smart imager is presented.

Efficient Model for Image Quality Assessment Utilizing Artificial Neural Network

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Radio-Electronics, Electrical and Power Engineering. Moscow: Moskovskij energeticeskij institut, 2006. pp. 125-126. ISBN 5-87789-022-0.
  • Rok: 2006
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper deals with objective quality evaluation of distorted images. Optimization of the novel model for image quality evaluation with ANN has been done. Advanced method od data preprocessing was applied.

Image and Video Processing for Image Quality Evaluation Using Artificial Neural Network

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Proceedings of Workshop 2006. Praha: České vysoké učení technické v Praze, 2006. pp. 150-151. ISBN 80-01-03439-9.
  • Rok: 2006
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    A novel approach for objective image quality assessment is presented in this paper. Reliable methods are often required to evaluate the quality effects of the visual artifacts appearing in a digital image processing while using lossy image compression. Optimization of the previously proposed model for image quality evaluation with Artificial Neural Network (ANN) has been done. The main aim of this approach is to automatically derive a score that is the same as, or at least well correlated with the Mean Opinion Score (MOS) obtained from the subjective votes of many observers. Advanced method of data preprocessing (Mutual Information - MI and Principal Component Analysis - PCA) has been applied to obtain good prediction of the image quality which is close to subjective results from the group of observers - Mean Opinion Scores (MOS). The proposed model achieves good prediction performance for used test samples.

Modeling of Visual Perception of Image Impairment Features

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: POSTER 2006. Praha: České vysoké učení technické v Praze, 2006. pp. 1-5.
  • Rok: 2006
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper presents an attempt tobetter understanding how coding artifacts and distortions can deteriorate the perceived image quality. A novel method for image quality assessment is described. It utilizes suitable properties of Artificial Neural Networks (ANN). The proposed quality assessment model has been trained and tested using a set of grayscale images distorted by selected image compression algorithms. Additionally an advanced method of data preprocessing (Mutual Information - MI and Principal Component Analysis - PCA) has been applied to obtain good prediction of the image quality that is close to subjective results. Good quality score prediction has been demonstrated in terms of Pearson correlation between the subjective Mean Opinion Scores (MOS) and ANN's output. The proposed model achieves good prediction performance for used test samples.

Proč a jak modelovat lidské vidění pro potřeby odhadu kvality obrazu a návrh medicínských zobrazovacích systémů

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Tento článek se zabývá problematikou modelování lidského vidění pro hodnocení kvality obrazu. Stručně popisuje dva základní přístupy hodnocení kvality obrazu: odhad kvality subjektivní se skupinou pozorovatelů a objektivní. S ohledem na výhody a nevýhody subjektivních testů je zdůrazněna potřeba návrhu dostatečně přesných metrik pro objektivní odhad kvality obrazu. Jednoduché matematické charakteristiky dávají v řadě případů velice nepřesné, pouze orientační výsledky. Za účelem dokonalejšího testování vlivu zkreslení v obraze byla navržena řada metod využívajících více či méně zjednodušený model lidského vizuálního systému HVS. V textu je popsána podstata funkce těchto systémů a uvedeny základní principy některých vybraných modelů.

Quality Enhancement in Security Image Information

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The image quality of image or video information is a crucial issue in security imaging systems. Our paper deals with three different points - a posteriori image improvement, objective image quality assessment and noise removal. In the first part we have tested and evaluated the impact of edge-enhancing operators. Their performance is of two contradictory effects - edge sharpening and noise level increase. The second part summarizes the ANN application in the objective image quality evaluation procedure. The advanced approach is based upon two advanced methods - Mutual Information MI and Principal Component Analysis PCA. The third part is devoted to the DWT noise-removal technique and the experimental results are presented.

A Novel Method for Objective Image Quality Assessment using Artificial Neural Network

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Seminář o řešení projektu GA ČR 102/03/H109 v roce 2005. Brno: VUT v Brně, Fakulta elektrotechniky a komunikačních technologií, 2005. pp. 40-42. ISBN 80-214-3013-3.
  • Rok: 2005
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    A novel method for image quality assessment was developed, implemented into a model and its performance was evaluated. The model consists of the two main parts: the impairment feature extraction block and ANN as a combiner. It was shown that the proposed image quality assessment model can achieve high correlation with the subjective ratings MOS.

H.264 - Moderní standard pro kompresi videa

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Článek se zabývá základním popisem kompresního standardu H.264/AVC zejména s ohledem na porovnání se standardy staršími. Standard H.264/AVC vznikl v rámci společného projektu ITU-T Video Coding Experts Group (VCEG) a ISO/IEC Moving Pictures Experts Group (MPEG). Cílem projektu bylo vytvořit jednoduchý standard pro kompresi videa, který by využíval běžných metod a byl vhodný pro síťové přenosy (konverzační - videotelefon, nekonverzační - vysílání, záznam). H.264 je přibližně 2x efektivnější než MPEG2 a jiné běžné standardy. MPEG2 vyhovoval širokopásmovému přenosu, nikoli úzkopásmovější UMTS či xDSL. V článku jsou presentovány výsledky subjektivních testů perspektivního standardu H.264, starší komprese MPEG2 a populárního DivX. Testy jsou věnovány dopadu komprese videa na obrazovou kvalitu v dohledových systémech.

Image Quality Assessment Tool with the Artificial Neural Network

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Applied Electronics 2005 - International Conference Pilsen. Plzeň: Západočeská universita, 2005. pp. 109-112. ISBN 80-7043-369-8.
  • Rok: 2005
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper deals with the objective image quality evaluation. The novel method for the quality assessment of compressed images is described in this paper. Image quality scores of distorted images are estimated using oriented multichannel pyramidal decomposition and artificial neural network as a postprocessor. Performance of the implemented model for the image quality assessment has been evaluated using the database of distorted images and subjective image quality assessment. The proposed model achieves good prediction performance for used test samples.

Image Quality Assessment Using Oriented Multichannel Pyramidal Decomposition and Artificial Neural Network Data Postprocessing

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Radioelektronika 2005 - Conference Proceedings. Brno: VUT v Brně, FEI, Ústav radioelektroniky, 2005. pp. 175-178. ISBN 80-214-2904-6.
  • Rok: 2005
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The novel method for the quality assessment of compressed images is described in this paper. Quality scores (highly correlated with experimental) are estimated using oriented multichannel pyramidal decomposition and artificial neural network as a postprocessor.

Image Quality Evaluation in Applied TV Security Systems

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper deals with specific image quality problems in TV security systems when the image compression is used. The image quality optimization criteria are listed and selected examples of real application are demonstrated.

Novel Approach to the Image Quality Assessment Using Oriented Multichannel Decomposition and Artificial Neural Network Data Postprocessing

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: 9th International Student Conference on Electrical Engineering. Praha: České vysoké učení technické v Praze, Fakulta elektrotechnická, 2005.
  • Rok: 2005
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The novel method for the quality assessment of compressed images is described in this paper.

Objective Image Quality Evaluation Using Artificial Neural Network

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Proceedings of Workshop 2005. Praha: České vysoké učení technické v Praze, 2005. pp. 376-377. ISBN 80-01-03201-9.
  • Rok: 2005
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    This paper deals with the enhanced approach to the objective quality assessment of video signals in the multimedia systems. Objective image and video quality evaluation plays very important role in the systems for signal recording and transmission. Higher precision of the image quality evaluation helps to optimize both recording and transmission system in order to minimize the bitrate needed to achieve as high image quality as possible. This paper presents the brief overview of the subjective and objective image quality evaluation methods and shows the proposal of the system for the video quality assessment using Artificial Neural Network (ANN).

Smart Imagers and Their Characteristics

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Proceedings of SPIE - Smart Imagers and Their Application. Washington: The International Society for Optical Engineering, 2005. pp. 151-162. ISSN 0277-786X. ISBN 0-8194-5950-X.
  • Rok: 2005
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The main objective of this paper has been to use a generalized OTF, which is primarily dedicated to the description of linear space invariant systems (LSI), for the purpose of sampled structures of image sensors (e.g. CCD, CMOS, CID) including smart ones, and to implement the derived results while utilizing the graphical user interface (GUI) in Matlab programming environment. The paper also includes an experimental measurement in the real system and a comparison with the results of modeling.

Subjective and Objective Video Quality Assesment in the Field of Security Technology

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Radio-Electronics, Electrical and Power Engineering. Moscow: Moskovskij energeticeskij institut, 2005. pp. 103-104. ISBN 5-87789-019-0.
  • Rok: 2005
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Methods for subjective and objective image quality assessment are presented in relation to the security systems. Results from several video codec tests in the surveillance systems are shown. Novel approach for the objective image quality assessment using an artificial neural network data postprocessing is proposed.

Subjective Image Quality Evaluation in Security Imaging Systems

Charakteristiky obrazových snímačů v modelech a měření

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Sborník příspěvků konference RADEŠÍN 2004. Brno: FEKT VUT v Brně, 2004. pp. 35-36. ISBN 80-214-2726-4.
  • Rok: 2004
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Příspěvek se zabývá použitím zobecněné MTF vzorkovaných struktur obrazového systému s využitím grafického uživatelského rozhraní GUI v programovém prostředí Matlab. Použitý model uvažuje vliv tvaru fotocitlivé oblasti detektoru, vzorkovacího procesu a dalších parametrů, jako je účinnost přenosu náboje, či difuze na průběh MTF. Byla též provedena měření na reálné soustavě včetně srovnání s výsledky modelování.

Image Compression Techniques in the Field of Security Technology: Examples and Discussion

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The image compression techniques are widely applied in the field of security technology (perimeter supervision, CCTV in facilities, faces, fingerprints, car plates etc.). The extensive and dramatically expanding use of image information requires increasing capacity of either transmission channels or retrieving devices. The image compression techniques offer a partial solution of this problem but there are some shortcomings to be avoided. During last years, we have tested and evaluated a set of different image compression techniques from the security point of view in a relation to a standard visual quality evaluation. The results have been part-by-part presented at several previous Carnahan conferences [1], [2], [3]. The paper presents summarized information about these results and based upon them a comprehensive discussion and conclusions are derived. Moreover some new results related to the VQ (Vector Quantization) and video coding are presented too.

Image Sensor Characteristics

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Digital Technologies 2004. Žilina: Žilinská univerzita, 2004. pp. 146-151. ISBN 80-8070-334-5.
  • Rok: 2004
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The main objective of this paper has been to use a generalized OTF, which is dedicated to the description of linear space invariant systems, for the purpose of sampled structures of image sensors, and to implement the derived results while utilizing the GUI in Matlab. The model used considers the effects of the detector photo sensitive area, sampling process, as well as other CCD specific parameters, such as the charge transfer efficiency or diffusion in order to derive the overall MTF shape. The paper also includes an experimental measurement in the real system and a comparison with the results of modeling.

Kvalitativní aspekty obrazových systémů

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Seminář o řešení projektu GA ČR 102/03/H109. Brno: VUT v Brně, FEI, Ústav radioelektroniky, 2004. pp. 39-41. ISBN 80-214-2730-2.
  • Rok: 2004
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Příspěvek stručně shrnuje postup a výsledky práce v rámci řešení projektu GA ČR 102/03/H109. První část se zabývá modelováním a měřením obrazových snímačů. V druhé části jsou uvedeny výsledky analýzy moderních metod komprese videa, zejména pak kodeku H.264 a jeho použití v dohledových bezpečnostních systémech. V závěru článku je stručně popsána možnost zvýšení účinnosti komprese videa s ohledem na pohyb očí pozorovatele a oblast ostrého vidění. Tato část je doplněna ukázkou analýzy očních pohybů pořízenou na oční klinice.

Modeling and Measurement of Image Sensors Characteristics

  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper focused to use a generalized optical transfer function for the purpose of sampled structures of image sensors and to implement the derived results while utilizing the graphical user's interface in Matlab

Modelování a měření charakteristik obrazových snímačů

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: MATLAB 2004 - Sborník příspěvků 12. ročníku konference. Praha: VŠCHT, 2004. pp. 113-122. ISBN 80-7080-550-1.
  • Rok: 2004
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Pro popis přenosových vlastností a jako objektivní měřítko kvality optických a elektrooptických systémů se používá modulační přenosová funkce MTF (Modulation Transfer Function). Tento příspěvek se zabývá použitím zobecněné MTF vzorkovaných struktur obrazových snímačů (např. CCD, CMOS, CID) za účelem implementace modelu obrazového systému s využitím grafického uživatelského rozhraní GUI v programovém prostředí Matlab. Použitý model uvažuje vliv tvaru fotocitlivé oblasti detektoru, vzorkovacího procesu, ale také dalších parametrů, jako je účinnost přenosu náboje, či difuze na průběh MTF. Měření přenosových charakteristik reálné zobrazovací soustavy - digitálního fotoaparátu - bylo provedeno s využitím univerzálního měřicího systému realizovaném jako GUI v Matlabu. Oba realizované nástroje jsou díky GUI dobře použitelné též pro výukové účely.

Optimal Sampling Structure of Image Sensors from the Point of View of Image Quality

  • Autoři: Hozman, J., Ing. Karel Fliegel, Ph.D.,
  • Publikace: Proceedings of 11th International Workshop on Systems, Signals and Image Processing ambient multimedia. Poznaň: PTETiS, 2004. pp. 371-374. ISBN 83-906074-8-4.
  • Rok: 2004
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    The paper deals with influence of the pixel shape, the pixel sensitivity profile and sampling process upon image quality. A few basic kinds of the pixel shapes have been considered. The modulation transfer function (MTF) as the most important parameter depending on sampling distance (pitch of image sensor) and sampling aperture is described as well. The main goal was to find the optimal pixel shape and pixel distribution over the image sensor area from the MTF point of view. The whole process has been modelled in MATLAB based on results of analytical computations.

Přenosové charakteristiky snímacích soustav

  • Autoři: Ing. Karel Fliegel, Ph.D.,
  • Publikace: Mikroskopie 2004. Praha: České vysoké učení technické v Praze, 2004. pp. 29-38. ISBN 80-01-03170-5.
  • Rok: 2004
  • Pracoviště: Katedra radioelektroniky
  • Anotace:
    Pro popis přenosových vlastností a jako objektivní měřítko kvality optických a elektrooptických systémů se používá modulační přenosová funkce MTF (Modulation Transfer Function). Tento příspěvek se zabývá použitím zobecněné MTF vzorkovaných struktur obrazových snímačů (např. CCD, CMOS, CID) za účelem implementace modelu obrazového systému s využitím grafického uživatelského rozhraní GUI v programovém prostředí Matlab. Použitý model uvažuje vliv tvaru fotocitlivé oblasti detektoru, vzorkovacího procesu, ale také dalších parametrů, jako je účinnost přenosu náboje, či difuze na průběh MTF. Měření přenosových charakteristik reálné zobrazovací soustavy - digitálního fotoaparátu - bylo provedeno s využitím univerzálního měřicího systému realizovaném jako GUI v Matlabu. Oba realizované nástroje jsou díky GUI dobře použitelné též pro výukové účely.

Za stránku zodpovídá: Ing. Mgr. Radovan Suk