The Experts below are selected from a list of 22590 Experts worldwide ranked by ideXlab platform
Moon Gi Kang - One of the best experts on this subject based on the ideXlab platform.
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demosaicing of rgbw Color Filter array based on rank minimization with Colorization constraint
Sensors, 2020Co-Authors: Han Sol Kim, Sukho Lee, Moon Gi KangAbstract:Recently, the white (w) channel has been incorporated in various forms into Color Filter arrays (CFAs). The advantage of using theWchannel is thatWpixels have less noise than red (R), green (G), or blue (B) (RGB) pixels; therefore, under low-light conditions, pixels with high fidelity can be obtained. However, RGBW CFAs normally suffer from spatial resolution degradation due to a smaller number of Color pixels than in RGB CFAs. Therefore, even though the reconstructed Colors have higher sensitivity, which results in larger Color Peak Signal-to-Noise Ratio (CPSNR) values, there are some Color aliasing artifacts due to a low resolution. In this paper, we propose a rank minimization-based Color interpolation method with a Colorization constraint for the RGBW format with a large number ofWpixels. The rank minimization can achieve a broad interpolation and preserve the structure in the image, and it thereby eliminates the Color artifacts. However, the Colors fade from this global process. Therefore, we further incorporate a Colorization constraint into the rank minimization process for the better reproduction of the Colors. The experimental results show that the images can be reconstructed well, even from noisy pattern images obtained under low-light conditions.
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Sensitivity and Resolution Improvement in RGBW Color Filter Array Sensor
MDPI AG, 2018Co-Authors: Seunghoon Jee, Ki Sun Song, Moon Gi KangAbstract:Recently, several red-green-blue-white (RGBW) Color Filter arrays (CFAs), which include highly sensitive W pixels, have been proposed. However, RGBW CFA patterns suffer from spatial resolution degradation owing to the sensor composition having more Color components than the Bayer CFA pattern. RGBW CFA demosaicing methods reconstruct resolution using the correlation between white (W) pixels and pixels of other Colors, which does not improve the red-green-blue (RGB) channel sensitivity to the W channel level. In this paper, we thus propose a demosaiced image post-processing method to improve the RGBW CFA sensitivity and resolution. The proposed method decomposes texture components containing image noise and resolution information. The RGB channel sensitivity and resolution are improved through updating the W channel texture component with those of RGB channels. For this process, a cross multilateral Filter (CMF) is proposed. It decomposes the smoothness component from the texture component using Color difference information and distinguishes Color components through that information. Moreover, it decomposes texture components, luminance noise, Color noise, and Color aliasing artifacts from the demosaiced images. Finally, by updating the texture of the RGB channels with the W channel texture components, the proposed algorithm improves the sensitivity and resolution. Results show that the proposed method is effective, while maintaining W pixel resolution characteristics and improving sensitivity from the signal-to-noise ratio value by approximately 4.5 dB
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Colorization based rgb white Color interpolation using Color Filter array with randomly sampled pattern
Sensors, 2017Co-Authors: Sukho Lee, Moon Gi KangAbstract:Recently, several RGB-White (RGBW) Color Filter arrays (CFAs) have been proposed, which have extra white (W) pixels in the Filter array that are highly sensitive. Due to the high sensitivity, the W pixels have better SNR (Signal to Noise Ratio) characteristics than other Color pixels in the Filter array, especially, in low light conditions. However, most of the RGBW CFAs are designed so that the acquired RGBW pattern image can be converted into the conventional Bayer pattern image, which is then again converted into the final Color image by using conventional demosaicing methods, i.e., Color interpolation techniques. In this paper, we propose a new RGBW Color Filter array based on a totally different Color interpolation technique, the Colorization algorithm. The Colorization algorithm was initially proposed for Colorizing a gray image into a Color image using a small number of Color seeds. Here, we adopt this algorithm as a Color interpolation technique, so that the RGBW Color Filter array can be designed with a very large number of W pixels to make the most of the highly sensitive characteristics of the W channel. The resulting RGBW Color Filter array has a pattern with a large proportion of W pixels, while the small-numbered RGB pixels are randomly distributed over the array. The Colorization algorithm makes it possible to reconstruct the Colors from such a small number of RGB values. Due to the large proportion of W pixels, the reconstructed Color image has a high SNR value, especially higher than those of conventional CFAs in low light condition. Experimental results show that many important information which are not perceived in Color images reconstructed with conventional CFAs are perceived in the images reconstructed with the proposed method.
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Color interpolation algorithm for an rwb Color Filter array including double exposed white channel
EURASIP Journal on Advances in Signal Processing, 2016Co-Authors: Ki Sun Song, Jonghyun Kim, Chul Hee Park, Moon Gi KangAbstract:In this paper, we propose a Color interpolation algorithm for a red-white-blue (RWB) Color Filter array (CFA) that uses a double exposed white channel instead of a single exposed green (G) channel. The double-exposed RWB CFA pattern, which captures two white channels at different exposure times simultaneously, improves the sensitivity and provides a solution for the rapid saturation problem of W channel although spatial resolution is degraded due to the lack of a suitable Color interpolation algorithm. The proposed algorithm is designed and optimized for the double-exposed RWB CFA pattern. Two white channels are interpolated by using directional Color difference information. The red and blue channels are interpolated by applying a guided Filter that uses the interpolated white channel as a guided value. The proposed method resolves spatial resolution degradation, particularly in the horizontal direction, which is a challenging problem in the double-exposed RWB CFA pattern. Experimental results demonstrate that the proposed algorithm outperforms other Color interpolation methods in terms of both objective and subjective criteria.
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intermediate Color interpolation for Color Filter array containing the white channel
electronic imaging, 2015Co-Authors: Jonghyun Kim, Sang Wook Park, Moon Gi KangAbstract:Recently, a Color Filter array sensor with the white channel has been developed. This Color Filter array differs from the Bayer CFA, which is composed of red, green and blue channels. Since the white channel shows high sensitivity through broad spectral bands and a high light sensitivity, it presents many advantages. However, various Color interpolation method for the Bayer CFA cannot be utilized for CFA pattern that contains the white channel directly. In this paper, a method for generating a quincuncial pattern is proposed for the CFA pattern. By generating an intermediate quincuncial pattern, various Color interpolation algorithms can be applied to it. Experimental results are shown in comparison with the conventional method in terms of PSNR measurements.
Andy Yingguey Fuh - One of the best experts on this subject based on the ideXlab platform.
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designs of high Color purity rgb Color Filter for liquid crystal displays applications using fabry perot etalons
IEEE\ OSA Journal of Display Technology, 2012Co-Authors: Chengkai Liu, Koting Cheng, Andy Yingguey FuhAbstract:Two designs of high Color purity RGB Color Filter (RGB-CF) using Fabry-Perot etalon were proposed. First, various transmission spectra for corresponding pixel arrays were achieved by optimizing the orientation of fixed polymerized liquid crystal polymers with high birefringence. The designed high Color purity RGB-CF is believed to have potential for display applications. Second, three primary transmissive peaks for each pixel were achieved with the optimized air gap. Compensated CFs were adopted to enhance Color purity by absorbing undesirable transmissive light. The second design is to overcome the limitation of the cell gap in the first design. Additionally, two approaches to improve light utilization efficiency were discussed.
Y Altunbasak - One of the best experts on this subject based on the ideXlab platform.
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multiscale gradients based Color Filter array interpolation
IEEE Transactions on Image Processing, 2013Co-Authors: Ibrahim Pekkucuksen, Y AltunbasakAbstract:Single sensor digital cameras use Color Filter arrays to capture a subset of the Color data at each pixel coordinate. Demosaicing or Color Filter array (CFA) interpolation is the process of estimating the missing Color samples to reconstruct a full Color image. In this paper, we propose a demosaicing method that uses multiscale Color gradients to adaptively combine Color difference estimates from different directions. The proposed solution does not require any thresholds since it does not make any hard decisions, and it is noniterative. Although most suitable for the Bayer CFA pattern, the method can be extended to other mosaic patterns. To demonstrate this, we describe its application to the Lukac CFA pattern. Experimental results show that it outperforms other available demosaicing methods by a clear margin in terms of CPSNR and S-CIELAB measures for both mosaic patterns.
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edge strength Filter based Color Filter array interpolation
IEEE Transactions on Image Processing, 2012Co-Authors: Ibrahim Pekkucuksen, Y AltunbasakAbstract:For economic reasons, most digital cameras use Color Filter arrays instead of beam splitters to capture image data. As a result of this, only one of the required three Color samples becomes available at each pixel location and the other two need to be interpolated. This process is called Color Filter Array (CFA) interpolation or demosaicing. Many demosaicing algorithms have been introduced over the years to improve subjective and objective interpolation quality. We propose an orientation-free edge strength Filter and apply it to the demosaicing problem. Edge strength Filter output is utilized both to improve the initial green channel interpolation and to apply the constant Color difference rule adaptively. This simple edge directed method yields visually pleasing results with high CPSNR.
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edge oriented directional Color Filter array interpolation
International Conference on Acoustics Speech and Signal Processing, 2011Co-Authors: Ibrahim Pekkucuksen, Y AltunbasakAbstract:Most of the current digital cameras feature a single sensor design which limits the number of channels recorded at each pixel location to one. However, a Color image is represented with three channels for each pixel. Color Filter Array (CFA) interpolation is the process of generating a full three channel Color image from a single channel mosaicked input. We propose a simple edge strength Filter to interpolate the missing Color values adaptively. While the Filter is readily applicable to the Bayer mosaic pattern, we argue that the same idea could be extended to other mosaic patterns and describe its application to the Lukac mosaic pattern. The proposed solution outperforms other available algorithms for the Lukac pattern in terms of both objective and subjective comparison.
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gradient based threshold free Color Filter array interpolation
International Conference on Image Processing, 2010Co-Authors: Ibrahim Pekkucuksen, Y AltunbasakAbstract:Color Filter Array (CFA) interpolation is an integral part of image processing pipeline for single sensor digital cameras. Many CFA algorithms have been proposed over the years to improve resulting image quality. One such algorithm is the highly successful Directional Linear Minimum Mean-Square Error Estimation (DLMMSE) method. We make several observations on this algorithm and propose a new method to address those points. The proposed method yields visually pleasing results and outperforms all CFA interpolation algorithms that are included in a recent survey paper in terms of PSNR.
Joonki Paik - One of the best experts on this subject based on the ideXlab platform.
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single camera based full depth map estimation using Color shifting property of a multiple Color Filter aperture
International Conference on Acoustics Speech and Signal Processing, 2012Co-Authors: Seungwon Lee, Junghyun Lee, M H Hayes, Aggelos K Katsaggelos, Joonki PaikAbstract:A multiple Color-Filter aperture (MCA) camera can provide depth information as well as Color and intensity in the single-camera framework, where the MCA generates misalignment between Color channels depending on the distance of a region-of-interest. In this paper, we present a single camera-based estimation of the full depth map using the Color shifting property of the MCA. For estimating the Color shifting vectors (CSVs) among red, green, and blue Color channels, edges are extracted at each Color channel. At the edge, we estimate CSVs using normalized cross correlation combined with Color shifting mask map. A full depth map is then generated by depth interpolation using the matting Laplacian method from sparsely estimated CSVs at an edge location. Experimental results show that the proposed method can not only estimate the full depth map but also correct the misaligned Color image to generate photorealistic Color images using a single camera equipped with MCA.
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simultaneous object tracking and depth estimation using Color shifting property of a multiple Color Filter aperture camera
International Conference on Acoustics Speech and Signal Processing, 2011Co-Authors: Seungwon Lee, Jinhee Lee, Joonki PaikAbstract:A multiple Color-Filter aperture (MCA) camera can provide depth information as well as Color and intensity in the single-camera framework, where the MCA generates misalignment between Color channels depending on the distance of a region-of-interest. In this paper, we present a simultaneous object tracking and depth estimation approach based on the Color shifting property of an MCA camera. An object region is first extracted by using Markov Chain Monte Carlo (MCMC) sampling-based particle Filter. The extracted object's region has Color misalignment among RGB planes depending on the distance of the object. We estimate Color shifting vectors (CSVs) between green-and-red (G-R) and green-and-blue (G-B) channels using a simplified elastic registration algorithm. Using the Color shifting property of the MCA camera, the depth of the object's region is estimated from CSVs. From experimental results, we can show the MCA camera-based surveillance system can estimate depth information as well as track object.
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Color shift model based image enhancement for digital multifocusing based on a multiple Color Filter aperture camera
IEEE Transactions on Consumer Electronics, 2010Co-Authors: Eunsung Lee, Wonseok Kang, Sangjin Kim, Joonki PaikAbstract:In this paper, we present a novel image enhancement approach using a Color shift model-based multiple Color-Filter aperture (MCA) camera for digital multifocusing. The proposed image enhancement algorithm consists of three steps; (i) cluster-based region-of-interest (ROI) estimation, (ii) image registration using phase correlation matching (PCM) and fusion, and (iii) image enhancement using spatially adaptive noise smoothing based on the alpha map. The image acquired by the MCA configuration contains Color misalignment, which provides additional depth information of objects at different distances. This Color misalignment can also provide additional information for blur estimation. The proposed cluster-based image segmentation method can effectively classify ROIs according to the distance from the camera. The segmented regions are aligned by using PCM, and they are fused to generate an in-focused image. For further enhancement of the Color-registered image, we use spatially adaptive noise smoothing based on the alpha map. Experimental results show the proposed image enhancement method can significantly enhance the visual quality of the MCA output image, and can be fully or partially incorporated into multifocusing or extended depth of field (EDoF) systems in the form of the finite impulse response (FIR) Filter structure.
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real time image restoration for digital multifocusing in a multiple Color Filter aperture camera
Optical Engineering, 2010Co-Authors: Vivek Maik, Joonki PaikAbstract:A multiple Color-Filter aperture (MCA) can provide a single camera with depth information and multifocusing. However, the original version of the MCA system exhibits inherent limitations such as manual, empirical tuning parameters for the Color channel registration and fusion (CRF) process. Furthermore, a CRF output image still contains undesired out-of-focus blur because of the finite-sized apertures and the lateral displacement of each Color-Filter aperture, which results in low exposure, Color mixing, deviation of Color convergence, and divergence of light rays. For overcoming these problems, we present a real-time image processing solution for digital multifocusing in a MCA system.
Chengkai Liu - One of the best experts on this subject based on the ideXlab platform.
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designs of high Color purity rgb Color Filter for liquid crystal displays applications using fabry perot etalons
IEEE\ OSA Journal of Display Technology, 2012Co-Authors: Chengkai Liu, Koting Cheng, Andy Yingguey FuhAbstract:Two designs of high Color purity RGB Color Filter (RGB-CF) using Fabry-Perot etalon were proposed. First, various transmission spectra for corresponding pixel arrays were achieved by optimizing the orientation of fixed polymerized liquid crystal polymers with high birefringence. The designed high Color purity RGB-CF is believed to have potential for display applications. Second, three primary transmissive peaks for each pixel were achieved with the optimized air gap. Compensated CFs were adopted to enhance Color purity by absorbing undesirable transmissive light. The second design is to overcome the limitation of the cell gap in the first design. Additionally, two approaches to improve light utilization efficiency were discussed.
