Optimization Method for Plasmonic Color Filters of High Optical Efficiency

Lee, Seonuk,Park, Junsu,Ju, Byeong-Kwon The Institute of Internet 2015 International Journal of Internet, Broadcasting an Vol.7 No.2

Various studies with regard to increasing the optical efficiency of plasmonic color filters have previously been conducted, such as mixing materials or applying diverse pattern shapes. Fundamentally, it is important to maximize the photonic crystal effect by finding the optimum periods of lattice as well as calculating the most efficient transmission area. In this study, we propose a technical method for optimizing the plasmonic color filters that have a high color gamut and luminance by analyzing the light spectrums based on the 1931 color coordinate system. Moreover, we suggest a calculation method in order to define the individual color purity of red and green and blue filters. Consequently, efficiency values are obtained independently from each color filter by evaluating the color purity and the luminance. The final result obtained from simulation are 27.6% of relative luminance and 25.3% of color gamut. The proposed optimization method is applicable to all plasmonic color filters having photonic crystal arrays.

Optimization Method for Plasmonic Color Filters of High Optical Efficiency

Seonuk Lee,Junsu Park,Byeong-Kwon Ju 한국인터넷방송통신학회 2015 International Journal of Internet, Broadcasting an Vol.7 No.2

Various studies with regard to increasing the optical efficiency of plasmonic color filters have previously been conducted, such as mixing materials or applying diverse pattern shapes. Fundamentally, it is important to maximize the photonic crystal effect by finding the optimum periods of lattice as well as calculating the most efficient transmission area. In this study, we propose a technical method for optimizing the plasmonic color filters that have a high color gamut and luminance by analyzing the light spectrums based on the 1931 color coordinate system. Moreover, we suggest a calculation method in order to define the individual color purity of red and green and blue filters. Consequently, efficiency values are obtained independently from each color filter by evaluating the color purity and the luminance. The final result obtained from simulation are 27.6% of relative luminance and 25.3% of color gamut. The proposed optimization method is applicable to all plasmonic color filters having photonic crystal arrays.

색수차 개선을 위한 효율적인 컬러 에지 퍼지 보간 방법

변오성(Oh-Sung Byun) 한국컴퓨터정보학회 2010 韓國컴퓨터情報學會論文誌 Vol.15 No.10

모바일폰이나 디지털 카메라에서 사용하는 영상 센서의 수광 소자는 한 가지 색만을 기록하는 베이어 패턴이기 때문에 각각의 화소들은 여러 개의컬러 중에서단 하나만의 컬러에 대한 화소값을얻게 된다. 잃어버린화소의 정보는 CFA(Color Filter Array)를 이용하여 그 주위의 화소에 대한 정보를 이용함으로 완전한 컬러 영상을 추론한다. 본 논문은 영상 센서의 수광 소자로부터 획득한 데이터의 평균과 각 컬러 채널 데이터 평균 사이의 관계를 유도하고, 이 관계를 이용하여 색상 보간을 위한 효율적인 에지 컬러 퍼지 보간 방법을 제안하였다. 또한 휘도 신호 채널의 보간은 컬러 노이즈를 감소하고 효율적인 보간을 위해 에지 방향에 따라 퍼지 보간을 하였다. 그리고 본 논문에서 PSNR을 이용하여 제안된 방법이 기존 방법보다 평균 2.4dB 정도 개선됨을 증명하였으며, 시각적으로 원영상의 해상도와 유사한 수준이며, 기존 알고리즘의 영상보다 색수차가 감소된 것을 실험 결과를 통하여 확인하였다. Each pixels become got pixel value for color of only one from among colors because of bayer pattern that light receiving device of image sensor which is used in HHP and digital camera writes only one color. Information of the missing pixels could infer perfect color image from using information of neighbor pixels by using CFA(Color Filter Array). In this paper, we derive relation between the average of the data from the light receiving device of image sensor and each color channel data. And by using this relation, a new efficient edge color fuzzy method for color interpolation is proposed. Also, missing luminance signal channel interpolation was fuzzy interpolation along any edges direction for reducing color noise and interpolating efficiently it. And in this paper, the proposed method has been proved improving average 2.4dB than the conventional method by using PSNR. Also, resolution of the image of the proposed method was similar to the original image by visual images, we has been verified to be decreased a chromatic aberration than image of conventional algorithms with simulation result.

분리된 컬러 필터 배열을 이용한 에지 방향 컬러 보간 방법

오현묵(Hyun Mook Oh),유두식(Du Sic Yoo),강문기(Moon Gi Kang) 大韓電子工學會 2010 電子工學會論文誌-SP (Signal processing) Vol.47 No.1

본 논문은 새로운 에지 방향 추정 방법과 영상의 영역 세분화에 기반을 둔 컬러 보간 알고리즘을 제안한다. 제안하는 에지방향 추정은 컬러 필터 배열(color filter array: CFA)의 채널 별 분리와 표본 줄임(down-sampling)을 통해 획득한 영상 사이에 존재하는 에지 방향성 상관관계를 바탕으로 이루어진다. 에지 방향성 상관관계는 영상 간의 샘플링 위치와 각 영상의 국부위치에서의 에지 방향성 사이에 존재하는 방향의 유사성을 바탕으로 정의한다. 영상의 영역을 분류함에 있어서 평탄, 에지 영역뿐만 아니라 반복되는 에지가 나타나는 패턴 에지 영역을 구분함으로써 영역을 세분화 한다. 이렇게 구분한 영역 각각에 대해 수직 혹은 수평 방향 에지를 검출하여 에지 방향에 따라 보간함으로써 오류를 최소화 하는 에지 방향성 컬러 보간이 이루어진다. 실험 결과를 통해 제안하는 방법이 기존 방법에 비해 수치적인 면과 시각적인 면에서 뛰어난 결과를 보임을 확인할 수 있으며, 제안하는 영역 세분화와 에지 방향 추정을 통해 영상의 고주파 영역에서 성능이 향상됨을 확인할 수 있다. In this paper, we present a color interpolation algorithm that uses novel edge direction estimator and region classifier. The proposed edge direction estimator accurately determines the edge direction based on the correlation between the images obtained by the channel separated and down-sampled Bayer color filter array(CFA) pattern. The correlation is defined based on the similarity between the edge direction in the local region of the image and the shifting direction of the images. Also, the region of an image is defined as the flat, the edge, and the pattern-edge regions, where the edges are appeared repeatedly. When all the pixels in the image are classified into the three different regions, each pixel is interpolated horizontally or vertically according to the estimated direction. Experimental results show that the proposed algorithm outperforms the conventional edge-directed methods on objective and subjective criteria.

A New N-time Systolic Array Architecture for the Vector Median Filter

양영일,Yang, Yeong-Yil The Korea Institute of Convergence Signal Processi 2007 융합신호처리학회 논문지 (JISPS) Vol.8 No.4

본 논문에서는 벡터 미디언 값을 계산하기 위한 시스톨릭 어레이 구조의 벡터 미디언 필터 구조를 제안하였다. 컬러영상처리에서 벡터 신호는 빨강, 녹색 파랑의 3개의 요소로 이루어져 있다. 벡터 미디어 필터는 빨강, 녹색 파랑 요소로 이루어진 벡터 신호들 중에서 벡터 신호를 크기 순서대로 나열하였을 때 가운데 값을 갖는 벡터 신호를 구하는 필터로, 컬러 영상처리에서 기본적으로 많이 사용되는 필터이다. 벡터 신호가 N 개가 있을 때, 지금 까지 제안된 구조에서는(3N+1) 클럭이 필요하나, 제안된 구조에서는 (N+2) 클럭이 소요된다. 그리고 기존의 구조에서는 N 개의 입력 벡터 신호는 미디언 필터에 병렬로 입력되어야 하나 제안된 구조에서는 입력 신호는 직렬로 인가된다. FPGA를 사용하여 구현하였다. In this paper, we propose the systolic array architecture for the vector median filter. In the color image processing, the vector signal (i.e. the color) consists of three elements, red, green and blue. The vector median filter is very effective to utilize the correlation among red, green and blue elements. The computational complexity of the proposed architecture for computing the vector median of N vector signals is (N+2) clock periods compared to the (3N+1) clock periods in the previous method. In addition to, the input vector signals can be loaded in serial in the proposed architecture. In the previous method, N input vector signals should be loaded to the vector median filter in parallel at the first clock. The proposed architecture is implemented with FPGA.

Covered Microlens Structure for Quad Color Filter Array of CMOS Image Sensor

황제혁,김윤경 한국광학회 2023 Current Optics and Photonics Vol.7 No.5

The pixel size in high-resolution complementary metal-oxide-semiconductor (CMOS) image sensors continues to shrink due to chip size limitations. However, the pixel pitch’s miniaturization causes deterioration of optical performance. As one solution, a quad color filter (CF) array with pixel binning has been developed to enhance sensitivity. For high sensitivity, the microlens structure also needs to be optimized as the CF arrays change. In this paper, the covered microlens, which consist of four microlenses covered by one large microlens, are proposed for the quad CF array in the backside illumination pixel structure. To evaluate the optical performance, the suggested microlens structure was simulated from 0.5μm to 1.0 μm pixels at the center and edge of the sensors. Moreover, all pixel structures were comparedwith and without in-pixel deep trench isolation (DTI), which works to distribute incident light uniformly into each photodiode. The suggested structure was evaluated with an optical simulation using the finitedifference time-domain method for numerical analysis of the optical characteristics. Compared to the conventional microlens, the suggested microlens show 29.1% and 33.9% maximum enhancement of sensitivity at the center and edge of the sensor, respectively. Therefore, the covered microlens demonstrated the highly sensitive image sensor with a quad CF array.

Color-Filter 및 Microlens를 포함한 CMOS Image Sensor의 Optical Stack 구조 별 Pixel FPN 특성 및 원인 분류

최운일,이희덕,Choi, Woonil,Lee, Hi-Deok 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.11

FPN (fixed-pattern-noise) mainly comes from the device or pattern mismatches in pixel and color filter, pixel photodiode leakage in CMOS image sensor. In this paper, optical stack module related pixel FPN was investigated and the classification of pixel FPN contribution with the individual optical module process was presented. The methodology and procedure would be helpful in reducing the greater pixel FPN and distinguishing the complex FPN sources with respect to various noise factors.

Mobility Support for Full-Duplex Multiuser Bidirectional VLC Networks

Sewaiwar, Atul,Tiwari, Samrat Vikramaditya,Yeon Ho Chung IEEE 2015 IEEE photonics journal Vol.7 No.6

<P>In this paper, a novel and unique mobility support scheme for a color-clustered (CC) full-duplex multiuser (MU) bidirectional visible light communication (VLC) network is presented. Mobility is classified into two categories: intercluster and intracluster. In the proposed scheme, the mobility support is efficiently provided using a color filter array (CFA) at the downlink receiver. This CFA gives rise to receiver diversity in the form of selection combining yielding performance improvement. Simulations are conducted in terms of communication delay and frame loss rate relative to user speed and distance. In addition, the bit error rate (BER) performance and the data rate are analyzed in the CC MU VLC network. It is demonstrated that the proposed CFA and receiver diversity based mobility scheme in the CC MU VLC network offers superior performance in terms of BER and data rate in indoor environments.</P>

육각형 구조의 베이어 컬러 필터 배열에 대한 디모자익킹

이경미(Kyungme Lee),유훈(Hoon Yoo) 대한전기학회 2014 전기학회논문지 Vol.63 No.10

This paper describes a demosaicking method for hexagonally-structured color filter array. Demosaicking is essential to acquire color images using color filter array (CFA) in single sensor imaging. Thus, CFA patterns have been discussed in order to improve image quality in single sensor imaging after the Bayer pattern are introduced. Advancements in imaging sensor technology recently introduce a hexagonal CFA pattern. The hexagonal CFA can be considered to be a 45-degree rotational version of the Bayer pattern, thus demosaicking can be implemented by an existing method with backward and forward 45-degree rotations. However, this approach requires heavy computing power and memory in image sensing devices because of the image rotations. To overcome this problem, we proposes a demosaicking method for a hexagonal Bayer CFA without rotations. In addition, we introduce a weighting parameter in our demosaicking method to improve image quality and to unifying exiting method with our method. Experimental results indicate that the proposed method is superior to conventional methods in terms of PSNR. In addition, some optimized values for the weighting parameter are provided experimentally.

고감도 컬러 영상 획득을 위한 W 채널을 포함하는 컬러 필터 배열에서의 확산 알고리즘 기반 색 보간 방법

오바울,이석호,김한솔,강문기 대한전자공학회 2018 전자공학회논문지 Vol.55 No.2

최근 감도가 높은 W 픽셀을 추가한 RGBW 컬러 필터 배열(CFA)에 대한 연구가 진행되어 왔다. W 픽셀은 컬러 필터 배열 내의 다른 컬러 픽셀들보다 감도가 높아 특히 저조도 환경에서 더 나은 신호 대 잡음비 특성을 보인다. 본 논문에서는 W 채널의 고감도 특성을 최대화 할 수 있는 새로운 RGBW CFA를 제안하였고 확산 알고리즘을 기반으로 한 새로운 색 보간 방법을 제안하였다. 제안된 RGBW 패턴은 W 픽셀의 고감도 특성을 최대화하기 위해 센서 면적의 50% 이상을 W 픽셀로 구성하였고 적은 숫자의 RGB 픽셀이 분포하도록 설계되었다. 이러한 컬러 필터 배열에 확산 기법을 응용하면 매우 적은 숫자의 RGB 픽셀들만을 이용하여 W 채널 수준의 SNR 특성을 갖는 컬러 영상을 획득할 수 있다. 실험 결과를 통해 제안된 CFA에서 획득한 컬러 영상은 저조도 환경에서 기존의 방법에서 얻은 영상보다 더 높은 SNR 값을 갖고 기존 방법에서는 감지할 수 없었던 영상 내 중요한 정보를 감지하는 것을 확인 할 수 있다. Up to the present, some of RGBW color filter arrays (CFAs) which have highly sensitive W pixels have been developed. As the W pixels are more sensitive than other color pixels in the filter array, they have better SNR characteristics, especially, in low light conditions. We propose a new RGBW color filter array that maximize the highly sensitive characteristics of W channel, and a new color interpolation algorithm based on the diffusion technique. In order to maximize the high SNR characteristics of W channel, the proposed RGBW CFA is designed to contain a larger number of W pixels and a smaller number of RGB pixels than conventional RGBW CFAs. By applying the diffusion algorithm to such a color filter array, a color image which has the high SNR characteristics of the W channel can be obtained using only a very small number of RGB pixels. Experimental results show that the reconstructed color image from the proposed CFA has a high SNR value, and many important information which cannot be identified in color images reconstructed with conventional CFAs can be identified in the images reconstructed with the proposed method.