Sensitivity and Resolution Improvement in RGBW Color Filter Array Sensor

Abstract

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.

High-Sensitivity Pixels with a Quad-WRGB Color Filter and Spatial Deep-Trench Isolation

“…The low-illumination signal-to-noise ratios of the luminance signal are improved by increasing the white CF area [11]. Moreover, the color reproducibility of the WRGB pattern is comparable with the Bayer pattern [11,12]. According to this research, the WRGB CFA demosaicing result has a similar spatial resolution, color reproduction, and better color aliasing artifact levels compared to the Bayer CFA demosaicing result by the post-processing method.…”

Deep Sensing for Compressive Video Acquisition

“…The Bayer filter [1] is often used for this color filter, and it consists of red (R), green (G), and blue (B) filters (as shown in Figure 1a). Because the RGB filter cuts out a lot of light, filters such as RGB-white (W) and cyan (C), magenta (M), and yellow (Y) filters have also been proposed to increase sensitivity [1,22,23]. When a uniform CFA is used, the spatial resolution of each color is decreased to 1/c (c is the number of color channels).…”

Silicon Nanowire Phototransistor Arrays for CMOS Image Sensor Applications

“…The prevailing image sensor technologies on the market employ a color filter array (CFA) that incorporates organic dye color filters placed over silicon (Si) photodiode arrays [ 4 ]. However, the reduction in sensitivity in CFAs is inevitable with attempts to miniaturize pixel sizes, a trend driven by the pursuit of enhanced spatial resolution [ 5 , 6 , 7 ]. In addition, organic dye filters, essential to the CFA design, manifest vulnerabilities under elevated temperatures and exposure to ultraviolet radiation [ 3 , 8 , 9 , 10 , 11 ].…”