A Color CMOS Imager With 4 $\times$ 4 White-RGB Color Filter Array for Increased Low-Illumination Signal-to-Noise Ratio

A color CMOS image sensor with the 4 times 4 White-RGB color filter array (CFA) including 50% white pixels has been developed. A transparent layer has been fabricated on the white pixel to realize over 95% transmission for visible light with wavelengths of 400-700 nm. Pixel pitch and number of the pixels were 3.3 mum and 2 million, respectively. With the simple and low-noise color separation process, low-illumination signal-to-noise ratios of luminance signal have been increased by 6 dB, compared with those of the Bayer pattern. Moreover, by locating the pixels so that every color components can be detected in every column and line, color artifacts at the edge were suppressed. The edge detection process became unnecessary and the process time was reduced by 70%. The new CFA has the potential to significantly increase the sensitivity of CMOS/CCD image sensors.