A novel color filter array with 75% transparent elements
Gang Luo · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2007
Conventional RGB color filter array (CFA) in single-chip color cameras greatly reduce light intensity, and therefore limits the ISO speed of cameras. A novel CFA and an algorithm of forming color images are proposed. 75% of the CFA are transparent elements, and the remaining 25% are repeated color filter blocks. A compact arrangement of color filter elements in each block helps to reduce color artifacts. Such an arrangement features a higher sampling rate of luminance and a lower sampling rate of chrominance. Black-and-white images (BI) with high resolution can be acquired from the transparent elements, and color images (CI) with low resolution from the color filter blocks. To generate output color images (OI), the CI in RGB format is transformed into CIE Lab space, and the luminance components are replaced with the high-resolution BI. Based on a principle compatible to JPEG format, the visual quality of OI is satisfactory. Simulation was conducted using raw images acquired with a Canon 20D camera. Results show the potential of the CFA in making digital cameras with high ISO speed. Applications can be security day/night cameras and cell phone cameras that are able to capture images with low noise under dim light levels.