image by TCav (Image rights)
The light-sensitive silicon material in a digital sensor responds to all wavelengths (colors) of visible light. In order to represent the color of a scene being photographed, some method of separating the red, blue, and green primaries must be introduced, to achieve natural color reproduction. The method almost universally used (as of 2012) is for the sensor to include a mosaic of tiny color filters over individual pixels, typically in the 2×2 grid pattern developed by Kodak engineer Bryce Bayer and patented in 1976. In this arrangement, there are twice as many green-filtered pixels as red- or blue-filtered ones, corresponding to the greater sensitivity of the human eye to yellow-green light. After the brightness values of the individual filtered pixels are recorded, a software demosaicing process interpolates R, G, and B values for all the pixels in the sensor.
Alternate color filter array arrangements are possible, and have been used, e.g. by Fujifilm; in fact Kodak itself developed sensors with some unfiltered ("clear") pixels in the array, to permit greater overall sensitivity. Foveon sensors use a different technology, able to discriminate separate RGB values at each pixel location.
Bryce Bayer died 13 November 2012, having retired from Kodak in the 1990s.