The Foveon X3 sensor is a digital camera image sensor designed by Foveon, Inc., (now part of Sigma Corporation) and manufactured by Dongbu Electronics.[1] It uses an array of photosites that consist of three vertically stacked photodiodes. Each of the three stacked photodiodes has a different spectral sensitivity, allowing it to respond differently to different wavelengths.[2] The signals from the three photodiodes are then processed as additive color data that are transformed to a standard RGB color space. In the late 1970s, a similar color sensor having three stacked photo detectors at each pixel location, with different spectral responses due to the differential absorption of light by the semiconductor, had been developed and patented by Kodak.[3]
The X3 sensor technology was first deployed in 2002 in the Sigma SD9 DSLR camera, and subsequently in the SD10, SD14, SD15, SD1 (including SD1 Merrill), the original mirrorless compact Sigma DP1 and Sigma DP2 in 2008 and 2009 respectively, the Sigma dp2 Quattro series from 2014, and the Sigma SD Quattro series from 2016. The development of the Foveon X3 technology is the subject of the 2005 book The Silicon Eye by George Gilder.