Active Pixel Sensors (CMOS Sensor)

CMOS (Complimentary Metal Oxide Semiconductor) sensors or Active Pixel sensors were first discussed in length in a paper from Dr. Eric Fossum, a scientist at NASA’s Jet Propulsion Laboratory, in 1992. 1993 through to 1995, JPL developed much of the technology which would be implemented into the CMOS sensor. Fossum and other members of the JPL co-founded Photobit Corporation in 1995 to commercialize the technologies they had developed. In 2001, Micron Technology acquired Photobit and used its extensive knowledge of CMOS wafer manufacturing to enhance the development further.
CMOS sensors derive their name from the way they are manufactured. They are cut from a CMOS wafer which is cheaper to produce then a CCD wafer, provides less power consumption, and also allow for more involved circuitry along side of the photosite array. Each photosite in the CMOS sensor has three or more transistors which has its benefits and its draw backs. The transistors allow for processing to be done right at the photosite, and each pixel/photosite can be accessed independently. Because the transistors occupy space on the array, some of the incoming light hits the transistors and not the photosites, which leads to picture noise. CMOS sensors also function at a very low gain which may contribute to noise.