CMOS And CCD — Small Differences Along The Way From Light To A Signal

Historically, CCD (charged coupled device) sensors have existed much longer than CMOS sensors, that is to say, for more than 40 years. Due to constant improvement and optimization over the years, CCD sensors today stand for excellent image quality. In 2009, the American scientists Willard Boyle and George E. Smith were awarded the Nobel Prize for Physics for the invention of the CCD sensor. Originally developed in 1969 for the storage of data, the potential of the charge coupled device as a light sensitive apparatus was soon realized. By 1975, the first sensors with a resolution sufficient for television cameras appeared. However, it took more than 10 years before the process technology was mature enough to begin production of CMOS (complementary metal oxide semiconductor) sensors. In the mid-nineties, the first commercially successful CMOS sensors appeared on the market.

CMOS sensors are based on the same physical principles as CCD sensors. They convert incoming photons into electrons by means of a photo effect. As a result of their sensor structure, the maximum sensitivity of CMOS sensors is in the red spectral region (650 – 700 nm). CCD sensors, not least because of the numerous innovations during their longer technological history, have a maximum at about 550 nm - exactly where the human eye is most sensitive.