Transmited light micrograph of a CCD chip: a charge-coupled device of a Starblitz SD220 digital camera (2 Mpx, color). Made of epitaxial layers of silicon, this image sensor device is a 2-D array of metal oxide semiconductor (MOS) capacitors. The CCD receives light (photons) as input, and their interaction with silicon atoms is stored as an electrical charge and converted into an electronic output signal. Each individual photodiode, or pixel, consists of three transparent polysilicon gates over a buried channel of doped photosensitive silicon which generates a charge through a photoelectric effect. Said charge is sequentially moved from one gate to the next (coupling) to allow this charge to be read out of the array to be digitized. Its high quantum efficiency is improved by using one or more microlenses on each pixel. Field of view size: 14.55 x 21.83 mm (0.573 x 0.860 in)