(Charge-Coupled Device sensor) An electronic memory that records the intensity of light as a variable charge. Although mostly replaced by CMOS sensors to capture images in cameras, camcorders and scanners, CCDs are still used in astronomy, microscopy and biomedical imaging because of their excellent sensitivity during long exposures. CCDs are analog devices. Their charges equate to shades of light for monochrome images or shades of red, green and blue when used with color filters. Devices may use three CCDs, one for each of the red, green and blue colors. Why Coupled? The CCD comprises an array of imaging pixels and a matching array of storage pixels that are coupled together. After the imaging array is exposed to light, its charges are quickly transferred to the storage array. While the imaging CCDs are being exposed to the next picture, the storage CCDs from the last picture are being read out a row at a time to the analog-to-digital converters (A/D converters) that transform the voltages into binary data to be processed. Contrast with CMOS sensor. See Bayer pattern, X3, Super CCD, blooming and digital camera.