Charge-Coupled Device (CCD)

A charge-coupled device (CCD) is a camera that converts visible-light images into digital signals. Some CCDs also work with infrared (IR) or ultraviolet (UV).Common digital cameras work on a principle similar to that of the CCD. The image focused on the retina of the human eye, or on the film of a conventional camera, is an analog image. It can have infinitely many configurations, and infinitely many variations in hue, brightness, contrast, and saturation. A digital computer, however, needs a digital image to make sense of, and enhance, what it “sees.” Binary digital signals have only two possible states: high and low, or 1 and 0. It is possible to get an excellent approximation of an analog image in the form of high and low digital signals. This allows a computer program to process the image, bringing out details and features that would otherwise be impossible to detect. The illustration is a simplified block diagram of a CCD. The image falls on a matrix containing thousands or millions of tiny sensors. Each sensor produces one pixel (picture element). The computer (not shown) can employ all the tricks characteristic of any good graphics program. In addition to rendering high-contrast or false-color images, the CCD and computer together can detect and resolve images much fainter than is possible with conventional camera film or more primitive types of video cameras. This makes the CCD useful in robots that must employ night vision.