CCD
in full
charge-coupled deviceSemiconductor device in which the individual semiconductor components are connected so that the electrical charge at the output of one device provides the input to the next device. Because they can store electrical charges, CCDs can be used as memory devices, but they are slower than RAMs. CCDs are sensitive to light, and are therefore used as the light-detecting components in video and digital cameras and in optical scanners.
CCD
(1) (Consumer Computing Device) A low-cost consumer-oriented product that contains a computer, such as a PDA, Internet appliance or specialized mobile device.
(2) (Charge-Coupled Device) An electronic memory that records the intensity of light as a variable charge. Widely used in still cameras, camcorders and scanners to capture images, 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 It's Coupled
The "coupled" in the name is because the CCD is comprised of 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 charges into binary data to be processed. Contrast with CMOS image sensor. See Bayer pattern, X3, Super CCD, blooming and digital camera.
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| Charge-Coupling Methods |
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| The storage CCDs are either a separate array (frame transfer) or individual photosites (interline transfer) coupled to each imaging photosite. The charges can be transferred faster with the interline method because each storage component is closer to its imaging counterpart. |
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| CCDs Record Light |
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| In a camera, CCDs take the place of film. They are exposed to light, recording the intensities, or shades, of light as variable charges. In the digital camera above, the variable, analog charges in the CCD are converted to binary data by analog-to-digital converter chips. |
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| CCDs Are Very Sensitive |
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| This CCD from Jet Propulsion Labs is used in astronomy. Sensing the output of telescopes, it detects ultraviolet light from distant planets. (Image courtesy of JPL's Microdevices Laboratory; Robert M. Brown, photographer) |