= Charge-coupled device
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= CCD
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A charge-coupled device stores photoelectrons in potential wells and transfers the charge through clocked stages to an output amplifier. The transfer differs from independently addressed pixels in a <hybrid infrared detector>.
In an imaging <charge-coupled device>, absorbed <photons> produce mobile <charge carriers> in a <semiconductor>; collection stores an <electric charge> packet associated with each <optical detector pixel>. Closely spaced <MOS capacitors> allow applied <electric potential differences> to move the packet from site to site. <Willard Sterling Boyle> and <George Elwood Smith> described storage, transfer and detection as distinct operations, including imaging as one application.<Charge Coupled Semiconductor Devices by Willard Sterling Boyle and George Elwood Smith>[Charge Coupled Semiconductor Devices, April 1970, p. 587, abstract and opening device-concept paragraphs; scanned original hosted by VTDA]{ref}
The useful architectural trick is that many <optical detector pixels> can send their <electric charge> to a shared output <electronic amplifier>. This makes repeatable conversion possible but makes fidelity depend on every transfer along the route. An <active-pixel sensor> made with <CMOS> technology instead uses circuitry at pixels to convert or buffer their signal and select it for readout; independent pixel addressing does not require transporting each packet through the whole image. This compares readout architectures, not whether either technology can use a <photodiode>.<CMOS Sensors Enable Phone Cameras, HD Video by National Aeronautics and Space Administration>[NASA Spinoff, 2017, NASA Technology, pixel-to-pixel transfer and amplification at individual pixels]{ref}
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