CCDs for seeing

Nov. 1, 2009
Machine vision begins at the sensing device, and the original and most prevalent design the CCD camera or charge-coupled device recently earned its inventors

Machine vision begins at the sensing device, and the original and most prevalent design — the CCD camera or charge-coupled device — recently earned its inventors Willard S. Boyle and George E. Smith the 2009 Nobel Prize in physics. The wafer, often with metal oxide semiconductor capacitors, is an electronic component segmented into a grid of individual light-sensitive cells or pixels called photodetectors.

The photoelectric effect

CCD pixels sense incoming light by the photoelectric effect, the tendency of some materials to release electrons when hit with light photons. When light rains on the pixels, electrons (fenced in by nonconductive boundaries) accumulate in them.

CCDs process data row by row. A sequence of clock signals shifts charges across the chip towards an amplifying register that measures charge. Like a bucket brigade, a row of information is transferred to the readout register while following rows are shifted closer. Then electric charges are released and the register emptied for the next row in line, until all information is read.

This 1/6-in. CS9501 CCD camera is one of the world's smallest. Its three-gram head is a mere 7 mm across. Suitable for robotic arms, it captures 470-TVL horizontal resolution (768 × 494 pixels NTSC) or full-frame images. Visit Toshiba Teli America Inc. at www.toshiba-teli.com.

Smith and Boyle will speak at the Nobel Physics Lectures on December 8. To listen to the conversations in which Laureates are first notified of their honor, and for more information, visit http://nobelprize.org.

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