Book Analog Interfacing to Embedded Microprocessors
Linear CCDs
Linear (or line-scan) CCDs have a single line of pixels. They are used in appli-
cations where the object to be scanned is moving. The CCD scans a single row
of pixels. When the target moves one pixel’s width, the CCD scans another
row of pixels. By assembling the rows of pixels, an image of the object may
be built in memory. Typical applications include any kind of imaging that
involves moving objects along a track, such as packages on a conveyer belt or
documents moving down a transport. Figure 3.17 illustrates this process. To
keep this figure simple, an array of only 24 elements is shown; a real array
typically has 512 to 4096 elements.
Linear CCDs can also be used where the object is motionless and the CCD
array moves. Most computer scanners work this way. A motor moves the CCD
array and the light source across the paper.
Sensors 73
Figure 3.17
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