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How A Scanner Works
A scanner is a device that captures and converts images to a
computer format. Its eyes are an array of photosensitive
cells that detect light reflected off or transmitted through
the object being scanned. This array of receptors, referred
to as a charged-couple device (CCD), measures light
intensity and converts it into an electrical charge.
An
analogue to digital converter (ADC) is then required to
digitize the information, putting into a form your computer
can understand. Each cell in the CCD array creates one pixel
and for each pixel a certain number of bits is stored. The
more bits of information assigned to each pixel the better
the image quality.
There
are also scanners that use CIS (Contact Image Sensor)
technology. With a CCD scanner, the light reflected from the
original document passes through a system of mirrors and
lenses which redirect the light to the CCD array. In a CIS
scanner, the array of image sensors lies just under the
document to be scanned so the sensors catch the reflected
light directly. CIS scanners are cheaper to manufacture,
smaller and more durable, however their image quality is not
as good as CCD. They are more suited to cramped desktops and
make useful portable scanners.
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