How Scanners Work - Microtek ScanMaker IIG User Manual

How scanners work

Scanners capture images by
shining light onto the
document to be scanned. The
light then bounces back and
is captured by a strip of light-
sensitive cells called a
charge-coupled device, or
CCD.
Since dark areas on the paper
reflect less light and light
areas of the paper reflect
more light, the CCD is able
to detect the amount of light
reflecting from each area of
the image. The CCD then
converts the reflected light
waves into digital informa-
tion, represented by combina-
tions of ones and zeros
(called bits, for binary digits).
Finally, the scanning software
that controls the operation of
the scanner reads this
incoming data and recon-
structs it into a computer
image file.
The process above describes
how scanners scan an opaque
original, such as a photo-
graphic print or page of text.
The same principle works if
you scan a transparency instead
of an opaque document, but
instead of bouncing back, the
light passes through the
transparency and is captured by
the CCD. Scanning a transpar-
ency involves special lighting
considerations, so a scanner
accessory called a Transparent
Media Adapter is specifically
used for this purpose.
Basic Concepts 1-3