1 - A light source illuminates the piece of paper placed face to the glass window located above the
scanner. The voids or white reflect more light than the parts that have letters or pictures, colored or not.
2 - A motor moves the scanning head located below the page. The move allows the scanning head to capture light that bounces off of the main areas about 1/90.000 square inch each.
3 - light from the page is reflected through a mirror system constantly adjusted so that the beam
light are aligned with the lenses.
4 - The lenses focus the beam of light in photosensitive diodes that convert light intensity into electrical current.
The greater the reflected light, the higher the chain tension.
5 - An analog-to-digital (AD) stores each reading analog voltage as a digital pixel represented by
an area of a black or white line that contains about 300 pixels per inch. The more sophisticated scanners can
convert tensions in shades of gray. If the scanner works with color images, the scan head passes
three times the images, and each pass the light is directed to a filter red, green or blue before reaching
original image.
6 - The digital information is sent to the program installed on the PC, where the data is stored in a format compatible
with the graphics program or program of optical character recognition (OCR).
Source: Evolution of Computers
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