1 - When you press the scan button of a common manual scanner, a light emitting diode (LED) illuminates the image that is under the scanner. An inverted mirror angle, positioned immediately above the scanner window, reflects the image the lens located at the back of the scanner.
2 - The lens focuses on a single line of the image through a device called a charge coupled device, or CCD
(Charge Coupled Device), designed to detect sudden changes in voltage. The CCD has a line of
light detectors. When light strikes these detectors, each of which registers the amount of light as a degree of tension that corresponds to white, black, or gray color.
3 - The tensions generated by the CCD are sent to a particular chip analog to be made a correction range,
process which improves the black image tone so that the human eye is more sensitive to light than
to dark tones, can more easily recognize the image. In some scanners, gamma correction is performed by a program.
4 - The online image is now going through an analog-digital (AD). A grayscale scanner, the converter
associates 8 bits each pixel, converted into 256 gray levels in the final scanned image. The AD converter of a
monochrome scanner records only 1 bit per pixel, active or not, representing, respectively, black or white.
5 - As the hand moves the scanner, a rubber bearing drive - whose main purpose is to ensure the
stability of the paper - also drives a series of gears that rotate the inner disk.
6 - As the disc rotates, the light passes through the cylinder and is detected by a location of fotomicrossensor
Furthermore the disc. When light strikes the sensor triggers a switch that sends a signal to the AD converter.
The signal asks the converter to send the bit line generated by the drive to the PC. The converter gets rid of the data, preparing to receive a new flow stress of the next line of the image.
Source: Evolution of Computers
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