Image scanner#Flatbed

A flatbed scanner is a building type of a scanner, in which the material is placed with the documents face down on a glass plate. To scan drives a lighting and scanning in a "bed" under the glass plate by, similar to the scanning unit in a digital photocopier. Different types of flatbed scanners are for example the desktop scanner or the XY scanner with a variable lens. With flatbed scanners formats can be scanned up to DIN A0. Since the scanned material is not fed or otherwise moved, any objects are scanned with flatbed scanners, from a postage stamp to go with the book page.

CCDs

The electronic components for image acquisition are rows of photodiodes. This is a sequence of about 8000 light sensors which generate an electric current when incident light. The line scanning can be performed once per each color, or even with 3-way line, each with a color filter. The light sensors are color blind, that is, it is only the intensity of the color, not the color itself recognized.

The nature of CCD elements may be caused by different light sensitivities of the photocells to image defects. A drum scanner is therefore the current state of the art often better quality than a flatbed scanner.

For a high quality cooling of the CCD is required. Increasingly, energy-saving scanning units with contact image sensors and LEDs are used.

Scan transparent materials

Transparent objects such as slides and negatives can not be like paper photos and other regulatory documents scanned as they need to be lit from the front instead of the opposite side. Flatbed scanner with a so-called transparency unit can solve this problem. See: Film Scanner

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