What are Optical Scanners

Optical scanner converts a physical entity into a digitized form that can be stored as a 2D image file on a computer. This physical entity can be an image, text, characters, diagrams, or any object. It comes under the category of hardware input devices as it takes physical entity as an input. Any image or a text can be converted into a digital file using this and this allows the computer to read or display the scanned object.A scanner is usually connected via USB port, FireWire port or the SCSI (Small Computer System Interface) port to a computer system. Optical scanner uses a light beam to scan the codes, text or any graphical image. Some other purposes for which optical scanners are used includes creating of automated data fields, reading customized response forms or recording fingerprints.

Optical scanner have been in existence from the decades are have accordingly become much cheaper and cheaper with the time. But still some good scanners are worth hundreds of dollars while the range itself starts from a mere few US Dollars. These scanners do not distinguish text from illustrations. They represent all images as bit maps. Thus the text which is scanned cannot be edited directly by the user. The text which is read by an optical scanner can only be edited with the help of an Optical Character Reader (OCR). This helps in translating the image into ASCII characters with the help of which the text can be edited. These days the optical scanners come with OCR packages.

The main part of an optical scanner is a charge coupled device (CCD). It is the same light sensor system used in digital cameras and camcorders. A CCD is basically an array of light-sensitive diodes called photosites, which generate an electrical signal in response to light photons. Each photosite records a pixel, a tiny dot representing the light that hit that spot.

The optical scanner processor makes sure the CCD has captured a clear image by checking the darkness of the pixels. If the overall image is too light or too dark then it rejects the image. In case of the rejected image the scanner adjusts the exposure time and then tries the scan again. But if the darkness level is adequate, the scanner system goes on to check the image definition and proceeds further depending upon the image definition.

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