The most common devices for solving the problem of transferring paper documents to electronic copies are scanners. The translation of paper documents into electronic copies will save them almost forever. In addition, the development of the global network allows you to exchange information only in electronic form.

The most common devices for solving the problem of transferring paper documents to electronic copies are scanners

Scanners can be classified for a number of features. First of all, scanners are black and white and color. Black and white scanners can read line and halftone images. In color scanners, the scanned image is illuminated through a rotating filter that senses successively the three primary colors, or three successively lit red, green and blue lights.

The next important characteristic of scanners is the resolution, measured by the number of points to be distinguished per inch of the image. For normal operation of the recognition programs for images and texts, which are supplied with scanners, there is enough resolution in 300-600 dpi. For the publication of pictures on Internet web sites, the resolution is 80 dpi.

For large scan volumes, the scan speed of the document is very important. It can be measured in millimeters per second, but in practice the number of seconds used to scan a single page is more often used.

Structurally, scanners are divided into four types: manual, flatbed, roller and projection. Hand-held scanners move on the image manually. They are made in the form of a block with a handle, which is "rolled" over the image. Only one part of the image is scanned in one pass, since the scanning width does not exceed 105 mm. The entire image is scanned in a few passes. Special software, supplied with the scanners, allows you to combine parts of the scanned image.

Flatbed scanners are the most common type of scanner. In them, the scanning head (a ruler of light-emitting diodes) moves relative to a motionless original, which is placed on a transparent glass base. The advantage of such scanners is that with their help you can scan both sheet and scrapped documents (books).

Roller scanners are used for batch processing of sheet documents. In them, the feed of the next sheet for scanning is automatic. The scanning head in such scanners is stationary, and the sheet of the original moves relative to it.

Projection scanners differ from the other types in that the original is mounted in a frame, and scanning is performed on the lumen, usually with scaling.