What is a scanner?

Many computer peripherals, currently used at home, only recently could be found only in the offices of large companies. That's exactly what happened with computer scanners. Manufacturers quickly realized that this niche market is free, and were able to establish the release of budget- class devices whose functions fully meet the needs of the average home user.

Despite the fact that computer equipment stores offer a wide range of these devices, often the visitor has a question about what a scanner is. This is quite normal, because the desire for knowledge is natural. Today we will figure out what a scanner is, and what to look for when buying.

The scanner is an optical-mechanical device designed for converting graphic information into digital form, with which computer programs can operate. Here is a simple definition. However, in order to more fully understand what a scanner is, you need to study its internal structure. This will not only increase the luggage of knowledge, but will also allow choosing the most comfortable model.

The general principle of the scanner is simple: rays of light are directed to the object being scanned and partially reflected on the light-recording elements. Due to different levels of reflection (for example, black color reflects worse than white), the logical scheme of the device generates a digital "impression" of the item being scanned. This explanation allows more broadly to answer the question of what a scanner is, because it is possible to scan, you can even bulk objects, and not just text on paper, as many believe. But, nevertheless, for obvious reasons, the distribution has received highly specialized devices designed to work with text and graphics. Despite the similar principle of work, there are different types of scanners.

Most budget models are tablet devices. In them, a sheet of paper with graphic information printed on it is placed on a transparent window (glass, plastic) of the device and pressed from above with an opaque lid. Then a light stream is directed to the sheet and captured by the reflected light. The main element of the scanner is the matrix. There are two varieties of it: CIS and CCD. In the case of the first type of matrix under the glass on which the sheet is placed, there is a carriage with several stripes of LEDs and photocells. It slowly moves along the sheet, alternately including the lines of LEDs of red, blue, green (necessary for the formation of a color picture).

Such models are characterized by low cost and high reliability (there is nothing to break), so they can interest economical buyers looking for a solution for scanning text from white sheets. In this case, remember that the scanning speed is low, you need a tight pressure of the sheet to the glass, the quality of the pictures is mediocre.

In models with a CCD matrix, the carriage does not have diodes, but a backlight. Reflected light is collected by a system of focusing mirrors, to obtain a color image is divided into components of the spectrum and is captured by photocells. Such a solution made it possible to obtain bright and saturated images at the output, while a tight clamp to the glass is not required, since the intensity of the light flux is sufficient to overcome a short distance. The processing speed also increased significantly. We can say that today this is a pretty good solution. The drawbacks include the limitation of the lifetime of the lamp (in time it will have to be changed, unlike LEDs) and the need for an external power supply.

Scanners are characterized by a depth of color coverage (those same 24, 32, 48 bit) and resolution. The bits of color are not only the flow of the picture, but also the noise of the matrix itself, so the more, the better. On the other hand, for the house to chase the bits should not be - the printer outputting the scanned picture, physically can not display 48 bits. The resolution is indicated as XXX: YYY, where "XXX" is the resolution in points, and "YYY" is the carriage step.