Many computer peripherals, currently used at home, until recently, could only be found in the offices of large companies. This is exactly what happened with computer scanners. Manufacturers quickly realized that this market niche was free, and were able to arrange the release of budget- class devices , the functions of which fully satisfy the demands of the average home user.
Despite the fact that computer hardware stores offer a large assortment of these devices, often the visitor has a question about what a scanner is. This is quite normal, because the pursuit of knowledge is natural. Today we will understand what a scanner is and what to look for when buying.
A scanner is an optical-mechanical device designed to convert graphic information into digital form, with which computer programs can work. 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 knowledge base, but also allow you to choose the most suitable model.
The general principle of the scanner is simple: light beams are sent to the scanned object and partially reflected on the light-recording elements. Due to different levels of reflection (for example, black reflects worse than white), the logical circuit of the apparatus forms a digital “impression” of the scanned item. Such an explanation allows us to more broadly answer the question of what a scanner is, because it turns out that you can even scan voluminous objects, and not just text on paper, as many believe. But, nevertheless, for obvious reasons, highly specialized devices designed for working with text and graphics have gained distribution. Despite the similar principle of operation, there are different types of scanners.
Most budget models are tablet devices. In them, a sheet of paper with graphic information applied to it is placed on a transparent window (glass, plastic) of the device and pressed on top with an opaque cover. Next, a luminous flux is directed onto the sheet and is captured reflected. The main element of the scanner is the matrix. There are two varieties of it: CIS and CCD. In the case of the matrix of the first type, under the glass on which the sheet is placed, there is a carriage with several strips of LEDs and photocells. It slowly moves along the sheet, alternately including the lines of red, blue, green LEDs (necessary for the formation of a color picture).
Such models are notable for their low cost and highest reliability (there is nothing to break), therefore they may be of interest to economical buyers looking for a solution for scanning text from white sheets. At the same time, we remember that the scanning speed is slow, a tight clip of the sheet to the glass is necessary, and the picture quality is mediocre.
In models with a CCD matrix, there are not diodes on the carriage, but a backlight. The reflected light is collected by a system of focusing mirrors, to obtain a color image, it is divided into components of the spectrum and captured by photocells. This solution allowed us to obtain bright and saturated images at the output, while a tight clip to the glass is not required, since the light flux intensity is sufficient to overcome a short distance. Processing speed also increased significantly. We can say that today it is a pretty good solution. The disadvantages include the limitation of the lamp life (after a while it will have to be changed, unlike LEDs) and the need for an external power supply.
Scanners are characterized by the depth of color gamut (those same 24, 32, 48 bits) and resolution. The bits of color account for not only the flow of the picture, but also the noise of the matrix itself, so the more the better. On the other hand, one should not chase the bits for a house - a printer that displays a scanned image will not be able to physically display 48 bits. The resolution is indicated in the form XXX: YYY, where “XXX” is the resolution in points, and “YYY” is the carriage steps.