Bryakotnin Nikolay Aleksandrovich

National research Irkutsk state technical university, Russia

Types of scanners and how they work

Articulation of the problem. Approximately every personal computer user often faces need of transformation of documents from a paper form in an electronic form. The procedure of manually input of such documents takes away a lot of time. During the process user may have mistakes. Besides, manually input is possible only for text documents, but not for images. The solution of the problem is a scanner which allows to type into the computer as text documents, so images. In this article I will provide the short review of scanners. This review serves to help users to choose device for home or office using.

The goal of research – to examine main characteristics of scanners in order for every user can optimally pick on suitable scanner.

Key findings

With the object of understanding the work of the scanner, it is necessary to know the principles of its work. This will allow understanding better technical characteristics which must be factored into a choice of scanners.

The flatbed scanner has a form of the rectangular plastic case with a cover. The original which needs to be scanned is located is placed under the cover on the surface from glass. There is the moving carriage, with the lamp of illumination and system of mirrors established on it. The carriage is moved by the stepper motor. The ray emitted by a lamp is reflected from the original then through the system of mirrors and the focusing lenses gets on a matrix. The matrix consists of sensors which generate electrical signals. The voltage value of such signals is defined by luminous intensity falling on the sensors based on photosensitive elements which are called a CCD - Couple Charged Device. Some couple charged devices are placed nearby on one line. The electrical signal leaving on these devices is analog quantity. Then an analog signal transform to a digital form. Hereafter the document already in a digital form is transferred to the computer for further using. Such function is carried out by the ATsP - Analog-to-digital Converter — ADC. Thus, while the carriage is moving the scanner reads in one for other horizontal strips of the original divide into discrete elements (pixels). Number of pixels is according to quantity of a CCD on a line.

In color scanners the three-row matrix of a CCD is, as a rule, used, and the original is lit by the white calibrated light. Each row in a matrix recognize to one of three color components of light: red, green and blue. In order to divide colors, are used the prism or the special filtering CCD cover decomposing a beam of white light to color components. Also there are color scanners with the matrix consisting of a one row CCD which in turn highlights the original by three lamps of basic colours.

There are CIS scanners (Contact Image Sensor) based on application of photoelement technology.

Photosensitive matrixes, which manufactured on such technology, distinguish light reflected by the original directly through scanner glass. This allows not using optical systems of focusing. Nevertheless such scanners are well suitable only for flat original which densely adjoin to glass on a operational field. Resultant of the image in such scanners depends on existence of foreign light sources (the cover of the CIS scanner shouldn't pass light and it has to be closed during scanning).

Tablet scanners are supplied with additional devices: slide adapter, automatic document feeder, etc. However not for all scanners it is provided.

The slide adapter (TMA - Transparency Media Adapter) — is special equipment which allows to scan transparent documents. Scanning of transparent documents provides by the passing light but which isn't reflected from the original. The slide adapter represents the hinged module supplied with a lamp moving synchronously with the scanner carriage. Some models of slide adapters evenly light a site of a operational field for not moving a lamp.

Automatic feeder — a device which submits originals to the scanner. It is convenient to use at in-line scanning of the homogeneous documents when it isn't required to recustomize the scanner often.

There are other types of scanners exist as well: handheld, sheetfed, drum, slide, for scanning of bar codes, high-speed for line production with originals.

The handheld scanner — is the portable scanner scanning by movement of the scanner manually on the paper. The principle of operation of such scanner is similar to the principle of operation of the tablet scanner. Width of area of scanning doesn't exceed 15sm.

The roller or sheetfed scanner — is the scanner stretching the original by a motionless linear matrix.

The drum scanner — is the scanner fixed the original document on the rotating drum. In the process of scanning photoelectronic multipliers are used. Such scanner scans dot area of the image, and the scanning head moves very close to the original along a drum.

The film-scanner — is a kind of tablet scanners which is intended for scanning of transparent originals. As a rule the size of transparent originals is fixed.

The bar-code scanner — is the scanner which is intended for scanning of bar codes. The principle of operation of such scanner is similar to the handheld scanner. The scanner is connected to the computer, or to special trade system. The scanner of any kind in the presence of the corresponding software can distinguish bar codes.

The high-speed scanner intended for work with documents (Document Scanner) — is a version the sheetfed scanners which are intended for high efficiency of multipage input. Such scanners are equipped with input and output trays calculated on volume over 1000 sheets and can enter the scanned information with a speed over 100 sheets/minute. Some models of such type can provide bilateral (duplex) scanning; also some models provide illumination of the original in various colors, for the purpose of a cut-off of a color background or compensation of heterogeneity of a background. High-speed scanners have modules of dynamic processing of polytypic originals.

The listed parameters don't settle all list.

Conclusion

Popularity of scanners more grows for office and home use. In the process of a scanner choice such parameters are decisive: hardware interface (way of connection), optical-electronic system and program interface (TWAIN module). For office and the home the tablet scanner will become the best option. If you want to be engaged in graphic design, the CCD scanner (on the basis of a CCD matrix) as it allows scanning even volume subjects will be the best variant. If you plan to scan slides or other transparent originals, the scanner, with the slide adapter provided for it will become the suitable scanner. Everyone who can imagine a variety of application of modern technologies of input of documents understands how the scanner can expand its opportunities.

Literature

1. Stepanenko O. S. Scanners and scanning. Publishing house: Dialectics, 2004 g. 288 p.

2. Shpunt Ya.B. How to choose the scanner which is necessary to you. Publishing house: NT Press, 2004 g. 144 p.

3. Shpunt Ya. B. In total about scanners. Publishing house: Nuclear heating plant, 2004g. 416 p.

4. Sokolenko A.L. Skaner and scanning. Publishing house: Eksmo, 2006g. 160 p.