The scanner is a device that uses photoelectric technology and digital processing technology to convert graphics or image information into digital signals by scanning.
Scanners are usually used for external computer equipment. By capturing images and converting them into digital input devices that computers can display, edit, store, and output. The scanner can be used to scan photos, text pages, drawings, art pictures, photographic negatives, photographic films, and even three-dimensional objects such as textiles, sign panels, printed board samples to extract and convert original lines, graphics, text, photos, and planar objects into devices that can be edited and added to files. The scanner belongs to the input system of computer-aided design (CAD). Through computer software and computer, the interface of output equipment (laser printer, laser plotter) forms the computer processing system before screen printing. It is suitable for office automation (OA) and is widely used in sign panel, printed board, printing industry, etc.
Scanners can be divided into three types: drum scanners, flat scanners, and emerging scanners, including pen scanner, portable scanner, and paper-feed scanner, which are only available in recent years.
Pen scanner appeared in around 2000, and its scanning width was only about the size of the 4th Chinese character. When it was used, it was used to scan line by line on paper and was mainly used for character recognition.
Drum scanners generally use photomultiplier tube PMT, so it has a large density range and can distinguish finer level changes of images. The plane scanner uses a photoelectric coupling device CCD, so its scanning density range is small. CCD (photoelectric coupling device) is a strip-shaped photosensitive component, which is used to convert the light wave reflected from the image into a digital signal during scanning. CCD used in plane scanners is mostly color image photoreceptors with a linear display of fluorescent lamps.
The paper-fed scanner is also called a small drum scanner. The paper-fed scanner came out at the beginning of 90 generations. Due to the high price of the flat-plate scanner and the small scanning width of the hand-held scanner, apart from a3 paper scanner, in order to meet the needs of A4-format document scanning, this product is introduced in color and grayscale. The color model is generally 24-bit color, but still, a few paper-fed scanners adopt CCD technology, whose scanning effect is obviously better than that of products using CIS technology. However, due to structural limitations, the volume is generally significantly larger than that of CIS technology products.