Scanner is a device that uses photoelectric technology and digital processing technology to convert graphic or image information into digital signals through scanning. Scanners are usually used as external instruments of computers, which capture images and convert them into digital input devices that computers can display, edit, store and output. Scanners can scan three-dimensional objects, such as photos, text pages, drawings, artistic pictures, photographic negatives, films, and even textiles, signs, printed board samples, etc. , and extract and convert original lines, graphics, characters, photos and plane objects into devices that can be edited and added to files. Scanner belongs to the input system of computer aided design (CAD). Through the interface of computer software, computer and output equipment (laser printer and laser plotter), a front-screen computer processing system suitable for office automation (OA) is formed, which is widely used in signboard, printed board and printing industry.