In computing, an image scanner is a device used to transfer images or text into a computer. There are special models for scanning photo negatives, or to scan books. In the computer, the signal from the scanner is transferred to a digital image. This image can then be edited, printed, etc. All scanners have special parts which are used to take a picture from an object. Charge-coupled device or Contact Image Sensor parts take the light from the object and change it into a digital signal. The digital signal is then transferred to the computer memory or is read in the scanner's processor. With some software it can be changed to a compressed digital image, like JPEG or PNG. Text printed or written by hand can be changed to ASCII code by an OCR program.
The main types of scanner
- Desktop scanner (flatbed) This is probably the most popular type. An object to be scanned (picture, image, text sheet) is put on the glass. Under the glass, there is a moving Image Sensor.
- Hand scanner. The device is moved on the paper by hand. It was popular during the 1990s.
- Rotary scanner (Drum Scanner) used for fast scanning large numbers of sheets of paper.