How scanner work

Scanners are very useful in our lives. But do you know how do they work? I will make a short introduction of them.

According to the different photosensitive elements, the scanners belong to three different types: CCD, CIS and photo multiplier tube.

CCD is the photosensitive element of our digital cameras. So it is not hard to understand that this type of scanners actually work like cameras. The main difference between camera and scanners is that the scanners only take a picture of  a line of the subject and combine the pictures of different lines into a whole picture of the subject.

CCD(photo by BAIDU.COM)

CIS use photosensitive resistances instead of CCD. The CISs can be very small. But the quality of the picture that the scanners take are very poor when compared to CCD.

Photo multiplier tubes work very different with the other two types. They use the principle that oxide of some material can emit electron when the light beating on them. Another element in the scanners can analysis the electrons flow and get the digit picture of the subject.

Photo multiplier tubes(photo by baidu.com)

What type of your scanners?