CIS is the abbreviation of English contact image sensor, which is literally translated as “contact image sensor”. It is used in the scanner to arrange the photosensitive units closely, and directly collect the light information reflected by the scanned manuscript. Because of its low cost and no lens group, it can produce a more compact scanner, and the cost is greatly reduced. However, due to the contact scanning (must keep a very close distance with the original), only led light source can be used, the depth of field, resolution and color performance are not as good as CCD, and can not be used to scan the transmission film. Anson Semiconductor provides a contact image sensor module that integrates light source, lens and image sensor in a compact package.
Working principle of contact image sensor
CIS is composed of len light source array, rod lens array, CMOS image sensor array and its circuit board, protective glass, interface and shell. The components of CIS are all concentrated in the shell, compact in structure, small in volume and light in weight. The production of its main components needs micro manufacturing process. When CIS works, the light emitted by LED light source array is directly directed to the surface of the object to be scanned (printed matter, etc.), and the light reflected from the surface is focused by the self focusing rod lens array and imaged on the photoelectric sensor array (generally MOS devices), which is converted into charge storage.
The light intensity of different parts of the scanning surface is different, so the light intensity received by different position sensor units (CIS pixels) is different. The illumination time (charge accumulation time) of each pixel in each reading cycle is consistent. When the accumulation time is reached, the shift register controls the analog switch to turn on in turn, and outputs the electrical signal of each pixel in the form of analog signal in turn, so as to obtain the analog image signal of the banknote.
Advantages of contact image sensor
1. CIS light source, sensor and amplifier are integrated. Its structure, principle and optical path are very simple. It has the characteristics of small volume, light weight, compact structure and easy installation;
2. There are no glass devices such as lamp and optical lens in CIS, so the anti-seismic performance is good;
3. CIS adopts single clock drive / timing logic, which makes the control simple;
4. CIS changes from power saving state to working state very quickly, so there is no need to preheat the scanner using CIS;
5. CIS mostly uses ceramic substrate, which has good temperature characteristics;
6. Using semiconductor manufacturing process, the production cost is low.