contact image sensor (CMOS) (CIS)
A Contact ImageSensor(CIS) is a low-cost image sensor used primarily in flatbed scanners and fax machines. It is based on CMOS technology and is cheaper to manufacture than CCD sensors. CIS sensors are line sensors consisting of an illumination system, an optical system and the sensor system.
The CIS sensor system is light-sensitive semiconductors arranged in rows as individual square photocells. Depending on the resolution, there can be 5,000 or more light-sensitive photocells. At a maximum resolution of 400 dpi, for example, the CIS cell size is only 0.05 mm. The optical lens system is a rod lens arrangement that directs the light reflected from the document being illuminated to the sensor cells. The illumination system itself is parallel to the sensor system and consists of red, green and blue light-emitting diodes that sequentially illuminate the document with the three primary colors, which then reflect the colors on the document that are detected by the CIS sensors.
CIS sensors do not have complex optics and are therefore flatter but also less sensitive than CCD sensors, which is noticeable in the image noise. However, the resolution is comparable or even higher than that of CCD sensors. It lies between 200 dpi and 600 dpi. Depending on their structure, CIS sensors have a better edge representation, clearer lines and lower corona effects.