Contact Image Sensor (CIS) Technology



Overview:


The conventional document scanning with CCD requires a lens, which might cause image distortions, e.g. pin cushion distortion, especially for large sized documents. Scanning with CIS usually generates 1:1 images without any distortion.


       



Scanning Methods:


There are two types of scanning methods:


1)     Sheetfed type:

The document sheet is fed  though the CIS module by a roller


2)     Flatbed type:

The document stays flat on a glass bed while the CIS module moves across the whole sheet.

 


                                


CIS Structure:


CIS is composed of the following components:

1)     Sensor Array and PCB

      

     Sensors are aligned and mounted on a PCB with other passive components. Sensors’ characteristics defines the key features of the CIS, such as resolution, scanning speed, sensitivity, MTF, etc.


2)     Light Source – to provide light for image scanning.

v There are two types of light sources.

·       Light Bar is for high speed CIS, it consists of array of LEDs evenly on a PCB.

·       Light Guide is for low speed CIS, it has acrylic rod to convey uniform light from LED(s).

v Numbers of light sources – Single-light is for low speed and low cost, while dual-light is good for high speed and wrinkled object scanning.

v The LED wavelengths (or colors) supported: UV, R,G,B, NIR, White

·       UV (ultra-Violet):        365 nm & 390 nm

·       Visible:                        Blue, Green, Red

·       NIR (Near Infrared):   880 nm & 940 nm 

3)     Lens Array – to focus the image for scanning

Sometime it is called Rod Lens or SLA (SELFOC Lens Array). There are single-row or dual-row types available, dual-row is for better collimation. Besides glass material with better quality, the Rod lens can be made of plastic material as well. 

4)     Cover Glass – The focus point of CIS is on the surface of the glass, which also serves as a protection.

5)     Connector – The inputs/outputs of CIS. A cable is required to connect CIS to a system.

6)      Housing – To house everything together, normally it is made of plastics, however, aluminum housing is also available for harsh environment.

 

* CMOS supports customization from standard CIS modules according to customer’s requirments.