Description Of Various Functions; Theory Of Cmos Image Sensor - Hamamatsu Photonics C11440-36U Instruction Manual

C11440-36U Instruction Manual Ver.1.1

9. DESCRIPTION OF VARIOUS FUNCTIONS

9-1

THEORY OF CMOS IMAGE SENSOR

The pixel of a CMOS image sensor is composed of the photodiode and the amplifier that
converts the charge into voltage. Entered light is converted to charge and converted to voltage in
the pixel. The voltage of each pixel is output by switching the switch one by one. (Figure 9-1)
The CMOS image sensor used in this camera has an on-chip CDS (correlated double sampling)
circuit, which plays an important role in achieving low noise. In addition, the data of one
horizontal line is read by the on-chip column amplifier and A/D in parallel and simultaneously.
Therefore, the CMOS image sensor realizes both low noise and high speed readout
simultaneously.
In general, rolling shutter method is commonly used as the exposure and the readout mode of
the CMOS image sensor. In this method, the exposure timing is varied by each line. This
variation can cause distortion when capturing a moving subject.
On the other hand, a global shutter method is applied in this camera. Thereby the exposure
timing is same at the all lines.
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Amp
CDS
A/D
Digital data out
Figure 9-1 Structure of the CMOS image sensor
CDS CDS
A/D A/D