C13440-20CU / C13440-20CU01 Instruction manual_Ver.1.3
29
10-2 READOUT METHOD OF CMOS IMAGE SENSOR
The exposure and the readout method of CMOS image sensor which this camera adopts is
rolling shutter. In the rolling shutter, the exposure and readout are done line by line. Therefore, the
exposure timing is different on one screen. (Figure 10-2) But even if the object moves during the
exposure, the affect of rolling shutter is very small.
Figure 10-2 Readout timing of Rolling shutter
10-3 PRECAUTION WHEN USING CMOS IMAGE SENSOR
This camera uses scientific CMOS image sensor. Careful attention must be paid to the following
points when using CMOS image sensor.
(1) White spot
Subjecting CMOS image sensor to extended exposures may cause failure in part of the silicon
wafer, resulting in white spots. Currently this phenomenon is not preventable. If CMOS image
sensor is at a fixed temperature, recurrence of the white spot increases proportionally with the
exposure time, so this can be rectified with dark subtraction*. Cosmic ray may generate white
spot.
*
Dark subtraction: After acquiring an image using a certain exposure time is loaded, CMOS image sensor is exposed to darkness for
the same amount of time, and another image is obtained. After this, the difference between the images is
determined, and the data for the dark portion of the original image is nullified.
(2) Folding distortion
A rough-edged flicker may be visible when imaging striped patterns, lines, and similar subject
matter.
(3) Over light
•
Be careful not to input too strong light such as high-energy laser into CMOS
image sensor because CMOS image sensor may be damaged by over light.
