qCMOS Camera C15550-20UP / C15550-20UP01 Instruction manual_Ver.1.3
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10-2 READOUT METHOD OF CMOS IMAGE SENSOR
The qCMOS camera adopts a rolling shutter readout for high speed imaging. In the camera, the odd and
even lines are read out in pairs, therefore the exposure and readout timing is slightly delayed as the
readout moves down the sensor (Figure 10-2). The affect of the rolling shutter timing is very small for
most exposure times.
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.
Rolling shutter
Exposure length is same for all lines
Exposure timing is different for every two lines
