ORCA-Lightning Digital CMOS Camera C14120-20P Instruction manual_Ver.2.5
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9. ABOUT IMAGE ACQUISITION
9-1 READOUT METHOD OF THE IMAGE
This camera uses scientific 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 four lines simultaneously. Therefore, the exposure timing is different on one screen.
However, even if the object moves during the exposure, the affect of rolling shutter is very small.
9-2 PRECAUTIONS WHEN USING THE 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) Excessive 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 excessive
light.
