S5K433CA Datasheet, PDF (21/25 Pages) Samsung semiconductor – 1/4 Optical Size 640x480(VGA) 3.3V/2.8V VGA CMOS Image Sensor

1/4 INCH VGA CMOS IMAGE SENSOR
S5K433CA, S5K433LA
By appropriately programming these four register values, the different output resolution according to the signal
can be achieved and the intra-scene dynamic range can be increased by 16 times. In another application, the
sectional global gain control can be used as a rough gamma correction with four sectional linear approximation
curve as shown in Figure 9.
sgg1
sgg2
sgg3
sgg4
sgg1=1111b
sgg2=0111b
sgg3=0011b
sgg4=0000b
sgg1=0111b
sgg2=0111b
sgg3=0111b
sgg4=0111b
0
255
511
767
1023
ADC output code at 10-bit resolution
Figure 9. Quadrisectional Glabal Gain Control
3. Post Processing
3-1. Dark Level Compensation
The dark level of Image sensor is defined as average output level without illumination. It includes pixel output
caused by leakage current of the photodiodes and ADC offset. To compensate the dark level, the output level of
optical black(OB) pixels can be a good reference value. When Auto Dark Level Compensation Register (dlcm) is
set, the image sensor detects the OB pixel level at the start of every frame and analog-to-digital conversion range
is shifted to compensate the dark level for that frame. So, the resulting output data of that frame will be almost zero
under dark state. If user wants the dark level which is not zero, the ADC Offset Register (adcoffs) can be used.
The lower 7-bit value represent the offset value in output code for compensation and the MSB is the sign to define
whether the offset is positive (adcoffs[7]=0) or negative (adcoffs[7]=1). When not in auto dark level
compensation mode, the adcoffs[7:0] act as a output code value to subtract the output image data. Please notify
that the all the 8-bit data are used for an offset value without sign bit.
3-2. Bad Pixel Replacement
When the Bad Pixel Replacement Register (bprm) is enabled, the image sensor check that the image data is
less or greater than horizontally neighboring pixels in same color channel by the preset threshold value (pthresh).
If satisfied, the output of the pixel is replaced by the averaged value of the neighboring two pixels. The detectable
defected pixels are rare and the bad pixel replacement action can remove defected image effectively. But it
reduces the line resolution in horizontal direction.
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