Data Sheet

CMOS VGA (640 x 480) image sensor with OmniPixel3-HS™ technology
OV7675/OV7175
proprietary to OmniVision Technologies PRODUCT SPECIFICATION version 2.0
4.4.4 manual exposure control
The OV7675/OV7175 works in manual exposure mode when register 0x13[0] is low. In manual exposure control mode
the companion backend processor can fully control the OV7675/OV7175 image exposure. The companion backend
processor may write exposure values to AEC [15:0] according to its corresponding Automatic Exposure Control (AEC)
algorithm.
The companion processor also needs to set correct exposure time to avoid banding in flicker light. Refer to section 3.3.1
and 3.3.2 for the exposure time calculation.
4.4.5 automatic exposure control (AEC)
The AEC function allows for the image sensor to adjust the exposure without external command or control. The
OV7675/OV7175 supports average based AEC. Note that both AEC and AGC functions are controlled by the same
algorithm and share the same registers of the algorithm parameter. In general, the AEC is the primary control and will be
adjusted before the AGC (AGC acts to adjust and center the AEC).
The average based AEC/AGC defines the fast operating region in which the AEC/AGC adjusts the image luminance very
fast by increasing the exposure time and gain adjustment.
0xA5 BD50MAX Bit[7:0]: Banding filter maximum step for 50Hz light source
0xAB BD60MAX Bit[7:0]: Banding filter maximum step for 60Hz light source
0x3B COM11
Bit[1]: Exposure time option
0: Limit the minimum exposure time to 1/100 or 1/120 second
in any light condition when banding filter is enabled
1: Allow exposure time to be less than 1/100 or 1/120 second
under strong light conditions when banding filter is enabled
table 4-5 exposure control mode registers
address register name description
0x13 COM8
Bit[7]: AEC operation speed
0: Normal speed
1: Fast speed
0x13 COM8
Bit[6]: AEC step size limit
0: Unlimited step size
1: Step size limited to vertical bank
0x13 COM8
Bit[3]: Pixel level exposure ON/OFF selection
0: Limit the minimum exposure time to 1 line
1: Allow exposure time less than 1 line
0x13 COM8
Bit[0]: AEC enable
0: Disable AEC
1: Enable AEC
table 4-4 exposure time registers (sheet 2 of 2)
address register name description
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