Omnivision CameraChip OV9650, Руководство по внедрению

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Analog Processing Block
Version 1.1, December 7, 2004 Proprietary to OmniVision Technologies 23
O
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The AGC operation is identical to the AEC (see Section 3.4.1.2 ). Table 4-4 lists the registers used
to set the AGC convergence limits.
4.1.2.1 Center-Based Reference Area Enable
Enabling this option changes the AEC/AGC exposure reference from the whole image to the
center-quarter, or center-half of the array (set in the AEC section - see
Section 3.4.1.2 ).
4.2 White Balance Control
The OV9650 C
AMERA
C
HIP
supports auto/manual white balance control. After the initial pixel level
adjustment, the Red and Blue channel gains are optimized to the Green channel to set the white
balance. This white balance is either automatically-controlled by the AWB circuit or
manually-controlled by the user. The following describes these AWB modes:
• Full user control
–
RED/BLUE channels are set manually
• Normal AWB control
–
RED/BLUE channels are under AWB control based on R/G/B average values
• Advanced AWB control
–
RED/BLUE channels are under AWB control based on color temperature
Register COM8 [1] (0x13) enables the AWB function. If this bit is set low, the user can manually
control red and blue gain. If this bit is set to high, the red and blue gain is controlled by the sensor’s
internal AWB algorithm.
Table 4-4. AGC Convergence Limits
Function Register Address
Control Zone – Upper Limit high nibble VPT [7:4] 0x26
Control Zone – Lower Limit high nibble VPT [3:0] 0x26
Stable Operating Region – Upper Limit AEW [7:0] 0x24
Stable Operating Region – Lower Limit AEB [7:0] 0x25
Step Size Limit COM8 [6] 0x13