Bg BG0836 - Adjust the Gain Strategy; Black Level Calibration; Table 18 BLC Control Register

V1.2
BG0836 1/2.7 inch 1080P HD CMOS image sensor
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Adjust the gain strategy
The strategy of gain mapping is shown as below. Assuming that gain is total system
gain:
(1) If gain is less than or equal to the maximum limitation of the analog gain, analog
gain is set to gain, and digital gain is set to 1 times.
(2) If gain is greater than the maximum limitation of the analog gain. First, less than the
limit part map to the maximum analog gain, the rest map to digital gain.
(3) The analog gain maximum before and after（ vrefh equal to 0x0c and vrefh
greater than 0x0c），There are additional register need linkage to ensure the best
image quality(Refers to vertical grain which under the maximum gain, specific
settings related to frame rate, please consult to FAE or refer to sample code).
(4) Write back to the Sensor internal registers through the I2C.
Black level calibration
BG0836 chip provides black level correction module. Its basic principle is using the
black level reference pixel to correct the effective pixels for black level, to eliminate
circuit, the environment temperature brought the black level drift.
Table 18 BLC control register
Name
Address
Width
Function
BLC_CTRL
0x0120
7
Bit[6:1] Reserved
Bit[0]: BLC enable, valid high 。
DBLC_OB_H
0x0130
4
[11:8] of Object of expected final image,
unsigned.
DBLC_OB_L
0x0131
8
[11:8] of Object of expected final image,
unsigned.
DBLC_LOWER
HI_ADJ
0x0136
8
Adjust the lower bound of convergence
range, unsigned.
DBLC_UPPER
LO_ADJ
0x0137
8
Upper bound of convergence range, lower
bound, unsigned.
DBLC_UPPER
HI_ADJ
0x0138
8
Upper bound of convergence range, higher,
bound, unsigned.
BLC_CTRL is the switch of control for BLCC function；
BLCC target value is adjust by DBLC_OB, It means that expect to get the black level.
after the BLCC completed the operation.
BLC_LOWERHI_ADJ, BLC_UPPERLO_ADJ, DBLC_UPPERHI_ADJ is used to adjust
the range of stability of the algorithm. The final convergence signal is as shown in Figure
14 BLC Convergence signal.