mt9v032 aptina, mt9v032 Datasheet - Page 48

• Manufacturer Part Number: mt9v032
• Description: 1/3-inch Wide-vga Cmos Digital Image Sensor
• Manufacturer: aptina

Black Level Calibration
Figure 26:
PDF: 6538045704/Source:2194051501
MT9V022_DS - Rev. C 9/10 EN
Black Level Calibration Flow Chart
Voltage (R0x48 or
Offset Correction
Black level calibration is controlled by:
• R0x4C
• R0x42
• R0x46–R0x48
The MT9V032 has automatic black level calibration on-chip, and if enabled, its result
may be used in the offset correction shown in Figure 26.
The automatic black level calibration measures the average value of pixels from 2 dark
rows (1 dark row if row bin 4 is enabled) of the chip. (The pixels are averaged as if they
were light-sensitive and passed through the appropriate gain.)
This row average is then digitally low-pass filtered over many frames (R0x47, bits 7:5) to
remove temporal noise and random instabilities associated with this measurement.
Then, the new filtered average is compared to a minimum acceptable level, low
threshold, and a maximum acceptable level, high threshold.
If the average is lower than the minimum acceptable level, the offset correction voltage
is increased by a programmable offset LSB in R0x4C. (Default step size is 2 LSB Offset = 1
ADC LSB at analog gain = 1X.)
If it is above the maximum level, the offset correction voltage is decreased by 2 LSB
(default).
To avoid oscillation of the black level from below to above, the region the thresholds
should be programmed so the difference is at least two times the offset DAC step size.
In normal operation, the black level calibration value/offset correction value is calcu-
lated at the beginning of each frame and can be read through the two-wire serial inter-
face from R0x48. This register is an 8-bit signed two’s complement value.
However, if R0x47, bit 0 is set to “1,” the calibration value in R0x48 may be manually set
to override the automatic black level calculation result. This feature can be used in
conjunction with the “show dark rows” feature (R0x0D, bit 6) if using an external black
level calibration circuit.
result of BLC)
(reset minus signal)
Pixel Output
Σ
C1
49
C2
MT9V032: 1/3-Inch Wide-VGA Digital Image Sensor
Gain Selection
result of AGC)
(R0x35 or
Aptina reserves the right to change products or specifications without notice.
10 (12) bit ADC
(R0x2C)
©2005 Aptina Imaging Corporation. All rights reserved.
V
REF
Feature Description
ADC Data
(9:0)