MT9M001C12STM-EVAL Micron Technology Inc, MT9M001C12STM-EVAL Datasheet - Page 23

• Manufacturer Part Number: MT9M001C12STM-EVAL
• Manufacturer: Micron Technology Inc

Specifications of MT9M001C12STM-EVAL

• Lead Free Status / Rohs Status: Compliant

Figure 13: Readout of Eight Pixels in Normal and Column Skip Output Mode
Black Level Calibration
PDF: 09005aef81c2856f/Source: 09005aef80a3e031
MT9M001_DS_2.fm - Rev. F 5/06 EN
The MT9M001 has automatic black level calibration on-chip which can be overridden by
the user, as described below and shown in Figure 14.
The automatic black level calibration measures the average value of 256 pixels from two
dark rows of the chip for each of the four colors. The pixels are averaged as if they were
light-sensitive and passed through the appropriate color gain. This average is then digi-
tally filtered over many frames.
For each color, the new filtered average is compared to a minimum acceptable level (to
screen for too low a black level) and a maximum acceptable level. If the average is lower
than the minimum acceptable level, the offset correction voltage for that color is
increased by one offset LSB (offset LSBs do not match ADC LSBs; typically, one offset
LSB is approximately 2mV). If it is above the maximum level, the level is decreased by 1
LSB (2mV). The upper threshold is automatically adjusted upwards whenever an
upward shift in the black level from below the minimum results in a new black level
above the maximum. This prevents black level oscillation from below the minimum to
above the maximum. The lower threshold is increased with the maximum gain setting
according to the formula described under Reg0x5F. This prevents clipping of the black
level.
Whenever the gain or any of the readout timing registers is changed (shutter width,
vertical blanking, number of rows or columns, or the shutter delay) or if the black level
recalculation bit, reset bit or restart bit is set, the running digitally filtered average is
reset to the first average of the dark pixels. The digital filtering over many frames is then
restarted. Whenever the gain or the readout timing registers are changed, the upper
threshold is restored to its default value.
After changes to the sensor configuration, large shifts in the black level calibration can
result. To quickly adapt to this shift, a rapid sweep of the black level during the dark-row
readout is performed on the first frame after certain changes to the sensor registers. Any
changes to the registers listed above will cause this recalculation. The data from this
sweep allows the sensor to choose an accurate new starting point for the running
average. This procedure can be disabled as described under Reg0x5F.
Column skip readout
Normal readout
D
D
LINE_VALID
OUT
LINE_VALID
OUT
9–D
9–D
OUT
OUT
0
0
MT9M001: 1/2-Inch Megapixel Digital Image Sensor
(9:0)
(9:0)
G0
G0
23
(9:0)
(9:0)
R0
R0
(9:0)
(9:0)
Micron Technology, Inc., reserves the right to change products or specifications without notice.
G1
G2
(9:0)
(9:0)
R1
R2
(9:0)
G2
(9:0)
R2
©2004 Micron Technology, Inc. All rights reserved.
Feature Description
(9:0)
G3
(9:0)
R3