NOIV1SN1300A Datasheet, PDF (27/76 Pages) ON Semiconductor – VITA 1300 1.3 Megapixel 150 FPS Global Shutter CMOS Image Sensor

NOIV1SN1300A, NOIV2SN1300A
Table 19. Configurable Parameters for Black Level Algorithm
Group
Addresses
Description
Black Line Generation
197[7:0]
black_lines
This register configures the number of black lines that are generated at the start of a
frame. At least one black line must be generated. The maximum number is 255.
Note: When the automatic black-level calibration algorithm is enabled, make sure that this
register is configured properly to produce sufficient black pixels for the black-level filtering.
The number of black pixels generated per line is dependent on the operation mode and
window configurations:
Global Shutter - Each black line contains 160 kernels.
Rolling Shutter - As the line length is fundamental for rolling shutter operation, the length of
a black line is defined by the active window.
197[8]
gate_first_line
When asserting this configuration, the first black line of the frame is blanked out and is not
used for black calibration. It is recommended to enable this functionality, because the first
line can have a different behavior caused by boundary effects. When enabling, the number
of black lines must be set to at least two in order to have valid black samples for the calib-
ration algorithm.
Black Value Filtering
129[0]
auto_blackcal_enable
Internal black-level calibration functionality is enabled when set to ‘1’. Required black level
offset compensation is calculated on the black samples and applied to all image pixels.
When set to ‘0’, the automatic black-level calibration functionality is disabled. It is possible
to apply an offset compensation to the image pixels, which is defined by the registers
129[10:1].
Note: Black sample pixels are not compensated; the raw data is sent out to provide ex-
ternal statistics and, optionally, calibrations.
129[9:1]
blackcal_offset
Black calibration offset that is added or subtracted to each regular pixel value when
auto_blackcal_enable is set to ‘0’. The sign of the offset is determined by register 129[10]
(blackcal_offset_dec).
Note: All channels use the same offset compensation when automatic black calibration is
disabled.
129[10]
128[10:8]
blackcal_offset_dec
black_samples
Sign of blackcal_offset. If set to ‘0’, the black calibration offset is added to each pixel. If set
to ‘1’, the black calibration offset is subtracted from each pixel.
This register is not used when auto_blackcal_enable is set to ‘1’.
The black samples are low-pass filtered before being used for black level calculation. The
more samples are taken into account, the more accurate the calibration, but more samples
require more black lines, which in turn affects the frame rate.
The effective number of samples taken into account for filtering is 2^ black_samples.
Note: An error is reported by the device if more samples than available are requested
(refer to register 136).
Black Level Filtering Monitoring
136
blackcal_error0
An error is reported by the device if there are requests for more samples than are available
(each bit corresponding to one data path). The black level is not compensated correctly if
one of the channels indicates an error. There are three possible methods to overcome this
situation and to perform a correct offset compensation:
• Increase the number of black lines such that enough samples are generated at the
cost of increasing frame time (refer to register 197).
• Relax the black calibration filtering at the cost of less accurate black level determina-
tion (refer to register 128).
• Disable automatic black level calibration and provide the offset via SPI register upload.
Note that the black level can drift in function of the temperature. It is thus recommended
to perform the offset calibration periodically to avoid this drift.
NOTE: The maximum number of samples taken into account for black level statistics is half the number of kernels.
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