AR0231AT
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Figure 7. Grid−ROI, Configuration 1; x_grid_status=0x3; y_grid_status=0x3
X Output Size
Y Output Size
offset1
offset2
offset3
X = X
offset
1
X = X
offset
2
X = X
offset
3
(0, 0) (0, 1) (0, 2) (0, 3)
(1, 0) (1, 1) (1, 2) (1, 3)
(2, 0) (2, 1) (2, 2) (2, 3)
(3, 0) (3, 1) (3, 2) (3, 3)
Black Level Control/Correction
Black level correction can optionally be automatically
controlled by the AR0231AT; the default setting is for
automatic black level calibration to be enabled. The
automatic black level correction measures the average value
of pixels from a set of optically black pixel rows in the image
sensor. The pixels are averaged as if they were light sensitive
and passed through the appropriate gain. This line average
is then digitally low−pass filtered over many frames to
remove temporal noise and random instabilities associated
with this measurement. The optically black lines may be
read out, bypassing the datapath, for off−chip analysis. The
automatic black level correction can be disabled and the
black level set manually via register settings. Manual black
level settings are frame synchronized to the next start of
frame.
Row and Column Correction
Row and column noise correction is applied automatically
by the image sensor on a frame by frame basis.
Re−triggering of correction circuits due to settings or
temperature changes are not necessary. The digital gain can
be applied before HDR linearization for white balancing,
and after HDR linearization for increasing scene brightness.
Defective Pixel Tracking/Correction
Defective Pixel Correction (DPC) is intended to
compensate or tag defective pixels by replacing their value
with a value based on the surrounding pixels, or tagging
them by assigning them a ‘0’ value. The defect pixel
correction feature supports up to 200 defects. The locations
of defective pixels are stored in a table on chip during the
manufacturing process; this table is accessible through the
two−wire serial interface. There is no provision for later
augmenting the defect table entries. The DPC algorithm is
one−dimensional, calculating the resulting averaged pixel
value based on nearby pixels within a row. The algorithm
distinguishes between color and monochrome parts; for
color parts, the algorithm uses nearest neighbor in the same
color plane. The defect pixel correction algorithm may be
disabled. (Note that the outgoing defect specification for the
AR0231AT assumes the defect correction is disabled). The
defect pixels identified during manufacture can be read from
on−chip ROM via the 2−wire control interface.
Analog/Digital Gains
A programmable analog gain of 0.125x to 8x applied
simultaneously to all color channels will be featured along
with a digital gain of 1x to 16x that may be configured on a
per color channel basis. Future releases will have an option
to separate the digital gain for use as an AWB function and
as a global gain.
Skipping/Binning Modes
The AR0231AT supports subsampling. Subsampling
allows the sensor to read out a smaller set of active pixels by
either skipping, binning, or summing pixels within the
readout window. Horizontal binning is achieved in the
digital readout. The sensor will sample the combined two
adjacent pixels within the same color plane. Vertical row
binning is applied in the pixel readout. Row binning can be
configured as two rows within the same color plane. Pixel
skipping can be configured up to two in both the x−direction
and y−direction. Skipping pixels in the x−direction will not
reduce the row time. Skipping pixels in the y direction will
reduce the number of rows from the sensor effectively
reducing the frame time. Skipping will introduce image
artifacts from aliasing. The AR0231AT supports row wise
vertical binning. Row wise vertical summing is not
supported.
CFA Type Identification
CFA type (e.g. RGB, mono, etc.) may be determined by
reading an identification register via the 2−wire control
interface.
ASIL/ISO26262 Support Features
The AR0231AT incorporates many features to assist
ASIL−B system compliance to be achieved by a system that
integrates it. Please refer to the AR0231AT Safety Manual
for more information.
