AR0130 Datasheet, PDF (29/53 Pages) ON Semiconductor – CMOS Digital Image Sensor

AR0130: 1/3-Inch CMOS Digital Image Sensor
Features
Gain
Digital Gain
Analog Gain
Digital gain can be controlled globally by R0x305E (Context A) or R0x30C4 (Context B).
There are also registers that allow individual control over each Bayer color (GreenR,
GreenB, Red, Blue).
The format for digital gain setting is xxx.yyyyy where 0b00100000 represents a 1x gain
setting and 0b00110000 represents a 1.5x gain setting. The step size for yyyyy is 0.03125
while the step size for xxx is 1. Therefore to set a gain of 2.09375 one would set digital
gain to 01000011.
The AR0130 has a column parallel architecture and therefore has an Analog gain stage
per column.
There are two stages of analog gain, the first stage can be set to 1x, 2x, 4x or 8x. This is can
be set in R0x30B0[5:4](Context A) or R0x30B0[9:8] (Context B). The second stage is
capable of setting an additional 1x or 1.25x gain which can be set in R0x3EE4[8].
This allows the maximum possible analog gain to be set to 10x.
Black Level Correction
Black level correction is handled automatically by the image sensor. No adjustments are
provided except to enable or disable this feature. Setting R0x30EA[15] disables the auto-
matic black level correction. 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 lines 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 new filtered average is then 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 correc-
tion value is increased by a predetermined amount. If it is above the maximum level, the
offset correction value is decreased by a predetermined amount. The high and low
thresholds have been calculated to avoid oscillation of the black level from below to
above the targeted black level. At high gain, long exposure, and high temperature condi-
tions, the performance of this function can degrade.
Row-wise Noise Correction
Row (Line)-wise Noise Correction is handled automatically by the image sensor. No
adjustments are provided except to enable or disable this feature. Clearing R0x3044[10]
disables the row noise correction. Default setting is for row noise correction to be
enabled.
Row-wise noise correction is performed by calculating an average from a set of optically
black pixels at the start of each line and then applying each average to all the active
pixels of the line.
AR0130 DS Rev. L Pub. 6/15 EN
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