AR0130 Datasheet, PDF (30/53 Pages) ON Semiconductor – CMOS Digital Image Sensor

AR0130: 1/3-Inch CMOS Digital Image Sensor
Features
Column Correction
The AR0130 uses column parallel readout architecture to achieve fast frame rate.
Without any corrections, the consequence of this architecture is that different column
signal paths have slightly different offsets that might show up on the final image as
structured fixed pattern noise.
AR0130 has column correction circuitry that measures this offset and removes it from
the image before output. This is done by sampling dark rows containing tied pixels and
measuring an offset coefficient per column to be corrected later in the signal path.
Column correction can be enabled/disabled via R0x30D4[15]. Additionally, the number
of rows used for this offset coefficient measurement is set in R0x30D4[3:0]. By default
this register is set to 0x7, which means that 8 rows are used. This is the recommended
value. Other control features regarding column correction can be viewed in the AR0130
Register reference. Any changes to column correction settings need to be done when the
sensor streaming is disabled and the appropriate triggering sequence must be followed
as described below.
Column Correction Triggering
Column correction requires a special procedure to trigger depending on which state the
sensor is in.
Column Triggering on Startup
When streaming the sensor for the first time after power-up, a special sequence needs to
be followed to make sure that the column correction coefficients are internally calcu-
lated properly.
1. Follow proper power up sequence for power supplies and clocks
2. Apply sequencer settings if needed
3. Apply frame timing and PLL settings as required by application
4. Set analog gain to 1x and low conversion gain
5. Enable column correction and settings
6. Disable auto re-trigger for change in conversion gain or col_gain, and enable column
correction always. (R0x30BA = 0x0008).
7. Enable streaming (R0x301A[2] = 1) or drive the TRIGGER pin HIGH.
8. Wait 9 frames to settle. (First frame after coming up from standby is internally column
correction disabled.)
9. Disable streaming (R0x301A[2] = 0) or drive the TRIGGER pin LOW.
After this, the sensor has calculated the proper column correction coefficients and the
sensor is ready for streaming. Any other settings (including gain, integration time and
conversion gain etc.) can be done afterwards without affecting column correction.
Column Correction Retriggering Due to Mode Change
Since column offsets is sensitive to changes in the analog signal path, such changes
require column correction circuitry to be retriggered for the new path. Examples of such
mode changes include: horizontal mirror, vertical mirror, changes to column correction
settings.
When such changes take place, the following sequence needs to take place:
1. Disable streaming (R0x301A[2]=0) or drive the TRIGGER pin LOW.
2. Enable streaming (R0x301A[2]=1) or drive the TRIGGER pin HIGH.
3. Wait 9 frames to settle.
AR0130 DS Rev. L Pub. 6/15 EN
30
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