Cheetah KAC Camera User Manual | Camera Link (CLF) Interface
October 1, 2019
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11
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Rev 7.2
Figure 2: Rolling Shutter Description.
In Rolling Shutter (RS) mode, each line of the image sensor is captured at a slightly
different time. This can cause distortions in the image if an object is moving very quickly
and the integration time is short with respect to the frame readout time. In rolling shutter
mode, pixels in a row are cleared of charge, allowed to integrate for the required
exposure time, and then read out of the entire line. The resetting of each line ripples
through the array and each line is exposed with a slight time delay (equal to the line
readout time) relative to the previous line. In RS mode, the global shutter transistor in
each pixel provides noise reduction.
1.2.1.2 A/D architecture and Blooming Suppression
The ON Semiconductor KAC-12040 and KAC-06040 image sensors have an analog to
digital converter on each column and built-in correction circuits that automatically
compensate and correct for fixed pattern noise within the image array. With an A/D
converter on each column of the imaging array, digitization occurs within each line time
rather than within a readout pixel time, which improves noise performance. Two rows are
read out simultaneously (one from the top of the array and one from the bottom of the
array) and, in this manual, this is referred to as “one line.” While the camera has 3000
rows in the active image area, there are only 1500 lines read out and while the C2880
camera has 2128 rows, only 1014 lines are read out. The total number of rows including
overhead readout of the C4080 camera is 3136 (1568 lines) and the C2880 camera is 2292
rows (1146 lines) The camera takes care of all the details of re-ordering the lines within
frame grabber memory.
The A/D converter architecture allows the user to select between 10 or 12-bit digitization.
The Cheetah C4080 supports both 10 and 12-bit digitization. In 12-bit digitization mode,
the A/D conversion time is longer than the minimum chip readout time and this reduces
maximum frame rates. In 10-bit digitization the A/D conversion time is reduced increasing
the maximum frame rate. The image sensor provides up to eight LVDS readout banks and
the time to readout one line from the image sensor is less than the time necessary to
output the data using Camera Link. The camera compensates for this mismatch in data
output rates by adding additional delay at the end of each line.
Each pixel within the imaging array has extremely robust anti-blooming suppression
eliminating classic ‘black sun’ artifacts present in other CMOS imaging arrays. The CMOS
