Cheetah KAC Camera User Manual | Camera Link (CLF) Interface
October 1, 2019
Page
104
of
135
Rev 7.2
Percentage of Output
Pixel Data
100%
Ultra-Bright Pixel
data
81%
80%
Very Bright Pixel
Data
61%
60%
Bright Pixel Data
31%
30%
Dark Pixel Data
0%
Table 23: Example of output data partitioning for intensity slopes.
As another example of the range of exposures possibilities, you could set the exposure
time for the pixels in the darkest region of the image at 33.0 milliseconds, consistent with
a 30 frame per second video rate. For Bright pixels within the scene, you could select an
exposure time of 3 milliseconds, and for Very Bright pixels, select an exposure time of 300
microseconds. The output will partition into three zones: one for Dark pixel exposure
data, one for Bright pixel exposure data, and one for Very Bright pixel data.
It is useful to set the wide dynamic range parameters using ratios. The overall entire
exposure period (Texp) is the time during which the dark pixels integrate to some value.
As an example, describe this time period as the quantity X and specify that 40% of the
output range is allocated to Dark pixel data. You might then set the exposure time for
Bright pixels to 5% of the overall exposure time (Bright pixel exposure is 0.05X) and
allocate 35% of the remaining output to these bright pixels. Finally, for the Very Bright
pixels within the scene, you might set the exposure time to 0.5% of the overall exposure
(Very Bright pixel exposure is 0.0025X). The camera allocates the remaining portion of the
output (25%) to these Very Bright pixels. In this way, the camera can support three
separate exposure times.
The following example (Figure 63) compares a single slope (normal CCD or CMOS camera)
exposure with a dual slope exposure in which Dark pixels integrate for the full exposure
time up to 30% of the camera output while Bright pixels integrate for only 10% of the
exposure time with 70% of the camera output partitioned to Bright pixel information.
