CHEETAH Hardware User’s Manual
Imperx, Inc.
Rev. 6.2
6421 Congress Ave.
7/7/2015
Boca Raton, FL 33487
+1 (561) 989-0006
58 of 152
‘Very Bright’ Pixels:
The exposure period for the Very Bright pixels is set by
parameter E2. The Very Bright pixel exposure period is defined as the Total
Exposure Period (Texp) minus E2. For example, if Texp (Dark Pixel Exposure time)
is 50.0ms and it is desired to set the Very Bright pixel exposure period to 0.5ms,
then E2 must be set to 49.5ms. (50.0ms – 49.5ms = 0.5ms)
Tvb (Very Bright) = Texp – E2;
E2 is a value in microseconds and must have a value between the E1 exposure
period and Texp. The minimum E2 value is 2 micro-seconds. The amount of camera
output allocated to Very Bright pixels is set by parameter P3 which can have values
ranging from 15% to 100% of the camera output (16 steps) and must be greater than
P2. The Very Bright’ pixel data is contained between the P2 percentage of output
and the P3 percentage of output. See Table 2.6c. If P3 is set to 100%, then the
camera output is partitioned into three zones.
‘Ultra-Bright’ Pixels:
The exposure period for the Ultra-Bright’ pixels is set by
parameter E3. The Ultra- Bright pixel exposure period is defined as the Total
Exposure Period (Texp) minus E3. For example, if Texp (Dark Pixel Exposure time)
is 50.00ms and it is desired to set the Ultra-Bright Pixel exposure period to 0.05ms,
then E3 must be set to 49.95ms. (50.00ms – 49.95ms = 0.05ms).
Tub (Ultra-Bright) = Texp – E3;
E3 is a value in microseconds and must have a value larger than E2, but less than
Texp. The minimum E3 value is 2 micro-seconds. The amount of camera output
allocated to Ultra- Bright pixels is between the P3 setting and 100% of the camera
output.
Figures 2.11a-d is a single knee point demonstration of the WDR function. It is
useful to note how the output histogram changes as P1 is varied from 75% to 50% to
25%.
