Cheetah Pregius Camera with 10 GigE Vision Interface – User Manual
October 8, 2020
Page
115
of
170
Rev 1.0
Automatic Exposure and Gain Control
Automatic exposure control (AEC) and automatic gain control (AGC) enable the camera to
maintain the same image brightness during the changing lighting conditions. You can enable
both AEC and AGC independently or together by setting
ExposureAuto
and
GainAuto
to either
Once
or
Continuous
.
AEC/AGC Mode
Description
Off
AEC/AGC is disabled and a manual control is on. The camera applies the exposure
time and gain you enter using the
ExposureTime
and
Gain
controls.
Once
Exposure duration/gain is adapted once by the camera. Once it has converged, it
returns to the Off state; and the exposure and gains determined during the Once
process are maintained until changed manually.
Continuous
Exposure duration/gain is constantly adapted by the camera to maximize the
dynamic range.
When AEC / AGC are in
Continuous
or
Once
mode, you can set the image luminance (brightness)
target (
ExposureGainAutoTarget
), and the camera adjusts the exposure and/or gain accordingly.
The luminance target is a 12-bit value (4095 is a max. value). To determine the luminance target
when using 8-bits per pixel, take the desired output in ADUs and multiply this value by 16. The
target luminance is the average luminance within the image.
Also, for the
Once
mode, you can set an acceptable difference between the target and current
image luminance (
ExposureGainAutoTargetThreshold
) in the range from 0 to 4095. When the
threshold is reached, the camera turns off AEC/AGC algorithms and enables manual control over
exposure duration and/or gain.
In some rapidly changing and bright light conditions, an image
brightness oscillation (image intensity flipping from bright to
dark) could occur. To prevent this, increase the AEC minimum
exposure setting, increase the target luminance level and/or
decrease the lens iris.
Initial conditions for AEC and AGC algorithms:
Exposure and gain are set to the user-specified values of the
ExposureTime
and
Gain
controls.
When AEC and AGC are enabled together, you might need to select whether to adjust gain or
exposure first using
ExposureGainAutoPriority
control.
•
If the
exposure priority
is selected (
ExposureTime
), the camera adjusts the exposure first
within the user-specified minimum/maximum limits. If one of the limits is reached before
the target image luminance (or threshold) is achieved, then gain is applied. The camera
varies the gain until either the target image luminance (or threshold) is reached or one of
gain limits is reached.
•
If the
gain priority
is selected (
Gain
), the camera adjusts the gain first within the user-
specified minimum/maximum limits. If one of the limits is reached before the target image
