Basler A640F User Manual page 30

Basic Operation & Standard Features
Level Controlled Exposure Mode
When level controlled mode is selected, the length of the exposure will be controlled by the ExTrig
signal. If the camera is set for rising edge triggering, exposure begins when the ExTrig signal rises
and continues until the ExTrig signal falls. If the camera is set for falling edge triggering, exposure
begins when the ExTrig signal falls and continues until the ExTrig signal rises. Figure 3-5
illustrates level controlled exposure with the camera set for rising edge triggering.
Level controlled exposure is especially useful if you intend to vary the length of the exposure time
for each captured image.
Figure 3-5: Level Controlled Exposure with Rising Edge Triggering
When you operate the camera in level controlled mode, you are required to set an exposure time
by using the shutter setting as described in Section 3.2.1. In level controlled operation, the
exposure time determined by the shutter setting represents an absolute minimum time for each
exposure. For each full cycle of the ExTrig signal:
• If the exposure time as controlled by the ExTrig signal is less than or equal to the minimum,
the camera will use the minimum exposure time.
• If the exposure time as controlled by the ExTrig signal is greater than the minimum, the cam-
era will use the exposure time determined by the ExTrig signal.
Example 1: Assume that you set your camera for level controlled exposure with rising edge
triggering and that you set the shutter setting for a 2000 µs minimum exposure time. Now assume
that you triggered an exposure start by raising the ExTrig signal and that the signal remained high
for 1500 µs. In this case, the camera would have a 2000 µs exposure time because the ExTrig
high time was less than the minimum exposure setting.
Example 2: Assume that you set your camera for ExTrig level controlled exposure with rising edge
triggering and that you set the shutter setting for a 2000 µs minimum exposure time. Now assume
that you triggered an exposure start by raising the ExTrig signal and that the signal remained high
for 3500 µs. In this case, the camera would have a 3500 µs exposure time because the ExTrig
high time was greater than the minimum exposure setting.
When using level controlled exposure, you should adjust the shutter setting to set the minimum
exposure time to the shortest exposure you intend to use. For example, assume that you will be
using level controlled exposure and that you intend to use the ExTrig signal to vary the exposure
time in a range from 3000 µs and 5500 µs. In this case you would use the shutter setting to set
the minimum exposure time to 3000 µs.
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BASLER A640
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