AW00123409000 Image Acquisition Control
Basler ace USB 3.0 131
and that you intend to use the ExFSTrig signal to vary the exposure time in a range from 3000 µs
to 5500 µs. In this case you would set the Exposure Overlap Time Max parameter to 3000 µs.
For more information about the Frame Trigger Wait signal, see Section 6.8.4.2 on page 168.
Trigger Width Exposure Mode for Cameras with Exposure Time Offset
Trigger width exposure is especially useful if you intend to vary the length of the exposure time for
each captured frame.
Some cameras provide an additional exposure time, the so-called exposure time offset (C
4
), that is
automatically appended to the user-controlled exposure time.
The following cameras provide an exposure time offset: acA640-750, acA800-510, acA1300-200,
acA1920-40, acA1920-150, acA1920-155, acA2000-165, acA2040-55, acA2040-90, acA2040-120,
acA2440-35, acA2440-75, acA2500-60.
Accordingly, when trigger width exposure mode is selected, the exposure time for each frame
acquisition is the sum of two individual time periods (see Figure 60):
The first time period is the exposure time that is controlled by the ExFSTrig signal: If the
camera is set for rising edge triggering, the first time period - and therewith the exposure time -
begins when the ExFSTrig signal rises. The first time period ends when the ExFSTrig signal
falls.
If the camera is set for falling edge triggering, the first time period begins when the ExFSTrig
signal falls. The first time period ends when the ExFSTrig signal rises.
The second time period is the exposure time offset, C
4
. It is automatically appended by the
camera’s sensor to the first time period. The length of the exposure time offset usually
depends on the bit depth of the current pixel format (8 bit, 10 bit or 12 bit) and, for some
camera models, on the currently available USB 3.0 bandwidth (expressed as "Device Link
Throughput").
For exposure time offsets, C
4
, and their dependencies, see Table 32 and Figure 59.
Note that C
4
is generally smaller than the camera’s minimum allowed exposure time. For the
cameras’ minimum allowed exposure times, see Table 33 on page 140 and Table 34 on page 141.
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