8.Features
© 2023 China Daheng Group, Inc. Beijing Image Vision Technology Branch 116
quality. You can set the exposure time that is synchronized with the external light source by using the
demo or interface function.
The MERCURY2 USB3 Vision camera supports Auto Exposure feature. If the Auto Exposure feature is
enabled, the camera can adjust the exposure time automatically according to the environment brightness.
See section 8.3.5 for more details.
8.2.11.
Exposure Delay
The exposure delay function can effectively solve the strobe delay problem. Most strobes have a delay of
at least tens of microseconds from trigger to light. When the camera is working in a small exposure mode,
the fill light effect of the strobe will be affected. The exposure delay is achieved by the strobe signal and
the delay of the actual exposure starting.
The unit of exposure delay is μs, the range is 0 ~ 5000μs, and the minimum value is 0.
Trigger Signal
Strobe Signal
Exposure Stage
T
fix_delay
T
exposure_delay
Figure 8-33 The exposure delay sequence diagram in overlaping exposure mode
When a hardware trigger signal is received to the sensor to start exposure, there is a small delay, which
is called the exposure delay and consists of four parts of time, as shown in Figure 8-34.
T1: The delay introduced by the hardware circuit when the external signal passes through the optocoupler
or GPIO. The value is generally in the range of several to several tens of μs. The delay is mainly affected
by the connection mode, driving intensity and temperature. When the external environment is constant,
the delay is generally stable.
T2: Delay introduced by the trigger filter. For example, if the trigger filter time is set to 50μs, T2 is 50μs.
T3: Trigger delay (trigger_delay), the camera supports trigger delay feature. If the trigger delay is set to
200μs, T3 is 200μs.
T4: The sensor timing sequence delay, the internal exposure of the sensor is aligned with the row timing
sequence, so T4 has a maximum row cycle jitter. The value of each sensor is different. Some products
with large delay time (several hundred μs or more) have additional configuration time counted in T4.
