8.Features
© 2023 China Daheng Group, Inc. Beijing Image Vision Technology Branch 75
The time width of the flash signal can be got by the following formula:
T
strobe
=T
exposure
-
(
N-1
)×
T
row
8.2.11.3.
Set Exposure Time
According to the length of the exposure time, two exposure time modes of the MARS-GT camera are
available: Standard exposure time mode and UltraShort exposure time mode.
In Standard exposure time mode, three exposure time adjustment modes are available: manual
adjustment, one-time automatic adjustment and continuous automatic adjustment. The standard exposure
time mode is the default setting. For the manual adjustment, please refer to section 8.2.10.Overlap
Exposure and Non-overlap Exposure and one-time automatic adjustment and continuous automatic
adjustment please refer to section 8.3.6.Auto Exposure/Auto Gain.
In UltraShort exposure time mode, the MARS-GT camera only supports manual adjustment of the
exposure time. Since standard exposure time mode is the default setting, if you want to set the UltraShort
exposure time mode, you first need to adjust the visibility level to guru and set the ExposureTimeMode to
UltraShort under the acquisition control features window.
Note: In UltraShort exposure time mode, the MARS-GT camera does not support automatic
adjustment of the exposure time, only support manual adjustment of the exposure time.
8.2.11.4.
Set Value of Exposure Time
The MARS-GT series camera supports setting the exposure time, step: 1μs.
The exposure precision of the camera is limited by the sensor, when the steps in the user's interface and
the demo display as 1μs, actually the steps is one row period. When the value of the ExposureTime cannot
be divisible by the row period, round up to an integer should be taken, such as the row period is 21μs,
setting 80μs exposure time, and the actual exposure time is 85μs.
When the external light source is sunlight or direct current (DC), the camera has no special requirements
for the exposure time. When the external light source is alternating current (AC), it is recommended that
the exposure time is better to be integral multiple of the light source cycle, for example, for a 100Hz light
source, it is better to set the exposure time as an integral multiple of 10ms (the frequency of fluorescent
lamp we usually use is 50Hz).
The MARS-GT series 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 8.3.6 for more details.
8.2.12.
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.
