Daheng Imaging MERCURY USB3, Руководство пользователя

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8.Features
© China Daheng Group, Inc. Beijing Image Vision Technology Branch 115
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), the exposure time must
synchronize with the external light source (under 50Hz light source, the exposure time must be a multiple
of 1/100s, under 60Hz light source, the exposure time must be a multiple of 1/120s), to ensure better image
quality. You can set the exposure time that is synchronized with the external light source by using the demo
or interface function.
The MER-U3 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
8.3.4 for more details.
8.2.8. Overlapping Exposure and Non-overlapping Exposure
There are two stages in image acquisition of the MER-U3 series camera: exposure and readout. Once the
camera is triggered, it begins to integrate and when the integration is over, the image data will be read out
immediately.
The MER-U3 series camera supports two exposure modes: overlapping exposure and non-overlapping
exposure. The user cannot assign the overlapping exposure or non-overlapping exposure directly, it
depends on the frequency of trigger signal and the exposure time. The two exposure mode are described
as below.

Non-overlapping exposure
In non-overlapping exposure mode, after the exposure and readout of the current frame are completed,
then the next frame will expose and read out. As shown in the Figure 8-16, the N
th
frame is read out, after
a period of time, the N+1
th
frame to be exposed.
The formula of non-overlapping exposure frame period:
non-overlapping exposure frame period > exposure time + readout time
Sensor
Exposure
Time
Non-overlapping
Non-overlapping
Frame N Frame N+1 Frame N+2
Frame N
Frame N+1
Sensor
Readout
Blank Blank
Figure 8-16 The exposure sequence diagram in non-overlapping exposure mode

Trigger acquisition mode
If the interval between two triggers is greater than the sum of the exposure time and readout time,
overlapping exposure will not occur, as shown in Figure 8-17.