8.Features
© 2023 China Daheng Group, Inc. Beijing Image Vision Technology Branch 86
will continuous adjust the gain value according to the data of the AAROI, so that the data in the AAROI is
kept near to the expected gray level.
The expected gray value is set by the user, and it is related to the data bit depth. For 8bit pixel data, the
expected gray value range is 0-255, for 10bit pixel data, the expected gray value range is 0-1023, and for
12bit pixel data, the expected gray value range is 0-4095.
The camera adjusts the gain value within the range [minimum gain value, maximum gain value] which is
set by the user.
The auto gain feature can be used with the auto exposure at the same time, when target grey is changed
from dark to bright, the auto exposure adjust is prior to auto gain adjust. Vice versa, when target grey is
changed from bright to dark, the auto gain adjust is prior to auto exposure adjust.
8.3.6.3.
Auto Exposure
The auto exposure can adjust the camera's exposure time automatically, so that the average gray value
in AAROI can achieve to the expected gray value. The auto exposure can be controlled by "Once" and
"Continuous" mode.
When using the "Once" mode, the camera adjusts the image data in the AAROI to the expected gray value
once, then the camera will close the auto exposure feature. When using the "Continuous" mode, the
camera will continuous adjusting the exposure time according to the data of the AAROI, so that the data
in the ROI is kept near to the expected gray level.
The expected gray value is set by the user and it is related to the data bit depth. For 8bit pixel data, the
expected gray value range is 0-255, and for 12bit pixel data, the expected gray value range is 0-4095.
The camera adjusts the exposure time in the range [minimum exposure time, maximum exposure time]
which is set by the user.
The auto exposure feature can be used with the auto gain at the same time, when target grey is changed
from dark to bright, the auto exposure adjust is prior to auto gain adjust. Vice versa, when target grey is
changed from bright to dark, the auto gain adjust is prior to auto exposure adjust.
8.3.7.
Test Pattern
The MARS-GT series camera supports three test images: gray gradient test image, static diagonal gray
gradient test image, and moving diagonal gray gradient test image. When the camera captures in RAW12
mode, the gray value of test image is: the pixel gray value in RAW8 mode multiplies by 16, as the output
of pixel gray value in RAW12 mode.
The following three test images are illustrated in the RAW8 mode.
GrayFrameRampMoving
In the gray gradient test image, all the pixels' gray values are the same in the frame. In the adjacent frame,
the gray value of the next frame increases by 1 compared to the previous frame, until to 255, and then the
next frame gray value returns to 0, and so on. A printscreen of a single frame is shown in Figure 8-34:
