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8.Features
© 2023 China Daheng Group, Inc. Beijing Image Vision Technology Branch 163
8.4.7.1.
FFC Coefficient Calculation and Preview
Before the FFC coefficient is obtained, it is recommended to determine the aperture of the lens and the
gain of the camera. In the following cases, the coefficient needs to be re-calculated.
Lens is replaced
If the requirement for FFC accuracy is high (if the purpose is to correct the inconsistency of the pixels),
it is recommended to recalculate the FFC coefficient after modifying the gain of the camera
According to the FFC plugin, the process of obtaining FFC coefficient is shown in the figure below, and
the yellow part are optional steps. For details of the FFC plugin, please see section 9.2.
1. Acquisition Frame Count
2. Acquisition of Bright
Field Images
4. Preview
3. Execute FFC
Figure 8-78 The process of obtaining FFC coefficient
1.
Acquisition frame count: acquisition frame count for the bright field image to obtain the average image.
It is not a necessary step, generally the default value is used
If the image noise is high, it is recommended to increase the acquisition frame count
2.
Acquisition of bright field images: perform this function to complete the bright field image acquisition.
It is recommended to align the white paper or the flat fluorescent lamp (to ensure the same
amount of light in different areas of the sensor), and adjust the distance between the camera
and the white paper/flat fluorescent lamp to fill the entire field of view
Do not overexpose the image. The gray value of the brightest area of the brightfield is
recommended to be less than 250
The image should not be too dark. The gray value of the darkest area of the brightfield is
recommended to be greater than 20
It is recommended to control the bright field gray value by adjusting the exposure time or light
source, and do not adjust the aperture
3.
Execute FFC: Calculate the FFC coefficient using the acquired image. After execution, the
subsequent image automatically use the calculated factors for FFC.
4.
Preview: Preview the effect of the current FFC.