Photon Focus MV0 CMOSIS Series, Руководство пользователя, Страница: 59 / 111

11.2 Column FPN Correction
11.2 Column FPN Correction
Due to the readout structure of the image sensors there is a column-wise fixed pattern noise
(FPN). The Column FPN Correction (ColCorrection) adds or subtracts a fixed value to a column.
These values are obtained by a calibration process. The ColCorrection of the camera was
calibrated at Photonfocus production facility.
11.2.1 Enable / Disable the Column FPN Correction
The Column FPN Correction can be enabled or disabled with the property ColCorrection_Enable
(in category Photonfocus / ColCorrection ). By default the correction is enabled.
11.2.2 Calibration of the Column FPN Correction
The Column FPN Correction of the camera is correctly calibrated at Photonfocus production
facility. Although a new calibration is normally not required, you can recalibrate the Column
FPN Correction with the following instructions:
1. Setup the camera to the mode where it will be usually used. (Exposure time, ...). The
width and height should be set to its maximal value.
If different exposure times will be used, calibrate the camera under the longest
exposure time.
2. Start the aqcuisition of the camera.
3. Close the lens of the camera or put a cap on the lens. The calibration requires an uniform
dark image. The black level offset should be set so that all pixels (except defect pixels)
have values above 0.
4. Run the command ColCorrection_CalibrateBlack (category ColCorrection ) by clicking on
the corresponding button.
The calibration process needs some images in order to do the calibration. If the
camera is in triggered mode, the user must apply the corresponding triggers.
To get the best calibration results, the camera should have achieved the working
temperatur.
5. Run the command ColCorrection_Update by clicking on the corresponding button. Read the
ColCorrection_Busy value which should be 0 after the calibration has finished. Repeat this
step if its value is not 0. If the
ColCorrection_Busy
value doesn’t show 0 after various tries,
check if the camera receive triggers, when the triggered mode is activated.
6. Check the values of the properties ColCorrection_Overflow and ColCorrection_Underflow . Both
should have the value 0 after calibration. If ColCorrection_Overflow is not 0, then decrease
BlackLevel
(in category
AnalogControl
) and re-run the procedure from step 4 on. If
ColCorrection_Underflow
is not 0, then increase
BlackLevel
(in category
AnalogControl
) and
re-run the procedure from step 4 on.
7. The Column FPN correction is now calibrated. The calibration values are stored in the
camera’s RAM and these values are lost when the camera power is turned off. To store the
calibration values to permanent memory see Section 11.2.3.
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