19.2 Improving the acquisition / image quality 147
19.2.1.2.1 Correcting Dark Current
The dark current correction is a pixel wise correction where the dark current correction image removes the dark
current from the original image. To get a better result it is necessary to snap the original and the dark current
images with the same exposure time and temperature.
Note
Dark current snaps generally show noise.
To correct the dark current pixels following steps are necessary:
1. Black out the lens completely
2. Set "OffsetAutoCalibration = Off" (Figure 3)
3. If applicable, change Offset_pc until you'll see an amplitude in the histogram (Figure 4)
4. Set exposure time according to the application
5. Set the (Filter-) "Mode = Calibrate"
6. Snap an image ("Acquire" with "Acquisition Mode = SingleFrame")
7. Finally, you have to activate the correction: Set the (Filter-) "Mode = On"
8. Save the settings including the correction data via "Action -> Capture Settings -> Save
Active Device Settings"
(Settings can be saved in the Windows registry or in a file)
The filter snaps a number of images and averages the dark current images to one correction image.
MATRIX VISION GmbH
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