Dalsa ML-FM-16K07A Manual page 83

Over Time, Pixels Developing Low Response
When flat field calibration is performed using a white reference, as per the guidelines in the user
manual, all pixels should achieve the same response. However, over time dust in the lens
extension tube may migrate to the sensor surface and reduce the response of some pixels.
If the dust particles are small, they may have only a minor effect on responsivity, but still create
vertical dark lines that interfere with defect detection and that need to be corrected.
Because repeating the flat field calibration with a white reference may not be practical while the
camera installed in the system, the camera has a feature where the flat field coefficients can be
downloaded to the host PC and adjusted using a suitable application, such as Microsoft Excel. (See
section Setting Custom Flat Field Coefficients for details.)
If the location of the pixel returning a low response can be identified from the image, then the
correction coefficient of that pixel can be adjusted, saved as a new file, and then uploaded to the
camera; thereby correcting the image without performing a flat field calibration.
See the user manual for details on downloading and uploading camera files using CamExpert.
Note: Dust accumulation on the lens will not cause vertical lines. However, a heavy
accumulation of dust on the lens will eventually degrade the camera's responsivity and
focus quality.
Appendix B: Troubleshooting Guide • 83