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1997
Conference Paper
Titel
Evaluation of camera data. Results of a round robin test
Abstract
The discussion of the standard draft ISO/CD 11 146 yielded some agreement within the laser community, that the beam radius should be determined from the second moments of the power density distribution (PDD). However, specially if beam properties are determined in the most straightforward manner from the evaluation of the digitised data of cameras and camera-like devices, ambiguous results may appear. For CCD camera systems offset or baseline ambiguity is the most prominent error source. Even after a dark image has been subtracted this offset level error may occur. In theoretical considerations an incorrect offset level causes divergent integral expressions due to infinite integration domains. In the evaluation of measured PDDs an incorrect offset yields severe errors in the moments. The error may be minimised by using cut-offs or thresholds. In addition to offset misalignment other sources of errors may occur which may either be common to all camera-like systems or specific for the ac tual device.