A simple combination of a street-lamp sodium vapour discharge tube and a high-frequency electronic drive ballast has been found to provide excellent performance in a specific machine vision system, where a line scan CCD detector required uniform, bright, narrowspectrum transillumination of a plastic film. The tube drive frequency was significantly higher than the scan rate of the CCD, so was effectively a DC source. The usual long life of this class of discharge tube seemed to be unaffected.

No abstract