A simple method of measuring the transverse stability of a microdensitometer is presented. The technique is based on a scan parallel to a straight edge using a square aperture such that the aperture partially overlaps the edge over a long distance in the scan direction. As the measured transmittance is linearly related to the width of the overlap of the aperture with the straight edge, it may be used to determine the displacement of the aperture relative to the edge during normal scanning operation. It was found that several commercial microdensitometers did not meet their stated specifications for positional accuracy.
Keywords: microdensitometer, position accuracy, scan stability, straight-edge scans
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