Determination of Distortion in Scanned Images by Moiré Patterns

Distortions in TV displays can be traced to distortions of the camera lens, the camera or display raster, or a misalignment between the two rasters. Needs in the near future for higher resolution TV with less distortion will necessitate more accurate scan pattern linearity measurement. If a conventional display scan pattern is examined through a matching stationary film line grating, a moiré interference pattern is produced showing scan line distortions in a vertical direction. Almost any regular scan pattern can be examined by viewing the scan pattern through an undistorted reference film transparency and noting the interference pattern. If a dot pattern equal to the limiting resolution of the TV system is used both as a camera scene and display reference transparency, fringe interference patterns representing both horizontal and vertical distortions are obtained. — A method is proposed and preliminary test results shown to measure the linearity of a TV system. For closed-circuit TV applications, a direct comparison of camera and monitor rasters can be made. Both vertical and horizontal linearity can be determined within one reference film element. Localized variations of display scene linearities can be found so that compensation circuits can be adjusted.

Print ISSN

0361-4573

Published

1970-09

Content type

Original Research

DOI

10.5594/J16685