Analysis and experimental study of ruled halftone screens

We have calculated the light intensity distribution behind ruled halftone screens of the type used in the graphic arts industry. The resulting formulas, which are derived from the theory of partial coherence, include diffraction effects at both the lens aperture and the screen. Their form is that of rapidly converging summations rather than expressions requiring numerical integrations for their evaluation. The method of solution is general in that it treats arbitrarily shaped lens apertures and both straightline and crossline screens with either conventional absorbing or transparent phase rulings. Theoretical predictions for the phase screen and a variety of circular apertures, wavelengths, and screen spacings agree very well with the experimentally measured intensity patterns.