Production of amplitude gratings with preset black to white line width ratio

Abstract

A simple, cheap and practical method of producing photographic amplitude gratings with black to white ratio differing from unity is described. A 50% amplitude grating is illuminated by a light source of defined extent. The light intensity distribution at a certain distance behind this grating is recorded on high contrast photographic emulsion. The black to white ratio changes with illumination time. Based on the same principle, the grating frequency can be doubled without grating size reduction.