Usually, images and other signals are recorded on photographic media using either density modulation, as in ordinary photographs, or spatial pulse modulation, as in halftone image reproduction. This paper presents an analysis of a modulation technique that combines density and spatial modulation. It is shown that the technique studied can provide a large class of average-transmittance functions. This class includes linear, power, and logarithmic functions. Design formulas for screens that give these functions are derived. It is shown that the average-transmittance function of films exposed through a screen of this design is independent dependent exposure range.
© 1978 Optical Society of AmericaPDF Article