Control of cross-talk effects with pulse-width modulated pictures on orthogonal carriers

Theta modulation has been previously employed to encode a number of pictures on a given film area using sinusoidal carriers at various angles. This technique requires very close control of the photographic process and uses the film at intermediate densities where the grain noise is most pronounced. Pulse-width modulation greatly reduces grain noise and simplifies the photographic processing but is liable to give rise to cross talk. This can be minimized by reducing the modulation depth as far as the quality of the generating grid will permit. Pulse-width modulation also allows the use of a powerful new noncoherent method of separation based on a moire pattern of zero frequency.