Multiple image subtraction by speckle interferometry

The usual techniques of random speckle coding can be used to obtain the difference between any two transparencies from a single photographic plate. The authors report that it is possible to obtain differences between a scene and subsequent different multiple input scenes from a single photographic plate. This is realized by making sequential exposures of the transparencies with a multiple aperture screen placed before the imaging lens system. The theory and experimental results with binary objects are presented.