Multiple multiple-exposure hologram.

The number of holograms that can be linearly superimposed on one photographic plate has two fundamental limits; one is the finite extent of the characteristic amplitude transmittance vs energy-of-exposure (Ta − E) film curve, and the other is holographic reciprocity law failure [ K. M. Johnson L. Hesselink J. W. Goodman , Appl. Opt.23, 218 ( 1984)], the chronological decrease in brightness of reconstructed images in a multiple-exposure hologram. In this paper a multistep hologram, called the multiple multiple-exposure hologram, is presented which increases the number of holograms that can be linearly superimposed on one photographic plate and reconstructs images of equal brightness. The brightness of the reconstructed images in the final display hologram is a function of the reference-to-object beam ratio K in the intermediate and final steps of the multiple multiple-exposure hologram. By choosing different values for K in each step of this technique, a cross section can be displayed with the same diffraction efficiency in the initial multiple-exposure holograms and the final multiple multiple-exposure hologram. The trade-off between the maximum number of holograms that can be linearly superimposed on one photographic plate and the signal-to-noise ratio in the final display hologram is also discussed.