In this paper an approach will be developed for wavefront recording and reconstruction with a photographic plate when emulsion thickness is not uniform. It is shown that in a first approximation an emulsion thickness variation will not affect the wavefront recording. However, thickness variation does affect the hologram image reconstruction. It is found that a first-order thickness variation (wedge-shaped), except for a lateral translation of image coordinates, will not affect the precision of the reconstruction. However, a second-order variation not only affects the precise dimension of the image reconstruction but also causes an astigmatic effect in the hologram image.
A. D. Gara and F. T. S. Yu, "Effect of Emulsion Thickness Variations on Wavefront Reconstruction," Appl. Opt. 10, 1324-1328 (1971)