A method of speckle reduction in holography for 2-D objects with minimum recording area is presented. The image is incoherently synthesized from the hologram double recorded with a set of random phase plates.
Makoto Kato and Yoshihiro Okino, "Speckle Reduction by Double Recorded Holograms," Appl. Opt. 12, 1199-1201 (1973)