Process for making high efficiency phase holograms

Claim 1

A process for the production of a phase hologram comprising the steps of: exposing silver halide photographic material in the exposure plane of a holographic optical system; developing the exposed photographic material with a non-tanning developer; treating the developed photographic material with a stopping agent consisting of a solution of 5-10% by weight of sodium sulfate (Na 2 SO 4 ) and 2-3% by weight of acetic acid (CH 3 COOH) having a pH value of from 2.8 to 3.2; rinsing the developed photographic material with deionized water having a pH value of 7; bleaching the developed photographic material with a tanning bleach solution having a range of pH values of from 2.2 to 2.7 and which includes 0.2% by weight of ammonium dichromate ((NH 4 ) 2 Cr 2 O 7 ) and 0.01-0.1% by weight of Potassium Bromide (KBr) which removes the silver of the metallic silver image areas while tanning the gelatin in the metallic silver image areas; rinsing the developed photographic material with deionized water having a pH value of 7; fixing the bleached photographic material with a non-tanning fixing solution containing 7-15% of weight of sodium thiosulfate (Na 2 S 2 O 3 ) having a pH value of 7 to remove the silver halide from the photographic material; washing the bleached and fixed photographic material in a 50/50 solution of water and isopropyl alcohol; dehydrating the bleached and fixed photographic material in a 100% solution of isopropyl alcohol; and drying the dehydrated material.