Ilford Limited

Alan Hodgson

Neil F Ashford

Stephen R Postle

Peter M Blum

There is described a method of processing exposed holographic material to obtain holograms having a broader band replay a hologram which is of the silver halide in gelatin binder type which method comprises holographically exposing the holographic material by use of coherent light, developing the holographic image by a chemical process and then treating the material sequentially either firstly with a solution of an anionic surfactant which comprises at least one alkyl group having at least four carbon atoms and then with a solution of a quaternary ammonium compound which comprises at least one alkyl group having from 10 to 18 carbon atoms or a polymeric compound which comprises at least one quaternary ammonium group in the repeating unit or firstly with a solution of said quaternary ammonium compound or polymeric compound and then with a solution of an anionic surfactant, the material being subjected to a silver bleaching step at one stage after development. Preferably the anionic surfactant is present either in an acid stop bath after the development bath or in the bleach bath which is an acid bath. Then after the bleach bath the material is treated with the aqueous solution of the quaternary ammonium compound.

Production of holograms

A method of preparing a hologram which is of the silver halide in gelatin binder type which method comprises holographically exposing the holographic material by use of coherent light, developing the holographic image by a chemical process and wherein after development the material is treated with an aqueous solution of an anionic surfactant which comprises at least one alkyl group having at least four carbon atoms, to achieve bathochromic shift in the replay wavelength.

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Stockport, United Kingdom

Alan Hodgson