Abstract: A method of preparing a reflection hologram which includes mounting a transmission hologram in register with a portion of transparent photosensitive holographic material there being present there between a filter to cut out zero order light transmitted through the transmission hologram, there being present on each side of an assembly which includes the hologram and the holographic material a light reflecting surface then causing a beam of light from a laser source to pass through a holographic optical element (H.O.E.

Abstract: A method of preparing a hologram which comprises subjecting holographic material to a holographic exposure, the holographic material comprising silver halide emulsion of which at least 80% by weight of the halide is bromide, developing the exposed material in a silver halide developing solution to yield developed silver, converting the developed silver to silver chloride using a bleaching agent selected from ferric ions, persulphate ions, chlorate ions, peroxides and water-soluble quinones, in the presence of chloride ions and then fixing out the silver chloride using a silver halide fixing agent which dissolves silver chloride but not silver bromide or silver iodobromide under the conditions of use.

Abstract: A method of preparing a hologram which comprises subjecting holographic material to a holographic exposure, the holographic material comprising a silver halide emulsion of which at least 80% by weight of the halide is bromide, developing the exposed material in a silver halide developing solution to yield developed silver, converting the residual silver bromide, in the main part at least, to silver iodide by use of an aqueous iodide solution, removing the developed silver but leaving the silver iodide either by use of a bleach/fix bath under controlled conditions or by rehalogenating the developed silver to silver bromide or chloride using a brominating or chlorinating silver bleach solution and simultaneously or subsequently fixing out the thus formed silver bromide or chloride using a fixing agent under such conditions that silver iodide is not dissolved from the material.