Process for the production of lightfast phase holograms utilizing ammonium dichromate and gelatin as photosensitive recording material
AssigneeAgfa-Gevaert
InventorsHans Wehner, Manfred Kliemann
Life of this patent
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Abstract
Hardenable gelatine recording materials are used in a process for the production of lightfast phase halograms. The recording material is hardened by the exposure to light and sensitized with ammonium dichromate. After exposure, it is developed, dehydrated and hardened. Development is carried out in a desensitizing bath containing formaldehyde sulphite and is followed by hardening in a formalin solution. Dehydration is carried out in two successive stages. In the first stage, the material is treated with an aqueous isopropanol solution and in the second stage with a concentrated isopropanol solution to which formaldehyde is added.
Claims7
A process for production of light fast phase holograms
- using a recording material comprised of a light-sensitive material containing hardenable gelatin
- in which the recording material is
- preliminarily hardened in a solution of 3-30% aqueous formaldehyde for up to 10 minutes to provide a temporary hardening and then
- sensitized in a solution of from 1-10% ammonium dichromate
- holographically exposed whereby cross-linked areas are created in accordance with the interference pattern of the holographic exposure and then the exposed material is developed to provide a phase hologram therein,
- wherein the improvement comprises
- the next treatment of the material after exposure is subjecting the hologram to a strongly basic formaldehyde sulfite bath comprising a solution of 3 to 20% by weight of sodium sulphite (Na.sub.2 S.sub.2 O.sub.5) and 5 to 30% by weight of 30% formalin in water for a period to desensitize the ammonium dichromate sensitization of the recording material
- and then treating the desensitized material with a bath containing formaldehyde to harden the gelatin of the material and then
- irrigating with running water for 30 minutes to 1 hour to complete desensitization by washing out dichromate without altering the cross-linked condition in the gelatin,
- after which the exposed and developed material is dehydrated in a first stage with aqueous isopropanol solution and in a second stage with concentrated isopropanol solution to which formaldehyde has been added and dried,
- said process producing optically clear phase holograms having signal to noise ratios of 30 to 70.
Dependencies are inferred from the claim text.