1. Field of the Invention
The invention lies in the art of hologram production and fabrication.
2. Description of Prior Art
Bleach solutions comprised of halide salts have been employed to increase the diffraction efficiency of photographically recorded three-dimensional interference patterns. Juris Upatnieks and Carl Leonard "Diffraction Efficiency of Bleached, Photographically Recorded Interference Patterns" Applied Optics, Vol. 8, No. 1,85 (1969). High diffraction efficiency holograms are obtained; however, these holograms are degraded upon prolonged exposure to visible light.
An alternative method of increasing the diffraction efficiency of similar materials is disclosed by R. L. Lamberts and C. N. Kurty "Reversed Bleaching for Low Flare Light in Holograms" Applied Optics, Vol. 10, No. 6, 1342 (1971). The process required special development prior to the application of a bleach comprised of an aqueous solution of potassium dichromate and sulfuric acid. It too yields holograms which degrade upon prolonged exposure to visible light.
H. Thiry, in his article "New Technique of Bleaching Photographic Emulsions and Its Application to Holography" Applied Optics, Vol. II, No. 7, 1652 (July 1972) discloses a process wherein the photographic emulsion is bleached by exposure to bromine vapors in a vacuum vessel and subsequently washed with water prior to drying. This process can be deemed an improvement over that disclosed by either Lamberts or Upatnieks however, it too is deficient in that the holograms degrade upon further exposure to visible light.
As holograms darken upon exposure to intensive light sources, there is a reduction of diffraction efficiency and light transmission which clearly limits their usefulness. Many investigators have sought to overcome this problem (See Scott L. Norman "Dye-Induced Stabilization of Bleached Holograms" Applied Optics, Vol. II, No. 5, 1234 (may 1972) and references cited therein, without apparent success. My process yields holograms which are stable with respect to printout characteristics while maintaining high diffraction efficiency and good image quality.