Holographic optical elements recorded in silver halide sensitized gelatin emulsions Part 2 Reflection holographic optical elements

Abstract

Silver halide sensitized gelatin (SHSG) holograms are similar to holograms recorded in dichromated gelatin (DCG), the main recording material for holographic optical elements (HOEs). The drawback of DCG is its low energetic sensitivity and limited spectral response. Silver halide materials can be processed in such away that the final hologram will have properties like a DCG hologram. Recently this technique has become more interesting since the introduction of new ultra-fine-grain silver halide (AgHal) emulsions. In particular, high spatial-frequency fringes associated with HOEs of the reflection type are difficult to construct when SHSG processing methods are employed. Therefore an optimized processing technique for reflection HOEs recorded in the new AgHal materials is introduced. Diffraction efficiencies over 90% can be obtained repeatably for reflection diffraction gratings. Understanding the importance of a selective hardening process has made it possible to obtain results similar to conventional DCG processing. The main advantage of the SHSG process is that high-sensitivity recording can be performed with laser wavelengths anywhere within the visible spectrum. This simplifies the manufacturing of high-quality, large-format HOEs, also including high-quality display holograms of the reflection type in both monochrome and full color.

Study of reflection gratings recorded in polyvinyl alcohol/acrylamide-based photopolymer

“…Reflection holographic optical elements can be recorded, for instance, in silver halide sensitized gelatin emulsions [8] with good results, but this recording medium has a thickness of 7 μm, which is very low if the aim is to store a great number of holograms in the same volume of material, as in the case of a holographic memory.…”

Applications of Holographic Optical Elements and Systems

“…DCG (dichromated gelatin), [6] 은염감광제(silver-halide emulsion), [7] PR(photoresist), [8] 광굴절 결정(photorefractive crystal), [9] 포토 폴리머(photopolymer) [10] …”

Real-Time Colour Holographic Interferometry (from Holographic Plate to Digital Hologram)

“…Concerning the first ones, a specific treatment proposed by Kim, 2002, has allowed obtaining a gelatine contraction smaller than 20 nm by mixing 2 ml of glycerol in the last bath of ethanol (100% ethanol drying). One can mention that the treatment applied to the Russian plates includes about ten steps and it is very sensitive to the temperature and the PH of the solutions.…”