Color holographic display based on single-layer monochromatic and panchromatic dichromated gelatin holographic recording materials

Jianhua Zhu
Sichuan university, China
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Three-dimensional color holographic display has important applications in visual representation of artworks, industrial products, museum items, medical images, etc., and has been always a long and diligent research goal for holographers and researchers. Through Slavich fine-grain silver-halide emulsion and Du Pont photopolymers have been successfully developed for color hologram recording, the research results of color holography based on dichromated gelatin material are still very limited. In this paper, we will summarize our recent results of color holographic display based on single-layer monochromatic and panchromatic dichromated gelatin materials. Firstly, based on the red sensitive methylene-blue sensitized DCG material, a new method is developed for the wide-range quantitative adjustment of the playback wavelength of Lippmann holograms. The main feature of this technique is homogenuously introducing a water-soluble organic reagent acrylamide into photosensitive layer as preswelling reagent and wavelegth adjuster, during the exposure process acrylamide will not react with other active reagents in DCG layer, but it will completely dissolve into water during the development process, this will result in an uniform shrink throughout the thickness of the photosensitive layer, and lead to the image reconstructed at shorter wavelength after the conventional dehydration process in isopropyl alcohol. By changing the concentration of preswelling reagent in the photosensitive layer, the final playback wavelength can be adjusted widely and quantitatively from red to green, and blue, almost covering all the visible spectral range. The quantitative investigations to derive the relationship between the wavelength shift and the concentration of preswelling reagent are reported in this paper. Secondly, by employing new types of multi-color photo-sensitizers and photochemical promoters to conventional photo-crosslinking DCG system, a high-quality single-layer panchromatic DCG material is achieved successfully in our laboratory. Its holographic recording characteristics such as spectral response, photosensitivity of three primary colors, angular and spectral selectivity of volume holograms are studied in detail. Summarily it has high diffraction efficiency (up to 85%), high spatial resolution (up to 5000 lines/mm), high photosensitivity (up to 20 mJ/cm2) for three-primary-color laser lines. Three-dimensional true-color reflection holograms with high color saturation and brightness are recorded successfully at the exposure level of 30 mJ/cm2 by using red, green and blue lasers. Some preliminary results of wavelength and angle multiplexed holographic storage using this material will also be given. We believe that it can be a new and good candidate for the practical applications such as true-color holographic display, wavelength multiplexing holographic storage, as well as holographic optical elements.