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The 1964 publication by Emmett Leith and Juris Upatnieks [J. Opt. Soc. Am. 54, 1295 (1964)] introduced the possibility of using holograms to record three-dimensional (3D) objects. Since then, there has been an interest in creating display holograms, i.e., holograms primarily produced to show objects in 3D. More recently, full color holography has become a reality, which was predicted in the 1964 paper. To record a hologram in which both the 3D shape and the color of the object are accurately reproduced, at least three laser wavelengths are needed. By computer simulation of the holographic color rendering process, the required amount of laser wavelengths and their distribution within the visible electromagnetic spectrum have been investigated. The quality of a color hologram also depends on the properties of the recording material. The demand on a panchromatic material for color holography is described. Recording techniques for color holograms are presented as well as the future of color holography as the perfect 3D imaging technique.

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We describe a new method for imaging with visible and near visible light inside media, such as tissues, which have strong light scattering. The chrono-coherent imaging (CCI) method is demonstrated in this paper for a transmission geometry where an absorbing object is completely hidden from normal visual observation by light scattering of the media. The resultant images are most similar to X rays, with cumulative transmission showing absorption features and refractive index differences in the media. We discuss laser coherence properties, coherence measurements, the relation of CCI to light-inflight holography, holographic film properties relevant to CCI, a particular optical setup for CCI, the results of a demonstration experiment imaging an absorbing object hidden by light scattering, and an experiment to estimate the clinical applicability of CCI.

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.

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Silver halide sensitized gelatin (SHSG) holograms are similar to holograms recorded in dichromated gelatin (DCG), the main recording material for holographic optical elements (HOE's). The drawback of DCG is its low sensitivity and limited spectral response. Silver halide materials can be processed in such a way that the final hologram will have properties like a DCG hologram. Recently this technique has become more interesting since the introduction of new ultra-high-resolution silver halide emulsions. An optimized processing technique for transmission HOE's recorded in these materials is introduced. Diffraction efficiencies over 90% can be obtained for transmissive diffraction gratings. Understanding the importance of the 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 HOE's.

No abstract