We describe a general pipeline for the computation and display of either fully-computed holograms or holographic stereograms using the same 3D database. A rendering previewer on a Silicon Graphics Onyx allows a user to specify viewing geometry, database transformations, and scene lighting. The previewer then generates one of two descriptions of the object--a series of perspective views or a polygonal model--which is then used by a fringe rendering engine to compute fringes specific to hologram type. The images are viewed on the second generation MIT Holographic Video System. This allows a viewer to compare holographic stereograms with fully-computed holograms originating from the same database and comes closer to the goal of a single pipeline being able to display the same data in different formats.

Now we propose a new type of electro-holography such as the head mount display (HMD) type holography TV. According to the usual projection method the viewing angle is too small and long distance is necessary for observing the reconstructed image. In this paper we propose the eye-lens type holography to realize the HMD type 3D TV and discuss about the field angle, image size and observing distance. It was made clear that in this stage eye-lens type holography is effective to realize the 3D display even though the eye position is fixed.

Computation for synthetic holography typically takes one of two forms: the `stereogram' approach, in which a large number of 2D perspective views are rendered and assembled into a composite fringe pattern; and the `fully computed' approach, in which the physics of light propagation from geometric surfaces and the resulting interference patterns at a recording plane are all simulated. Algorithms implementing the stereogram approach often generate their component perspective views by taking advantage of dedicated graphics hardware, capable of rapid rendering with hidden- surface removal and smooth shading. However, these standard computer graphics schemes for occlusion and shading are inappropriate for fully computed hologram synthesis. We describe an efficient algorithm that starts with a standard- form geometric description of the desired scene and generates a list of simple holographic `primitives' that can be transformed into the final interference pattern by a simple fringe rendering program. The algorithm simultaneously performs the multiple-viewpoint equivalent of hidden surface removal, so that nearer surfaces and objects properly occlude those more distant, and surface shading, so that each object appears solid and exhibits the correct visual behavior in response to lighting in the scene.

Lightforest is a large-scale holographic work permanently installed at the MIT Museum in Cambridge MA. Organic shapes in the rounded walls and floor of a small room (15 by 10 by 9 feet) frame the approximately 200 white-light transmission or rainbow holograms of fabricated rainforest plants combined with light and image projections. Sound and computer-controlled lighting and the use of motion and proximity sensors enhance viewer interaction. Primary funding of Lightforest came through an AT&T Foundation's New Experiments in Art and Technology initiative. An outgrowth of the project has been the creation of a Holography Teaching Program at the MIT Museum, The Lightforest installation makes important connections between art, technology, education, and the environment.

A display system requiring no special glasses is a useful technology for 3D images. In this paper, two types of real- time 3D displays using a holographic screen instead of a lenticular screen are described. One is a stereoscopic 3D display system with viewing apertures such as conventional two-step holographic stereogram. The other is a stereoscopic 3D display system based on a reconstruction of parallax- rays. These systems consist of a liquid crystal device and a holographic screen formed on holographic optical elements. These systems can construct animated 3D images in real-time by updating LCD pixels.

A new method of 3D image formation is proposed. A 3D image is generated in this case by a matrix of aspects of a 3D scene that are focused in spots. The matrix is formed by a laser scanning beam in which the aspects of the scene are introduced in consecutive order. As a result the observer sees on the screen a 2D image whose configuration changes depending on the position of the eye in such a way as if the observer examines the real 3D object. The optical scheme of AFS Display (Aspect-Focused-in-Spot Display) is presented and the mechanism of 3D image formation is considered. The results of the experiment on modeling a 3D image which is formed by a scanning spot of light that projects the aspects of the scene are given. The experiment has been carried out as applied to the case of projection of a 3D image that reproduces the horizontal parallax only. It is pointed out that the display considered is compatible with existing TV system. It is supposed that it can be used as a 3D computer display, for 3D imaging in educating, medicine, flight and car training and so on.

Just as we expect holographic technology to become a more pervasive and affordable instrument of information display, so too will high fidelity force-feedback devices. We describe a testbed system which uses both of these technologies to provide simultaneous, coincident visuo- haptic spatial display of a 3D scene. The system provides the user with a stylus to probe a geometric model that is also presented visually in full parallax. The haptics apparatus is a six degree-of-freedom mechanical device with servomotors providing active force display. This device is controlled by a free-running server that simulates static geometric models with tactile and bulk material properties, all under ongoing specification by a client program. The visual display is a full parallax edge-illuminated holographic stereogram with a wide angle of view. Both simulations, haptic and visual, represent the same scene. The haptic and visual displays are carefully scaled and aligned to provide coincident display, and together they permit the user to explore the model's 3D shape, texture and compliance.

Color reflection holograms recorded with the Denisyuk geometry have been demonstrated by the recently formed HOLOS Corporation in New Hampshire. The Slavich red-green-blue (RGB) sensitized ultra-high resolution silver halide emulsion was used for the hologram recording. The employed laser wavelengths were 647 nm, 532 nm, and 476 nm, generated by an argon ion, a frequency doubled Nd:YAG, and a krypton ion laser, respectively. A beam combination mechanism with dichroic filters enabled a simultaneous RGB exposure, which made the color balance and overall exposure energy easy to control as well as simplifying the recording procedure. HOLOS has been producing limited edition color holograms in various sizes from 4' X 5' to 12' X 16'. A 30 foot long optical table and high power lasers will enable HOLOS to record color holograms up to the size of one meter square in the near future. Various approaches have been investigated in generating color hologram masters which have sufficiently high diffraction efficiency to contact copy the color images onto photopolymer materials. A specially designed test object including the 1931 CIE chromaticity diagram, a rainbow ribbon cable, pure yellow dots, and a cloisonne elephant was used for color recording experiments. In addition, the Macbeth Color Checker chart was used. Both colorimetric evaluation and scattering noise measurements were performed using the PR-650 Photo Research SpectraScan SpectraCalorimeter.

This report is concerned with several display systems for making 3D image fluctuate. These systems aim to reconstruct rainbow hologram images moved dynamically. The first method is using small motors for drifting an illumination and swinging a reflection mirror. The second method is using an electric fan for flapping a film hologram hung with rubber strings. The third method is using a liquid crystal display (LCD) projector controlled by a computer and a screen sized reflection panel composed of many small mirrors. In the last case, the small beam out of the LCD projector is reflected on a mirror of the reflection panel and illuminates the hologram panel. The hologram image generated by each small mirror has its particular property that is slightly different each other; shape, position and color. The highlight pattern of the beam projected on the reflection panel is moved by the computer program. When the pattern is fluctuated by the computer program, the position and color of the generated hologram image fluctuate accordingly.

In the evolution of synthetic holography as a viable medium for industrial design and scientific visualization, the inclusion of full parallax represents a logical next step from the previous horizontal parallax-only approaches. The significant increase in full-parallax information content implies the need for high speed perspective view synthesis, optimized mechano-optical recording systems, and novel hologram illumination approaches. This paper outlines recording techniques for producing full-parallax holographic stereograms of computer-synthesized and acquired data. We document on-the-fly high-speed rendering software that integrates the printing and image-synthesis steps. In the interest of hologram printer size control, approaches for optical image plane enlargement are highlighted, and successful examples of A4-size (30 cm X 21 cm) full- parallax images are presented. We assess perspective-view array and image-plane pixel resolutions and their effect on overall image quality, in particular with respect to medium- size formats. Finally, we demonstrate optimized illumination techniques for controlling image clarity, including dispersion-compensated and edge-illuminated approaches.

Simpler and easier sampling method which is one of the most important parameter required for making holographic stereograms is presented to reconstruct the images from transfer hologram. Instead of fringe-by-fringe sampling method which is difficult to apply in recording holographic stereograms, a new geometrical method is proposed for easier calculation of the sampling numbers. When the slit size is fixed under human pupil size, one can see the full 2D image through a slit. Dividing the distance between the two pupils by slit size, it determines the sampling numbers which are needed for recording. The angle difference of the real object becomes a binocular parallax. And the series of these 2D images are recorded on the master hologram. After processing, it transfers to transfer hologram. As a result, two images which exactly correspond to the places of viewer's eyes can be seen simultaneously. Because the object is taken at different angle and these two images are observed simultaneously, it makes us feel as a real object.

It is well known that unproper sampling of discrete perspective images can result in readily visible artifacts. Previous work has used partial coherence theory to calculate the characteristics of sampled perspective imaging in the case where the viewer's pupil coincides with the perspective window. I now apply the same formalism to treat the general case where the viewer position is independent of the perspective window. This allows the theory to be used in the treatment of generalized holographic stereograms (ultragrams) and other unconventional geometries.

This paper presents a computer graphics algorithm useful for rapidly generating image data for full parallax spatial displays such as full parallax holographic stereograms. Other techniques such as custom-designed ray-tracing packages and image-based rendering techniques have significant disadvantages for rapid display production. In contrast, the method described here uses scanline-based computer graphics techniques. The described implementation uses the widely available OpenGL^TM graphics library and takes advantage of acceleration by computer graphics hardware subsystems. The time required to render the image data of a moderately-sized scene for a single holographic exposure is less than one second using desktop computer systems. This method is compatible with both one-step and master-transfer holographic recording geometries. Details of the algorithm are included.

The average Nusselt number of a heated sphere rotating in quiescent air was measured experimentally over the range 0 < Re < 33320 from free to forced convection regimes. As well, real time holographic interferometry was applied to the observation of flows structure and evolution, and later employed to analyze the deviations revealed by a comparison of the measured data Nu with previous experimental and theoretical results. Thus, real time holographic visualization provides a physical understanding of the effect of the evolving flow structure on Nu as rotational speed increases. In addition, a new asymptotic formula for correlating the experimentally measured Nu was established.

Holographic Interferometry (HI) has been utilized in industry to inspect material for defects or the dynamic characteristics of a laminated structure. Application of the HI technique for biomedical diagnostic instrumentation was also reported. For detection of breast lesions, which could lead to breast cancer, we have utilized the HI technique to create a superficial fringe contour distortion over the underlying lesion. In the HI technique, an appropriate stressing mechanism is crucial to obtain proper density and contrast of fringe patterns. To apply pressure as the stressing mechanism, we have designed the Lucite pressure chamber to enclose both of the subject's breasts. Preliminary results have demonstrated the feasibility of fringe distortions occurring around breast lesions. The location of the possible lesions have been compared with an X-ray mammography.

We present a new holographic display system that reconstructs the complex hologram (which is free from the bias and the conjugate image) obtained from the modified triangular interferometer. This system is based on the Mach- Zehnder interferometer with modification of inserting liquid crystal displays (LCDs) and a wave plate. The information of the real and imaginary parts of the complex hologram are transferred to LCDs and the lights passed through LCDs are recombined by a beam splitter. By Fresnel diffraction, the desired image is reconstructed. We demonstrated through theoretical analysis and experiments that the image reconstruction from the complex hologram is possible using the proposed system.

A new method of making a reflection type holographic screen with use of a retroflex plate is presented. This method allows to use very simple optics compared with the mirror method. Some of optical parameters of the screen are derived by paraxial ray approach. A holographic screen made by a retroflex plate from 3M company, USA, demonstrates its potentiality as an image projection screen. The optical characteristics of the screen can be determined by the recording set-up parameters.

Holographic screen is an optical element of special kind with the directed light scattering, so that each pixel of the projected image on the screen sends light only in one observers eye (viewing zone). It is possible to record the holographic screen of two types: the reflection type screen and the transmission type one. In this paper the problem of compensation of high spectral dispersion of the transmission type holographic screen is considered. To overcome this problem the diffuse scatterer in the form of narrow long stripe, stretched in the direction to the reference beam axis, has been used. In order to simplify the recording setup, the large size holographic screen has been recorded with the diverging reference beam, because it is possible in this case to use small size optics. Experimentally the transmission type holographic screens have been recorded on the photoplates `Ilford' and PFG-01 (Russia). The screens have been used to display the stereoscopic and multiview color images from the slide-projector. The screen size was 30 X 40 cm. There is possibility to increase the screen size, if it is represented as mosaic of subscreens, each of them being recorded so, to minimize its aberrations.

A general recording model of in-line far-field holography is first proposed, which includes three illumination modes: divergent, convergent and collimated beam illuminations. The general irradiance distribution on a hologram is then derived from the general recording model. Based on the general irradiance distribution of in-line far-field holography, the analytical solutions of recordable depth of view (RDV) and allowable farthest far-field distance (AFFD) of in-line far-field holography have been given for different illumination modes. The analytical solutions of RDV and AFFD show that AFFD can be not limited if micro- objects are positioned in one special space and illuminated by convergent beams, but RDV isn't improved. When micro- objects are placed in another special space and illuminated by divergent beam, the RDV and AFFD can be improved simultaneously, but recording object space is split into two sub-spaces. These results are very important for the design of holographic recording system.

It is well known that photoresist undergoes a chemical change on exposure which results in a variation in its refractive index. In the recording of diffraction gratings this index change leads to a detectable phase grating before development: the so called latent image. The growth of the grating may be observed in real time by monitoring the diffraction efficiency of the first order beam from this latent image. By superposing the diffracted beams from two such latent gratings a moire pattern may be observed, from which the position of the fringes of one grating relative to the other may be obtained. If one of the gratings is moved relative to the other then this pattern may be used as the trigger for an optical exposure, and gratings may be written to cover a length independent of the size of the exposing beams.

Holographic optical elements with several optical functions recorded in a single layer have advantages in many applications. They have been difficult to fabricate because when they are recorded simultaneously in a single layer, spurious holograms are formed from the crosstalk between the recording beams. For some materials, sequential recording is a solution, but the mobile nature of photopolymer materials during recording prohibits the usual sequential techniques. The result has been that the crosstalk problem has required such holograms to be made from multiple layers causing both increased cost and reduced performance. This paper describes a method of recording such multiple elements in a single layer that completely eliminates such crosstalk holograms. The beams that form each hologram function included in the element are shuttered on in pairs for short intervals. Only the recording beams that form a desired hologram are present at any given time. No crosstalk occurs, since no unwanted beams are ever present. All holograms grow at the same rate as they each in turn receive short exposures. The round of exposures is repeated many times until they are all fully exposed. By keeping each round's exposures short, all holograms form essentially simultaneously, ensuring that they all see nearly the same recording material characteristics at the same stage of their development. This equalizes the recording of each element, even though the characteristics of the recording material change drastically and nonlinearly during the recording.

Photopolymer films developed by DuPont have excellent features as volume hologram recording material including high resolution, high diffraction efficiency, full color recording capability and fabrication with all dry processing. We have prepared several types of HOEs by using the films to implement designed function such as high power, multi-color recording and controlling of the diffraction bandwidth. To accomplish them, direct and precise knowledge of the fringe pattern such as slant angle and fringe space was strongly required. We have developed a new technique for the observation of the fringe pattern by scanning electron microscope (SEM) with an aid of Iodine dying pre-treatment (IDT-SEM). It is thought that Iodine is preferentially adsorbed at double bondings in unpolymerized monomers, which leads to a presumption that Iodine distribution detected by SEM accurately reproduce the refractive index modulation in volume hologram. This has been confirmed experimentally by the observation that fast Fourier transform analyses of SEM images for single, two and three color recorded HOEs are good agreement with optical spectra of the HOEs. The SEM image provides us the spatial information of both fringe space and slant angle with good resolution. This technique has been further applicable to other type of HOEs.

The recording of color holograms often leads to disappointing results in terms of low color saturation. The reasons for this can be largely attributed to the recording of travelling waves in a situation requiring that only standing wave patterns place demands on the dynamic range of the recording medium. This paper discusses some routes to avoiding this issue and also outlines the important problem of loss of color saturation in contact copying from reflection master to reflection copy using scanning techniques.

Multicolor display holography has been described by using some different techniques. Those that allow white-light viewing of the final hologram generally involve several stages, some requiring accurate registration. The recording technique, the recording material and the processing are all important parts of the final color hologram. Various special techniques allow the production of holograms exhibiting different colors. Color control for reflection holograms usually implies the preswelling of the emulsion before the recording. In this paper we will describe different methods of obtaining different colors for reflection holography on silver halide photographic emulsion by means of chemical methods, other than the preswelling. By using a He-Ne laser at 632.8 nm for the recording, we can achieve a range of reconstruction wavelength from 550 nm to 700 nm by using different developments and bleachings as well as different temperatures during the processing. By measuring the coordinates of each point recorded, we will find its right wavelength. Thus, comparing them to those of the CIE diagram, we will know the exact location of each color in the horseshoe shape. This will allow us to choose the desired color and repeat it in the conditions previously experimented.

DuPont has developed photopolymer materials for recording volume phase holograms. These unique materials record the complete wavefront of light from an object as a periodic refractive index modulation throughout the thickness of the film. Materials have been designed and developed for reflection and transmission holograms for a variety of applications. Recently, new materials with panchromatic sensitivity, designed specifically for color display holography, have been developed. This paper presents DuPont's new color material designed for reflection display holography. An overview of the recording mechanism, holographic performance, and process of use is given. Experimental color balancing results are discussed, and performance is compared to that of a film with different color balancing characteristics.

The formation of infrared holograms at a wavelength of 10.6 microns based on a thermal process that produces thermal bleaching, optical activation or surface deformation of different recording materials has been investigated over the last thirty years. This paper will review most of the known infrared recording media and identify materials with potential interest for specific applications.

Thick-layered self-developed glycerol-added dichromated gelatin has been suggested for the recording of volume holograms. The thickness of the layers varied from 0.4 to 0.6 mm. The diffraction efficiency is equal to 30% at the exposure about 5 J/cm².

PVA films have been used as mold releases, strippable coatings, binders for photopolymers and when sensitized with metals and/or dyes they have been used as photoresists, volume HOEs, multiplexed holographic optical memory and real time non destructive holographic testing. The list goes on and includes Slime and birth control. In holography, DC-PVA is a real time photoanisotropic recording material useful for phase conjugation experiments and also a stable long term storage medium needing no processing other than heat. Now we add the capability of greatly increasing the versatility of PVA by boosting the index modulation by almost two orders of magnitude. We can add broadband display and HOE applications that were not possible before. Simple two or three step liquid processing is all that is required to make the index modulation grow.

Holograms in dichromated gelatin (DCG) are of potential interest in many technical sectors. The current technology facilitates the manufacturing of large format (1 m²) holographic optical elements (HOE) operating between 400 nm and 2000 nm for various applications: photovoltaic two color solar concentrators, holographic stacks for daylighting and wideband passive shading devices for sun control, as well as spectrally matched concentrators for solar chemistry. For all these applications the optical properties of the HOEs have to be controlled carefully. By precise control of all the necessary manufacturing steps this can be achieved. The developing process has an high impact upon the optical properties of the HOE. Therefore, an excellent knowledge of the effect of the process on the inner structure of the gelatin is essential for achieving the desired optical properties. In this paper we describe the influence of the different developing baths and of the exposure energy on the inner structure of holograms in DCG. With increasing dehydration speed the swelling gradient becomes larger leading to broader reflection holograms and to asymmetric angular spectra of transmission gratings. With increasing exposure energy saturation of the refractive index modulation is attained. Higher exposure energies lead to a deformation of the refractive index profile and even `thick' transmission gratings exhibit higher diffraction orders with significant efficiencies. Models for the deformation of the refractive index profile and for inhomogeneous swelling across the layer of transmission holograms are presented. Theoretical simulations are compared to experiments and show excellent agreement.

We describe novel organic compounds based on polyester and peptide backbones with azobenzenes in the side chain for erasable holographic storage. These materials exhibit high diffraction efficiency, high resolution and long storage life and can be used for holographic storage in a broad spectra window of 415 - 530 nm. In polyester thin film systems with a chiral azobenzene, diffraction efficiencies of about 50% have been achieved with just 300 ms exposure. Through atomic force and near-field optical microscopic investigations, we have found an aggregation process encompassing both the main and side chains to be responsible for the permanent storage in the case of polyesters. The stored information can be erased globally in this case with heat. On the contrary, holograms written in peptide films are not totally erased even after exposure to 250 degree(s)C for one month. However, the information can be locally erased using circularly polarized light. A strong polarization dependent surface relief is observed both for the polyesters and peptides. Through FTIR and surface profile measurements, we further show that irradiation of the films with p- polarized light results in a large surface roughness. We show that in the case of the polyesters the storage is mostly due to optical anisotropy and in the case of the peptide oligomers, both the anisotropy and surface relief are large.

A new analysis of the reversal bleaching mechanism and the catalytic reaction of exposure quantity in silver halide holographic diffraction gratings is presented. It is turned out that the exposure quantity reacts as a catalyst in the developing process and makes the velocity of developing reaction time fast. The experimental investigation has revealed that the holographic phase gratings with high diffraction efficiencies (> 70%) could be taken, if the developing reaction time be optimized in the 50 approximately 350 [(mu) J/cm²] range of exposure quantity.

At the end of the last century, Gabriel Lippmann was experimenting with color photography. His photographic color recording technique, Lippmann photography, produced very beautiful photographs and the fact that the colors are preserved in the early Lippmann photographs indicates something about their archival properties. Recent progress in color reflection holography has made it possible to take a new look at this one hundred year old photographic technique. Today, high-resolution panchromatic recording materials suitable for Lippmann photography are on the market. In particular, the color photopolymers from DuPont have been investigated for modern Lippmann photography. Since the color photographs contain no dyes or pigments their archival stability may be high. In addition, a Lippmann photograph is difficult to copy which makes it a unique color photographic recording. Both of these features must attract a photographer interested in creating beautiful art photographs. Security application is another potential field for Lippmann photographs as well as optical filters. The dry processing of the photopolymer material is an important advantage. Another advantage is that no expensive equipment, such as lasers, is needed to explore this photographic recording technique; only a modified camera is required.

We have been investigating wavelength multiplexed holograms in persistent spectral hole burning (PHB) materials. We have examined PHB hologram characteristics in some organic PHB materials to show guides to produce more suitable PHB materials for wavelength multiplexed holograms. The examined characteristics were diffraction efficiency, sensitivity and the capability of wavelength-multiplexing and the distribution of diffraction efficiency at the temperature of 4.2 K. Typical characteristics in the examined materials at 4.2 K were as follows: (1) sensitivity of > 0.1 mJ/cm², (2) diffraction efficiency of < 0.3%, and (3) the holograms' intervals of > 15 GHz where adjacent holograms could be formed most closely without cross talk. Hundreds of holograms can be stored without crosstalk with each other in calculation. Furthermore, we showed that wavelength multiplexed holographic storage of tens of 2- and 3-D images could be performed at the different laser frequencies at the temperature of 4.2 K. The continuous 3D retrieval of the images of a moving object could be performed by scanning laser frequency continuously.

The analysis of the results received during last 5 years in the field of light-sensitive holographic recording media is presented. The lines of the improvement of these media for color display holography, phototechnology for making of holographic optical elements and perspective information optical technologies are determined.

The forming of intensive Bragg diffraction maxima at recording of volume reflection holograms in dichromated gelatin (DCG) is investigated. The Bragg maxima up to 3rd order are received at use of special techniques of DCG layer processing. Mentioned maxima are located in the spectral range from UV up to IR wavelengths. The intensity of harmonics is high enough. By means of rigorous chain-matrix method the spectral characteristics of holographic structures with non-sinusoidal refractive-index modulation profile are calculated. Spectral curves for various sets of hologram parameters are computed and approximation of spectra received experimentally is conducted.

The forming of intensity Bragg diffraction maxima at recording of volume reflection holography in dichromated gelatin is investigated. The Bragg maxima up to 4th order are received at use of special schemes of hologram recording. Mentioned maxima are located in the spectral range from UV up to IR wavelengths. The intensity of harmonics is high enough. By means of rigorous chain-matrix method the spectral characteristics of holographic structures with uniform on thickness parameters and nonsinusoidal refractive-index modulation profile are calculated. Spectral curves for various sets of hologram parameters are computed and approximation of spectra received experimentally is conducted.

An investigation that the diffraction efficiency of dichromated gelatin (DCG) holograms is stable in the high humidity (RH equals 85%) environment is reported. In this study, the amino group, one strong absorbing humidity groups of gelatin in DCG, is modified with acetic anhydride and changed into weak absorbing humidity groups, amide groups. The procedures of the molecule enclosure did not obviously affect the diffraction efficient of DCG holograms.

The holographic camera system for surface-relief hologram multiple reversible registration is presented. Photosensitive media is a single-layer photothermoplastic polymer on a glass substrate with conductive layer. This exclude a charges accumulation in the polymer volume and permits to realize an efficient enhancement of latent electrostatic image and its fast pulse heating development. The processes of charging, photogeneration, carriers transport, fast development and erasing, image enhancement were studied in detail and optimized. In order to improve some defects of photothermoplastic recording, originating from influences of circumstances and recording conditions, some new processes were developed: (1) fast charging with pulses corona in closed dielectric volume, (2) optoelectronic enhancement of electrostatic image, and (3) fast pulsed development with automatically controlled temperature rate. The dust-proof recording camera with built-in highvoltage power supply, thermo- and photosensors was designed to meet the needs of real-time or multiple- exposure interferometry, holographic training recording, holographic storage systems, correlation investigations and pattern recognition.

The results of investigations of real-time gratings recording in lightsensitive medium of photosynthetic reaction centers at near IR are presented. Investigations were carried out using low-intensity semiconductor lasers of different wavelengths. The contribution of absorption and dispersive components of grating was evaluated. The maximum value of diffraction efficiency was 0.06%. The spatial- frequency dependence of grating efficiency was investigated.

We demonstrate the recording of high-efficiency reflection holograms in DuPont photopolymer films HRF-800X071-20 and HRF-700X001-20 by using, for the first time to our knowledge, nanosecond laser pulses. The weak reflectance efficiency (6.5%) of the mirror holograms could be significantly improved up to 75% by using pre-illumination. With incoherent pre-illumination, significantly increased diffraction efficiency and sensitivity of the holograms are obtained, while pulsed pre-illumination leads to an enhancement of the reflectance only. The results are compared with cw laser exposure under identical processing conditions, including pre-illumination.

Diffraction characteristics of 0.5 micron period, liquid- crystal-filled diffraction gratings are presented. Theoretical predictions from rigorous coupled wave analysis, device fabrication techniques, and experimental device performance are detailed. These devices are shown to be useful for diffractive daylighting, high efficiency color liquid crystal displays and as elements in 3D video systems.

Large format holograms are of potential interest to the energy and building sectors. Such holograms are considered as present for photovoltaic power generation and for daylighting or glazing in buildings. Dichromated gelatin exhibits properties that are nearly ideal for these applications. Both sectors require large format holograms with accurately controlled properties, such as: spectral bandwidth, operating wavelength and diffraction efficiency. The required properties are attained by exactly controlling the thickness of the gelatin layer and the refractive index variation over the entire aperture as a function of layer depth. The information presented in this paper is based on ten years' efforts that includes layer deposition and film drying techniques with controlled thickness, development process and an inexpensive dry copying procedure for the industrial fabrication of the holograms on a flexible film substratum. Design criteria and experimental results for large format holographic gratings, lenses and mirrors are presented and discussed. The current technology facilitates the manufacturing of HOEs that operate between 400 nm and 1500 nm in various applications: photovoltaic solar concentrators for multicolor operation, hybrid collectors for simultaneous thermal and PV application, holographic stacks for white light (RGB) daylighting and wideband sun shading and holographic concentrators with spectral bandwidths that are adapted to particular photochemical reactions for solar chemistry.