Digital holography is analysis, synthesis and simulation of wave fields by means of digital computers and processors. Since first publications in digital holography, more than 30 years have passed. From then on, the ideas of digital holography formulated at that time has found quite a number of applications and implementations; but not all of them. Some old dreams such as that of holographic television, display and virtual reality still have not come true and some results and methods were left on the roadside. In the paper, a brief review of digital holography is presented and some 'roadside' subjects such as discrete representation of optical transforms and Monte Carlo methods for synthesis of computer generated display holograms and studying speckle noise in coherent imaging systems are revisited. In particular, it is shown (i) how, by an appropriate selection of a 'virtual' pseudo-random diffuser, one can generate Fourier holograms of 3D objects that can reconstruct their images from different observation directions and (ii) how such distortions in measuring diffusely scattered wave fields for computer reconstruction as limitation of the hologram size, limitation of its dynamic range and quantization affect speckle contrast in reconstructed images.

Computational methods for image plane reconstruction form a hologram are developed. The methods are based on use of Fast Fourier Transform which greatly aids the computation speed. Even more computing speed is afforded by a special-purpose digital signal processor programmed for this application. The goal is to greatly speed up the process of quantitative image reconstruction as compared to 3D scanning of optically reconstructed images. Examples of in-line holographically recorded images of marine micro-organisms are shown and computed images from computationally synthesized particle field hologram are provided since this is of interest for 3D particle image velocimetry. A fast computational method of counting the number of small objects recorded on a hologram is developed and used. A measure of the depth of field is given which shows that for very fine depth resolution, off- axis holograms are recommended. However, these require more pixels and image memory so they are limited to smaller areas than in-line holograms.

We report on new developments of a technique called Digital Holographic Microscopy (DHM), for the numerical reconstruction of digital holograms taken in microscopy, which allows simultaneous amplitude and quantitative phase contrast imaging. The reconstruction method computes the propagation of the complex optical wavefront diffracted by the object and is used to determine the refractive index and/or shape of the object with accuracies in the nanometer range along the optical axis.. The method requires the acquisition of a single hologram. The technique comprises the recording of a digital hologram of the specimen by means of a standard CCD camera at the exit of a Mach-Zehnder or Michelson type interferometer. The quantitative nature of the reconstructed phase distribution has been demonstrated by an application to surface profilometry where step height differences of a few nanometers have been measured. Another application takes place in biology for transmission phase- contrast imaging of living cells in culture. The resolution for thickness measurements depends on the refractive index of the specimen and a resolution of approximately 30 nanometers in height, and about half of a micro in width, has been achieved for living neural cells in cultures by using a high numerical aperture.

In digital holographic microscopy, a hologram of an object is recorded by an electronic image sensors and a computer is used to reconstruct the original object numerically. A number ro different arrangements have been successfully used, for example by Haddad, Schnars, Takaki and Jacquot. There is an intermediate case between the Fourier-transform method of Haddad et al and the Fresnel arrangement used by Jacquot et al, which has some of the advantages of both methods. A point reference source in a lane some distance from object provides the spatial frequency reduction in the hologram plane, as for Fourier transform methods, without the strong central peak and with the twin image defocused in the object plane. This arrangement is tested, showing that it can produce a resolution significantly improved over the Fresnel case. We also consider the removal of the holographic twin image in the Fresnel in-line holographic arrangement. The high-contrast parts of the image are assumed to be part of the true image, and the twin image corresponding to these high-contrast elements is subtracted, leaving an improved estimate of the true image only. We present experimental results demonstrating this method for a number of different objects.

Two schemes for digital holographic microscopy are explored. The goal is to revisit the issues that have hindered holographic microscopy since its earlier days, and find ways to overcome these difficulties. The first scheme discussed is a full-field holographic method that takes advantages of the properties of charge-coupled-device detectors, namely their high spatial as well as temporal bandwidths. The second scheme is based ona scanning holographic technique, and is shown to offer a wide range of possibilities such as enhanced transverse resolution, extended depth of focus, or axial sectioning. Both schemes are described, and some of their attributes and relative merits are discussed.

Novel method for synthesizing light waves from objects expressed in surface model is presented for fast creation of digitally synthetic holograms. This method has a feature of coordinates rotation in Fourier domain, in which only twice FFTs and an interpolation of spectrum are necessary for calculation of light waves form each object's plane. Therefore, presented method is faster than conventional ray- tracing when large scale full-parallax holograms are synthesized in a surface model. Phases of a surface object are also discussed in relation to controlling the direction and diffusiveness of object waves. Furthermore, fabrication of a hologram based on the method and its reconstruction are presented for a demonstration.

A new and practical method for achieving Color Electro- Holographic Display systems was developed and tested with very promising results. In this method, holography techniques utilizing a single white light source, instead of the traditional three color laser lights, and three liquid crystal display panels (LCD) were proposed. A metal halide lamp with good specifications in each wavelength of the color components was adopted as the light source. Each of the three color light components required for the reconstruction of an image was extracted by color separation using dichroic mirrors. The separate color images were then reconstructed by the hologram formed on the LCD panels which is then combined together through eh use of a prism to form a single 3D image. Moreover, in proposal method, no lens are used by virtual-image-reconstruction. System size was reduced so far in 40 percent of the techniques by the proposal technique.

We describe the development, construction and sea testing of An underwater holographic camera (HoloCam) for in situ recording of marine organisms and particles in large volumes of sea water. HoloCam comprises a laser, power supply, holographic recording optics, and plate holders, a water- tight housing and a support frame. Added to this are control electronics such that the entire camera is remotely operable and controllable from ship or dock-side. Uniquely the camera can simultaneously record both in-line and off-axis holograms using a pulsed frequency double Nd:YAG laser. In- line holography is capable of producing images of organisms with a resolution of better than 10 micrometers . Off-axis holograms of aquatic systems of up to 50,000 cm³ volume, have been recorded. Following initial laboratory testing, the holo-camera was evaluated in an observation tank and ultimately was tested in Loch Etive, Scotland. In-line and off-axis holograms were recorded to a depth of 100 m. We will present result on the ste dives and evaluation of the camera performance.

The application of pulsed laser in real time holography base don acousto-optic (AO) cells allows to get rid of mechanical horizontal scanning. The improvement of recently reported real time pulsed holographic display is presented. Ar-ion laser, used before as a coherent light source, is replaced with Q-switching Nd:YVO₄ laser with SHG, operated by external triggering at 46 kHz. The commercial PC dual monitor graphic card was adapted to generate six parallel analogue outputs to feed six AO cells with gray scale hologram data. The upgrade improves brightness and clearness of reconstructed images and reduces the system dimensions and power consumption. 2D and 3D images reconstructed from precomputed HPO holograms are presented.

Until recently, display holography was usually associate with 3D imaging. After the appearance of color holography it has become possible, however, to record holographic images of 2D objects, such as, for example, oil paintings. The realistic-looking virtual image recorded in a Denisyuk reflection hologram is the most suitable for such reproductions. A holographic contact recording of a painting reproduces the painting with all its texture details preserved, such as brush strokes, the painter's signature, etc. This means that an exact copy of the painting can be made, which can then be displayed at art exhibitions, museums, etc., when the original is not available. If an expensive painting is concerned, possessing an exact copy of the painting may also be important for insurance purposes, in case the painting is stolen or damaged. The advantage of a color contact hologram is that the hologram reconstruction process can be relaxed, as there is no need of spatial coherence of the white light source used to illuminate the hologram. In addition, no depth distortions are introduced as a function of the light source's distance from the plate. Only the angel of illumination is of primary importance if good color reproduction is to be obtained. The paper discusses the rendition of color in hologram, which is extremely important in this case. The holographic reproduction process of an oil painting is also described, and the major advantages of holographic reproduction are discussed together with its limitations.

Six novel methods in real-time holographic interferometry recently worked out by the authors of this paper. They are: the one for recording a real-time hologram with high contrast interference fringes and high brightness of the testing optics field, the one for measuring the phase modulation of a thin-phase hologram, the one for controlling the phase modulation in making a real-time hologram, the one for measuring in the 'reference wave field', the one for fast predicting the direction of displacement, and the one for avoiding the light reflected from the surfaces of collimation lens. All these methods are helpful to holographers in pursuit of high precision and efficiency in real-time holographic interferometry.

The results of experimental and theoretical investigations of dynamic hologram recording and optical limiter improvement in nano-size porous glasses containing fullerene C₆₀ and toluene solution of C₆₀ are presented. TO record a grating with spatial frequency 20 mm^-1 we used laser pulses with 18 ns duration and 532 nm wavelength. Initial transmittance of the samples varied from 32 percent to 73 percent. Experiment showed that high diffraction orders appeared during dynamic hologram recording, and if the input intensity increased the number of orders increased, too. Presence of high diffraction orders caused more effective optical limiting because of laser energy redistribution. Taking into consideration different processes including reverse saturable absorption a model of dynamic hologram recording in fullerene solution waw carried out. The result of experiments were analyzed by numerical modeling. Analysis of computations and experimental results showed adequacy of the used model and perspective of applying of dynamic hologram recording in media containing C₆₀ toluene solution for improvement of optical limiting.

This paper is useful for teaching holography workshops in classrooms as well as in makeshift locations such as museums, businesses, and homes. The target audience is very general, young children to adults of any profession, al of whom have no prior experience in making holograms. A typical number of participants is twenty-five, but can vary depending on space and personnel availability. A central original contribution of this paper is the discovery of a new chemical processing regime for the Slavich PFG-03M holographic plates. These silver halide plates have the highest resolution of its kind and some of the world's best holograms have been recorded on it for several decades. Due to its low sensitivity and long developing time, this material has been excluded form use in workshops. Our new processing regime JARB has the following advantages: It (1) increases the sensitivity of PFG-03M emulsion ten-fold without sacrificing resolution; (2) hardens the emulsion during processing without significant shrinkage; (3) has a ten- to twenty-second development time; (4) is quick drying using squeegee and warm air; and (5) allows the finished hologram to be viewable with laser or incandescent light. Other advantages of JARB are (1) low toxicity, (2) low volatility, (3) non-staining, (4) low cost, and (5) long shelf life.

Teaching holography at high school level is a fascinating task and an important teaching tool. The impact on students is very positive and satisfactory at a personal level as well as at a pedagogical level. The purpose of this work is the 3D imaging by holographic means for application in different educational areas. In this paper we present a project that intends to explore the technique and some applications of holography for particular aims in each field of study. The educational strategy based on contextualized teaching of optics with multi disciplinary and technological applications will be presented. A comparison between the interest on holography by science and art students will be analyzed. The experimental configurations and chemical processing will be presented. The result obtained will be analyzed and discussed.

This paper considers research and development of arrays of computer-generated multiple-focus phase micro holograms for providing given light patterns in the near field zone. Peculiarities of such arrays are discussed. The main result of the talk is the fabrication of the micro hologram array providing the given complex image in the focal plane. The size of array was 1.54 mm by 1.54 mm, the size of each micro hologram was 0.192 mm by 0.192 mm, and focal length - 2 mm.

The authors present the hologram computer-aided design (CAD) tool, and analysis of imaging characteristics of holographic optical element (HOE) taking light efficiency into consideration using the tool. The tool, which the authors have been developed, is specialized in hologram and provides the capability of analysis, simulations, and designing of holograms. The function of analyzing the imaging characteristics of the tool calculates imaging point and displays spot diagram. HOE lenses, whose the recording and reconstruction wavelengths are different each other, are designed and their characteristics are analyzed taking light efficiency into consideration by the tool. The result of the analysis show that although the spot diagram with considering light efficiency has the same intensity as that without it, the RMS radius of the spot diagram can be reduced. The tool has been also extended to deal with a Gaussian beam as intensity profile of the illuminating wave of hologram for more precise and high flexible analysis. The Gaussian beam is implemented by weighting individual reconstructing ray with relative intensity. The analysis taking light efficiency and the weight into consideration is useful to clarify more effective HOE lens and helpful for designing practical holograms.

The inherent feature of the coherent optics is the speckle phenomena. To reduce the spiral speckle in the diffraction image generated by the diffractive optical element, we designed the boundary modulated diffractive optical element. The spiral speckles can be removed by introducing an appropriate smooth initial phase to the image plane and conserving the smoothness of it during the iteration process of the iterative Fourier transform algorithm. To conserve the smoothness of the phase on the image plane, the aperture shape of the diffractive optical element is modified optimally. The diffractive optical element with deformed aperture decreases the transmission efficiency. TO increase the transmission efficiency, the initial phase distribution of the image plane is optimized by use of the genetic algorithm.

A new type of grating image that provides a higher resolution imaging known as 'Crystagram Neo' is presented. As in a conventional grating image, a Crystagram Neo is constructed by a lot of tiny diffraction grating cells written by Electron Beam technology. Its primary point is a novel design method to arrange cells and to make gratings in those cells. On a conventional dot matrix grating pattern, the identical size cells are arranged orderly in a matrix order, and the gratings exist inside the cells by a monotonous arrangement. On the other hand, each gratin cell of Crystagram Neo have various size, and gratings are made with the cell independent distribution. BY this method, a Crystagram Neo which ash more flexible arranged gratings supplies a full color image, superfine micro characters with smooth shapes among other advantages. These properties provide even more effective measures against counterfeiting for security usage.

We propose a technique to produce conical beams. This effect is produced when a conventional beam laser through the radial amplitude computer hologram. The computer hologram can be designed to produce a first order ring of light distribution with a spot in the center of the screen, elliptical distribution or another conical distribution are designed and shown. With these computer holograms, we can modulate the spatial structure of the light source. With the radial amplitude hologram is possible to produce different conical distribution, only with incorporate a phase term in the hologram function.

RL Associates in conjunction with Hybrid Technologies is developing a narrow linewidth optical filter employing extremely thick volume holographic diffraction gratings. The gratings are written in MEMPLEX, a new holographic materia invented by Laser Photonics Technology, Inc. and licensed to Hybrid Technologies. MEMPLEX has the following characteristics: (1) Excellent optical clarity, (2) Preparable at any thickness up to 10 mm, (3) Large dynamic range for plane wave holograms, (4) Hard, freestanding, stable, polishable and coatable. We have written and characterized numerous gratings in 1.8 mm thick samples to study the effect of writing geometry on the spectral linewidth and field-of-view of a single grating in the reflection geometry. We have succeeded in writing some very efficient gratings at 15 degrees internal write angles with external slant angles of 5 degrees. These gratings exhibit linewidths of < 0.2 nm and diffraction efficiencies of better than 70 percent. The measured angular acceptance of these gratings ranges from 0.1 to 0.24 degrees. We have also written some initial angle multiplexed gratings which include 3 efficient gratings in the same volume in an attempt to increase the angular acceptance. In this manner we hope to achieve a highly efficient optical filter with extremely narrow spectral linewidth and wide angular acceptance. Filters based on thick volume holograms show great promise in Lidar applications and should result in superior S/N ratios.

Generally, an autostereoscopic display presents a 3D image to a viewer without the need for glasses or other encumbering viewing aids. In this paper, we propose a new autostereoscopic 3D video display system which allows viewers to observe 3D images in the same range of viewing angle. In this system, a photopolymer-based VHOE is made from volume holographic recording materials and it is used for projecting a multiview images to the spatially different directions sequentially in time. Since this technique is based on the VHOE made from the photorefractive photopolymer instead of the conventional parallax barrier or lenticular sheet, the resolution and parallax number of the proposed VHOE-based 3D display system are limited by the photopolymer's physical and optical properties. To make the photopolymer to be applicable for a multiview autostereoscopic 3D display system, the photopolymer must be capable of achieving some properties such as a low distortion of the diffracted light beam, high diffraction efficiency, and uniform intensities of the reconstructed diffracted lights from the fully recorded diffraction gratings. In this paper, the optical and physical characteristics of the DuPont HRF photopolymer-based VHOE such as a distortion of displayed image, uniformity of the diffracted light intensity, photosensitivity and diffraction efficiency are measured and discussed.

FRTH is a new kind of hologram, which is different form common Fresnel holograms and Fourier transform holograms. It can be applied for fractional Fourier transform filtering and anti-counterfeiting, etc. Due to the flexibility of holographic lens, we present a method that uses the -1 diffraction wave of holographic lens as the object wave and the 0 diffraction wave as the reference wave to record FRTH. It provides a new simple way to record FRTH. In this paper, the theory of achieving FRT and recording FRTH with holographic lens has been discussed, and the experimental results are also presented.

It is verified by the source-to-fiber coupling experiment that micro holographic lenses (MHLs) can be used as the outside coupler the light emitted form a laser diode to a fiber. Properly arranging the recording geometry using the equation presented in the paper to fabricate MHLs, the performance of a single MHL can replace a complicated optical coupling system, thus resulting in compact configuration, easy alignment and low cost. Proposals for further increasing the coupling efficiency are provided.

We show a technique to modulate source spatial coherence, using conical beams, made with rings amplitude computer hologram. With these devices can be applied to modulate the spatial structure of the light from arbitrary source. In the present work, we design a computer amplitude hologram to produce as to first order a light distribution as ring with a spot in the center of the conical distribution, incrementing the spatial coherence. Because a ring light has more small the airy disc than conventional pupil with similar diameter, Young interferometer, we model by numerical process to obtain the visibility of the interference pattern. This device opens the possibility to make good collimator of white light.

In this report, a method of producing computer-generated holograms (CGHs) that are capable of reconstructing 3D images with higher luminosity than our previously manufactured ones is proposed. This method involves controlling etching depth and width of each cell in order to record both phase and amplitude information of the object wave. In the previous method, presented in Practical Holography XIII, interferogram data of the CGHs are computed by simulating a recording process of conventional optical holograms. This method, however, has a disadvantage in diffraction efficiency, due to the fact that only the first order diffraction of incident light contributes to reconstructing images, leaving the other orders of diffraction wasted. In order to improve the diffraction efficiency, it is desirable to modulate incident light directly to the wavefront that reconstructs the images. In this report, the cell structure that modulates both the phase and the amplitude of an incident light is proposed. The etching depth of a cell encodes phase information, and the etching width of the cell encodes amplitude information. A CGH was fabricated by forming each cell corresponding to the complex amplitude of the object wave at each sampling point of the CGH. With this method, we have succeeded in fabricating the image-type CGH that can reconstruct multilevel 3D images with about twice as high luminosity as the previous type ones.

A new rotation-angularly multiplexed holographic memory system by using moving window and double-focusing lens (DFL) is proposed, in which crosstalk due to two neighboring moving window rows in the vertical direction of the conventional moving window (MW) holographic memory system can be overcome. That is to say, in the proposed method, crosstalk in the vertical direction can be eliminated by combined use of the DFL, which has periodical curvature of radius R₁ and R₂ with different focal lengths F1 and F2, respective, and moving windows on the LCD spatial light modulator. Light beams form curvature of radius R₁ and R₂ parts of double-focusing lens are focused at F1 and F2 locations, respectively, to occur different reference wave vectors K_r and K_r. By such shift multiplexing effect, crosstalks due to two neighboring MW rows in the vertical direction on the reconstruction can be eliminated. By combining the proposed multiplexing method with rotating disc-type photopolymer, it is possible to achieve the high- density storage capacity compared with the conventional holograph memory system and its feasibility is demonstrated through optical experiments.

A new compact hologram display system is presented. An LED is used to illuminate the hologram directly in air with around 85 degrees incidence. No intermediate element is used between the light source and the hologram so that the system is extremely compact and the hologram recording process is simple. The mechanism of the generation of harmful interference fringes on the hologram is analyzed, and the proposed method eliminates the harmful fringes effectively.

The novel method of using holographic optical element (HOE) to realize optical clock distribution for optical interconnection is presented. Polarization holographic technique is adopted to fabricate the HOEs. 4-fan-out clock distribution has been obtained. Methods for obtaining multiple fan-out clock distribution using polarization holographic technique is proposed.

When fabricating a large area holographic diffuser by cascading hologram of diffusion patterns with specified are, it was found that a fluctuation of diffraction intensity occurred at the boundaries of the two adjacent exposed areas. It was affirmed experimentally that this problem could be alleviated by controlling the intensity distribution of reference laser beam around the boundary of each exposure area. Using these method, the fluctuation was reduced considerably. For better compensation of the non- uniformity a theoretical analysis for the diffusion process of photopolymer is discussed and compared with the experimental result.

The method and the optical system for making rainbow multiplex holograms are described. The making of rainbow multiplex holograms is a very difficult task, because the optical component requirements are very high. The optical system for the recording rainbow multiplex holograms is a modified optical system for two-step technology. Using computer graphics, we can create an object that the 3D information. This computer-generated graphic object is divided into several view aspects, which are used to synthesize the composite hologram of Leith. The composite hologram consists of several slits, each of them is a number of a simple holograms. The image, reconstructed from the composite hologram of Leith, is projected to the plane of the rainbow multiplex hologram. The proposed technique gives a high quality reconstructed image.

Multi-phase and binary-phase computer-generated holograms were designed and demonstrated for full-color image generation. Optimize a phase profile of the hologram that achieves each color image, we employed a simulated annealing method. The design binary phase hologram had the diffraction efficiency of 33.23 percent and the reconstruction error of 0.367 X 10^-2. And eight phase hologram had the diffraction efficiency of 67.92 percent and the reconstruction error of 0.273 X 10^-2. The designed BPH was fabricated by micro photolithographic technique with a minimum pixel width of 5micrometers . And the it was reconstructed using by two Ar-ion lasers and a He-Ne laser. In addition, the color dispersion characteristic of the fabricate grating and scaling problem of the reconstructed image were discussed.

We have reported that viewing angle of the computer- generated hologram can be expanded with lensless Fourier transform hologram. It however, requires a laser to illuminate the CGH for reconstruction. In the previous paper, we have proposed that making the second hologram for white-light reconstruction. The reconstructed image from the first hologram is used as the object beam of the second hologram. The second hologram can be either transmission or reflection hologram, which depends on the direction of the reference beam. In this report, we extend this method to make the full-parallax computer-generated holographic stereogram. At first, we calculate the master hologram consists of elementary holograms. Each elementary hologram is calculate by Fast Fourier Transform of perspective 2D image. Then, the transfer hologram can be made from the master CGH with single exposure. In the experimental result, we obtain full-parallax computer-generated holographic stereogram with 20 degrees of viewing angle and 10 mm X 7.6 mm image size.

Different techniques for making digital holograms in order to synthesize true 3D images have been reported. The generation of digital Fresnel holograms by means of the ray- tracing method is the most flexible way and relatively simple, that is the objects are considered to be composed of a large number of discrete points sources of light, and the complex amplitude of spherical waves from each point sources is super-imposed on the hologram plane, however there is carry out a great amount of calculate. We presented a technique in order to evaluate simultaneously eight points on the hologram plane, so we obtain a reduction in a factor of eight the computation time. The equation of Kirchhoff- Fresnel is first calculated applying symmetry conditions avoided the redundancy in the calculations and later added the reference wave; also the precision in the values of the complex amplitude is not loss. Other methods that have been reported coupled components doing the ray tracing methods quicker yet.

A blue white beam of commercially available He-Cd laser is simply divided into the light with three primary colors, i.e., R/G/B components, using a set of dichroic mirrors. The dichroic mirror is widely used in color TV cameras or in optical special sensors to separate the visual image into its three primary color components. In this study influence on additive color mixture of two types of reconstructed hologram images is checked from the optical experimental results using the He-Cd laser and dichroic mirrors. The visual appearance and deterioration of reconstructed images owing to the cross-talk are discussed as for the optical Fresnel hologram and computer generated FTH. In the case of the Fresnel hologram, the reduction ratio, i.e., estimation value of reconstructed color images is considered from the theoretical and experimental view-points.

Theoretical analysis indicates that for micro holographic Fresnel lenses with the same diameter, the spatial frequency of the interference fringes of the MHFL recorded with two spherical waves is higher than that recorded with a spherical wave and a plane wave. Therefore two-spherical- wave arrangement results in higher diffraction efficiency. Experimental results have verified the theoretical analysis. To obtain an MHFL with small diameter and high spatial frequency of interference fringes, lense with large f-number are preferred in the recording geometry.

In this paper the physical process of real-time holographic interferometry is simulated by the computer calculations based on scalar diffraction theorem and the deformation field of the specimen is calculated by the inverse calculation of the diffraction from the interference fringes. The application the study of micro-crack nucleation process leads to interesting result in good agreement with experiments.

The present paper suggest vast experimental data as a form of phase images obtained in vibrational stability testing of industrial products. An optical configuration based on the photo thermoplastic recording is suggested for the operation optical diagnostics and standardization of the products in the real time scale. Dry development of the images in the real-time scale and instant fixation of images on the photo thermoplastic carriers followed by the computer analysis used to compare the production and the standard allow us to gain in time and areas.

A 2D dynamic phase-modulating system (DPS) addressed by a digital signal at video frame rate can realize several optical transmission functions in the field of refractive as well as diffractive optics. Critical parameters are the space-bandwidth product, the phase shift and the light efficiency of the system. We demonstrate result of our current research activities on a compact system based on the SVGA spatial light modulator and a 635 nm laser diode. Points of discussion are limitations of pixilated diffractive optical systems, which cause boundaries for the application in the field of beam shaping and beam splitting. Furthermore, light efficiency and compactness of the systems architecture are main tasks. Examples are shown, which deal with the current state of beam shaping possibilities and which show the potential in the field of rapid-prototyping for optical transmission functions.

Problems of the quality improvement of holographic images and the reconstruction time reduction are discussed. The convolution and Fresnel approaches are presented. For both methods the algorithm improvement is proposed. Basing on the special transmittance function calculating the computation time is significantly decreased. For the Fresnel approximation the autocorrelation factor from the reconstructed image is removed. The presented ideas are illustrated by exemplary images for each step of computation. Advantages and disadvantages of the methods are discussed.

Holographic spectral filters become popular nowadays in various kinds of wavelength selective devices. The attractive feature of holograms is the possibility to widely vary the final parameters of a filter by choosing the appropriate recording material and recording geometry. However, up to a recent time there was a kind of a gap in attainable spectral selectivity due to the thickness of available materials. The ordinary materials, such as DCG, photopolymers, silver halide etc. are usually 20-30 micrometers thick. The very thick materials, namely porous glasses, PDA and some others start from the thickness of a few hundreds of micrometers. And because of that it was rather difficult to achieve the spectral selectivity of the order form several nanometers up to 20-30 nanometers, which are magnitudes required for many applications. The new holographic photopolymer film from DuPont, 50 micrometers thick, is a good candidate to fill in the gap and to obtain filters with the desired selectivity. This paper presents results on the recording of holographic spectral filters in this material.

Surface relief holograms are fabricated by means of irradiation of laser interference patterns. The diffraction efficiency and the surface relief depth depend on the writing energy and the polarization of the writing laser beam. This structure is very stable at temperatures under glass transition temperature T_g and can be erased by heating above T_g. We proposed a new technique to control the surface relief structure. The electric charge was deposited on the surface relief grating in a corona- depositing poling setup in an oven. The first-order diffraction efficiency measured before and after corona discharge increased from about 0.24 percent to about 28 percent. This diffraction efficiency increase is mainly caused by the increase of the relief depth caused by the electric charge. The relief depth is increased form 20 nm to 350 nm by corona charging.

Recently, a number of photopolymers for recording volume phase hologram have been proposed. We have developed the novel photopolymerizable materials for recording the transmission and reflection volume holograms. These hologram recording materials are composed of lower-refractive index binding polymers, higher-refractive index monomers, plasticizers, photoinitiators, and photosensitive dyes. In this paper, the experimental result for the holograms using these materials would be presented. These materials can record both transmission and reflection volume holograms with high sensitivity, high diffraction efficiency, high resolution, and high heat resistance. These holograms were self-developing and white light was sufficient for fixing. After recording holograms, no treating to fix such as heat processing or postexposure of UV were needed. The optical and thermal properties of obtained hologram are written as follow. The diffraction efficiencies were over 90 percent. Transmittance was about 90 percent. Sensitivities were less than 10 mJ/cm² from UV light to Ar ion laser. And these holograms have the heat resistance over 100 degrees C. The mechanisms of refractive index modulation in photopolymerization of the materials are also discussed.

The high density and data rate performance demonstrated for holographic data storage continues to fuel research and development efforts, even in the face of continued rapid improvement in performance and decrease in cost of conventional technologies. A major remaining technical challenge for a commercially viable system is the development of a suitable storage medium, especially for rewriteable storage. At IBM, we have tested a variety of potential holographic storage materials for both thin 'disk' applications and bulk crystal stationary media applications. Here, we review the materials requirements for both geometries and assess the performance of some of the best materials candidates.

A numerical method is developed to investigate the properties of polarization diffraction gratings. The diffraction efficiency and polarization state of the diffraction orders are investigated in 3 main cases - when recording with two circularly polarized waves; when recording with two linear polarizations and in the general case - two orthogonal elliptical polarizations. The linear and circular anisotropy of the recording media are taken into consideration. The result in particular cases known from the practice or where analytical expressions have been reported, are in agreement with the model predictions.

Self-developing dichromated gelatin is holographic photosensitive medium that possesses the number of unique properties. Being illuminated by interferometric pattern it records the energy distribution, and in such way the gratings with high diffraction efficiency can be obtained. The absence of postexposure processing allows to use it for in-situ experiments. And besides the self-developing property of the material allows to create new kinds of optical elements based on very thick gratings that possess very high selectivity properties.

One of the most important area of holograph applications is display holography. In case of pulse recording the requirement for vibration stability is easier than compared to CW exposure. At the same time it is widely known that the behavior of sliver-halide holographic materials strongly depends on the exposure duration. In particular the exposure sensitivity drastically decreases under nanosecond pulse duration. One of the effective ways of the diffraction efficiency improvement is SHSG processing method. This processing scheme is based on high modulation of refractive index due to microvoids appearance inside emulsion layer. It should be mentioned that the SHSG method was used earlier only in the cases when the holograms were recorded by use of CW lasers. This work is devoted to the investigation of SHSG method for pulse hologram recording on VRP plates. We used a pulsed YLF:Nd laser with pulse duration of 25 nanoseconds and wavelength of 527 nm. Both transmission and reflection holograms were recorded. The different kinds of bleaching as well as developing solutions were investigated. Our final processing scheme includes the following stages: 1) development in non-tanning solution, 2) rehalogenating bleach, 3) intermediate alcohol drying, 4) uniform second exposure, 5) second development in diluted developer, 6) reverse bleaching, 7) fixing and 8) gradient drying in isopropyl alcohol. Diffraction efficiency of transmission holograms was of about 60 percent and reflection mirror holograms was of about 45 percent. Thus we have demonstrated the SHSG processing scheme for producing effective holograms on VRP plates under pulse exposure.

The recording and processing technique for color HOEs in ultrafine-grain panchromatic silver halide emulsions is presented. It is possible to obtain high diffraction efficiency employing the silver halide sensitized gelatin (SHSG) process. SHSG holograms are similar to holograms recorded in dichromated gelatin (DCG). The drawback of DCG is its low sensitivity and limited spectral response. Panchromatic silver halide materials from Slavich can be processed in such a way that the final holograms have properties like a DCG hologram. The processing method or microvoid technique has been optimized for three laser- wavelength recordings in Slavich PFG-03C emulsion. For example, applying this new processing technique high- efficiency white holographic reflectors can be manufactured. The technique is also suitable for producing efficiency color display holograms. In particular, masters for mass production of color holograms or color HOEs can be performed by contact-copying into photopolymer materials because the reconstruction wavelengths are identical to the recording wavelengths.

Ion this work we present a distortion of the usual H-D curve due to the action of a high contrast developer, Kodak D8 on ultra fine grain emulsion. This effect has been found for emulsions BB640, with a mean grain size of 20 nm. This anomalous curve shows two different linear zones for two different exposure ranges and no solarization region. Densities higher than 11 have been measured. Superaditivity effects of D8 with different developing agents were studied. Based on obtained result with different holographic bleaching processes, some ideas on the mechanisms involved in the anomaly have been proposed.

Color control is very important in some holographic applications and its is a procedure that should be taken into account during practical holography. In this paper an optimized procedure for reflection holograms recorded in Slavich PFG-01 emulsions will be presented. The procedure is mainly focused on measurements of different colors obtained by manipulation of the emulsion thickness before exposure, which has been preswollen in solution of different concentrations of Triethanolamine and recorded with different exposure times. Experimental configurations and chemical processing will be presented. The results obtained will be analyzed and discussed.

The beam sampling grating is one of the important diffractive optical elements used in the field of laser sampling. It can be considered as an off-axis, binary phase, Fresnel zone plate. Base don the theory of interference, the principle of the variable period grating formation process is analyzed perfectly and the transmissive function of the BSG is obtained. This paper repots to fabricate the BSG with electron-beam direct writing. Compared with the holographic method, the new method is simpler, cheaper, and more efficient to manufacture elements on a large scale.

Quenching ofimidazoyl radical (Im ) formed in photoinitiator systems comprising an aminostyryl dye and a radical generating reagent by a 2mercaptobenzothiazole (MBT):aminostyryl-dye; 2-[p-(diethylamino)styryl]naphtho[1,2-d]thiazole (NAS), radical generating reagent; 2,2'-bis(2-chlorophenyl)-4,4',5,5'4etraphenyl-1,1'-bi-lWimidazole (BI) in a poly(methyl methacrylate) film has been investigated by laser flash photolysis using a total reflection cell.

By rotating the reference beam instead of a photopolymer, we combined rotational multiplexing with angular or shift multiplexing for high capacity hologram storage in DuPont's HRF-150-100 photopolymer material. We used the spherical reference and signal waves for angular and rotational as well as shift and rotation multiplexing. To get uniform diffraction efficiency, we used the time-scheduled exposure during recording.

A holographic study of films prepared with polyvinyl alcohol (PVA) with different molecular weights and sensitized by introducing a dye of the triphenylmethane group is reported. Interference patterns obtained from the superposition of parallel and orthogonal polarized beams are storage in the dyed palates. Recording dynamics of the resultant electric field distributions and dependence of the diffraction efficiency on the PVA molecular weight are determined. Additionally, it is demonstrated that reconstruction of the object polarization is dependent on the frequency of the polarization grating. Finally, the recording area of the material is analyzed to detect a relief formation.

This paper presents theoretical considerations on recording and reconstruction processes of sum- and product-type multiexposure digital holograms in coherent and incoherent configuration. The analysis of the result from the point of view of digital holovideo application is performed. The method of optoelectronic reconstruction of digitally stored holograms is presented.