Trial fabrication of image-type CGHs which are recorded by an electron beam printing system to display 3D images is described. First, to verify the feasibility of fabricating CGHs for 3D image reconstruction, two preliminary experiments, in which the divergence of the object wave was limited in one horizontal plane and the reference wave was defined as a plane wave from the horizontal direction, were performed. To confirm that the depth of reconstructed images can be perceived, two flat images (characters G and R) differing in depth and a simple wire frame object including some lines in the depth direction, were selected as object data. Both images were successfully reconstructed under the white light and thus the feasibility has been supported experimentally. Secondly, to reduce the blur caused by chromatic aberration and to improve the uniformity in luminous intensity in the reconstructed G-R image, the CGH was modified to image-type and the angle of divergence of the object wave was narrowed; thus the reconstructed image has been improved. Finally, to facilitate observation of the reconstructed image, the direction of the reference wave was modified to the vertical direction. All of the reconstructed images are shown and some technical problems are also mentioned.

Electroholographic display with viewing zone multiplexing, based on multichannel AOM is described. A method of viewing zone multiplexing resides in sequential reconstruction of elemental perspective views of the 3D object, accompanied by the formation of moving exit pupil of the display. The exit pupil is created by the combination of field lens and synchronously scanning reflection type vertical diffuser, placed in the reconstructed image volume. The method makes possible spatio-temporal multiplexing of wide viewing zone without resort to optical demagnification. The method is also capable of viewing zone extension without any reduction in lateral size of the reconstructed image. Two types of reconstruction geometry have been considered. One is corresponded to reconstruction of real image Fresnel type hologram, another is similar to Fourier type. Fresnel type display with image size 7 X 7 cm is designed for the experimental realization.

Computer generated hologram as a basic optical diffractive element can be used widely in many fields. In designing computer generated holograms, a coding and Fourier domain iterative optimization method are introduced in the paper. Each pair of real and imaginary part in the Fourier spectrum of an image is coded by a weighted cosine function. Then the binary computer generated hologram corresponds to the coefficient distribution of the cosine extension. Moreover we define a Fourier domain mean-squared error between the Fourier spectrum of an image and the binary computer generated hologram. By minimizing the Fourier domain mean- squared error iterative, we can implement the hologram coding and optimization.

This paper introduces a scheme whereby complex holography is realized as computer generated holograms. Complex holography is based on the complex amplitude of the wavefront using an additive representation of a real part and imaginary part. Two types of hologram are needed, but no conjugate image is produced. Conventional holography can avoid the effects of conjugate images only by using a display/recording device with very high resolution, but this solution is not available to electro-holography. The conjugate image, which is always generated from the original image simultaneously, makes the reconstructed image very noisy. Complex holography involves decomposing the complex value of each pixel into the real and imaginary parts of the pattern. Each interference pattern is displayed on a different display device, and illuminated by coherent lights. At this time, the coherent lights differ only in terms of phase, the phase difference is (pi) /2 radians. The summation of the two diffraction patterns regenerates the complex wavefront while eliminating the conjugate object light wave-front. This paper first mathematically confirms the principle of the proposed method. Next, experimental simulations in which synthesized images are clearly reconstructed are described. In addition, an experimental system is demonstrated that uses two LCD panels.

We describe the implementation of a system which enables a user to interact with and modify an electronic holographic image using a force-feedback device. The force-feedback (or haptic) device is capable of sensing and reporting the 3D position of its hand-held stylus and displaying appropriate forces to the user. Thus, a user can feel and modify algorithmically specified shapes in the haptic workspace. We precisely register the haptic workspace with the free- standing, spatial image displayed by the MIT second-generate holographic video system (holovideo). In the coincident visuo-haptic workspace, a user can see, feel, and interact with synthetic objects that exhibit many of the properties one expects of real ones, and the spatial display enables synthetic objects to become a part of the user's manipulatory space. To the best of the authors' knowledge, this is the first time that such an interactive holographic system has been built.

This report is concerned with a stereovision system using holographic optical element (HOE). The authors introduce a natural 3D display system that provides the observer the clear stereoscopic vision without glasses. Even though both eyes of the observer are arbitrary located at the focuses of the stereovision system, he can be satisfied to look at the suitable 3D images. It is important that the focuses are not restricted at the specific points but occupy more broad areas. Such a mechanism is realized by the method of exposing with the diffractive plate. Moreover the authors are interested in a deep stereovision system. The system with four focuses is described to provide the adequate focuses in the accordance with his distance from the object. This system has HOE of multiple focuses that makes two pairs of viewing points in the back and forth locations. In this system four original images are projected from the behind of the HOE. All images join at the HOE and advance for the schemed focuses.

A novel design of the diffraction grating cell used as a pixel on a 3D display is proposed. When illuminating the display, we can observe parallax images from corresponding directions through the diffractive function of each grating cell. Because the small grating cell is designed usually as a binary grating filling a small rectangle area, the first order diffracted light from each pixel has a broadened diffraction intensity distribution. The diffracted light which exists outside the geometrically projected area is so- called `feet' of the diffraction pattern. The feet result in crosstalks in the 3D display between the images from adjacent pixels corresponding to the other viewing angles. It is better for the diffracted light from each cell to have a flat distribution in a desired area on an observation plane, and zeros in the surroundings. We introduce a spherical wavefront generation and an apodization in the grating cell design to realize arbitrary extent of the diffracted light with diminishing feet. As a result, a 3D display consisting of the grating cells designed in this manner can reconstructed 3D images with less crosstalks than that of the binary case.

A display system requiring no special glasses is a useful technology for 3D images. The authors have researched real- time holographic stereogram displays using a holographic screen. In June 1995, we presented the stereoscopic 3D display system with viewing apertures such as conventional two-step holographic stereogram. In 1996, we introduced the stereoscopic 3D color display system using a holographic pseudo-color technique. Last year at the 1997 conference on Practical Holography, the authors presented the stereoscopic 3D display system based on a reconstruction of parallax- rays. These systems consist of a liquid crystal device and a holographic screen formed of holographic optical elements. These systems can construct animated 3D images in real-time by updating LCD pixels. In this paper, the latest result of our study about a stereoscopic 3D display system is proposed. In addition, this paper presents the result of a holographic stereogram movie system as a future 3D display.

In order to reproduce the natural color of object on color display devices, such as CRT and LCD (liquid crystal display), the saturation of the reproduced color is limited by the gamut of the display device. This paper presents a method to increase the color gamut by using more than three primary colors generated by a holographic optical element (HOE). The light diffracted by HOE is used to generate multiprimary colors, and the color image with extended color gamut is displayed by LCD device. Both transmission- and reflection-type systems suitable for projection displays are proposed, and the capability of increasing the gamut is discussed. The experimental result using transmission-type HOE is also demonstrated.

The procedure of manufacturing of a diffuse screen for the projection of 3D images that reproduce the horizontal parallax only is presented. The optical properties of such screen are considered. The screen represents a diffusor that is capable of scattering the light in the vertical direction only. The screen is fabricated by means of photographical recording of a pattern of speckles generated by a vertical luminous thin line. The details of the chemical treatment of the exposed photograph of the pattern are considered. The measurements of optical properties of the screen have shown that the chemical treatment ensured the suppression of the zero order in the scattered light. The mechanism of 3D image projection when using the screen is considered.

This report presents automatic data reduction techniques for determining bullet and fragment volumes, positions, and momenta from holograms of bullets penetrating armor. The holography technique and the computer data reduction methods are described. Initial results are shown and sources of error in the technique are described. 2D digital images of the hologram are computationally combined by running a backprojection algorithm to produce a 3D array that represents the space containing the bullet and fragments. Thresholding the numbers in this space from the backprojection algorithm produces a representation of the bullet and fragments. Methods of automatically counting the voxels (3D picture elements) that occur in separated fragments have been programmed. These programs also find the centroids and shapes of the fragments and determine velocity using timing information. Volume errors are 40% in current results. These errors could be reduced to less than 3% if the described error sources were eliminated. Future work to improve the algorithms and the holographic process is described.

Holographic Interferometry has been successfully employed to characterize the materials and behavior of diverse types of structures under stress. Specialized variations of this technology have also been applied to define dynamic and vibration related structural behavior. Such applications of holographic technique offer some of the most effective methods of modal and dynamic analysis available. The technology is non-destructive, real-time, and definitive in allowing the identification of vibrational modes, displacements, and motion geometry. Structures and processed materials can be analyzed with very low amplitude excitation and the resultant data can be used to adjust the accuracy of mathematically derived structural models. Holographic Interferometry has offered a powerful tool to aid in the development and analysis of new designs for in-the-ear hearing aid technology. Engineering applications such as this must consider that the microscopic components and the mounting structures in these devices are highly susceptible to unwanted acoustic vibration and structure borne noise. These undesirable effects are detrimental to both the operation and overall behavior of this sort of device. The requirement for measurement of small vibration, modal, and mechanical motions are ideal requisites for analysis using advanced holographic methods in initial design and subsequent test. Holographic methods are non-destructive, real-time, and definitive in allowing the identification of vibrational modes, displacements, and motion geometries. Such information can be crucial to the determination of mechanical configurations and designs as well as operational parameters of in-the-ear hearing aid structures.

The mechanical behavior of satellite telescope structures, subjected to non-uniform heating, as this occurs in orbit, is examined. In the laboratory, temperature gradients are created either by resistors or by IR lamps. Telescope structures are made of a material of very low thermal expansion coefficient--INVAR or carbon-carbon composite--in order to cope with stringent long term stability requirements in relation to temperature variation. Real time holographic interferometry is used to disclose the micro- deformation of the telescope. A careful implementation of the method is necessary, since, within the fixed temperature range for this study, very small deformations are expected. Monitoring of the heating conditions is achieved by an IR camera and thermocouples. Maps of temperature and of the corresponding interferometric out-of-plane deformation are obtained in parallel. The dynamic phase shifting technique allows to produce time-sequences of such deformation maps. These movies, and the temperature/deformation maps, highlight the structure deformation in a quantitative and dynamic way and suitably determine whether the structures meet their specifications.

This paper presents a planewave approximation based method to calculate the HPO hologram patterns of a 3D object. The proposed method, unlike the holographic stereogram, takes Fourier transform of horizontally sliced 2D images without the projection process, which makes it possible to reconstruct a higher resolution image with depth information. Starting from the ray-tracing based conventional digital hologram, we makes the derivation of the proposed method where the need for the segmentation of a hologram is described. From the computational point of view, we show the proposed method is quite advantageous over the conventional hologram, especially for wide horizontal viewing visualization. Finally, simulation results obtained by both methods are compared.

We have been making researches on 3D displays using computer-generated holograms (CGHs). We use an image setter with a resolution of 5080 dots per inch to record the binary CGH patterns. It is possible to reconstruct CGHs with light- emitting diodes or light bulbs which have small emitting segments. In the reconstruction with a light bulb, color- smeared images are observed due to the white light. In order to improve this dispersion, we considered a method to apply a color filter to the CGH. And, we propose a method to make computer-generated color hologram which can reconstruct color point light sources, by combining RGB color filters with the stripe CGHs corresponding to each color.

We present results of investigations of modern cw-laser diodes, emitting in the red spectral range from 635 nm to 670 nm with power from 5 mW to 100 mW for recording and reconstructing reflection and transmission holograms. High- quality reflection holograms were recorded in silver halide materials and in DuPont photopolymers. We demonstrated a brilliant reconstruction of transmission holograms with a depth of image up to 3 m.

This paper is concerned with illumination systems for fluctuating the images of rainbow holograms by an LCD projector and a wide mirror array. The authors introduce the early display systems developed for fluctuation holograms. These systems are not enough to fluctuate them arbitrarily because the locations or the angles of their light sources are fixed or cyclically varied. The authors developed an illumination system by which the observer can see the image of the hologram fluctuated like under the natural environment. An LCD projector and a lens-mirror array are used in the illumination system. The lens-mirror array is composed of about 400 small mirrors pasted over with thin concave lenses. The beam projected out of the LCD projector covers the lens-mirror array. The beam reflected by the lens-mirror array is centered for the hologram panel fixed above the LCD projector. When the highlight zone from the LCD projector is continuously moved on the lens-mirror array, the image of the hologram is smoothly fluctuated. In the case of a large holographic optical lens panel instead of the lens-mirror array, the illumination system becomes more simple. The time to adjust the position of the hologram and the angle of the holographic optical lens panel is extremely reduced. Although the bright area is limited around the zone of the mid height, the movement of the rainbow hologram becomes more natural. Next the authors prepared a multiple exposed hologram that was recorded multiple images like a stereogram. This case realized that the image of the hologram is fluctuated more complicatedly because the multiple images are reconstructed by the multiple illuminations.

A compact display was designed for white-light-transmission (WLT) holograms (30 cm X 40 cm). The unit, measuring 40 cm X 40 cm X 15 cm, contains a tungsten halogen bulb and a folded play-back beam, providing an aesthetically pleasing alternative to the usual large space needs of WLT holograms. The inevitable availability, in the near future, of red, green and blue diode lasers will bring the possibility of their use in the play-back of full-color transmission holograms. In this paper I explore the recording and playback requirements as well as several approaches for future display designs.

A new type of display equipped with a transparent screen was proposed. One can see the background of the display through the screen on which the information is displayed. The see- through display was constructed by two main components; a polymer dispersed liquid crystal (PDLC) panel and an illuminating unit with an edge-lit hologram. The OFF pixels in the scattering mode of the PDLC were illuminated by monochromatic light from the illuminator to display necessary information and/or patterns. The other part of the display was clear and the background was observed through the display because the ON pixels as well as the illuminator were transparent. The design to realize the multi-color display as well as the process to make quality edge-lit holograms were also discussed.

As the interest of holographic stereogram in the 3D displays is increased, the application of this technique has been suggested in several fields. Especially, in architecture, 3D bird's-eye view can be replaced instead of building models. In this paper, the possibility of application is proposed and demonstrated it in architectural perspective presentation. Using computer graphics, we can create an object that has 3D information, but it is only 2D when projected on a screen or CRT. Dividing these computer- generated graphic objects into several views aspects (2D images) and then synthesize them onto holographic film. A geometrical method is used to calculate sampling angles, and a TFT LCD is used to display the 2D images. Using a big size of collimating mirror and films, we made a holographic stereogram, which is 600 X 400 mm².

Holographic hard-copy techniques suffers from a lack of availability for ordinary users of computer graphics. The production of holograms usually requires special skills as well as expensive equipment which means that the direct production cost will be high for an ordinary user with little or no knowledge in holography. Here it is shown how a system may be created in which the users of computer graphics can do all communication with a holography studio through a Java-based web browser. This system will facilitate for the user to understand the technique of holographic stereograms, make decisions about angles, views, lighting etc., previsualizing the end result, as well as automatically submit the 3D-data to the producer of the hologram. A prototype system has been built which uses internal scripting in VRML.

A full color reflection type holographic screen having the spectral range of reflection, 470 to 620 nm is made of DuPont photopolymer film type OmniDex 706 with color tuning film CTF-75-24.6 by controlling the tuning process to have the chirp type fringes. A small size diffuser is used to modify the reference beam in a single beam recording scheme to increase the viewing zone size of the screen. Intermodulation fringes due to the diffuser do not deteriorate the performances of the screen because of insensitivity of photopolymer to large period fringes. The screen shows very low level of scattering when looking through it. The screen has both properties of a diffuser and a spherical mirror.

We will discuss the prototype of Head Mounted Display using Holographic Optical Element in this paper. It is obvious that a single HOE can record the multiple optical images by the characteristic in itself, that is angular selectivity and wavelength selectivity. Therefore, it is very easy to understand the HOE has the function which can separate the stereoscopic images onto the left and right eyes, like as the conventional HMD. In this report, we propose the prototype of HMD using a single HOE, and we will extract the problem in application of the real industrial field, especially manufacturing and designing. Consequently, we proved that the HMD using Lippmann hologram has the potentiality of miniaturization, lightening, wide field of vision. This HMD can be suitable in the Virtual Reality field. But it is necessary to adjust the pupil distance and the incident angle of conjugate beam precisely.

We have been developing various holographic optical elements (HOEs) and holograms. In this paper holographic light control films (HLCF's) for use with reflective monochromatic type liquid crystal displays (LCDs) are discussed. The HLCFs are volume type holograms which diffract selected wavelengths of the ambient light to specific angles. Using HLCF's as reflectors in conjunction with LCDs allows the concentration of reflected light to specific viewing areas. Three beneficial characteristics of HLCFs, weak dependence upon incident light angles, good control of diffracted color and excellent environmental stability are described. (1) Weak dependency on incident light angles: Specially designing master holograms and replication conditions allows the production of HLCF's only depend weakly on the angle of the incident light. (2) Control of diffracted color: Varying process conditions allows the creation of HLCF's which diffract specific colors. (3) Stability during and after environmental tests: Using DuPont photopolymers resulted in good stability for both low and high temperatures and high humidity test conditions. In addition, the TEM pictures of the cross sections were shown.

Reflection hologram for recording deep and blur-less images has been proposed. The reconstruction image, which was floating at more than 30 cm in front of the hologram, was mono-color and observed from wide longitudinal angles when illuminated by an extended white light source such as fluorescent lamp. Multi-color images can be easily obtained by multiplexing the holograms with different wavelengths. One step recording method was found useful to record a 2D object such as a transparency and to represent the arbitrary color when it was combined with the pseudo-color technique. The concept of the proposed hologram can be extended to a projector system for displaying off-screen images.

This report presents some examples of holographometry (holographic measurements) applications in science and industry: automatic control of spatial water solution concentration during crystal growth providing large homogeneous (industrial) crystals such as KDP, DKDP, and alike; detection and measurement of defects in the natural crystals, grown crystals and precious stones (brilliants); optimization of blood refrigeration process to prevent cell damage; measurement of the shape of live erythrocytes and lenslet array parameters; flow velocity distribution in spillway of river dams; distribution of droplets in diesel engine sprayers; investigation of electric wire explosions (modeling the real explosions); detection and measurement of the static and dynamic objects located behind non- transparent media.

This paper presents a technique for realizing the Joint Transform Correlator in real time using a Barium Titanate crystal and a low power He-Ne laser. This technique avoids the use of additional CCD camera and electrically addressed SLM, and provide high fidelity correlation peak. The phenomenon of Degenerate Four Wave Mixing is used for image correlation in this experiment. The object and reference are arranged in a single beam and the Joint Fourier Transform is focused in the crystal. Fourier Transform of the conjugate beam gives the required correlation. The peaks are recorded with the help of low light sensitive CCD camera for further analysis for determining the exact location of the target.

This report describes the physics education at Tama art university and Tokai university (Japan) for using display holography. More than 30 years ago, we started this program of physics education. At the first step, students visited the holography exhibition and were making holograms, within 1.5 hours, by means of the hand-made holography camera using a simple optical set-up. The electro holography was useful for the students to understand the basic theory of holography absolutely.

A method of application of pulsed holographic interferometry together with the associated hardware has been developed and applied as a non-destructive inspection (NDI) tool for application to aluminum aircraft fuselages such as those used in the present air transport fleet. A number of novel techniques are involved in the design features of the holographic camera and the method of excitation to obtain optimum conditions where any structural faults present can be made apparent. The holographic camera system has been designed to be small, portable and ruggedly designed so it is suitable for field operations in aircraft repair stations and hangars. The technique operates by the introduction of a selected single frequency vibration signal into the area undergoing test. The camera system has been designed to record both the relative and actual phase of the vibrationally induced into the structure of the fuselage undergoing excitation and NDI. Results are presented showing structural defects. A computerized technique is being developed for the analysis of the interferogram fringe maps an preliminary results are discussed.

An instant holographic portrait printing system has been developed. The system consists of a capturing camera, a high-speed image processing device, and a desktop one-step holographic stereogram printer. It takes less than 3 minutes to obtain a horizontal parallax 3D image 78 mm X 59 mm on DuPont photopolymer film HRF700X071-20, including capturing and image processing time. Since the holographic stereogram printer is designed for easy operation under non-laboratory conditions, an anti-vibration table or a dark room is not required. We describe several key technologies as well as a practical method for evaluating the image quality produced by one-step hologram printers.

Discussed the system of holographic disc memory. This memory uses the overlapping expanded partial holograms on the moving disc and collinear optical heterodyning for data readout. Discussed the requirements to holographic materials for realization of this system. By selection of materials we used the signal and noise characteristics for different materials (silver halide, dichromated gelatin etc.). By development of materials we used the method of registration latent holographic images. Discussed the technological problems by realizing of materials and holographic memory. The experimental results are demonstrated.