We have proposed a high image-quality Lippman type one-step holographic stereogram printer in 1998. However, as with most Lippman holograms, it was difficult to appreciate the quality of the holographic images output from our holographic stereogram printer unless the holograms were illuminated correctly. In order to overcome this problem, we have developed a version of our printer that makes edge-lit transmission holographic stereograms that are designed around the use of a built-in illumination source. In this paper, we describe our method for making transmission edge-lit holographic stereograms. The desired optical system can be obtained by making a small change to the Lippman holographic stereogram printer head. By using this reconfigured optical system, we succeeded in making an instant edge-lit holographic stereogram portrait system. We also describe a cylindrical holographic stereogram as an application of the edge-lit transmission holographic stereogram.

We describe the use of a digital micromirror device (Texas Instruments, Inc.'s DMD^TM) as a spatial light modulator for holographic applications. Questions of the interferometric effects of the moving mirror structure and the appropriateness of pulse-width modulation for grayscale imaging are addressed. Compensation for the particular attributes of DMD imaging has allowed the creation of full-color holographic stereograms of high image quality.

A holographic video system, displaying computer generated Fourier transform hologram is described. The method of Horizontal Parallax Only (HPO) Fresnel CGH is well known. HPO computer generated Fourier transform hologram is basically 2- dimensional hologram. To expand an HPO computer generated Fourier transform hologram algorithm based on the ray tracing is introduced. This algorithm can possibly reduce CGH data amount and CGH calculation time. The experimental result is included, and it shows the reduction of CGH data amount and CGH calculation time. One extra advantage compared with Fresnel CGH is described as well.

Over many years, the subject of computer generation of holograms has been visited in various guises. Historically, the obvious restrictions imposed by computational power and computer generated hologram (CGH) fabrication techniques have placed limits on what can be taken seriously in terms of image complexity. Modern advances in computational hardware and electro-optic systems now permit both the calculation and the manufacture of CGH's of complex 3D objects which fill a significant volume of space. New methods permit the recording to be made within a reasonable timescale. In addition to advancing fixed CGH generation techniques, the motivation for the work reported here includes assessment of design algorithms, modulation strategies and image quality metrics. These results are of relevance for a novel electroholography system, currently under development at DERA Malvern. This paper describes a complete process of data generation, computation, data manipulation and recording leading to practical techniques for the creation of large area CGH's. As a support to the advances in theoretical understanding and computational methods, we describe (in Part II) a new laser plotter technique that enables, in principle, an unlimited size of pixel array to be plotted efficiently with a rigorous estimate of duration of the plot run time. The results reported here are limited to 2048 X 2048 pixels. In this example, the novel switching techniques employed on the laser plotter permit the pixel array to be printed in approximately 1 hour. However, paths towards easily raising the pixel count and its associated printing rate are presented for both the computational engine and laser plotting processes.

As a support to the advances in theoretical understanding and computational methods, we describe a new laser plotter technique that enables, in principle, an unlimited size of pixel array to be plotted efficiently with a rigorous estimate of duration of the plot run time. Developments in laser plotter design are presented that allow the formation of pixellated holographic structures of high precision (c. 1 - 10 micron pixel dia.) with an accompanying high pixel count (e.g. at least up to, and beyond, 10⁴ per side within a square array). The case of absorption holograms offers an easy route to a good quality result. We can then exploit the many tricks of amplitude holography borrowed from lithographic and holographic experience using ultra-fine grain silver halide materials. The problem of exposure quantization and linearization is addressed in a pragmatic fashion. The central issue of why such holograms can tolerate intrinsic diffraction artifacts within each pixel is considered along with the exposure level quantization -- it is difficult to print individual pixels within which the optical density is clinically uniform. We cannot over-estimate the reliability difficulties that can arise in a system designed to print massive arrays of pixels in a serial fashion. The electronic testing involved has to be associated with error-free repeatability and high accompanying switching speeds. This may look easy but it is the major issue that distinguishes serially printed digital holography from the simple one-step parallel process of forming the ordinary hologram.

A method for synthesis of driving RF signal, corresponding to sampled hologram, which allows to minimize the capacity of the display memory, is suggested. With the application of new method required frame-buffer capacity for the current displays can be reduced by the factor 1.8 - 3. We have considered three variants of hologram sampling method for data reduction. It is found that minimum hologram data redundancy can be achieved with Fourier and Image types of holographic stereograms. For given 3-D image resolution a maximum image size, which can be displayed without redundancy is determined as 4...5 cm. Further scaling of the image requires application of the sampling method. With proper improvement of the hardware, application of hologram sampling method provides stable capacity of the display memory a little over 32 MB regardless of the image size. Since the method also permits direct synthesis of driving RF signal, acousto-optical modulators with up to several GHz bandwidth can be employed in electroholographic display.

A new electroholography system is introduced that uses a liquid crystal display, a photorefractive crystal, and a time- sharing display method. By using the photorefractive crystal as a kind of screen through which the hologram is recreated, we can realize high quality, off-axis, and computer-generated holograms. The time sharing approach enables an electronic display device to display 3D objects clearly by breaking them into parts that are displayed in sequential frames. If the fames are cycled at a high enough speed, we see these parts as a single object due to the afterimage effect. This approach relaxes the strict dynamic range requirements that would normally be placed on the electronic display device. The photorefractive crystal suppresses the flicker caused by the time-sharing display method. This paper first describes the time-sharing method. Next, a new experimental 3D-TV system with a photorefractive crystal, strontium barium niobate, is demonstrated. This system confirms the exciting future of electroholography.

We discuss the color hologram of the human object and previous works with monochromatic reconstruction. A two step method of recording the hologram with reconstruction in white light was suggested in 1975 for monochromatic reconstruction of the image. The transmission hologram with low noise was the first step of this recording. In first experiment we used photo plate 8E75 with bleaching for recording of H1 holograms. Selection of recording materials using signal and noise characteristics is shown. The original method of producing low-noise holograms (SHSG process) for H1 process is discussed. The reflection hologram H2 was produced as the second step. For copying of H1 hologram onto H2 hologram in the first experiment we used He-Ne laser and photo plate PE-2, produced in laboratory (predecessor of plate PFG-03). We will discuss different optical setups for recording H1 and H2 hologram. New problems connected with recording color holograms. In first our work on modeling color holograms was used a method of emulsion thickness manipulation in between exposures and He-Ne laser, then system silver halide -- dichromated gelatin and original silver halide materials with color sensitizing. Characteristics of SHSG process for color silver halide materials are shown. Finally simulation recording color hologram and possible applications demonstrated.

In recent years, the study of 3D-display is rapid development and many researchers propose many methods. Holography is best method. But, it is difficult that we developed holographic movie in the future tense. At the present time, stereogram method will make practicable in the near future. These methods can easily make animated 3D image. But this method has one problem; this method is conflict between convergence and accommodation. An observer can't watch 3D-display of this method long time. The authors will solve this problem. The authors proposed the 3D-display system that is used holography and stereogram technology. The proposed system has little conflict between convergence and accommodation. The authors developed this 3D-display system. The developed system has four focuses in horizontal direction. The display parts of the developed system are LCD display because the developed system can play 3D movie. Of cause, this display doesn't have special glasses. But, color of this display is single color. It is red. The authors will develop full color 3D-display. The picture size of this display is about 6 inch and the form of this display is very large. The author will develop small size system and show large size picture.

A new method of 3-D image projection is considered. The recording of the image includes two steps and is performed with the help of conventional photographic methods. At the first stage of the recording the set of aspects of a 3-D scene is registered. At the second stage the set of aspects is transformed into a set of so-called subaspects. At the stage of projection the subaspects are transilluminated by a laser beam that is focused in spot. The beam scans the screen and as a result the matrix of luminous spots is formed. It is shown that when viewing such a matrix, the spectator sees on the screen a two-dimensional image of the scene. When the point of observation is changed, the configuration of the image represented on the screen is changed, too, simulating the changes of the aspects of the scene which take place when viewing a real 3-D object. As a result, the spectator has got the illusion of the 3-D character of the projected image. It is mentioned that the process of scanning the screen by the set of aspects focused in spots is equivalent to simultaneous scanning of the screen by a set of independent thin beams of light, a special 'own' aspect being projected on the screen by each beam of light. The version of the display that reproduces the horizontal parallax only is considered. It is shown that the viewing zone should be stretched in this case in the vertical direction with a help of a one-dimensional diffusing screen. The case when the scanning beam is controlled by a conventional TV signal is analyzed. It is shown that the display is compatible with existing TV systems. An experiment on modeling the display that reproduces the horizontal parallaxes of a 3-D scene only was carried out. A photograph of a speckle pattern which was formed by a diffusing luminous line was used as a one-dimensional diffusing screen. Some data on the chemical treatment of this photograph are presented. The experiment has shown that while stretching the viewing zone in the vertical direction, such a screen practically does not impair the quality of the image of the aspect projected through the screen. The experiment has also confirmed the possibility of the complete elimination of the speckle structure of the projected image by giving small circular movements to the screen.

Fortunately for designers holography is cramped with incredible techniques that describe spatial dimensions, but getting to grips with these techniques can prove a design visualization nightmare unless some prior knowledge of the process is held. To the detriment of display holography, it is becoming increasingly difficult to acquire these skills as many universities and colleges of higher education, such as The Royal College of Art in London, have shortsightedly withdrawn holography from their curriculum. As a student from The Royal College of Art Holography Unit, I had the great advantage of some of the finest holographic training and insight from the teachings of Peter Miller, Robert Munday and Nick Phillips and count myself fortunate that I now make a living from designing and making holograms. However, the evolution of a holographic designer is something that can not be taught in any school or college as evolution is the experience of survival. I would therefore like to take this opportunity to offer a few common sense tips to designers treading a similar path to my own.

We will discuss the characteristics of the Head Mounted Display (HMD) using Holographic Optical Element (HOE) in this paper. We have already proposed that using the HOE we could realize the see-through HMD, that is to say the binocular stereoscopic display. This time we evaluate the influence on the human vision system regarding the optical characteristics of the HOE. The HMD using HOE we proposed so far is the Maxwellian View which is the direct projection on the human retina. When we see something by Maxwellian View, we don't need the focusing of the crystalline lens (ocular accommodation) because the depth field is extremely wide. Therefore our binocular crystalline lens will focus at the vergence point when the Maxwellian View is used on the binocular retina. And we can solve the dissociation of accommodation and convergence which is the basic problem of the conventional HMD. We have made the prototype of HOE which can provide the Maxwellian View on our retina and we have proved that our HOE could separate the binocular images onto left and right eye. In this report, we will introduce the Maxwellian View will change the ocular accommodation optionally according to the convergence when we see the real objects and the virtual objects at the same time. We proved that the HOE which provided the Maxwellian View could solve the dissociation of accommodation and convergence.

The fundamental thinking and the optical implementation of an innovative dot matrix writer that can generate image grating pixels of arbitrary grating pitch and grating orientations on a photoresist plate is presented. In this newly developed system, the incident laser beam is split by a beamsplitter to become two incident laser beams. The two coherent light beams are then focused onto a photoresist plate by an especially designed focusing lens. The grating pitch of the grating pixel formed on the photoresist plate can be varied on-the-fly by translating a set of stages to change the distance of the two coherent light beams before impinging on the focusing lens. Moving a lens on the incident light path to change the convergent angle of the incident light beams can change the spot size of this system. As the grating pixels generated by this dot matrix writer are able to have spot sizes, grating orientation, and grating pitch completely specified by the designer, the image effect by this type of dot matrix writer can exert a pre-specified color at each specific viewing angle. Diffractive images with various visual effects and applications that can be created by using this newly invented system are examined.

The major purpose of this article is to evaluate the various aspects of color composition and color reconstruction by using diffractive technology, i.e. representing color by combining light beams of various spectra generated from shining an incident light beam onto multiple diffractive grating pixels. Using the linearity feature of the CIE chromaticity diagram, it can be shown that the colo representation range encircled by the diffractive technology can cover almost the whole color-visible range that is perceivable by humans. With the advantages of the various characteristics of the CIE diagram, also to be discussed is the newfound freedom of diffractive color-composition technology offered to approach the anti- counterfeit tasks from a brand new perspective. In addition, also detailed is the term metamerism, i.e. the same color that can be composed by using different sets of color spectra, which can be used to facilitate several potential anti- counterfeit approaches. By using a newly developed dot matrix writer, which has a simple and efficient optical configuration to implement on-the-fly grating pitch change, various grating pixels which possess vastly different pitch are used to implement and evaluate the effectiveness of the diffractive color composition technology. Both theoretical analysis and experimental results are presented to examine the potential when a variable pitch dot matrix writer is used.

We present details of a compact highly automated pulsed holographic camera system designed for the rapid production of image-planed white-light-viewable reflection holograms up to a size of 40 X 60 cm. The camera operates in two modes: Mastering and Copying. In the mastering mode a holographic plate (40 cm X 60 cm VRP-M Slavich) is placed in a special plate holder at the front of the main camera unit and two diffusers either side of this plate illuminate the object/subject to be holographed. The reference beam exits from the back of the main camera unit and is directed onto the plate by two small overhead mirrors. In copying mode, a processed holographic master is placed in a special rig and a new plate (VRP-M Slavich) having a size up to 40 cm X 60 cm is placed opposite and parallel to this master. In this mode two beams exit the main camera body at opposite sides and are directed by small tripod-mounted mirrors to illuminate the master and copy plates. The camera system is highly automated, providing instant switch-over from copying to mastering modes and permits digital electronic setting of all beam ratios. Machine options currently under development are discussed which include high-speed film copying and a digital mastering interface.

Results of the development of holographic beamsplitters are reported. Binary and multilevel samples for 630-nm and 530-nm laser light have efficiency of over 70% (over 80% for multilevel ones) and output beam intensity variations of less than 5%. The effect of various errors has been simulated for the process of fabrication of multilevel structures. The use of three-level phase structures for realizing asymmetric output beam pattern is investigated. The possibility to employ 2D acousto-optical structures for making dynamic phase elements (real-time HOEs) is investigated. The output diffraction pattern of an element generated by two perpendicular acoustic waves is computed and the possibility to split the input laser beam is demonstrated. The results of testing an experimental real-time beamsplitter are given and show good agreement with computations. The sample is a LiNbO₃ crystal between the parallel faces of which the acoustic pulse undergoes multiple reflections. The output beam patterns for a combination of a passive and dynamic HOEs are also presented.

The goal of our research is to create the holographic optical element with high value of spectral selectivity, about 0.1 nm. The operating wavelength of the filter is determined by the particular task which it is made for, therefore this wavelength is usually different than the recording wavelength. The theoretical analysis was carried out to determine the requirement for such hologram recording in order to reach the maximal diffraction efficiency. The dependence the required refractive index modulation of the material on the reconstruction wavelength was calculated for both transmission and reflective recording schemes. Standard holographic materials can not be applied for the recording of the spectral filter with high selectivity, because the material thickness must be about millimeter. PDA photomaterial (polymer with diffusive amplification) was applied for recording of these holograms. Experimentally achieved bandwidth of the spectral selectivity contour is 0.5 nm. The dependence of the reconstructed wavelength on the angle of reconstruction for the experimentally obtained specimen was measured, and it occurred higher than for the ordinary diffraction grating. This makes thick holographic gratings recorded in PDA very promising from the point of view of their spectroscopic application as a wavelength demultiplexers in the communication networks and as an optical part of monochromator. The comparison of the characteristics of spectral filter and double monochromator was carried out. Another possible applications of the filter including its usage in solar investigations, stabilizing of laser sources, Raman spectroscopy are also discussed.

In this paper, we propose a new kind of fractal kinetic hologram using fractal hypercomplex model for security purposes. The proposed fractal kinetic holograms consist of a sequence of computer-generated fractal images between which there are self-similarity. And on that basis, we can make 'fractal animated holograms.' The results indicate that the model is quite efficient for synthesis of fractal kinetic images. The generated fractal kinetic holograms can be used in the laser anti-counterfeiting field.

A reflection type hologram recorded by using a lenticular lens sheet with a one step recording method, for two dimensional objects, is proposed. This type of hologram has the same characteristics with a reflection type one recorded by using a slit with a two step recording method and can reconstruct a monochromatic and deep image by using a line shape white light source such as a fluorescent lamp. Illuminating with an LED direct bar, lining up linearly a lot of white light LEDs at regular intervals, a mono-color and sharp image was observed from wide longitudinal angles at more than 50 cm in front of the hologram.

We examined the data compression by transform coding for hologram patterns generated on a computer, to realize effective compression of hologram patterns with extremely huge information. We can't apply conventional 2-D image compression techniques directly to hologram patterns since the statistical properties of hologram patterns are quite different from those of 2-D images. Furthermore, it is not a hologram pattern but an image reproduced from the hologram pattern to be essential in the holography. We have to compress hologram patterns by considering the reproduced image. We found that hologram patterns contain a large amount of unnecessary component to reproduce the image. This should be removed for effective coding. The unnecessary component can be distinguished clearly from the necessary component in the frequency domain. We successfully removed it by bandpass filtering hologram patterns. We apply Karhunen-Loeve Transform (KLT) to the hologram patterns after this preprocessing. In the case of high compression, it is better to allocate more bits to the lower order KLT coefficients than the bits determined by the conventional power-based allocation method. Then, effective coding of hologram patterns is realized and better images are reproduced.

A diffusive color reflector using volume hologram was examined to implement a diffusive reflector to be employed in reflective color LCDs, with high brightness due to gain reflection and with high color purity and high light efficiency. In holographic exposure experiment a micro-lens- array was introduced to generate object lights and to define an abrupt gain profile and to control the magnitude of the angular profile. The DuPont materials were used to obtain high color purity of reflection lights. The high light efficiency was realized by broadening the reflection width to the value of about 100 nm under an optimized color tuning process.

We have been developing various types of holograms. In this paper mass-produced color graphic arts holograms are discussed. The TRUE IMAGE^TM hologram, as it is known in Japan, is a volume-type hologram which diffracts selected wavelengths of the ambient light to selected desired angles. When replicating the TRUE IMAGE^TM, three lasers are used simultaneously or independently. There are four beneficial characteristics of the TRUE IMAGE^TM hologram; (1) Repeatable mass product techniques and few defects: a direct lamination method has been developed. (2) Looking bright and clear under fluorescent light: specially designed masters and replication conditions allows TRUE IMAGE^TM holograms to be seen under fluorescent light. (3) Stable chromaticities: expressing full color by developing objects, paints, mastering process and replication process. (4) Good environmental stability: use of effective adhesive films. In this paper, the first characteristic is mainly discussed.

Comparative study of existent hologram authenticity test devices shows that these devices don't satisfy demands of nowadays. We propose new optical arrangement of the device, reduces some disadvantages of previous ones. We are proposed the optical arrangement of the device to include semiconductor laser, collimating lens, hologram frame, phase mask, objective, and screen. Laser and collimating lens provide collimated beam incidence to the hologram in the frame. The reconstructed wave front directs to the screen through the phase mask and objective. The phase mask is a positive lens matrix. These lenses may be placed in orthogonal, or in hexagonal, or in another order. The objective front main plane and lenses back focal plane are the same. Therefore, light beams will be homocenterical at that plane. Because of finite lens size hologram placement tolerance increases without reconstructed image disappearance. This device may be used for testing authenticity of paper documents, shares, and goods with protection holograms.

In the development of new products there are two parallel lines for the development process to follow; the traditional or 'real,' and the new computer aided or 'virtual.' The traditional line is to develop prototypes that can be used for testing strength, functionality, and visual appearance of the product. In the virtual line digital (CAD) models are developed which can be tested entirely in a computer by simulations e.g., using Finite Element Analysis (FEA) and other tools. For transformation from the real to the virtual world some kind of 3D camera is needed. The shape of the model should be measured together with further data concerning the visual appearance, material properties, etc. We have developed electronic recording techniques for doing this based on the Light-in-Flight technique. This technology has all advantages of holography, i.e., apart from the shape it is also possible to measure how much light is reflected from different parts of the object along with interferometric information, which can give mechanical data for the object. This can be used for example for visualization and to give tactile and haptic information to a virtual reality system about how the object would be perceived by a person touching it.

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. Real-time dynamic testing of the modal and mechanical behavior of aerodynamic control and airfoil structures for advanced aircraft has always required advanced instrumentation for data collection in either actual flight test or wind-tunnel simulations. Advanced optical holography techniques are alternate methods which result in actual full-field behavioral data on the ground in a noninvasive environment. These methods offer significant insight in both the development and subsequent operational test and modeling of advanced exotic metal control structures and their integration with total vehicle system dynamics. Structures and materials can be analyzed with very low amplitude excitation and the resultant data can be used to adjust the accuracy mathematically derived structural and behavioral models. Holographic Interferometry offers a powerful tool to aid in the developmental engineering of exotic metal structures for high stress applications. Advanced Titanium alloy is a significant example of these sorts of materials which has found continually increased use in advanced aerodynamic, undersea, and other highly mobil platforms. Aircraft applications in particular must consider environments where extremes in vibration and impulsive mechanical stress can affect both operation and structural stability. These considerations present ideal requisites for analysis using advanced holographic methods in the initial design and test of structures made with such advanced materials. Holographic techniques are nondestructive, 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 structural components fabricated from advanced and exotic materials. Anomalous behavioral characteristics can be directly related to hidden structural or mounting anomalies and defects. Deriving such information can be crucial to the determination of mechanical configurations and designs, as well as critical operational parameters of structural components fabricated from advanced and exotic materials.

Shearography is a full field interferometric technique for the measurement of small deformation gradients. The main fields of application are non-destructive testing in quality control and material inspection. In both cases the direction of the deformation gradient plays a major role. We present a new image shearing speckle pattern interferometer set-up for simultaneous measurement of two independent deformation gradients equivalent to two shear directions. Herein, we use the polarization effect to separate the two directions. Based on a Michelson interferometer, we placed in one arm an additional polarization beamsplitter (PBS) and an additional mirror. The two orthogonal polarized images can be separated by a further PBS and simultaneously captured by a second camera. Substituting the second PBS with a rotatable polarizator and using only one camera, both sheared images can be recorded in rapid succession. We make use of a liquid crystal cell as a fast rotating polarizator and demonstrate the utility of this new concept with measurements in an industrial environment on a tensile testing machine.

A system for transmission and previsualization of digital data for production of holographic stereograms has been developed. The aim of this system is to help the communication between producers of holographic stereograms and their clients. The client accesses the system through a Java applet, a small program, which is automatically downloaded and run on the clients local computer. The client loads a file in VRML format into the applet and the 3D model is displayed using the VRML browser plug-in usually delivered with WWW browsers. The Java applet overrides the controls of the VRML browser and provides only the manipulations possible and necessary for preparing the hologram production and visualizing the result. The applet permits the client to somewhat modify the scene e.g. by adding lights and manipulating them. After finishing the settings and visualizations of the hologram, the client may save the file with the new settings on her own computer in order to resume work later on. When satisfied she may upload the file with all settings to the hologram producer. The computer of the hologram producer is running a small, specially designed http server which will receive the file from the client for further handling.

The transmission type holographic screen is a special kind of scatterer, which is used to concentrate the light from the projected image into small size spot (viewing zone). As a result, different images can be delivered to each observer's eyes and it is possible to display the stereoscopic images. The most serious problem related with the holographic screen is its high dispersion and aberrations which cause the viewing zone distortions and poor color reproduction in the displayed image, especially in the screen corners. Both of the above mentioned drawbacks become more prominent when the screen size becomes larger. To compensate the screen dispersion, a diffuser in the form of a long narrow stripe directed to the reference beam axis is used for an object. The length and position of the diffuser are calculated to make the reconstructed images of it for all wavelengths of the white light projector to be superposed in the viewing zone. To solve the aberrations problem, a big size screen was composed by mosaicking many sub-screens which were recorded individually in the specially optimized setup. For example, when the sub- screen is recorded for the edge part of the screen, the diffuser was tilted different direction to provide proper superposition of the reconstructed diffuser images. For each sub-screen, the diffuser is tilted such that it is in nearly the same plane with the reference beam axis. The sub-screens are recorded on the holographic photoplates PFG-01 (Russia) with an optical set-up optimized for each sub-screen by adjusting the diffuser position and its tilt angle. All necessary parameters are calculated by considering the light beam path for different wavelengths in the visible spectrum. The size of each sub-screen is 40 X 30 cm². Eight sub- screens are mosaicked to obtain a composite holographic screen with size 80 X 120 cm². The screens have been used to display the full color stereoscopic images from slide projectors. The distances between the projector and the composite screen, and the screen and a viewer are set to 4 m and 3.5 m, respectively.

A chromatically corrected reflective holographic screen is made by stacking two holographic plates with focused mirror properties. This screen has the properties of three equal power spherical mirrors by recording two spherical mirrors on one of the plates. Each of these mirrors is tuned to a corresponding CRT's spectral bandwidth centered at one of the wavelengths 450, 540 and 626 nm. The plate with two spherical mirrors are tuned and chirped its fringe structures to widen its bandwidths. An experimental sample with a dimension of 10 X 8 cm² is recorded on DuPont photopolymer film, HRF- 706-20 such that the images of the exit pupil of a projector's objective by the three holographic spherical mirrors overlap together with a spatial resolution enough for 8-views image display. The image brightness on the screen is about 15 times of that on the standard white diffuser.

In this report, computer-generated holograms (CGH's) which have the ability to reconstruct multi-level 3-D images under white light are described. For trial fabrication of the CGH, an electron beam printing system (EBPS) which is capable of recording interferogram data (IFD) with submicron precision is utilized. Because EBPS is controlled with on-off switching, IFD needs to be transformed into minute rectangle cells with their locations corresponding to the fringe. In our previous report, the intensity of the IFD was quantized into 2 levels with the median threshold, and then transformed into the cells. By this method, the location information of the IFD can be retained, while the intensity information, which is essential to reconstruct the tone of images, cannot. To solve this problem, pulse-width modulation (PWM), in which the intensity is quantized into multi levels is used, then the cell width is determined in proportion to the quantized intensity value, and applied to the IFD transformation. As a result of this experiment, in which 8 leveled PWM is applied to the IFD transformation, a 7 level-shaded pyramid is found to be sufficient, and therefore the effectiveness of the transforming method for reconstructing multi-level 3-D images has been confirmed experimentally.