This PDF file contains the front matter associated with SPIE Proceedings Volume 7233, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Horizontal-parallax-only holographic stereograms of nearly SDTV resolution (336 pixels by 440 lines by 96 views) of textured and normal-mapped models (500 polygons) are rendered at interactive rates (10 frames/second) on a single dual-head commodity graphics processor for use on MIT's third-generation electro-holographic display. The holographic fringe pattern is computed by a diffraction specific holographic stereogram algorithm designed for efficient parallelized vector implementation using OpenGL and Cg vertex/fragment shaders. The algorithm concentrates on lightfield reconstruction by holographic fringes rather than the computation of the interferometric process of creating the holographic fringes.

A computer generated hologram (CGH) requires a high-resolution device to represent a hologram data. I propose a new three-dimensional display method that has the expanded viewing zone and a large object size with a low-resolution device. Using the method, I developed a portable three-dimensional display system that shows 3D objects in the area of 4x2 cm. The display showed three-dimensional images which were full parallax, autostereoscopic and viewed binocularly. It is small and lightweight enough to carry by a hand. Moreover, it is assembled at a low cost and uses a low-price transparency sheet with 4000dpi.

We propose a new synthesis method for the hologram of 3D objects using multiple orthographic view images captured by lens array. The 3D objects are captured through a lens array under normal incoherent illumination, and their multiple orthographic view images are generated from the captured image. Each orthographic view image is numerically overridden by the plane wave propagating at the direction of the corresponding projection angle and integrated into a single complex value, which constitutes one pixel in the synthesized hologram. By repeating this process for all orthographic view images, we can generate the Fourier hologram of the 3D objects. Since the proposed method generates the hologram not from the interference with the reference beam, but from the multiple view images, coherent system is not required. The manipulation of the 3D information of the objects is also easily achieved in the proposed method. By manipulating coordinate information of each orthographic view image according corresponding view angle, the depth order of the reconstructed 3D object can be controlled.

Holography is a 3-D display method that fully satisfies the visual characteristics of the human eye. However, the hologram must be developed in a darkroom under laser illumination. We attempted hologram generation under white light by adopting an integral photography (IP) technique as the input. In this research, we developed a hardware converter to convert IP input (with 120×66 elemental images) to a hologram with high definition television (HDTV) resolution (approximately 2 million pixels). This conversion could be carried out in real time. In this conversion method, each elemental image can be independently extracted and processed. Our hardware contains twenty 300-MHz floating-point digital signal processors (DSPs) operating in parallel. We verified real-time conversion operations by the implemented hardware.

Holography is thought as a revolutionary science for imaging and display. With the commercialization of LCD and DMD projectors, the quality of the imaging screen becomes more and more important to the future display technology. In this paper, we propose to use the holographic lens array as the imaging screen of the projectors. Basic principle, details of implementation and the influence to the future display technology are described.

To compete with other digital images, holograms must go beyond the current range of source-image types, such as sequences of photographs, laser scans, and 3D computer graphics (CG) scenes made with software designed for other applications. This project develops a set of innovative techniques for creating 3D digital content specifically for digital holograms, with virtual tools which enable the direct hand-crafting of subjects, mark by mark, analogous to Michelangelo's practice in drawing, painting and sculpture. The haptic device, the Phantom Premium 1.5 is used to draw against three-dimensional laser- scan templates of Michelangelo's sculpture placed within the holographic viewing volume.

We propose a method generating elemental images for the auto-stereoscopic three-dimensional display technique, integral imaging, using phase-shifting digital holography. Phase shifting digital holography is a way recording the digital hologram by changing phase of the reference beam and extracting the complex field of the object beam. Since all 3D information is captured by the phase-shifting digital holography, the elemental images for any specifications of the lens array can be generated from single phase-shifting digital holography. We expanded the viewing angle of the generated elemental image by using the synthetic aperture phase-shifting digital hologram. The principle of the proposed method is verified experimentally.

In order to enlarge the image size and viewing zone angle of a hologram, an image generated by a high-speed spatial light modulator (SLM) is converted into a vertically long image by an anamorphic imaging system, and this image is scanned horizontally by a galvano scanner. The reduction of the horizontal pixel pitch of the SLM provides a wide viewing zone angle. The increase of the image height and horizontal scan enlarge the image size. In this study, a digital micromirror device (DMD) with the resolution of 1,024×768 was used as a high-speed SLM. A laser diode with the wavelength of 635 nm was used as a light source. An anamorphic imaging system had the magnifications of 0.183 and 5.0 in the horizontal and vertical directions, respectively, to generate a vertically long image with the size of 2.56 mm×52.5 mm. The horizontal pixel pitch was reduced to 2.5 μm to provide the horizontal viewing zone angle of 15°. The horizontal scan width of the galvano scanner was 73.1 mm, so the resultant image size was 73.1 mm×52.5 mm. The scanning frequency of the galvano scanner was 60 Hz and the frame rate of the DMD was 13.333 kHz so that one hologram consisted of 222 vertically long images. The vertically long images were displayed with the horizontal pitch of 0.32 mm and there were substantial overlaps. We succeeded the generation of a hologram image having 15° horizontal viewing zone angle and 3.5" screen size with a 60 Hz frame rate.

In recent years the field of digital holography became an attractive research area following the developments of CCD-arrays and an ever increasing computational power of computers. Here we investigate digital holography reconstruction methods and compare them for the accuracy and the computational speed. In addition, possible discrepancies in the calculation of the diffraction integral via fourier transform is clarified and it is compared to convolution methods. The proper evaluation of discrete Fresnel diffraction equation is demonstrated by creating artificial holograms and numerically reconstructing them. Simulation results and experimental work is presented.

The laser microbeam uses lasers to alter and/or to ablate intracellular organelles and cellular and tissue samples, and, today, has become an important tool for cell biologists to study the molecular mechanism of complex biological systems by removing individual cells or sub-cellular organelles. However, absolute quantitation of the localized alteration/damage to transparent phase objects, such as the cell membrane or chromosomes, was not possible using conventional phase-contrast or differential interference contrast microscopy. We report the development of phase-contrast digital holographic microscopy for quantitative evaluation of cell dynamic changes in real time during laser microsurgery. Quantitative phase images are recorded during the process of laser microsurgery and thus, the dynamic change in phase can be continuously evaluated. Out-of-focus organelles are re-focused by numerical reconstruction algorithms.

A novel technique is presented for calculating large-scale CGHs by using polygon-based method. In the technique, wave fields are regionally segmented and propagated by using the shifted Fresnel method. As a result, large CGHs can be calculated even in the case that the whole frame buffer can not be stored in main memory. The produced full-parallax CGH has the size of four billion pixels and reconstructs the fine image of a smooth surface object accompanied with a strong depth sensation.

This paper is dedicated to THz pulse holography with reference beam, opposite to our last year report on THz pulse holography without reference beam1. With reference source, we can use not only wavefront inversion modelling for reconstruction, but also reconstruction by shorter wavelength radiation that is much easier to be viewed. Using almost the same setup as in THz holography with reference beam, after digital registration we can reproduce hologram at the desired THz wavelength scaled to the desired reconstruction wavelength, then, we use standard scheme for reconstruction. Taking into account time needed for computational reconstruction, the new approach looks promising especially for practical purposes. A comparison between reconstruction techniques related to resolution and noise dependency is given.

This report presents the results of computer simulation images for image-type Computer-Generated Holograms (CGHs) observable under white light fabricated with an electron beam lithography system. The simulated image is obtained by calculating wavelength and intensity of diffracted light traveling toward the viewing point from the CGH. Wavelength and intensity of the diffracted light are calculated using FFT image generated from interference fringe data. Parallax image of CGH corresponding to the viewing point can be easily obtained using this simulation method. Simulated image from interference fringe data was compared with reconstructed image of real CGH with an Electron Beam (EB) lithography system. According to the result, the simulated image resembled the reconstructed image of the CGH closely in shape, parallax, coloring and shade. And, in accordance with the shape of the light sources the simulated images which were changed in chroma saturation and blur by using two kinds of simulations: the several light sources method and smoothing method. In addition, as the applications of the CGH, full-color CGH and CGH with multiple images were simulated. The result was that the simulated images of those CGHs closely resembled the reconstructed image of real CGHs.

A cylindrical hologram is well known to be viewable in 360 deg. This hologram depends high pixel resolution.Therefore, Computer-Generated Cylindrical Hologram (CGCH) requires huge calculation amount.In our previous research, we used look-up table method for fast calculation with Intel Pentium4 2.8 GHz.It took 480 hours to calculate high resolution CGCH (504,000 x 63,000 pixels and the average number of object points are 27,000).To improve quality of CGCH reconstructed image, fringe pattern requires higher spatial frequency and resolution.Therefore, to increase the calculation speed, we have to change the calculation method. In this paper, to reduce the calculation time of CGCH (912,000 x 108,000 pixels), we employ Graphics Processing Unit (GPU).It took 4,406 hours to calculate high resolution CGCH on Xeon 3.4 GHz.Since GPU has many streaming processors and a parallel processing structure, GPU works as the high performance parallel processor.In addition, GPU gives max performance to 2 dimensional data and streaming data.Recently, GPU can be utilized for the general purpose (GPGPU).For example, NVIDIA's GeForce7 series became a programmable processor with Cg programming language.Next GeForce8 series have CUDA as software development kit made by NVIDIA.Theoretically, calculation ability of GPU is announced as 500 GFLOPS. From the experimental result, we have achieved that 47 times faster calculation compared with our previous work which used CPU.Therefore, CGCH can be generated in 95 hours.So, total time is 110 hours to calculate and print the CGCH.

Effects of the light-modulation characteristics of a LCD panel on the image reconstruction are discussed. Experimental results show that the optical images are lower in quality than the numerical ones reconstructed from the same hologram. Effects of the bit-depth limitation in quantization, and the phase change of modulated light are studied by the numerical simulation. Simulation results indicate that the nonlinear characteristics of the LCD panel and the phase change of amplitude-modulated light can have considerable influences upon the quality of images. Especially, the contrast of images becomes low. The static or the dynamic characteristics are measured for LCD panels by using the holographic technique, and their effects on the image reconstruction are discussed. New methods are also described for improving the quality of images reconstructed from the holographic display. The nonlinear response of the LCD panel and the phase change of modulated light can be made correction for the improvement of image quality by modifying the complexamplitude hologram.

This paper describes a new class of recording materials for volume holographic applications suitable to meet commercial manufacturing needs. These next-generation holographic photopolymers have the ability to satisfy the unmet demand for color and depth tuning that is only possible with volume holograms. Unlike earlier holographic photopolymers, these new materials offer the advantages of no chemical or thermal processing combined with low shrinkage and detuning. Furthermore, these materials exhibit high transparency, a high resolution of more than 5000 lines/mm and are environmentally robust. Bayer MaterialScience plans to commercialize these materials, which combine excellent holographic characteristics with compatibility to mass-production processes. In this paper, we will briefly discuss the potential markets and applications for a new photopolymer, describe the attributes of this new class of photopolymers, relate their ease of use in holographic recording, and discuss potential applications of such materials..

Volume holographic gratings have recently attracted interest as wavelength-selective devices, for applications such as wavelength stabilizers for laser diode sources. These thick gratings are usually produced using various photosensitive materials like photo-thermo-refractive glass and specially prepared polymers. These materials often require two or more process steps for production of volume holographic gratings. In this study several copolymers with MethylMethAcrylate as base material are compared. Unlike commercially available PMMA, the polymers have a glass transition temperature up to 155 °C, which enables the use on higher laser powers. The refractive index of the polymer is modified using 325-nm-radiation. The polymers were not sensitized by peroxidation prior to irradiation, and after the irradiation process, no development was needed. The gratings were recorded with both a Lloyd mirror setup and the well-known phase mask method. The gratings produced have a calculated refractive index variation in the range of 10^-5. The reflection characteristics were measured with a modified Michelson interferometer and a tunable laser source. Volume holographic gratings with extremely narrow bandwidth and angular selectivity can be produced on some of the polymers. The production cost of the gratings is low and they can be used for multiple applications such as wavelength tuning and wavelength selection of diode lasers at high power levels.

The formation of phase and surface relief gratings in low-molecular-weight organic glasses containing azobenzene moieties has been studied with holographic methods. Advantages of this class of materials are the simple synthesis, the perfectly amorphous phase, and the possibility of blending them with polymers. Surface relief gratings are formed very efficiently in molecular glasses, and this process can be explained by the gradient force model. Heights up to 610 nm were measured; the temporal evolution of the diffraction efficiency could be reproduced in computer simulations. For technical applications, the surface relief gratings can easily be duplicated by replica molding. Since surface gratings are detrimental to holographic data storage at high densities, it is also possible to suppress their formation by using proper polarizations of the writing beams. Reorientation of the azobenzene groups in the bulk of the glasses and angular multiplexing was demonstrated and the thermal stability of the corresponding phase gratings was studied. Different combinations of molecular cores and substituents at the azobenzene moieties were investigated to find the best systems which yield a high sensitivity and fast grating build-up.

This paper describes a new closed form of the matrix elements by using T-matrix method. This formulation is useful expression because T-matrix element is presented in the analytical form of the Bessel function series. The energy convergence does supply a numerical consistency check at less than 1[%] in percentage power error. Numerical examples are illustrated for diffraction efficiencies which the incident angle and profile for holographic Fourier gratings are variable. If the profile of a grating is chosen appropriately, the diffraction efficiency can be checked by becoming more than 80[%] at TE and TM polarization.

We propose a new method of calculating the reflectance distribution on object surfaces for computer-generated holograms to improve the reality of reconstructed images, which takes into consideration reflection on the surfaces of metallic objects. It is based on the Blinn or the Torrance-Sparrow reflection model that has been established in computer graphics. Moreover, we also take into account the Fresnel equation for the method, which provides the degree of reflection on metallic surfaces. We adapted this model to the process of calculating computer-generated holograms, so that various reflectance distributions could be derived. In our experiments, we carried out comparison theoretical and simulated intensity distributions, optical reconstructed experiments, and computer simulations. As a result, we obtained the reflectance distributions of reconstructed images by using the new approach.

A new method of the lens-less holographic microscope is proposed for recording a high-resolution 3-D image with large visual depth. The light beam with a large viewing angle diffracted from the object surface is recorded by illuminating the three-dimentional object with a large incidence angle. A number of partial holograms are sequentially recorded with one CCD located at the fixed position by changing an incident angle of illumination light. These partial holograms are arranged in order to generate a hologram with large viewing-zone angle for the reconstruction of a high-resolution image. Optical experiments are carried out to demonstrate the present new method of the holographic microscope. Results show that a high-resolution image is reconstructed from the wide hologram generated from a number of partial holograms and the resolving power of reconstructed image is improved as the number of partial holograms becomes large.

A new technology of one-shot digital holography is developed for instantaneous recording of the complex-amplitude hologram for color three-dimensional images. Three holograms for different phases of the reference light are obtained both by spatially sampling an off-axis hologram and by interpolating sampled hologram data, and the complex-amplitude hologram is extracted from these three holograms. The one-shot holography is generalized for recording the hologram with the reference light having general phase distribution, and the limitation of bandwidth in one-shot holography is also discussed. Numerical simulation and optical experiment are carried out to demonstrate one-shot recording of the complex-amplitude hologram. Results show that fine color images with high resolution are reconstructed from the complex-amplitude hologram as a result of perfect elimination of the direct beam, the zero-order noise and the conjugate beam. The one-shot digital holography can make possible to record color images of the moving object by adopting RGB pulse lasers, and to reconstruct moving color images in real-time with the holographic display

We report an all-optical switching transmission grating fabricated by holographic polymer dispersed liquid crystal (HPDLC) technique. The all-optical switching ability is achieved by doping the nematic LC with azobenzene. The trans-cis deformation of doped azobenzene under the irradiation of pumping light induces the phase transformation of the phaseseparated LC microdomains and further creates an index modulation environment to switch the grating efficiency. We also observe the grating formation by monitoring the diffracted intensity at different writing laser power. An optimum of writing power (150 mW/cm²) is required to get maximum diffraction efficiency.

In this paper, we propose a new approach for fast generation of computer-generated holograms (CGHs) of a 3-D object by using the run-length encoding (RLE) and the novel look-up table (N-LUT) methods. With the RLE method spatially redundant data of a 3-D object are extracted and re-grouped into the N-point redundancy map according to the number of the adjacent object points having the same 3-D value. Then, basing on this redundancy map N-point principle fringe patterns (PFPs) are newly calculated by using the 1-point PFP of the N-LUT (novel look-up table) and the CGH pattern for the 3-D object is generated with these N-point PFPs. In this approach, object points to be involved in calculation of the CGH pattern can be dramatically reduced and as a result an increase of computational speed can be obtained. Some experiments with a test 3-D object are carried out and the results are compared to those of the conventional methods.

We propose a new method of synthesizing computer-generated holograms (CGHs) at an arbitrary viewpoint from multi-view images under a natural light environment. This method generates a CGH of an arbitrary viewpoint using multi-view images from randomly arranged cameras. The method is based on a distance transformation and a rotation of a light wave. The distance transformation interpolates a ray on the space, and the rotation is achieved using a shift on the frequency space. A hologram was made using our method, and we confirmed that optical reconstruction enabled us to reconstruct images of full-parallax.

We are studying electronic holography and have developed a real-time color holographic movie system which includes three functional blocks, capture block, processing block, and display block. We will introduce the system and its technology in this paper. The first block, capture block, uses integral photography (IP) technology to capture color 3-D objects in real time. This block mainly consists of a lens array with approximately 120(W)x67(H) convex lenses and a video camera with 1920(W)x1080(H) pixels to capture IP images. In addition to that, the optical system to reduce the crosstalk between elemental images is mounted. The second block, processing block, consists of two general personal computers to generate holograms from IP images in real time. Three half-zone-plated holograms for red, green and blue (RGB) channels are generated for each frame by using Fast Fourier Transform. The last block, display block, mainly consists of three liquid crystal displays for displaying the holograms and three laser sources for RGB to reconstruct the color 3-D objects. This block is a single-sideband holography display, which cuts off conjugate and carrier images from primary images. All blocks work in real time, i.e., in 30 frames per second.

A novel approach for discrimination of partially occluded 3-D target objects from reconstructed digital hologram by using a spatial filtering scheme is proposed. Because of the distance condition among the target and occluding objects in the digital hologram system, the occluding objects would directly act as some noises to the reconstructed target image as a result performance of the digital hologram based 3-D target recognition system might be severely deteriorated. When we just focuse on the occluded image for recognition, sometimes we do not know the shape exactly. But if we extract the occluding objects from the hologram pattern, it is recognized more clearly when we reconstructed. Because of the property of hologram, some pixel does not have information what we want and other pixels have it. In accordance with it, we are able to discriminate the shape of occluded object even though the part of occluded object is not brightly and clearly. In this paper, by selectively subtraction the occluding object noises from the recorded hologram pattern using a spatial filtering scheme, robust discrimination of 3-D targets from the occluding objects can be realized with this spatial filtered hologram. Thus, performance of the proposed digital hologram based 3-D target recognition system can be dramatically improved. In order to show the feasibility of the proposed method, some experiments with test objects are carried out and the results are presented.

We have been investigating the computer-generated disk hologram (CGDH). Since general flat format hologram has the limited viewable area, we usually cannot see the other side of the reconstructed object. Therefore, we proposed the computer-generated cylindrical hologram (CGCH) to realize the 360 degrees viewable hologram. However, the CGCH has the special shape, it is difficult to construct the CGCH and the calculation amount is too large. In contrast, a disk type hologram is also well known as the 360 degrees viewable hologram. Since the disk hologram is the reflective type flat hologram, the setup of reconstruction is very easy. However, there was few report of the disk hologram by the computer-generated hologram. Due to the lack of the spatial resolution of our output device, the hologram cannot provide the large diffraction angle. In addition, the viewing zone is depended on the hologram size (of course, the maximum size of the fringe pattern is decided on the special frequency of the out put device), the calculation amount is also large (calculation amount of the CGDH is about quarter of the CGCH). In our previous study, the computer-generated disk hologram was realized. However, since the relation between the vertical viewing zone and reconstructed image size is trade-off, the size of the reconstructed image and view zone is not enough for practical use. Therefore, to improve both parameters, we modified the fringe printer to output the high resolution fringe pattern for the disk hologram.

We propose a novel optical cryptography of gray-level information image using QPSK digital modulation method and digital holographic technique. A gray-level information image is digitized into 8-bits binary information data by ASCII encoding method and these binary information data are expressed by four pair of quadrature phase values in a block having 2×2 pixels by QPSK digital modulation. After encoding and modulation, the size of data to be encrypted expands two times more than the original size of gray-level image. The modified information with corresponded phase values is displayed on a phase-type spatial light modulator and is encrypted with a security key by using optical digital holography. The security key is expressed with random binary phase. Digital hologram in this method is Fourier transform hologram and is recorded on CCD camera with 256 gray-level quantized intensities. These encrypted digital holograms are able to be stored by computer and be transmitted over a communication network. With this encrypted digital hologram, the phase values are reconstructed with the same security key by holographic technique and are decrypted into the original gray-level information image by decoding. Simulation results show that the proposed method can be used for a cipher and security system.

In the case of projection type display[1], it needs to use the screen in order to project the image clearly and wide viewing angle. We have been developing the projection type display system using the mist screen[2-4]. However, the image with mist screen was flickered by gravity and air flow. Then we considered to reduce the flicker of the image and we found that flicker can be reduced and viewing angle became more large. This time we report the large viewing angle projection type display system using screen made up with very small particle size smoke and flow controlled nozzle. Hence, at first we considered the most suitable particle for the screen and then the shape of screen and then we constructed the array of flow controlled smoke screen. By the results of experiment we could get considerably high contrast flicker-less image and get the viewing angle more than 60° by this flow controlled nozzle attached new type smoke screen and moreover we can get the step-in type display with this method and make clear the efficiency of this method.

We have developed a glasses-type color computer generated hologram (CGH) by using a color filter. The proposed glasses consist of two "lenses" made of overlapping holograms and color filters. The holograms, which are calculated to reconstruct images in each primary color, are divided to small areas, which we called cells, and superimposed on one hologram. In the same way, colors of the filter correspond to the hologram cells. We can configure it very simply without a complex optical system, and the configuration yields a small and light weight system suitable for glasses. When the cell is small enough, the colors are mixed and reconstructed color images are observed. In addition, color expression of reconstruction images improves, too. However, using small cells blurrs reconstructed images because of the following reasons: (1) interference between cells because of the correlation with the cells, and (2) reduction of resolution caused by the size of the cell hologram. We are investigating in order to make a hologram that has high resolution reconstructed color images without ghost images. In this paper, we discuss (1) the details of the proposed glasses-type color CGH, (2) appropriate cell size for an eye system, (3) effects of cell shape on the reconstructed images, and (4) a new method to reduce the blurring of the images.

Significant enhancement of the thermal stability of the hologram recorded on photochromic materials had been achieved via covalent bonding of the photochromic dye to the polymer matrix as compared to the host-guest systems. One time partial reduction of the hologram's initial diffraction efficiency due to thermal exposure was observed for both - polymers with attached dye as well as host-guest materials. Such one time reduction is interpreted to be due to the thermal relaxation of the polymer network induced with photochromic transition in the dye molecule. A gradual hologram erasure at elevated temperatures was observed for the host-guest system, which is assumed to be due to dye's diffusion between highly lit and dark areas. At temperatures ca. 100 °C there was no detectable diffusion type degradation of the hologram after 6 hours of exposure to elevated temperature. Same heating of the hologram in photochromic host-guest polymer led to a full hologram erasure within 40 minutes. In both cases the one time reduction of the diffraction efficiency (DE) due to matrix relaxation and heat adjustment had comparable value of about 0.5 of hologram's initial DE.

Volume holographic properties of diarylethene doped polymers are reported for the first time. Resolution of more than 1500 lines/mm with ▵n about 10^-4 is demonstrated on a sample 1 mm thick. Angular selectivity contains two contributions - the wide one from the amplitude holographic component, and the sharp one from the phase counterpart. The half-width of the amplitude component is about order of magnitude larger than that of the phase component. High fatigue resistance of the dye allows multiple record/erase cycles without degradation. Thermal stability of the dye allows for durability of the recording material at the temperatures above 115 °C. Holograms while stable at room temperature exhibit thermal degradation at elevated temperatures even below 115 °C. This gives potential to implement on that material multiple use holographic thermal sensors.