Yoshinori Kajiki

New approach to the interactive holographic display system

This paper presents a new type of the interactive holography display system which features both dynamic and precisely detailed imaging. The main discussion is on synthesis of electronic holograms and optical holograms. Electronic holograms have benefits of dynamic imaging of computer generated 3D objects in essence. On the other hand, conventional optical holograms are known to be suitable for detailed and precise imaging. Considering that many images typically contain objects which dynamically move around on the still background, synthesis of electronic holograms and optical holograms has high potential that the currently limited electronic holograms are applied to a wide range of applications. The second discussion of this paper is about the possibility of producing computed holograms in real time. Computation time of generating holographic fringe patterns with a parallel computer CYBERFLOW is considerably reduced by using techniques such as parallel computation with and within 64 processing elements, vectorized computation, scalar computation simultaneously in parallel with vector computation, and simultaneous computation with data transfer to the output display device. The obtained result is 84.7 times as fast as a conventional computer and promises the possibility of the real time computer generated hologram.

Three-dimensional shape measurement using images reconstructed by the computer from a hologram

Laser holographic interferometry has been developed to provide a direct optical transonic flow diagnostic tool. It is often convenient, due to the needs of passage instrumentation and blade fixtures, to restrict optical access to one side of the test facility. To overcome this limitation a reflective holographic system has been devised which uses one of the internal tunnel walls as a mirror surface. However, due to the movement of the facility, spurious rigid body vibration information is added to the transonic flow data. A numerical method has been developed by Warwick University and demonstrated on the Laval nozzle flow facility at EPFL which uses a digital fast Fourier transform algorithm to remove the superimposed background information. A further method known as phase unwrapping is used to extract quantitative numerical data from the interferometrically formed images automatically. A complication to the experiment was created by the non-linear deflection of glass window between the two holographic exposures. The deflection was determined experimentally to be of a parabolic nature and has been successfully removed. This was achieved by post processing the unwrapped fringe data.

Cylindrical large computer-generated holograms and hidden-point removal process

We have been making researches on 3D displays using computer-generated holograms (CGHs). Our CGHs are binary Fresnel holograms that reconstruct point light sources and are recorded by using high resolution laser printers (image setters). The image setters have the resolution of 3600 or 5080 dots per inch (7.1 or 5.0 micron dot width). The resolution is lower than that of photo reduction, but it has wide drawing area, and it is not expensive to draw large CGH patterns on a high contrast film. In this paper, we present an approach to making cylindrical large CGHs and hidden-point removal process. The number of reconstructible point light sources is considered to be restricted due to the low resolution of the printer. To improve this restriction and to make larger displays, we propose a method arranging plural CGHs cylindrically that reconstruct divided objects. For improving the depth of the objects reconstructed from the CGHs, we consider it is necessary to apply hidden-point removal process to our CGH calculation. Whether a certain point object is visible or not from a point of view depends on the existence of the interference fringes on the CGH plane.

Optical symbolic substitution using lenslet arrays

An optical symbolic substitution using lenslet arrays is presented. By using the shift and the superposition properties of the lenslet array, the recognition and the substitution phases can be performed. The advantages of using the lenslet array for symbolic substitution are efficiency, cascadability, and high resolvability. Experimental demonstrations of the proposed symbolic processor are provided.

Computer-generated color holograms using RGB color filters

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.

An Optical Pattern Classification Using Computer-Generated Holograms

We have proposed an optical pattern classification system which performs weighting and summation by the optical system using computer-generated holograms (CGHs). Our system makes it possible to simplify the structure and to improve the processing speed. We propose a trainable pattern classification system which can perform weight modification by using a CGH matrix and a dot matrix liquid crystal display (LCD) as a shutter array. We describe the trainable pattern classifier using a CGH matrix and LCD, and present the experimental results.

Applications of holographic stereograms by a large liquid crystal display

A fabrication method for holographic stereograms using a large liquid crystal display panel (LCD) is proposed and experimental results are described. Holographic stereogram is a useful method that can synthesize computer graphics or portraits of 2D perspectives but its process is troublesome. An LCD of a lap top personal computer is applied for perspective display. This method has some advantages, e.g., simple optical layout, no registration mechanism, no aberration by projection lenses and so on. A technique to improve the quality of holograms with a holographic optical element is also proposed.

Miniature light bulb reconstructible and large-sized computer-generated holograms recorded with an image setter

Visualization of 3D information or 3D displays are important subjects. We have been researching 3D displays using computer-generated holograms (CGHs). We set our sights on making large and high quality 3D displays. In this paper we present an approach to making large CGHs relatively easily, and at low cost, which are binary Fresnel holograms and are recorded by using a high resolution laser printer (an image setter). By using the image setter it is possible to draw large CGH patterns very easily. Furthermore, we found it was possible to reconstruct CGHs with light-emitting diodes or miniature light bulbs. Making good use of this advantage we propose a method of making larger 3D displays by the multiple comstruction using plural light sources and CGHs.