Ichiro Yuyama

Real-time pickup method for a three-dimensional image based on integral photography.

We studied integral photography (IP), which creates three-dimensional autostereoscopic images. In particular we studied the possibility of a new method that uses a television camera to shoot directly numerous real images produced by a lens array. Unlike the conventional IP method in which the film is placed immediately behind a lens array, this method employs a television camera, which enables us to shoot moving pictures. Of a number of factors affecting the process of image pickup, we examined some optical factors and compared them with those obtained by the conventional IP method. The results show that with this new direct pickup method that uses a television camera, we can obtain an IP image like those obtained by using the conventional IP method. Further, we conducted an experiment with an high-definition TV camera, confirming the production of an autostereoscopic image by using a display device that combines a liquid-crystal panel and pinholes.

Gradient-index lens-array method based on real-time integral photography for three-dimensional images

Because a three-dimensional (3-D) autostereoscopic image can be seen from a desired viewpoint without the aid of special viewing glasses, integral photography (IP) is an ideal way to create 3-D autostereoscopic images. We have already proposed a real-time IP method that offers 3-D autostereoscopic images of moving objects in real time by use of a microlens array and a high-definition television camera. But there are two problems yet to be resolved: One is pseudoscopic images that show a reversed depth representation. The other is interference between the element images that constitute a 3-D autostereoscopic image. We describe a new gradient-index lense-array method based on real-time IP to overcome these two problems. Experimental results indicating the advantages of this method are shown. These results suggest the possibility of using a gradient-index lens array for real-time IP.

Three-dimensional video system based on integral photography

A three-dimensional (3-D) video system based on integral photography is proposed. In this system, real erect images of an object are formed by a gradient-index (GRIN) lens array as elemental images and are directly captured by a television camera. A large-aperture convex lens is introduced in front of the GRIN lens array to control the depth range of the reproduced image. The video signal of a group of elemental images is transmitted to a display device that combines a liquid crystal panel and an array of convex microlenses, producing a color 3-D image in real time. As a result, full-color and autostereoscopic 3-D images with full parallax can be observed. We confirmed the possibility of a 3-D television system.

Time-alternating method based on single-sideband holography with half-zone-plate processing for the enlargement of viewing zones

The single-sideband method of holography, as is well known, cuts off beams that come from conjugate images for holograms produced in the Fraunhofer region and from objects with no phase components. The single-sideband method with half-zone-plate processing is also effective in the Fresnel region for beams from an object that has phase components. However, this method restricts the viewing zone to a narrow range. We propose a method to improve this restriction by time-alternating switching of hologram patterns and a spatial filter set on the focal plane of a reconstruction lens.

A study on the relationship between shooting conditions and cardboard effect of stereoscopic images

In this paper, we examine the cardboard effect by varying such image acquisition parameters as lighting intercamera distances, lens focal length, and presence or absence of motion parallax and backgrounds in program production. Subjective evaluation tests show that binocular disparity calculated from camera-separation lens selection and convergence point are dominant factors. The cardboard effect can be effectively avoided or lessened by enhancing increasing the binocular parallax. In case of actual program production, it is practical to use standard lenses or ones close in focal length to standard lenses, and to set camera separation around the same as the average eye separation of human eyes in order to mitigate the cardboard effect. When binocular disparity is small using lenses with long focal length, other cues, such as motion parallax accompanied by the relative movement between subjects and cameras, are effective.

A study on resolution and aliasing for multi-viewpoint image acquisition

We equate multi-viewpoint image acquisition with object sampling from different viewpoints, and calculate the resolution of multi-viewpoint camera systems. Aliasing, which occurs with the sampling, leads to depth shifting of objects. For instance, an image of a distant object may be taken as if it were near when aliasing occurs. A condition of the camera pitch free from aliasing is discussed. An appropriate prefilter for the sampling can eliminate alias-causing spatial-frequency components, even when the camera pitch is large. We analyze the characteristics of the prefilters from the aspects of depth shifting, ghosting, and waveform distortion. The experimental results show that a prefilter, which reduces ghosting, can be realized optically. For precise acquisition of multi-viewpoint images, however, a prefilter with electrical processing is needed.

Combination enlargement method of viewing zone for computer-generated holography

We have developed a new system based on computer-generated holography using a hologram plane with a sampling structure like a liquid crystal display. This system can eliminate beams from conjugate images and enlarge the viewing zone, which are achieved by combining the following two methods. The first method enlarges the viewing zone by using higher- order diffraction beams generated because of the sampling structure of the hologram plane. If the angle between the object beam and the reference beam is larger than the angle determined by the sampling period on the hologram plane, aliasing occurs in the fringe patterns. In this method, the viewing zone is enlarged by using a spatial filter to extract the object beams from the higher-order diffraction beams generated from aliasing and then combining them. The second method is a modification of the single-sideband method that is known to eliminate the conjugate beams and to restrict the viewing zone to a narrow range. The modified method improves this restriction by dividing the range of the object beams and reproducing each of them. This paper presents the developed system, and the results of experiments that confirmed the effectiveness of this system in enlarging the viewing zone.

A study on scanning methods for a field-sequential stereoscopic display

This paper focuses on the scanning methods of a field-sequential stereoscopic display system. We examined the advantages and disadvantages of several scanning methods to identify the most suitable one for the field-sequential stereoscopic display technique. An evaluation test using a system with 525 scanning lines and a 120-Hz field frequency was conducted. The results show that the picture quality of the 4:2 or 4:1 interlace method, which maintains high vertical resolution, is superior to that of the simple 2:1 interlace one. We also developed an experimental field-sequential stereoscopic system for HDTV with 1:2 interlacing and confirmed that it is possible to display high-quality stereoscopic HDTV pictures in full 1125-line vertical resolutions.

Real-time three-dimensional pickup and display system based on integral photography

A real-time three-dimensional (3-D) pickup and display setup called a Real-time IP system is proposed. In this system, erected real images of an object are formed by a GRIN lens array as element images, and are directly shot by a television camera. The video signal of a group of element images is transmitted to display device that combines a liquid crystal panel display and a convex micro-lens array, producing a color 3-D image in real-time. Full-color and autostereoscopic 3-D images with full-parallax can be observed. We confirmed the possibility of the 3-D television system.

Time Sensitive Evaluation of the Quality of Digitally Coded Sequences

The authors have developed an experimental device suitable for verifying whether assessors can subjectively evaluate temporal variations in picture quality. They also developed a technique suitable for processing opinion scores obtained by means of their device. This new method, the single-stimulus temporally continuous evaluation (SSTCE) method, can solve some problems associated with the single-stimulus continuous quality evaluation (SSCQE) method recommended by the ITU-R, and is more effective for evaluating the time-varying quality of television sequences.