Tomoyuki Mishina

Viewing-zone enlargement method for sampled hologram that uses high-order diffraction

We demonstrate a method of enlarging the viewing zone for holography that has holograms with a pixel structure. First, aliasing generated by the sampling of a hologram by pixel is described. Next the high-order diffracted beams reproduced from the hologram that contains aliasing are explained. Finally, we show that the viewing zone can be enlarged by combining these high-order reconstructed beams from the hologram with aliasing.

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.

Viewing-Zone-Angle-Expanded Color Electronic Holography System Using Ultra-High-Definition Liquid Crystal Displays With Undesirable Light Elimination

This paper describes a viewing-zone-angle- expanded color electronic holography system using ultra-high-definition liquid crystal displays (LCDs) with undesirable light elimination. The authors first investigate methods eliminating undesirable light, color aberration, and astigmatism. They then investigate spatio-temporal multiplexing methods to reduce system complexity. These investigations enable an electronic holography system to be constructed using 33 Mpixel LCDs. Experimental results show high-quality full-color 3D images with a diagonal size of 4 cm, viewing-zone-angle of 15 deg, and frame rate of 20 fps.

Calculation of holograms from elemental images captured by integral photography.

We describe a method in which holograms can be produced by calculation from images captured by integral photography (IP). We present a basic algorithm obtained by simulating IP reconstruction, in which conditions are set so as not to cause aliasing in the holograms after the calculations. To reduce the calculation load, we also propose a way to limit the range of calculation considering the distribution of light and a way to shift the optical field on the exit plane of microlenses in a lens array. Finally, by optical experiments, we confirm that three-dimensional images can be reconstructed from holograms calculated from an integral photograph of a real object captured with an IP camera.

Real-time color holography system for live scene using 4K2K video system

We are studying electronic holography and have developed a real-time color holography system for live scene which includes three functional blocks, capture block, processing block, and display block. In this paper, we will introduce our developed system after describing basic idea that quickly calculates hologram from IP image. The first block, capture block, uses integral photography (IP) technology to capture color 3-D objects under natural light in real time. The second block, processing block, consists of four 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 all captured IP images by using fast Fourier Transform. The last block, display block, mainly consists of three liquid crystal displays to display the holograms and three laser sources for RGB to reconstruct the color 3-D objects. All blocks work in real time, i.e., in 30 color frames per second.

Wide viewing-zone-angle full-color electronic holography system using very high resolution liquid crystal display panels

A wide viewing-zone-angle full-color electronic holography reconstruction system is developed. Time division multiplexing of RGB color light and space division multiplexing of viewing-zone-angles are adopted to keep the optical system compact. Undesirable light such as illumination light, phase conjugate light, and high-order diffraction light are eliminated by half-zone-plate hologram generation and single sideband beam reconstruction. Color aberration and astigmatism caused by the reproduction optical system are analyzed and reduced. The developed system expands viewing-zone-angle of full-color holographic image three times wider than the original, suppressing undesirable light, color aberration, and astigmatism.

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.

Cross talk elimination using an aperture for recording elemental images of integral photography

A major problem with integral photography using a lens array is overlapping recordings (cross talk) between elemental images. Another problem is the decrease in the number of pixels in the elemental images. We describe two methods (including analyses) of manipulating the aperture of a telecentric optical system to improve these problems. The first method locates the aperture on the focal plane of a field lens. The advantage of this method is that cross talk can be reduced without changing the size of the whole optical system. The second method establishes a telecentric optical system between objects and the lens array. The advantage of this method, even though the whole optical system becomes bigger, is that cross talk can be completely eliminated. In addition, the number of pixels in the elemental images can be increased by varying the aperture position sequentially with respect to time. We also describe how cross talk is reduced in both methods by taking diffraction into consideration. Experimental results are presented to verify this reduction.

Integral imaging system with enlarged horizontal viewing angle

We developed a three-dimensional (3-D) imaging system with an enlarged horizontal viewing angle for integral imaging that uses our previously proposed method for controlling the ratio of the horizontal to vertical viewing angles by tilting the lens array used in a conventional integral imaging system. This ratio depends on the tilt angle of the lens array. We conducted an experiment to capture and display 3-D images and confirmed the validity of the proposed system.

Real-time IP-hologram conversion hardware based on floating point DSPs

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.