角江 崇

© OSA 2016. The 3D structure designed by our proposed algorithm can exhibit multiple 2D images to different directions. However, refraction of the light at the glass surface causes the deterioration in the image quality when the original algorithm is implemented on cylindrical or spherical glasses. Therefore, we proposed a refraction-compensating algorithm and performed the computer graphics simulation. We succeeded in showing the effectivity of the proposed algorithm.

© 2014 SPIE. We report frequency estimation of loudspeaker diaphragm vibrating at high speed by parallel phase-shifting digital holography which is a technique of single-shot phase-shifting interferometry. This technique records multiple phaseshifted holograms required for phase-shifting interferometry by using space-division multiplexing. We constructed a parallel phase-shifting digital holography system consisting of a high-speed polarization-imaging camera. This camera has a micro-polarizer array which selects four linear polarization axes for 2 × 2 pixels. We set a loudspeaker as an object, and recorded vibration of diaphragm of the loudspeaker by the constructed system. By the constructed system, we demonstrated observation of vibration displacement of loudspeaker diaphragm. In this paper, we aim to estimate vibration frequency of the loudspeaker diaphragm by applying the experimental results to frequency analysis. Holograms consisting of 128 × 128 pixels were recorded at a frame rate of 262,500 frames per second by the camera. A sinusoidal wave was input to the loudspeaker via a phone connector. We observed displacement of the loudspeaker diaphragm vibrating by the system. We also succeeded in estimating vibration frequency of the loudspeaker diaphragm by applying frequency analysis to the experimental results.

© 2014 . Society for Information Display. All rights reserved. We proposed a real-time time-division color electroholography using parallel calculation on multi graphics processing unit (GPU) system. Finally, we succeed to display a reconstructed color 3-D object of around 4000 points per color in real-time.

We have developed an algorithm which can record multiple two-dimensional (2-D) gradated projection patterns in a single three-dimensional (3-D) object. Each recorded pattern has the individual projected direction and can only be seen from the direction. The proposed algorithm has two important features: the number of recorded patterns is theoretically infinite and no meaningful pattern can be seen outside of the projected directions. In this paper, we expanded the algorithm to record multiple 2-D projection patterns in color. There are two popular ways of color mixing: additive one and subtractive one. Additive color mixing used to mix light is based on RGB colors and subtractive color mixing used to mix inks is based on CMY colors. We made two coloring methods based on the additive mixing and subtractive mixing. We performed numerical simulations of the coloring methods, and confirmed their effectiveness. We also fabricated two types of volumetric display and applied the proposed algorithm to them. One is a cubic displays constructed by light-emitting diodes (LEDs) in 8×8×8 array. Lighting patterns of LEDs are controlled by a microcomputer board. The other one is made of 7×7 array of threads. Each thread is illuminated by a projector connected with PC. As a result of the implementation, we succeeded in recording multiple 2-D color motion pictures in the volumetric displays. Our algorithm can be applied to digital signage, media art and so forth. © 2014 SPIE.

© 2014 . Society for Information Display. All rights reserved. We implemented an algorithm for enlarging the viewing-zone angle of holographic images on GPU with the aim of speeding up the calculation. We achieved results showing that calculations on the GPU were 15 times faster than on the CPU.

© 2014 . Society for Information Display. All rights reserved. We try to display the real-time reconstructed 3-D image consisting of a large number of object points. We propose spatiotemporal division multiplexing electroholography using multi-GPU cluster system with InfiniBand network. Finally, the proposed method realized a real-time reconstructed movie of a 3-D object composed of44,647points.

© 2013 ITE and SID. Real-time electroholography requires the high computational performance. The study of fast parallel computation using excellent cost-effective and general-purpose computer system as multi-GPU system is very important. We proposed the parallel algorithm to compute multiple computer-generated holograms using multi-GPU cluster system with infiniband network simultaneously.

© 2013 ITE and SID. We proposed a real-time time-division color electroholography using a USB-to-Parallel module for simple synchronous control of one-chip RGB LED. The proposed system is low-priced. Host PC can directly synchronize the lighting of one-chip RGB LED with the CGH computation by using Message Passing Interface (MPI).

Computer holography addresses holographic nature on a computer by computing light propagation. Its applications include digital holography, computer-generated holograms and so forth. Acceleration is an important issue because recent computer holography requires real-time processing or large-scale holograms, due to the progress of camera and display devices. In this paper, we present our acceleration techniques for computer holography using hardware (FPGAs, GPUs and Intel XeonPhi) and algorithms. © OSA 2013.

© 2013 ITE and SID. We succeeded in enlarging the viewing zone of a holographic image which was generated from an image captured by integral photography (IP). Although the quality of the reconstructed holographic image was somewhat degraded, we confirmed that we could observe the image of a large viewing zone (∼15 degrees) by using a lens array having a short focal length (2.2 mm).

© 2013 ITE and SID. We tried to display the real-time reconstructed 3-D image consisting of a large number of object points. We propose one-colored time-division electroholography using the persistence of vision. Finally, we succeed to display a reconstructed 3-D image consisting of 44, 647 object points using a NVIDIA GeForce GTX TITAN at 12 fps.

© 2013 ITE and SID. Holographic projection inherently requires no lenses, reconstructs images with high contrast and reconstructs color images with one spatial light modulator. In this paper, we demonstrate a speckle-reduced zoomable holographic projection. This holographic projection realizes the zoom function using a numerical method, called scaled Fresnel diffraction. In addition, the speckle noise of projected images is reduced by the combination of optimized holograms, a lowspeckle laser and a vibrating multi-mode fiber.

We constructed a high-speed four-dimensional (4-D) microscope for dynamically moving biological specimens. By use of parallel phase-shifting digital holography, 3-D behavior and phase distribution were captured at 150,000 frames-per-second. © OSA 2012.

We propose a combination of recording wavelengths of color digital holography using spectral estimation for improvement of color reproduction, and numerically confirmed that the color differences were greatly reduced by the combination. © OSA 2012.

Using parallel phase-shifting digital holography with a high-speed camera, the authors succeeded in phase-shifting interferometry at the rate of 180,000 fraames/s. Motion pictures of three-dimensional image of dynamically moving objects were demonstrated. © 2012 OSA.

Thanks to parallel phase-shifting digital holography system using a high-speed camera, the authors succeeded in recording motion pictures of phase image and three-dimensional image of dynamic object at the rate of 262,500 fraames/s. © OSA 2012.

We succeeded in high-speed imaging of gas flow by means of parallel phase-shifting digital holography. This technique is capable of capturing three-dimensional (3-D) information of object and carrying out phase-shifting interferometry with a single-shot exposure because the interference fringe images in which the information of multiple phase-shifted holograms is spatially multiplexed are simultaneously recorded. We constructed a high-speed phase-shifting digital holography system by employing a quarter-wave plate and a high-speed camera. The image sensor of the camera has an anisotropic polarization-detecting function pixel by pixel. Each pixel of the polarization-detecting function corresponds to each pixel of the image sensor. The phase retardation of the reference wave is determined by the direction of the polarization axis of the each pixel. A compressed gas flow sprayed from a nozzle was set as an object. We attained the reconstructed images of phase variation caused by the gas flow. We also succeeded in phase imaging at the rate of 180,000 frames per second when the number of pixels of the captured image was 128 × 128. Additionally, we also obtained temporal subtraction images of the reconstructed images. The achieved frame rate was the fastest among not only phase-shifting digital holography but also digital holography and phase-shifting interferometry which have been ever reported, for our knowledge. It is expected that parallel phase-shifting digital holography and the constructed system can contribute to 3-D moving picture measurement of dynamically moving objects such as particle flows, shock waves, mechanical vibration, and so on. Copyright © 2011 by ASME.

We propose an optical-path-length-shifting digital holography with single-shot exposure for capturing three-dimensional images of color object. The proposed technique was numerically simulated and its validity was confirmed by evaluating root mean square errors. ©2010 Optical Society of America.

The authors demonstrated a phase-shifting digital holography at the rate of 20000 frames/second, for the first time. Thanks to parallel phase-shifting digital holography, the digital holography system succeeded in three-dimensional imaging for dynamically moving objects. © 2010 Optical Society of America.