角江 崇

© 2017 Proceedings of the International Display Workshops. All rights reserved. Japanese students have a problem of low motivatbn for science courses. In order to solve this problem, we developed a simulator about the planets that works on the 2D display in previous study. In this study, help the stereoscopic recognition of students by operating the simulator in VR.

© 2017 Proceedings of the International Display Workshops. All rights reserved. A method to design "a 3D object containing multiple 2D infonnation patterns", which can exhibit different motion pictures to different directions, has been developed. However, it is difficult for humans to decide the placement of threads. In this study, we aim for realization of a simulator for a practical projection system to a directional volumetric display. The simulation results by our simulator was similar to the actual projection results. As a result, we confirmed that the simulator we developed is correct.

© 2017 Proceedings of the International Display Workshops. All rights reserved. We propose a method for the phase recovery of a three-dimensional object from axial diffraction patterns using ptychographical iterative engine. The phase recovery using conventional phase retrieval methods under spherical illumination is difficult. The proposed method can retrieve the phase of an object under both planar and spherical wave illuminations.

For a three-dimensional display using computer-generated holograms (CGHs), fast CGH calculations are required. The multiple wavefront recording planes (WRPs) method can reduce the computational amount by placing WRPs near an object. In previous studies using this method, the numbers and intervals of the WRPs were fixed. Hence, the calculation time was heavily affected by calculation conditions, such as variation in the distribution of object points. This paper proposes a method that can automatically optimize the number and arrangement of WRPs to accelerate CGH generation. (C) 2016 Optical Society of America

Parallel calculations of large-pixel-count computer-generated holograms (CGHs) are suitable for multiple-graphics processing unit (multi-GPU) cluster systems. However, it is not easy for a multi-GPU cluster system to accomplish fast CGH calculations when CGH transfers between PCs are required. In these cases, the CGH transfer between the PCs becomes a bottleneck. Usually, this problem occurs only in multi-GPU cluster systems with a single spatial light modulator. To overcome this problem, we propose a simple method using the InfiniBand network. The computational speed of the proposed method using 13 GPUs (NVIDIA GeForce GTX TITAN X) was more than 3000 times faster than that of a CPU (Intel Core i7 4770) when the number of three-dimensional (3-D) object points exceeded 20,480. In practice, we achieved similar to 40 tera floating point operations per second (TFLOPS) when the number of 3-D object points exceeded 40,960. Our proposed method was able to reconstruct a real-time movie of a 3-D object comprising 95,949 points. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

This is the first study to demonstrate that colour transformations in the volume of a photochromic material (PM) are induced at the intersections of two control light channels, one controlling PM colouration and the other controlling decolouration. Thus, PM colouration is induced by position selectivity, and therefore, a dynamic volumetric display may be realised using these two control lights. Moreover, a mixture of multiple PM types with different absorption properties exhibits different colours depending on the control light spectrum. Particularly, the spectrum management of the control light allows colour-selective colouration besides position selectivity. Therefore, a PM-based, full-colour volumetric display is realised. We experimentally construct a mixture of two PM types and validate the operating principles of such a volumetric display system. Our system is constructed simply by mixing multiple PM types; therefore, the display hardware structure is extremely simple, and the minimum size of a volume element can be as small as the size of a molecule. Volumetric displays can provide natural three-dimensional (3D) perception; therefore, the potential uses of our system include high-definition 3D visualisation for medical applications, architectural design, human-computer interactions, advertising, and entertainment.

This study reviews fast algorithms and hardware implementations of computer holography, including computer-generated holograms and digital holography. To reduce the calculation time, which is mainly consumed by diffraction calculation, fast algorithms and hardware implementations are highly necessary and will ensure the further development of this field.

We propose two calculation methods of generating color computer-generated holograms (CGHs) with the random phase-free method and color space conversion in order to improve the image quality and accelerate the calculation. The random phase-free method improves the image quality in monochrome CGH, but it is not performed in color CGH. We first aimed to improve the image quality of color CGH using the random phase-free method and then to accelerate the color CGH generation with a combination of the random phase-free method and color space conversion method, which accelerates the color CGH calculation due to down-sampling of the color components converted by color space conversion. To overcome the problem of image quality degradation that occurs due to the down-sampling of random phases, the combination of the random phase-free method and color space conversion method improves the quality of reconstructed images and accelerates the color CGH calculation. We demonstrated the effectiveness of the proposed method in simulation, and in this paper discuss its application to lensless zoomable holographic projection. (C) 2016 Optical Society of America

Surgery under endoscopic vision has advantages such as lower invasiveness, less bleeding, and less pain for patients, providing expanded vision for precise operation compared with open abdominal surgery. To improve preservation of normal tissue and flexible utilization of ultrasound imaging, water-filled laparoendoscopic surgery (WaFLES) has been actively researched. In WaFLES, the abdominal cavity is filled with saline instead of insufflated with carbon dioxide gas. The circulating irrigating solution maintains desirable moisture and temperature for organs as well as provides a clear endoscopic view. By buoyancy effect, the organs are floating and easy to move during surgery, but organs around the surgical field often affect the surgeon's view. We propose a novel surgical spacer for WaFLES based on reversible structural alteration between two- and three-dimensional shapes, which is designed to be inserted through a single small incision and expanded in the abdominal cavity independently. We designed and fabricated prototypes of the proposed spacer made of polyvinyl chloride and polyethylene terephthalate, and tested their structural strengths. The prototypes demonstrated the required strength to withstand the forces loaded from organs around the treated area under WaFLES conditions.

A three-dimensional (3D) structure designed by our proposed algorithm can simultaneously exhibit multiple two-dimensional patterns. The 3D structure provides multiple patterns having directional characteristics by distributing the effects of the artefacts. In this study, we proposed an iterative algorithm to improve the image quality of the exhibited patterns and have verified the effectiveness of the proposed algorithm using numerical simulations. Moreover, we fabricated different 3D glass structures (an octagonal prism, a cube and a sphere) using the proposed algorithm. All 3D structures exhibit four patterns, and different patterns can be observed depending on the viewing direction. (C) 2016 Optical Society of America

A three-dimensional (3D) structure designed by our proposed algorithm can simultaneously exhibit multiple two-dimensional patterns. The 3D structure provides multiple patterns having directional characteristics by distributing the effects of the artefacts. In this study, we proposed an iterative algorithm to improve the image quality of the exhibited patterns and have verified the effectiveness of the proposed algorithm using numerical simulations. Moreover, we fabricated different 3D glass structures (an octagonal prism, a cube and a sphere) using the proposed algorithm. All 3D structures exhibit four patterns, and different patterns can be observed depending on the viewing direction. (C) 2016 Optical Society of America

In this paper, we show fast signal reconstruction for compressive holography using a graphics processing unit (GPU). We implemented a fast iterative shrinkage-thresholding algorithm on a GPU to solve the l(1) and total variation (TV) regularized problems that are typically used in compressive holography. Since the algorithm is highly parallel, GPUs can compute it efficiently by data-parallel computing. For better performance, our implementation exploits the structure of the measurement matrix to compute the matrix multiplications. The results show that GPU-based implementation is about 20 times faster than CPU-based implementation. (C) 2016 Optical Society of America

We propose an optical encryption framework that can encrypt and decrypt large-sized images beyond the size of the encrypted image using our two methods: random phase-free method and scaled diffraction. In order to record the entire image information on the encrypted image, the large-sized images require the random phase to widely diffuse the object light over the encrypted image; however, the random phase gives rise to the speckle noise on the decrypted images, and it may be difficult to recognize the decrypted images. In order to reduce the speckle noise, we apply our random phase-free method to the framework. In addition, we employ scaled diffraction that calculates light propagation between planes with different sizes by changing the sampling rates. (C) 2015 Elsevier B.V. All rights reserved.

We demonstrated holographic multi-projection using the random phase-free method and the iterative method. Holographic multi-projection is a method of projecting multiple different images focused on different screens at the same time. The random phase-free method succeeded in improving the image quality. By applying the iterative method to the random phase-free method, the image quality was improved further. The results of our numerical reconstruction and optical experiments confirm that the proposed method improves the image quality. The peak signal-to-noise ratios of the reconstructed images using the proposed method and the conventional method are 30.66 and 13.61 dB, respectively. (C) 2016 Optical Society of America

We report speeding-up of calculation of the reconstruction processing in digital holography in order to realize realtimemultispectral digital-holographic high-speed imaging flow cytometry. We adopted digital holography which applies spatialfrequency-division multiplexing method to recording of red-, green-, and blue-color holograms. Because the reconstructionprocessing takes 1.6 ms by using GPU computing, we estimated from the calculation results that the imaging- flow-cytometrysystem could realize 2,500 cells/s as measurement throughput.

We succeeded in improving the image quality of a color reproduction image by using random phase-free method. This method enabled the zoom of the reproduction image without lens. Conventional color computer-generated hologram was applied random phase to enlarge reproduction image regardless of hologram size. However, the random phase generated speckle noise and degraded the reproduction image. Computer-generated hologram was encoded with Frank code and Schroeder code to reduce a speckle noise at the time of reproduction. The both method need lens to expand reproduction image in optical system. In this paper, we used random phase-free method to improve the reproduction image. As the result of simulation and experiment with optical system, we succeeded in improving the image quality and enlarging the color reproduction image.

折りたたまれた平面から，二つの端点を引っ張るだけで強固な立体形状を形成する手法が本研究グループで開発されている．この技術を天体教育に応用し，教材を試作した．中学3年生の授業で使用したところ，良好な評価を得た．

Surgery under endoscopic vision has advantages such as lower invasiveness, less bleeding, and less pain for patients, providing expanded vision for precise operation compared with open abdominal surgery. To improve preservation of normal tissue and flexible utilization of ultrasound imaging, water-filled laparoendoscopic surgery (WaFLES) has been actively researched. In WaFLES, the abdominal cavity is filled with saline instead of insufflated with carbon dioxide gas. The circulating irrigating solution maintains desirable moisture and temperature for organs as well as provides a clear endoscopic view. By buoyancy effect, the organs are floating and easy to move during surgery, but organs around the surgical field often affect the surgeon's view. We propose a novel surgical spacer for WaFLES based on reversible structural alteration between two- and threedimensional shapes, which is designed to be inserted through a single small incision and expanded in the abdominal cavity independently. We designed and fabricated prototypes of the proposed spacer made of polyvinyl chloride and polyethylene terephthalate, and tested their structural strengths. The prototypes demonstrated the required strength to withstand the forces loaded from organs around the treated area under WaFLES conditions.

© 2016 IEEE. Computer-generated holograms (CGHs) are core technology in electroholography systems; however, heavy and enormous calculations are required for calculating CGH. We have developed algorithms for decreasing the computational cost in CGH. We introduce three of our works for the rapid calculation of CGHs and compare the results.

Random phase is required in computer-generated hologram (CGH) to widely diffuse object light and to avoid its concentration on the CGH; however, the random phase causes considerable speckle noise in the reconstructed image and degrades the image quality. We introduce a simple and computationally inexpensive method that improves the image quality and reduces the speckle noise by multiplying the object light with the designed convergence light. We furthermore propose the improved method of the designed convergence light with iterative method to reduce ringing artifacts. Subsequently, as the application, a lensless zoomable holographic projection is introduced.

Computer-generated holograms (CGHs) are core technology in electroholography systems; however, heavy and enormous calculations are required for calculating CGH. We have developed algorithms for decreasing the computational cost in CGH. We introduce three of our works for the rapid calculation of CGHs and compare the results.

This paper shows the process used to calculate a computer-generated hologram (CGH) for real scenes under natural light using a commercial portable plenoptic camera. In the CGH calculation, a light field captured with the commercial plenoptic camera is converted into a complex amplitude distribution. Then the converted complex amplitude is propagated to a CGH plane. We tested both numerical and optical reconstructions of the CGH and showed that the CGH calculation from captured data with the commercial plenoptic camera was successful. (C) 2015 Elsevier B.V. All rights reserved.

The cosine function is a heavy computational operation in computer-generated hologram (CGH) calculation; therefore, it is implemented by substitution methods such as a look-up table. However, the computational load and required memory space of such methods are still large. In this study, we propose a simple and fast cosine function approximation method for CGH calculation. As a result, we succeeded in creating CGH with sufficient quality and made the calculation time 1.6 times as fast at maximum compared to using the look-up table of the cosine function on CPU implementation. (C) 2015 Optical Society of America

We propose real-time time-division color electroholography using a single graphics processing unit (GPU) and a simple synchronization system of reference light. To facilitate real-time time-division color electroholography, we developed a light emitting diode (LED) controller with a universal serial bus (USB) module and the drive circuit for reference light. A one-chip RGB LED connected to a personal computer via an LED controller was used as the reference light. A single GPU calculates three computer-generated holograms (CGHs) suitable for red, green, and blue colors in each frame of a three-dimensional (3D) movie. After CGH calculation using a single GPU, the CPU can synchronize the CGH display with the color switching of the one-chip RGB LED via the LED controller. Consequently, we succeeded in real-time time-division color electroholography for a 3D object consisting of around 1000 points per color when an NVIDIA GeForce GTX TITAN was used as the GPU. Furthermore, we implemented the proposed method in various GPUs. The experimental results showed that the proposed method was effective for various GPUs. (C) 2015 Optical Society of America

Our proposed method of random phase-free holography using virtual convergence light can obtain large reconstructed images exceeding the size of the hologram, without the assistance of random phase. The reconstructed images have low-speckle noise in the amplitude and phase-only holograms (kinoforms); however, in low-resolution holograms, we obtain a degraded image quality compared to the original image. We propose an iterative random phase-free method with virtual convergence light to address this problem. (C) 2015 Elsevier B.V. All rights reserved.

Digital holography has the twin image problem that unwanted lights (conjugate and direct lights) overlap in the object light in the reconstruction process. As a method for extracting only the object light, phase-shifting digital holography is widely used; however, this method is not applicable for the observation of moving objects, because this method requires the recording of plural holograms. In this study, we propose a twin-image reduction method by combining the "periphery" method with the "random phase-shifting" method. The proposed method succeeded in improving the reconstruction quality, compared to other one-shot recording methods ("parallel phase-shifting digital holography" and "random phase-shifting"). (C) 2015 Elsevier B.V. All rights reserved.

We demonstrate an aerial projection system for reconstructing 3D motion pictures based on holography. The system consists of an optical source, a spatial light modulator corresponding to a display and two parabolic mirrors. The spatial light modulator displays holograms calculated by computer and can reconstruct holographic motion pictures near the surface of the modulator. The two parabolic mirrors can project floating 3D images of the motion pictures formed by the spatial light modulator without mechanical scanning or rotating. In this demonstration, we used a phase-modulation-type spatial light modulator. The number of pixels and the pixel pitch of the modulator were 1,080 x 1,920 and 8.0 mu m x 8.0 mu m, respectively. The diameter, the height and the focal length of each parabolic mirror were 288 mm, 55 mm and 100 mm, respectively. We succeeded in aerially projecting 3D motion pictures of size similar to 2.5 mm(3) by this system constructed by the modulator and mirrors. In addition, by applying a fast computational algorithm for holograms, we achieved hologram calculations at similar to 12 ms per hologram with 4 CPU cores.

We propose a random phase-free kinoform for large objects. When not using the random phase in kinoform calculation, the reconstructed images from the kinoform are heavy degraded, like edge-only preserved images. In addition, the kinoform cannot record an entire object that exceeds the kinoform size because the object light does not widely spread. In order to avoid this degradation and to widely spread the object light, the random phase is applied to the kinoform calculation; however, the reconstructed image is contaminated by speckle noise. In this paper, we overcome this problem by using our random phase-free method and error diffusion method. (C) 2015 Optical Society of America

We report acceleration of color computer-generated holograms (CGHs) from three dimensional (3D) scenes that are expressed as RGB and depth (D) images. These images are captured by a depth camera and depth buffer of 3D graphics library. RGB and depth images preserve color and depth information of 3D scene, respectively. Then we can regard them as two-dimensional (2D) section images along the depth direction. In general, convolution-based diffraction such as the angular spectrum method is used in calculating CGHs from the 2D section images. However, it takes enormous amount of time because of multiple diffraction calculations. In this paper, we first describe "band-limited double-step Fresnel diffraction (BL-DSF)" which can accelerate the diffraction calculation than convolution-based diffraction. Next, we describe acceleration of color CGH using color space conversion. Color CGHs are generally calculated on RGB color space; however, we need to perform the same calculations for each color component repeatedly, so that computational cost of color CGH calculation is three times as that of monochrome CGH calculation. Instead, we use YCbCr color space because the 2D section images on YCbCr color space can be down-sampled without deterioration of the image quality. (C) 2014 Elsevier B.V. All rights reserved.

Computer-Generated Holograms (CGHs) can be generated by superimposing zoneplates. A zoneplate is a grating that can concentrate an incident light into a point. Since a zoneplate has a circular symmetry, we reported an algorithm that rapidly generates a zoneplate by drawing concentric circles using computer graphic techniques. However, random memory access was required in the algorithm and resulted in degradation of the computational efficiency. In this study, we propose a fast CGH generation algorithm without random memory access using run-length encoding (RLE) based recurrence relation. As a result, we succeeded in improving the calculation time by 88 %, compared with that of the previous work. (C) 2015 Optical Society of America

In this study, we propose and experimentally demonstrate a volumetric display system based on quantum dots (QDs) embedded in a polymer substrate. Unlike conventional volumetric displays, our system does not require electrical wiring; thus, the heretofore unavoidable issue of occlusion is resolved because irradiation by external light supplies the energy to the light-emitting voxels formed by the QDs. By exploiting the intrinsic attributes of the QDs, the system offers ultrahigh definition and a wide range of colours for volumetric displays. In this paper, we discuss the design, implementation and characterization of the proposed volumetric display's first prototype. We developed an 8 x 8 x 8 display comprising two types of QDs. This display provides multicolour three-type two-dimensional patterns when viewed from different angles. The QD-based volumetric display provides a new way to represent images and could be applied in leisure and advertising industries, among others.

Random phase is frequently used to a hologram calculation in order to widely spread an object light. However, the reconstructed image is contaminated by speckle noise. In this paper, we apply spherical wave instead of random phase to the hologram calculation, and demonstrate image projection with random phase-free amplitude hologram.

We have developed an algorithm to record multiple two-dimensional information patterns in single volumetric display. In this technique, different two-dimensional information pattern is expressed by the observation position of the observer. We showed some application of this technique.

We propose spatiotemporal division electro-holography for high-definition reconstruction of 3-D object composed of huge number object points. Fainaly, we succeed to display a reconstructed high-difinition image and movie of 3-D object consisting of about 900,000 points.