A volumetric display for visual, tactile and audio presentation using acoustic trapping.

Science-fiction movies portray volumetric systems that provide not only visual but also tactile and audible three-dimensional (3D) content. Displays based on swept-volume surfaces, holography, optophoretics, plasmonics or lenticular lenslets can create 3D visual content without the need for glasses or additional instrumentation. However, they are slow, have limited persistence-of-vision capabilities and, most importantly, rely on operating principles that cannot produce tactile and auditive content as well.

Development of copper recovery process from flotation tailings by a combined method of high‒pressure leaching‒solvent extraction.

Sulfide copper mineral, typically Chalcopyrite (CuFeS), is one of the most common minerals for producing metallic copper via the pyrometallurgical process. Generally, flotation tailings are produced as a byproduct of flotation and still consist of un‒recovered copper. In addition, it is expected that more tailings will be produced in the coming years due to the increased exploration of low‒grade copper ores.

Digital holographic high-speed 3D imaging for the vibrometry of fast-occurring phenomena.

Digital holography allows production of high-speed three-dimensional images at rates over 100,000 frames per second; however, simultaneously obtaining suitable performance and levels of accuracy using digital holography is difficult. This problem prevents high-speed three-dimensional imaging from being used for vibrometry. In this paper, we propose and test a digital holography method that can produce vibration measurements.

Speeding up image quality improvement in random phase-free holograms using ringing artifact characteristics.

A holographic projector utilizes holography techniques. However, there are several barriers to realizing holographic projections. One is deterioration of hologram image quality caused by speckle noise and ringing artifacts.

Autoencoder-based holographic image restoration.

We propose a holographic image restoration method using an autoencoder, which is an artificial neural network. Because holographic reconstructed images are often contaminated by direct light, conjugate light, and speckle noise, the discrimination of reconstructed images may be difficult. In this paper, we demonstrate the restoration of reconstructed images from holograms that record page data in holographic memory and quick response codes by using the proposed method.

In-line digital holographic microscopy using a consumer scanner.

We demonstrate an in-line digital holographic microscopy using a consumer scanner. The consumer scanner can scan an image with 4,800 dpi. The pixel pitch is approximately 5.

Three-dimensional volume containing multiple two-dimensional information patterns.

We have developed an algorithm for recording multiple gradated two-dimensional projection patterns in a single three-dimensional object. When a single pattern is observed, information from the other patterns can be treated as background noise. The proposed algorithm has two important features: the number of patterns that can be recorded is theoretically infinite and no meaningful information can be seen outside of the projection directions.

Band-limited double-step Fresnel diffraction and its application to computer-generated holograms.

Double-step Fresnel diffraction (DSF) is an efficient diffraction calculation in terms of the amount of usage memory and calculation time. This paper describes band-limited DSF, which will be useful for large computer-generated holograms (CGHs) and gigapixel digital holography, mitigating the aliasing noise of the DSF. As the application, we demonstrate a CGH generation with nearly 8K × 4K pixels from texture and depth maps of a three-dimensional scene captured by a depth camera.

Fast calculation of computer-generated hologram using the circular symmetry of zone plates.

Computer-Generated Holograms (CGHs) can be generated from three-dimensional objects composed of point light sources by overlapping zone plates. A zone plate is a grating that can focus an incident wave and it has circular symmetry shape. In this study, we propose a fast CGH generating algorithm using the circular symmetry of zone plates and computer graphics techniques.

Fast high-resolution computer-generated hologram computation using multiple graphics processing unit cluster system.

To overcome the computational complexity of a computer-generated hologram (CGH), we implement an optimized CGH computation in our multi-graphics processing unit cluster system. Our system can calculate a CGH of 6,400×3,072 pixels from a three-dimensional (3D) object composed of 2,048 points in 55 ms. Furthermore, in the case of a 3D object composed of 4096 points, our system is 553 times faster than a conventional central processing unit (using eight threads).

Scaled angular spectrum method.

The angular spectrum method (ASM) calculates diffraction calculation in a high numerical aperture, unlike Fresnel diffraction. However, this method does not allow us to calculate at different sampling rates on source and destination planes. In this Letter, we propose a scaled ASM that calculates diffraction at different sampling rates on source and destination planes using the nonuniform fast Fourier transform.

Arbitrary shape surface Fresnel diffraction.

Fresnel diffraction calculation on an arbitrary shape surface is proposed. This method is capable of calculating Fresnel diffraction from a source surface with an arbitrary shape to a planar destination surface. Although such calculation can be readily calculated by the direct integral of a diffraction calculation, the calculation cost is proportional to O(N²) in one dimensional or O(N⁴) in two dimensional cases, where N is the number of sampling points.

Generation of real-time large computer generated hologram using wavefront recording method.

We report the generation of a real-time large computer generated hologram (CGH) using the wavefront recording plane (WRP) method with the aid of a graphics processing unit (GPU). The WRP method consists of two steps: the first step calculates a complex amplitude on a WRP that is placed between a 3D object and a CGH, from a three-dimensional (3D) object. The second step obtains a CGH by calculating diffraction from the WRP to the CGH.

Time-division color electroholography using one-chip RGB LED and synchronizing controller.

We propose time-division based color electroholography with a one-chip RGB Light Emitting Diode (LED) and a low-priced synchronizing controller. In electroholography, although color reconstruction methods via time-division have already been proposed, the methods require an LCD with a high refresh rate and output signals from the LCD for synchronizing the RGB reference lights such as laser sources, which consequently increase the development cost. Instead of using such an LCD, the proposed method is capable of using a general LCD panel with a normal refresh rate of 60 Hz.

Numerical study of color holographic projection using space-division method.

We propose a color holographic projection using the space-division method, which can reconstruct a two-dimensional color image by one hologram and avoid the superimposing of unwanted images on a wanted image. We calculated three holograms corresponding to red, green and blue, and then generated one hologram to add the three holograms. The three holograms were optimized by the Gerchberg-Saxton algorithm for improvement of reconstructed color images.

Rapid calculation algorithm of Fresnel computer-generated-hologram using look-up table and wavefront-recording plane methods for three-dimensional display.

A rapid calculation method of Fresnel computer-generated-hologram (CGH) using look-up table and wavefront-recording plane (WRP) methods toward three-dimensional (3D) display is presented. The method consists of two steps: the first step is the calculation of a WRP that is placed between a 3D object and a CGH. In the second step, we obtain an amplitude-type or phase-type CGH to execute diffraction calculation from the WRP to the CGH.

Fast calculation of computer-generated-hologram on AMD HD5000 series GPU and OpenCL.

In this paper, we report fast calculation of a computer-generated-hologram using a new architecture of the HD5000 series GPU (RV870) made by AMD and its new software development environment, OpenCL. Using a RV870 GPU and OpenCL, we can calculate 1,920 x 1,024 resolution of a CGH from a 3D object consisting of 1,024 points in 30 milli-seconds. The calculation speed realizes a speed approximately two times faster than that of a GPU made by NVIDIA.

Quantitative assessment method for computer-generated holograms free from the effect of viewpoint.

A quantitative assessment method for computer-generated holograms is presented. Our scheme is based on a simple evaluation quantity reflecting the optical radiating power from the holograms; this assures the overall validity of our method as a three-dimensional (3D) display assessment technique. Moreover, the effect of location from which the 3D view is observed is ruled out from the result.

One-unit system to reconstruct a 3-D movie at a video-rate via electroholography.

We have developed a one-unit system, including creating and displaying a hologram for real-time reproduction of a three-dimensional image via electroholography. We have constructed this one-unit system by connecting a special-purpose computer for holography and a special display board with a reflective liquid crystal display as a spatial light modulator. Using this one-unit system, we succeeded in reproducing a three-dimensional image composed of 10,000 points at a speed of 30 frames per second, which is the video rate in NTSC format.

Simple and fast calculation algorithm for computer-generated hologram with wavefront recording plane.

We present a simple and fast calculation algorithm for a computer-generated hologram (CGH) by use of wavefront recording plane. The wavefront recording plane is placed between the object data and a CGH. When the wavefront recording plane is placed close to the object, the object light passes through a small region on the wave recording plane.

Simplified electroholographic color reconstruction system using graphics processing unit and liquid crystal display projector.

We have constructed a simple color electroholography system that has excellent cost performance. It uses a graphics processing unit (GPU) and a liquid crystal display (LCD) projector. The structure of the GPU is suitable for calculating computer-generated holograms (CGHs).

HORN-6 special-purpose clustered computing system for electroholography.

We developed the HORN-6 special-purpose computer for holography. We designed and constructed the HORN-6 board to handle an object image composed of one million points and constructed a cluster system composed of 16 HORN-6 boards. Using this HORN-6 cluster system, we succeeded in creating a computer-generated hologram of a three-dimensional image composed of 1,000,000 points at a rate of 1 frame per second, and a computer-generated hologram of an image composed of 100,000 points at a rate of 10 frames per second, which is near video rate, when the size of a computer-generated hologram is 1,920 x 1,080.

Special purpose computer system for flow visualization using holography technology.

We have designed a special purpose computer system for visualizing fluid flow using digital holographic particle tracking velocimetry (DHPTV). This computer contains an Field Programmble Gate Array (FPGA) chip in which a pipeline for calculating the intensity of an object from a hologram by fast Fourier transform is installed. This system can produce 100 reconstructed images from a 1024 x 1024-grid hologram in 3.

Computer generated holography using a graphics processing unit.

We have applied the graphics processing unit (GPU) to computer generated holograms (CGH) to overcome the high computational cost of CGH and have compared the speed of a GPU implementation to a standard CPU implementation. The calculation speed of a GPU (GeForce 6600, nVIDIA) was found to be about 47 times faster than that of a personal computer with a Pentium 4 processor. Our system can realize real-time reconstruction of a 64-point 3-D object at video rate using a liquid-crystal display of resolution 800x600.

Special purpose computer for digital holographic particle tracking velocimetry.

We have designed a special purpose computer system for digital holographic particle tracking velocimetry (DHPTV). We present the pipeline for calculating the intensity of an object from a hologram by fast Fourier transform in an FPGA chip. This system uses four FPGA chips and can make 100 reconstructed images from a 256x256-grid hologram in 266 msec.