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Current display approaches, such as VR, allow us to get a glimpse of multimodal 3D experiences, but users need to wear headsets as well as other devices in order to trick our brains into believing that the content we are seeing, hearing or feeling is real. Light-field, holographic or volumetric displays avoid the use of headsets, but they constraint the user’s ability to interact with them (e.g. content is not reachable to user’s hands, user’s constrained to specific locations) and, most importantly, still cannot simultaneously deliver sound and touch. In this talk, we will present the Multimodal Acoustic Trapping Display (MATD): a mid-air volumetric display that can simultaneously deliver visual, tactile and audio content, using phased arrays of ultrasound transducers. The MATD makes use of ultrasound to trap, quickly move and colour a small particle in mid-air, to create coloured volumetric shapes visible to our naked eyes. Making use of the pressure delivered by the ultrasound waves, the MATD can also create points of high pressure that our bare hands can feel and induce air vibrations that create audible sound. The system demonstrates particle speeds of up to 8.75 m/s and 3.75 m/s in the vertical and horizontal directions, respectively. In addition, our technique offers opportunities for non-contact, highspeed manipulation of matter, with applications in computational fabrication and biomedicine.

Sulfide copper mineral, typically Chalcopyrite (CuFeS2), 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. Therefore, this research aims to develop a copper recovery process from flotation tailings using high‒pressure leaching (HPL) followed by solvent extraction. Over 94.4% copper was dissolved from the sample (CuFeS2 as main copper mineral) by HPL in a H2O media in the presence of pyrite, whereas the iron was co‒dissolved with copper according to an equation given as CCu = 38.40 × CFe. To avoid co‒dissolved iron giving a negative effect on the subsequent process of electrowinning, solvent extraction was conducted on the pregnant leach solution for improving copper concentration. The result showed that 91.3% copper was recovered in a stripped solution and 98.6% iron was removed under the optimal extraction conditions. As a result, 86.2% of copper was recovered from the concentrate of flotation tailings by a proposed HPL‒solvent extraction process.

[Abstract] Holography is a leading method of recording and reproducing 3D images. The increasingly widespread availability of computers has encouraged the development of holographic 3D screens (electroholography). Although electroholography was first proposed a half-century ago, it has not been used in practical applications. A fundamental problem is the enormous volume of data that a hologram requires. Even modern computational power is inadequate to process this volume of data in real time. The area from which the reconstructed image can be viewed is determined by the way in which the light diffracted by the hologram is spread, and this in turn depends on the pixel pitch of the hologram. A smaller pitch creates a wider viewing angle. At a pixel pitch of 1 μm, the viewing angle extends to 30°, thus making it practical for everyday applications. The pixel pitch of a typical current liquid crystal display is approaching this limit. However, a high-definition display device requires a large number of pixels, thus making processing challenging. At a 1 μm pixel pitch, even a display device that is 1 cm × 1 cm in size would require 100 million (108) pixels. Our group has been pursuing a five-year project with the goal of realising an arithmetic circuit that is able to drive a video-rate 1 cm × 1 cm computer-generated hologram of 108 pixels at a pixel pitch of 1 μm. In the course of this research, we have developed a special-purpose holography computing board by using eight large-scale field-programmable gate arrays (FPGAs). This computing board is far beyond the scope of current commercial offerings. We have also succeeded in achieving a parallel operation of 4,480 hologram calculation circuits on a single board. By clustering eight of these boards, we succeeded in increasing the number of parallel calculations to 35,840, thus allowing computations to be performed 1,000 times faster than those of a personal computer. By using a 3D image comprising 7,877 points, we succeeded in updating 108-pixel holograms at a video rate, thus allowing 3D movies to be projected. We further demonstrated that the system speed scales up in a linear manner as the number of parallel circuits is increased. The system operates at 0.25 GHz with an effective speed equivalent to 0.5 Pflops (1015 floating-point operations per second), matching that of a high-performance computer. These results suggest that a holographic 3D image system can be constructed using currently available technology. In a further step, we will upgrade the system to a large-scale integration (LSI) circuit that is 1 cm × 1 cm in size by using existing technology. Coupling this LSI to a 108-pixel display would create a chip dedicated to holography. Given that the computation of a hologram treats each pixel independently, a suitable arrangement of these dedicated chips could create a 3D video system of arbitrary size and shape (hemispherical, spherical, cylindrical, etc.). As one of immediate goals, we can create a wide 3D projection space by incorporating our dedicated chip into a head-mounted display.

Blue-phase liquid crystals form three-dimensional structures in a self-organizing manner and are similar to living tissue structures such as the teeth of mice and collagen tissues. This stu...

Fast hologram calculation methods are critical in real-time holography applications such as three-dimensional (3D) displays. We recently proposed a wavelet transform-based hologram calculation called WASABI. Even though WASABI can decrease the calculation time of a hologram from a point cloud, it increases the calculation time with increasing propagation distance. We also proposed a wavefront recoding plane (WRP) method. This is a two-step fast hologram calculation in which the first step calculates the superposition of light waves emitted from a point cloud in a virtual plane, and the second step performs a diffraction calculation from the virtual plane to the hologram plane. A drawback of the WRP method is in the first step when the point cloud has a large number of object points and/or a long distribution in the depth direction. In this paper, we propose a method combining WASABI and the WRP method in which the drawbacks of each can be complementarily solved. Using a consumer CPU, the proposed method succeeded in performing a hologram calculation with 2048 × 2048 pixels from a 3D object with one million points in approximately 0.4 s.

Acid mine drainage (AMD) waters are one of the most important ecological risks at the global level because of its high heavy metals content and strong acidity. Treatment of AMD water is a complex and expensive. One of the most widely used treatment process is the neutralization process of AMD. The result of neutralization is the production of sludge which may contain various other (heavy) metals, depending on the chemical characteristics of the mine water treated. In this paper, leachability and toxicity of the sludges obtained during the neutralization process of wastewater from Saraka and Robule acid mine drainage and the sludges after the stabilization process at different temperatures is tested. Sludge produced in the neutralization process of Robule AMD R4 (40) and stabilized on 105°C and 200°C shows a H8-corrosiveness characteristic. Stabilized sludge show tendency to lower leachability of zinc and copper, but without influence on sulphate leachability. Sludges that show a H8-corrosiveness needs additional stabilization/neutralization pretreatment prior temperature treatment.

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 surfaces1,2, holography3, optophoretics4, plasmonics5 or lenticular lenslets6 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. Here we present the multimodal acoustic trap display (MATD): a levitating volumetric display that can simultaneously deliver visual, auditory and tactile content, using acoustophoresis as the single operating principle. Our system traps a particle acoustically and illuminates it with red, green and blue light to control its colour as it quickly scans the display volume. Using time multiplexing with a secondary trap, amplitude modulation and phase minimization, the MATD delivers simultaneous auditive and tactile content. The system demonstrates particle speeds of up to 8.75 metres per second and 3.75 metres per second in the vertical and horizontal directions, respectively, offering particle manipulation capabilities superior to those of other optical or acoustic approaches demonstrated until now. In addition, our technique offers opportunities for non-contact, high-speed manipulation of matter, with applications in computational fabrication7 and biomedicine8. A volumetric display that can simultaneously deliver visual, tactile and auditory content is demonstrated.

Electroholography can produce natural 3D scenes and has gained recognition as an ideal 3D technology. However, insufficient computational power has made it difficult to achieve real-time electroholography. In this paper, we developed a compact special-purpose system for calculating phase-only holograms. We implemented the developed system using a system on a chip embedded with a processor and logic circuit blocks. Our system successfully computed holograms of 1,920×1,080 pixels from a point-cloud with 32,500 points at 10 frames per second. The system is 147 times faster than a personal computer (with 6 CPU cores).

The possibility of metal removal from the real acid mine drainage (AMD) in the area of copper ore mines in the southeast Serbia, was investigated through a combination of neutralization and adsorption methods. This approach of metal removal from AMD includes a two-step neutralization method in the first phase, aiming to separate metals as sludge. The results of laboratory test revealed that more than 99 mass % of Fe is removed up to pH 4 and more than 99 mass % of Cu up to pH 7. Based on the results obtained in laboratory conditions, a test on a semi industrial plant was carried out. The two-step neutralization separately removed Fe and Cu at pH 4 and 7, respectively. Especially, the obtained sludge at pH 7 included 1.24 mass % of Cu, much higher than usual Cu ore. Chitosan was applied for dissolved Mn removal from treated AMD. After 24 h incubation, 70 mass % of Mn is removed from the treated AMD at pH 7.4. Mn concentration was reduced from approx. 35 mg L&minus, 1 to 5 mg L&minus, 1. These results have indicated that a combination of neutralization and adsorption methods could be used effectively for metal removal from real AMD.

Digital holography is attracting attention because it can record instantaneous three-dimensional (3D) information and record dynamic phenomena. However, when recording high-speed phenomena, the frame rate ranges from tens of thousands to hundreds of millions, and the calculation time of the reconstructed images is a problem. We have developed a special-purpose computer for high-speed 3D imaging using digital holography. The developed special-purpose computer has four calculation modules and has achieved a calculation time 68 times faster than that of a personal computer with 48 cores. With the developed computer, a total of 32 reconstructed images can be calculated in 0.69 ms from four holograms of 128 × 128 pixels with eight varying depths.

The aim of this research was to develop a copper recovery process from mine tailings (0.34%Cu) using flotation followed by high-pressure oxidative leaching (HPOL) and solvent extraction. The results of HPOL using the concentrate of mine tailings obtained by flotation under the optimal conditions of the previous study shown that an efficient copper dissolution of 94.4% was achieved in an H2O media, while the copper concentration of PLS reached to be 2.9 g/L. The solvent extraction of PLS obtained from the optimal HPOL showed that 91.3% copper was recovered in stripped solution under the determined optimum conditions, in which the copper concentration achieved to be 44.8 g/L. Finally, a proposed copper recovery process from the concentrate of mine tailings was developed by combination of HPOL and solvent extraction, while a total copper recovery of 86% was achieved.

金沢大学理工研究域機械工学系, 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. The method is based on single-shot phase-shifting interferometry. Herein, we imaged the surface of a loudspeaker diaphragm and measured its displacement due to the vibrations produced by a frequency sweep signal. We then analyzed the frequency of the experimental data and confirmed that the frequency spectra inferred from the reconstructed images agreed well with the spectra produced by the sound recorded by a microphone. This method can be used for measuring vibrations with three-dimensional imaging for loudspeakers, microelectromechanical systems, surface acoustic wave filters, and biological tissues and organs. © 2017 The Author(s).

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.

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. The combination of the random phase-free method and the Gerchberg-Saxton (GS) algorithm has improved the image quality of holograms. However, the GS algorithm requires significant computation time. We propose faster methods for image quality improvement of random phase-free holograms using the characteristics of ringing artifacts.

Electroholography is attracting attention as an ideal 3D image presentation method. Developing such methods involves significant computational complexity; thus, they are difficult to realize. Typically, large cluster systems with a control PC and a field-programmable gate array (FPGA) acceleration board are used to reduce hologram calculation time. However such systems cannot be used for embedded 3D systems, such as a head-mounted display. In this study, we developed a compact holographic computer using a Xilinx Zynq UltraScale+ MPSoC with an ARM CPU and an FPGA on a single chip. The proposed system can reproduce a 3D video at 15 frames per second for a spatial light modulator of 1,920 $\times$× 1,080 pixels from an object represented by 6,500 point cloud sources. The proposed system can be embedded in various systems, e.g., head-mounted displays and 3D televisions.

Holographic projection is for laser displays and has the merits of being aberration free, producing high-contrast images, having the ability of color reconstruction with one spatial light modulator, and so on. In this paper, we propose a zoomable holographic projection without using a zoom lens and verify the proposed method by using numerical simulation. Although such a system can be readily realized to use the features of holography, which is capable of recording a large image exceeding the hologram size, the required calculation is very time consuming. For acceleration, we used shifted Fresnel diffraction for setting different sampling rates on a hologram and projected image. The proposed method can project any zoom-in and zoom-out image between zeroth-order and first-order lights, and the processing time and required memory for the zoom are constant.

In this paper, we derive a fast recurrence relation for a computer-generated-hologram (CGH). The recurrence relation based on Taylor expansion reduces the number of cosine computations as compared with conventional CGH formula. The recurrence relation calculates a CGH 7 or 8 times faster than the conventional CGH formula on a CPU and graphics processing unit (GPU). In addition, there is almost no difference between a CGH generated by the recurrence relation and that generated by the conventional type.

Particle Image Velocimetry (PIV) is a method of obtaining velocity field. A HORN-5 is a special-purpose computer had 4 FPGAs. We designed a circuit for PIV with an 8 × 8 two-dimensional 2-radix FFT in a FPGA on the HORN-5 and compared its calculation speed with that of a PC by using a C++ code. As a result, the calculation speed of the FPGA was found to be 8.93 times faster than that of the PC. Moreover, the system was adopted for reading artificial PIV standard images and real experimental images. On the numerical accuracy, the velocity vectors of both results were also found to be in good agreement with that of the PC by FORTRAN code.

There are two types of hologram, an amplitude modulation and a phase modulation ones. Recently, not only amplitude modulation ones but also phase modulation ones have been used in liquid crystal displays. We constructed an electro-holography system with a phase modulation type liquid crystal display and compared it to a system using current amplitude electro-holography. In the amplitude hologram, the reconstructed image darkens because the contrast of the hologram is low when the gray level is increased. It lightens most when binary. However, the phase hologram with high diffraction efficiency has produced an excellent result. The reconstructed image is bright even if the gray level is increased, and all the information of the liquid crystal display can be used at 256 gray levels.

We have designed a PC cluster system with special purpose computer boards for visualization of fluid flow using digital holographic particle tracking velocimetry (DHPTV). In this board, there is a Field Programmable Gate Array (FPGA) chip in which is installed a pipeline for calculating the intensity of an object from a hologram by fast Fourier transform (FFT). This cluster system can create 1024 reconstructed images from a 1024 × 1024 -grid hologram in 0.77 s. It is expected that this system will contribute to the analysis of fluid flow using DHPTV.

We have sped up the calculation of a computer-generated hologram by parallel computing using ClearSpeed Advance TM Dual CSX600 PCI-X Accelerator Board by ClearSpeed Technology plc. By using two boards in parallel, our system was able to perform the calculation 50 times as fast as a personal computer.

Using a system of combined PC and LSI is useful when a research environment does not allow using supercomputers and calculation objects are restricted. FPGA is different from ASIC. A circuit in FPGA can be designed and reconfigured with PC or workstation electrically. We designed and implemented a circuit for 8×8 two-dimensional 2-radix FFT in a FPGA and compared its calculation speed with that of a PC. As a result, the calculation speed of the FPGA was found to be 1.3 times faster than that of a PC.

In this paper, we report an interactive color electroholography system using the field-programmable gate array (FPGA) technology and the time division switching method for color reconstruction. We implemented 30 dedicated-processors for a computer-generated hologram (CGH) into an FPGA chip, and the FPGA chip can generate full-parallax CGHs, on which we record color information for a color 3D object, faster than a personal computer. The time division switching method can reconstruct a color 3D object from the CGHs, to make use of the afterimage effect on human eyes. The system allows us to perform interactive operations for a reconstructed color 3D object using a keyboard, while viewing the reconstructed color 3D object.

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 3.3 sec. It is expected that this system will contribute to fluid flow analysis.

In this paper, we report an electroholographic reconstruction method for a colour three-dimensional (3D) object, using the time division switching of reference lights. We use a reflective liquid crystal display (LCD) panel with a high refresh rate as a spatial light modulator. A colour 3D object is divided into red, green and blue components, from which we compute three computer-generated holograms (CGHs). The LCD panel displays the CGHs in sequence at a refresh rate of about 100 Hz. The LCD panel also outputs synchronized signals, indicating that one of the CGHs is currently displayed on the LCD panel. Red, green and blue light emitting diodes (LEDs), as used for reference lights, are switched by the synchronized signals. As a result of the afterimage effect on human eyes, we can clearly observe a coloured 3D object.

We developed a simple electroholography system consisting of a graphics processing unit(GPU),which has been developing quickly in recent years,and a PC projector,which contains a minute reflective liquid crystal display(LCD).The structure of the GPU is suitable for calculating a computer-generated hologram(CGH).The calculation speed of the GPU is approximately 500 times faster than that of a central processing unit(CPU) alone.We succeeded in reproducing a video of an object,which consisted of 256 points in about 20 frames/s.Reconstruction at the video rate(real time) was almost completely achieved.Moreover,we used a PC projector in which minute reflective LCD panels were included as part of the reconstruction optical system.Three LCD panels for the three RGB colors were built into the inside of a projector.Using them,holographic reconstruction with color was also able to be performed easily.This system,consisting of a GPU and a projector,is simple to make.Therefore,this system is expected to promote reserch in this field.

We have developed a special-purpose computer for analyzing X-ray scattering of models of macromolecules, named XSAM-2 (solution X-ray Scattering Analysis of Macromolecules). XSAM-2 contains 64 circuits operating in parallel for calculating X-ray scattering intensities using the pipeline method. XSAM-2 calculates 122 times faster than a personal computer with a Pentium 4 processor.