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Background To provide updates on clinical practice of acute pancreatitis (AP) in Japan, we conducted a nationwide epidemiological survey. Methods This study consisted of a two-staged survey; the number of AP patients was estimated by the first-stage survey and their clinical features were examined by the second-stage survey. We surveyed AP patients who had visited hospitals in 2016. Results The estimated number of AP patients in 2016 was 78,450, with an overall incidence of 61.8 per 100,000 persons. We obtained detailed clinical information of 2994 AP patients, including 706 (23.6%) severe cases classified according to the Japanese severity criteria. The male-to-female sex ratio was 2.0, and the mean age at onset was 59.9 years in males and 66.5 years in females. Alcohol was the most common etiology (42.8%) in males and gallstones in females (37.7%). The AP-associated mortality was 6.1% in severe AP cases, which was decreased by 40% compared to the 2011 survey. Antibiotics were administered to most cases, with carbapenem being frequently used. Enteral nutrition was given in 31.8% of severe cases, but majority cases received after 48 h. Among the 107 patients who received intervention for walled-off necrosis, five patients received surgery-first approach, 66 received endoscopic ultrasound-guided transluminal drainage, and 19 underwent step-up approach. Conclusions We clarified the current status of AP in Japan including the significant reduction of mortality in severe cases, shift to endoscopic approaches for walled-off necrosis, and poor compliance of the recommendations in the guidelines including management of enteral nutrition and antibiotic administration.

We assessed the image quality in holographic near-eye displays by faithfully simulating coherent image formation on the retinal plane and comparing the simulated results with those of incoherent imaging.

Optical phased arrays (OPAs), which manipulate an optical beam by controlling the phase of light, are optical devices characterized by high speed, small size, light weight, and high reliability that make various applications possible. In this study, an eight-channel-waveguide OPA using an electro-optic (EO) polymer for phase control was fabricated. Very high-speed optical beam scanning with a frequency of 2 MHz was demonstrated by applying a driving waveform superimposing sinusoidal and rectangular-wave voltages. Furthermore, the EO polymer OPA can be operated with a low total-operation power consumption of 0.38 mW at a scanning speed of 500 kHz.

We have been investigating an optical phased array (OPA) using an electro-optic (EO) polymer, that can control the shape and direction of an optical beam at high speed. In this study, we propose an OPA which consists of hybrid waveguides with organic and inorganic optical core materials. By applying the taper structure to the inorganic core at the connection part, we inproved coupling efficiency.

An integral 3-D technique provides a 3-D spatial image viewable from varying positions without the use of special light sources or viewing glasses. Therefore, this technique shows promise for diverse applications in various fields, including 3-D television broadcasting, advertising, and medical diagnostics. However, there are problems in capturing and displaying large amounts of information in realizing practical integral imaging devices. This paper overviews integral 3-D capturing methods and analyzes integral 3-D imaging technology at its capturing and displaying stages. To overcome the resolution problem, it also introduces our recent work for capturing high-resolution integral imaging information. The introduced device consists of a multiple-lens array and a complementary metal–oxide–semiconductor image sensor with a circuit patterned using multiple exposures. This device can capture depth-controlled spatial information by introducing additional optics. Two types of optics for depth control are applied to the capturing device: one functions as a convex lens to control and compress a relatively large object space and the other functions as an afocal lens array that controls a relatively small object space without any distortion in the depthwise direction. Experimental results of spatial information capturing and 3-D image displays confirm that the method produces 3-D images having an appropriate motion parallax. The presented method is scalable; thus, this technique offers possibilities for developing advanced high-resolution integral 3-D imaging devices.

We present a phase compensation method for an optical phased array (OPA) to manipulate a sharply defined optical beam. Undesirable initial phase distribution caused by non-uniformity of fabrication processes and variation in the characteristics of phase shifters is measured by utilizing phase-shifting digital holography, where a light wave from a waveguide in arrayed waveguides is used as a reference wave and light waves from the other waveguides are used as object waves. The initial phases can be compensated by using the measured result without falling into local optimal solutions. A numerical simulation showed that the initial phases were correctly measured and compensated by using the proposed method. Applications of the proposed compensation method to a fabricated OPA with 16-channel electro-optic polymer waveguides results in obtaining a sharply defined optical beam.

We have been developing a magneto-optical (MO) spatial light modulator (SLM) with a narrow pixel pitch which enables reproducing holographic three-dimensional (3D) images with wide-viewing angle. In this study, we investigated a light modulation performance for reproducing holographic 3D image of an MO light modulation device array. The light modulation device array can easily realize a magnetic interference fringe pattern by applying an external magnetic field without a transistor (i.e. without fabricating the real MO-SLM). The pattern, however, is not rewritable. The array was designed with a pitch of 1 × 2 μm. When a reproducing illumination light was incident to the device, a holographic 3D image with wide-viewing angle of 36° in the horizontal direction and 18° in the vertical direction was reproduced. A clear holographic image was observed through an analyzer because the phase of the unnecessary diffracted light, generated by the pixel structure, shifts by 90° from that of the magnetically diffracted component by the MO effect. If the light modulation device array is fabricated on the transistor backplane, any magnetization pattern can be realized by injecting a current. The MO-SLM was shown as an effective device for realizing a holographic display with a wide-viewing angle.

We fabricated a high-density, large-scale magneto-optical (MO) light modulator array to investigate its performance for holographic display applications. The modulator comprised a magnetic nanowire for light modulation using MO Kerr effect and two hard magnets (HMs) to control the switching property of the nanowire. The magnetization direction of the designated pixels in the array was controlled by the external magnetic field, unlike a spatial light modulator, which drives arbitrary pixels with cell selection backplane transistors. Magnetization of the light modulators with HMs can be reversed using a smaller magnetic field compared with those without HMs; this enables the formation of magnetic patterns by switching only the magnetization direction of the nanowire with smaller switching field; the pattern thus obtained is predetermined and not arbitrary. A diffracted beam in a magnetic stripe pattern displayed on the array was observed as spot patterns, and their spot position was consistent with a diffraction angle of the stripe period. We fabricated a magnetic hologram using a 10 k × 10 k pixel array calculated by computer-generated holography and successfully reproduced a holographic three-dimensional image with a wide viewing angle.

We present a method to display an integral three-dimensional (3D) image without gaps between multiple display active areas by using multiple liquid crystal display (LCD) panels and multi-image combining optical systems (MICOS). We designed a MICOS to improve the resolution characteristics and decrease the luminance unevenness corresponding to the viewpoint. Furthermore, we developed a method for correcting the distortion of the integral 3D image by using image processing. We prototyped an integral 3D display using four 8K dual-green (8KDG) LCD panels and the improved MICOSs. The prototype display achieved to magnify the display area about 5.66 times more than when a single LCD panel was used.

In integral photography (IP), it is difficult to obtain three-dimensional photographs with high spatial resolution, high angular resolution, and a wide viewing angle simultaneously. Thus, we proposed a dense parallax image acquisition method using single-pixel imaging. We confirmed that parallax images can be obtained depending on the position of the photodetector. By replacing the detector to each pixel of an image sensor, a two-dimensional image with different parallaxes in each pixel can be acquired. We demonstrated the reconstruction of dense parallax images according to the pixel position of the image sensor. This method is effective in addressing the trade-off among spatial resolution, angular resolution, and a viewing angle. It can also improve the image quality in IP.

In reflection-type holographic memory, speckle-shift multiple recording along the axial direction of a storage medium is investigated experimentally and numerically. We record three data pages along the axial direction of an iron-doped lithium niobate medium with a thickness of 0.5 mm and an interval of the first null distance of shift selectivity, and each hologram was read out at the recording position. We also numerically evaluate the multiple recording along the axial direction. The numerical analysis supports the fact that the speckle size determines the three-dimensional recording interval. The numerical results are in qualitative agreement with the experimental results. We numerically examine the bit error rate as a function of the recording interval. The results show that multiplexing along the axial direction can increase the storage capacity.

A compact integral three-dimensional (3D) imaging device for capturing high resolution 3D images has been developed that positions the lens array and image sensor close together. Unlike the conventional scheme, where a camera lens is used to project the elemental images generated by the lens array onto the image sensor, the developed device combines the lens array and image sensor into one unit and makes no use of a camera lens. In order to capture high resolution 3D images, a high resolution imaging sensor and a lens array composed of many elemental lenses are required, and in an experimental setup, a CMOS image sensor circuit patterned with multiple exposures and a multiple lens array were used. Two types of optics were implemented for controlling the depth of 3D images. The first type was a convex lens that is suitable for compressing a relatively large object space, and the second was an afocal lens array that is suitable for capturing a relatively small object space without depth distortion. The objects captured with the imaging device and depth control optics were reconstructed as 3D images by using display equipment consisting of a liquid crystal panel and a lens array. The reconstructed images were found to have appropriate motion parallax.

A method to detect minute flaws on metal parts is proposed to remove the defective parts before assembling in a factory. The input gray-scale images of metal parts are used directly to recognize flaws without any image conversion to shorten recognition time. The recognition problem to find flaws and detect their positions on the metal parts is converted here to another problem to search for maximum peak and the variables giving the peak. Then the recognition problem can be treated as an optimization problem, and this conversion allows us to utilize the high performances of Genetic Algorithms in the optimization. The recognition rate of the proposed system was improved by changing the lighting condition so as to emphasize the contrast between the metal surface and the bruise using the reflection character of the hairline on the metal resulted by polishing process. The effectiveness and problems of proposed method are analyzed on standing points of recognition speed and quantitative recognition ability.

We have developed a compact integral three-dimensional (3D) imaging equipment that positions the lens array and image sensor in close proximity to each other. In the conventional scheme, a camera lens is used to project the elemental images generated by the lens array onto the image sensor. In contrast, the imaging equipment presented here combines the lens array and image sensor into one unit and makes no use of a camera lens. This scheme eliminates the resolution deterioration and distortion caused by the use of a camera lens and improves, in principle, the quality of the reconstructed 3D image. We captured objects with this imaging equipment and displayed the reconstructed 3D images using display equipment consisting of a liquid crystal panel and a lens array. The reconstructed 3D images were found to have appropriate motion parallax.

A presence of a strong external magnetic field can affect a flow distribution of a liquid-metal (LM) coolant in a fusion blanket, due to magnetohydrodynamic (MHD) effects. LM blankets have some manifolds, where the coolant flow from a single supply channel is distributed to multiple parallel channels. Since these manifolds have complex geometries, an interaction between induced axial electric currents and the magnetic field reorganizes the flow to be three-dimensional. A flow imbalance in such a complicated manifold affects heat removal performances, which is closely related to the blanket feasibility and safety. This study was performed to experimentally and numerically investigate a LM distribution in MHD flows in an electrically insulating manifold with changing the intensity and orientation of the magnetic field transverse to the flows. The flow passage employed in this study is a U-turn manifold consisting of an upward rectangular duct, a U-turn branching area, and two downward ducts with insulating walls. The gallium-indium-tin eutectic alloy (GaInSn) was employed as a working fluid. The present study shows that, as the magnetic field is applied more perpendicularly with respect to the U-turn, much amount of the fluid flows in the inner downward channel than that in the outer one.

Integral three-dimensional (3D) television based on integral imaging requires huge amounts of information. Previously, we constructed an Integral 3D television using Super Hi-Vision (SHV) technology, with 7680 pixels horizontally and 4320 pixels vertically. We report on improved image quality through the development of video system with an equivalent of 8000 scan lines for use with Integral 3D television. We conducted experiments to evaluate the resolution of 3D images using an experimental setup and were able to show that by using the pixel-offset method we have eliminated aliasing produced by full-resolution SHV video equipment. We confirmed that the application of the pixel-offset method to integral 3D television is effective in increasing the resolution of reconstructed images.

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.

Japan has about 120 active volcanoes. Estimated potential of geothermal power generation is 23,470 MWe from hydrothermal reservoirs to a depth of 3 km. Geothermal energy is expected to be an important role for zero-carbon era. Currently, 21 electric power units at 18 geothermal sites are in operation with a total capacity of 537 MWe, which amounts to about 2.3% of its potential power. The main reason of such a low utilization rate is mainly due to its high cost and impact on ambient surrounding of power plant. We start to develop a new system of geothermal energy conversion. In order to do its first pilot experiment for the proposed system, case studies are carried out by using the two-fluid model which is well developed in the nuclear reactor field. The two types of extraction of hot water, that is, two-phase flow and single-phase liquid flow, have been examined. According to the results of case studies, the required material properties, dimension of test apparatus, experiment conditions, such as inlet pressure and flow rate, have been cleared.

Integral 3D television based on integral imaging requires huge amounts of information. Earlier, we built an Integral 3D television using Super Hi-Vision (SHV) technology, with 7680 pixels horizontally and 4320 pixels vertically. Here we report on an improvement of image quality by developing a new video system with an equivalent of 8000 scan lines and using this for Integral 3D television. We conducted experiments to evaluate the resolution of 3D images using this prototype equipment and were able to show that by using the pixel-offset method we have eliminated aliasing that was produced by the full-resolution SHV video equipment. As a result, we confirmed that the new prototype is able to generate 3D images with a depth range approximately twice that of Integral 3D television using the full-resolution SHV.

We present a method of changing the ratio of a horizontal to vertical angles by rotating a lens array in integral imaging. We arranged an elemental image with a width and height that is not equal to the pitch of an elemental lens as the total number of the pixels of the elemental image is invariant. Additionally, we rotated the lens array to avoid overlapping the specially-shaped elemental images. We enlarged the horizontal viewing angle by arranging the elemental images with a width that is larger than height and the pitch of the elemental lens. We investigated the arrangement of these images and found that rotating the lens array changed the ratio of the horizontal to vertical viewing angles.

We present a generating method of stereoscopic images from moving pictures captured by a single high-definition television camera mounted on the Japanese lunar orbiter Kaguya (Selenological and Engineering Explorer, SELENE). Since objects in the moving pictures look as if they are moving vertically, vertical disparity is caused by the time offset of the sequence. This vertical disparity is converted into horizontal disparity by rotating the images by 90 degrees. We can create stereoscopic images using the rotated images as the images for a left and right eyes. However, this causes spatial distortion resulting from the axi-asymmetrical positions of the corresponding left and right cameras. We reduced this by adding a depth map that was obtained by assuming that the lunar surface was spherical. We confirmed that we could provide more acceptable views of the Moon by using the correction method.

In this paper, we present the estimation of storage capacity in reflection-type holographic memory by using scalar diffraction theory. Signal to noise ratio in speckle shift multiplexing is derived numerically. The maximum storage capacity is presented by using signal to noise ratio and then a few tera byte is possible in a 5-inch disk.

This paper investigates numerically interpage crosstalk noise in reflection-type holographic memory system by speckle three-dimensional shift multiplexing. The crosstalk noise is one of factors to limit storage capacity. Numerical evaluation showed that constant crosstalk noise was caused by illumination of a readout beam.

Numerical evaluation of storage density in reflection-type holographic memory by shift multiplexing with random phase modulation is presented. Numerical results show that the random phase modulation can improve the shift selectivity in shift multiplexing recording.

A simulation technique for a volume holographic memory system based on binary page data is proposed to evaluate quantitative diffraction efficiency, bit error rate, and signal-to-noise ratio. In this simulator, propagation of a signal and reference beams and diffraction at gratings are calculated quantitatively by use of numerical Fresnel propagation and Kogelnik's coupled-wave theory. To apply Kogelnik's wave theory to arbitrary signal and reference beams, both beams at the hologram plane are decomposed into plane waves. Numerical results show good agreement with the exact solution under the Born approximation in a transmission-type volume hologram. We also apply the simulator to reflection-type holographic memory.

A reflection-type holographic disk memory system with random phase shift multiplexing is proposed. The experimental results show that a binary data page of 18x17 bits is recorded successfully at intervals of 4 mum in a Fe:LiNbO3 crystal with a thickness of 0.5 mm when six data pages are superimposed. Numerical results show that random phase modulation can improve the shift selectivity in shift multiplexing recording as well as in data security. Experimental and numerical results show that reflection-type holographic disk memory has a high potential for terabyte storage capacity as in transmission-type memory.

Maximum storage capacity in a reflection-type holographic memory with three-dimensional speckle shift multiplexing is investigated numerically. An explicit expression of storage capacity is derived on the basis of interpage crosstalk noise. We fabricate a simulator to evaluate reflection-type holographic data storage by calculating wave propagation, recording a hologram, and reconstruction by scalar diffraction. We calculate the properties of the resultant diffraction efficiency, that is the noise, at the first null in the speckle-shift multiplexing. Numerical results indicate that the storage capacity is proportional to the numerical aperture to the fourth power and to the volume of the recording medium and is inversely proportional to the wavelength to the third power. Achievable storage capacity is discussed.