Optical Review最新文献

The formation of thrombus in blood may be a cause of thrombosis which induces symptoms, such as myocardial infarction, cerebral infarction, and economy class syndrome. Recently, investigations on blood flows inside artificial blood vessel and artificial organ have been performed energetically for clinical application. Thus, in vitro monitoring of thrombogenesis in blood flow inside them is thought to be essential to optimize their function for stable blood perfusion in such as artificial dialysis system and blood transfusion system. In the present study, we propose a method for monitoring the size and dynamics of thrombus in artificial blood flow using speckle patterns obtained under the illumination of coherent light. We experimentally discuss the spatial and temporal variation information on speckle patterns in relation to the size and dynamics of thrombus, respectively, under illumination of a laser diode. The above information contributes to the quantification of degree of thrombogenesis. Experimental results show the feasibility of the present method for in vitro monitoring of the formation of thrombus in artificial blood flow.

Heat-assisted magnetic recording (HAMR) is a promising technology for improving the recording density of hard disk drives. A near-field transducer (NFT), which forms a small light spot on a recording medium, is necessary in HAMR. The authors’ group previously proposed a novel device, in which a metal nano-antenna acting as an NFT is attached to a semiconductor ring resonator acting as a light source via a dielectric spacer. In this study, the temperature rise including the recording medium using this device was analyzed through the combination of optical and thermal simulations. To reduce the temperature rise of the nano-antenna while heating the recording layer to the Curie temperature, the following two methods were used: first, the nano-antenna length and the spacer thickness were optimized. Second, a heat spreader, which surrounds the nano-antenna, was introduced. The nano-antenna was made of Au, and the spacer and heat spreader were made of SiO₂. When the peak temperature of the recording layer was 800 K, the temperature of the nano-antenna was 3350 K without the above methods, but it was significantly reduced to 400 K with the above methods. This is a sufficiently low value to keep the hardness of the nano-antenna. On the other hand, the thermal spot size in the recording layer was slightly increased from 62 × 64 nm² to 67 × 72 nm² by the above methods.

An aerial 3D image formed by the use of a 3D-shaped light source gives a greater sense of reality compared to the conventional aerial 2D image. In particular, an aerial image of hollow face evokes a kind of illusion that the direction of the face changes depending on the viewing direction. In this study, we investigate the viewing zone of an aerial 3D display that employs a 3D object as a light source in aerial imaging by retro-reflection (AIRR) optical system. The viewing zone is defined by the minimum observation distance and viewing angle where the entire width of the aerial 3D image is visible. The Formulae for the viewing zone are derived and confirmed experimentally. 3D objects in various shapes are used in the experiments. The aerial 3D image of each object was observed in the corresponding viewing zone. Hollow face illusion was evoked even under binocular observation. We have clarified the optical design of our proposed AIRR optical system for hollow face illusion.

Nonlinear photoacoustic-based methods for measuring high-speed blood flow velocity typically use a single-pulse laser or a dual-pulse laser system with high repetition rate to achieve thermal tagging and acoustic excitation at the same time. However, the peak power of the pulsed laser is too high and can easily exceed the damage threshold, causing the blood to be overheated, which limits the application of this method in living tissue. In this paper, we propose and confirm a method of detecting high-speed blood flow with a low-power continuous laser-assisted nonlinear photoacoustic. We first establish a model of the relationship between the attenuation of Gruneisen parameters and velocity. Based on this, we further develop a theoretical relationship between the change of photoacoustic signal and the blood velocity. Then we used a low-power continuous laser for thermal tagging and a low repetition rate of pulsed laser to excite photoacoustic signals in the experiment. After calibration, the results show that the velocity measured by this method is in good agreement with the actual velocity and the highest flow velocity can be measured was 100 mm/s under our experimental conditions.

Optical interconnection technology is the most promising solution for on-chip multi-core interconnection because of its advantages over electrical interconnection. To improve the performance of on-chip optical interconnection network architecture, a novel 5 × 5 full-duplex communication optical routing switch based on microring is proposed. A novel microring resonator switch formed by covering a layer of insulating layer HfO₂ and a layer of activating material indium-tin oxide on the traditional microring resonator is used as the switch unit. The 15-microring topology enables non-blocking switching of 5 bidirectional ports, reducing power consumption and area. The results show that the maximum insertion loss of the optical router is 1.485 dB, the average insertion loss is 0.904 dB, and the average energy consumption is only 5.7211fJ, and the response time is less than 12 ns. The optical router has the advantages of simple structure, small size, and low-energy consumption, and can be widely used in signal processing systems, communication systems, and interconnection systems.

In this paper, based on a scale-adapted set of Laguerre-Gaussian modes, a theoretical model has been presented for evaluating the coupling efficiency of modes and mode crosstalk between different spatial modes caused by transverse offset and angular misalignments. A proof-of-model demonstration is performed for three-mode fiber, and the results show that the coupling efficiency and mode crosstalk of various modes behaves differently in the presence of axial offset and the direction of the misalignment. And it is also demonstrated that the proposed scheme can be scalable to analyze the FMFs with a large number of modes. On the basis of this model, the tolerance of coupling efficiency to the fusion splice conditions with different FMF parameter is analyzed. The results show that the larger the FMF normalized frequency V, the smaller the tolerance of spatial mode coupling to the transverse offset value. With the increase of V value, the tolerance of self-coupling efficiency and mode crosstalk to angular misalignments changes regularly. Therefore, the transverse offset and angular misalignments of fusion splice with different FMF parameters need to be strictly controlled to achieve suitable mode coupling efficiency and mode crosstalk.

In this paper, we revealed that the pseudo-3D perception of a 2D aerial image is increased by reducing the luminance and contrast of the background pattern, and by adding image movement that changes the shape and shading of the aerial image. In recent years, aerial images are used in our daily lives as entertainment, aerial touch panels etc. Most of them are 2D aerial images, but we sometimes perceive the depth of them as 3D objects. In this paper, we call this phenomenon pseudo-3D perception. However, it is not revealed what factors affect the pseudo-3D perception of 2D aerial images. Therefore, we evaluated what factors affect it. Especially, we evaluated how the luminance and contrast of the background pattern of the aerial image and the depth position of the aerial image relative to the background affect the pseudo-3D perception of the 2D aerial image. In addition, we evaluated how adding movement to the 2D aerial image affects the pseudo-3D perception of the 2D aerial image.

The purpose of this study is to apply digital image processing to original images acquired with common digital devices to generate the resulting images that are easy for the elderly to see without using colorimetric values. Therefore, we propose an image enhancement method to improve color visibility of digital images for the elderly, taking account of their color vision characteristics. The proposed method consists of lightness conversion by adaptive gamma correction according to the effective luminance ratio of the young and the elderly, contrast enhancement using an S-shape function, and hue preservation processing in the RGB color space. The effectiveness of the proposed method is illustrated by comparing it with other conventional methods through experiments using many natural images.

Two technologies for improving image gaps and narrow viewing angle were applied to a space-saving compact aerial display with striped retro-reflector on a LED panel. The aerial image gaps created by the striped retro-reflector structure was smoothed by scrolling the images perpendicular to the stripe direction. The narrow viewing angle inherent to the compact aerial display was successfully improved by increasing the width of the striped retro-reflector, verified by both theoretical calculation and measurement. These improvements in the space-saving compact aerial display would greatly expand its applications, such as digital signage and touchless interface.