Minute particle detection using a light-wave-guide incorporated optical total analysis system

An optical sensor combined total analysis system (TAS) is thought to be one of the most effective functional elements in realizing a ubiquitous human healthcare system. In accordance with this concept, we have proposed a fundamental structure of a light-wave-guide incorporated TAS and have developed a micro fluidic channel fabricated chip, where two light waveguides having approximately 10-??m cores were facing each other across a fluidic channel with a width of 12???m. By passing 5-??m-diameter polystyrene particles across the portion where a light-wave-guide and the fluidic channel intersect at a right angles, we confirmed that changes to transmitted light and scattered light were detectable even with an extremely low laser source power of 5???W, and they increased proportionally as the introduced laser power became higher. Increasing the introduced laser power clearly increased the correlation between the transmitted and scattered light change. Here we discuss in detail the two different correlation tendencies that appeared in the correlation maps.     

Illumination and scattered light detection using a light source consisting of sub-micrometer defect arrays formed on a extremely flat light waveguide core

We have previously argued that an optical sensor combined total analysis system (TAS) is one of the indispensable functional components needed to realize a “ubiquitous human healthcare” system. To achieve this goal, we have proposed a fundamental structure for illuminating a minute cell or particle running along a microfluidic channel using a flat waveguide construction. It is desirable that the TAS light source should be arranged as close to the specimen flow as possible in order to acquire the necessary optical properties; hence, artificial defects formed on the surface of a flat light waveguide are considered to be a promising candidate for realizing the arbitrary-shaped light source for a highly functional optical TAS structure. Based on this idea, we fabricated a structure, constructing a flat and square light source consisting of rectangular solids, sub-micrometer in size, with a 1-μm thick and a 12-μm wide light waveguide core. We successfully trial-manufactured an optical TAS chip with a fluidic channel containing a 14 × 10-μm cross section, and an extremely flat light waveguide core. We repeatedly confirmed that the defect array could function as an approximately square light source when a 650-nm wavelength laser power was carefully introduced. Furthermore, we developed a hybrid numerical calculation method base on the finite-difference, time-domain method together with the beam propagation method. Utilizing this hybrid method, we evaluated the optical response when a particle runs across the light source while changing the aperture length of a shading mask to obtain signals with both higher intensity and shorter full width at half maximum. The numerical results were compared with experimental results obtained using an image acquisition system, and demonstrated good qualitative accord.     

Preliminary scanning fluorescence detection of a minute particle running along a waveguide implemented microfluidic channel using a light switching mechanism

It has long been thought that an optical sensor, such as a light waveguide implemented total analysis system (TAS), is one of the functional components that will be needed to realize a “ubiquitous human healthcare system” in the near future. We have already proposed the fundamental structure for a light waveguide capable of illuminating a living cell or particle running along a microfluidic channel, as well as of detecting fluorescence even from the extremely weak power of such a minute particle. In order to develop novel functions to detect the internal structure of living cells quickly, an angular scanning method that sequentially changes the direction of illumination of the minute cell or particle may be crucial. In this paper, we investigate fluorescence detection from moving particles by switching the laser power delivery path of plural light waveguides as a preliminary experiment toward this novel method. To construct an experimental system able to incorporate a switching light source mechanism cost effectively, we utilized a conventional TAS chip with plural waveguide pairs arranged in parallel, and a forced vibration mechanism on an optical fiber tip by a piezoelectric actuator. With this system, we performed an experiment to detect extremely weak fluorescence using micro particles with a fluorescent substance attached and an optical TAS chip that incorporated a microfluidic channel and three pairs of laser-power-delivering light waveguide cores. We successfully obtained clear, quasi-triangular-shaped pulses in fluorescent signals from resin particles running across the intersection under three different conditions: (1) a particle with approximately the same velocity as that of a forced-vibrated optical fiber tip of approximately 700 mm/s, (2) a particle with velocity 1 digit smaller than that of an optical fiber tip, and (3) a particle with velocity approximately 1/20 that of an optical fiber tip.     

Polarization of light scattered by clover

This study was undertaken in order to better understand the factors that govern the polarization of light scattered from vegetation and soils. This phenomenon is not well understood but is potentially of interest for remote sensing of the earth. The intensity and polarization of light scattered by clover in vivo and soil were measured at a number of different angles of incidence and reflectance. Both individual leaves and natural patches of vegetation were measured. The Umov effect, or inverse relation between polarization and reflectance noted by many earlier workers, was observed here and is shown to be a very general property of diffusely scattering surfaces. The light transmitted through the leaves was found to be negatively polarized. The polarization of light scattered from aggregations of leaves is affected by this negatively polarized, transmitted light. The light scattered from the upper leaf surfaces was found to be positively polarized in a manner which could be accounted for quantitatively by specular Fresuel reflection from small, randomly oriented facets on the surfaces of the leaves.     

基于FPGA的高速光幕同步系统设计与实现

常规光幕实现发射器和接收器双方信号的同步需要专用同步电缆来完成。针对这一缺点,提出了一种新的高速光幕同步方法,即在发射器的每个循环周期的第一通道发射光脉冲之前增加一个作为帧同步码的光脉冲段,接收端通过判断帧同步码的方式实现收发信号同步,这样便不再需要专用同步电缆,有效地节省了光幕同步系统成本。进一步地,采用新提出的高速光幕同步方法,基于FPGA技术,设计并实现了高速光幕同步系统的总体方案,硬件制作了可应用于高速运动物体的实时到位检测的高速光幕检测装置。实际工程应用表明,采用此方法的高速光幕检测装置,成本低,工作稳定可靠,捕捉与同步性能优良。     

Detection of fluorescence from a mixed specimen consisting of micro particles attached to different fluorescent substances using a light waveguide incorporated optical TAS

A “ubiquitous human health care system” will require a monolithic optical total analysis system (TAS) consisting of waveguides and microfluidic channels based on a transparent resin chip. Together with the rapid development of the fluorescent marking method, fluorescence analysis by TAS of mixed-microparticle specimen attached to different fluorescent substances will be necessary. Towards realization of this, we here propose a novel method for using a part of the fluorescence acquired by irradiating microparticles with AC-modulated laser power as light dedicated to the discrimination of fluorescent substances. Since the light power for discrimination was extremely weak, we extracted effective signal components using a lock-in detection method. Then, by comparison with the signal of the original fluorescence, we could determine whether the fluorescence signal was from the microparticles attached to the fluorescent substance to be discriminated. Using a mixed specimen composed of microparticle-attached fluorescent substances with emission peaks of 520 nm and 600 nm, we found that 10% of the acquired fluorescence could successfully determine the specified fluorescent substance as a discrimination signal. The peak value of the discrimination signal was approximately double the amplitude of the stationary noise in the discrimination signal.

     

Modeling and analysis of a hybrid communication channel based on free-space optical and radio-frequency technologies

The mathematical model of a high-speed hybrid communication system based on free-space optical (FSO) and radio-frequency (RF) technologies is considered. Multimedia information is transmitted using two communication lines operating in the hot redundancy mode, namely, an FSO channel and a millimeter radio-frequency channel. In addition, we derive ergodicity conditions for the Markov process describing the system operation and provide some performance characteristics for the hybrid communication channel.     

An optical target to eliminate impinging light in a light scattering simulation

Based on the Convolutional perfectly matched layers (CPML) absorbing boundary condition algorithm that is implemented at the outer boundary of a light scattering simulation, we propose a numerical target that can eliminate light impinging upon it from arbitrary directions. To model light propagation through random media to a specific position, elimination of light reaching the target position is necessary to prevent further reverberation through the simulation space and become a source of noise. Various factors that affect the performance of the optical target are analyzed, including shape of the wavefront and alignment of the impinging light. Simulation results show that incident light can be most effectively eliminated for incident wavefront normally impinging upon the optical target.     

基于布里渊散射的结构应力光纤测试技术研究

作者通过分析一定功率的脉冲光射入光纤中的布里渊散射规律,介绍了分布式光纤测量测量轴向应力的基本原理;制作实验装置,测量单独的应变模型,分析散射回来的波形图,初步了解应力在光纤布里渊散射波谱上的图像特征;将应力作用于光纤的不同位置,对比它们与无应力作用诗所得到的散射波形之间的图像差异,研究其对光脉冲在光纤传输过程中的影响规律;结果表明,应力的作用大小,作用位置的不同都会对脉冲光的传播造成影响,主要在于影响布里渊散射的斯托克斯光和反斯托克斯光;本次研究所得可以为分布式光纤测量提供参考,为分布式光纤在测量微型形变的应用中有一定的促进作用;本次研究的创新点在于使用滑轮的方法,解决同等应力在分布光纤的不同位置作用效果。     

Mathematical simulation of ultrashort light pulse propagation in a highly scattering medium

The problem of probing a nonhomogeneous medium imitating the biological tissue by an ultrashort light pulse is investigated. The pulse propagation in the medium is described by a transient transport equation. A grid algorithm for its solution based on the analytical presentation of the density of the unscattered photon flux is presented as well as a semianalytical algorithm for computing the density of the flux of singly scattered photons. Methodological calculations carried out by the grid method and by the alternative Monte Carlo method are given.     

Interaction of guided light in rib polymer waveguides with dielectrophoretically controlled nanoparticles

This work demonstrates an optofluidic system, where dielectrophoretically controlled suspended nanoparticles are used to manipulate the properties of an optical waveguide. This optofluidic device is composed of a multimode polymeric rib waveguide and a microfluidic channel as its upper cladding. This channel integrates dielectrophoretic (DEP) microelectrodes and is infiltrated with suspended silica and tungsten trioxide nanoparticles. By applying electrical signals with various intensities and frequencies to the DEP microelectrodes, the nanoparticles can be concentrated close to the waveguide surface significantly altering the optical properties in this region. Depending on the particle refractive indices, concentrations, positions and dimensions, the light remains confined or is scattered into the surrounding media in the microfluidic channel.     

A simple parameterization of canopy reflectance using photon recollision probability

Information on the fractions of incident radiation reflected, transmitted and absorbed by a plant canopy is crucial in remote sensing of vegetation and modeling of canopy microclimate. Photon recollision probability p allows to calculate easily the spectral behavior of canopy scattering, i.e. the sum of canopy reflectance and transmittance. However, to divide the scattered radiation into reflected and transmitted fluxes, additional models are needed. In this paper, we present a simple formula to estimate the fraction of radiation scattered upwards by a canopy. The new method is semi-empirical, makes use of the concept of photon recollision probability, and is derived from an analysis of modeling results. Although a physical interpretation is given for the single additional parameter needed in the formula, the scattering asymmetry parameter q, the method is not strictly based on the radiative transfer equation. Our results indicate that the method is accurate for low to moderate leaf area index (LAI) values, and provides a reasonable approximation even at LAI = 8. In addition, we present a method to compute p using numerical radiative transfer models.     

Construction of substantially different solutions of an inverse problem for a toroidal plasma equilibrium equation

The paper is devoted to the reconstruction of the current density in toroidal plasma, using experimentally measured data. The toroidal current density is characterized by two functions in the right-hand side of the Grad-Shafranov equation which, together with the poloidal flux, is to be deter-mined. The question about the uniqueness of the solution of the inverse problem was usually not addressed in the numerical methods developed over the past few decades. However, the theoretical study of this question for simplified models showed the possibility of the existence of substantially different solutions. For a correct understanding of the physical properties of a pulse it is necessary to analyze all possible solutions of the inverse problem in its physically correct formulation. This formulation is presented in the paper. A new numerical method for determining all substantially different solutions of the inverse problem is proposed. Examples of the existence of such solutions are constructed for plasma parameters which are close to experimental.     

Modeling and simulation results on a new Compton scattering tomography modality

Conventional tomography (X-ray scanner, Single Photon Emission Computed Tomography, Positron Emission Tomography, etc.) is widely used in numerous fields such as biomedical imaging, non-destructive industrial testing and environmental survey, etc. In these tomographies, a detector rotates in space to collect primary radiation emitted or transmitted by an object under investigation. In this case Compton scattered radiation behaves as noise hindering image quality and consequently correction to scatter should be required. However recently an interesting new imaging concept, which uses precisely scattered radiation as imaging agent, has been advocated. The camera records now images labeled by scattered photon energy or equivalently by scattering angle. In the present paper we propose a new modality of Compton scattering tomography (CST), akin to the X-ray scanning tomography, in the sense that it works in transmission modality but uses Compton scattered radiation to recover the electron density of the studied medium. The new image formation modeling is based on a new class of Radon transforms on circular arcs (CART). Through numerical simulation results we show the feasibility and the relevance of this new imaging process.     

Hybrid analog/digital wavelength-time optical CDMA systems in radio-over-fiber transmissions

This study presents a hybrid analog/digital (A/D) mechanism of two-dimensional (2-D) structure of wavelength-hopping and time-spreading coding optical code-division multiple-access (OCDMA) system for future generation communication and network technologies. The 2-D method increases the maximum permissible number of simultaneous base stations (BSs) and security using a finite bandwidth of optical broad-band light source (BLS). In the proposed system, we can employ low-cost BLS which can mitigate the sampling rate of optical switch (OSW) and has the advantage of power saving. The performance enhancement is using the time-spreading method by a Mach-Zehnder modulator (MZM) with switch function to suppress the phase-induced intensity noise (PIIN) effect of the wavelength domain and the receiver structure is equipped with balanced detectors in order to suppress the multiple-access interference (MAI). In addition, the hybrid OCDMA network is equipped using a dual input MZM for the choice which time analog or digital signals to be transmitted and the advantage of these two kinds of signals can transmit by the same coder/decoder (codec) mechanism and recover by different type filters in the receiver end. The numerical evaluation results demonstrate that, for analog and digital signals under PIIN- and MAI-limited conditions, the proposed system outperforms a conventional multi-wavelength and time-spreading OCDMA scheme. Hence, enhancing the confidentiality of the asynchronous networks of codeword assignments and integratable hardware designs for the scheme with a MZM, an optical switch (OSW), arrayed-waveguide grating (AWG) and fiber Bragg gratings (FBGs) in hybrid A/D 2-D OCDMA system is proposed.     

一种新型颜色传感器设计

本文介绍一种采用脉冲光源照明、双光纤束导光的新型颜色传感器，光电探测器由光电二极管和覆盖其上方的滤色片组成。用光电积分法进行测量，在整个可见光谱区间内，对反射光谱功率进行积分，得到被测物体的颜色三刺激值X、Y、Z。同步控制脉冲光源发光与电路测量，由双光路捡测系统测量颜色三刺激值X、Y、Z和脉冲光源的微小变化，并根据后者对测试结果实时修正。该颜色传感器适合于本身不发光物体的表面颜色测量。     

Development of inverse dynamic model for a surgical hybrid parallel robot with equivalent lumped masses

Robotic-assisted surgery is a continuously developing field, as robots have demonstrated clear benefits in the operating room. This paper presents the inverse dynamic model (in the case of using the laparoscope as a surgical instrument) and some characteristics of a 5-DOF hybrid parallel robot designed for minimally invasive surgery. The new inverse dynamic model is obtained using the virtual work method on the basis of dynamically equivalent lumped masses. The simulation and numerical results have been obtained for the experimental model of the developed PARASURG-5M robot, showing that the analytical inverse dynamic model could be used in the control of the robot. Finally, a comparison between the simulation data obtained in Matlab (IDM) with the simulation data through a Multi-body Simulation software (MBS), namely Adams (MBS) has been performed.     

一种竹丝正反面辨识传感器及其辨识方法

为了解决竹席编织自动送丝系统中准确区分原料竹丝正反面的问题,设计了一种竹丝正反面辨识传感器。传感器机械结构与竹丝反面中心凹槽构成光通道,红外光经过该光通道传播至红外光敏三极管,通过检测三极管的c-e极电流可测得红外线的光通量,进而识别出竹丝的正反两面。此外,还研究了单个传感单元对竹丝正反两面输出电流的分布曲线,并给出了一种同质多传感单元条件下的融合策略。经实验,该传感器能快速准确地识别原料竹丝的正反面,为实现竹席编织自动送丝系统提供了基础。     

Study of polarization state of the transmitted light through the cholesteric liquid crystal

In this paper we describe a new Jones matrix, in which the matrix element is the complex exponential. Using this matrix we theoretically study the properties of the cholesteric liquid crystal. It is found that the left-hand circular polarized light of wavelength being equal to pitch of the cholesteric liquid crystal is totally reflected when it propagates along its helical axis and that the right-hand circular polarized light simply transmitted. We also analyze the polarization state of the transmitted light through the cholesteric liquid crystal with different optical pitch. The theoretical analysis shows that the polarization state of the transmitted light will change after the polarized light pass through the cholesteric liquid crystal. Furthermore, we also explain the reason of the selective reflecting of cholesteric liquid crystal for visible light.     

Optical system design for light detection and ranging with ultra-wide field-of-view using liquid lenses

The light detection and ranging (LiDAR) technology is based on irradiating near-infrared light and measuring the time-of-flight of the scattered light in an object. This technology is becoming increasingly important, as the requirement of three-dimensional camera technology for future autonomous vehicles is on the rise. In this study, we propose an ultra-wide field-of-view (FOV) optical system for LiDAR that can sequentially scan a beam emitted from a high power laser through a small beam steering system using a liquid lens and a fisheye lens. The proposed optical system consists of a series of liquid lenses for beam steering, a commercial fisheye lens with a wide FOV, and a relay optics to effectively conjugate the intermediate image planes of the two lens systems. To verify theoretical feasibility, we have designed a practical optical system with an FOV of approximately 170°, which is much higher than the FOVs in any other non-rotating LiDAR systems.