新型旋光仪测量原理的研究

在对传统旋光仪旋光度测量原理分析的基础上提出了一种新的测量原理。利用该测量原理可以省略传统旋光仪中的机械部分。该原理充分运用光电检测技术和法拉第磁光效应,利用光电池检测经过法拉第线圈和待测溶液后的线偏振光,并将此信号与驱动法拉第线圈信号的相位进行比较,从而实现对旋光物质旋光度的测量。通过旋转起偏器实验模拟了该方法的可行性。     

双功能静态光电显微镜的探讨

一、引言静态光电显微镜是一种高精度瞄准器,大多用于线纹尺的刻制及检定中。我们对光亮法双功能静态光电显微镜的设计方案进行了研究和探讨,应用谐波分析理论,对两种功能状况下的静态光电显微镜的光电信号进行了计算与分析。结果表明,在现有仪器装备条件下,只需对电路稍加改装,并选用三次谐波分量做为测量的输出信号,即可实现仪器     

基于微环谐振器的溶液浓度传感器研究

设计了基于微环谐振器的溶液浓度传感器,提出了一种溶液浓度测量的新方法。介绍了全通微环谐振器(MRR)的结构及传输机制和MRR浓度传感器的工作原理。根据电磁场理论得到了狭缝波导的特征方程,计算了MRR的共振波长,并以乙二醇溶液为例,利用有限时域差分法模拟了外界环境浓度变化时微环的功率谱。模拟结果表明:随着乙二醇溶液浓度增大,MRR的谐振波长与乙二醇溶液浓度的变化近似呈线性关系,与理论计算结果一致;并对该传感器的灵敏度进行计算,结果显示灵敏度可达490.2nm/RIU。采用MRR测量液体浓度成本低、结构简单,能够实现对环境介质的快速精确测量。所设计传感器还可用于测量固体、气体浓度和其它与浓度、折射率相关的参量。     

基于表面等离子体共振技术油水持率传感器的实验研究

为研究表面等离子体共振技术在油井产液剖面持率参数测试方面的潜在应用,采用磁控溅射方法在三棱镜底面沉积不同厚度的金膜,制作Kretschman型表面等离子共振传感元件,对不同体积浓度的油水折射率进行测定。实验结果表明,对于折射率相同的三棱镜,沉积的金膜厚度越大,共振吸收峰越弱。表面等离子体共振峰位对不同体积浓度的油水介质很敏感,介质体积浓度由低到高变大时,表面等离子体共振吸收峰向右平移,共振角逐渐增大。实验表明,表面等离子体共振传感测试技术对不同浓度油水介质的折射率变化非常敏感,能够用其进行流体持率的测量。     

基于强度调制的液体浓度检测系统

介绍了一种光纤传感器液体浓度实时检测系统，采用了5mW的激光二级管LD、光纤光电耦合器、U型敏感元件以覆PN结型光电二极管（PD）为主要的组成部件。光在U型敏感元件中传输时发生全反射，同时被测液体的浓度对光强进行调制，通过测量输出端电压的变化来测量液体浓度的变化。实验以食盐和蔗糖溶液为测量对象，精度可以达到0．05％，测量结果与理论分析十分相符。这个实验装置的显著优点是体积小、结构简单、测量范围宽，能够实现液体浓度的在线测量与生产的自动化。     

EEMD结合小波阈值的光电容积脉搏波信号降噪

为了研究脉搏波信号降噪的问题,文章提出了一种集合经验模态分解(Ensemble Empirical Mode Decomposition,EEMD)与小波阈值相结合的降噪方法,对采集到的光电容积脉搏波信号来做降噪处理,同时和EMD结合小波阈值降噪算法进行比较。算法首先把信号做EEMD的分解,将原始信号分解为n个模态分量(Intrinsic Mode Function,IMF),然后对这些分量做相干性的计算,对其中的噪声分量来做小波阈值降噪,最后将信号重构。原始信号在STM32平台上采用MAX30100传感器测得。实验结果表明:本文的方法能够很好地剔除光电容积脉搏波中包含高频噪声与基线漂移的各种噪声,降噪后信噪比为34.09,均方根误差为1.99。提高了PPG信号的质量,为光电容积脉搏波信号的准确测量提供了新的思路。     

基于STM32的可见分光光度计设计

设计了一种基于STM32F103系列处理器为控制核心的可见分光光度计,实现了在可见光谱区域对样品物质进行定量分析,可以实时显示透射比、吸光度、溶液浓度、浓度因子。系统采用具有超低暗电流的硅光电池进行光电信号转换,电流信号经过由正负电源供电的精密运放芯片进行放大处理,然后由MCU进行A/D采样和数据处理,通过液晶屏显示透射比等参数。测量结果显示,该系统的测量结果非常精确,并且具有很好的重复性和响应速度。     

消光法测量乳剂颗粒的研究

为研究消光法颗粒粒径测量中浓度和双层球形颗粒问题,根据Lambert-Beer定律,对不同浓度下的乳剂和PBA/PMMA双层球颗粒乳剂采用多波长消光法进行测量分析。实验结果表明:当颗粒物浓度超出某一临界浓度范围后,由消光法测量的粒径结果将受浓度变化的剧烈影响;对于核壳结构的双层球形颗粒,如果两层结构的折射率相差不大,采用其中一种折射率通过消光法来测量,其结果仍比较准确,误差不大。     

双散射角光学粒子计数器的研制

为了实现同时测量气溶胶粒子的谱分布和折射率,研制了一种新的双角度光学粒子计数器(D-OPC),该计数器采用60°和110°双散射角系统对气溶胶谱分布进行测量.利用Mie散射理论定义敏感函数,选取两个最佳的散射角,使其既对折射率敏感又不线性相关.然后,利用气溶胶折射率对两个散射角系统敏感性的差异来反演气溶胶折射率.最后,利用该仪器对大气气溶胶谱分布以及折射率进行实际测量.与TSI公司黑炭仪和浊度计测量的吸收系数和散射系数对比表明,双散射角光学粒子计数器测量气溶胶折射率和谱分布结果合理,测量误差<20%,可以满足同时测量气溶胶粒子谱分布和折射率的需要.     

基于倾斜光纤光栅的液位传感特性研究

研究了一种基于倾斜光纤布拉格光栅(TFBG)的液位传感器,利用OptiGrating软件仿真分析了外界折射率和温度对TFBG透射谱的影响,仿真结果表明,当外界折射率为1.408～1.444时,TFBG透射谱包层模的透射谱幅值随外界折射率的增大逐渐减小,且不受温度的影响,但峰值波长随温度升高而增加。同时,搭建了液位和温度测量实验装置,对不同浓度的5种甘油溶液进行液位测量,并采用包层模归一化面积作为液位测量量度来提高灵敏度,证实随着液位的升高,归一化面积逐渐减小,且溶液折射率越接近包层折射率,液位测量灵敏度越高。同时,可利用TFBG布拉格谐振峰中心波长的漂移量与包层模归一化面积实现温度与液位的同时测量。     

The effect of refractive index of the mounting medium on the apparent diameter of latex particles and glass fibres

The diameters of latex particles were measured in different media with a light microscope. The microscope was fitted with a filar micrometer eyepiece and, for measurement, the cross-wire was set on the centre of the dark line forming the edge of the image. Electron microscopy was used for comparison. Good agreement between light and electron microscopy was obtained using media of relative refractive index (n_d object/n_d medium) between 1·06 and 1·08. With higher relative refractive indices the light microscope underestimates dimensions for particles 4·17 μ diameter and overestimates for particles 2·7 μ diameter.     

基于后向光散射的颗粒测量技术研究

颗粒粒径和颗粒折射率是光散射颗粒测量技术中的重要参数。为了实现颗粒粒径的测量及其分档,在广义Mie理论基础上,分析了颗粒粒径及折射率对后向散射光能分布的影响,并得到了后向散射光能分布随颗粒粒径及折射率呈周期变化规律。实验验证结果表明,后向散射光能与颗粒粒径及颗粒浓度有关。研究结果可为后续的颗粒测量研究提供参考。     

基于低相干光干涉的液体折射率测量

液体折射率是液体一个重要指标,介质中折射率的变化会影响光程,提出一种用低相干光干涉测量光程变化,进而测得折射率的方法。通过调节两束低相干光使它们之间的光程差在相干长度之内,将被测液体放入一束光路中,根据光电探测器得到的干涉信号可求得相应的光程变化量,进而得到待测液体的折射率。利用低相干光干涉测量折射率的方法,其测量和计算过程方便快捷,受外界限制因素小,在810nm波长下,对折射率的测量精度可以达到10-4量级以上,是测量各种液体折射率的有效方法。     

角度位置自动识别的红外折射率测量

为准确快速获得块体硫系玻璃红外波段的折射率,搭建了基于类准直测量法的折射率测量系统。该系统采用液氮制冷的碲镉汞探测器和特殊的光路实现了光强信息的高分辨采集,使用高分辨数据采集卡将角度信息数字化,利用精密步进电机传动控制系统实现了光强信号与位置信号的同步记录。开发的测量软件可自动判别光强峰位信息,自动计算获得待测样品的折射率。对比测试Ge_(20)Sb_(15)Se_(65)、Ge_(28)Sb_(12)Se_(60)、As_2S_3和As_2Se_3商用硫系玻璃在3.39μm和4.8μm处的折射率。实验结果表明,该装置系统测量折射率的标准偏差为10~(-3),测量不确定度为0.002 9,可快速、准确测量块体材料红外波段的折射率。     

Note: Refractive index sensing of turbid media by differentiation of the reflectance profile: Does error-correction work?

A widely used method for determining refractive index postulates that the derivative of the angular profile for light reflected from the sample is maximum at the critical angle for total internal reflection (TIR). It is well-known that in turbid media this "differentiation method" yields errors in refractive index. Unexplained anomalies in previous error-calculations are eliminated if one uses a recent model of TIR which departs from traditional Fresnel theory. However we find that, in practical situations, the refractive index obtained by differentiation even after error-correction is significantly different from the best estimate for the refractive index obtained by curve-fitting the reflectance data. Thus the differentiation method lacks scientific validity in turbid media.     

微注塑保压时间对平面透镜相对折射率的影响

针对透明器件对光学性能要求很高的现实，提出通过调控相对折射率来实现光学性能调控的方法。以微注塑薄壁透镜为例，对平行激光光源通过光学透镜后的波阵面进行检测与重建;接着推导出了波阵面检测结果与相对折射率的理论关系，并计算了透镜内部相对折射率的分布;最后考查了微注塑过程中保压时间对透镜相对折射率分布的影响。实验结果表明：当微注塑保压时间从1s延长至3s时,相对折射率分布均匀度明显提高，折射率的极差从6.1×10-3减小到2.9×10-3。该相对折射率表征方法能有效调控光学制品性能。     

Modern techniques in reflectance measurements

In the field of quantitative investigation of microscopic images reflectance measurements with the aid of photoelectric equipment play an important role. Reflectances can be used for the identification of various components in a polished specimen, for chemical analysis and for the determination of the refractive index of a specimen as well as for a determination of the various absorption parameters of reflecting solid material. The parameters involved are: reflectances at given wavelengths, spectral reflectance curves in the visible, UV-, and near IR-spectral range, reflectances of optically anisotropic surfaces at varying orientations of the vibration plane of linearly polarized light, reflectances in air and in an immersion liquid (mainly in standard immersion oil). From spectral curves, quantitative expressions of colour can be derived. Due to improvements in reflectance standard materials and technical design of apparatus the measurements and calculations can be carried out very conveniently, quickly and precisely.     

光在多层不匹配介质中的稳态传输

分析了光在多层不匹配折射率介质中的漫射方程,给出了精确的漫射方程解。用蒙特卡罗方法检验了稳态的漫射方程。通过与多层介质的空间分辨漫反射蒙特卡罗方法的比较,验证了方法的正确性。讨论了有限尺寸光源和折射率的变化对空间分辨漫反射的影响。实验结果表明,折射率的变化对漫射的影响会因折射率的不同而不同,折射率在1.35~1.45之间变化时,最大误差为7%.     

Near-Field Nanofluid Concentration Measurement by Rayleigh Particle Scattering Bragg Grating Evanescent Wave

We report an approach to detect near-field nanofluid concentration by scattering Bragg grating evanescent wave (EW). Since the suspended nanoparticles can enhance the scattering intensity of the EW from the thinned and tapered fiber with Bragg grating, the reflectance ratio of Bragg grating is dependent on the corresponding refractive index (RI) of the nanofluid at different nanoparticle volume fraction. A critical reflectance ratio measurement identifies the nanofluid concentration. Theory and simulation of scattering Bragg grating EW was analyzed. The scattering Bragg grating EW fiber sensing probe was designed and fabricated by the wet chemical etching method, and calibration was made by several chemical solutions without suspended nanoparticles. The example application of the nanofluid containing dispersed 40 nm SiO₂ nanoparticles demonstrates the feasibility. The reflectance ratio decreases by over 3.2% with the nanofluid concentration increasing from 0.25 wt.% to 4 wt.%, while the temperature disturbance can be negligible.     

A method for controlling the spins of atoms using optical near-fields

On the basis of the procedure for controlling the spins of atoms using circularly polarized evanescent light proposed by Hori et al.[(1996 ) Abstracts of the 1st Asia‐Pacific Workshop on Near‐field Optics] we discuss the influence of boundary conditions on the probability of spontaneous emission and thus on the spin polarization efficiency, which was not considered in the Hori et al. study. Using the Carniglia–Mandel mode expansion of electromagnetic fields, we derive the spontaneous emission and spin polarization probabilities of atoms near a dielectric surface, and show the atom–surface distance dependence and refractive index dependence. Numerical evaluation for the 6P_1/2–6S_1/2 transition of a Cs atom indicates an increase in the efficiency of spin polarization by 30%.