Measurement of aerosol absorption using photothermal low coherence interferometry

研究了气溶胶粒子的光热敏效应和热感应光致折射率变化,提出了通过增加光热作用区个数来提高探测灵敏度及用低相干干涉法降低成本的方法.建立了光热低相干干涉法测量大气气溶胶吸收系数的数学模型,分析了干涉仪正交状态测量和干涉条纹细分探测两种方式下的探测灵敏度,讨论了低相干偏振干涉情况下的探测限.结果显示,在典型条纹细分情况下理论探测灵敏度可达1×10-6m-1;增加光热作用区m个,探测灵敏度理论值可提高m倍.理论和方法研究证明光热低相干干涉法具有可直接测量大气气溶胶吸收系数、在线原位、低成本,易于进行温度修正等优点.     

应用于眼轴参数测量的光学相干层析系统

生物测量在眼科疾病的诊断和治疗中越来越重要,对儿童和青少年的眼轴长度进行监测有助于预防和治疗近视及其引发的眼科疾病,眼轴参数的准确测量也是影响眼病患者术后视觉质量的重要因素。为了测量眼轴参数,本文研究了基于时域低相干技术的眼轴测量方法,研制了高精度、非接触式眼轴测量的原理样机,并开展了相应的实验研究。利用低相干干涉技术与长相干干涉测距技术结合的方法,采用时域的机械扫描方式,搭建一套光纤型低相干层析测量系统。通过对标准透镜厚度和镜面间隔的测量实验,重复测量精度优于0.3μm。最后对鱼眼眼轴参数进行测量,清晰得到鱼眼的角膜、晶状体和视网膜等结构。实验结果表明,该系统的稳定性及重复性均能达到设计要求,可以用于动物眼轴参数的测量。     

CFBG色散特性低相干干涉测量的误差分析

CFBG(Chirped Fiber Bragg Grating)是一种光纤无源器件,在光通信系统的色散补偿以及传感技术等方面具有广阔的应用前景,其色散特性对其推广应用具有至关重要的作用。本文介绍一种CFBG色散特性测量的光纤低相干干涉系统,并说明其测量原理。进行了相关的实测实验并对所采集的干涉图进行数据处理。实验表明该系统测量精度高,达到皮秒(群时延)量级,并且测量速度快。并对系统进行了误差分析。     

基于逆向蒙特卡洛法的溶液葡萄糖浓度低相干测量

提出了基于蒙特卡洛逆运算的葡萄糖含量低相干干涉测量方法,理论研究了葡萄糖含量与光学参数的相关性.通过正向蒙特卡洛数值模拟说明了从干涉曲线中同时求解散射系数和吸收系数的条件和可行性.以脂肪乳悬混溶液Intralipid作为实验对象,研究了糖浓度变化对深度相关干涉信号的影响.利用低相干干涉测量系统配合逆向蒙特卡洛计算提取了散射和吸收系数,进而通过散射和吸收系数的变化量间接获得了溶液葡萄糖含量.对实验结果与双积分球测量结果进行了比较验证,并对存在的系统误差进行了修正.实验结果显示,在加入修正值后,测量的散射和吸收系数的最大相对误差分别为2.52％和3.11％.研究结果表明,葡萄糖含量与散射系数和干涉曲线存在高度相关性,在非前向散射条件下,可以同时测量吸收和散射系数.经过校准后的测量结果满足了实际要求.     

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。     

基于低相干光干涉原理的眼轴测量研究

眼轴长度测量的精确度对近视防控及白内障患者术后视力恢复治疗等具有重要意义。本文介绍一种非接触光学测量技术,利用低相干光干涉原理研究相比传统测量及其他光学测量的新的系统,通过两路回光产生的干涉,达到无接触、精度更高的测量,达到20μm的误差,并进行模拟眼重复性测试,与现有IOL Master进行多组数据对比,验证其良好的准确性与精确度。     

光干涉法显微镜测量三维表面形貌研究

本文介绍了利用光干涉法显微镜测量三维表面形貌.利用计算机对在光干涉法显微镜下拍摄的零件表面轮廓条纹图象进行图象识别与处理,自动寻找条纹和计算,直接获得三维表面轮廓形貌.测量结果与触针式轮廓仪的测量结果进行了比较.     

圆锥量规锥度的高精度光学干涉法测量

针对超精密数控机床对圆锥量规锥度高精度测量的需求,研究了一种将\"大数\"和\"小数\"相结合,准确测量圆锥量规锥度的方法。介绍了锥度测量系统的基本原理及组成,给出了实验测量结果,分析了测量系统的不确定度。该测量方法利用最大分度间隔误差为0.10″的多齿分度台构成高准确度分度系统保证测量\"大数\"部分的准确性,采用激光偏振干涉装置及精密回转工作台组成小角度测量系统保证测量\"小数\"部分的精度,而双光束白光干涉系统实现了测量位置的精确定位。实验和分析结果表明,该方法在不确定度置信因子k为2时,锥度测量系统的扩展不确定度约为0.24″,优于0.3″,可实现圆锥量规任意锥度的高精度测量。     

干涉法表面形貌测量使用的扩展深度测量范围的方法

系统归纳了在干涉法表面形貌测量中使用的用来扩展深度测量范围的各种方法,分析了这些方法的原理、特性及性能指标,比较了这些方法的优越性。     

Photothermal microscopy: a step from thermal wave visualization to spatially localized thermal analysis

The calculation of photothermal response detected by a photothermal microscope is presented. By using a technique based on Green's functions and integral transforms, a model for laser‐induced temperature distribution functions has been derived. The mathematical method for solution of inverse problem is proposed. It suggests that photothermal microscopy, besides imaging subsurface of solids, has the potential for quantitative thermal analysis of varioussamples.     

润滑油膜光干涉测量系统与技术研究进展

光干涉是润滑油膜厚度测量中最广泛采用的手段,干涉图像的光强与色度学信息反映出接触区内部油膜的厚度与形状。概述光干涉技术在油膜测量领域的发展历程,介绍比色法、光谱分析法、相对光强法等3种典型的光干涉油膜测量方法和新发展的双色光光强调制测量方案。阐述润滑油膜测量光干涉测量系统的理论建模方法和系统设计的关键,并展望光干涉油膜测量系统的发展方向,如开发专用的光干涉油膜测量仪器,实现多光源的同步测量等。     

双孔载频剪切散斑干涉法测量表面动态形变

为了精确地测量物体表面的动态形变并得到形变高度和梯度信息,提出了一种基于双孔衍射结构的空间载频剪切散斑干涉法.该方法采用双孔产生固定的载频条纹,利用双旋转光楔实现剪切量的连续调节,采用正弦拟合算法进行相位计算.首先,分析了双孔调制的相位载频与双孔距和像距之间的关系,讨论了双旋转光楔得到线性剪切量调整的实验参数.然后,设计了测量光路参数;采用孔距为3.8 mm的双孔径配合焦距为80 mm的成像镜头在物距为300 mm时得到了载频为π/2的散斑场.最后,对动态形变的薄金属板进行了测量.实验结果表明:配合实时图像处理系统,该方法可以在帧率为15 frame/s的采集速度下实现动态形变的测量与显示,可测形变峰值为0.11～1.15 μm.本系统结构简单,易于集成,适用于动态形变的实时检测.     

Vacuum measurement using total-internal-reflection heterodyne interferometry

Based on the effect that the phase difference between s- and p-polarizations at the total-internal-reflection is changed with the variation of the air refractive index, which is related to the air pressure, a new optical method for measuring the air pressure of a vacuum cavity is proposed. From the experimental curve of the phase difference variation measured by the heterodyne interferometry and the calibrated pressure measurement of a vacuum cavity, an empirical formula is derived. With this empirical formula, the measurable range of this new optical method is 760 to 0.1 torr.     

A Wide Range Measuring System for Thin Lubricating Film: From Nano to Micro Thickness

This paper introduces a newly developed lubricating-film-thickness measuring system, which implements the multi-beam intensity-based (MBI) scheme proposed recently by the authors. Some details about the software of the testing system and instrumentation of the MBI approach are discussed. For efficient determination of the fringe order range of measured points, a simple counting strategy was suggested. It is shown that this measuring system can provide a measurement range from nano to micrometers and a high resolution on the nanometer level. Besides being able to detect ultra-thin lubricating film thickness, the system can also measure tiny local variations in film thickness on a nano-scale in the conventional EHL regime. The capability of the system is demonstrated by the determination of film thickness in the range of 1nm to 2.542m with a standard deviation of 0.89nm. In addition, some analyses are given for further understanding the optical EHL and the testing system in this paper.     

Multiplexing optical fiber low coherence and high coherence interferometric system with large range and high resolution for on-line measurement

A novel optical fiber sensing system multiplexing low coherence interferometry and high coherence interferometry that is endowed with large range and high resolution and is stabilized for on-line measurement is presented. An optical fiber Michelson interferometer performing measurement task in the system works in both modes of low coherence interferometry and high coherence interferometry simultaneously by employing a broadband light source and a fiber Bragg grating as an in-fiber reflective mirror. The amplitude of the measurand is determined by the low coherence interferometry while the value of the measurand is measured by the high coherence interferometry. Another optical fiber Michelson interferometer which is incorporated with the one performing measurement task stabilizes the sensing system for on-line measurement by exploiting an electronic feedback loop to reduce the influences that are resulted from environmental disturbances. The measurement range is 6 mm and the measurement uncertainty is less than 2 nm.     

A NEW ALGORITHM FOR ELIMINATING PHASE-SHIFT ERROR IN PHASE SHIFTING INTERFEROMETRY

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Novel two-frequency laser

The optics of a novel two-frequency laser is presented in this paper. The key components are a laser and a modulation unit consisting of acousto-optical modulators and Wollaston prisms. Different laser types can be used, covering a large wavelength range. The frequency difference is tunable. Use of the Wollaston prisms results in an efficient, compact, and stable unit with one optical axis. Its components are easy to align.     

Sub-micron position measurement and control on precision machine tools with laser interferometry

The trend towards tighter part tolerances from precision machine tools is placing increased demands on position transducers on these machines. Improved accuracy, repeatability and resolution from the position transducers is required to match this trend.This paper describes a new performance modelling technique for laser interferometer systems. Each error affecting the measurement accuracy and repeatability is described in detail, along with the method to determine these performance measures. Two products from Hewlett-Packard — wavelength tracking compensation and the high resolution interferometer — are also described that will help meet the future measurement requirements for precision machine tools.     

用于纳米测量的扫描X射线干涉技术

介绍扫描Ｘ射线干涉仪在当前纳米测量技术中的重要意义,阐述了该技术的基本原理,全面介绍了国外在该领域的研究现状,并对影响纳米测量的扫描Ｘ射线干涉技术的主要因素进行了分析。