超薄弹性层超声反射波频域测厚法

为了克服超声体积波测量方法只适用于测试厚度大于声波波长的弹性层的缺点,提出了频域相对传递函数法测量超薄弹性层的厚度的新方法.在推导超薄弹性层相对反射传递函数的基础上,用相对反射传递函数幅度谱、相位谱和复谱定征超薄弹性的厚度,分析了影响估计准确性的各种因素,研究了相对反射传递函数对厚度的灵敏度函数在误差传递中的意义.实验结果表明:相对传递函数法能够测量厚度为波长百分之一的铝薄层的厚度,相对误差小于2.5%,其中用幅度谱定征得到的结果最准确.这表明相对传递函数法可以有效地测量超薄弹性层的厚度,在实际应用中更加实用,其定征的准确性主要由相对传递函数对厚度灵敏度函数和测量误差共同决定.     

能量色散法在铁单晶应力测量中的应用

为了更精确地进行材料内部的应力测量，尝试了用能量色散法进行应力测量的模拟研究。模拟计算的结果分析表明：能量色散法进行应力测量的分辨率（3．9×10^-4）优于传统的应力测量方法的分辨率（101），并且在波长选定的情况下，狭缝的宽度与试样厚度是影响结果的主要因素。     

离子束溅射沉积Co膜光学特性的尺寸效应研究

本文采用离子束溅射沉积了不同厚度的Co膜,利用Lambda-900分光光度计,对不同厚度的Co膜从波长为310nm到1300nm范围测量了薄膜的反射率和透射率.选定波长为310、350、400、430、550、632、800、1200nm时对薄膜的反射率、透射率和吸收率随薄膜厚度变化的关系进行讨论.实验结果显示,Co膜的光学特性都有明显的尺寸效应.对在可见光范围内同一波长时的反射率和透射率随薄膜厚度变化关系的实验结果作于同一图上,发现反射率曲线与透射率曲线都有一个处在网状膜阶段的交点,这个交点对应的厚度作为特征厚度,该厚度可认为是金属薄膜生长从不连续膜进入连续膜的特征判据.     

分光光度计入射光质量对浓度测量的影响

分光光度计定量测量的基础是朗伯──比尔定律，即用公式表示为：－logI/I=kbc或A=kbc式中：I＿一定波长的平行单色光入射强度l——通过均匀、非散射、浓度和液层厚度一定的溶液后的透光强度A——溶液的吸光度ffe一吸光系数l：ry一液层厚度c一溶液的浓度当吸收他厚度保持不变，吸光度与浓度之间的关系应该是一条通过原点的直线。但在实际工作中，吸光度与浓度之间并非完全线性关系，产生测量正偏差或负偏差，如图1。图中：1．标准曲线；2．正偏差；3．负偏差。测量过程中，分光光度计产生误差的因素很多，如光电效应的非线性，电位计的非…     

用消光式椭圆偏振光谱测量薄膜光学参数的方法

本文主要介绍如何应用 TP—77型椭偏仪与 WDF 反射式单色仪组合,实现不同波长下的消光椭偏测量。此方法可测量薄膜厚度、折射率、吸收系数等光学参数。     

分光光度计波长误差的产生和控制方法

通过对影响分光光度计测量准确性的因素进行分析，认为波长准确度是其中的主要因素。对检定用波长标准进行特性研究，确定各种标准器的用途；对波长误差的构成原理进行分析，确定波长误差的调整方法；综合对检定波长产生误差的相关方面进行论述，全面提出了控制波长误差的具体方法，为控制影响分光光度计测量准确度的波长误差提出了一套解决方案。     

利用钠双线测量透明介质的厚度

本文为测量透明的介质片及介质膜的厚度,提供一个简易可行的办法,测量范围从1厘米至几十个波长。一、原理若用钠双线来照射迈克尔逊干涉仪,在视场中我们观察到干涉条纹的可见度将随着光程差增大(或减小),而发生“极大—极小—极大……”的周期性变化。这是因为条纹的宽度与波长成正比,不同波长照射光在干涉屏上所     

多波长测量技术

给出了3种多波长测量技术的应用实例，采用多波长二极管激光器干涉仪测量表面轮廓，3个二极管激光器分别发射780nm、823nm和825nm3种近红外光波，可以得到2个近似15μm和29μm的合成波长，激光二极管的注入电流用1MHz左右的3种不同频率调制，以获得干涉仪的相位调制，这3个干涉信号用1个光电检测器和锁相放大器检测，采用同样的干涉仪，仅用2种波长进行了圆度偏差测量，论述了相移干涉测量技术，其试件的长度表示为光源波长的倍数，如果只使用1种波长，则要求确切知道整数干涉级；而使用多种波长，如532nm、633nm和780nm时，可得到几个独立的长度，此时整数衍射级不同，可以通过“精确小数法”计算得到，PTB精密干涉仪长度测量不确定度很小，其单值性范围约0.6mm，因此其近似的长度估算足以满足超精密长度测量的要求。     

激光器全反射介质膜的制作原理与光学厚度测定

阐述了光学薄膜的镀制原理、反射率推算,阐述了镀制全反射介质薄膜过程中光学厚度的测定方法-极值法测量的原理和所用光线的波长,阐述了得到高反射率的条件,给出了测量膜厚的实验系统装置,并叙述了镀制17层全反射介质薄膜的过程和测量的方法,最后给出了17层全反射介质薄膜的反射率测量结果。     

基于摄像的结冰厚度测量方法的研究

本文主要讨论了基于摄像测量厚度的原理，提出了一种测量结冰厚度的方法，通过对摄像头和图像采集卡采集的结冰数字图像进行实时处理，提取边界来测量结冰层的厚度。文中对测量系统中的光学系统和结冰图像的数字处理过程步骤作了说明，并且给出了计算的结果。     

基于LIF海面溢油平坦厚油膜区域边缘厚度评估方法研究

油膜厚度是对海面溢油污染定量分析的一个重要指标。结合海面溢油平坦和非平坦两种厚油膜区域的形态特点,依据激光诱导荧光(LIF)技术探测不同厚度油膜的信号特征给出判定,提出平坦厚油膜区域边缘厚度评估方法,根据油膜区域边缘厚度的不同,采用荧光强度估算油膜厚度。实验观察平坦厚油膜边缘的厚度变化,利用LIF实验系统对平坦厚油膜的边缘厚度进行评估,结果表明,该方法对于厚度大于20μm的油膜厚度评估,相对偏差在±10%左右。     

大型水轮机组推力轴承油膜厚度在线监测研究

油膜厚度是反映推力轴承运行状态的重要参数,对油膜厚度进行实时在线监测有助于实现推力轴承的稳定运行。以某大型水轮机组推力轴承为例,结合其润滑流体的雷诺方程和油膜厚度方程,利用有限差分法分析了不同载荷和不同转速下推力轴承油膜厚度和压力分布的变化规律,并设计了一种油膜厚度实时在线监测方法。理论分析结果表明,当转速一定时,推力轴承油膜厚度先随着载荷的增大而增大,达到峰值后,随着载荷的增大而减小;当载荷一定时,油膜厚度随着转速的增大而增大。理论分析结果与该水轮机组推力轴承油膜厚度的在线监测数据完全吻合,验证了提出的油膜厚度在线监测方法的可靠性,为推力轴承运行状态的诊断提供了科学依据。     

Improvement of minimum paint film thickness for THz paint meters by multiple-regression analysis

We propose a numerical parameter fitting method to determine the time delay between two temporally overlapped echo pulses in terahertz (THz) tomography measurements. The method is based on multiple-regression analysis with the least-squares method and is applied to decrease the minimum paint film thickness for THz paint meters. Applying multiple-regression analysis to paint thickness measurements is five times more sensitive with regard to the minimum thickness than numerical Fourier deconvolution. We apply the proposed method to determine the optical thickness, geometrical thickness, and group refractive index of dry paint film and wet paint film. The proposed method is useful for decreasing the minimum thickness for a THz paint meter and other THz tomography measurements.     

振动冲击对海水润滑塑料轴承时变热弹流润滑的影响

建立了冲击载荷作用下综合考虑热效应和时变效应的海水润滑塑料轴承弹流润滑数学模型;利用压力求解的多重网格法,弹性变形的多重网格积分法及温度求解的逐列扫描技术数值模拟了连续冲击载荷作用下海水润滑膜压力及膜厚的分布;对比分析了正弦周期脉冲及三角形周期脉冲作用下的润滑膜中心压力、中心膜厚及最小膜厚随时间变化的特性;讨论了载荷幅值及脉宽对润滑膜特性的影响。数值计算结果表明,压力的变化周期同载荷的一致,膜厚的变化滞后于冲击载荷及压力的变化;随载荷幅值的增大,压力和膜厚的振幅增大,中心压力的对称线下移,相应膜厚的对称线上移;随脉宽的增大,中心压力的最大值变大,最小膜厚的最小值变小。     

一种基于波段比值法的海面厚油膜评估方法

激光诱导荧光(LIF)技术是目前较为有效的海面溢油探测技术之一,然而基于该技术的油膜厚度反演算法目前仅适用于薄油膜(≤20μm)。鉴于此,建立了一种基于LIF技术利用油膜荧光信号评估较厚油膜厚度的双波段比值模型,利用油膜荧光光谱的波形特性反演油膜厚度并论证了该算法的适用范围。实验数据得出,当油膜较薄时反演结果误差较大,随着油膜厚度增加误差逐渐降低,当油膜荧光信号趋于饱和时,误差较大且随油膜厚度的增加而快速变大。实验结果表明,该算法可以有效评估200~1400μm范围内的海面溢油油膜的厚度,并可以利用油膜荧光信号的测量相对误差评估该算法的适用范围。     

Calculation of film thickness for dip coated antireflective films

Antireflective films require an accurate film thickness to be able to perform optimally. The ideal thickness on most films is a quarter wavelength optical thickness (QWOT). The physical thickness of the QWOT film depends on the refractive index of the material that is being used. Each layer of the antireflective coating will have different optimal conditions for applying the film. When using the dip coating method, these conditions are withdrawal speed and concentration of solution.When using the currently accepted equations derived by Yang et al. to calculate the film thickness an error of 31.7% was noted when compared with the experimentally measured film thickness. Realising that the refractive index of the film plays a role in determining the thickness of the film, the equations were modified to take refractive index into account. Once this was taken into account, the calculated film thickness deviated from the measured film thickness by 8.7%. This error can be attributed to experimental errors which involve temperature and concentration fluctuations.     

Method for measuring thickness of dielectric films using microdielectric fringe-effect sensors

A method for noninvasive thickness measurements of dielectric films using fringe-effect (FE) sensors is developed and experimentally validated. The fringing electrical field, created by electrodes microfabricated at the film substrate, depends on the film thickness and dielectric permittivity of the film under test (FUT). The unknown film thickness is estimated by matching the theoretical prediction of thickness-dependent sensor admittance with the measured value. In the case of FE sensors with spatially periodic, interdigitated electrode (IDE) configuration, the admittance prediction is simplified, which allows for the real-time measurements of changing thickness. The developed method can be used to continuously measure the changing dielectric permittivity of the FUT material, which makes it possible to determine the thickness of films of changing dielectric properties, caused by chemical or other transformations. The application of the developed method is demonstrated experimentally by measuring the thickness of silicon nitride film deposited in several increments on the quartz substrate of the IDE sensor. In the expected range of sensor sensitivity, the results show an excellent agreement with the independent thickness measurements.     

低阈值的聚合物分散液晶膜厚对其电光性能的影响

采用聚合物诱导相分离方法制备PDLC膜,主要研究了膜厚对PDLC膜电光特性的影响。结果表明,膜厚对PDLC中液晶微滴的尺寸与形状有很大影响,在一定范围内随着膜厚的增加,液晶微滴变得细小均匀,进而使液晶的阈值电压及饱和电压增加,但同时使液晶的下降时间缩短,有助于提高响应速度。     

Fracture-induced formation of semi-concentric patterns on polymeric films

Using the linear perturbation method, the effect of radial residual-compressive surface stress on the surface evolution of a solid film was analyzed. The result showed that the radial-compressive surface stress can cause the formation of concentric surface waviness on the surface of the film. An analytical relationship was established between the apparent surface stress, the spatial wavelength, and the film thickness. Using a concentrated-loading method, a complementary set of semi-concentric surface ripples was formed on the fracture surfaces of a polymer film which was sandwiched between two glass slides. The amplitude of the semi-concentric ripples first increased with increasing the film thickness and then became independent of the film thickness for the film thickness ranging from 491 nm to 636 nm. Using the derived relationship and the experimental data, the variation of the apparent surface stress with the film thickness was calculated. The magnitude of the apparent surface stress increased with increasing the film thickness.     

Dimensional control of brittle nanoplatelets. A statistical analysis of a thin film cracking approach

Nanoparticles are essential building blocks for nanotechnology. In this paper we demonstrate a novel method to create nanoplatelets by thin film cracking. The thickness of the resulting platelets is determined by the film thickness, and their aspect ratio is controlled by the total strain and the elastic mismatch between substrate and thin film. Platelets can be created from any brittle film independently of microstructure and materials class. The feasibility of this method is substantiated by a statistical analysis of the fracture process.