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.     

基于狭缝光阑的剪切散斑干涉动态测量

为了精确、实时地测量物体表面的动态形变,提出了基于狭缝光阑的空间载波剪切散斑干涉系统。该系统通过倾斜迈克尔逊干涉仪的一个平面镜来产生剪切量和载波频率,实现空间频谱的移动;采用一个可调节的狭缝光阑控制散斑大小和空间频谱宽度。基于傅里叶变换与反变换在空间频率域上提取所需的频谱并计算相位图,最后通过一幅干涉条纹图得到相位分布信息。采用该系统对一个中心加载、四周固支的薄铝板进行了动态测量,分析了光学系统参数对测量结果的影响。结果表明,采用像素尺寸为4.65μm×4.65μm的高分辨率相机,焦距为8mm的成像镜头,设置剪切量为25mm,狭缝光阑X方向的尺寸为1mm时,可得到高质量的剪切散斑相位图。该方法可以在25frame/s的采集速度下,以43.6°的视场角实现动态形变的测量,可测形变峰值为0.5~30μm。     

数字散斑干涉图像拼接方法研究

散斑干涉测量系统的视场大小和量程受成像器件尺寸的限制.为了扩大视场和形变测量范围,对散斑干涉形变测量的图像拼接方法展开深入研究.搭建了双CCD散斑干涉测量光路,通过对两个CCD获取的散斑干涉图的拼接实现大视场形变测量.对互相关、差方和和互信息法以及归一化改进的配准算法进行了研究,并分析了重叠面积的影响.结果表明,互相关...     

宽谱段、动态局部高分辨离轴主动反射变焦系统

为了实现无遮拦、宽谱段、动态的局部高分辨成像,设计了一种局部高分辨率的离轴主动反射变焦系统。该系统将离轴主动反射式变焦理论和局部动态高分辨率成像理论相结合,实现了宽谱段范围内不同焦距处的动态局部高分辨成像。采用曲率半径可变的变形镜实现变焦,避免了传统机械变焦中复杂的机械运动控制,减轻了系统体积和重量并有效地保证了系统的宽谱段和大视场;通过对变形镜面形的控制,在不同焦距处实现了全视场内任意感兴趣区域的局部高分辨成像,降低了数据传输量;而采用无色差的反射式系统则克服了传统透射式及折反射式系统只能实现单色局部高分辨成像的缺点。经过优化设计,系统在可见光范围内成像,焦距f′为75 mm(视场角FOV为x:0°~0.5°,y:3°~10°)~150mm(FOV为x:0°~0.5°,y:1.7°~5°),F/#为7~14。理论和仿真分析表明,系统在各焦距处感兴趣区域内的成像质量均可达到衍射极限,实现了全视场内任意区域动态局部高分辨的成像效果。     

双波段/双视场全景航空相机光学系统设计

为提高航空相机识别目标能力,设计了一种应用于全景式航空侦查相机的可见光/红外双视场成像光学系统,可见光光学系统焦距为200 mm/400 mm,相对孔径为1∶8.8,视场角为9.4°×7°/4.7°×3.5°。红外光学系统焦距为117 mm/234 mm,相对孔径为1∶4,视场角为9.4°×7.5°/4.7°×3.76°。该光学系统利用物像交换原则采用轴向移动变倍方式,设计结果表明,光学系统成像质量接近衍射极限,可以满足实际使用需求。     

剪切散斑干涉术中剪切量的测量

由于采用剪切散斑干涉术测量离面应变和面内应变都与剪切量有关,所以剪切量的测量精度决定了应变场分布测量的准确性.本文论述了公式法、成像法、莫尔条纹法和相关法等4种剪切量测量法的测量原理,定性分析了它们的测量范围.搭建了一套剪切量测量系统,利用成像法、莫尔条纹法、相关法测量剪切散斑系统的剪切量,并以公式法计算的结果为准,比较其他3种方法的测量结果.结果表明:剪切量＞3 mm时,利用相关法测量具有较高的测量精度;剪切量＜3 mm时,奠尔条纹法测量效果会更好.因此,实际应用中,应该先根据实际测量条件估算剪切量的大致范围,然后依据估算范围选择合适的测量方法.     

用于位相缺陷检测的反射式剪切点衍射干涉仪

为了实现光学元件位相缺陷的大视场、高分辨率、瞬态检测,设计了一种基于无镜成像算法的反射式剪切点衍射干涉仪。该干涉仪通过在参考光与测试光之间引入横向错位量,形成高密度线性载频,利用快速傅里叶变换算法从单幅干涉图中提取待测波面信息,实现缺陷的瞬态测量。利用无镜成像算法抑制了缺陷的衍射效应,总结了有效的缺陷类型辨别方法。实验检测了强激光系统中的一块光学平晶,验证了所提缺陷类型判据的正确性。此外,采用反射式剪切点衍射干涉仪对一块激光毁伤的光学平板进行检测,测试结果与Veeco NT9100白光干涉仪测量结果相比,相对误差为2.1%。结果表明,该干涉仪能够有效应用于检测大口径光学元件的位相缺陷。     

混频对全视场外差动态干涉仪测量精度的影响

全视场外差动态干涉仪在面形测量方面具有测量精度高、抗干扰能力强等优点,适合用于长焦距面形的动态干涉测量以及大口径光学元件的测量。但是干涉仪系统内部光学元件性能不理想以及元件装配存在误差等,会在干涉光路中引入频率混叠,影响干涉仪的测量精度。为了分析混频对全视场外差动态干涉仪测量精度的影响,从混频产生的原因出发,建立了由混频引入的测量误差的理论模型,分析了混频程度对测量精度的影响,分析结果表明,测量误差与混频程度呈非线性正相关,混频会造成测量面形结果上叠加一个和干涉条纹相同频率的周期性误差。搭建了全视场外差动态干涉测量实验系统,验证了不同混频程度对面形测量精度的影响,当混频程度为0.029时,面形测量误差为0.053λ;当混频程度为0.120时,面形测量误差为0.110λ,与仿真分析结果吻合。本文的研究对研制高精度全视场外差动态干涉仪具有实际意义。     

分孔径三视场中波红外光学系统

为了克服单一光学通道长焦距与大视场之间的矛盾,设计了一款分孔径大变倍比三视场中波红外光学系统。该光学系统采用分孔径技术,包括小视场光学通道和中视场/大视场光学通道,两个通道之间的转换通过切出切入45°放置的反射镜完成,小视场光学通道采用二次成像,仅采用6片透镜,透过率高;中视场/大视场光学通道采用三次成像;小视场光学通道与中视场/大视场光学通道共用一片反射镜和中继组,实现了共出瞳分入瞳——分孔径;小视场长焦距为1 120mm,大视场短焦距为22.58mm,变倍比达到53×;对小视场光学通道进行了三次立体折叠,对中/大视场光学通道进行了一次折叠,有效地对横向和纵向尺寸进行了控制,外形包络在270mm×217mm×258mm范围内,系统紧凑,实现了兼具长焦距和大视场的三视场中波红外光学系统。设计及实验结果表明该光学系统像质良好,满足热像仪使用要求。     

纳米磁微粒的双扫描干涉激光散斑实验

设计了研究纳米尺度磁微粒簇运动的双扫描干涉激光散斑实验。采用干涉条纹作为散斑运动的标度测量了磁流体中磁微粒的运动,避免了用传统数字散斑相干方法计算量大、精度依赖亚像素搜索算法的缺点;利用位相延迟扫描补偿横向扫描附加位相带来的干涉条纹变动,提高了动态散斑测量的空间分辨能力。对尺度为30～100nm的磁微粒簇运动进行了实验分析,结果表明,受磁流体磁场变化的非线性、微粒间的碰撞和聚集等复杂因素的影响,磁微粒簇是以湍流,非匀速方式运动的,其运动的平均速度为6.93mm/s。另外,该方法可通过改变条纹间距方便地调节精度以满足不同的测量要求。     

Investigation and compensation of the nonlinearity of heterodyne interferometers

The nonlinearity of heterodyne interferometers is mainly influenced by the nonorthogonality and ellipticity of the linearly polarized partial beams of the laser and by the limited extinction capability of the polarizing beam splitters. The phase errors at the interferometer output can be detected by measuring the phase difference between the two orthogonal directions in the output beam. This arrangement can be used to check an interferometer setup for causes of nonlinearity and to eliminate them by adjustment, replacement, etc. The arithmetical mean value of the phases of the two orthogonal output signals is linear, except for a residual error. These detection and compensation capabilities of the proposed phase measurement arrangement are demonstrated by experimental investigations.     

Correction of Errors in Polarization Based Dynamic Phase Shifting Interferometers

Polarization based interferometers for single snap-shot measurements allow single frame, quantitative phase acquisition for vibration insensitive measurements of optical surfaces. Application of these polarization based phase sensors requires the test and reference beams of the interferometer to be orthogonally polarized. As with all polarization based interferometers, these systems can suffer from phase dependent errors resulting from systematic polarization aberrations. This type of measurement error presents a particular challenge because it varies in magnitude both spatially and temporally between each measurement. In this article, a general discussion of phase calculation error is presented. We then present an algorithm that is capable of mitigating phase-dependent measurement errors on-the-fly. The algorithm implementation is non-iterative providing sensor frame rate limited phase calculations. Finally, results are presented for both a high numerical aperture system, where the residual error is reduced to the shot noise limit, and a system with significant birefringence in the test arm.     

System for automatic gauge block length measurement optimized for secondary length metrology

This paper presents a contactless system for automatic gauge blocks calibration based on combination of laser interferometry and low-coherence interferometry. In the presented system, the contactless measurement of the absolute gauge block length is done as a single-step operation without any change in optical setup during the measurement. The optical setup is combined with compact gauge block changer with a capacity of 126-ga blocks, which makes the resulting system fully automatic.The paper also presents in detail a set of optimization steps which have been done in order to transform the original experimental setup into the automatic system which meets secondary length metrology requirements. To prove the measurement traceability, we conducted a set of gauge block length measurement comparing data from the optimized system and the established reference systems TESA NPL A.G.I. 300 and TESA–UPC operated in Czech Metrology Institute Laboratory.     

Theoretical Study on the Interferometry of Thin EHL Film Measurement

Interferometry has been widely utilized in elastohydrodynamic lubrication (EHL) film measurement since the 1960s. In-depth optical analyses are required to get more fundamentals of optical EHL film tests. In this paper, a stratified-layer model of optical EHL contact is numerically analyzed by the multi-beam interference approach. It is revealed that the high reflectance of the beam-splitter and the steel interface generate a deviation of the intensity profile from the two-beam interference. Previous experimental results about fringe contrast are reproduced, and the determination of the beam-splitter layer is theoretically clarified. Furthermore, some characteristics of spectrometry for ultra-thin film measurement are studied, and the dependence of the interference spectrum on the spacer layer thickness is displayed. The measurement simulation has theoretically confirmed the constant initial phase change assumed in practical measurement. It is theoretically demonstrated that in the spectrometry approach, TiO₂ layer can generate spectrum with high finesse and may be used in the future application. The theoretical results in this paper are correlated with previous experimental practices, and the optical EHL technique can therefore be much better theoretically understood.     

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。     

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.     

On a novel approach to evaluate Schlieren interferograms of axisymmetric refractive index fields

In Schlieren interferometry one often encounters axisymmetric refractive index fields which principally violate the general assumption of interferometry, namely the two-dimensionality of the phase object. However, there exist numerical methods capable to evaluate axisymmetric refractive index fields using the fringe distribution of interferograms. This paper describes a novel approach for evaluating Schlieren interferograms of axisymmetric refractive index fields. The suggested algorithm exhibits higher accuracy without constrains for large beam separation (where the interferometer sensitivity is higher) when compared to methods given in the literature. The computational performance has been controlled and compared by using analytical test functions.     

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.     

相位偏移干涉测量波面的一种新算法

本文分析了利用相位依稀干涉的相位计算方法对测量结果准确程度的影响,提出了一种利用相位偏移干涉原理测量波面的新算法（四幅改进算法）。考虑到移相误差是导致相位偏移干涉测量法产生误差的主要因素,本文着重讨论相位偏移干涉测量算法对移相误差的敏感程度。根据对实验测试机构所进行的测量与分析,以实际的数据为基础得出在相位人多干涉测量算法对移相误差的敏感程度,根据实验测试机构所进行的测量与分析,以实际的数据为基础得出在相位偏移干涉测量中新算法的优秀品质。该新算法对移相误差有良好的抑制作用,无论是理论分析速 是实际测量效果都很好。