光学三维测量技术与应用

光学三维测量技术是一种可视化的测量技术,能完成复杂形体的点、面、形的三维测量,能实现非接触测量,在制造业和航空航天领域得到广泛应用。航空三维激光扫描与摄影测量技术利用激光测距原理和航空摄影测量原理,与基于全球定位系统(GPS)和惯性测量装置(IMU)的机载定位定向系统(POS)联接,可以快速获取大面积地球表面三维数据。本文对光学三维测量技术和航空三维激光扫描技术做一简单介绍,给出三维激光扫描技术在航空航天领域的几个应用。     

光学方法测量三维形状综述

本文首先对采用各种光学方法进行三维形状测量给以综述。然后我们集中阐明结构光学技术，其中包括各种光学配置，图像捕获技术，数据处理、分析方法和优缺点。文中列举了若干工业应用实例，还讨论了需要进一步研究开发的重要领域。最后提供的是有关三维形状测量的文献目录，尽管它并不很详尽。     

数字全息术用于光学元件表面缺陷形貌测量

利用像面数字全息显微术对光学元件表面缺陷的三维形貌测量进行了理论及实验研究。设计并搭建了相应光路系统记录全息图,采用角谱算法数值重建物光场,通过相位修正消除了系统误差引入的波前畸变,获得了经过待测光学元件表面缺陷调制的物光相位分布,并根据建立的相位分布与表面缺陷面形的关系模型计算得到缺陷三维形貌。实验以多个划痕和麻点等常见表面缺陷作为测量对象,分别获得了它们的三维形貌,以其中一条实际宽度为35μm、深度为270nm的划痕为例,测量得到该划痕的宽度为35.21μm,平均深度为267.6nm,与真实值相比,横向测量误差为0.6%,纵向测量误差为0.9%。实验结果证实该测量方法是有效、可靠的,能够准确测量光学元件表面缺陷的三维形貌,因而有助于判断光学元件损伤程度以及分析缺陷对系统波前的影响,对保障高功率激光装置的安全正常运行有重要意义。     

三维表面形貌的逾渗特性表征

为了建立表面形貌微观结构与其功能特性之间的关系,基于逾渗理论建立了表面形貌的逾渗模型,用逾渗概率、空体集团平均大小和空体集团分布系数对三维表面形貌的逾渗特性进行了量化表征。采用数字滤波技术生成具有给定自相关函数和纹理取向的数字化粗糙表面,分析了具有相同均方根粗糙度而结构不同的三维表面形貌的逾渗特性,给出了表面纹理方向参数和自相关长度对表面逾渗特性的影响,并借助部分三维形貌参数(ISO25178)建立了表面形貌与逾渗特性参数间的量化关系。结果表明:对于各向异性表面,沿横向搜索跨越空体集团,表面逾渗发生时的表面高度、逾渗阈值和逾渗体积均随着表面纹理方向参数的增大呈减小趋势,而空体集团分布系数呈增大趋势;沿纵向搜索时,其变化规律与横向相反。对于各向同性表面,逾渗发生时的表面高度和逾渗阈值随着表面自相关长度的增大呈先减小后小幅增大趋势,而逾渗体积和空体集团平均大小呈逐渐减小趋势。研究结果为面向功能的表面形貌设计提供了理论基础。     

汽车模具光学三维在线测量检测系统

西安交通大学和天津汽车模具股份有限公司联合推出中国第一个自主研发的,包括近景工业三维摄影测量系统、面扫描系统、变形测量分析系统等的汽车模具光学三维在线测量检测系统。该系统已经应用在天津汽车模具股份有限公司的设计、生产、测试等环节。     

计算机微视觉的三维显微测试及构形系统的研究

微结构三维显微测量是研究微加工工艺和微尺度结构特性的主要测试手段.一种基于计算机微视觉的方法被提出用来对三维微结构进行显微测量.对微结构测试及构形系统的基本原理进行了研究,构建了微结构测试及构形系统的硬件和软件平台.从而实现了在光学显微镜下对微结构的三维观测[0].通过运用微结构测试及构形系统的硬件平台实现了对微结构高分辨率的观察测量、三维精确运动控制以及水平与竖直方向的精确制动.通过软件平台完成了对微结构的三维重构.课题利用微结构测试及构形系统对微结构进行了测试及重构.通过实验,证明了理论研究和系统的可行性,该研究在微结构的测试方面具有较大的理论意义和实用价值.     

变间隔法实现三维形貌测量

随着生产的发展,对许多工件提出了测量三维形貌的要求。本文提出了在较大光点间隔下实现小采样间隔三维形貌测量的方法。该方法可不改变测量系统光学结构,通过外加简单的装置改变光点间隔,从而实现小采样间隔的三维形貌测量。论文给出了相应的数学模型、测量步骤,并进行了误差分析。     

用于表面微观形貌测量的光学方法

介绍了在表面微观形貌测量中常用的光学测量方法,分析了它们各自的原理和优缺点,并对光学法表面微观形貌测量技术的发展作了简要评述。     

三维信息测量技术研究

将测量技术分为接触式和非接触式两大类,先介绍了接触式测量中的三坐标测量机的相关技术,再介绍了非接触式测量中光学和非光学测量所包含的几种主流的三维测量方法的原理,重点讨论了非接触式测量中光学测量方面的几种测量技术。     

Calibration of focusing steps and image rotation of electron microscopes

Reflection electron microscopy (REM) is used to calibrate the focusing steps and rotation of electron microscopes. The calibration of focusing steps is done by the direct measurement of the shift on in-focus positions in the REM micrographs. Rotations between the diffraction patterns and images are calibrated in the usual way. By using the REM geometry, the reflection high energy electron diffraction (RHEED) patterns and REM images have no rotation symmetry, thus eliminating the 180° uncertainty.     

Effects of mathematical models and algorithms on quantitative characterization of areal step height with optical and stylus profilometers

Step height characterization is essential for the quality control of various functional components, such as graphene and the step features of semiconductor devices. Two methods are proposed to characterize the areal step heights. The first method extends the two-dimensional characterization in the ISO specification into a three-dimensional one by extracting multiple parallel profiles. The second method calculates the step heights by projecting from the measurement points to the normal vector at the surface centroid. Mathematical models and algorithms of the two methods are introduced and validated by synthetic data. Experiments are conducted by comparing the assessment results of the two methods and of a method proposed in a previous research. The calibrated values of the standards are utilized for validation. The characterization results may differ notably or slightly, depending on the properties of the data and the algorithm.     

Performance of visible and mid-infrared scattering-type near-field optical microscopes

We describe the principles of two scattering‐type near‐field optical microscopes (s‐SNOMs), one operating at 633 nm wavelength, the other at selectable wavelengths in the range 7.3–11.3 µm, and compare the measurement experience. Both use interferometric detection of scattered radiation, and are therefore capable of amplitude and phase‐contrast imaging. In this study both instruments use the same or even identical commercial probe tips, and measure a single, three‐component, test sample. Our results show that the imaging process of s‐SNOM is wavelength‐independent, namely, that the resolution is determined by the properties of the tip only, and that the contrast is given by the complex refractive index of the sample, predictable from a simple, analytical model of tip–sample interaction. A novel, ‘edge‐darkening’ artefact is described which may appear in s‐SNOM and that is wavelength‐independent.     

Imaging properties of high aperture multiphoton fluorescence scanning optical microscopes

A theory for multiphoton fluorescence imaging in high aperture scanning optical microscopes employing finite sized detectors is presented. The effect of polarisation of the fluorescent emission on the imaging properties of such microscopes is investigated. The lateral and axial resolutions are calculated for one-, two- and three-photon excitation of p-quaterphenyl for high and low aperture optical systems. Significant improvement in lateral resolution is found to be achieved by employing a confocal pinhole. This improvement increases with the order of the multiphoton process. Simultaneously, it is found that, when the size of the pinhole is reduced to achieve the best possible resolution, the signal-to-noise ratio is not degraded by more than 30%. The degree of optical sectioning achieved is found to improve dramatically with the use of confocal detection. For two- and three-photon excitation axial full width half-maximum improvement of 30% is predicted.     

面向航天快速发射的光学载荷设计与制造

为系统地介绍面向航天快速发射的微纳卫星光学载荷设计与制造过程,从光学原理设计出发,以折反式光学相机为研究对象,主要介绍光学元件的结构设计、力学分析、加工及检测过程,最终得到500 km对地极限分辨率为3.1m的光学载荷.研制结果表明,通过合理的光机结构设计,并选取单点金刚石车削、磁流变修形以及计算机控制光学表面成形加工...     

Analysis of multiscale measurements of porous microstructures based on 3D optical microscopes

In this article, a multiscale measurement strategy is introduced to analyze porous microstructures and the main influences on the measurement accuracy of 3D optical microscopes are investigated. The purpose is to explore the fundamental relationship between resolution, magnification and imaging in optical systems derived from using different optical lenses and their impacts on the characterization of porous microstructures. A confocal laser scanning microscope with different lenses is used for the data acquisition. Afterwards, a post-processing for data combined with image processing is carried out to analyze the geometry differences of identical pores. The results show that the numerical aperture is the primary factor causing measurement differences of the same micro object rather than the magnification of a lens and the calibrated image pixel resolution. Moreover, the assessed geometry differences strongly depend on the size or the scale of the microstructures. This phenomenon can be treated as a good verification example for the classic Abbe-theory.     

High-accuracy displacement metrology and control using a dual Fabry-Perot cavity with an optical frequency comb generator

A displacement metrology and control system using an optical frequency comb generator and a dual Fabry-Perot cavity is developed with sub-nm accuracy. The optical frequency comb generator has expanded the displacement measurement range and the dual cavity system has suppressed the environmental fluctuation. We evaluated the absolute uncertainty of the developed displacement measurement system to be approximately 190 pm for the displacement of 14 μm and the accurate displacement control using a phase-locked loop was demonstrated with a resolution of approximately 24 pm.     

Axial resolution of confocal microscopes with parallel-beam detection

We present a simple theory for the evaluation of the axial resolution of a confocal scanning microscope with parallel-beam detection. The results demonstrate that, in certain cases, the collection efficiency is low compared with a conventional confocal microscope, but the axial resolution may be further improved.     

The theory of scanning microscopes with Gaussian pupil functions

The theory of imaging in scanning microscopes with lenses, source and detector all having Gaussian pupil function is developed. This assumption is useful as the expressions may be evaluated analytically. It is shown that Type 2 microscopes exhibit superior performance to those of Type 1. Effects of defocus are considered. It is found that defocus can be used in a Type 2 microscope to observe phase information without the limitation in resolution associated with stopping down the collector of a conventional microscope. It is also found that a Type 2 microscope discriminates against light scattered by parts of the object outside of the focal plane, allowing observation of detail within a thick object.     

Analysis of the measured signals in apertureless near-field optical microscopy

We present an analytical model able to explain the optical signal recorded during our experimental approach curves in the infrared at a wavelength lambda=10.6 microm, with a home-made apertureless near-field scanning optical microscope ANSOM. This model uses classical electrodynamics to calculate the scattering cross section of the oscillating tip, considered as a dipole, and its dielectric image in the sample as a function of the tip-sample separation from the near-field to the far-field regime. The dipoles are placed in a non-uniform electric field because of the standing wave arising from the interference between the incident and the specular laser beams. We also added a background field coming from a scatterer on the surface in order to account for zeroing of the optical signal for particular tip-sample separation and interference patterns.