基于条纹反射的镜面测量及三维重建算法分析

本文详细介绍了依据条纹反射术测量镜面、类镜面的原理和方法,分析了经由梯度数据重建三维面形的主要算法和关键问题。通过计算机模拟和波面实际测量,对十字路径积分法、傅里叶变换积分法和区域波前重构法三种主要算法的重建精度进行了对比研究。研究表明:区域波前重构法不但对高频噪声有较强的抑制作用,同时也可以处理复杂的连通区域和非等间距分布梯度数据的复杂情况,因此更适用于基于条纹反射术的波面测量。

基于开源硬件的便携式镜面测量实验

在光电专业的教学过程中,光学检测实验是一项非常重要的内容。传统的教学方式多依托专门的光学设备或仪器开展相关实验教学,虽然能够在一定程度上锻炼学生的实际动手能力,但存在诸如实验场地受限、实验设备软硬件昂贵、学科专业知识交叉不足等缺陷。为了克服上述问题,本文以光学检测中的镜面测量为例,根据相位偏折术(Phase Measuring Deflectometry,PMD)基本原理,以树莓派开发板为平台核心、Python语言为编程工具,结合机械制图和3D打印技术,设计并构建了一套基于开源硬件的便携式镜面测量装置。该实验装置具有低成本、小型化、不受场地限制等优点,相关实验内容涵盖几何光学、计算机视觉、软件编程、机械制图设计等专业知识,对于大学生综合实验素质与能力、特别是创新型实验能力的提升具有积极的促进作用。

镜面物体三维测量系统中两显示屏的平行正对校正

针对镜面物体三维测量系统中两显示屏无法精确平行正对的问题,提出了一种在镜面物体三维测量系统中通过软件产生变形条纹等效两显示屏精确平行正对的方法。该方法首先采用机器视觉技术标定两显示屏的外参。然后基于所标定的外参,利用软件编程产生等效两显示屏平行正对的变形条纹,变形条纹通过半透半反镜后所成的像在相机坐标系内呈现前后精确平行正对的关系。最后,利用对应两个显示屏上的变形条纹计算相应位置相位的差值,并通过均方根误差定量评定所提出的方法。实验结果表明,所提出的方法能将水平方向的均方根误差缩减为原来的24.21%,竖直方向的均方根误差缩减为原来的8.15%,从而提高三维测量系统的精度。

大型镜面大误差范围相位恢复在位测量研究

研究了一种基于相位恢复技术的新型镜面测量方法,用于测量大型光学镜面研抛加工过程中较高较陡的面形误差,为光学镜面加工中误差收敛的过渡阶段提供可靠的定量在位测量方法。文中构建了基于离焦光场的相位恢复测量系统并设计适用于大误差检测的相位恢复算法。分析了各种误差因素以及系统测量精度以及测量范围。对一面口径150mm球面反射镜进行了在位测量实验。相位恢复测量与干涉测量结果一致。理论分析和实验都表明该方法切实可行,检测范围和相对精度满足加工要求,具有良好的应用前景。

条纹反射法测量三维面形中的积分算法

基于不同梯度数据噪声,研究讨论了几种典型的梯度积分算法,并提出了一种改进的Southwell全局积分算法.以重建面形和原始面形的相似度、均方根误差作为算法性能参数,对梯度数据进行模拟测试.搭建条纹反射实验平台,对标准凹球面反射镜进行积分重建,并将条纹反射法测量结果和实际元件参数进行对比.实验结果表明:用改进的Southwell算法重建的凹球面的半径误差为0.09%,结构相似度大于0.999,其重建速度为原算法的1.2倍.改进后的Southwell算法相较于传统的积分算法,获得了更高的重建质量和重建效率,满足镜面物体测量的非接触、精度高、稳定性强等要求.

大镜面在位检测中的相位恢复技术研究

为了满足大型光学镜面加工对在位检测的需求,探索了一种应用相位恢复技术的新型镜面测量方法.构建了基于离焦光场的相位恢复测量系统并实现了与此系统相适应的相位恢复算法,此测量系统结构简单且不易受环境振动影响.在此系统基础上,详细分析了各种误差因素以及系统测量准确度和测量范围,并针对在位检测的特点和要求,研究了此方法在应用中的可靠性.对一面口径430mm的球面反射镜进行了分平台在位测量实验.实验中分析了不同测量参量对测量结果的影响.相位恢复测量与干涉测量结果对比较为吻合.理论分析和实验都表明该方法切实可行,检测准确度满足光学镜面研抛加工要求.

基于平面镜的相机-显示器快速标定方法

针对基于计算视觉的镜面物体测量中相机和显示器的位置参数标定问题,提出了一种基于平面镜的快速标定方法。该方法使用显示器投射标定模板直接作为标定物,由相机通过平面镜的反射获得标定模板的图像,然后进行相机标定,可同时获得相机的内部参数及标定模板虚像在相机坐标系下的位置参数,最后根据平面镜成像的原理计算标定模板即显示器的实际位置。在标定过程中,平面镜可自由移动,而无需知道平面镜的具体位置参数。实验结果表明,该方法简单快速,同时具有较高的标定精度,满足实际测量需求。

光学镜面间隔测量中的色散研究

材料的色散会影响镜面间隔的测量精度,为了提高光学干涉法测量镜面间隔的精度,对材料色散效应进行理论分析和数值仿真,分别对LAK9、ZF6、H-ZF2、BAK7、K9光学玻璃进行仿真测试,得到了干涉信号峰值偏移量关系式,信号峰值偏移量与材料的一阶色散系数成正比。为了验证该关系式的正确性,搭建了一个镜面间隔测量实验平台,实验测量得到的干涉信号最大值偏移量与仿真测试结果的相对误差小于2%,考虑到实验过程中的误差因素,证明仿真测试得到的结果是正确的。

Determination of efficient superfinishing conditions for mirror surface finishing of titanium

To determine mirror surface finishing conditions and efficient and economical superfinishing conditions for pure titanium and titanium alloys, an abrasive film is used when superfinishing is performed under varying conditions. These conditions include the workpiece rotation speed, the oscillation speed, the contact pressure of the roller, the hardness of the roller, and the type of abrasive film. The superfinishing device is applied to polishing a thin and long cylindrical bar. A micro-finishing film and a lapping film were used as abrasive films. A1203 grains or SiC grains were used as abrasives. The surface roughness of a polished workpiece was measured using a stylus-type surface-roughness measuring instrument. As a result, the conditions to improve the polishing surface efficiently include high values for the workpiece rotation speed, oscillation speed and contact pressure. The roller hardness has no effect on the efficient polishing conditions. The mirror finish of a surface can be created using lapping film of 3 μm with Al2O3 grains after polishing to a steady surface roughness under the efficient polishing conditions.

A shaped annular beam tri-heterodyne confocal microscope with good anti-environmental interference capability

annular beam tri-heterodyne confocal microscope has been proposed to improve the anti-environmental interference capability and the resolution of a eonfoeal microscope. It simultaneously detects far-, on-, and near-focus signals with given phase differences by dividing the measured light path of the eonfoeal microscope into three sub-paths （signals）. Pair-wise real-time heterodyne subtraction of the three signals is used to improve the anti-environmental interference capability, axial resolution, and linearity; and a shaped annular beam super-resolution technique is used to improve lateral resolution. Theoretical analyses and preliminary experiments indicate that an axial resolution of about 1 nm can be achieved with a shaped annular beam tri-heterodyne confoeal microscope and its lateral resolution can be better than 0.2 um for A = 632.8 nm, the numerical aperture of the lens of the microscope is NA = 0.85, and the normalized radius e = 0.5.

A Flexible Calibration Method of Laser Light-Sectioning System for Online 3D Measurement

A flexible calibration method based on a front-coated flat mirror is proposed for a laser light-sectioning three-dimensional(3D)measurement system. Since the calibration target and its mirror image are spatially separated and can be recorded in an image by a camera,the proposed method requires only a single composite image that contains a non-planar checkerboard pattern,a laser strip projected on the target and their mirror images to complete the calibration of the camera and the laser plane in one step. Levenberg-Marquardt(LM)algorithm is used to optimize the system parameters,and the measurement accuracy and speed are improved to enable online 3D inspection. Static and dynamic online 3D measurements are carried out on a cup and a triple stepped shaft,respectively,to validate the proposed method. The shaft has two steps with the depth of(0.5±0.01)mm and(2±0.01)mm to be measured online when the shaft is rotated and translated at the same time. The measurement results can be output at a frequency of 7 to 11 readings per second with standard deviations of 0.040 mm and 0.051 mm. The experimental results verify the effectiveness and flexibility of the proposed method.

Characterization of Zinc Passive Film by Sonication in 7 M KOH Solution

The influence of 40 kHz ultrasound radiation on the passivation behavior of zinc in 7 M KOH is presented. The results of potentiodynamic and potentiostatic measurements combined with the current oscillation caused by the irradiation were examined to explain the mechanism and the sequence of formation of the oxide films during passivation. In this study, sonication was also used to investigate both effects of the passivation duration and passivation potential on the structure of the oxide layers; the adherence of the layers was found to depend strongly on both parameters. Scanning electron microscopy-energy dispersive X-ray （SEM-EDX） analysis of the zinc surface provided complementary information on the oxide layer composition and structure.

Choice of reference surfaces for machined surface roughness in milling of SiC_p/Al composites

In order to choose the appropriate reference surface on the machined surface roughness of Si Cp/Al composites, the cutting experiments of Si Cp/Al composites were carried out, and the machined surface topography was measured by OLS3000 Confocal laser scanning microscope. The 3D measured data of machined surface topography were analyzed by the area power spectrum density. The result shows that the texture of machined surface topography in milling of Si Cp/Al composites is almost isotropic. This is the reason that the values of Rq at different locations on the same machined surface are obviously different. Through the comparison of performance of different filtering methods, the robust least squares reference surface can be used to extract the surface roughness of SiC p/Al composites effectively.

扫描曝光系统中二维工作台x轴测量镜的面形在线检测

为了提高二维工作台的定位精度,提出了一种在线检测二维工作台x轴测量镜面形的方法。无需y轴测量镜,利用三路激光干涉仪检测工作台x轴测量镜的二次微分信息,对所得数据进行二次积分得到工作台测量镜的精确面形。分析了零点误差对工作台测量镜面形误差检测的影响,并提出了相应的校正方案。对所提出的方法进行了理论推导和实验验证,结果表明,所提方法的检测重复精度优于2.6521nm,验证了该方法对工作台测量镜面形误差检测的正确性,并且可对工作台x轴测量镜的面形误差进行实时补偿。

基于衍射图像的大型光学镜面在位检测

介绍了相位恢复测量系统的软硬件实现原理。构建了由CCD移动平台等硬件装置和基于GS迭代算法的软件程序组成的实验平台。并对一面口径500mm的球面反射镜进行了在位加工环境下的测量实验。测试结果与干涉测量相比较表明测量数据准确,精度满足光学镜面研抛加工要求。

基于直接相位测量术的系统参数标定方法

基于条纹反射的相位测量术被广泛用于获取镜面物体的表面三维形貌数据,系统标定是相位测量术中重要的一步,它直接决定了测量结果的精度。提出一种基于相位信息获得系统模型中未知参数的方法,建立相位和深度间的直接关系,并对比了采用相位信息和传统几何特征标识点棋盘格标定显示屏外部参数的准确度,证明了在离焦状态下,采用相位信息的方法具有更高的精度。使用标定好的系统测量了一个凹面镜和一个具有不连续反射表面的台阶工件,得到系统测量结果的误差约为22μm。实验结果表明所提方法可以精确地标定系统参数,并能获得高精度的三维测量数据。

Study on microscale adhesion between solid surfaces with scanning probe

The adhesion between two parallel solid surfaces is of great interest with the rapid development of micro-nano devices and instruments.The adhesion forces between a flat tip with a diameter^1.7μm and some surface have been determined by recording the force-displacement curves with an atomic force microscope(AFM).The flat tip is used to prevent wear and mimic the adhesion between two parallel surfaces.The free energy of the solid surface is calculated by the contact angles between the probe liquids and the surface.The adhesion force between parallel solid surfaces cannot be predicted by the theory of thermodynamic surface free energy.The adhesion measurements were carried out under ambient conditions,in a nitrogen-filled glove box,under distilled water,and under potassium chloride(KCl)solution.The outcome shows that the real contact area without the applied load is only a small proportion of the apparent contact area.The measurement stability and repeatability of adhesion by the AFM depend on the surface characterization,measurement methods and the environment.Under different environments,there are different interactions and factors affecting the adhesion force,and the dominant interactions and factors may be different too.The various interactions and factors are mutually coupled to determine the final adhesion force.

A displacement measurement system based on optical triangulation method

A new displacement measurement system is described in this paper according to the basic principles of traditional lasertriangulation method. The range of the traditional measuring method is enlarged by measuring in sections. Three independent CCDs, which are distributed uniformly along the optical axis, are used to achieve subsection measurement. The planemirror is regarded as a virtual detector. When imaging beam is reflected by the plane mirror, the beam is imaged on theCC D. The designed system is equivalent to add a CCD. The feasibility of the displacement measurement system is verifiedby the experiment.

Measuring the number concentration of arbitrarily-shaped gold nanoparticles with surface plasmon resonance microscopy

Molar concentration of gold nanoparticles is one of the most critical parameters of gold colloids in order to develop their applications in sensing, diagnostics and nanomedicine. Previous methods often stand just for gold nanoparticles with regular shape and narrow size distribution. In the present work, we proposed an absolute quantification method that determined the molar concentration of gold nanoparticles with arbitrary shapes and polydisperse sizes. This approach involved the real time monitoring and counting of individual nanoparticles collision events, from which the quantification of molar concentration was achieved using a theoretical model consisting of Fiek＇s laws of diffusion and Stokes-Einstein equation. The determination of spherical gold nanoparticles concentration resulted in excellent agreement with traditional spectrometry method. It was further demonstrated that the present approach can be expanded to determine the molar concentration of gold nanoparticles with arbitrary shapes and poly-diversed distributions.