二帧变换光源阴影莫尔技术研究

为了快速测量物体表面三维轮廓,提出一种变换光源位置的相移阴影莫尔技术.该方法通过控制两个光源的亮灭,将相移引入测量视场.使用二维经验模式分解法对条纹图进行正则化,结合螺旋相位变换方法和二帧相移算法对测量高度进行估计,利用发展的迭代自调算法提取精确测量相位.计算机仿真和光学实验结果表明,该方法的解调准确度优于现有的二帧相移解调算法,同时,由于消除了测量过程中必要的机械运动,只需要二帧条纹图进行相位解调,节约了测量时间.     

级数相位去包裹方法

提出了一个简单的相位去包裹方法－－条纹的极数相位去包裹算法,将其用来恢复物体的真实相位。与传统的条纹相位去包裹方法相比较,该方法能够消除光载频、物体边缘、阴影和盲点的影响。理论分析和实验结果证明该方法适用于条纹空间相位测量方法解调的包裹相位。     

相移阴影莫尔条纹正交化解调技术

提出一种基于克莱姆正则化分析法的三帧自标定相移阴影莫尔三维轮廓技术.该技术首先采用移动光栅的方法获得相移条纹图,然后通过不同帧相移条纹图相减去除条纹图背景,进而结合克莱姆正交化法和最小二乘法,发展了一种相位解调方法,提取了测量相位.以五步Harlharan算法为参考,用不同算法对同一物体表面进行测量.结果表明,相对于典型的三步相移法和主量分析方法,提出的方法测量得到的相位误差最小(0.5rad),且简化了测量过程.     

调相光栅的正交相干相位检测

本文提出了一种解调调相光栅相位的新方法.将一幅相位调制光栅图输入计算机,通过正交相干相位解调算法处理,能够高精度、快速地获得光栅的相位分布.本文详细论述了正交相干相位解调原理,并给出实验系统和处理结果,最后与其他类似的相位解调方法进行了比较.     

一种基于双参考平面的等相位坐标标定方法

栅线投影三维测量中通过标定技术把二维的相位信息转化为高度信息,提出了一种基于双参考平面的等相位坐标标定方法。该方法利用被测物体上相位和两个参考平面上相位相同的位置坐标,通过线性插值得到物体表面的高度,而不是传统方法中将物体上的相位直接减去参考平面上同一坐标下的相位得到绝对相位,再建立高度和绝对相位之间的函数关系(将此类方法称为等坐标相位法)。所提方法能够同时解决相位-高度转换以及由于栅线投影系统的非线性响应导致的非正弦性误差的问题。理论和实验证实了该方法的有效性。结果显示,等相位坐标法得到的主要由条纹的非正弦性引起的均方根(RMS)误差不到等坐标相位法的一半。     

基于压缩传感的纯相位物体相位恢复

传统的相位恢复算法通过双强度或者单强度测量的数据进行迭代运算以恢复丢失的相位信息, 它要求采样数据必须满足香农采样定理.当成像的分辨率较高时, 大量的测量数据势必会对数据采样设备提出更多的要求.因此, 为减少采样负担, 本文提出了一种基于压缩传感的相位恢复算法, 通过在傅里叶面的少量单强度测量数据, 应用改进的混合输入输出算法来恢复纯相位物体的相位分布.在采样数据远小于采样定理所需的条件时, 该算法仍能精确地恢复相位分布具有分块均匀特征的纯相位物体.数值仿真实验表明该算法具有良好的收敛性能. 关键词： 相位恢复 压缩传感     

基于低通滤波的相位掩模干涉图相位解调方法

 传统的四步相移算法在分析相位掩模干涉图时存在相移值误差、分辨力降低和相干噪声等不足,从而影响了动态干涉仪的性能。为了提高相位掩模干涉图的分析精度,提出了一种基于低通滤波的相位解调方法。该方法根据相位掩模引入相位的空间频率远大于被测相位空间频率的最大值,采用低通滤波的方法提取相位信息。数值分析结果表明,该方法的精度高于传统四步相移算法。分析干涉图的信噪比,合理选择低通滤波器,可进一步提高相位解调的精度。     

虚拟光纤Sagnac干涉仪及其数模混合解调系统

解调算法在Sagnac干涉仪系统中占有重要地位.目前已经提出的一些数字开环解调算法在运算过程中时常会出现某些特殊相位点互相混淆的问题,这会导致系统输出错误的解调结果.在对特殊相位点的产生原理进行理论分析的基础上,设计了一种以集成电路芯片为核心的虚拟光纤Sagnac干涉仪系统.该系统可以便捷地解决使用光纤Sagnac干涉仪难以对特殊相位点进行检测的问题,同时,可以方便地判别解调系统在这些特殊相位点是否会发生错误解调.最后,利用该虚拟Sagnac干涉仪对一种数模混合解调系统进行了特殊相位点测试.并通过实验测得该虚拟光纤Sagnac干涉仪的标度因数为49.9°/V;标度因数的非线性度为0.167%,标度因数的不对称度为0.088062%,零漂小9.5265°/h.     

小波相位解调轮廓术

针对傅里叶变换轮廓术因混频难以准确提取基频的问题,可将小波变换用于三维形貌相位直接解调。对其原理进行了研究,通过编程实现了小波相位解调。取Morlet复小波作为小波母函数,对调制栅线图逐行进行连续小波变换,从各位置的沿尺度方向的小波变换系数幅值的极值中可直接求取对应的相位数据。由于小波函数具有空域_频率两域的局部化特性,因此它对变形栅具有很强的自适应能力。为验证新方法,对其进行了仿真分析,同时还对石膏半球模型和化妆品瓶进行了实际测量,并分别用傅里叶变换和小波变换进行了处理。结果表明,新方法有效地克服了混频的问题,改善了相位解调效果,提高了测量精度,特别适合于复杂物体的形貌测量。     

抑制相位测量轮廓术饱和误差相位融合算法

在相位测量轮廓术中,由于被测物体表面反射率过大,导致照相机捕获的图像中部分像素点强度值超过照相机的最大量化值,即光强度饱和。分析了光强度饱和引起的相位误差,提出一种相位融合算法。该算法通过查找归一化后的最大调制强度,提取其对应的相位,并将该相位作为三维重建的最终相位。实验结果表明,在理想情况及测量系统存在Gamma畸变时该算法均能有效地修复饱和误差。当测量系统存在Gamma畸变时,校正后相位误差均方根值相对于传统技术减小了58.86%。     

次条纹积分法解调位相的三维面形测量

提出一种新的条闰相分析技术用于三维面形自动测量。将光栅图案投影于物体表面上，投影像随物体三维面形变形，形变的投影像用次条纹积分算法分析，求出位相变化和相应的三维面形。     

Phase-unwrapping algorithm in the presence of discontinuities using a system with crossed grating

A new phase-unwrapping algorithm for the phase map containing discontinuities by the use of a system with crossed grating is described in this paper. A crossed grating is projected onto the object in the usual way, the deformed grating image acquired is Fourier transformed and the frequency spectra for the individual gratings are separated. Using both phase distributions which have different sensitivities, the correct phase values in the presence of discontinuities, especially those caused by the object with height steps, can be obtained. This algorithm is fast and accurate. The results of the measurement of a three-dimensional object with height steps are presented.     

A new pixel matching method using the entire modulation of the measured object in online PMP

A method using entire modulation information of the measured object itself for pixel matching is proposed in online phase measuring profilometry (PMP). Only one fixed sinusoidal grating is projected onto the moving measured object and then five deformed patterns are captured by the imaging system (CCD). Because the contrast of the sinusoidal grating is a constant, the modulation distribution of each deformed pattern reflecting the gray of the measured region can be extracted. The entire modulation of the object cut from one of them is regarded as a template, and then the distance of the measured object's movement between each two adjacent deformed pattern can be calculated by the correlation operation so that we can cut the corresponding parts containing the measured object's information from five deformed patterns. Then the discrete phase can be calculated with Stoilov algorithm. By the phase unwrapping and the mapping algorithm, the object can be reconstructed exactly. A series of simulations and experiments confirm its feasibility and validity.     

A three dimensional on-line measurement method based on five unequal steps phase shifting

A three-dimensional on-line measurement method based on five unequal steps phase-shifting with phase measuring profilometry is presented. While only one sinusoidal grating pattern is projected onto the measured object moving with the pipe-line, five arbitrary deformed patterns are captured by CCD as the measured object moves within a duty cycle of the grating pattern. The modulation distribution based on Fourier transform profilometry is introduced to realize pixel matching so as to calculate the corresponding equivalent shifted phase on the deformed patterns. A five unequal steps phase shifting algorithm is developed, which is suitable for non-uniform motion of the pipeline. The experiments verify its feasibility and validity.     

On-line phase measuring profilometry based on phase matching

On-line phase measuring profilometry based on phase matching is proposed. While just one fixed sinusoidal fringe is projected on a measured object moving with the pipeline, deformed patterns modulated by the object moving at the same distance moment are captured synchronously by the CCD camera. The phase information of the object in those captured deformed patterns can be predicted using FTP method to assist the pixel matching so as to realize the point-to-point correspondence of the object in the captured deformed patterns. Meanwhile, the equivalent phase-shifting deformed patterns can be extracted. So the three dimensional shape of the object can be reconstructed successfully with an equal phase-shifting algorithm. Numerical simulation and experiments show feasibility and validity of the proposed method.     

Automatic Analysis of the Phase Object Using Projection Moire Deflectometry

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一种采用相位测量轮廓术的工件在线三维检测方法

提出了一种基于相移轮廓术在线检测工件三维信息的方法.利用计算机编程产生的一固定正弦光栅图通过数字投影机投射在流水线的一段区域,无需专门的相移装置,当物体在线移动穿过此区域时,使用计量光栅等距离定位发信,控制CCD采集五帧变形条纹图,并采用具有一定特征的标记实现五帧变形条纹图间的亚像素级像素匹配,提取相移变形条纹图,由Stoilov算法计算,得到工件表面截断相位,展开后可得到物体表面三维信息.实验验证了其可行性.     

位相相关在大尺寸物体三维重构中的应用

提出了一种对大尺寸物体进行三维重构的方法.将一正弦光栅投影到物体表面,通过摄像机得到有变形条纹的二维子区域强度像.在频域中完成各二维子区域强度像之间的相关,根据输出的相关峰值位置即可得出平移量,通过图像拼接获得有变形条纹的整个物体的二维强度像.运用傅里叶变换轮廓术可得到大尺寸物体的三维型面,给出了实验结果.     

Shape identification using phase shifting interferometry and liquid-crystal phase modulator

A phase shifting technique using a Michelson interferometry system is presented and applied to surface contour measurement. Hyperbolic fringes are produced by the interference of two spherical wavefronts expanded from a beam expander. The fringe pattern is projected on an object surface and the deformed grating image is captured by a CCD camera for subsequent analysis by a PC. Phase variation is achieved by a liquid-crystal device incorporated in the Michelson interferometry system. Results obtained using the proposed method for objects of various shapes and sizes compared well with those from a conventional profilometer.     

Phase locked loop profilometry

An innovative technique for obtaining automatic three-dimensional shape information of a diffuse surface is presented. The technique is based on a new approach of phase measuring from a fringe pattern. The target to be studied is first modulated by projecting a linear grating onto its surface. The linear fringes are deformed according to the surface shape. Demodulation is carried out by determining the phase of these deformed fringes using a novel digital phase locked loop demodulation algorithm. The technique has the main advantage that the traditional phase unwrapping process is not required. The phase is determined continuously as the algorithm scans the two-dimensional fringe pattern. Owing to its sequential nature, this phase detection technique can be implemented using a special purpose video processor for phase determination at video rates, making it a very fast algorithm. The algorithm along with experimental results of real surface profiles are presented.