基于正交光栅投影的快速调制度测量轮廓术

在共轴光学测量系统中,将水平光栅与竖直光栅沿着光轴方向相距一定距离垂直放置,被测物体放置在两个光栅成像面之间.利用同光轴方向放置的CCD采集一帧正交光栅像,进行傅里叶变换、滤波和逆傅里叶变换操作,分别得到对应水平条纹分量和竖直条纹分量的调制度图,通过计算其调制度比,实现对复杂物体的快速三维面形测量.在几何光学近似条件下,给出两个光栅投影像的光强表达式,讨论了水平光栅与竖直光栅间距和投影镜头光圈大小对测量结果的影响.对标准平面和复杂物体三维面形的快速测量结果表明,该方法能快速有效地测量恢复物体的三维信息.     

投射离焦三维测量方法

提出了一种在投射光路中实现主动离焦三维测量的方法。该方法采用改变投射参数来拍摄物体的两幅图像,通过计算图像的调制度分布来获得物体的三维分布。该方法不但可使三维测量的空间分辨率达到单个像素,而且扩大了离焦三维测量的使用范围。实验得到的精度高于2.8%。     

基于调制度分析的快速三维物体识别方法

提出了一种基于调制度分析的快速三维物体识别方法。将两个有一定间距且正交的光栅同时投影到被识别物体表面上,使被识别物体位于两个光栅正焦像面之间,从同一方向获取被物体高度信息调制的正交光栅像,而物体的高度信息就被编码在这个图像中。采用傅里叶变换和空间频域分析,可分别得到两个方向上的基频。然后计算识别参数(每个基频强度的和)的值,识别参数值可以被看作是二维识别空间的一个点,对于不同形状的物体,识别参数值是不同的,所以不同物体的识别参数将对应识别空间不同的位置。计算机模拟实验和实际物体的识别实验证明了此方法的有效性。     

小波变换在调制度测量轮廓术中的应用

基于调制度分析的光学垂直测量技术利用投影和成像共轴,可以有效地解决复杂物体和台阶状物体测量时所存在的遮挡、阴影等问题.该方法不需要截断相位计算和相位展开过程,只需解算条纹的调制度分布就能得到被测物体的三维面形,已成为广泛应用的光学三维检测方法.针对基于傅里叶变换方法的垂直扫描测量技术存在的问题,利用小波变换的局部和多分辨率特性,将小波分析技术用于调制度测量轮廓术中,提高了每个扫描位置获取单帧条纹的调制度测量的精度.推导了调制度和小波系数之间的关系,计算机模拟和实验均验证了方法的有效性.     

调制度测量轮廓术在复杂面形测量中的应用

调制度测量轮廓术(MMP)是将物体的高度信息编码在投影到待测物面上的正弦条纹的调制度信息中,可以实现对物体的垂直测量,特别适合测量表面有高度剧烈变化或不连续区域的物体。探讨了基于傅里叶变换的调制度测量轮廓术在复杂面形测量中的应用,提出了调制度焦深的概念并详细分析了调制度焦深对测量的影响,以调制度焦深为基础从测量系统设计的角度提出了提高测量精度的具体措施,给出了实验系统设计方案,讨论了影响测量精度的几个实际问题及解决方案。对复杂面形和深孔物体的实测结果表明,基于傅里叶变换的调制度测量轮廓术测量复杂面形物体可以达到较高的测量精度。     

从变形光栅条纹提取基准光栅信息

基于傅里叶变换轮廓术,提出一种直接从变形光栅条纹中提取基准光栅条纹信息并重建基准光栅的测量方法.分析了基准光栅条纹和参考平面的功能,揭示变形光栅条纹和基准光栅条纹的关系;应用窗口傅里叶变换对变形光栅条纹中的各个微小区域进行频谱分析,从中识别并提取基准光栅的频率和相位信息;重构出一幅完整的基准光栅条纹,实现三维物体形貌测量.实验结果表明该方法是可行的,为三维形貌测量提供一种新手段.     

基于调制度层析的在线三维测量方法

调制度反映相位展开可靠性的程度,与物体本身灰度和形状有着紧密的关系,因此可作为测量的特征标记。提出了一种采用调制度层析实现在线三维测量的方法。通过投影一固定的正弦条纹到待测运动物体上,借助物体运动可产生等效的相移变形条纹。利用基于傅里叶变换轮廓术调制度模型计算各帧等效的相移变形条纹的调制度,并采用层析方法从各帧调制度分离出反映待测物体的调制度层析特征,以该层析信息作为特征模板,实现像素匹配,从而获取各帧具有一致像素坐标的等效相移变形条纹,实现在线移动物体的三维面形测量。实验证明了该方法的可行性和实用性。     

基准光栅重构傅里叶变换轮廓术

应用傅里叶轮廓变换术进行三维形貌测量中,为了获得待测物体的高度相位信息,通常需要采集两幅图像.因此当光学系统发牛变动时,必须重新采集基准光栅图像,不利于快速测量.提出一种从变形光栅图像中获取基准光栅图像信息的测量方法.首先在变形光栅图像中记录基准光栅信息,然后通过傅里叶分析提取基准光栅频率信息,通过图像分析获得基准光栅相位信息,最后重构出一幅完整的基准光栅图像,实现三维物体形貌测量.实验结果验证了该方法的可行的.     

窗口傅里叶变换轮廓术中窗口尺度选取的改进

多尺度窗口傅里叶变换法根据条纹信号的瞬时频率梯度来确定信号的局域平稳长度,再由局域平稳长度来控制窗口的尺度,即窗口的尺度和局域平稳长度成正比。使用多尺度窗口傅里叶变换法来使条纹信号的频谱局域化,可以在条纹信号的频率分辨率和空间分辨率之间达到一种较佳的调和。针对多尺度窗口傅里叶变换三维形貌测量技术中局域平稳长度提取算法的不足进行了改进,使窗口尺度的选取更具合理性,对变形光栅基频提取更精确,进一步减小了位相测量的误差。给出了理论分析、计算机模拟以及实验结果。     

二值条纹高速离焦投影的旋转风扇面形测量

傅里叶变化轮廓术将结构光投影与傅里叶条纹分析相结合,只需一帧变形条纹就可以重建被测物体三维面形,是动态三维面形测量中的首选。选择最适用于傅里叶变换轮廓术测量系统的二值条纹编码方法,对二值化后的正弦条纹进行离焦投影,既克服了普通商用数字投影仪的刷新频率限制和非线性响应影响,又能充分利用光学成像系统的低通滤波特性获得很好的高速正弦光场。设计搭建了一套高速离焦投影条纹并同步采集的三维面形测量系统,利用该测量系统对高速旋转的散热器风扇进行测量,得到任意采样时刻风扇扇叶的三维面形信息,重建完整的风扇转动过程。能进一步分析散热器风扇扇叶在高速转动过程中的形变,为散热器风扇材料选择以及改善其性能提供可靠的测量技术方案与原始数据,有效地拓展了动态三维面形测量的应用。     

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.     

Recovery of three-dimensional shapes by using defocused structured light

We present a new concept for three-dimensional shape recovery using defocused structured light (DSL) images. The DSL technique externally extracts the depth information from the scene by using projections of cylindrical wavefronts on the object. These projections show different degrees of defocus as a function of the depth. Efficient algorithms for shape recovery are developed taking advantage of the spatial regularity of the projected light and the profile of each fringe. In this way a depth map of the scene is obtained using only one image. Experimental results are shown and we discuss the possibility of a real time implementation.     

利用Cramér-Rao理论研究相位差法的最佳离焦量

 针对光子数足够多的情况,利用Cramér-Rao理论研究了在选取离焦作为附加像差时,不同的待测波前和目标对最佳离焦量选取的影响。结果表明:在点目标情况下,像差的大小和空间频率对最佳离焦量的影响不大;而在扩展目标情况下,最佳离焦量虽然与待测像差的空间频率关系不明显,但随着待测像差峰谷值的增大而增大。最佳离焦量与目标的结构有关而与其扩展程度关系不大,成像时目标上各点的干扰越大,最佳离焦量越大。     

Fast Calculation of Computer-Generated Fresnel Hologram Utilizing Distributed Parallel Processing and Array Operation

Fresnel CGH for a three-dimensional (3-D) object is generated by calculating the Fresnel diffraction, but it requires a huge amount of calculation. This is one reason for the difficulty in realizing real-time holography. We propose fast calculation method of computer-generated Fresnel hologram (Fresnel CGH) utilizing distributed parallel processing and array operation. In our method, a projected image with depth information of the 3-D object is prepared to calculate the Fresnel diffraction. The Fresnel diffraction of the projected image is then calculated with depth information by array operation and distributed parallel processing. Parallel processing is realized using JavaSpaces and many standard computers. In our array operation, calculation error in phase distribution on a hologram occurs more than the strict Fresnel diffraction. However, it was confirmed by experiments that the influence of an error can be controlled and ignored. In this paper, our proposed method and some experimental results are shown.     

一种无需标记的在线三维测量方法

提出了一种无需标记的物体在线三维面形测量方法。将一固定的正弦条纹投影到待测运动物体上,借助物体运动产生等效的相移变形条纹。基于傅里叶变换轮廓术的调制度对各帧变形条纹计算,提取其具有某一特定分布的特征区域,采用相关度最大法,检测各帧变形条纹对应的调制度特征区域的位移量来检测出物体的移动,从而实现像素匹配,得到一组像素坐标完全一一对应的等效相移变形条纹图。利用Stoilov相移算法得到物体的截断相位,利用位相展开算法展开位相,通过位相和高度映射即可实现在线移动物体的面形测量。通过计算机仿真验证了该方法的可行性。     

双工件台光刻机中的焦面控制技术

面对可用焦深日益缩短的趋势,高精度的焦面控制技术显得尤为重要。针对双工件台光刻机中采用的焦面控制技术,介绍了基于偏振调制的光栅检焦技术及其测量原理,研究了双工件台光刻机中的调平调焦技术。基于平面拟合、最小二乘法及坐标变换公式推导了曝光狭缝内离焦量计算公式;研究了一种离焦量解耦算法,该算法将曝光狭缝内离焦量解耦为调平调焦机构三个压电陶瓷的独立控制量,并使狭缝曝光场中心在调平调焦运动过程中不发生平移。经仿真分析表明,该算法可用于调平调焦精度优于10 nm 的高精度调焦调平系统, 能满足线宽小于100 nm 投影步进扫描光刻机的需要。     

3D Reconstruction of Large-Depth Objects Using Fresnel Diffraction of a Ronchi Grating and Simultaneous Recording of Reference and Object Fringes

We propose an active triangulation based range-finding system that, besides its simplicity, has two advantages over similar existing systems. First, the system can acquire range data for large-depth objects since it generates an illumination pattern with large-depth of focus using Fresnel diffraction from a Ronchi grating projected over the entire object surface. Secondly, the system does not need preliminary recording of reference fringes since it displays simultaneously, on a single image, both reference and object deformed fringes. This system offers other properties: it is mechanically simple, uses everyday optical components, is low cost, can be operated via a PC and uses relatively simple image analysis software. Three dimensional reconstructions are illustrated for various objects having 10 cm maximum depth variations. The depth accuracy (typically 0.5 mm for an object located at 350 mm from the camera) is comparable with other systems, but a certain compromise has to be accepted in acquisition time (typically 1 minute). This system can find applications in research laboratories as a tool to provide range data with relatively good depth accuracy.     

直接法应用于蛋白质二维晶体的电子晶体学图像处理

试把直接法应用于抗生蛋白链菌素(streptavidin)沿［001］方向投影的模拟像和相应的理论结构因子作图像处理.先用两张高分辨电子显微像作直接法解卷,以互补因衬度传递函数的作用而损失的结构信息,求得的欠焦值比用单张像解卷的结果更接近真实值.把从结构模型计算出的030nm以内的相位,以及025nm以内的振幅作为起始数据,进行直接法相位外 推,并借助团簇分析方法得到030nm至025nm之间的相位.所得分辨率为030nm的解卷像 和分辨率为025nm的晶体结构投影均与理论结构模型的相应投影电 关键词： 高分辨电子显微学 直接法 图像处理     

Phase deviation analysis and phase retrieval for partial intensity saturation in phase-shifting projected fringe profilometry

Intensity saturation may take place as a sinusoidal fringe pattern is projected onto an object which has a relative high reflective index on some regions of the surface. If a phase-shifting method is used, the illuming light intensities at the same point of the object may have different values for each projected phase-shifting fringe pattern. Therefore, when the intensity at a point of the object exceeds the saturation level for a certain phase step of projected fringe pattern, other intensities obtained at the same point with different phase steps of projected fringe patterns do not exceed the saturation level. This kind of saturation is defined as partial intensity saturation. In the case of partial intensity saturation, a relative larger phase error is introduced when a conventional phase reconstruction algorithm is used in the phase-shifting projected fringe profilometry (PSPFP). To get rid of such disadvantage, an improved algorithm for phase reconstruction is proposed in this paper. By using the new algorithm, the effect of partial intensity saturation for the phase reconstruction can be decreased greatly and a good quality of reconstructed phase map can be obtained. Phase deviation of the reconstructed phase is also analyzed. Finally, an experimental result with PSPFP is presented to validate the feasibility of the proposed algorithm.