基于改进Sierra 抖动算法的微离焦投影三维轮廓测量技术研究

通过分析传统频率调制的相位轮廓测量技术,提出基于蛇形扫描改进Sierra抖动算法,结合微离焦投影,可减小正弦光栅二值化的量化误差,同时抑制非对称纹理,能较大地改善离焦后光栅的正弦性。将该抖动算法生成的离焦光栅用于三维轮廓测量技术,与Bayer有序抖动算法、Sierra抖动算法和Floyd-steinberg误差扩散抖动算法进行了比较,实验结果表明:改进Sierra抖动算法具备更好的适应性,能够较大程度地降低相位误差,运算速度快,生成光栅准确度较高,改善了相位质量,适用于高精度三维轮廓测量。     

虚拟光栅变频投影三维测量技术的研究

虚拟光栅变频投影三维测量技术采用多光束干涉条纹形成虚拟余弦光栅,将虚拟余弦光栅投影到被测物体上得到被物体形貌调制的变形虚拟光栅。通过调整多光束干涉的楔角改变虚拟光栅频率,将两幅不同频率的变形虚拟光栅经过光学接收系统成像在CCD像机上,对CCD像机记录的变频变形光栅图像进行综合处理从而获取被测物体的三位形貌。本文给出了这种测量技术的原理,实验结果表明,采用变频虚拟光栅投影三维形貌测量技术可以有效地解决三维测量中被测物体高度变化率过大引起相位展开困难的问题。     

光栅投影三维形貌测量低通滤波器的设计

分析在光栅投影三维形貌测量中,用于对变形光栅像解调的低通滤波器的性能。分别设计了脉冲响应为9点的FIR低通滤波器和IIR4阶Butterworth低通滤波器。处理1×512大小的光栅图像,FIR滤波器需要16128次加法和2304次乘法,位相测量平均误差为0.0356rad;4阶Butterworth滤波器只需4096次加法和4096次乘法,位相测量平均误差为0.0043rad。仿真试验结果表明,IIR的Butterworth低通滤波器具有更高的测量精度和计算速度。     

基于彩色双通道投影的快速调制度测量轮廓术

针对传统调制度轮廓术测量速度较慢的问题,本文提出了彩色双通道投影的调制度轮廓术.该方法将两个正弦光栅通过不同的通道同时成像在被测物体上,两光栅像面不重合(相互离焦),采用彩色CCD采集条纹图,利用彩色CCD的色通道性质,分离出两个单一通道的条纹图,得到其调制度分布.由于调制度比值和物体高度存在一一对应关系,由此可重建物体三维面形.文中给出了实验的设计方案、信息获取的方法、实验结果及误差分析,讨论了影响测量精度的几种原因.实验结果表明,该方法测量深孔等面形复杂物体,测量速度快,算法简单,且可以达到较高测量精度.     

泰伯衍射光场的三维分布特征

采用菲涅尔近似公式和傅里叶级数展开的方法，分析了罗奇光栅、正统强度光栅、正统振幅光栅的泰伯衍射光场的三维强度分布特征，给出了计算机模拟的三维强度分布图，并讨论了一些在三维传感领域有应用前景的性质。     

基于单步相移算法的投影技术及其应用

利用一组规则栅线投县物体表面的变形光栅,采用单步相移算法解调出含有物体表面高度信息的位相。本文建立了一种较传统相移技术快速,但精度相当的投影技术。该技术只需采集一幅图象。文中给出了一个典型试件的实验结果和分析。     

航空相机光电自准直检调焦系统

为了补偿航空相机在高空中由于气压,温度等环境变化引起的离焦,本文设计了一个基于光电自准直方法的航空相机自动检调焦系统.利用相机内部高对比度光栅进行调焦,有效避免了基于图像处理的调焦系统在目标物对比度较低时调焦失败的情况.采用物方光栅、像方光栅和反射镜摆扫的方式对光强信号进行调制,利于信号的分析处理;采用粗,精结合的遍历...     

二维傅里叶变换法三维曲面检测

对投影光栅方法获得的位相调制空间载波图进行二维数字图象处理,实现了散射物体的三维曲面测量,利用二维快速傅里嚅变换将空域信号转变为频域信号,对一级频谱进行傅里叶反变换,逐步解调出其位相值,重建了被测物体表面的形貌。文中给出了对人体模型的实验测量结果。     

位相型自聚焦微分滤波器

介绍一种用二元光学方法制作的光学图象微分滤波器，它是由两个频率相近的位相型Ｒｏｎｃｈｉ光栅和离轴型位相菲涅耳波带片的组合而成的。称之为位相型自聚焦滤波器。它具有衍射效率高，光路简单，使用方便等特点。     

阶梯形浮雕和折射率位相光栅的衍射性质比较

位相全息图一般既有浮雕调制又有折射率调制,它们都会对衍射特性产生影响。利用以严格电磁波理论为基础的模式匹配法（ＭＭＴ）,从理论上比较了阶梯形浮雕位相调制光栅和折射率位相调制光栅对ＴＥ波的各级衍射效率。尽管它们同一周期内的相应部分所引起的位相变化相同,但随着光栅层厚度的加大两种位相调制光栅的各级衍射效率会出现差别。这种差别与周期有关。并将矢量理论的结果与标量理论的结果进行了比较,研究结果对研究全息术     

Electronic speckle pattern interferometry based on spatial fringe analysis method using two cameras

A new speckle measurement method is proposed by applying a spatial phase shifting method to multi-camera technology in order to perform a high resolution, high speed, and large deformation measurement. It is confirmed that the alignment of optical elements in this method is easier than the ordinary multi-camera methods because the optical system uses only two cameras. The validity of principle of the method is discussed by the results of experiments. It is shown that measurement precision of this method is about 1/50 wavelength in a small deformation measurement. Furthermore, the method is improved for a large deformation measurement method by accumulating the results of the small continuous deformation measurement. The optimum sampling process of the large deformation of an object is proposed in order to detect the phase map of the large deformation. It is confirmed that the large deformation can be precisely measured by this method.     

相移掩模方法及其一维数值模拟

相移掩模方法是一种新的光刻技术，它可以提高现有光刻设备的分辨率，使超大规模集成电路及二元光学的制作迈上一个新台阶。本文介绍了相移掩模方法的基本原理，用部分相干光成象理论分析了用于光刻的投影照相系统的成象特性，导出了一维成象的简化公式，对一维光栅结构进行了计算机数值模拟并给出了模拟结果。     

相移条纹投影三维形貌测量技术综述

结构光三维形貌测量系统目前得到了越来越广泛的应用和研究,相移条纹投影三维形貌精密测量技术是其重要的发展方向。对结构光相移条纹投影三维形貌测量系统的应用发展、工作过程、不同系统构成方式、相移条纹的各种形式及特点、相位误差校正方法、不同相位解包裹算法及其优缺点和适用场合、测量系统数学模型的实现方法及其相应的优缺点、高动态范围测量技术等进行了详细的分析。对相移条纹投影系统的工作流程、实现方法、关键技术的发展及其存在问题等进行了比较全面的梳理,为三维形貌精密测量技术进一步满足先进制造中更高精度的要求指出了后续的研究方向。     

Making optical low-pass spatial filters by thin-film phase grating

A modified rule was applied to design a grating optical low-pass spatial filter (GOLF) with a thin-film phase grating. This filter differed from the crystal type of optical low-pass spatial filter (OLPF). The fabrication method of the thin-film phase GOLF was also different from the conventional lithographic process. A new fabrication method utilizing a metal mesh mask and a thin-film coating process was applied to make the GOLF. The process had the advantages of being simple and cheap, and would thus be good for mass-production. The modulation transfer function (MTF) of the device was measured and the results agree well with the theoretical calculations. Finally, the GOLF was installed on a digital camera which was used to capture images of the circular zone plane (CZP), to show the Moiré pattern suppression ability.     

采用光栅投影的三维测量方法

提出一种新的三维坐标测量方法,该方法基于光栅投影、相移和三角测量等测量方法。与传统的光学测量方法不同,测量系统采用两个CCD相机记录投影光栅,减小了测量误差,提高了测量精度。测量实验结果在各个坐标上的精度分别为?靘,?靘,?8.5靘,总体精度优于20靘,证明了该方法的先进性和可行性。     

Visualization of two-dimensional phase gradients by subtraction of a reference periodic pattern

We describe a simple method for visualization of phase objects. The phase object is placed between a printed two-dimensional periodic pattern and a CCD camera. The ray deflection that is due to the phase object distorts the image of the pattern. This image is subtracted from a reference image and then, by squaring and low-pass filtering, a measurement of the two-dimensional refractive-index changes is obtained. Because the optical system does not require special alignment or illumination, the method presented has potential application for detection of gas leaks in industrial environments.     

Dynamically shifting the focal spot with tunable pupil filters

Abstract

It is popularly believed that when the focal spot is shifted far away from the optical axis of optical system with the pupil filter, it will be significantly aberrated. Therefore, the pupil filter is usually only used to adjust the distribution of the focal spot at the optical axis of optical system. In this paper, the special combination of the phase pupil filter shifting the focal spot and the high-pass filter eliminating the aberration of the focal spot is designed so that the focal spot can be shifted dynamically at the focal plane. By utilizing the Debye vector diffractive theory, the shifting behaviours of the focal spot are investigated in detail. The proof-of-principle experiment demonstrates the validation of the method for dynamically controlling the position of focal spot. This work is helpful to realize dynamically shifting the focal spot with the pupil filter and may find valuable applications in particle trapping, microscopes, optical engineering, and so on.     

一种新的高精度测相方法

提出采用光学移相办法测量超高频调制光相位特性的一种方法。它具有精度高、实用性强等特点。     

Dynamic measurement of 2D refractive index distribution of NaCl solutions

We demonstrate a simple and reliable method for measuring the two-dimensional refractive index (RI) distribution of transparent liquids, either homogeneous or inhomogeneous. The RI variation and the RI over the laser incident surface are measured by computing the phase shift of the interferograms as the optical path difference between the two beams passing through the sample liquid and air is changing. The phase shift is calculated by analyzing the interferograms by fast Fourier transform and a fringe shift counter. The RI change of the NaCl–water in the dissolving process was successfully measured by our method. This algorithm is stable, fast, efficient and of high accuracy up to 10^?4. It holds potential for some applications that requires noncontact, and particularly for inhomogeneous transparent mediums.     

Full-field optical coherence tomography by achromatic phase shifting with a rotating polarizer

We demonstrate two-dimensional detection optical coherence tomography (OCT) using achromatic phase shifting with a rotating polarizer. This phase shifting, which experiences a light beam with a cyclic change in its polarization state, is, in principle, independent of wavelength. We simulated the wavelength dependence of an achromatic phase shifter using Jones calculus and found that the achromatic region exceeded 145 nm when the deviation of the phase retardation was less than +/- 0.5 degrees. Using the achromatic phase shifter and a conventional phase-shift calculation method, we obtained en face OCT images of an onion at different depths. This method is effective to enhance the quality of OCT with an ultrabroad-spectrum light source.