Determining large step heights using zero-order interference fringe identification and an external cavity diode laser

Zero-order interference fringe identification is a powerful tool for measuring large step heights. In contrast to white light scanning interferometry, this study utilizes an external cavity diode laser as the light source. The zero-path difference point can be accurately identified by combining wavelength scanning interferometry, in which the laser wavelength is continuously changed, with single wavelength interferometry, in which the laser wavelength is fixed. The experimental apparatus is a two-arm interferometer containing the sample in the measurement arm. The step height denotes the distance between two locations of a zero-order interference fringe, which are obtained by continuously varying the length of the reference arm. The accuracy of a sample of 10 mm step height was found to be 0.33 μm.     

Interferometric determination of the refractive indices and birefringence of some highly oriented fibres

Variable wavelength interferometric technique (VAWI) is a direct method for determining the refractive indices and birefringence of highly oriented fibres. This method uses the polarizing interference Pluta microscope with a monochromatic light from wedge interference filter that provides a continuously variable wavelength. The standard calibration process of the Pluta polarizing interference microscope is carried out and a calibration graph is obtained. The refractive indices and birefringence of PEN, CONEX and TECHNORA were measured over the visible range of the spectrum and the constants for the Cauchy's dispersion formula were determined. The oscillation and dispersion energies were calculated from the measurements of the refractive index.     

A genetic optical interferometric inspection on micro-deformation

This paper describes a feasibility study of an optical method for measuring nanoscale deformation of micro-components that are commonly employed in the field of microelectromechanical systems (MEMS). Both theoretical and experimental results demonstrate that an optical interference fringe pattern resulted from an air gap consisting of two surfaces (object and reference surfaces) is a simple function of the deformation of the micro-component. A microscopic system incorporating a coaxial monochromatic light illumination and a high resolution CCD sensor is utilized to record the interference fringe pattern. The experimental results on different micro-components show that the proposed technique is applicable to the deformation measurement on micro-components of MEMS devices.     

干涉法测量掺铒光纤的非线性折射率

本文提出一种测量掺铒光纤非线性折射率的方法,该方法使氩离子激光通过一根掺铒光纤和另一根并排的普通光纤产生干涉.由掺铒光纤的非线性折射率导致的位相差变化将使干涉条纹发生位移,通过位移的测量可以得出光纤的非线性折射率.     

Determination of the optical thickness of polymer fracture surface layers from interference phenomena

Optical thickness of thin transparent layers was determined from the extinction condition for the interference of monochromatic light on the layer. Several ways have been suggested for the determination of the order of interference of the extinction fringes, based on the fringe shifts with the wavelength. The method has proved useful in the determination of the optical thickness of the fracture surface layer of polymers, but the range of its possible applications is wider.Na Petinách 1888, Praha 6, Czechoslovakia.     

单腔,双腔窄带干涉滤光片在单色光照射下的光散射

从理论和实验上讨论了单腔、双腔窄带干涉滤光片中的光散射现象，结果表明：光散射主要是由干涉滤不片和腔结构引起的。当波长小球滤光片峰值波长的激光束入射到该滤光片上时，在滤光片两侧形成散射光锥，散射光的散射角等于滤光片峰值紫移到入射光波长时滤光片所转过的角度，理论计算和实验结果符合得很好。     

多光源白光干涉仪的最佳波长组合

使用多个宽带光源构成的组合光源的白光干涉仪,其干涉信号为单个光源干涉信号的叠加,从而使干涉信号强度重新分布。通过理论分析和计算机模拟,发现一个最佳波长组合,使干涉信号零级条纹与次级极大条纹的强度差变大,且由于它的使用可以更精确地确定零级中心条纹的位置,提高系统分辨率,降低对系统信噪比的要求,并提出了选择最佳波长组合的方法。     

低频声表面波对细激光束的衍射效应

对于频率为几十赫兹的液体表面声波,实验上观察到反射光所形成的稳定、清晰的激光干涉图样.改变表面声波振幅,进一步发现了干涉图样的调制效应.调制效应明显地表现为干涉条纹的缺级,并且随表面声波振幅变化.依据波动光学原理,分析了调制作用下光束干涉所产生的光强解析分布及条纹特征,得到了干涉条纹角宽度与表面声波之间的解析关系,并据此对表面声波的特性参量波长和振幅及各级条纹相对光强分布规律进行了测定.     

Nanoscale deformation measurement by using the hybrid method of gray-level and holographic interferometry

This study extends the use of holographic interferometry to measure the nanoscale out-of-plane displacement with high surface resolution. It is noted that if the deformation is less than half of the optical wavelength, it is hard to find an obvious fringe pattern. Under such a situation, in general, the phase shift method is used. However, it needs to take more than 3 images for phase shifting and phase reconstruction In this paper, a more simple hybrid method of gray-level and holographic interferometry is used to extract fringe skeletons, in which it just needs to take one or two images for the normal deformation measurement directly, even if there exists no obvious fringe pattern. The displacement field with high surface resolution can also be obtained. The proposed method yielded a theoretical precision of 0.15 nm for out-of-plane displacement with a monochromatic CCD camera of 10-bit gray scale (1024 gray scales) sensitivity and microscale surface resolution for millimeter scale object with 640×480 pixels image resolution by an He–Ne LASER (632.8 nm wavelength) light source. The gray-level method is proposed to calculate the non-obvious interferometry fringe by traditional holographic interferometry hologram, and the result showed that this method works for this purpose.     

静态傅里叶变换光谱仪的机理及干涉条纹的校正

针对高速、瞬时光谱测量要求光谱仪的结构简单、装备方便、实时性强的特点,文章介绍了一种静态傅里叶变换光谱仪,并对其原理进行了推导与剖析。针对其调整中出现的干涉条纹的倾斜校正问题,进行了详细的理论分析和干涉条纹模型的数学推导,得出倾斜镜旋转参数和光学元件最小通光口径之间的数学关系,以及倾斜镜旋转参数和干涉条纹旋转参数之间的数学关系。通过利用Matlab7.0数学工具,对所总结推导的干涉条纹模型进行模拟,对所得的各种参数之间的数学关系进行验证。分析结果表明据此数学关系所求得的β角校正精度达到1.4%,是一种有效可行的校正方法。     

Multi-wavelength phase-shifting interferometry for micro-structures measurement based on color image processing in white light interference

Conventional multi-wavelength phase-shifting interferometry utilizes two or three monochromatic light sources, such as lasers, to realize the measurement of the surface topography with large discontinuity. In this paper, the white light source, with a single-chip CCD color camera, is used to accomplish multi-wavelength phase-shifting interferometry. In addition, we propose an algorithm which combines white light phase-shifting algorithm, equivalent wavelength method and fringe order method to achieve measuring and calibrating the micro-structures ranging from nanometer scale to micrometer scale. Finally, the proposed method is validated by a traceable step height standard.     

基于Mach-Zehnder干涉仪的光纤气体传感器理论

提出了一种基于马赫-曾德尔(Mach-Zehnder)干涉仪的光纤气体传感器。由于Mach-Zehnder干涉仪具有抑制光源噪声和模式噪声的特点,在高精度测量中越来越受到重视。在干涉仪的传感臂上涂有对待测气体敏感的薄膜,由于气体与敏感层的作用,导致光纤纤芯折射率发生变化,两臂的相位差发生变化,并引起干涉仪输出光强的变化和干涉条纹的平移,平移量与气体浓度对应。根据杨氏双缝干涉的理论,利用MATLAB对该研究进行计算机仿真,绘制出单色光的杨氏干涉图样和光强分布曲线,及气室中通入一定浓度的待测气体使干涉图样产生平移。     

迈克尔逊干涉仪测波长的一种便捷方法

提出了迈克尔逊干涉仪测波长的一种便捷且精确的测量方法。利用自制的光电计数及电机控制装置,在短时间内无须任何数据处理便可由计数器直接读取待测光源波长值。该方法不仅实现了条纹的全自动计数,又简化了干涉仪繁复的读数环节,更消除了仪器的零点误差。     

测量超快现象用光学系统时间特性的研究

超快速电子成象器件的发展,使超快现象的测量成为可能,同时也提出了研究光学透镜系统时间特性的新课题。实验证明:光学系统时间畸变和时间弥散,将影响超快现象的测量。本文除了对皮秒、飞秒变象管扫描相机工作在可见光波段时透镜系统的时间特性进行研究外,还对该系统用于紫外波段时,光学透镜系统的新特点进行了分析。     

Optical measurement of Young's modulus of a micro-beam

This paper presents an optical method based on the interference of light beams of equal path difference for the measurement of the Young's modulus of a micro-beam. An optical wedge which consists of an optical plate and a micro-beam which forms part of a micro-accelerometer is illuminated by a collimated monochromatic sodium light beam. Loading on the micro-beam is accomplished by a loading-pin mounted on a three-axis translation stage and the resulting interference fringe pattern is observed using a CCD camera connected to a computer. Loadings are recorded using a high-sensitive load cell which measures loads of up to 200 g with a resolution of 0.01 g. Test results conducted on micro-beams of different sizes show good repeatability and comparison of the experimental results with theory shows good agreement.     

Measurement of surface topography by RGB Shadow-Moiré with direct phase demodulation

In this paper we present the application of a direct demodulation method for the measurement of surface topography by means of Shadow-Moiré. In our set-up, we use three LEDs (with green, red and blue peak wavelengths) to illuminate the grating. Due to the different position of these light sources, a polychromatic Shadow-Moiré fringe pattern is produced, which can be described as the superposition of three monochromatic (red, green and blue) fringe patterns. Taking the image of this polychromatic fringe pattern with a RGB CCD camera, we get a monochromatic fringe pattern stored at each RGB channel of the CCD. The direct demodulation algorithm employed uses these fringe patterns to calculate the wrapped phase map. After unwrapping the phase map using a standard multi-grid technique, we implemented an automatic procedure to detect the area of interest of the phase map by removing low modulation zones and to calculate the absolute value of the phase. In this way it is possible to determine the topography of a surface with a single RGB snapshot maintaining a simple experimental set-up, which is an important feature, especially for the study of dynamic phenomena such as deformations. We present the experimental results obtained after measuring different objects with both smooth and rough surface textures.     

The Effects of Motion on Dynamic Moiré Interferometry

Experimental techniques (e.g. laser interferometry, photoelasticity) that generate fringe data are currently being utilized for analyzing full-field surface deformations in a variety of dynamic problems in experimental mechanics. As opposed to static problems, the transience of surface deformations in dynamic problems poses a unique problem in accurately resolving the fringe data that is acquired. Neumann determined that for time-lapse, double-exposure holographic interferometry the fringe contrast depends on the data acquisition time, wavelength of the light source, and transience of the dynamic phenomena. Dally performed a similar analysis for dynamic photoelasticity, where the dependence was on the stress gradients instead of the wavelength of the light source. This paper attempts to extend the analysis of Neumann and Dally to the analysis of transient fringe intensity data obtained from using dynamic moiré interferometry. It is found that the fringe contrast can depend on the frequency of the fringe field rather than the wavelength of the light source or stress gradients, and the fringe contrast will decay more rapidly for Gaussian light sources than constant intensity light sources. © 1997 Elsevier Science Ltd. All rights reserved.     

Spatial filters for differentiation

A grating is copied in monochromatic coherent light. The copy plate is not quite in contact with the grating. Therefore, the fringe contrast on the copy plate will vary across the field. This copy plate can serve as spatial filter for performing first order or higher order differentiations, if the geometry of the copy process was chosen properly.     

MOCVD原位红外测温方法的比较研究

MOCVD原位红外测温方法主要有单色辐射测温法与双波长比色测温法。利用薄膜等厚干涉模型与Kirchhoff定律计算了Si (111)衬底生长10 m GaN外延片的940 nm、1 550 nm光谱发射率,以Thomas Swan CSS MOCVD为例,比较了500 ℃至1 300 ℃范围内,940 nm单色辐射测温法、1 550 nm单色辐射测温法、940 nm与1 550 nm双波长比色测温法的相对误差和相对灵敏度,以及单色辐射测温法与双波长比色测温法的校准修正,并利用940 nm与1 550 nm双波长比色测温法在线监测了Si (111)衬底生长InGaN/GaN MQW 结构LED外延片过程中的温度。研究表明:940 nm与1 550 nm双波长比色测温法在相对误差及有效探测孔径修正校准上优于940 nm单色辐射测温法和1 550 nm单色辐射测温法,该结论可为MOCVD原位红外测温设备开发提供参考。     

基于法布里-珀罗干涉仪的液体浓度实时检测系统的研究

设计了一种对透明液体浓度进行高精度测量的动态跟踪系统。该系统根据液体的浓度与折射率关系以及折射率与光纤法布里珀罗(F-P)干涉仪干涉光波波长、级次之间关系,通过测量法布里珀罗干涉仪干涉级次的变化量,获得液体浓度的变化量。系统中光源选用He-Ne激光器,波长为632.8 nm,输出功率为2 mW,法布里珀罗干涉腔反射面的反射系数为0.9~0.95,平行度为(1/10~1/20)光波波长,平面度为(1/20~1/100)光波波长,接收干涉条纹的器件采用电荷耦合器件(CCD),对电荷耦合器件输出的信号进行二值化处理时采用阈值浮动措施,消除光强波动带来的测量误差。通过对一组不同浓度酒精进行测量,该系统可识别出0.01?的浓度变化。