标准硅球直径精密测量系统的设计

基于多光束干涉的基本原理，导出了使用斐索干涉仪测量硅球直径多光束干涉光强分布的精确公式。针对目前的硅球直径测量系统忽略了多次反射对干涉信号造成的影响和系统中固有的条纹清晰度低的问题，研究了多次反射对干涉信号造成的误差，结果表明其最大光强误差可达到8％。通过对光学干涉系统结构设计和元件参数选择，最大限度地优化了干涉条纹的可见度，并设计出零背景光强标准硅球直径精密测量系统。数值模拟结果表明，该系统不仅极大地提高了干涉条纹对比度、消除了背景噪声，而且可通过改变透镜焦距调节干涉条纹的强度以达到CCD的最佳工作范围，从而提高了光强信号的测量准确度。     

Experiments with active phase matching of parallel-amplified Multiline HF laser beams by a phase-locked Mach-Zehnder interferometer

Active phase matching of multiline HF laser beams by means of a phase-locked Mach-Zehnder interferometer was demonstrated by locking the interferometer to the central interference fringe at zero optical path length difference. The central fringe could be found by varying the spectral content of the input beam. Laser amplification in one leg of the interferometer decreased fringe visibility without adversely affecting locking. Single-line fringe patterns produced by an array spectrometer (while the interferometer was operated in its scanning mode) were analyzed to show that no significant dispersion occurred in the amplifier. The techniques developed have potential for measuring dispersion mismatch between larger parallel amplifiers. These experiments demonstrated in principle that a number of multiline HF amplified beams can be recombined and phase-matched to produce a high beam quality output beam.     

Investigation of the influence of spatial coherence of a broad-area laser diode on the interference fringe system of a Mach-Zehnder interferometer for highly spatially resolved velocity measurements

Laser Doppler anemometry is a method for absolute velocity measurements that is based on a Mach-Zehnder interferometer arrangement and usually employs transverse fundamental-mode lasers. We employed inexpensive and powerful broad-area laser diodes and investigated ways in which an interference fringe system is influenced by the spatial coherence properties of a multimode beam. It was demonstrated that, owing to poor spatial coherence of the beam, interference is suppressed in the marginal regions of the intersection volume. Based on these results, a sensor for highly spatially resolved velocity measurements can be built. The inherent astigmatism of the broad-area diode is corrected by an arrangement of two crossed cylindrical lenses. An interference fringe system of length 200 microm and a relative variation in fringe-spacing of only 0.22% were demonstrated with light emitted from a broad-area laser diode with a 100 microm x 1 microm emitter size. Based on this principle a powerful, simple, and robust laser Doppler sensor has been achieved. Highly spatially resolved measurements of a boundary layer flow are presented.     

Stroboscopic white-light interference microscopy

The principle of stroboscopic motion freezing of oscillating objects extends directly to interference microscopes that use coherence as part of the measurement principle. Analysis shows, however, that the fringe contrast loss for out-of-plane motion in stroboscopic interferometry is a wavelength-dependent phenomenon, which can alter the apparent nominal center wavelength of the white-light source. As in monochromatic systems, the key adjustable parameter is the duty cycle, equal to the product of the vibrational frequency and the pulse width. This theoretical study provides detailed graphs of expected errors as a function of the duty cycle, including fringe contrast loss, apparent wavelength shift, and measurement error.     

Measuring the refractive indices of liquids with a capillary tube interferometer

A theoretical analysis of the fringe pattern produced by a capillary tube interferometer is presented, which is expected to be two-beam interference, and a computer program to simulate the interference fringe pattern is established. By comparing the simulated fringe pattern and the experimental fringe pattern, the refractive index of the liquid can be given when the two fringes coincide best. The results of this method are close to those of the Abbe refractometer.     

Using minimum deviation of a secondary rainbow and its application to water analysis in a high-precision, refractive-index comparator for liquids

A new method for measuring the refractive-index difference of a liquid has been developed. The liquid to be measured is contained in a 60-mm-diameter, cylindrical glass cell, and a He-Ne laser light is passed into the cell so that the laser light incidence fulfills the condition of minimum deviation. In this condition, the beam emerging from the cell has a fine interference fringe. The position of the interference fringe is read out as a marker to measure the deflection of the laser light. Directly reading the peak shift of the interference fringe makes it easy to obtain the refractive index difference of the liquid with a fairly high precision of at least 6 x 10(-6). Further high precision is potentially expected to be realized by use of an improved data analysis treatment of the overall interference fringe pattern.     

E150柴油机缸内压缩温度场的全息干涉测量

介绍了采用激光双曝光全息干涉技术测取柴油机压缩温芳场的基本原理及实验过程。提出了利用绝热压缩缩区的温度作为计算干涉条纹的初始条件,从而为计算全息干涉条纹所对应温度提供了可行的方法。由柴油机压缩过程中缸内的温度场的测量结果可以看出,在柴油机压缩过程中,缸内温度变化幅度在４０Ｋ左右,最大温度梯度是在靠近燃烧室壁面大约０．５ｍｍ的区域内。本文的实验结果,为分析柴油机压缩过程缸内传热过程提供了依据;所使用     

Three‐Dimensional Shape Reconstruction System Based on Fiber‐Optic Interference Fringe Imaging

In this article, we describe a three‐dimensional shape reconstruction system based on the Mach–Zehnder interferometer structure and Young's double pinhole interference principle, while utilizing Fresnel reflection on fiber end face and interference at the fourth port of 3‐dB coupler to achieve closed‐loop precise control of fringe phase. A root‐mean‐square phase stability of 4 mrad is measured with the system. The shape of the object is determined by analyzing the fringe pattern. A new algorithm called rotating rectangular window autoselection is used as the band‐pass filter. The measuring time of the whole system is less than 200 ms, and the error of system is 0.27 mm. Meanwhile, the overall complexity of the measuring algorithm is O(n log n).     

Vibration-compensated interferometry system using phase-modulating interference fringe subdivision technology

An innovative vibration-compensation method, with phase-modulating interference fringe subdivision technology, is described. It simulates fringe movement by the phase difference of signals and can detect the fringe movement with an accuracy of 1/400 fringe spacing using this subdivision technology. A closed-loop vibration-compensation system is built, and the measurement of an interference fringe movement and a vibration-compensation test are successfully demonstrated. Because of this new method and a new feedback algorithm that was introduced, interference fringes can be stabilized at any preset phase position in real time. Compared with known methods, this method is simple and inexpensive, as well as effective.     

Statistical analysis of a scatter plate interferometer

A scatter plate interferometer is analyzed based on the principle of statistical optics for what is to my knowledge the first time. It is shown that the optical complex amplitude distribution of scattered-direct light that is scattered by the first scatter plate and transmitted through the second scatter plate is equivalent to the distribution of direct-scattered light that is transmitted through the first scatter plate and scattered by the second scatter plate if there are no aberrations in the tested optical elements. Then the mechanism producing interference fringes and fringe contrast are discussed by means of a statistical method. It is shown that the fringe pattern depends on the correlation of the transmittance distributions of the two scatter plates and the aberration of the tested lens. The analysis coincides with experimental phenomena. The method used gives a new viewpoint on the principles of scatter plate interferometry and reveals its statistical nature.     

Reversible interference fringe counter with a small measurement range

Conclusions On the basis of the above work we assembled an apparatus with an interference fringe counter which had a range of 50 fringes and a precision down to one interference fringe. The utilization of a single-stage photomultiplier type FÉU-2 made it possible to produce a counter which has a small measuring range and does not require a high voltage source. The displacement of one interference fringe system with respect to the other by half a period was attained, owing to the small number of fringes, by a simple adjustment of the slit positions. The electronic unit can also be used for measuring larger displacements, provided the number of counting cells is increased and the interference fringes fed to the photomultiplier have a sufficient brightness and contrast.     

High-resolution two-dimensional angle measurement technique based on fringe analysis

A novel angle-measurement technique based on fringe analysis for phase-measuring profilometry is proposed. A two-dimensional (2-D) angle between two mirror surfaces is determined by least-squares fitting of a plane to the 2-D distribution of the phase difference introduced by the 2-D tilt angle. To evaluate the performance of the proposed technique, numerical simulations that use the Fourier-transform technique and the phase-shift technique for fringe analysis were performed, and the results are compared. A 2-D angle-measurement interferometer based on a Mirau interference microscope was developed that demonstrated the validity of the proposed principle. It is shown by simulation and experiment that the proposed 2-D angle-measurement technique can achieve both a wide measurement range and a high angular resolution simultaneously.     

Microinterferometry: Three-Dimensional Reconstruction of Surface Microtopography for Thin-Film and Wetting Studies by Reflection Interference Contrast Microscopy (RICM)

We present an improved theory of image formation by reflection interference contrast microscopy (RICM) for structural studies of stratified films on planar substrates and propose a new theoretical approach to analyzing the surface profile of nonplanar films. We demonstrate the validity of the new approach by analyzing the fringe patterns of RICM images from wedge-shaped liquid films and spherical probes. By simulation of various scenarios, we study the effect of finite-aperture illumination and the shape of the nonplanar interface on the interference fringe pattern of RICM images. We show how the reconstruction of the microscopic topography of the sample from the fringe spacing is corrected by angular and curvature correction terms. We discuss the variation of the mean intensity of the fringe patterns and the decay in the fringe amplitude with increasing fringe order that is caused by nonplanar interfaces of different slope.     

Coherence-multiplexed fiber-optic sensor systems for measurements of pressure and temperature changes

A digital demodulation method for read-out of phase changes induced in coherence-multiplexed sensors based on highly birefringent fibers is described. The method employs the fringe counting principle and enables registration of the phase shifts simultaneously induced in two multiplexed sensors with a maximum frequency of 10 kHz and resolution of 1/4 of the interference fringe. The performance of three multiplexed systems interrogated using the proposed detection method is investigated. The first system is composed of two serial multiplexed sensors serving for measurements of pressure and temperature changes in the same location, while the two other systems are composed of two parallel or serial multiplexed temperature-compensated sensors serving for pressure measurements at different locations.     

基于多项式拟合的条纹图象处理方法

根据干涉场的条纹灰分布规律,对条纹图象进行处理。用多项式对条纹数据进行拟合,提高了条纹提取的速度和精度,同时也起到了噪声抑制的作用。用求极值的方法确定每次采样条纹中心点的位置,再把所有的中心点组合起来表示条纹的形状,从而达到提取条纹的目的。     

光纤干涉仪条纹动态测量技术

针对光纤干涉仪条纹的CCD动态测量技术,分析了限制条纹最大允许移动速度的因素,提出了采用中值滤波提高信号处理速度的方法。在条纹移动速度成指数增长时,实验观察了条纹位移测量值的变化情况,并进行了中值滤波实验。结果表明,条纹的最大允许移动速度除受CCD的场频和信号处理时间影响外,还与干涉仪使用的光源波长和光纤直径以及两光纤间的距离有关;中值滤波可以缩短信号处理时间,同时获得较好的滤波效果。     

Certification of specimens for checking profilographs and profilometers

Conclusions By studying the problems related to certifying specimens which have regular profiles and are intended for checking contact profilographs and profilometers of the M system it is possible to arrive at the following conclusions.In the case of the visual interference method for measuring heights, which is used for certifying specimens with a profile of a simple shape formed by straight-line segments, the measurement errors produced by superposing subjectively the sighting line of a reading device over an interference fringe are determined mainly by the interference field parameters (the visible width of an interference fringe and the luminance function in the contour-shaping area). Measurements with a minimum error correspond to visible fringe widths of 0.03–0.06 rad (under normal conditions).The angle between the profile elements can be measured by means of the interference method independently of the relative position of the reference plane when =0.Profilograms with an absolute and independent scale can be obtained for profiles of a complex shape by means of a photoelectric interference scanning system.In this system the profile elements' recording errors can be analyzed by means of the profile linear approximation method by representing the screen-emitted luminous flux in the form of a Fourier series of spatial frequencies.For the majority of the specimen's regular profiles the error which can be tolerated in practice for transmitting the shape of profile-approximating elements occurs when the ratio between the interference fringe width normal to the scanning trajectory and the size of the screen components is equal to ten. The raising of this ratio does not provide a substantial reduction of the error.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 24–28, February, 1969.     

Determination of the axial velocity component by a laser-Doppler velocity profile sensor

We report about the determination of the axial velocity component by a laser Doppler velocity profile sensor that is based on two superposed fanlike interference fringe systems. Evaluation of the ratio of the Doppler frequencies obtained from each fringe system yields the lateral velocity component and the axial position inside the fringe system. Inclined particle trajectories result in chirped burst signals, where the change of the Doppler frequency in one burst signal is directly related to the axial velocity component. For one single tracer particle it is possible to determine (i) the lateral velocity component, (ii) the axial velocity component including the direction, and (iii) the axial position of the tracer trajectory. In this paper we present the measurement principle and report about results from simulation and experiments. An uncertainty of the axial velocity component of about 3% and a spatial resolution in the micrometer range were achieved. Possible applications of the sensor lie in three-component velocity measurements of flow fields where only one optical access is available.     

Determining small angles of beam splitter rotation in optical vortex shearing interferometer

It is suggested to use a singular beam of unit topological charge in a scheme of vortex shearing interferometer intended for the observation of isoclinic fringes. In the interference pattern, the regions of fringe splitting determine the localization of wavefront dislocations and exhibit a shift that depends on the beam splitter rotation angel. Using the proposed method, it is possible to evaluate small angles of beam splitter rotation with an accuracy determined by the interference fringe width.