Extension of the controlled sensitivity range in holographic interferometry with a lateral shear

The possibility of controlling the measurement sensitivity in shearing interferometry with a small lateral shear is considered. A method based on recording several holographic interferograms with different magnitudes of lateral shear and with different carrier frequencies of holographic fringes during a single exposure is proposed. The measurement sensitivity of the interference patterns is controlled at the stage of optical processing of the combined holographic interferograms with lateral shear, when the interferograms are illuminated by two coherent light beams and the filtering of the corresponding diffraction orders is performed. The results of the experimental testing of the proposed method by using it for the visualization of the melting zones of planar polymethylmethacrylate samples under heat treatment are presented.     

Highly sensitive comparative analysis of periodic structures using lateral shear interferometry

The promising character of application of large lateral shear interferometry for the comparative analysis of a pair of transmission periodic structures, one of which is the structure under study and the other is the standard structure, is shown. For increasing the sensitivity of the representation of differences in the behavior of grooves of the structure under study and the standard structure, it is proposed to use higher order diffraction interference for both structures. Results of experimental testing of the method for monitoring the quality of production of two-dimensional amplitude masks are given.     

Interferometry for measuring large aspherical surfaces with holographic optical elements

Interferometry for measuring the shape of large aspherical surfaces is reported. The interference fringe pattern between the parallel reference beam and the reconstructed wavefront from the master zone plate which is drawn by an electron-beam drawing machine is recorded on a hologram plate with off-axis optical arrangement. The hologram plate used as the standard element is reconstructed by the conjugate beam in a modified Twyman-Green interferometer. Insufficient parallelism of commercial hologram plates can be compensated by this method. It is also easy to make replicas. Some experimental results are also presented.     

基于平移旋转的球面绝对检测技术仿真分析

基于平移旋转的球面绝对检测技术是一种实现高精度面形测量的有效手段。通过绕光轴多次等角度旋转被测球面测得被测面面形误差的旋转非对称部分,并由共心平移被测球面恢复出被测面面形误差的旋转对称部分,合成即可得到被测球面完整的面形信息。详细推导了平移旋转法的理论公式,并进行了仿真分析。仿真结果表明,基于上述方法获得的被测球面面形误差与初始面形误差残差图的均方根值为5.300 010-12 nm,其与初始面形误差均方根值的比值为1.164 110-12,理论误差极小,满足高精度面形检测要求。     

横向剪切干涉的波前重构新方法

 在常规横向剪切干涉仪的基础上,利用波前周期延拓的假设,基于小波变换的方法实现了波前重构。这种波前复原实现了光滑波前的快速重构,并且能够较好地快速重构非模式波前。数值模拟表明,该方法对波前复原的精度优于常规多项式拟合方法。利用该方法在不均匀介质对波前的扰动的测量重构表明,重构波前比常规多项式拟合重构波前合理。     

透镜初级球差的横向剪切干涉条纹研究

利用玻璃平行平板构成简单的横向剪切干涉仪可以观察到单薄透镜形成的准直光束的剪切干涉条纹,由干涉条纹分布求出对应的几何像差和离焦量.用焦距为190 mm的单薄透镜做实验,实验结果与计算机模拟结果符合,说明可以从剪切干涉条纹的分布求出透镜的轴向调整误差和初级球差.     

含非球面光学系统多功能光学设计程序

本FORTRAN程序普适于球面和含有非球面的光学系统.用它可在微机上完成包括自动设计和OTF计算在内的全部设计过程.自动设计子程序贯穿了复合优化思想;提出了新的病态处理方法;实现了自动设计与OTF评价的方便结合,与传统设计手段的方便结合.     

剪切干涉灵敏度和剪切图的全处理方法的研究

本文对剪切干涉灵敏度进行定量讨论,首次提出平均灵敏度数学模型,它圆满地解释了剪切干涉特性.通过讨论得出一个重要结论,要准确求出待测波面,必须用变剪切干涉仪,使用不同的切量对同一波面进行测量.然后采用一种新方法——剪切干涉图全处理的方法,求出待测波面.     

A differential method for calculation of aspherical surfaces using polynomial approximation

A simple method is described for the correction of the spherical aberration using one aspherical surface represented by a polynomial approximation. The same principle is useful for the design of aplanatic systems containing two aspherical surfaces.Finally, the author wishes to convey his thanks to Mr. J. Vondich (Institute of Physics, Czechoslovak Academy of Sciences) for performing the calculations.     

Visualization and interferometry for cylindrical and spherical sample tomography and profilometry

A technique combining image processing and laser interferometry for visualizing and detecting the deformation of transparent cylindrical and spherical sample is proposed. This deformation includes geometric deformation such as volume transition in profilometry and physical deformation such as refractive index change in tomography. Phase contour lines are used for quantitative analysis and graphical representation of the deformation. This method allows us to visually detect the spatial variation of the deformation field and to evaluate the test quality such as misalignment of optical system. A theoretical analysis using phase contour map to characterize the deformation field is described in detail. A method using phase contour map to qualify the interferometric test is proposed. Analysis of test examples is carried out. Suggestions on using phase contour line method to ameliorate test system design are finally discussed.     

Flexible interferometry for optical aspheric and free form surfaces

Optical Review - A flexible interferometry is proposed to test concave optical aspheric and free-form surfaces. It employs a flexible aberration generator (FAG) consisting of a movable reflective...     

Holographic interferometry of phase objects by recording lateral shear holograms on two carriers placed in series

Techniques for recording a pair of lateral shear holograms at a time on two carriers arranged one after the other are considered. Resulting interference patterns are variable-sensitivity images of phase changes induced by the object. The techniques were tested in experiments with planar poly(methyl methacrylate) samples subjected to heat treatment. Interference patterns confirming the efficiency of the techniques in studying fast processes are presented.     

A holographic,radial and lateral shear interferometer

A new holographic shear interferometer is described in which both the radial and the lateral shear can be simultaneously introduced by using an off-axis zone plate.     

Ultrasonic interferometry for the measurement of shear velocity and attenuation in viscoelastic solids

A method for the measurement of the shear properties of solid viscoelastic materials is presented. The viscoelastic material is cut into a cylindrical sample which is clamped between two rods. The transmission and reflection coefficient spectra of the fundamental torsional mode through the sample are measured by means of two pairs of piezoelectric transducers placed at the free ends of the rod-sample-rod system. Such spectra exhibit maxima and minima which occur approximately at the resonance frequencies of the free viscoelastic cylinder. Therefore, the shear velocity can be obtained by measuring the frequency interval between two consecutive maxima or minima. The shear attenuation is derived by best fitting the analytical expression of the reflection and transmission coefficients to the experimental spectra. The test is very quick to set up as the sample is simply clamped between the two rods.     

Holographic lateral shearing interferometry with the displacement of an object under study

A new method of the holographic lateral shearing interferometry is considered. In the method, the recording of the reference holographic lateral shear interferogram is followed by the displacement of an object under study by a distance equal to the lateral shear. The method provides the simultaneous recording of several aberration-free interference patterns representing with the different sensitivity the changes in the phase of the light wave, introduced by the object under study. The method has been tested experimentally to detect optical inhomogeneities in a cylindrical crystal of the active medium of a solid-state laser.     

Modal wavefront reconstruction for radial shearing interferometer with lateral shear

In a radial shearing interferometer, a portion of the test beam is magnified and used as the reference for the tested wavefront. However, the reference portion is always off center (lateral shear), which complicates the wavefront reconstruction. A modal method for solving this problem is presented here. This method uses orthogonal Zernike polynomials and its matrix formalism to calculate the Zernike coefficient of the wavefront under test. This approach has easier implementation, is better filtering, and has a more adaptive practical situation. The corresponding mathematical formula is deduced, and a computer simulation is also made to verify operation of the algorithm. The result of simulation analysis shows that the proposed method is correct and accurate.     

横向剪切干涉中剪切量的选取及分析

横向剪切干涉技术是一种直接测量波面相位分布的光学测量方法,由于其不需要高精度的参考平面,并且能够测量偏离量较大的表面面形偏差,因此得到了更为广泛的应用。但是,通常情况下剪切量大小的选择凭工作经验来确定。为了给出一种定量的剪切量判定方法,论文提出了一种基于Zernike多项式拟合的剪切量判定方法,通过计算机仿真和实验给出了剪切量与测量误差的关系,发现剪切量为测量口径1/10时即可达到良好的测量结果。     

Simultaneous measurement of several near-parallel surfaces with wavelength-shifting interferometry and a tunable phase-shifting method

Wavelength-shifting interferometry can distinguish in frequency space interference signals from different surfaces, and therefore allows the measurement of optical thickness variation between several quasi-parallel surfaces of a composite transparent object. Frequency analysis of the signal spectrum with a tunable phase-shifting formula can then detect the phase of the individual signals. We have devised a tunable phase-shifting method which uses a freely adjustable number of intensity samples and can be adapted to any frequency spectrum. To extract the signal reliably, two properties of the phase-shifting method are particularly important: it should suppress cross-talk from unwanted frequencies, and it should allow for some variation in the signal frequency. We show that a carefully designed sampling function envelope will combine these benefits, and demonstrate the technique in measurements of three different composite objects each consisting of three reflecting surfaces. The importance of phase-shift linearisation is discussed, and methods for selecting optimal set-up parameters are given.     

Casimir energy calculations for Chern-Simons surfaces and dielectric plates within the formalism of lattice quantum field theory

A new method based on the Monte Carlo calculation on the lattice is proposed to study the Casimir effect in the noncompact lattice QED. This method can be used for Chern-Simons surfaces (thin metal films) and for dielectric plates.