Improvement of the sensitivity of measurements in the formation of holographic interferograms of wedge plates

We consider the method for improving the sensitivity of measurements in the formation of aberration-free interference images of wedge plates, which do not require a priori knowledge of the position of the wedge edge. It is shown that the sensitivity in the measurement of the wedge angle in real time interferometry is doubled in the case of recording on the reference hologram of the wedge plate followed by its reconstruction by the object light wave that has passed through the wedge plate rotated through 180° relative to the normal. It turns out that recording of a pair of holograms of the wedge plate, one of which is the image of the wedge plate turned through 180° relative to the normal to the plate, makes it possible to increase the sensitivity of measurements by more than an order of magnitude by eliminating the systematic components of measuring errors due to complete compensation of aberrations. The results of experimental testing of the method are considered.     

Interferometric method to measure and test the optical homogeneity of transparent materials

The main idea of the method is to eliminate physically the influence of errors of glass sample plane surfaces on the wavefront transmitting through the sample. This makes it possible to reveal the “pure” optical inhomogeneity of the material independently of the errors of flat surfaces of a glass sample made in the form of a plane-parallel plate or a wedge of the small refractive angle. A basic optical layout of the laser interferometer explaining the capabilities of the practical application of the method is presented.     

Wedge plate interferometry: a new dual field configuration for collimation testing

A method of deriving a dual field fringe pattern from a single wedge plate for collimation testing is presented. The proposed technique uses a wedge plate and a 90° prism retroreflector to form two interference fields. With the two sets of fringes, the technique provides twofold increase in sensitivity and has its own reference.     

光电相位检测技术测量楔角

介绍用莫尔偏折术及电子外差读数技术测量楔角的方法,并给出楔角计算公式。该方法引入的测量误差约为1％,且它适于小角度测量。     

A Fourier transform speckle method to determine the change in angle of illumination

It is analytically shown that the position of the Fourier transform of the speckle pattern produced by a coherently illuminated, diffusely reflecting surface depends upon its angle of illumination. A method is proposed to measure small changes in this angle by doubly exposing the photographic plate with the original and laterally displaced Fourier transforms of the object speckle. The method is well suited for accurate measurements of the wedge angle and tilt of optical surfaces and to determine variations in refractive index or temperature of axially symmetric phase objects.     

Polarization Mixing Error Reduction in a Two-Beam Interferometer

A simple method to reduce the polarization mixing in a two-beam interferometer is proposed. A small separation angle Wollaston prism and an optical wedge were added to the conventional heterodyne setup. It was experimentally demonstrated that the polarization mixing error was reduced below 52.4 mrad by this method.     

Highly sensitive interferometric testing of deviation of the wedge angle of transparent plates

To improve the accuracy of the interferometric method of testing the wedge angle of a transparent plate, we propose using nonlinear recording of holograms of the reference and tested plates on different carriers and creating interference patterns that map the deviation of the angle, using higher orders of light diffraction on the holograms, with improved sensitivity. The increasing accuracy of the interferometric method of testing is provided by waves diffracted on holograms of the reference and tested plates in higher diffraction orders. Results of experimental testing of the method are presented.     

碳离子束射程快速验证方法的蒙特卡罗模拟研究

可通过楔形装置把离子束(质子和重离子)纵向上的的深度剂量分布转换成横向上的剂量分布,进行离子束射程的快速测量及验证。本工作通过基于GEANT4内核的GATE蒙特卡罗模拟平台,模拟计算了不同能量碳离子束在用于制作楔形装置的铜、铝、铁和有机玻璃等材料中的深度剂量分布,得到不同能量碳离子束在不同材料中Bragg峰位所处深度与能量之间的关系;模拟计算了不同能量碳离子束穿越单楔板、双楔板和大小组合楔板等楔形装置后横向上的剂量分布,得到了横向剂量峰值出现位置与碳离子束射程之间的关系。本文蒙特卡罗模拟研究为进一步开发重离子治疗当中的射程快速验证方法与设备奠定了坚实的基础。     

Smoothing the side lobes of a focused pattern by spectral dispersion in the broadband laser

Starting from the Huygens–Fresnel diffraction integral, the propagation equations of a broadband laser passing through a dispersive lens and a dispersive wedge are derived. Smoothing effect on the side lobes of the focused pattern is achieved as the broadband laser passes through the lens because of the spectral dispersion of the lens. By inserting a dispersive wedge behind the lens, better smoothing effect is realized because a relative position shift between focused patterns of different frequency components is generated due to the spectral dispersion of the wedge. Smoothing effect on the side lobe is obtained even with small bandwidth of the broadband laser as the wedge is used.     

Stagnant waves in an elastic wedge-shaped plate

Stagnant antisymmetric waves in an elastic wedge-shaped plate were studied theoretically and experimentally. The solution to the nonuniform problem was obtained in the approximation of a small and smooth field nonuniformity. The vibration amplitudes in a standing wave were calculated and measured for a small wedge angle. Experimental measurements were performed on an original setup.     

Imaging properties of a tetra wedge readout

The decoding principle of a tetra wedge anode, which is a development of the wedge and strip anode, is described. The influence of charge cloud size on decoding accuracy is studied using the Monte Carlo method. Simulation results show that the decoding error is large when the size of charge clouds collected by the anode is small. Thus, the charge clouds collected by the tetra wedge anode should reach a necessary size to ensure accurate decoding. Finally, using the ultraviolet photon counting imaging system, the linearity and the spatial resolution of the system are tested. Experimental results show that the system has a good linearity and the spatial resolution is better than 100 μm.     

Study of temperature fields in a rectangular plate with a temperature-dependent internal source with the aid of fast expansions

The approximate analytic solution of the problem of temperature field in a rectangular plate with an internal temperature- dependent source is obtained by the method of fast expansions. The critical value of a parameter characterizing heat release, which fundamentally affects the analytic solution form, is found. The maximum solution error is shown to amount to 0.02 at the consideration of the first three terms of the Fourier series in fast expansion. Temperature fields are presented, and an analysis of the influence of the plate sizes and the heat release magnitude on their formation is given. Recommendations on the plate shape choice are given.     

Synchrotron X-ray study of the q-fold quasicrystalline symmetry of the smectic C twist grain boundary phase (TGBC)

We report the first X-ray scattering investigation of spatial variations of the q-fold quasicrystalline symmetry (so-called commensurability) of well-aligned samples. A spatial resolution of was achieved using the ESRF microfocus beamline. The liquid crystal samples, contained between glass plates which were either parallel or in a wedge geometry, were scanned in order (i) to probe the mosaicity and (ii) to continuously change the balance between surface and volume effects. In the case of parallel plate cells, commensurability was observed everywhere throughout the sample, hence ruling out possible effects of mosaicity to explain the q-fold symmetry of the diffraction patterns previously reported when probed with a spatial resolution of mm² in rotating anode experiments. In the case of wedge cells, the evolution of X-ray patterns with thickness suggested that commensurate lockin occurs for sufficiently thick samples with a width that is statistical. Received 18 January 1999     

等光程干涉仪中参考镜楔角最优补偿方式研究北大核心CSCD

在测量多表面平行样品时,多面干涉会影响测量结果。为了能改善多面干涉问题,介绍了等光程干涉仪,并研究了参考镜楔角的最佳补偿方式。在等光程干涉仪中,由于参考镜和分光镜的楔角和倾角的存在,测量结果中会带有回程误差。根据参考镜楔角的不同情况采用了不同的补偿,理论分析并确定了各种补偿的放置方式和补偿量,同时研究了倾角和楔角的大小对于要被遮拦光束高度和像方数值孔径NA的影响。再利用Zemax进行不同补偿方式下的干涉仪仿真,并根据仿真得到的干涉图PV值分析回程误差的大小。分析表明:选用最佳补偿方式,参考镜楔角为1′,回程误差优于0.003个波长。     

Photoelastic stress pattern analysis using Fourier transform with carrier fringes: influence of quarter-wave plate error

The Fourier transform method, widely applied in photomechanics for the automated analysis of interferometric fringe patterns, has been recently extended to the photoelastic isochromatic fringe patterns analysis. Unfortunately, its use in photoelasticity involves some limitations that have not been completely highlighted in literature. This work deals with the influence of the quarter-wave plate tolerance on the evaluation of the retardation. Both theoretical and experimental analyses have shown that the quarter-wave plate error does not affect the retardation only if the principal stress directions in the model and in the carrier are aligned. In general, instead, the tolerance of the quarter-wave plates leads to an amplification of the retardation error due to the influence of the isoclinics with a subsequent restriction of the field in which the method can be applied. For instance, using common quarter-wave plates and tolerating a maximum retardation error of about 0.03 fringe order, than the Fourier transform method cannot be applied as a full-field technique but only in the model zones in which the misalignment between the principal stresses in the model and in the carrier is less than 15°.     

微楔形镜加工技术研究

微楔形镜的加工不能像平行平面元件那样,采用大块抛光,切片分割的办法。针对零件尺寸小、精度要求高的特点,研究了加工过程中的粘结上盘、面形精度控制和楔形角检测等技术,设计了吸附式粘结上盘和楔形角测量等专用装置,应用于尺寸为3×3×1mm(6°)的Nd∶YVO4(掺钕钒酸钇)晶体批量生产中,提高了零件的面形精度和加工可靠性。测试结果表明:面形精度优于λ/10(λ=632.8nm),表面光洁度达0/0级,楔形角合格率达98%以上。     

Lamb wave radiation from plate termination in a liquid

The liquid wedge method is used to excite leaky Lamb waves on an aluminium plate while the plate is immersed in water. The excitation occurs near the end of the plate so that sonic energy of the excited mode radiates into the liquid. A Schlieren method is used to observe the radiation pattern and a correlation is made between the radiation lobe structure and the symmetric or antisymmetric nature of the excited mode. Theoretical calculations of the transfer of energy from the plate to the liquid are made and agreement between theory and experiment is obtained.     

电桥法测杨氏模量的实验研究

本文引入了电桥法测量杨氏模量,用自制平行板电容器对传统的实验装置进行改进,用电容的变化来表征微小位移的变化,通过实验原理、误差分析,结合测量结果,由此给出了一种测量杨氏模量的新的方法.     

Smoothing effect in the broadband laser through a dispersive wedge

The propagation expression of a broadband laser passing through a dispersive wedge is derived on the basis of the Huygens-Fresnel diffraction integral. Smoothing effects caused by the phase perturbation of the dispersive wedge on the intensity profiles are investigated in detail. The phase perturbation of the dispersive wedge induces a relative transverse position shift between the diffraction patterns of different frequency components. The relative transverse position shift is of great benefit to the fill of the intensity peaks of some patterns in the valleys of others when these patterns are overlapped and thus the smoothing effect is achieved.     

Nonuniform elastic stagnant wave in a wedge-shaped plate

An acoustic field near the edge of an elastic wedge-shaped plate is studied. The field is represented in the form of two counterpropagating nonuniform waves. The standing vibration profiles varying with distance to the edge are constructed. A specific acoustic effect arising when the wave moves away from the wedge is revealed. Theoretical results are confirmed by measuring the standing wave amplitudes with a proprietary setup.