Simple real-time 3-D displacement measurement by fringe analysis using a photorefractive interferometer

A simple 3-D displacement measurement method using a photorefractive interferometer is proposed and experimentally demonstrated. A photorefractive crystal attached to the sample under test is used to record an original spherical wave that provides a shifted reconstructed wave after displacement. The shifted wave interferes with direct wave to form an interferogram. By analyzing the fringe pattern the in-place and out-of-place displacements can be determined at the same time. This method works in real-time and is easy to operate with adequate accuracy comparable with or even better than that of other techniques.     

用迈克尔逊干涉仪测量全息干板膜厚度

全息干板膜的厚度是全息干板的重要参数之一。使用迈克尔逊干涉仪和白光光源对2种全息干板膜厚度进行测量，并对测量结果误差进行分析，给出了测量误差与膜厚及折射率之间的关系以及此方法的适用范围。研究结果表明：在膜厚从8μm增至41μm的过程中，测量结果的绝对误差≤2μm且变化很小，相对误差则从14.1%降到了2.2%。随着膜厚的增加，相对误差明显降低；折射率n也参与了误差传递，其值与测量误差呈类似反比关系；当n值在1.5附近时，为保证测量的准确性，所测膜厚≥40μm。最后指出，迈克尔逊干涉仪在测量全息干板膜等较厚的薄膜时，具有测量范围大，结果较准确等优点。     

Photothermal modulation of laser diode wavelength: application to sinusoidal phase-modulating interferometer for displacement measurements

In this paper, a novel laser-diode (LD) sinusoidal phase-modulating (SPM) interferometer, which utilizes a photothermal technique for LD wavelength modulation, is proposed to measure displacements with a nanometer accuracy. In conventional LD–SPM interferometers, the LD intensity modulation is concurrent with the wavelength modulation, which increases measurement errors. Using the photothermal technique, the LD wavelength modulation can be accomplished with negligible concomitant intensity modulation, and the measurement errors are thus eliminated. The computer simulations and experiment results verify the usefulness of this novel interferometer.     

利用等厚干涉条纹测量微光的调制传递函数MTF

通过对微光的调制传递函数 (MTF)的讨论 ,结合传统的“分辨率板法” ,提出了一种新的测量微光的MTF的方法。该方法直接从MTF的物理含义出发 ,利用迈克尔逊干涉仪产生一系列空间频率的等厚干涉条纹来模拟分辨率板的作用 ,在计算机的控制下 ,自动测量出连续的MTF曲线。给出的实验光路和实验结果表明 ,利用干涉条纹测量微光的MTF是一种可行的简便方法 ,在计算机的控制下 ,可快速完成夜视仪的传递函数测量     

波带板法检测非球面技术

总结了在波带板干涉技术检测非球面方面最近的发展和应用，比较了不同方法的优缺点。叙述了用一块改进型波带板检测非球面的原理和方法。还分析了波带板的安装与测量精度的关系。针对干涉条纹在周边弯曲的现象，对波带板的设计进行了改进。最后给出了实验结果。     

A laser interferometer for measuring straightness

This paper proposes a laser interferometer for determining the straightness of a moving stage. The optical setup is described and the theory is derived. The results show that this interferometer not only overcomes the disadvantages of the conventional interferometers but also provides a higher sensitivity. Two experiments were carried out in this research. The first experiment verifies the validity of the theoretical derivation. The second experiment demonstrates that this interferometer could be adopted for straightness measurements.     

A new method for angular displacement measurement

We describe a new method for angular displacement measurements that is based on a Fabry-Perot interferometer. A measurement accuracy of 10-8 rad is obtained by use of the sinusoidal phase modulating interferometry. Another Fabry-Perot interferometer is used to obtain the key initial angle of incidence.     

用于位移精密测量的光外差马赫-泽德干涉仪

本文介绍了我们研制的用于位移精密测量的光外差马赫－泽德干涉仪。由于在光路设计中采用了共光路的布置，共模抑制技术得以实现，环境干扰产生的噪声得到很好的消除，相位检测的稳定性和精度大大提高。使用该干涉仪测量了一台在光学相移器内ＰＺＴ微位移驱动装置的电压－位移关系。测量结果具有良好的线性和重复性，与预期相符。根据测量数据分析，该光外差干涉仪具有３ｎｍ的位移测量精度。     

Zygo interferometer for measuring refractive index of liquids and its application for heavy water analysis

The Zygo interferometer for measuring refractive index of liquids such as heavy water is presented. The accuracy of measurement in the refractive index of liquids is found to be ±0.0002 in the Zygo interferometer. An application of Zygo interferometer for heavy water analysis is also presented. The interferometer is found to be useful for determining the percentage purity of heavy water with an accuracy of ±5% in the purity range of 0–100%.     

A modified moiré interferometer for three-dimensional displacement measurement

This paper presents a new optical interferometric system, MMI-T/G, composed of a modified four-beam moire interferometer and a Twyman/Green interferometer. The MMI-T/G system can measure threedimensional displacement fringe patterns with a single loading on the specimen, and the in-plane and out-of-plane displacement fields can be measured independently and defined clearly. The optical setup has the advantages of structural novelty, flexibility, and high fringe contrast. Moreover, the in-plane displacement sensitivity is twice of that of the normal moire interferometer. The measuring techniques to obtain the fringe patterns and displacement fields using the MMI-T/G system axe described. The experimental results of thermal displacement of an electronic device are shown.     

激光干涉数字化角度计量系统分析

通过对数字干涉测角系统的组成、原理、误差、精度等方面的阐述与分析介绍了一种新型的精密角度测量系统。该系统是基于激光干涉技术的一种角度测量系统 ,系统以激光作为干涉光源 ,迈克耳逊干涉仪作为角度量测量的核心装置 ,通过机械装置将角度 (角位移 )量转换为迈克耳逊干涉仪干涉光路中可反映光程差变化的线位移量 ,进而反映为干涉条纹的变化 ,最后通过有关电路对干涉条纹进行的一系列处理 ,实现了对大转角的精密测量。还就上述有关问题用计算机模拟的方法作了定量分析     

Design of a wedge plate for polarization-preserving angular shifter

It is shown that by using a wedge plate, the incident direction of light propagation can be rotated as necessary while still preserving beam polarization. The basic conditions of these preservations of polarization are deduced. For numerical demonstration, it is shown that a collimated beam with +45° linear polarization can be guided to any pre-settled direction where the square of ellipse ratio variation in the polarization is less than 0.0001%, while the variation of squared ellipse ratio of a right circular polarization beam is kept under 0.1%.     

Hybrid fiber interferometer for simultaneous measurement of displacement and temperature

A hybrid fiber interferometer sensing configuration for displacement and temperature measurements is proposed and experimentally demonstrated that is constructed by splicing a short section of polarization maintaining optical fiber to an end-cleaved single mode optical fiber with a tapering structure. The reflected spectrum changes with the variation of displacement and temperature. The sensing configuration uses the method of wavelength and intensity modulations for displacement and temperature measurements, respectively, to which the sensitivities are 0.01392 nm/μm, 0.0214 d Bm/μm,-0.09136 nm∕°C, and 0.15795 d Bm/°C. Experimental results show that displacement and temperature can be measured simultaneously by demodulating the reflected spectrum.     

空气中被动声定位系统定位精度分析

本文对影响被声定位系统定位精度的几种因素进行了比较全面及深入的分析。推导出了测时差定位系统在均匀煤质和非均匀媒质中一些因素对定位精度影响的公式；给出了误差曲线；得出了一些有益的结论并提出了提高定位精度的几种方法。     

Refraction in plane-parallel plate—Reconsideration of method of measurement of refractive indices

The prism (minimum deviation) method of measurement of refractive indices in solids has a couple of disadvantages including problems associated with manufacturing of a good prism itself. Besides this method is unsuitable to be used in piezo- and electro-optical experiments when one needs to achieve so-called homogeneous distribution of an interaction (electric field, stress, strain) within the sample. Besides, worked out with a large expenditure of energy and cost, the prism is usually useless in other applications (destructive method). Therefore, an “elder” method of measurement of refractive indices by measuring shift of the refracted beam of light in a plane-parallel plate has been reconsidered in this paper. The sample itself may be a cuboid (if one wishes to measure all of three principal refractive indices in optically biaxial crystal), or just a crystalline boule in which one is cutting off the conical and tail parts and by suitable mechanical treatment (lapping and polishing) reveals a pair of plane parallel surfaces properly oriented to crystallographic (or principal axes of the optical indicatrix) directions. In such case, however, one can only measure one (isotropic crystals) or two (optically uniaxial crystals) refractive indices. However, in case of this method as opposed to the prism method one can repeat the measurement a couple of times, e.g. after a series of consecutive annealing, when this is either impossible or undesirable to cut the boule into smaller pieces prior to the final annealing (nondestructive method). The error depends on the angle of incidence and on sample (boule) thickness and is usually of the order of 0.001. However, in the future it is expected that the error can be reduced by implementing an electronic readout of the beam shift below 1 μm. Working of the method has been illustrated with a couple of examples in GdCOB (biaxial), LiNbO₃ (uniaxial) and YAG:Cr,Mg (isotropic) crystals.     

卡塞格林系统装调过程中高精度测角方法

为了能够准确测量同轴三反相机中次镜的倾斜量变化,提出一种新的角度测量方法,即用大口径干涉仪与经纬仪相结合进行测量。以主镜为测量基准,两镜相对倾角较小时,使用大口径干涉仪同时测量两镜的干涉条纹,相对倾斜角度过大时次镜无干涉条纹,加入一台经纬仪分别自准直于干涉仪和次镜,间接测量两镜相对夹角。通过模拟计算与实验验证表明,对于次镜组件倾角测量误差可以控制在0.5″以内。结果表明,该检测方法具有通用性强,测量精度高等特点,克服了传统检测方法测量精度不足的问题。     

Heterodyne interferometer for displacement measurement with amplitude quadrature and noise suppression

The high precision displacement measurement in nanoscale is crucial to many applications. We present a heterodyne interferometry with differential phase to amplitude conversion scheme for displacement measurement in nanoscale. In this approach, the differential phase introduced by the displacement is converted into the amplitudes of heterodyne signals in quadrature. Meanwhile, the heterodyne signals in phase quadrature are also achieved so that the displacement can be determined from the amplitude ratio of the quadrature signals, and the direction of displacement can be determined from the phase quadrature. Since the differential phase to quadrature amplitude conversion is achieved through the optical addition and subtraction by polarization tuning, which are based on differential detection concept. Thus the proposed method benefits from the features of differential detection with common phase noise and correlated amplitude noise rejection and that of quadrature detection with real time and wide dynamic range of phase measurement. To demonstrate the capability of proposed method in differential phase measurement, we measure the displacement drove by a commercially available PZT pusher and found close agreement between the experiment and the theory. The experimental evidence of noise suppression is also found with spectral measurements, which demonstrates the resolution of displacement measurement at 60 pm and minimum detectable differential phase of 5.6 × 10⁻⁶ rad/ over 50 kHz.     

平行板电容器演示实验装置的改进

介绍一种具有干燥、照明和充电系统的演示实验装置，该装置使平行板电容器在演示时能保持所带电荷基本不变。     

A displacement measurement system, utilizing a Wollaston interferometer

A dual interferometric displacement measurement system is presented where a Wollaston prism interferometer is employed in conjunction with a normal Michelson interferometer. The system operates without the use of external polarizers, apart from those associated with the Wollaston prism interferometer itself. It is shown that an optical path difference induced in the Michelson interferometer can be detected using the Wollaston prism in a normal interferometer arrangement. Further, the interference pattern produced by the Wollaston prism interferometer changes in a measurable, linear fashion as the optical path difference from the Michelson interferometer alters. A simple theoretical analysis of the system is presented and used to derive a computer model of the optical arrangement. Results from an experimental implementation of the system, using a Wollaston prism with a beam separation of 0.5 degrees and a superluminescent diode, of wavelength 825 nm, as a light source, are included and compared to the results from the computer model.     

小孔干涉仪滤波孔的研究

用惠更斯-基尔霍夫公式对小孔干涉仪的滤波孔进行计算及分析后指出:尽管滤波孔小于爱里斑,滤波孔的位置对参考波的质量仍有影响。在接收面上参考波位相有较大偏移处,往往伴有较大的光强变化(变弱)。给出实验结果,并进行了讨论。