Heterodyne angular interferometer using a square prism

An interferometer composed of a dual-frequency laser, sensing assembly, and decoding system is proposed for angular displacement determinations. The laser is a heterodyne light source. The sensing assembly generates an interference signal by the use of a square prism, and the decoding system extracts the phase difference of the interference signal. The theory, which reveals that the phase difference has a relation with the angular displacement of the square prism, of the interferometer is described. A setup constructed to realize the interferometer and the results of using this setup are then demonstrated and presented.     

Angular interferometer using calcite prism and rotating analyzer

An interferometer using a calcite prism and rotating analyzer is proposed for angular displacement determinations. The calcite prism senses the angular displacements and the rotating analyzer transfers the interference signals from dc-type into ac-type. Compact optical setup and using low-cost devices are thus the advantages of the interferometer. The theory of the interferometer is first demonstrated. A setup constructed to realize the interferometer and the results of using this setup are then presented.     

Shearing interferometer using low-coherent light source and calcite prism

A shearing interferometer using a low-coherent light source and calcite prism is proposed in this paper. The calcite prism is the shear plate that generates sheared wavefronts with optical-path difference induced only by the contour of the specimen. Low-coherent light source is thus available while the interferometer is adopted for contour derivative determinations. The design of this interferometer is introduced, a setup constructed to realize the interferometer is described, and the experimental results from the uses of the setup are finally presented.     

Sub-50 nm patterning by immersion interference lithography using a Littrow prism as a Lloyd's interferometer

We present a simple setup that combines immersion lithography with a Lloyd's mirror interferometer. Aiming for smaller structure sizes, we have replaced the usual Lloyd's interferometer by a triangular Littrow prism with one metal-coated side, which acts as a mirror. Because of the higher refractive index of the prism, the wavelength and, thus, the attainable structure sizes, are decreased significantly. Using a laser with a wavelength of 244nm, we could produce line patterns with a period of less than 100nm and a width of 45nm. The introduced setup retains all the advantages of a Lloyd's mirror interferometer, in particular the flexibility in periodicity.     

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.     

Broadband light source shearing interferometer using Savart plate and angular scanning technique

A shearing interferometer based on using broadband light source, Savart plate, and angular scanning technique is proposed for slope contour measurements in this Letter. Of which, the Savart plate divides the wavefront reflected from the detected surface into two laterally displaced ones, the interference pattern generated by the interference of the divided wavefronts is modulated by an envelope function, and the slope contour of the detected surface is determined by examining the shifting of the darkest fringe as the shear plate is angularly scanned. A setup for realizing the interferometer is constructed. The experimental results of using this setup agree the validity and feasibility of the proposed interferometer.     

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.     

Sorting and detecting orbital angular momentum states by using a Dove prism embedded Mach-Zehnder interferometer and amplitude gratings

An experimental system consisting of a Dove prism embedded Mach-Zehnder (M-Z) interferometer and two gratings was built to sort and detect orbital angular momentum (OAM) states of light beams. The helical beams with different OAM states were generated by propagating the fundamental-mode Gaussian beam through a spatial light modulator. The Dove prism embedded M-Z interferometer was used to sort helical beams with odd or even OAM number and two binary amplitude gratings were used to measure the OAM states. Sorting of coaxially-superposed coherent and incoherent helical beams with odd and even OAM states was realized in the experiment.     

Polarizing interferometer with constant radial and azimuthal shears

An interferometer is described in which a rotatable Wollaston prism is used to achieve constant radial and azimuthal shears in a converging beam. These displacements may have applications in speckle shearing interferometry for the deformation measurement of objects with axial symmetry.     

高精度六面体垂直度误差测量的一种新方法

介绍了一种利用波面干涉仪和精度为0.2″的端齿盘组合测量六面体相邻两面垂直度误差的新方法,建立了基于最小二乘算法的评定垂直度误差分布的数学模型,介绍了测量装置及测量实验步骤。该方法不但测量精度高,而且能够获得两个面之间垂直度误差分布数据,可用于六面体面体形位误差的高精度修形加工。针对精度为2″的标准直角棱镜的测量实验表明该方法测量结果可信,精度优于0.5″。可推广到其他多面体类零件形位误差的高精度测量。     

Downstream Fabry-Perot interferometer for acoustic wave monitoring in photoacoustic tomography

An optical detection setup consisting of a focused laser beam fed into a downstream Fabry-Perot interferometer (FPI) for demodulation of acoustically generated optical phase variations is investigated for its applicability in photoacoustic tomography. The device measures the time derivative of acoustic signals integrated along the beam. Compared to a setup where the detection beam is part of a Mach-Zehnder interferometer, the signal-to-noise ratio of the FPI is lower, but the image quality of the two devices is similar. Using the FPI in a photoacoustic tomograph allows scanning the probe beam around the imaging object without moving the latter.     

Remotely scanned multiphoton temporal focusing by axial grism scanning

A simple technique for remote scanning of the focal plane in temporal focusing multiphoton microscopy is demonstrated both theoretically and experimentally. A new on-axis light propagation optical setup design enables this scanning, which was considered not feasible in previous studies. The focal plane is axially displaced by the movement of a remote optical device, consisting of a double prism grating, and optionally a cylindrical lens. The displacement is linear, and its slope is inversely proportional to the square of the optical system's magnification.     

Coding of functions by classes for numerical simulation in hard X-ray optics

An advantage of implementation of object-oriented programming principles in numerical simulation in hard X-ray optics was considered. The suggested approach was demonstrated on the example of two-beam X-ray interferometer with the refracting prism. It was shown that the proposed coding technique significantly simplifies the main program code by reducing its size, as well as making it more readable and easily modifiable.     

Nulling interferometry by use of geometric phase

Nulling interferometry is a method of detecting a faint source near a bright one, in which destructive interference is realized for the light from the bright source. A nulling interferometer that makes use of geometric phase (Pancharatnam phase) is proposed. An experimental setup is constructed to simulate a stellar interferometer with geometric-phase modulation. We attained extinction of 6 x 10(-5) in white light.     

马赫-曾德尔光纤干涉仪型梳状滤波器优化计算

提出了一种具有方波形输出谱的级联马赫-曾德尔光纤干涉仪型梳状滤波器的优化计算方法。利用传输矩阵法将级联马赫-曾德尔光纤干涉仪的输出光谱表示为显式函数，采用独特的递推方法将理想的梳状滤波器的方波型输出函数展开，当这2个函数的系数对比时，有时候没有精确解，此时利用Matlab，通过特别的优化计算，可以得到级联马赫-曾德尔光纤干涉仪的近似结构参数，使其输出谱近似为方波。设计实例表明：此种优化计算方法非常方便、灵活和有效。     

Beugungstheoretische Behandlung eines Differentialinterferometers für ausgedehnte Phasenobjekte

The diffraction theory of image construction has been used, in the case of a differential interferometer employing a Wollaston prism, to derive the position of the interference fringes in dependence upon the phase object and the prism position. This procedure is not only more correct, but proves also to be simpler than the corresponding geometric-optical treatment. An example is presented in which the fringe shift resulting from a symmetrical gas flow has been used to evaluate the gradient of the optical path perpendicular to the rotational axis of symmetry.

     

White-Light Frequency-Domain Interferometry Using a Köosters Prism

An optical frequency-domain interferometer incorporating a Kösters prism is constructed to offer an excellent instrument for making a stable precision-measurement of material absorption and dispersion. The working stability is well retained over a long-term operation of 15 h, but the spectral resolution is limited to the resolving power of the spectrum analyzer used. The absorption and dispersion measurements are demonstrated by use of two samples of a BK-7 glass plate and rhodamine in ethanol.     

静态偏振风成像干涉仪中光在四面角锥棱镜中的传播规律研究

简述了自行设计的新型静态偏振风成像干涉仪的原理和四面角锥棱镜的分光机理;应用光线追迹法,推导出了主截面内任意光线在棱镜中的传播方向及出射点坐标,建立了平行光束经角锥棱镜后的偏向角和透过率的理论表达式;采用计算机模拟给出了偏向角和透过率随入射角的变化关系曲线;根据静态偏振风成像干涉仪的具体参数确定了四面角锥棱镜的侧面和底面夹角以及底边长度.该研究为静态偏振风成像干涉仪的研制提供了理论依据.     

一种基于光学倍乘原理的绝对距离干涉测量系统

介绍了一个基于光学倍乘原理的绝对距离干涉测量系统。系统包括两个干涉仪:采用半导体激光器作为光源的定位干涉仪和测量位移的外差干涉仪。介绍了光源的选择,系统的设计以及信号的采集和处理方案。采用这套绝对测量系统,可以实现长度为2m以内的绝对距离测量,定位精度可以达到±0.5μm。     

A microprism array as shearing device for speckle shearing interferometry

In most speckle shearing interferometers image shearing is performed by means of a Michelson interferometer or by means of a wedge prism covering half of the aperture of the camera objective. We present a speckle shearing interferometer which utilizes a microprism array for this purpose. It is placed between the test specimen and the camera. In comparision with a wedge prism it exhibits some advantages: it needs no exact alignment, it works with any camera lens, the shearing distance and direction of shearing can be easily changed by changing position (resp. angular orientation) of the element. Phase stepping for computer evaluation of the speckle shearing interferograms is performed by the translation of the shearing element. A special translation stage was developed. Experimental results are presented. The interferometer is suited for microcomponent and microsystem testing.