Spot size effects in miniaturized moving-optical-wedge interferometer

In this paper we study the effect of diffraction on the performance of a miniaturized moving-optical-wedge interferometer. By using the Gaussian model, we calculate the degradation of the interferometer visibility due to diffraction effects. We use this model to optimize the detector size required to obtain maximum visibility and study its effect on resolution of Fourier transform spectrometers based on a moving-optical-wedge interferometer. A comparison between these effects in Michelson and wedge interferometers is also presented showing the advantage of the moving-optical-wedge interferometer in suppressing the diffraction effects with respect to the Michelson interferometer.     

Principle of the moving-mirror-pair interferometer and the tilt tolerance of the double moving mirror

A novel type of interferometer, the moving-mirror-pair interferometer, is presented, and its principle and properties are studied. The new interferometer is built with three flat mirrors, which include two flat moving mirrors fixed as a single moving part by a rigid structure and one flat fixed mirror. The optical path difference (OPD) is obtained by the straight reciprocating motion of the double moving mirror, and the OPD value is four times the physical shift value of the double moving mirror. The tilt tolerance of the double moving mirror of the novel interferometer is systematically analyzed by means of modulation depth and phase error. Where the square aperture is concerned, the formulas of the tilt tolerance were derived. Due to the novel interferometer's large OPD value and low cost, it is very applicable to the high-spectral-resolution Fourier-transform spectrometers for any wavenumber region from the far infrared to the ultraviolet.     

Principle of a two-output-difference interferometer for removing the most important interference distortions

This paper presents a two-output-difference interferometer for removing the most important interference distortions caused by nonlinear detectors. These distortions can be removed not only because the resulting interferogram is composed of the difference between the signals of the two detectors, but also because the modulated signals at each output have the same amplitude and opposite phases. Due to the use of two corner-cube mirrors fixed as a single moving element, the tilt and shearing problem will disappear. The effect of the corner-cube mirror deviation angle and the plane mirror tilt angle are investigated in detail, and the formulas of their tolerance are derived by means of modulation depth and phase error. The advantage of the interferometer enables it to be suitable for Fourier transform spectrometers.     

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.     

原子干涉仪灵敏度的阿伦方差分析

针对分析原子干涉仪灵敏度时,采用哪种阿伦方差容易出现混淆的问题,系统地给出了阿伦方差、重叠阿伦方差和修正阿伦方差三种形式在时域和频域中的详细推导,分析了它们对五类典型噪声的分辨能力,指出修正阿伦方差具有更加适合评估原子干涉仪长期稳定性的特点。基于修正阿伦方差在频域中的表达式,文中还首次给出了存在测量死区的原子干涉仪灵敏度与噪声功率谱之间的传递函数,通过分析其特点,指出了提高原子干涉仪灵敏度的两条具体途径,为原子干涉仪技术的进一步发展和评价奠定了更加扎实的理论基础。     

Modeling and analysis of an extrinsic Fabry-Perot interferometer cavity

A schematic representation of optical feedback between two resonator mirrors undergoing a phase shift each round trip as a function of the separation of the mirrors is studied. A transfer function modeling of the extrinsic Fabry-Perot interferometer (EFPI) is presented. Nyquist analysis has been used to forecast the operational stability and possibility of interference in an EFPI. The analysis with two perfectly parallel surfaces of the cavity shows efficient interference. The performance when there is some tilt between the two mirrors in the cavity is also studied and is presented. In this case some restricted interference is found.     

马赫-曾德尔干涉仪对大气后向散射的谱分析

论证了马赫-曾德尔干涉仪对532 nm/354.7 nm大气后向散射的频谱分析性能。马赫-曾德尔干涉仪接收激光大气后向散射回波,通过测量双臂光路、正交偏振、四通道结构形成的干涉相位差和干涉对比度,计算大气的多普勒频移,以及大气气溶胶后向散射与气体分子后向散射的比值;发射脉冲激光器及其倍频器可以直接工作在多纵模状态下,大气的后向散射的频谱分析器可以不必与发射光中心频率锁定;给出同时探测大气的后向散射比分布廓线及大气风速的分析方法。马赫-曾德尔干涉仪作为大气后向散射的频谱分析器,若应用于高光谱分辨率激光雷达中,将成为一个性能优秀、前景广阔的大气分析装置。     

Simulation and analysis of a multi-order imaging Fabry-Perot interferometer for the study of thermospheric winds and temperatures

We describe an analysis procedure for estimating the thermospheric winds and temperatures from the multi-order two-dimensional (2D) interferograms produced by an imaging Fabry-Perot interferometer (FPI) as imaged by a CCD detector. We also present a forward model describing the 2D interferograms. To investigate the robustness and accuracy of the analysis, we perform several Monte Carlo simulations using this forward model for an FPI that has recently been developed and deployed to northeastern Brazil. The first simulation shows that a slight cross-contamination at high temperatures exists between neighboring orders in the interferogram, introducing a bias in the estimated temperatures and increasing errors in both the estimated temperatures and winds when each order is analyzed in full. The second simulation investigates how using less than an entire order in the analysis reduces the cross contamination observed in the first set of simulations, improving the accuracy of the estimated temperatures. The last simulation investigates the effect of the signal-to-noise ratio on the errors in the estimated parameters. It is shown that, for the specific FPI simulated in this study, a signal-to-noise ratio of 1.5 is required to obtain thermospheric wind errors of 5?m/s and temperature errors of 20?K.     

Reflective grating interferometer: a folded reversal and shearing wave-front interferometer

The reflecting grating interferometer (RGI) is a folded and reversal wave-front interferometer sensitive only to asymmetrical aberrations such as third-order coma. The RGI can isolate and evaluate coma both in nearly collimated and in noncollimated beams. We propose a RGI with a different optical configuration that includes a lateral shearing in addition to folding and reversal operations. With lateral shear, the RGI also becomes sensitive to other terms of third-order aberrations such as defocusing, astigmatism, and spherical aberration. Optical path difference equations for interpreting interferograms and numerical simulations are presented to show how the interferometer works in the shearing configuration. Its potential applications are described and discussed.     

多级爪型干式真空泵原理分析

多级爪型干式真空泵的结构对于其材料消耗、体积、能耗等性能有着非常重要的作用。本文介绍了北京朗禾科技的最新型结构——螺旋反爪结构,就其原理和国际上最经典的两种结构:螺旋型(德国)和反爪型(英国)做了介绍和对比,说明螺旋反爪结构可以大幅度缩短泵的长度、节约大量的材料、提高抽气效率、降低加工精度、提高抽气性能,对爪型干式真空泵的发展和普及有很好的推动作用。     

Tilt sensitivity of the two-grating interferometer

Fringe formation in the two-grating interferometer is analyzed in the presence of a small parallelism error between the diffraction gratings assumed in the direction of grating shear. Our analysis shows that with partially coherent illumination, fringe contrast in the interference plane is reduced in the presence of nonzero grating tilt with the effect proportional to the grating tilt angle and the grating spatial frequencies. Our analysis also shows that for a given angle between the gratings there is an angle between the final grating and the interference plane that optimizes fringe contrast across the field.     

Characterization of the wind imaging interferometer

The Wind Imaging Interferometer is a field-widened Michelson interferometer onboard the Upper Atmosphere Research Satellite. The characterization of the instrument required a pixel-by-pixel evaluation of the instrument performance. Some of the configurations, techniques, and results of the characterization are summarized. Throughput was excellent and equivalent to a total system quantum efficiency of ~10%. Localized spatial noise in response has been attributed to scattering from residual surface effects on the CCD. Instrument visibility factors greater than 90% were measured with distinct distribution patterns over the field of view that were different for the night and day apertures. The instrument phase for zero wind was determined with laboratory airglow sources.     

An analysis of the polarization component of the measurement error in heterodyne laser interferometer measurement systems

The reasons for the occurrence of the polarization component of the measurement error in heterodyne laser interferometer measuring systems are considered. An analysis of this component is given.     

Nonlinear phase error analysis of equivalent thickness in a white-light spectral interferometer

A white light spectral interferometry based on a Linnik type system was established to accurately measure the thin film thickness through transparent medium. In practical work, the equivalent thickness of a beam splitter and the mismatch of the objective lens introduce nonlinear phase errors. Adding a transparent medium also increases the equivalent thickness. The simulation results show that the equivalent thickness has a significant effect on thin film thickness measurements. Therefore, it is necessary to perform wavelength correction to provide a constant equivalent thickness for beam splitters. In the experiments, some pieces of cover glasses as the transparent medium were added to the measured beam and then a standard thin film thickness of 1052.2±0.9 nm was tested through the transparent medium. The results demonstrate that our system has a nanometer-level accuracy for thin film thickness measurement through transparent medium with optical path compensation.     

Jones matrix analysis of frequency mixing error in three-longitudinal-mode laser heterodyne interferometer

In this study, the authors investigate theoretically a periodic non-linearity effect and its compensation in a three-longitudinal-mode heterodyne interferometer (TLMI). An analytical formula of the frequency mixing error in the TLMI is obtained based on the Jones calculus taking into account experimental parameters. We find that the non-ideal polarisation states and imperfect alignment of the optical setup play the major role to produce four- and eight-cycle non-linearities. The operation of non-linearity compensation system on the four- and eight-cycle non-linear errors is also presented.