The application of the refractive fringe diagnostic to shocks in air

A review of the refractive fringe diagnostic is presented. A modified de Laval nozzle is used to produce shocks in air, which are transversely probed using a low power HeNe laser. The refractive fringes recorded on film at different imaging distances are analysed using a video digitization technique. Both strong and weak density profiles are deduced.     

一种干涉条纹细化算法的改进

针对经典Hilditch细化算法处理干涉条纹有过多的毛刺和断点的不足的问题,提出了改进的Hilditch细化算法。该算法借鉴了OPTA算法中的8个模板,在每次扫描图像之前,调用这8个模板。改进的细化算法可对干涉条纹进行细化处理,细化结果相对光滑,无毛刺分叉,有利于干涉条纹的精确判读。     

类Ne铬X射线激光莫尔条纹技术研究

利用星光 II激光装置以较低泵浦功率密度获得了类Ne铬X射线激光,并以此为探针光建立了莫尔条纹偏折装置,获得了清晰的静态X射线激光莫尔条纹。介绍了实验方法,给出了实验结果,并对结果进行了讨论。     

A simple way for improving the identification of the central fringe in a fibre-optic white-light interferometer

A white-light fibre-optic interferometer working in the spatial domain, using a special three-peak-wavelength LED as the light source, is presented. Based on the Gaussian spectrum distribution function, a simple spectrum decomposing method has been used to describe the special three-peak-wavelength LED source. Experimental and theoretical analyses show that the special three-peak-wavelength LED source can be used in white light interferometry to simplify the problem of central fringe identification.     

Refractive index profiling across a candle flame using speckle techniques

Refractive index profiles have been obtained at different heights in the region above a candle flame both theoretically and experimentally by means of double and multiple exposure speckle photography. Improved fringe visibility has been achieved in the case of the multiple exposure technique giving rise to accurate measurement of the refractive index. Theoretical analysis shows that the resulting speckle pattern is equivalent to the ordinary pattern convolved with a function representing the effect of light deflection, while the interference pattern obtained is modulated by a background representing the autocorrelation function of the diffuser.     

条纹法提高成像分辨率的实验研究

 对利用条纹场照射目标以提高成像分辨率的方法进行了实验研究。条纹法提高成像分辨率的基本思想是,采用余弦条纹场照射目标,光学系统截止频率外的一部分高频分量将通过光学系统,通过对用多幅同频条纹场照射目标所获得的图像序列进行综合处理,可以获得超分辨率的图像。实验采用激光形成的干涉条纹场照射目标,共采用10幅余弦条纹场,各幅条纹场之间依次有1/10个周期的平移,对这10幅条纹场照射目标时所拍摄的图像进行综合处理,获得了分辨率提高的图像。实验结果证明了利用干涉条纹场照射目标获得超分辨率像这一方法的可行性。     

利用电磁波折射现象计算和测量液体折射率

电磁波在传播过程中如果遇到障碍物,就会产生反射和折射现象,并且遵守反射定律和折射定律.本实验利用一个金属板作为反射体,利用蒸馏水、乙醇、糖溶液(80％)作为折射体,验证了电磁波中反射现象和折射现象,同时测量出了液体的折射率.     

Refractive index of two-level gas in quantized field of counterpropagating waves

An expression for the refractive index of a gas of two-level atoms in the quantized single-mode field of counterpropagating waves is calculated. It is shown that in the limit of large numbers of photons the result reproduces the quasiclassical result in only the case of standing wave where intensities of both waves are equal. Explanation of this “strange” situation where the abilities of quantum field theory turn to be more restricted than those of classical theory is given.     

Matlab软件在迈克尔逊实验仪测空气折射率中的应用

通过压强变化时显示屏上干涉条纹出现或者消失的数量,迈克尔逊实验仪可以测定空气的折射率。实验中测量的物理量较多,人工处理数据比较繁琐,且容易出错,因此使用Matlab软件处理数据可以直接得到不同气压的空气的折射率,处理过程快捷精确。Matlab软件处理数据时,对实验数据进行了最小二乘法处理,可以得到空气折射率随气压变化的拟合直线。     

A subfringe integration method for multiple-beam Fizeau fringe analysis

Some aspects concerning the subfringe integration method in interferogram analysis have been investigated and modified. The modified algorithm, introduced in this paper, is capable of reconstructing the phase in the presence of noise or errors in carrier frequency. The subfringe integration method was applied to analyze two computer simulated patterns of equispaced Fizeau fringes using N bucket integration. Also, it is used to analyze the multiple-beam Fizeau fringe. The refractive index profile of polyethylene fiber is obtained by using two methods, subfringe integration method, and Fourier transform method. A comparison between the obtained results using the maintained methods is presented.     

Multiple-beam interferometric determination of the coherence length of spectral sources

A theoretical treatment for multiple-beam fringe visibility taking into consideration the profile of the spectral source is derived for (a) a Gaussian profile; and (b) a Lorentzian profile. A comparative study between the visibility of the two profiles is presented. Expressions for the intensity distribution for Doppler and Voigt cases are given. The fringe visibility dependence on the half-width of the spectral profile of the light illuminating the interferometer for the two cases, namely Lorentzian and Gaussian, is presented. This leads to the view that the coherence length for a Voigt profile is less than it is in the absence of Doppler or pressure broadening. Multiple-beam Fabry-Perot fringes in transmission have been utilized for the determination of the coherence length of the two spectral lines emitted from ¹⁹⁸Hg at wavelengths of 5461 Å and 4358 Å. The method for determination is based on the variation of the visibility of the recorded interference fringes with path difference.     

The identification of fringe positions in speckle patterns

This paper two methods of identifying fringe positions in speckle patterns. The first uses local directional averaging to track fringes, while the second uses standard image processing techniques to connect the patterns into a form where the fringes can be identified.     

利用位相信息的条纹微位移测量

详细讨论了在利用位相信息测量条纹亚像素级位移时 ,随机噪声、量化、像元尺寸和像元间隙对位移分辨力的影响 ,并给出了详尽的实验结果。采用一般CCD实现了 1/ 10像素的单次测量精度。     

散斑法中的干涉条纹级数判别及细分方法

本文给出一种判别及细分散斑法中的干涉条纹级数的简单方法。它可以用于确定位移的大小,干涉条纹级数的判别与细分、提高测量精度以及自动分析。     

Measurement of vibration with Young's fringe modulated speckle patterns in a photorefractive correlator

A technique has been proposed to analyze small in-plane component of vibrations by measuring the fringe shift, and analysing the correlation output of captured vibrating Young's fringes with a photorefractive correlator. Fringes are formed due to interference between the reconstructed speckled beam recorded for stationary object beam, and vibrated speckled beam transmitting through a BaTiO₃ crystal after introducing a small shift in the diffuser position. The correlation peak intensity is affected due to mismatch of vibrations between two piezo-mirrors in the object beam. High correlation output gives an indication of the frequency matching of known reference and unknown vibrations, thus giving information on the frequency of vibration. Vibration amplitudes of the order of a wavelength of light have been measured by counting the number of fringes passing past a line in the observation plane.     

数字散斑条纹图的滤波方法

在现代数字散斑测量方法中，一般采用减模式来产生数字散斑条纹图，它是进一步图像处理的信息载体，同时不可避免地附带有大量的乘性噪声。为了保证测量精度，在进一步图像处理前必须对其进行降噪，选择合适的滤波方法显得尤为重要。在多年实际经验及阅读了大量文献的基础上，该文对国内外常用的数字散斑干涉条纹图滤波方法进行了分类阐述，选择了一些有代表性的方法予以实现，给出实验结果，并进行了对比分析。最后对数字散斑干涉条纹图滤波方法的发展方向给出了自己的看法。     

水槽成像法测定液体折射率

实验利用几何光学的原理,通过水槽成像间接地测定液体的折射率。     

Determination of fractional fringe orders in holographic interferometry using polarization phase shifting

A simple method to determine the fringe orders at points between fringes in holographic interferometry is presented. The method is based on the use of two reference beams in the recording and reconstruction of the interferogram. A phase difference is imposed between the reference beams on reconstruction through polarization elements. The interferogram is viewed through a polarizer to recombine the images. The fractional fringe order is obtained from the angle through which the polarizer is rotated to shift the adjacent fringe to the point of interest.     

Limitation of carrier fringe methods in digital photoelasticity

The carrier fringes method has been proposed in digital photoelasticity in combination with techniques such as Fourier transform and phase shifting method, without considering the influence of the isoclinics on the isochromatic patterns analysis. Unlike other optical methods as moiré and holographic interferometry, in photoelasticity the light intensity emerging from a circular polariscope is related to both the isochromatic retardation and the isoclinic parameter. As it is shown by the theoretical analysis, owing to the misalignment between the principal stresses in the model and in the carrier, the computed retardation is affected by an error which is the same for all photoelastic methods based on the use of carrier fringes. Consequently, the photoelastic analysis carried out by methods that use carrier fringes cannot be applied as a full-field technique. In detail, numerical simulations show that the retardation error is comparable (less than 0.05 fringe orders) with that of other photoelastic methods provided that the misalignment between the principal stresses in the model and in the carrier is less than 30°. On the contrary, in the model zones where the misalignment is higher than 30°, the retardation measurement can be affected by non negligible errors (up to 0.25 fringe orders).     

迈克耳孙干涉仪条纹计数器的研制

设计了电路简单、可自动识别条纹移动方向的迈克耳孙干涉仪条纹计数器。该计数器仅用9个常见的分立元件即实现了对光信号的采集、放大、滤波、整形的功能,并有效地去除了计数过程中的干扰因素。输出信号经条纹移动方向识别电路后,送入可逆计数器能自动进行相应的加计数或减计数并显示。