High-precision measurement of a fiber connector end face by use of a Mirau interferometer

What we believe to be a new instrument for measuring the end-face geometrical parameters of fiber connectors is described. In this apparatus, a Mirau-type interferometric objective is employed to measure a small area of the connector end face and generate an interferogram corresponding to the surface profile. Various new technologies are used to ensure excellent performance and high measurement repeatability. A multipoint method is proposed to adjust the inclination of the physical contact sample stage. The physical contact angle of the sample stage is adjusted directly on the instrument by use of a special tool whose angle is calibrated with the reversal method. Measurement results of important parameters of the fiber connector end face are compared with those inspected by a commercial profiler or with a standard sample. Optical insertion losses of connectors inspected by the developed system are also evaluated.     

Measuring the acoustic wave velocity and sample thickness using an ultrasonic transducer array

We suggest a new method for determining the longitudinal and transverse acoustic wave velocities and sample thicknesses, which is based on the measurement and analysis of pulsed echo signals by an array of ultrasonic transducers. Analytical expressions relating the delay of signals detected by the array and the values of parameters to be determined are obtained within the framework of a ray model of the measuring system. Measurements on a reference sample have been performed. The values of ultrasonic wave velocities and sample thickness obtained using the proposed technique agree with the results of measurements using independent methods.     

Expressions for determination of layer absorbances of a weakly absorbing double-layer sample through reflectance at the Brewster angles

A new technique for determining absorbances of interferenceless (incoherent) layers based on measurements of the ratio of the front and the back reflectivities of a double-layer sample at the Brewster angles is proposed. A double-layer stack must have at least one absorbing layer, and the two layers should be interferenceless and should be thicker than the wavelength of the incident light. We found that under these conditions the ratio of the front and the back reflectivities at the Brewster angle of a sample surface is directly related to layer absorbance. For a layer with a known thickness this means finding the extinction coefficient of the layer material. In comparison with the conventional method for measuring transmittance, the advantage of this approach is that it affords an opportunity to get rid of the influence of surface effects on the measuring volume absorption coefficient. For a thick layer with known thickness, it makes possible the determination of a small bulk absorption on a background with even greater surface effects. We trust that this technique will prove to be powerful for measuring the extinction coefficients of weakly absorbing materials.     

基于响应面法和Morgenstern-Price法土坡可靠度计算方法

基于响应面法,建立了一种高效的边坡可靠度指标和失效概率近似计算方法。该法在构造响应面函数时,抽样点计算采用Morgenstern-Price法取代传统费时的有限单元法,大大降低了计算工作量。利用Monte-Carlo随机抽样原理,提出了一种能同时确定边坡最危险非圆弧滑动面和最小可靠度指标的随机搜索新算法。该文给出的两个算例验证了方法的实用性和可靠性,其计算结果同时表明:当分别以最小可靠度指标和最小中值安全系数为目标函数时,搜索到的边坡最危险滑动面相差较大。最后,探讨了土性指标(c,φ)的分布概型及相关性对边坡可靠度计算结果的影响。     

A new technique for measuring the constitutive parameters of planarmaterials

A technique for measuring the constitutive parameters of materials over a broad range of frequencies is developed. The technique is specifically designed for planar samples. Planar samples can be placed in the measurement fixture without any special preparation; this makes the technique more convenient than other techniques which require that the sample has to be machined to fit into a measurement fixture. Using fourth-order elements, the finite-element method provides a general, very accurate solution. The technique is experimentally verified by measuring the constitutive parameters of two materials with known properties. The measured results are compared to those of other investigators and are shown to be in good agreement     

Use of a ultrasonic transducer array for measuring the velocity and attenuation of leaky acoustic waves

We suggest a new method for measuring local values of the velocity and attenuation of leaky acoustic waves, which is based on wave field measurements using an immobile array of receiving ultrasonic transducers. In comparison to the methods using a single focused transducer mechanically scanned over a given region of the sample, the proposed technique is advantageous in having a higher operation speed due to the electronic switching of receiving channels in the array and in requiring no high-precision mechanical scanners. A ray model of the proposed measuring system comprising an array of ultrasonic transducers with an electronic scanning facility is described. Theoretical conclusions have been experimentally confirmed by tests on the samples with known properties.     

Heterodyne polariscope for sequential measurements of the complete optical parameters of a multiple-order wave plate

A new heterodyne polariscope for sequential measurements of the complete optical parameters of linearly birefringent materials is proposed. A multiple-order crystalline quartz quarter-wave plate used as a sample was tested in two sequential setups. In the first setup we used an electro-optic modulator to modulate the circular heterodyne polariscope and then applied a phase-locking technique to measure the principal axis angle precisely. In the second setup, removing the first quarter-wave plate, resulted in a linear heterodyne polariscope, and again we used the phase-locking technique to extract the apparent retardance. Furthermore, by tilting the sample and placing a material of known thickness into the second setup, we determined the order, thickness, and refractive indices (ne and no) of a multiple-order wave plate by using the new algorithm. The proposed method has average absolute errors of 0.2167 degrees and 0.15% with respect to the principal axis angle and the apparent retardance, respectively. The order, thickness, and refractive indices are also in good agreement with the known sample data. In contrast to the conventional measurement schemes that could not measure more than two parameters, the proposed heterodyne polariscope uniquely measures six parameters.     

Technique for determining the angular orientation of molecules bound to the surface of an arbitrary planar optical waveguide

A technique to determine the angular orientation of a molecular assembly bound to the surface of a planar optical waveguide of arbitrary structure is described. The approach is based on measuring the absorption dichroic ratio by using the waveguide evanescent fields with orthogonal polarizations (TE, TM) and the same mode order to probe two molecular assemblies, (i) a reference sample composed of an isotropic orientation distribution of dipoles and (ii) a sample of interest. The isotropic sample is used to characterize the waveguide structure, which then allows the orientation parameters of a molecular assembly under investigation to be determined from a measured dichroic ratio. The method developed here is particularly important for applications in gradient-index and multilayer planar waveguide platforms because in those cases the extension of previously reported approaches would require a full experimental characterization of the guiding structure, which would be problematic and may yield inaccurate results.     

基于DSP技术的钢管内直径及内表面检测

提出了一种新的检测钢管内直径及内表面质量的方法。该方法采用高分辨力面阵CCD成像, 通过数字信号处理(DSP)系统进行图像采集,图像处理及计算。该方法速度快,精度高,实时性好,可以有效地检测钢管内表面的各种缺陷及钢管内直径。采用像素细分技术,测量精度可达0.05mm。     

Extrinsic fiber-optic Fabry-Perot interferometer sensor for refractive index measurement of optical glass

A simple fiber-optic sensor based on Fabry-Perot interference for refractive index measurement of optical glass is investigated both theoretically and experimentally. A broadband light source is coupled into an extrinsic fiber Fabry-Perot cavity formed by the surfaces of a sensing fiber end and the measured sample. The interference signals from the cavity are reflected back into the same fiber. The refractive index of the sample can be obtained by measuring the contrast of the interference fringes. The experimental data meet with the theoretical values very well. The proposed technique is a new method for glass refractive index measurement with a simple, solid, and compact structure.     

Simultaneous Estimation of Thermal Properties of Living Tissue Using Noninvasive Method

A new noninvasive measurement method is presented for simultaneous estimation of the key thermal properties of cylindrical living tissue. This method is based on heating of the surface of a cylinder and measuring surface temperatures at three points on the cylinder. Numerical calculations and theoretical analysis for the corresponding two-dimensional model are carried out. The results have demonstrated the feasibility of the proposed method. The selection, crossover, and mutation operators of a new real-coded genetic algorithm (GA) are designed in this paper to solve the problem of parameter optimization. Then, a set of simulations are performed to verify the effectiveness of the proposed method as well as to optimize the design of the experiments. Finally, a series of experiments is performed to measure the thermal parameters of the human forearm. The experimental results indicate that the obtained parameters, such as the thermal conductivity, blood perfusion, and volumetric heat capacity, are within the range of reference values. The proposed method is easy to implement in practical applications. Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

A proposed new and quick method for measuring surface tension of liquid helium

Experimental difficulties in measuring the surface tension of liquid helium by the existing methods are discussed. A new, fast and reliable experimental technique for measuring the surface tension of liquid helium is described. The instrument is simple, compact and sensitive for such investigations. The principle of this method is to balance the downward pull due to surface tension on the edges of a glass-slide against the upthrust of liquid helium. The instrumental technique is flexible for modification, to facilitate the measurements of surface tension of other liquified gases and chemicals subjected to various physical conditions     

An acoustic sensor system for determination of macroscopic surfaceroughness

In this paper, an alternative technique for the measurement of roughness of road surfaces is proposed. This noncontact method is based on the scattering of acoustic waves from the road surface and measuring the normalized Fourier spectrum of the scattered wave in the specular direction. Surfaces prepared with different size aggregates ranging from 2.36 mm to 25 mm were analyzed. The roughness parameter of a surface increases linearly with increasing aggregate size. The proposed method can possibly be extended to perform in situ surface roughness measurements from a moving vehicle     

Mapping nanoscale elasticity and dissipation using dual frequency contact resonance AFM

We report on a technique that simultaneously quantifies the contact stiffness and dissipation of an AFM cantilever in contact with a surface, which can ultimately be used for quantitative nanomechanical characterization of surfaces. The method is based on measuring the contact resonance frequency using dual AC resonance tracking (DART), where the amplitude and phase of the cantilever response are monitored at two frequencies on either side of the contact resonance. By modelling the tip-sample contact as a driven damped harmonic oscillator, the four measured quantities (two amplitudes and two phases) allow the four model parameters, namely, drive amplitude, drive phase, resonance frequency and quality factor, to be calculated. These mechanical parameters can in turn be used to make quantitative statements about localized sample properties. We apply the method to study the electromechanical coupling coefficients in ferroelectric materials and the storage and loss moduli in viscoelastic materials.     

An improved de-embedding technique for the measurement of thecomplex constitutive parameters of materials using a stripline fieldapplicator

A method for measuring the electromagnetic constitutive parameters of materials using a strip-transmission-line field applicator is presented. A technique is developed to measure the scattering parameters of the imperfect transition regions between the applicator coaxial terminal ports and the front and back terminal planes of the material sample in stripline, S-parameters of the sample region are subsequently deembedded from the coaxial-terminal model. The complex permittivity and permeability of the sample are easily related to the sample's S-parameters through well-known analytic relations. Measured constitutive parameters are presented for several representative materials     

Measuring the optical parameters of weakly absorbing, highly turbid suspensions by a new technique: photoacoustic detection of scattered light

We present and apply a novel method, the scattering photoacoustic (SPA) technique, for measuring optical parameters in weakly absorbing, highly scattering suspensions. In this method, a solid absorber is in contact with a suspension sample to permit the photoacoustic detection of the sample's light-scattering properties. We conducted measurements conducted to determine the reduced scattering coefficients of Intralipid suspensions with a concentration range of 0.1-5%, and the results are in good agreement with those achieved by other researchers. Moreover, we also illustrate the relationship between the amplitude of the SPA signal and absorption, scattering, and detection distance. Through a study of Intralipid-ink mixes, we demonstrate that the SPA technique has the ability to determine simultaneously the absorption and reduced scattering coefficients of turbid media. This new technique has low cost and is noninvasive, and it enables on-line measurements to be made.     

光纤定位器件微小孔抛光技术

提出了利用金刚石涂层的金属线对光纤定位器件上微小孔抛光的新方法．为验证该方法,设计并制造了一个微型样机．该机器采用了振动系统以提高加工效率．为优化加工参数进行了系统的工艺研究．实验结果表明,采用这种抛光方法加工的微小内孔表面粗糙度可达到0．065μm．     

使用位敏探测器PSD的焦面检测方法

本文介绍一种新的焦面检测方法,以位置敏感探测器PSD作为检焦器件对光学系统的实际焦面进行检测。该方法原理简单、处理快速方便、检测精度较高,特别适用于对透镜截距的测量和胶片摄影系统的精密调焦。还讨论了使用PSD测量先学系统其它参数的方法以及影响PSD测量精度的主要因素。文中还将PSD与CCD等器件做了一些比较,充分肯定了PSD驱动电路简单、处理速度快和分辨率高等优点。     

A new variant for measuring the surface tension of liquid metals and alloys by the oscillating drop method

The theoretical background of the oscillating drop technique for measuring surface tension is briefly presented and the different analysis procedures are cited. A new method is described for obtaining oscillation frequencies by fast fourier transformation (FFT) of the pyrometer voltage signals from temperature measurements at the top of the levitated sample. The results on the first experiments on liquid nickel are in a good agreement with the hterature data.Paper presented at the Fourth International Workshop on Subsecond Thermophysics. June 27–29, 1995, Köln, Germany.     

Radiative Properties of Uranium Dioxide Near Its Melting Point

A new technique for measuring radiative properties of nuclear fuel materials at high temperatures has been developed. The technique is based on pulse diffuse optical probing of the sample surface and on pyroreflectometry used in measuring radiative properties of refractory materials during laser heating or cooling. Pulse diffuse optical probing of the sample has been realized for the first time in subsecond pyrometry of the open surface heated by laser radiation. Such a procedure of sample irradiation during sample laser heating or cooling enables reflectivity and emissivity measurements near high temperature phase transitions to be performed in spite of possible sharp changes of the reflection indicatrix at phase transitions in the investigated material. With the method developed in this study, the spectral emissivity and reflectivity of uranium dioxide near its premelting and melting points have been measured. It has been found that condensation of the vapor plume formed above the sample during laser heating influenced the melting and boiling temperatures of uranium dioxide. The first-order phase transitions in uranium dioxide, such as solid–vapor–solid and liquid–vapor–liquid, have been observed in uranium dioxide for the first time during laser heating. Also, new data on the spectral emissivity of uranium dioxide at a wavelength of 0.644 m and in the temperature range of 2000 to 4200 K are presented.