On the accuracy of microinterferometric measurements of optical-path differences by means of the half-shade method

Using a shearing double-refracting interference microscope with a half-shade eyepiece, the accuracy of optical-path-difference measurements has been examined. For the half-shade elements, birefringent strips with phase difference equal to 180°, 110° and 20° as well as a half-wave plate with a narrow slit, cemented between two glass plates, were used. It is known that different relative intensities of the background inside and outside the half-shade strip introduce a subjective error in the correct visual assessment of the matching point of the interference image of the object under examination. Applying test objects made of thin strips of dielectric evaporated in vacuum onto glass slides, it has been demonstrated that this error depends upon the optical-path difference and image size of the object being measured, as well as upon the half-shade phase difference. For a small half-shade phase difference the error is practically imperceptible and for the half-shade strip giving half-wave retardation it attains maximum values. In the case of homogeneous objects, the images of which are as large as 1.5–2° in the field of view of the microscope, this error does not usually produce inaccuracies greater than ± λ/100 in optical-path-difference measurements. Using the half-shade strip with a diaphragm which masks the misleading background and enables an observer to see the matched image areas only, the optical-path difference can be measured with accuracy ± 0.003λ or better.     

双盘式渐开线测量仪测点位置调整方式

分析了双盘式渐开线测量仪中测点位置偏差对渐开线齿形测量的影响,探讨了高精度调整测点位置的两种方法:试验调整法与误差补偿调整法。试验调整法是根据测点偏离导轨平面测量渐开线齿形时,测量结果中齿形角小于实际值的原理,调整测头处于不同位置并测量渐开线齿形,齿形角最大的测量曲线对应的测点位置即为最佳位置。误差补偿调整法是在测点处于高于导轨平面的两个位置时,分别测量同一渐开线齿形,通过对测点偏移量逐次试值,补偿两次测量结果,使得测量结果中齿形偏差相同,获得测头偏移量。分析得出,上述两种方法调整测头位置的极限偏差分别为±0.010 mm和±0.015 mm,均可满足1级(GB/T10 095.1-2 001)渐开线齿形的测量要求。     

A microwave interferometer with increased stability for diagnostics of steady-state plasma

The schematic and results of studying an interferometer for a wavelength of 8 mm with homodyne frequency conversion for measuring the electron density of a steady-state plasma are described. The design of its waveguide system allows the drift of the indicated initial phase to be reduced to a level of ±0.1°/h. The maximum phase shift measured is 360°, the tolerable signal-power decay in plasma is 16 dB, and the maximum phase measurement error is ～5%.     

空间相机均力输出式调焦机构

为了补偿空间相机因所处复杂运载环境和空间运行环境导致的焦平面偏移,研制了一套利用均力输出组件驱动,正反双曲柄滑块机构传动,直动组件导向的新型高精度调焦机构。介绍了其结构组成和运动原理,并对其误差来源及影响因素进行了深入分析。该调焦机构采用两点支撑方式,两支撑点均力输出且无同步性误差,机构内应力小,运行平稳,调焦精度高;运动副采用预压消间隙措施,有效消除配合间隙,无空回,重复精度高。在模拟空间环境条件下,对其各项参数进行了测试。试验结果表明,该调焦机构可在±1.77mm间调焦,直线定位精度大于±8μm,重复性优于±2μm;同步性误差小于±4μm,重复性优于±3μm;调焦行程范围内调焦反射镜转角精度优于±5″,重复性优于±1.5″。得到的结果能够满足空间相机在复杂空间环境下的成像需求。     

Young's Modulus Extraction Methods for Soft Tissue from Ultrasound Measurement System

Abstract

Young's Modulus of soft tissue is a key index to evaluate the biomechanical features of the soft tissue; it has a close relationship to the force and deformation of the soft tissue. In order to measure the force and the deformation of soft tissue, a specially designed device is used to link ultrasound and force transducers by mounting them in series. The combined transducers can simultaneously sense the compressive force and the deformation of the soft tissue. The measurement system is calibrated, before it is used, to collect the data. Based on the measured force and the measured deformation of the soft tissue, the analytics biomechanical model of the soft tissue can be obtained by data fitting.

In this paper, the biomechanical model of the soft tissue is assumed to be linear and possess viscous elasticity; when the model of the soft tissue is a linear model, the derived Young's Modulus of the soft tissue is a constant; when the model of the soft tissue is a viscoelastic model, the derived Young's Modulus is a function of the deformation of the tissue. Calibration data show that the maximal error of the measurement system is less than 1.9 µm, non‐linearity error γ_T is ±0.06%, and the static error band γ is ±0.07%. The measurement system can be used to diagnose the pathology of soft tissue.     

Improvement of the accuracy of friction coefficient determination with Amsler-type friction machines

The error of friction coefficient determination with Amsler-type machines depends strongly on the friction losses in the machine’s spindle unit. It is shown theoretically that the error is inversely proportional to the product of the lower roller diameter times the friction coefficient to be measured and directly proportional to the friction coefficient of the rolling bearings employed; the error can reach 100% or more. A method of static and dynamic torque sensor calibration is developed to ensure friction coefficient measurement accuracy within ±2%.     

超限学习在磁罗盘非线性误差补偿中的应用

针对磁阻式传感器组成的磁罗盘中不容忽视的非线性误差,建立了隐式非线性误差模型,引入机器学习中的超限学习机算法对非线性误差模型进行训练。利用训练好的误差模型对航向角测量误差进行补偿,误差由补偿前的±3°下降到±0.2°,均方根误差为0.1°。任意选取的训练集、测试集和重复实验证明超限学习算法具有很好的泛化性和鲁棒性,而且训练速度极快,是传统BP神经网络的上千倍。     

光纤石英玻璃基板微V槽阵列的精密磨削

针对脆性石英玻璃的微加工,利用自主研发的金刚石砂轮微尖端修整工艺,研发了光纤阵列石英玻璃微V槽磨削技术。分析了60°的微V槽形状偏差对光纤耦合损耗的影响,然后,研究了砂轮微尖端的误差补偿修整工艺。最后,实验分析了微V槽的磨削精度。理论分析显示:微V槽角度、间距和宽度的偏差分别控制在±0.42°、±1.04μm和±1.2μm以内时,耦合损耗小于0.5dB。实验结果表明:开发的数控磨削工艺可加工高精度的60°微V槽阵列;采用数控轨迹和角度补偿修整后,砂轮微尖端半径可平均达到10.46μm,角度精度为(60±0.22)°;对石英玻璃进行微磨削后,微V槽的角度偏差达到0.4°,尖端半径为10.5μm,宽度偏差为0.3μm,间距偏差为0.5μm,可保证光纤阵列的精密对接。     

High GVF and low pressure gas–liquid two-phase flow measurement based on dual-cone flowmeter

Parameter measurement of gas–liquid two-phase flows with a high gas volume fraction (GVF) has received great attention in the research field of multiphase flow. The cone meter, as a new proposed differential pressure (DP) meter, is increasingly being applied in flowrate measurement of gas–liquid two-phase flow. A dual-parameter measurement method of gas–liquid two-phase flow based on a dual-cone meter is proposed. The two-phase flow is investigated in a horizontal pipeline with high GVF and low pressure, and exists in the form of annular flow. By adding a second cone meter, both gas mass fraction (GMF) and mass flowrate are measured. The pressure drop performances of five different sized cones have been discussed to make a cooperating cone selection and efficiently position the dual-cone in the pipe. Dual-cone flowmeter experiments of 0.45 and 0.65 equivalent diameter ratio combination, and 0.65 and 0.85 equivalent diameter ratio combination are respectively carried out to analyze the linearity of two-phase flow multiplier with Lockhart–Martinelli parameter and obtain the dual-parameter measurement results. The relative experiment error of GMF, gas mass flowrate and total mass flowrate are respectively within ±7%, ±5% and ±10%. The relative error of the liquid phase is within ±10% when the liquid mass fraction is beyond 40%. The experimental results show that it is efficient to utilize this dual-cone method for high GVF and low pressure gas–liquid two-phase flow measurement.     

Experimental study on rectangular cut-throated flume: Effects of flume walls slopes and channel longitudinal slope

This research conducted to study the flow through a rectangular cut-throated flume (RCTF). The flume is simply formed by placing two vertical triangular prisms (two vertical folded plates) on either side of a rectangular open channel. Both channel and flume cross-sections are rectangular. The investigated flume is inexpensive, easy to install and does not require high maintenance. A wide experimental investigation, carried out under free outflow conditions and under upstream subcritical flow regime to investigate the effects of the channel longitudinal slope, the flume throat width, and slopes of upstream and downstream flume walls on the stage-discharge relationship. The stage-discharge relationships were deduced by applying the dimensional analysis and were calibrated using the data of this study. The proposed stage-discharge equation for horizontal channel has an average absolute relative error of 2.97% with the relative errors restricted in the range of ±10%, and 80% of the data points are in the error range of ±5%. The proposed stage-discharge equation for sloping channel has an average absolute relative error of 3.97% with the relative errors restricted in the range of ±10%, and 66% of the data points are in the error range of ±5%. The measurements indicate that slopes of upstream and downstream walls affect the stage-discharge relationship of the CTFs only in sloping channels and flow discharge is not influenced by the flume walls slopes in a horizontal channel. The proposed unified stage-discharge equation for both horizontal and sloping channels has an average absolute relative error of 3.38% with the relative errors restricted in the range of ±10%, and 74% of the data points are in the error range of ±5%. The proposed stage-discharge model demonstrates favorable accurate and convenient estimation of discharge for flows through the CTFs.     

双盘式渐开线测量装置误差的计算机补偿方法

以双盘式渐开线测量装置为研究对象,研究了对此装置的微机误差补偿方法。从众多的误差源中选出最大的三种误差进行补偿,使装置不确定度由原来的≤±0.7μm下降到≤±0.5μm.     

A prototyping and microfabrication CAD/CAM tool for the excimer laser micromachining process

A CAD/CAM tool for prototyping and small-scale production of micro-electro-mechanical systems (MEMS) devices based on the excimer laser ablation process has been developed. The system’s algorithms use the 3D geometry of a microstructure, defined as an STL file exported from a CAD model, and parameters that influence the process (laser fluence, pulse repetition frequency, number of shots per area, wall angle, stitching errors) to automatically generate a precise NC part program for the excimer laser machine. The performance of the system has been verified by NC part program generation for several 3D microstructures and subsequent machining trials. An initial stitching error of 23.4±2.2-μm wide and 3.4±1.5-μm high was observed when the overlap size between adjacent volumes was zero, when ablating 100×100-μm features in polycarbonate (PC) at a fluence of 0.5 J/cm² using a workpiece-dragging technique. When the size of the overlap was optimised by a system based on optimal process parameters determined by the Taguchi design of experiment method (DOE), and incorporated in the mask design, the maximum stitching error was reduced to 13.4±2.2-μm wide and 1.4±0.9-μm high under the same conditions. By employing a hexagonal-shaped mask with incorporated size of the image overlap, reduced horizontal-stitching errors of 2.4±0.2-μm wide and 1.4±0.2-μm high were observed. The system simplifies part program creation and is useful for excimer laser operators who currently use a tedious trial and error process to create programs and complex masks to generate microstructure parts.     

Electron microscopy of the poly-l-lysine α-helix

Dark field electron micrographs of polylysine molecules in the α-helical form were analyzed by digital Fourier techniques to determine the extent to which the helix was still represented in the images. A total of 50 molecular images were selected following defined criteria, 13 from spreads of molecules from aqueous solution and 37 from methanol solution. As controls, similar shapes were chosen from the random structure seen in the carbon specimen support without polylysine. Computer analysis of the 50 molecular images indicated the presence of a helical structure with a pitch of 0.54±0.01 nm and a pitch angle of 25.6°±1.5° (standard error) in over 70% of the images. Moreover, 63% of the total α-helix measured by circular dichroism for the molecules in solution was still represented in the micrographs. The controls had no helical characteristics.     

高精度角位移平台的研制及误差补偿*

在拉曼光谱仪中,要求承载分光元件转动的角位移平台在具备较大的转动范围、较高的转角分辨率和转角定位精度的同时还具备较快的转动速度,传统的几种驱动方式很难同时满足上述所有要求。有鉴于此,设计了一种采用力矩电机直接驱动技术的高精度角位移平台。一般控制方法的控制精度在很大程度上依赖于反馈元件的测量精度,为了突破反馈元件测量精度对整个控制精度的影响,采用了一种更为精确的误差补偿校正技术,并搭建了误差测量装置,将测得的绝对转角误差在控制器中通过一定的控制算法加以有效的补偿。最后,对结构设计和误差补偿校正的效果进行了实验检测。结果显示:当测量步距为1°时,双向绝对定位精度优于1.008″;当测量步距为10°时,双向绝对定位精度为0.648″;回转轴系的轴向晃动误差小于±5″。以上结果验证了该角位移平台具有机械精度高、转角分辨率高、定位准确等技术优势,能够满足拉曼光谱仪等相关仪器的使用需求。     

Absolute angle-measurement with a dihedral mirror of the multi-longitudinal mode laser self-mixing sensor

In this paper, a static multi-longitudinal mode laser self-mixing absolute angle measurement system is developed to accurately monitor the deflection angle. The experimental results show that this multi-longitudinal mode laser angle sensor is capable of effectively measuring the deflection angle of the vertical dihedral mirror. The angle-measurement range and resolution of the self-mixing experimental sensing system can be obtained as ±22.0° and 0.008°, respectively. Furthermore, in-depth analysis of the angle-measurement error and related error sources are performed, of which the absolute error is less than 0.37° that demonstrates the good reliability and practicality of the self-mixing angle sensor.     

超精密外差利特罗式光栅干涉仪位移测量系统

开展了扫描干涉光刻机工作台超精密位移测量的实验研究,以提高扫描干涉光刻机的环境鲁棒性。针对扫描干涉光刻机工作台位移测量精度,提出了新型高环境鲁棒性外差利特罗式光栅干涉仪测量系统。介绍了系统测量原理,设计了测量系统,提出了基于Elden公式的系统死程误差建模方法。设计制造了尺寸仅为48mm×48mm×18mm的光栅干涉仪。基于误差模型计算了死程误差,计算结果表明:对于1.52mm死程的光栅干涉仪,宽松的环境波动指标(温度波动为0.01℃、压力梯度为±7.5Pa、相对湿度波动为1.5%、CO2含量波动为±50×10-6)仅引起±0.05nm的死程误差。最后,设计了基于商用双频激光平面镜干涉仪的测量比对系统,开展了光栅干涉仪原理验证实验和测并量稳定性实验。原理验证实验表明:光栅干涉仪原理正确且系统分辨率达0.41nm。测量稳定性实验表明:常规实验室环境下,环境波动引起的死程误差为7.59nm(3σ)@0.9Hz1~10Hz,优于同等环境条件下平面镜干涉仪的31.11nm(3σ)@0.9Hz1~10Hz。实验结果显示系统具有很高的环境鲁棒性。     

A precision CNC turn-mill machining center with gear hobbing capability

With ever increasing demand for small parts with complex shapes and high dimensional accuracy, many traditional machine tools have become ineffective for machining these miniature components. Typical examples include dental implants, parts used in mechanical watch movements, and parts used in medical endoscopes. This paper introduces our PC-controlled CNC turn-mill machining center. It has 5 axes, an automatic bar feeder, an automatic part collection tray, and a tool changer. It features a special control algorithm for the synchronization of its axes that produces not only higher accuracy but also makes the machine easier to use. In addition, a volumetric error compensation algorithm is implemented to improve accuracy. Based on experiments, the machining error is ±3 μm for turning, ±7 μm for milling and the maximum profile error is less than ±7.5 μm for gear hobbing.     

双模式紫外光谱辐射计的波长机构精度分析

通过对双模式紫外光谱辐射计中波长扫描机构的系统误差进行分析和计算,确定仪器的波长读数精度值。选用标定过的低压汞灯谱线和氘灯,分别在常压和真空环境测试不同模式下的波长读数值,并采用最小二乘法拟合紫外光谱辐射计在工作波段内波长读数值,验证波长读数精度≤±0.03nm。     

Measurement of the viscosity of biodiesel by using an optical viscometer

In this paper, we report the characterization of the viscosity of biodiesel produced from jatropha curcas. The viscosity measurement has been carried out by using a modified falling ball viscometer as well as optical technology. The viscosity was measured from 28 to 70 °C, which is the interest for determining the quality of biodiesel. We found that the falling ball optical viscometer offers a resolution of a viscosity measurement of ±0.039 mPa s with a relative error of 1.47933%. The measurement process was compared with a commercial viscometer, and it has been demonstrated that the biodiesel produced in Chiapas has good quality.     

Discrete liquid-helium level-meter sensors based on TVO carbon resistors

It is shown that for discrete liquid-helium level-meter sensors, based on TVO resistors with a rated power of 0.125 W and rated resistance value of 1 kΩ, one can attain a helium-level measurement error of ±0.5 mm for the horizontal TVO resistor disposition and ±2 mm for the vertical one.