激光聚变冲击波被动式测速光学系统设计

针对激光聚变装置冲击波速度被动测量的需求,设计了一种测速光学系统。采用高紫外透过率的氟化玻璃,实现了透射式300～800nm复消色差设计。系统光路具有前后两组镜头,中间为平行光,镜头间距可变,光路适应能力强。系统前端两侧的双目机器视觉能够完成自动寻的。平行光路中设置5个激光器,轴上的1个前向照明靶点用来观察条纹相机狭缝处的目标像质,轴外的4个与光轴平行后向传输用来标识系统光轴的位置,激光器部件可电动切入/切出。系统前组镜头F/#数为4,宽谱工作物方分辨率优于10μm,532nm单波长工作物方分辨优于5μm。该光学系统光路排布灵活,可单独被动测速,也可与主动测速系统VISAR耦合构成主被一体复合测速系统,满足激光聚变装置冲击波测速的需求。     

用激光外差技术高精度测量目标速度

搭建了外差探测实验平台,分别选用漫反射目标及类简谐运动模型作匀转速运动及变速运动的测量目标,应用激光外差探测技术实现了对匀转速运动及变速运动物体的速度测量.在匀转速测量过程中,同时采用外差探测法和振幅调制法测量了漫反射目标正负两个方向转动的速度,共得到133组不同的转速结果.通过调整实验系统,亦实现了对类简谐运动目标的...     

薄膜谐振Lamb波传感器测量液体流速矢量的方法

针对液体流速测量领域中微型流量传感器高品质因数、高灵敏度的性能要求。本文设计一种双端增强型薄膜谐振结构实现Lamb波传感器的高品质因数,利用传感器反对称模式(A01模式)在薄膜-液体界面处的消逝波实现液体流速矢量测量。所制作的双端增强型薄膜谐振Lamb传感器A01模式的主峰品质因数为703,A01模式的频率移动量与液体流速大小存在线性关系,频率移动方向与液体流动方向存在对应关系。流速实测灵敏度约为270 Hz/mm/s,传感器稳定性噪声小于0.2Hz,流速最低检测极限值(LOD)为2.2μm/s,流量最低检测极限值(LOD)为18.3nL/min。结果表明,双端增强型薄膜谐振Lamb波传感器可以实现液体流速高灵敏度矢量测量。     

二维点列式激光多普勒法测量物体速度

提出了一种二维点列式激光多普勒测量方法,用于捕捉轨迹有一定波动范围的空间运动物体的速度信息。该方法使衍射光栅产生的多束相干光在空间某探测位置相交,从而形成一个结构可调的二维探测体阵列。当物体轨迹的波动量在二维阵列范围内时,系统即可以获得其速度信息。与扩展光束型的多普勒测速系统相比,该方法具有空间分辨率高及能量集中等优点,因此可以用于远距离探测。另外,对固体表面散射光的多普勒信号进行了分析及模拟。结果表明:测量结果与模拟结果相一致,且经频谱校正后的平均误差可以达到1.63%。该系统结构易于集成,调节方便,适用于轨迹有一定波动量的空间物体的速度测量。     

用于超声散斑跟踪血流测速的多角度平面波局部运动补偿

血流速度剖面用于计算壁面剪切率等血流动力学指标,与动脉粥样硬化病程发展密切相关。 超快超声散斑跟踪广泛用 于血流速度剖面估计,然而多角度平面波复合成像存在血流散射体的运动伪影,不利于流速估计。 提出了一种多角度平面波复 合成像的局部运动补偿法,对射频信号时间序列的相邻帧进行局部运动补偿来消除不同径向位置的运动伪影,从而提高流速测 量准确性。 相比直接相干复合,B-MoCo 法将仿真、仿体实验中流速测量结果的归一化均方根误差平均减小了 10. 37% 、 37. 82% ,说明了 B-MoCo 法的有效性。 基于兔骼动脉的实测实验进一步证明了 B-MoCo 法的临床可行性。 综上,B-MoCo 法能够 有效提高血流速度剖面的测量精度,有助于相关心血管疾病的早期诊断与病程监测。     

Surface finish measurement using microwaves

This paper describes a method of measuring the surface finish using microwaves and contains the results of measurements made on surfaces produced by some machining processes     

扩展光束型激光多普勒速度测量系统

为了获得高速弹丸在出膛后的瞬时速度以及在不同位置时的速度分布,提出了一种基于扩展光束的激光多普勒测速系统.该系统对出射的激光束进行两次扩展,使扩展后的相干光束在空间某一位置相交来形成具有一定延展范围的探测体.该方法有效避免了经典双光束多普勒测速系统由于探测体积小而导致的物体偏离探测区域的情况,因此,在实际测量弹丸速度的过程中能够解决传统多普勒系统因弹道偏差而导致的无法测速的问题.该系统也可以采用并联方式来监测弹丸在弹道不同位置上的速度分布.通过实验对激光束进行了不同尺度的径向扩束,并在此基础上获得了不同散射面积下的多普勒信号.分析结果显示:在速度为10～25 m/s时,测量值与实际值的平均误差可以达到1％～2％,表明这种测量方法是有效且可行的.     

激光聚变冲击波速度测量光学系统设计

针对激光聚变冲击波速度测量的需求,设计了一种集被动式扫描高温计和主动式冲击波速度测量于一体的复合冲击波速度测量系统.通过采用多种耐辐射光学玻璃材料,实现了共用光路的400～700 nm耐辐射消色差设计;通过采用自动控制干涉仪简化了系统操作;主动测速系统通过切换不同焦距的中继成像镜头,实现了不同放大倍率的切换.系统的物方...     

A broadband spectroscopy method for ultrasonic wave velocity measurement under high pressure

A broadband spectroscopy method is proposed to measure the ultrasonic wave phase velocity of Z-cut quartz under high pressure up to 4.7 GPa. The sample is in a hydrostatic circumstance under high pressure, and we can get longitudinal wave and shear wave signals simultaneously in our work. By fast Fourier transform of received signals, the spectrum and phase of the received signals could be obtained. After unwrapping the phase of the received signals, the travel time of ultrasonic wave in the sample could be obtained, and the ultrasonic wave phase velocity could also be resolved after data processing. The elastic constant of measurement under high pressure is also compared with previous studies. This broadband spectroscopy method is a valid method to get ultrasonic wave travel parameters, and it could be applied for elasticity study of materials under high pressure.     

光电非接触式表面流速测量

针对水工物理模型试验中尚无简单易行的表面流速测量方法,提出了一种新型光电非接触式表面流速直接测量法。在对光束入射水体后散射光强度公式进行推导的基础上,根据水体浅层泥沙浓度的统计继承效应,得出了经上下游浅层泥沙调制的散射光强成相关特性的结论。根据上下游散射光的相关特性,推导了流速测量公式,并分析了上下游测量间距、水流流速、采样率对测量结果的影响。搭建了实验系统,在6种不同标定流速下,分析了不同含沙量对测量精度的影响。实验结果表明,在0～50kg/m36种不同含沙量情况下,实测流速与标定流速的一致性均较好,但水体在10～50kg/m3适量含沙情况下,测量精度较不含沙情况有所提高,测量绝对误差均小于0.1m/s,相对误差能控制在8%以内。     

螺旋锥齿轮齿面扫描式测量法及其应用研究

螺旋锥齿轮的实际齿面形状是影响其动力学性能的一个非常重要的因素。本文介绍了采用虚拟共轭基准面的螺旋锥齿轮齿面的扫描式测量、数据处理及应用方法，即大齿轮的基准面采用的是由机床设定参数计算出的理论齿面，而小齿轮的基准面采用的是与大齿轮共轭的假想小齿轮齿面。由于采用了二维测头进行齿面测量，有效地避免了测头与齿面间摩擦力的影响，既能保持高精度，又能进行快速测量。同时，该种测量采用连续扫描的方法，信息量大、速度快，适合于大批量生产中的螺旋锥齿轮的齿面质量管理与控制。由于扫描式测量采用了虚拟共轭基准齿面，所以从测量数据本身就可以判断齿面的接触斑点位置与形状，因而可以直观、有效地对齿面质量进行管理与控制。     

Air velocity and flow measurement using a Pitot tube

The accurate measurement of both air velocity and volumetric airflow can be accomplished using a Pitot tube, a differential pressure transducer, and a computer system which includes the necessary hardware and software to convert the raw transducer signals into the proper engineering units. The incorporation of sensors to measure the air temperature, barometric pressure, and relative humidity can further increase the accuracy of the velocity and flow measurements. The Pitot tube measures air velocity directly by means of a pressure transducer which generates an electrical signal which is proportional to the difference between the pressure generated by the total pressure and the still air (static pressure). The volumetric flow is then calculated by measuring the average velocity of an air stream passing through a passage of a known diameter. When measuring volumetric flow, the ‘passage of a known diameter’ must be designed to reduce air turbulence as the air mass flows over the Pitot tube. Also, the placement of the pitot tube in the passage will influence how accurately the measured flow tracks the actual flow through the passage. Calibrating the measurement system in a wind tunnel can further increase the accuracy of the velocity and the flow measurements. This objective of this paper is to provide the field engineer with single, concise source of information on flow measurement using a Pitot tube.     

Measurements of parallel electron velocity distributions using whistler wave absorption

We describe a diagnostic to measure the parallel electron velocity distribution in a magnetized plasma that is overdense (ω(pe) > ω(ce)). This technique utilizes resonant absorption of whistler waves by electrons with velocities parallel to a background magnetic field. The whistler waves were launched and received by a pair of dipole antennas immersed in a cylindrical discharge plasma at two positions along an axial background magnetic field. The whistler wave frequency was swept from somewhat below and up to the electron cyclotron frequency ω(ce). As the frequency was swept, the wave was resonantly absorbed by the part of the electron phase space density which was Doppler shifted into resonance according to the relation ω - k(∥)v(∥) = ω(ce). The measured absorption is directly related to the reduced parallel electron distribution function integrated along the wave trajectory. The background theory and initial results from this diagnostic are presented here. Though this diagnostic is best suited to detect tail populations of the parallel electron distribution function, these first results show that this diagnostic is also rather successful in measuring the bulk plasma density and temperature both during the plasma discharge and into the afterglow.     

激光测距与光速测量实验方法研究

本文给出了采用相位式进行激光测距的实验原理,根据相位式激光测距原理提出了一种激光测距实验方法。在此基础上,通过对实验方法的调整,同时实现了对光速的测量,并对距离测量和光速测量测量的结果进行了误差分析。     

基于同步压缩变换的临界折射纵波波速精确测量

基于声弹性效应,采用临界折射纵波检测金属材料的残余应力有较为广泛的应用前景。然而临界折射纵波速对应力的声弹性效应较弱,这很大程度上影响了材料应力检测的分辨率。为了提高临界折射纵波波速检测精度,提出一种非线性分解技术(同步压缩变换)对临界折射纵波进行波形变换与重构,精确计算超声到达时刻。以1 060铝板为研究对象,基于有限元仿真软件分析了铝板中临界折射纵波的波形特性,以此为依据调节实验中的超声波信号从而提高实验中临界折射纵波的波形准确性。实验精确测量临界折射纵波在1 060铝板中的传播时间,并计算了铝板中的波速,误差不超过0. 05%。实验结果验证了提出的临界折射纵波波速精确计算方法的有效性。     

Accurate ultrasound speed measurement using an MLS-modulated continuous wave

The continuous wave shows greater potential than the pulse signal to achieve high-accuracy ultrasound speed measurement thanks to its stronger noise resistance. However, the accuracy of ultrasound speed measurement would deteriorate if echoes exist in the received continuous wave. This paper presents an applicable method using the maximum length sequence-modulated continuous wave. The present method improves the accuracy of ultrasound speed measurement further by resisting echoes. The time delay between the received signal and the transmitted signal is estimated accurately by combining the cross-correlation, parabolic interpolation and phase shift technique. Moreover, both the inherent delays induced by physical system and the path length of ultrasound are expediently corrected through least square estimation. As a result, accurate time of flight and ultrasound speed measurement are achievable. For example, the standard deviation of ultrasound speed measurement in distilled water is less than 0.003 m/s, and the deviation between the ultrasound speed measurement and the reference is less than 0.04 m/s.     

Displacement measurement using digital speckle multi-frequency harmonic wave correlation method

In the displacement measurement using digital speckle correlation method, significant measuring error due to the multi-peak nature of the correlation coefficient function is a critical issue as sometimes the secondary peak can be wrongly determined as the maximum instead of the highest peak. In the multi-frequency harmonic wave correlation method (MHCM) as proposed in this work, for speckle patterns before and after the displacement, correlation calculations were performed on corresponding sets of data matrices assembled by amplitudes/intensities obtained from harmonic waves with different frequencies. The calculated maximum correlation coefficients were compared with each other to locate the maximum in order to measure the displacement. Both ultrasonic speckle MHCM and laser speckle MHCM were applied to the displacement measurement respectively. Measured results indicated that MHCM effectively helps to ensure the correct determination of the maximum correlation coefficient, to avoid random errors caused by other factors and improves the measurement accuracy in the meanwhile.     

基于液晶的激光偏振测量系统研究

主要研究基于液晶的激光偏振测量系统,利用液晶可变相位延迟器(LCVR)代替传统测量技术中的旋转波片,改变所加的电压值控制液晶双折射系数,对入射光的偏振状态进行精确控制.通过偏振光调制法测量斯托克斯(Stokes)参量,从而实时、准确地测量激光的偏振特性.同时,利用虚拟仪器LabVIEW软件平台实现系统的数据分析、处理、界面显示和打印输出功能的一体化.研究表明:该方法能够准确地测量光束的偏振特性,能够服务于从科研实验室到工业生产过程的各类应用领域,具有广阔的应用前景.     

Spindle thermal drift measurement using the laser ball bar

Thermally induced errors are major contributors to the overall accuracy of machine tools. An important component of thermally induced errors is the error associated with spindle thermal drifts. In this paper, a novel method is developed to measure spindle thermal drifts in machine tools using a laser ball bar (LBB) as the calibration instrument. The method is implemented on a two-axis CNC turning center. The LBB is used to measure the coordinates of the spindle center and the direction cosines of the spindle axis at various thermal states. The axial, radial, and tilt thermal drifts of the spindle are then computed from the changes in these coordinates. The new method is verified by comparing the spindle drifts measured with the LBB to those measured by capacitance gauges. The results obtained by the new method show good agreement with the capacitance gauge technique. The primary advantage of the new method is the ability to measure the spatial coordinates of the spindle center and direction cosines of the spindle axis with the same instrument used for measurement of the geometric errors of the machine axes.