X波段高功率微波馈源辐射总功率阵列法测量技术

分析了采用阵列法测量高功率微波(HPM)馈源辐射总功率的相关技术环节。仿真计算了某型X带HPM馈源辐射场分布,设计了积分法测量辐射总功率的参数,并对积分总功率与端口注入功率的关系以及积分方法引入的测量误差进行了计算。设计了由8路HPM辐射场功率密度测量系统组成阵列,对馈源辐射场功率密度进行测量,保证功率密度测量结果一致性和重复性。测量结果表明：多路测量系统测量波形相同,单路系统多次重复测量偏差在±0.1 dB内,多路测量系统对同一点辐射场功率密度测量偏差在±0.3 dB内,馈源热测E面方向图与冷测结果基本符合,积分总功率与等效辐射功率测量结果吻合较好。     

Instantaneous frequency measurement using two parallel I/Q modulators based on optical power monitoring

A scheme for instantaneous frequency measurement(IFM)using two parallel I/Q modulators based on optical power monitoring is proposed.The amplitude comparison function(ACF)can be constructed to establish the relationship between the frequency of radio frequency(RF)signal and the power ratio of two optical signals output by two I/Q modulators.The frequency of RF signal can be derived by measuring the optical power of the optical signals output by two I/Q modulators.The measurement range and measurement error can be adjusted by controlling the delay amount of the electrical delay line.The feasibility of the scheme is verified,and the corresponding measurement range and measurement error of the system under different delay amounts of the electrical delay line are given.Compared with previous IFM schemes,the structure of this scheme is simple.Polarization devices,a photodetector and an electrical power meter are not used,which reduces the impact of the environmental disturbance on the system and the cost of the system.In simulation,the measurement range can reach 0 GHz-24.5 GHz by adjusting the delay amount of the electrical delay lineτ=20 ps.The measurement error of the scheme is better at low frequency,and the measurement error of low frequency 0 GHz-9.6 GHz can reach-0.1 GHz to+0.05 GHz.     

Research note: Vibration amplitude measurement using a fringe-counting technique

A simple, self-calibrating vibration amplitude measurement technique, which employs a Twyman-Green interferometer and a fringe-counting technique, is proposed. It has been experimentally shown to be accurate to within the quantization error of an optical half wavelength.     

Mass measurement using an intensity-modulated optical fiber sensor

Design and operation of an opto-mechanical sensor for mass measurements is reported. This device uses a pair of optical fibers and a reflecting coated lens. The light intensity modulation is based on the relative motion of the lens due to a given mass with respect to the optical fibers. The modulated intensity because of the weighing mass has been measured by using a digital voltmeter. A full-range sensitivity of about 11.5 mV/g for a dynamic range of 80 g is obtained. A mass resolution of better than 0.25 g has been measured with this device. The measured output response is checked against the expected theoretical one and a general agreement observed. A comparison with similar experimental results shows some advantages of this method and potential use of such a sensor for medium mass measurements.     

Hybrid measurement system including optical heterodyne and laser microscopy functions using an acoustooptic deflector

The construction of a hybrid measurement system for measuring lateral and vertical dimensions and its applications to industrial inspection are described. This system uses an acoustooptic deflector, and includes optical heterodyne, confocal and non confocal laser scan microscopy functions in one and the same optical device. These functions are used individually or collectively depending on the purpose of the measurement. For example, by using the optical heterodyne and non confocal microscopy functions at the same time, lateral and vertical dimensions can be measured simultaneously.     

Velocity measurement by the laser speckle method using optical fibres

An optical device for in-plane velocity measurement is described. Laser light is focused by the use of an optical fibre onto the object, and the device utilizes the dynamic sparkle effect for velocity determination. The influence of different optical fibres on the speckle formation is investigated with special respect to fibre movement, and as the diameter of the aperture used for speckle detection also affects the measuring signal, an optimum value is found. A simple electronic circuit processes the measuring value proportional to the object velocity.     

一种基于互易原理的超声功率新测量方法

本文从换能器的互易原理出发，利用平面波自易校准法获得换能器的自由场发送电流响应．根据平面活塞型换能器的衍射规律，推导出发射声功率的表达式．由此计算互易换能器在给定驱动电流（或电压）作用下的辐射超声功率．基于上述原理，使用自易校准装置测量了互易换能器的声功率一频率曲线．估计的测量不确定优于±20％．     

Acoustic parameter measurements by acousto-optic diffraction techniques using a light-beam of one acoustic wavelength width

A method is presented for measuring the Raman-Nath parameter by an acoustically diffracted light-beam of one acoustic wavelength width. The diffraction spectrum obtained is not discrete but broadened continuously because of the width of the light-beam itself. The Raman-Nath parameter can be determined from the intensity measurement at the centre of the diffraction pattern. The acoustic wavelength can also be determined by measuring the light-beam width of one acoustic wavelength at which a beating photocurrent, produced by the positive and negative first-order diffraction components, dies out at the centre of the pattern.     

Acoustic cavitation series: part one: Acoustic cavitation: an introduction

Acoustic cavitation has been an active area of research for at least 30 years and interest in the subject shows no sign of diminishing. Cavitation may occur whenever high intensity ultrasound is applied to liquids, for example in such important applications as sonar, industrial processing and bio-medical research. Future issues will carry a series of articles reviewing the physics and technology of acoustic cavitation, each contributed by a well-known specialist. The present introductory article is a preface to the series, covering background history, explaining the scope of the subject and defining terms in common use. Also included is a list of the major sources of reference presently available, in the form of books, reviews and collections of papers.     

光学信号互相关法烟气流速测量的研究

工业环境中的烟气流速测量是一个很重要的问题。研究了利用抗干扰能力强、能适应恶劣环境的非介入式的光学信号互相关技术测量烟气流速。利用光学传感器获取由烟气造成的光学闪烁信号,通过高性能数据采集卡进行数据采集和A/D转换,在计算机上编制软件,对由烟气造成的光学闪烁信号进行了互相关处理,求得了烟气流经上游和下游传感器的渡越时间,从而计算出了烟气流速值。通过风洞实验,比较了该方法与传统的皮托管法的测量结果,分析了流速反演方法存在的问题及解决方法。在此基础上获得了较为满意的结果。     

多光束激光外差高精度测量玻璃厚度的方法

利用基于激光外差测量技术和激光多普勒技术的非接触式多光束激光外差测量方法,得到了光电探测器输出电流的谐波表达式.讨论了该测量方法用于玻璃厚度超精密测量的可行性及理论依据,并利用Matlab软件对不同情况进行了仿真实验.结果表明：该方法在不同入射角时测量平板玻璃厚度最大的误差为0.3%,明显比其他测量方法精度高. 关键词： 外差探测 多光束激光外差 激光多普勒技术 非接触式测量     

An acoustooptic method of measuring the noise equivalent power of optical heterodyne systems

The noise equivalent power of optical heterodyne detection at 10.6 m has been measured with a method based on Raman-Nath diffraction of a CO₂ laser beam. One of the frequency shifted first order diffracted beams is used as the signal radiation. The local oscillator radiation is obtained by splitting off a part of the laser beam incident upon the device used for the acoustooptic diffraction. The signal power can be varied over a large dynamic range by changing the acoustic input power. A study of the probable errors shows that the total error in the NEP measurement is less than 30%.     

基于合成波长法的飞秒激光外差干涉测距方法

本文提出了一种基于合成波长法的飞秒激光外差干涉测距方法.系统采用两个带通滤波器产生两个具有一定波长差的单波长,用于产生合成波长.本方法结构简单,能量利用率高.与双频激光干涉仪在40 mm范围内的比对结果表明,该方法比对残差的标准差为91 nm.     

基于菲涅尔反射的光纤激光器功率测量方法

分析了光纤熔接点处的菲涅尔散射光模型,得出熔接点散射光功率与输出光功率成线性关系的结论。利用该结论设计了kW级光纤激光器的振荡器、泵浦源输出功率检测装置,并安装在某kW级光纤激光器上进行了实验。通过建立线性估计函数,利用最小二乘法对光纤熔接点的散射光功率与光纤激光器的振荡器、泵浦源输出功率的关系进行了拟合。通过实验验证了熔接点散射功率与光纤输出功率的线性关系。实验表明利用熔接点散射光功率间接测量光纤激光器输出功率的方法线性度优于4%。     

A method for phase reconstruction in optical three-dimensional shape measurement

In optical three-dimensional shape measurement, a method of improving the measurement precision for phase reconstruction without phase unwrapping is analyzed in detail. Intensities of any five consecutive pixels that lie in the x-axis direction of the phase domain are given. Partial derivatives of the phase function in the x-and y-axis directions are obtained with a phaseshifting mechanism, the origin of which is analysed. Furthermore, to avoid phase unwrapping in the phase reconstruction, we derive the gradient of the phase function and perform a two-dimensional integral along the x- and y-axis directions. The reconstructed phase can be obtained directly by performing numerical integration, and thus it is of great convenience for phase reconstruction. Finally, the results of numerical simulations and practical experiments verify the correctness of the proposed method.     

Laser heterodyne vibration measuring method

This paper introduces a heterodyne vibration measuring method: a new signal processing device with a microprocessor has been designed. The most important advantages of this method are that the vibrating amplitude and frequency of the object can be measured simultaneously, with a measuring accuracy of 1% and 0.5% respectively. Better heterodyne signals can be seen by using glass microspheres as scatterers. By using their strong backward scattering, the vibrations in non-optic axis directions can be measured. This method can be used for measurements in which the vibrating body cannot be loaded or is at a long distance.     

高功率微波辐射场功率阵列测量装置研制

基于高功率微波辐射场分布积分方法,通过衰减、延迟、合路等技术手段,研制了一套高功率微波辐射场功率阵列测量实验装置。该装置仅利用一台示波器就可以同时测得16个不同点处的高功率微波辐射场波形,由此得到不同点处的功率密度,在辐射天线方向图旋转对称的条件下,利用编写的程序可以迅速求得单次、短脉冲高功率微波源的空间辐射功率,并在X波段相对论返波管高功率微波源功率测试中得到应用,为高功率微波功率测量特别是单次HPM功率测量,提供了一种新的功率测量阵列装置。     

高功率微波辐射场功率阵列测量装置研制

基于高功率微波辐射场分布积分方法,通过衰减、延迟、合路等技术手段,研制了一套高功率微波辐射场功率阵列测量实验装置。该装置仅利用一台示波器就可以同时测得16个不同点处的高功率微波辐射场波形,由此得到不同点处的功率密度,在辐射天线方向图旋转对称的条件下,利用编写的程序可以迅速求得单次、短脉冲高功率微波源的空间辐射功率,并在X波段相对论返波管高功率微波源功率测试中得到应用,为高功率微波功率测量特别是单次HPM功率测量,提供了一种新的功率测量阵列装置。     

A new ultrasonic technique for the measurement of liquid level

A new design of pulse-echo ultrasonic liquid level gauge is described in which the ultrasonic pulse (here a Rayleigh or a Lamb wave) travels down a metal bar or strip towards the liquid surface, where, through a double mode-conversion process and a special reflecting structure, a strong echo is generated which travels back up the bar to the receiving transducer.The geometry of the special reflecting structure is outlined, and it is shown how this affects the basic accuracy of measurement. Inaccuracies arising from other effects like temperature variation, viscosity and poor signal-to-noise ratio are also discussed. Some mechanical variants, like using the wall of the tank in place of the metal bar carrying the ultrasonic wave and the use of corner reflectors as part of the reflecting structure, are also considered.A note in the Appendix briefly describes one method which has been used successfully for the generation of Rayleigh and Lamb waves.     

Design of thermistor probes for measurement of ultrasound intensity distributions

Thermistors coated with absorbing material provide small omnidirectional probes for measurement of ultrasound intensity distributions. They are simple and inexpensive to construct and can be made with dimensions less than 1 mm. The use of various glues, varnishes and resins for the ultrasound absorbing coating is considered. Heat is generated by shear viscosity in the neighbourhood of the boundary between the thermistor and coating material. The rate of temperature rise over the first one or two hundred milliseconds after the ultrasound is switched on is a reasonably linear function of intensity over the range used in physiotherapy.