Planar acoustic microscope lens using Rayleigh to compressional conversion

A planar acoustic lens is described in which Rayleigh waves generated by a circular interdigital transducer on LiNbO3 are converted to a focused hollow conical beam in the contiguous liquid. The focal spot is comparable to that of a standard diffraction-limited lens of similar aperture; the calculated sidelobes are higher but the measured ones are comparable.     

Acoustic material signature extension

Measurements and an empirical equation are presented for Δz _M, the maxima separation along the lens axis between the focal plane and the first AMS peaks in the metrology mode of the acoustic microscope. The new addition Δz_M extends the upper range of the AMS family to higher Rayleigh velocity materials at microwave frequencies     

声透镜指向性换能器研究

该文利用声学透镜使声波能量聚焦,实现小尺寸换能器窄波束声辐射。利用有限元方法分别建立了单凹面声透镜及双凹面声透镜仿真模型,优化了声透镜结构参数,设计并制作了双凹面声透镜指向性换能器,并在消声水池内对换能器样机和声透镜进行了性能测试。换能器样机辐射面积直径?120 mm,设置声透镜后,提高发送电压响应级4 dB,发射指向性-3 dB波束开角由76°变为约30°(@10 kHz),与仿真计算结果相符。实验结果表明,声透镜有效减小了换能器发射波束宽度,提高了换能器主瓣发送电压响应,验证了双凹面声透镜对优化换能器指向性的效果。     

柱面声透镜声场分析

从惠更斯原理出发,采用点声源合成法对柱面型声透镜声场的分布及声场分布与透镜几何参数间的关系等作了分析.分析表明,如果对声透镜表面的划分足够小,则点声源合成法在一定程度上可用来对声透镜的声场作近似分析,同时发现柱面聚焦声透镜形成的线聚焦声场的分布和焦域声压幅值与声源频率、透镜长度、宽度及其几何半径均有复杂关系.     

低损耗高Q值声表面波谐振器

介绍了低损耗高Q值声表面瑞利波和声表面横波谐振器的原理、结构、制作和关键的设计参数,以及实验结果。其中双端声表面瑞利波谐振器的有载Q值可达5000以上,无载Q值可达20000以上。     

聚焦超声换能器的仿真与性能分析

高频声透镜聚焦超声换能器在电子器件评估与检测、材料微观机械性能表征、生物医学成像、细胞操控等方面具有重要的应用。结构参数是影响其性能的主要因素之一。该文通过有限元法对基于声透镜结构的高频聚焦超声换能器进行仿真模拟,分析了声透镜的开孔角度对该类换能器聚焦区域声压模式、横向分辨率、-6 dB景深等关键性能参数的影响。仿真结果表明,换能器的焦距和横向分辨率与理论计算结果接近。随着声透镜开孔角度的增大,换能器的横向分辨力随之提高,焦点处声压级逐渐增大,-6 dB景深逐渐下降。这为声透镜聚焦超声换能器的优化设计提供了一定的技术基础。     

Rayleigh wave absorption via acoustic microscopy

The acoustic material signature(AMS) model may be used to extract acoustic propagation loss for Rayleigh waves via the reflection acoustic microscope. Attenuation measurements for two metallic material examples are consistent with published results on bulk wave scattering losses.     

抛物形梯度折射率透镜耦合器件的简化模型

本文研究高斯光束经抛物形梯度折射率纤维透镜的传播。其结果表明,当物距大于瑞利距离时,简化模型可描述高斯光束经这种纤维透镜的物像变换。最后讨论了这种模型的一些应用实例。     

圆管中激光激发表面瑞利波极性的有限元分析

用有限元方法数值模拟了脉冲线源激光作用于厚铝管时产生的温升以及由此温升而产生的表面声波的情况,得到了逆时针向探测点和波源之间角度从=5°到=180°范围内一系列表面法向位移的时域波形,并对相同厚度不同外径的铝管的表面波进行对比。数值结果表明表面声波中显著的波为掠面纵波、头波和瑞利波,第一个瑞利波脉冲的极性在传播过程中发生了倒转现象,逆时针向看探测点离波源的角度,当较小时瑞利波脉冲是单极性的(负的),随着角度的增大,瑞利波脉冲逐渐变为双极性的,且双极性中正向极性逐渐增大,到=90°时变为完全双极性(正向和负向对称)。随着角度的进一步增加,双极性中负向极性逐渐减小,到=180°时瑞利波脉冲又变为单极性(正的)。不考虑衍射效应时,圆管中第一个瑞利波脉冲的极性和试样的尺寸无关,仅和探测点离波源的角度相关。     

基于相位光时域反射的光纤分布式声波传感研究

文中提出了一种光纤分布式声波传感方案。作用在传感光纤上的声波信号导致后向瑞利散射光的相位变化,将含有声波信息的后向瑞利散射信号注入到迈克尔逊干涉仪,并采用相位载波解调算法解调出相位信息。实验中采用压电拉伸器模拟声波振动,分布式声波传感系统实现了10 m的空间分辨率以及平坦的频响。     

Linearly focused acoustic beams for acoustic microscopy

A linearly focused acoustic beam is investigated to be introduced into acoustic microscopy for characterising materials in the nonscanning version. The new acoustic beam enables us to detect acoustic anisotropies of materials to be measured successfully. For forming the acoustic beam, an acoustic sapphire lens with a cylindrical concave surface of 1.0 mm in radius is made and the acoustic field distributions are investigated at 200 MHz.     

Investigating stress measurement capabilities of GHz Scanning Acoustic Microscopy for 3D failure analysis

This paper discusses the possibility of using Scanning Acoustic Microscopy in GHz frequencies for detection and analysis of stresses around TSVs. An innovative idea was employed to measure the slight variations in Rayleigh wave velocities as a function of Si crystal orientation using a spherical imaging lens. The fringe pattern around an empty TSV and a copper TSV was analyzed in different directions and Rayleigh wave velocities were calculated. The initial comparison between the measured velocities around the TSVs and the calculated values from a pure Si Crystal suggest the capability of using this technique in detecting Rayleigh wave velocity differences and thus, measuring stresses around Cu TSVs.     

Acoustic Microscopy in Micrometrology

In-depth analysis of the propagation of an acoustic signal excited by a short radio pulse is performed. The signal is reflected from the simple lens of a scanning acoustic microscope, and its power is detected. An expression for V(z) curve (acoustic signature of a material) is derived. It takes into account excitation conditions (delay and recording times of a signal to be detected) and lens parameters.     

球面-锥面声透镜换能器的研究

通过数值计算和实际测量，研究了球面－锥面声透镜聚焦换能器产生的声场，证实其能产生较细长的聚焦声束，并且透镜的形状参数对聚焦声场分布有明显影响。     

A normal mode theory for the Rayleigh wave amplifier

A Rayleigh acoustic wave traveling on the surface of a semi-infinite piezoelectric medium may be amplified by interaction with drifting carriers in an adjacent semiconductor. The gain and frequency response of this interaction is determined here by using a normal mode expansion of the Rayleigh wave piezoelectric fields. The configuration which uses a thin semiconductor film supported by a semi-infinite dielectric and separated from the piezoelectric by a small air gap is described in detail and the results are expressed in a form that clearly shows the effect of piezoelectric, air gap, and semiconductor parameters. Comparisons with experimental data for the lithium niobate-silicon film configuration show that acoustic gains on the order of 100 dB/cm can be obtained in the frequency range above 0.1 GHz.     

Role of coupling fluid in acoustic signature V(z)

The acoustic material signature (AMS) also called V(z) constitutes a unique function that arises from interference of elastic propagating modes in the reflective acoustic microscope. More than only Rayleigh modes can participate in the AMS, and it is shown that by choosing an appropriate coupling fluid, such as mercury, longitudinal modes can also be generated with high efficiency conversion.<>     

Surface Acoustic Wave Properties of Tantalum Pentoxide Thin Films on YX Quartz (Letters)

The properties of a Rayleigh surface wave propagating in tantalum oxide thin films on YX quartz are presented. Dispersion and acoustic wave loss measurements are made using the optical probe technique.     

A tsunami warning system using an ionospheric technique

Earthquakes generate Rayleigh waves which travel along the surface of the earth about 20 times faster than the potentially destructive tsunami (if one is also generated) and reach distant points several hours before the tsunami. The Rayleigh wave excites an upward-propagating acoustic wave which, because of the exponential decrease in air density with height, increases to a large amplitude at ionospheric heights and produces ionization density changes in the ionosphere proportional to the amplitude and form of the wave. HF radio signals reflected from the ionosphere are Doppler-shifted by these motions and can be processed to produce a record which is a faithful reproduction of the Rayleigh wave. By analyzing the ionospheric record and tracing the Rayleigh wave back to the earthquake's epicenter, the characteristics of the earthquake can be determined. This information can then be used to deduce the probability that the earthquake generated a tsunami Instrumentation for a tsunami warning system based on this method is simple and inexpensive.     

Electromagnetic versus acoustic backscattering by prolate spheroids

The exact computed values for both electromagnetic and acoustic axial backscattering by prolate spheroids of various axial ratios are compared together in the Rayleigh and the resonance regions. Interesting observations are made in the context of a previous-attempt in this direction.     

"飞行光学"焦移研究

基于焦移传输理论，推导了“飞行光学”中焦移、相对焦移的表达式，分析了“飞行距离”、瑞利长度和聚焦镜焦距对“飞行光学”中焦移、相对焦移的影响。