Foote Kenneth G, Theobald Peter D
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA.
National Physical Laboratory, Teddington TW11 0LW, United Kingdom.
J Acoust Soc Am. 2015 Sep;138(3):1627-36. doi: 10.1121/1.4929372.
The acousto-optic effect, in which an acoustic wave causes variations in the optical index of refraction, imposes a fundamental limitation on the determination of the normal velocity, or normal displacement, distribution on the surface of an acoustic transducer or optically reflecting pellicle by a scanning heterodyne, or homodyne, laser interferometer. A general method of compensation is developed for a pulsed harmonic pressure field, transmitted by an acoustic transducer, in which the laser beam can transit the transducer nearfield. By representing the pressure field by the Rayleigh integral, the basic equation for the unknown normal velocity on the surface of the transducer or pellicle is transformed into a Fredholm equation of the second kind. A numerical solution is immediate when the scanned points on the surface correspond to those of the surface area discretization. Compensation is also made for oblique angles of incidence by the scanning laser beam. The present compensation method neglects edge waves, or those due to boundary diffraction, as well as effects due to baffles, if present. By allowing measurement in the nearfield of the radiating transducer, the method can enable quantification of edge-wave and baffle effects on transducer radiation. A verification experiment has been designed.
声光效应是指声波引起光学折射率的变化，这对通过扫描外差或零差激光干涉仪确定声换能器或光学反射薄膜表面的法向速度或法向位移分布施加了基本限制。针对由声换能器发射的脉冲谐波压力场，开发了一种通用的补偿方法，其中激光束可以穿过换能器近场。通过用瑞利积分表示压力场，将换能器或薄膜表面未知法向速度的基本方程转化为第二类弗雷德霍姆方程。当表面上的扫描点对应于表面积离散化的点时，数值解很容易得到。对于扫描激光束的斜入射角也进行了补偿。目前的补偿方法忽略了边缘波或边界衍射引起的波，以及如果存在的话由障板引起的效应。通过允许在辐射换能器的近场中进行测量，该方法可以量化边缘波和障板对换能器辐射的影响。已经设计了一个验证实验。
