低频液体表面波的激光干涉测量

对于频率为几十赫兹的液体表面声波,提出了一种激光干涉测量方法,并在实验上观察到了反射光所形成的稳定的、清晰的调制干涉图样,干涉图样被限制在一定的空间区域内,其强度分别在两边界位置达到极大,形成了两个极亮点.理论上导出了调制干涉图样光强度、干涉条纹角宽度、干涉区域角宽度与表面声波之间的解析关系,并与实验数据进行了对比.基于这一发现,建立起一种适应测量低频表面声波特性及表面张力的实用方法.

Measurement of Low-Frequency Surface Acoustic Wave on Liquid Surface by Means of Laser Interference

A laser interference technique for measuring liquid surface acoustic wave at a few tens Hertz was designed and the high visibility and modulated interference fringes, which are formed by the reflective light beam from the liquid surface, were obtained experimentally. The interference fringes are confined in a certain space range and the double brightest spots locate at the both extreme positions of this range. An analytic intensity expression of the light from the liquid surface, the angle space of the interference fringes and the angle width of the interference fringe range with the surface acoustic wave were derived theoretically. The results show that the theory predication is well consistent with experimental data. Moreover, a practical technique can be developed, based on the discovery, to measure the properties of the surface wave at these frequencies and the dynamic surface tension.