在钢板的生产和使用过程中，钢板厚度的测量极其重要。传统的激光三角法不适合测量粗糙表面物体和多散射介质的厚度。基于硅酸铋光折变晶体搭建了一套自适应的双波混合干涉仪系统，使用该系统精确测量了铝块的厚度。由于光折变效应形成的全息光栅使信号光和参考光发生衍射，解调出超声振动信号。动态全息光栅的形成，能自动滤除环境引起的低频扰动。该系统在厚度测量、粗糙面超声振动测量中具有灵敏度高、调节方便、非接触、价格相对便宜等特点，将来与激光超声技术相结合在内部缺陷检测上有非常广阔的前景。

Measuring the thickness of metal sheets is an issue of great importance in production facilities and in other industrial applications. The conventional triangulation method is not suitable for the detection of rough surfaces and semitransparent or multi- scattering materials. Therefore, an adaptive two- wave mixing interferometer based on the photorefractive Bi12SiO20 (BSO) crystal is designed to measure the thickness of an aluminum metal sheet. A holographic grating, formed by the photorefractive effect, diffracts both the signal beam and the reference beam to demodulate the ultrasonic vibration. The system, in which the low frequency noise caused by the environmental perturbation can be filtered automatically through the dynamic holography grating, is demonstrated to be a highly sensitive, convenient, and inexpensive non- contact technique for thickness measurement and ultrasonic vibration detection on rough surfaces. The technique has the potential for the detection of hidden defects, especially when it is combined with laser ultrasonic technology.