第 42 卷 第 8 期
2015 年 8 月
Vol. 42, No. 8
August, 2015
中 国 激 光
CHINESE JOURNAL OF LASERS
0808002-
Thickness Measurement of a Metal Sheet by an Adaptive Two-Wave
Mixing Interferometer
Duan Changqi Chen Jian He Sailing
Centre for Optical and Electromagnetic Research, Zhejiang Provincial Key Laboratory for Sensing Technologies, State
Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, Zhejiang 310058, China
Abstract 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 Bi
12
SiO
20
(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.
Key words measurement; two-wave mixing; holography grating; metal sheet; ultrasonic
OCIS codes 120.3180; 050.1950
基于自适应双波混合干涉仪的金属板厚度测量
段昌琪 陈 剑
*
何赛灵
浙江大学现代光学仪器国家重点实验室, 浙江省传感重点实验室, 光及电磁波研究中心, 浙江 杭州 310058
摘要 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。
关键词 测量; 双波混合; 全息光栅; 金属板; 超声
中图分类号 TH741; O438.1 文献标识码 A
doi: 10.3788/CJL201542.0808002
收稿日期: 2015-03-02; 收到修改稿日期: 2015-04-17
基金项目: 国家自然科学基金(61401392)、中国博士后科学基金(2014M551729)
作者简介: 段昌琪(1991—),男,硕士研究生,主要从事光学精密测量方面的研究。E-mail: duanchangqi@zju.edu.cn
导师简介: 何赛灵(1966—),男,教授,博士生导师,主要从事生物光学、光学测量等方面的研究。E-mail: sailing@jorcep.org
*通信联系人。E-mail: mechenjian@zju.edu.cn
1 Introduction
Accurately measuring the dimensions of metal sheets by automated, non-contact methods become an increasingly
important issue. The thickness must be monitored during metal production to improve quality and yield;
measurements are also required during practical applications to ensure good performance
[1]
. To meet these needs,
several non- contact optical methods have been used to detect the thickness of metal sheets, such as double-sided
laser point triangulation
[1- 2]
, light attenuation, and autofocus
[3]
techniques. The best- known technique, which is
1