提出了一种将空间激光注入光纤与相干探测技术相结合的激光无损检测方法。分析了激光超声信号的传输特征和相干光探测原理,探讨了激光无损检测的信号处理及噪声抑制方法,构建了以激光激励与检测为基础,激光注入与保偏传输为核心,图形化编程语言LabVIEW人机交互为监测手段的实验系统。实验结果表明,该系统能减小背景光的抖动对信号检测的影响;通过控制激光的光斑直径及能量可获得不同超声信号的反射波峰,有效提高了超声回波信号对材料缺陷检测的敏感性和平稳性。检测方法为工程应用提供了新的技术途径。

A nondestructive laser detection method is proposed by combining the spatial laser injection into fibers with the coherent detection technique. The transmission characteristics of laser ultrasonic signals and the principle of coherent light detection are analyzed, and the signal processing and noise suppression methods in the nondestructive laser detection are discussed. The experimental system is established based on the laser excitation and detection where the laser injection and polarization-maintaining transmission are the cores, and the human-machine interactive system based on the graphical programming language LabVIEW is the monitoring way. The experimental results show that this system can reduce the influence of background light jitter on signal detection. By controlling the spot diameter and energy, one can obtain the reflection peaks of different ultrasonic signals. The sensitivity and smoothness of the ultrasonic echo signal detection on material defects are improved effectively. The testing method provides a new technique for engineering applications.