激光超声诱导与光学相干探测方法研究

Aimed at the disadvantages of traditional ultrasonic testing in precision, speed, noise suppression, reliability and SNR improvement, a technique for ultrasonic testing based on laser-induced ultrasound technology and optical coherent detection is put forward. In this project, by using laser-induced ultrasound theory and optical coherent-balanced detection technology, the impact that fundamental frequency modulation of laser (the inducing source) has on the generated ultrasound signals is analyzed. Based on optoacoustic effect caused by the interaction of laser and medium, nondestructive testing can be realized by analyzing the induced ultrasonic signal characteristics. By coupling beams into fiber and adopting coherent-balanced detection, solutions to noise suppression and SNR improvement in laser measurement technology are studied, which explores a new laser-based metrical way. Simulation and experimental platforms are established, where optoacoustic conversion efficiency for the interaction of laser and medium is further analyzed. Meanwhile, to achieve goals of high stability and anti- jamming ability, the impact that optical matching has on sensitivity and stability is researched, and optical methods and measures for noise suppression in optical coherent detection are discussed, which provides a new technique for laser-based measurement.

针对传统超声产品检测精度、测量速度、噪声抑制、探测可靠性及信噪比改善等方面的不足，提出一种激光超声诱导与光学相干探测方法，项目以激光超声诱导机理为基础，运用光声效应理论与光学相干平衡探测技术，分析激光诱导源基频调制对超声信号形成的影响关系，利用激光与介质互作用的光声效应，通过对激励的超声信号特征分析实现物体的无损检测，研究激光测量技术中噪声抑制与信噪比改善，采用空间光耦合与相干平衡探测技术，探索一种新的激光测量方法。通过建立系统仿真和实验测试平台，进一步分析激光与介质互作用的光声转换效率关系，研究相干探测光学匹配对探测灵敏度和输出稳定性的影响，探讨光学相干检测噪声抑制方法与措施，达到提高光学测量信号稳定性和抗干扰能力目的，为激光测量提供一种新的技术途径。

针对传统超声产品检测精度、测量速度、噪声抑制、探测可靠性及信噪比改善等方面的不足，提出一种激光超声诱导与光学相干探测方法，项目以激光超声诱导机理为基础，运用光声效应理论与光学相干平衡探测技术，分析激光诱导源基频调制对超声信号形成的影响关系，利用激光与介质互作用的光声效应，通过对激励的超声信号特征分析实现物体的无损检测，研究激光测量技术中噪声抑制与信噪比改善，采用空间光耦合与相干平衡探测技术，探索一种新的激光测量方法。通过建立系统仿真和实验测试平台，进一步分析激光与介质互作用的光声转换效率关系，研究相干探测光学匹配对探测灵敏度和输出稳定性的影响，探讨光学相干检测噪声抑制方法与措施，达到提高光学测量信号稳定性和抗干扰能力目的。. 本项目进行了激光激励超声信号机理、激光超声在金属固体中传播特性、回波信号采集处理、相干光检测等技术研究，对几种典型的铝、不锈钢、铁金属材料进行缺陷检测对比，得到光声转换效率、超声传播衰减特性、缺陷对激光超声跃变的回波响应与金属材料的性质有密切关系。. 项目完成了激光超声无损检测实验演示系统搭建和测试，通过激光的注入处理、相干光探测技术、微弱信号采集和LabVIEW建立的上位机虚拟分析系统，较好实现金属材料的实时检测分析，其抗干扰能力、弱信号检测能力和信号测量精度都有一定提升，测试精度优于几毫米，相比传统接触式检测系统优势明显，为无损检测领域的应用研究提供一种新的技术方法。