激光超声激励与检测技术研究
发布时间：2018-12-17 17:26
【摘要】：由于激光超声具有波长短，方向性强，遇障碍物产生衍射和散射等特点，日益成为无损检测领域重要研究内容。本文主要通过仿真与实验的方法，从激光超声激励与检测系统构成与原理出发，重点研究了激光超声激励与检测技术。 以激光超声激发机理为基础，对激光超声激励关键技术进行了分析，设计了激光点源聚焦和激光一维扩束线源两种激励源空间调制模块，设计过程中充分考虑激励源高功率、不连续、不可见的特点。点源聚焦模块采用倒立望远镜系统改善光束质量后再进行聚焦，输出光斑可实现100m-1000m连续可调。针对一维扩束线源模块提出了基于单一柱透镜和基于鲍威尔棱镜与菲涅尔透镜相结合的两种设计方案，柱透镜方案设计过程中利用光学仿真软件分析了柱透镜成像规律，根据其输出线源呈线型高斯分布的特点，提出了用精密光阑截取能量集中部分用于实验的解决方案。依据鲍威尔棱镜线型公式利用Solidworks软件建立了模型，并导入光学分析软件进行仿真，结果显示输出线源达到了良好的均匀性。 对常用的激光超声光学检测法相关理论及可行技术方案进行研究，提出新型激光超声检测系统设计方案。该设计利用声光调制器在信号中引入一个载波频率，利用高频调制手段提高信号的稳定性和系统的抗干扰能力；通过双光路差分原理消除了环境噪声对干涉信号的影响；利用偏振特性，，使相同偏振态的光进行干涉，大幅提高干涉信号幅值；通过增加聚焦透镜组，进一步提高系统灵敏度。针对激光外差信号的特点，设计了以AD8302为核心的相位解调模块。该模块利用AD8302良好高频测相能力以及外围相关电路的设计，解决了现有电路系统的诸多问题。其理论分辨率可以达到0.1nm，从而实现更高精度的激光外差干涉信号处理，并且该芯片能检测两干涉信号幅值比，实时监控激光外差光路干涉质量。 最后搭建了激光超声激励与检测系统，对各模块功能进行了实验验证，实现了对超声信号的激励与检测。结果表明本设计可提高激光超声激发效率，超声检测系统信噪比高，有利于高频微弱激光超声信号检测。
[Abstract]:Because of the characteristics of short wavelength, strong directionality, diffraction and scattering due to obstacles, laser ultrasound has become an important research field in the field of nondestructive testing (NDT). In this paper, by means of simulation and experiment, the laser ultrasonic excitation and detection technology is studied based on the structure and principle of laser ultrasonic excitation and detection system. Based on the principle of laser ultrasonic excitation, the key technology of laser ultrasonic excitation is analyzed. Two kinds of spatial modulation modules of laser point source focusing and laser one-dimensional beam spreading source are designed. The high power of excitation source is fully considered in the design process. The quality of being discontinuous or invisible. The point source focusing module uses the inverted telescope system to improve the beam quality before focusing, and the output spot can be continuously adjustable by 100m-1000m. Two design schemes based on single cylindrical lens and Powell prism and Fresnel lens are proposed for one-dimensional beam spreading source module. The imaging law of cylindrical lens is analyzed by optical simulation software in the design process of cylindrical lens. According to the linear Gao Si distribution of the output line source, the solution of using precision aperture to intercept the energy concentration part for experiment is put forward. According to Powell's prism linear formula, the model is established by Solidworks software, and the optical analysis software is introduced to simulate the model. The results show that the output line source has achieved good uniformity. The relevant theory and feasible technical scheme of laser ultrasonic optical detection method are studied, and a new design scheme of laser ultrasonic detection system is put forward. In this design, an acousto-optic modulator is used to introduce a carrier frequency into the signal, the high frequency modulation is used to improve the stability of the signal and the anti-interference ability of the system is improved, and the influence of environmental noise on the interference signal is eliminated by the principle of double optical path difference. By using the polarization characteristic, the interference of the same polarization state light can be carried out, and the amplitude of the interference signal will be greatly increased, and the sensitivity of the system can be further improved by increasing the focusing lens group. According to the characteristics of laser heterodyne signal, a phase demodulation module based on AD8302 is designed. This module solves many problems of the current circuit system by using the good high frequency phase measurement ability of AD8302 and the design of peripheral related circuits. The theoretical resolution can reach 0.1 nm, which can achieve higher precision processing of laser heterodyne interference signal, and the chip can detect the amplitude-value ratio of two interference signals and monitor the interference quality of laser heterodyne optical path in real time. Finally, a laser ultrasonic excitation and detection system is set up, and the function of each module is verified experimentally, and the excitation and detection of ultrasonic signal is realized. The results show that this design can improve the efficiency of laser ultrasonic excitation, and the signal-to-noise ratio of ultrasonic detection system is high, which is beneficial to the detection of high frequency weak laser ultrasonic signals.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN247
本文编号：2384557
[Abstract]:Because of the characteristics of short wavelength, strong directionality, diffraction and scattering due to obstacles, laser ultrasound has become an important research field in the field of nondestructive testing (NDT). In this paper, by means of simulation and experiment, the laser ultrasonic excitation and detection technology is studied based on the structure and principle of laser ultrasonic excitation and detection system. Based on the principle of laser ultrasonic excitation, the key technology of laser ultrasonic excitation is analyzed. Two kinds of spatial modulation modules of laser point source focusing and laser one-dimensional beam spreading source are designed. The high power of excitation source is fully considered in the design process. The quality of being discontinuous or invisible. The point source focusing module uses the inverted telescope system to improve the beam quality before focusing, and the output spot can be continuously adjustable by 100m-1000m. Two design schemes based on single cylindrical lens and Powell prism and Fresnel lens are proposed for one-dimensional beam spreading source module. The imaging law of cylindrical lens is analyzed by optical simulation software in the design process of cylindrical lens. According to the linear Gao Si distribution of the output line source, the solution of using precision aperture to intercept the energy concentration part for experiment is put forward. According to Powell's prism linear formula, the model is established by Solidworks software, and the optical analysis software is introduced to simulate the model. The results show that the output line source has achieved good uniformity. The relevant theory and feasible technical scheme of laser ultrasonic optical detection method are studied, and a new design scheme of laser ultrasonic detection system is put forward. In this design, an acousto-optic modulator is used to introduce a carrier frequency into the signal, the high frequency modulation is used to improve the stability of the signal and the anti-interference ability of the system is improved, and the influence of environmental noise on the interference signal is eliminated by the principle of double optical path difference. By using the polarization characteristic, the interference of the same polarization state light can be carried out, and the amplitude of the interference signal will be greatly increased, and the sensitivity of the system can be further improved by increasing the focusing lens group. According to the characteristics of laser heterodyne signal, a phase demodulation module based on AD8302 is designed. This module solves many problems of the current circuit system by using the good high frequency phase measurement ability of AD8302 and the design of peripheral related circuits. The theoretical resolution can reach 0.1 nm, which can achieve higher precision processing of laser heterodyne interference signal, and the chip can detect the amplitude-value ratio of two interference signals and monitor the interference quality of laser heterodyne optical path in real time. Finally, a laser ultrasonic excitation and detection system is set up, and the function of each module is verified experimentally, and the excitation and detection of ultrasonic signal is realized. The results show that this design can improve the efficiency of laser ultrasonic excitation, and the signal-to-noise ratio of ultrasonic detection system is high, which is beneficial to the detection of high frequency weak laser ultrasonic signals.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN247
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