纳米级激光外差干涉检测系统的设计与实现

发布时间：2018-04-26 12:15

本文选题：纳米位移检测 + 激光外差干涉　；参考：《中北大学》2017年硕士论文

【摘要】：激光外差干涉非接触式的特点使其成为无损检测领域重要的组成部分,对于某些特殊行业来说,能够实现纳米级别的高精度检测显得尤为重要。本文旨在设计并实现纳米级激光外差干涉检测系统,首先对激光外差干涉检测原理进行阐述,对光路结构进行优化,实现差分双光路。分析了光路系统非线性误差来源,将具体误差归为两类进行数学推导,建立起误差模型并进行仿真,对光路系统所用的主要器件进行性能测试及分析。其次,介绍了目前常用的几种激光外差干涉信号处理方法,选择使用FPGA对纳米级激光外差干涉检测系统进行信号处理,设计出所需的三个模块,分别进行仿真验证。最后将采集到的信号处理完并在整体仿真图中显示出来。通过压电陶瓷静态实验、动态实验的数据分析,证明了系统抗噪性能的优越,动态实验中对振动信号解调得到的电压信噪比达到32.1dB,干扰信号强度不到主频信号的2.6%,对振动信息(位移信息)解调的还原度高。在脉冲激光器激励实验中,样品与整形后的脉冲点光源距离50mm处,在宽频范围内检测到4.59nm,2.18nm两个主要位移,对应振动频率分别为1.7MHz、7.4MHz,证明了样品内部存在缺陷。样品距整形后点光源距离分别80mm、60mm处,FPGA解调出的主要位移分别为104.8058nm、18.037nm。
[Abstract]:The non-contact laser heterodyne interference makes it an important part in the field of nondestructive testing. For some special industries, it is very important to realize high-precision detection at nanometer level. The purpose of this paper is to design and implement the laser heterodyne interferometric detection system. Firstly, the principle of laser heterodyne interference detection is expounded, the structure of the optical path is optimized, and the differential double optical path is realized. The source of nonlinear error of optical path system is analyzed, the concrete error is classified into two kinds of mathematical derivation, the error model is established and simulated, and the performance of the main devices used in optical circuit system is tested and analyzed. Secondly, several commonly used methods of laser heterodyne interference signal processing are introduced. FPGA is chosen to process the signal of nanometer level laser heterodyne interferometry detection system. Three modules are designed and simulated respectively. Finally, the collected signal is processed and displayed in the overall simulation diagram. The static and dynamic experiments of piezoelectric ceramics show that the anti-noise performance of the system is superior. In dynamic experiment, the signal to noise ratio (SNR) of the vibration signal demodulated is 32.1dB, the interference signal intensity is less than 2.6dB of the main frequency signal, and the reduction degree of the vibration information (displacement information) demodulation is high. In the experiment of pulse laser excitation, two main shifts at 4.59 nm ~ 2.18 nm and corresponding vibration frequency of 1.7 MHz ~ (7.4 MHz) were detected in the wide frequency range from the sample to the pulse point light source (50mm) after shaping. It is proved that there are defects in the sample. The main displacement demodulated by FPGA is 104.8058nm ~ 18.037nm respectively at the distance of 80mm ~ 60mm from the sample to the point light source after shaping.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN24

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