Author Affiliations
Abstract
1 Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
2 University of Chinese Academy of Sciences, Beijing 100059, China
Based on the 1 550 nm all-fiber pulsed laser Doppler vibrometer (LDV) system independently developed by our laboratory, empirical mode decomposition (EMD) and optimally modified Log-spectral amplitude estimator (OM-LSA) algorithms are associated to separate the speech micro-vibration from the target macro motion. This combined algorithm compensates for the weakness of the EMD algorithm in denoising and the inability of the OM-LSA algorithm on signal separation, achieving separation and simultaneous acquisition of the macro motion and speech micro-vibration of a target. The experimental results indicate that using this combined algorithm, the LDV system can functionally operate within 30 m and gain a 4.21 dB promotion in the signal-to-noise ratio (SNR) relative to a traditional OM-LSA algorithm.
光电子快报（英文版）
2020, 16(6): 462
1 中国科学院 长春光学精密机械与物理研究所 激光与物质相互作用国家重点实验室, 吉林 长春 130033
2 中国科学院大学, 北京 100049
3 96901部队，北京 100094
激光多普勒雷达实际测得的振动信号绝大多数都是时变信号，而基于傅立叶变换的时频分析方法是处理时变信号的有利工具。本文针对激光多普勒雷达测得的实际振动信号，比较了魏格纳-维利分布、平滑伪魏格纳-维利分布、频谱图、波恩-约旦分布和扩展修正B分布5种形式的时频分析性能。利用激光多普勒雷达测量实际单音响产生的啁啾信号振动、双音响产生的二分量啁啾信号振动、以及成年男性心跳振动3种振动，分析了时频图的分辨率和交叉项抑制情况，并通过计算时频聚集度指数，比较了5种分布情况下振动的分析性能。实验证明，扩展修正B分布的性能优于其他4种时频分布，扩展修正B分布更适合应用于激光多普勒雷达材料共振频率探测和心跳检测领域。
时频分析 激光多普勒测量 扩展修正B分布 time-frequency analysis laser doppler measurement extended modified B distribution
Author Affiliations
Abstract
1 Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
2 University of Chinese Academy of Sciences, Beijing 100049, China
In a typical infrared optical system, the “Narcissus” effect exists extensively. This concept can be extended into a heterodyne detection. In a heterodyne detection, besides the probe and local oscillator beams, a third coherent beam or even more beams caused by spurious reflection might interfere with each other on the surface of the photodetector. Generation of heterodyne signal is dependent on the interference effects between regular and unexpected waves. Based on the theory of PM demodulation, we analyze the effect of multi-beam interference competition in a laser Doppler vibrometer (LDV). A mathematical analysis demonstrates that the signal competition depends on the modulation index, the amplitude ratio of competing signals and their relative phases. The distortion of demodulated signal due to the appearance of ripples or spikes is also predicted in this study. These effects are verified by setting up an all-fiber LDV system for measuring vibration.
光电子快报（英文版）
2019, 15(3): 213
1 中国科学院 长春光学精密机械与物理研究所，吉林 长春 130033
2 激光与物质相互作用国家重点实验室,吉林 长春 130033
3 中国科学院大学，北京 100049
为了获得TEA CO2激光器高质量的单纵模输出，对种子注入锁定的TEA CO2激光器进行了研究。首先，本文提出了一种透射耦合输出的虚共焦非稳谐振腔方案，利用Glad软件的Prony法对腔模的演化进行了仿真分析，并实验记录了近场与远场的光斑光强分布。仿真结果与实验结果吻合，验证了此腔型方案的合理性。其次，在此腔型的基础上进行了腔外种子注入锁定实验，实验结果显示：自由振荡时存在频率为195 MHz的拍信号，当种子注入锁定成功后，输出激光拍频消失,波形变光滑,峰值功率降低48.6%,脉冲产生时间缩短20 ns。实验结果与已有成果吻合，验证了此种透射式非稳腔的TEA CO2激光器具有输出高质量单纵模的能力。
TEA CO2激光器 非稳谐振腔 注入锁定 单纵模 TEA CO2 lasers unstable resonator injection-locked single longitudinal mode
