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当外部激光被反射回激光内腔时,反馈光与激光器腔内光混合,调制激光器的输出功率和频率,通过信号处理可以得到物体运动的多普勒频率,从而计算出物体的运动速度。基于这种特性,设计出一种激光自混合干涉仪,为了知道该技术是否适用于变速测量,对激光自混合用于变速运动物体的速度测量进行了探索。基于激光自混合三镜腔模型,建立了激光自混合用于变速测量的数学模型,提出了基于该模型的特征参量提取方法,该方法基于离散Chirp-Fourier变换理论。对激光自混合输出信号进行离散Chirp-Fourier变换,变换结果的主瓣坐标反映了物体运动的速度及加速度信息。最后,对该方法进行了仿真分析,在SNR=0 dB和SNR=7 dB的情况下,能较好地获得物体的速度和加速度信息。因此,仿真试验证明:该方法在较低信噪比的情况下仍能有效提取物体的速度及加速度信息。
When the external laser is reflected back to the laser cavity, the feedback light is mixed with the laser cavity light to modulate the output power and frequency of the laser, and the Doppler frequency of the object movement can be obtained through signal processing to calculate the object moving speed. Based on this feature, a laser self-mixing interferometer was designed. In order to know whether this technology is suitable for variable speed measurement, the speed measurement of variable speed moving objects by laser self-mixing was explored. Based on the laser self-mixing three-cavity model, a mathematical model of laser self-mixing for variable speed measurement is established, and the method of feature parameter extraction based on the model is proposed. The method is based on discrete Chirp-Fourier transform theory. Discrete Chirp-Fourier transform is applied to the laser self-mixing output signal. The mainlobe coordinates of the transformed result reflect the velocity and acceleration information of the object. Finally, the method is simulated and analyzed, and the object velocity and acceleration information can be obtained well with SNR = 0 dB and SNR = 7 dB. Therefore, the simulation results show that this method can still extract the object’s velocity and acceleration information effectively even at low signal-to-noise ratio.