半导体激光自混合变速测量的离散Chirp-Fourier变换方法

Invariable acceleration velocity measurement using self-mixing laser diode based on discrete Chirp-Fourier transform method

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。

Laser output power and frequency are modulated when the optical beam is back-scattered into the active cavity.By signal processing,the Doppler frequency can be acquired,and the target′s velocity can be calculated.Based on these properties,a self-mixing interferometer was designed.In order to know whether the technology is suitable for time-varying velocity measurement,the time-varying velocity measurement by self-mixing laser diode was explored.Based on the three-mirror cavity model,a mathematics model was established for the time-varying velocity measurement by self-mixing laser diode.Based on this model,a discrete Chirp-Fourier transform（DCFT） method was applied.To change the self-mixing laser diode output signal by DCFT,the coordinates of the main lobe showed the target′s velocity and acceleration information.At last,the numerical simulation analysis was carried out when SNR=0 dB and SNR=7 dB.The simulation result shows that under the low SNR conditions,through the DCFT method the object′s velocity and acceleration information still can be extracted.So,the simulation results prove the validity of the algorithm even in the situation of low SNR.