摘要
调频连续波(Frequency Modulated Continuous Wave,FMCW)激光雷达以其探测精度高、测距测速一体、抗干扰能力强等优势,广泛应用于目标探测、成像、定位与跟踪等领域。针对探测目标表面散射引起的偏振态变化导致回波光与本征光偏振失配现象,从目标探测与识别的角度出发,提出了一种基于偏振正交解调FMCW激光雷达探测系统,通过控制回波偏振态解决因偏振失配造成的探测能力减弱和探测距离受限的问题。实验结果表明,在相同测试环境下,相较于典型探测方式,六种典型目标边模抑制比分别提升了11.85%、11.98%、13.46%、15.39%、17.12%、18.29%。进一步实验表明,通过调整波片夹角(22.5°、45°、60°),得到当波片夹角为45°时,测距标准差取得最小值0.012 m,边模抑制比最高可提升至16.931 dB。通过对回波偏振态的研究,为FMCW激光雷达在目标识别应用提供一定的技术支撑。
Objective Lidar detects targets by actively emitting and receiving laser signals,and obtains information such as the target's distance,speed,and direction from the reflected echo.FMCW lidar is a ranging technology based on frequency modulated continuous wave signals,combining the advantages of frequency modulated continuous wave ranging and laser detection.This technology transmits a frequency modulated continuous wave to the target,mixes the signal light with the intrinsic light,and uses the beat frequency signal generated by laser interference to calculate the distance and speed of the target,thereby achieving high-precision distance and speed measurement.It has the characteristics of integrated distance and speed measurement and strong anti-interference ability.However,during laser transmission,depolarization effects may occur due to atmospheric turbulence or reflection from the target surface,resulting in polarization mismatch between the echo light and the intrinsic light.This polarization mismatch can significantly reduce the heterodyne efficiency,signal-to-noise ratio,maximum detection distance,and detection accuracy of the system.Therefore,in order to achieve high-precision long-distance detection,research on the polarization characteristics of FMCW lidar echoes has important academic significance and application value.Methods In actual detection of FMCW laser radar,the polarization matching degree between signal light and intrinsic light directly determines the heterodyne efficiency of coherent detection,which in turn affects the signalto-noise ratio,detection distance and accuracy of the FMCW laser radar system.Since the polarization state of the intrinsic light remains stable when it is transmitted in the polarization-maintaining fiber,and the polarization state of the signal light changes due to the scattering of the detection target surface when it is received by the optical system after undergoing a complex atmospheric propagation process.Therefore,it is particularly important to analyze the polarization characteristics of the echo in order to better understand its impact on the performance of the FMCW laser radar system.Based on the optimization and improvement of the traditional FMCW laser radar detection principle,a new detection system based on polarization orthogonal demodulation is proposed.A 1/4 wave plate is added to the incident end of the signal light,and the different polarization states of the signal light are simulated by changing the fast axis angle of the wave plate.The intensity of the balanced detector output signal is analyzed and verified.Results and Discussions In view of the polarization mismatch between the echo light and the intrinsic light caused by the change of polarization state caused by the surface scattering of the detection target,this paper analyzes and studies the detection performance of FMCW laser radar based on polarization orthogonal demodulation from the perspective of target detection and recognition,effectively solving the problems of weakened detection capability and limited detection distance caused by polarization mismatch.The experimental results show that under the same test environment,compared with the typical detection method,the side mode suppression ratio of the six detection targets(reflector,quadcopter UAV,bird feather,green luo,marble,plastic bag)is improved by 11.85%,11.98%,13.46%,15.39%,17.12%,and 18.29%respectively.Further experiments show that by adjusting the wave plate angle(22.5°,45°,60°),when the wave plate angle is 45°,the ranging standard deviation reaches the minimum value of 0.012 m,and the side mode suppression ratio can be increased to 16.931 dB.Through the study of the echo polarization state,further theoretical support is provided for the application of FMCW laser radar in target recognition.Conclusions This article combines polarization information with FMCW laser radar technology to provide theoretical basis for the polarization characteristics of echoes,expand their applications in military,autonomous driving,and industrial detection fields,improve target recognition,low reflectivity target detection,and environmental perception capabilities,solve the recognition limitations of traditional laser radar in complex environments,and provide theoretical support for high-precision target recognition and system optimization design.
作者
刘宇
姜成昊
袁野
解天鹏
平步云
朱精果
LIU Yu;JIANG Chenghao;YUAN Ye;XIE Tianpeng;PING Buyun;ZHU Jingguo(Institute of Microelectronics of the Chinese Academy of Sciences,Beijing 100029,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《红外与激光工程》
北大核心
2025年第7期165-176,共12页
Infrared and Laser Engineering
基金
北京市自然科学基金-丰台创新联合基金项目(2024FTZD010)。
关键词
激光雷达
调频连续波
偏振正交解调
目标识别
lidar
frequency modulated continuous wave
polarization quadrature demodulation
target identification
