可调谐激光器的光束特性对合成孔径激光雷达成像质量的影响研究

Synthetic aperture ladar (SAL), which applies synthetic aperture radar (SAR) techniques in the optical laser radar domain, can theoretically provide centimeter-class resolution with a small-diameter optical aperture in 1000 km, thus it has great potential in such field of military and civil applications as aviation, aerospace and everiment monitoring. To obtain high signal bandwidth and realize high resolution image , a tunable laser is often used in synthetic aperture ladar as the light source. During the broadband tuning process, the beam properties will become the factors that can not be ignored for that affect the imaging quality of synthetic aperture ladar. This research presents an in-depth study on the influence of beam property on the imaging quality of synthetic aperture ladar with the heterodyne detection system. By means of simulation analysis and experiment,such measures can be used to improve the imaging quality of synthetic aperture ladar as optimizating of beam model, reducing the output signal phase error and raising the peak sidelobe ratio of point target response.At the same time, the influence of wavelength repeat in tunable laser can be reduced on image quality by designing optical bandpass filtering with Zemax software . The meaabove-mentioned measures can improve synthetic aperture ladar system stability, impact resistance, safety. The research result may provide a reference for the synthetic aperture ladar system in reality.

合成孔径激光雷达是合成孔径雷达在光学波段的拓展，是现阶段能够对上千公里目标实现厘米量级分辨率的唯一光学遥感手段，在航空、航天、环镜监测等领域有着巨大的应用价值。为了获得大信号带宽、实现高分辨率探测成像，合成孔径激光雷达常采用可调谐激光器作为光源。在宽带调谐过程中，激光器的光束特性将成为影响合成孔径激光雷达成像质量不可忽视的因素。本项目拟针对周期性调谐过程中可调谐激光器的输出光束特性对合成孔径激光雷达成像质量的影响机理进行深入研究。采用模拟分析和实验验证的方法，通过优化光束模型、降低输出信号相位误差等因素对成像质量的影响，获得高峰值旁瓣比的点目标响应，从而提高合成孔径激光雷达的成像质量。同时，利用Zemax软件设计光学带通滤波器从而实现对可调谐激光器输出光束的优化，降低波长重复度对成像质量的影响，提高合成孔径激光雷达系统的稳定性、抗冲击性、安全性，为合成孔径激光雷达系统走向实用化提供参考。

合成孔径激光雷达是合成孔径雷达在光学波段的拓展，是现阶段能够对上千公里目标实现厘米量级分辨率的唯一光学遥感手段，在航空、航天、环镜监测等领域有着巨大的应用价值。为了获得大信号带宽、实现高分辨率探测成像，合成孔径激光雷达常采用可调谐激光器作为光源。在宽带调谐过程中，激光器的光束特性将成为影响合成孔径激光雷达成像质量不可忽视的因素。本项目重点围绕可调谐激光器输出光束的频率非线性、起始波长误差和光束模型对合成孔径激光雷达成像的影响展开研究。首先建立可调谐激光器调谐过程中输出光束相位误差的理论模型，研究可调谐激光器由调谐产生的相位误差对合成孔径激光雷达成像分辨率的影响规律，利用相位补偿算法提高合成孔径激光雷达在距离向的成像分辨率。分析可调谐激光器输出波长的起始波长误差对合成孔径激光雷达方位向和距离向成像的影响，研究了合成孔径激光雷达成像中光谱定标方法及流程，分析了该方法的特点及局限；进一步提出了一种更为优化的标定方法，通过设计光学带通滤波器实现对对合成孔径激光雷达的起始波长误差的校订。结合可调谐激光器实际输出光束的特点以及合成孔径激光雷达对光源的需求，构建了时间超高斯线性调频光束模型，分析了时间超高斯线性调频信号的特性，推导了时间超高斯线性调频光束模型经过合成孔径激光雷达系统后的传输公式，并模拟了时间超高斯线性调频光束经过合成孔径激光雷达系统后的点目标成像。本项目针对影响合成孔径激光雷达成像的频率非线性、起始波长误差和光束模型等光束特性给出了相应的优化设计，为合成孔径激光雷达系统的实用化提供了参考。