双曲波前差自扫描直视合成孔径激光成像雷达原理

Principle of Auto-Scanning Synthetic Aperture Imaging Ladar Using Hyperbolic Wavefront Difference

提出了一种双曲波前差自扫描直视合成孔径激光成像雷达系统,结构上采用正交偏振同轴双光束发射和偏振干涉自差探测结构,原理上应用波面变换产生双曲波前差照射光斑,因此通过目标的相对运动在交轨向自动扫描产生目标面横向距离有关的线性相位调制,同时在顺轨向产生目标顺轨向距离有关的二次项相位历程,采用补偿二次多普勒频移的傅里叶变换和补偿交叉耦合的共轭二次项匹配滤波算法实现图像重构。本系统主要特点是结构简单,无需使用任何光调制器,没有交轨向信号的初始相位同步问题,不存在目标时间延时影响,同时也保留了直视合成孔径激光成像雷达的固有优点,如有效地降低了大气等相位干扰,照明光斑可以很大,接收口径可以很大。本雷达适用于航空航天的各种相对运动速度和作用距离的对地观察成像和基于逆合成孔径原理的激光成像雷达。

A kind of auto-scanning down-looking synthetic aperture imaging ladar（SAIL） is proposed, which in construction uses two coaxial orthogonally polarized beams in transmitter and polarization interference based self-heterodyning detection in receiver and in principle adopts the wavefront transformation to generate illumination wavefronts with a hyperbolic spatial phase difference. Therefore, the wavefront scanning from the relative movement of target produces automatically the necessary linear phase modulation in the orthogonal direction of travel, and the quadratic phase history in the travel direction as well. The image is reconstructed by virtue of the Fourier transform with the Doppler quadratic compensation in the orthogonal direction of travel and the conjugate quadratic phase matched filtering with the crossed coupling compensation in the travel direction. The system is very simple in structure. Optical modulator isn′ t used. The initial phase synchronization for linear phase modulations doesn′t exist. The time delay of target doesn′t exist, too. And the advantages of the original down-looking SAIL remains such as the availability of big receiving aperture and big optical footprint, and the capability of suppression of phase interferences from atmospheric turbulence and others. The suggested SAIL is of practical potentials to applying for spaceborne and airborne observation or inverse-SAIL radar under every workable distance and speed.