一种机载合成孔径激光雷达相位误差补偿方法

Phase Errors Compensation in Airborne Synthetic Aperture Ladar Data Processing

准确理解大气湍流扰动相位对光束传输特性的影响机制,并以此为基础发展有效的相位误差补偿算法是实现合成孔径激光雷达(SAL)高质量成像的关键之一。从激光光束的相位结构函数入手,提出了一种新的大气湍流相位屏产生方法——结构函数法,建立了满足Kolmogorov统计规律的大气湍流数值模型,计算了不同强度湍流作用下机载SAL的成像结果。通过将其与秩一相位估计法联合使用,克服了秩一法对初始值敏感的缺点,提高了补偿算法的精度和效率。实验表明,与谱反演法相比,结构函数法的计算结果更接近于理论值,同时计算复杂度由O(N^2)降至O(N)。改进的秩一法能够较为有效地改善一定强度范围内大气湍流引起的SAL图像失真,而且补偿后图像的信噪比相比传统的秩一法提高了大约5 dB,计算时间也缩短了约30%。

Accurately understanding the effects of phase fluctuation on the laser beam propagation through the atmospheric turbulence, and then making an effective wavefront correction will improve the imaging ability of practical synthetic aperture ladar systems. Based on the phase structure function of laser beam, the structure-function method for generating phase screens is presented, by which the Kolmogorov turbulence of different strength is numerically simulated to investigate its distortion on SAL imaging ability. By combining it with the rank one phase estimation （ROPE） algorithm, improvement of both accuracy and efficiency can be obtained by overcoming the weakness that ROPE is sensitive to initial value. Experiments show that the simulating results by structure function method, will be much closer to the theoretical value than that by spectrum method, and computational complexity will also be reduced from O（N2） to O（N）. At the same time, image distortion induced by atmospheric turbulence within a certain intensity range can be restored by the modified ROPE algorithm. Compared with the traditional ROPE, compensation results by the modified method can have a 5 dB signal-to-noise ratio improvement, and computing time can be cut down by 30%.