All-fiber coherent laser image Lidar based on phase correction.

Abstract

Owing to the weak signals produced by all-fiber coherent lidar systems, when the instability of the local oscillator laser power is greater than the target echo signal, it is difficult to extract a target's intensity image. In this study, an intensity imaging method for weak signal all-fiber lidars is proposed. First, a phase compensation method is used to correct the position of the heterodyne signal in the time domain to reduce the impact of noise on the positioning heterodyne signal. In addition, an algorithm is proposed to extract the weak echo signal from the corrected heterodyne signal in the time domain to obtain the relative intensity of the echo signal of a single pixel point. Finally, we analyze and verify the proposed imaging method by using false alarm rates, range, intensity accuracy, and the speckle characteristics of the target. The method proposed in this study only requires that the phase of the heterodyne signal be corrected by the proposed numerical method without the need for other optical equipment, thus simplifying the entire system. It is very important to improve the detection sensitivity of coherent lidar remote imaging system.