Study On Experiment And Algorithm Of Synthetic Aperture Imaging Lidar

Synthetic aperture technique is from microwave imaging, which makes use of the motion between the radar platform and the target to synthesize the virtual aperture in order to improve the resolution. The resolution of the synthetic aperture technique is restricted by the wavelength of the carrier and there is no end for people in pursuit of higher resolution. The characters of the laser are good in direction, good in stability of the frequency and good correlation in space and time. Compared with microwave, the wavelength of laser is much smaller. In other words, a better resolution can be obtained. Though synthetic aperture imaging lidar can achieve amazing resolution as the combination of the synthetic aperture technique and laser technique, there are still many difficulties to be overcome, such as system design, imaging algorithm and so on.The work in this paper is around the key technique of synthetic aperture, including analysis of key techniques, study on the range dimension, system design of the indoor synthetic aperture imaging lidar, algorithm of data processing, analysis of the effect of the turbulence, system design of an airborne synthetic. Finally, the simulation experiment and the real experiment were set up to prove the feasibility of the system and the validity of the algorithm. This paper is organized as follows:Chapter 1 is the introduction. It reviews the histories of synthetic aperture technique and synthetic aperture imaging lidar development. And it introduces the dissertation's research main work.Chapter 2 introduces the principle of the synthetic aperture and inverse synthetic aperture techniques. Then, it gives the key techniques of the synthetic aperture imaging lidar in detail.Chapter 3 studies the synthetic aperture imaging lidar in range dimension. Due to the non-linear frequency of the signal transmitted by the laser source, the range compression will be deteriorated. The problems of the non-linear frequency and the signal receiving are discussed. Then, a compensation algorithm for pulse's high-order phase error is given which is based on the reference channel and performed in the time domain. The work of this chapter is well prepared for the two dimensional imaging.Chapter 4 studies the two dimensional imaging. A system of inverse synthetic aperture is proposed, which makes use of the transmitted and the received lens apart in order to eliminate the interference efficiently. And the real data from the system proves the validity of the system. Finally, an image of the inverse synthetic aperture was obtained, which is the first inverse synthetic aperture imaging in the domestic.Chapter 5 studies the algorithm of the synthetic aperture imaging lidar. We start with the signal model of the synthetic aperture imaging lidar, analyze the geometry of the imaging and propose two algorithms which are suitable for the side-looking and the spot model separately. And then simulation of Phase Screen (PS) distorted by atmospheric turbulence following the von Karman spectrum by using Fourier Transform is implemented in order to simulate turbulence. The effect of the turbulence is discussed, which deteriorate the azimuth compression. And it will be useful for the synthetic aperture imaging lidar experiment in the future.Chapter 6 designs a system suitable for the synthetic aperture imaging lidar. Firstly, the contradiction between the modulating of the laser source and the pulse repetition frequency is analyzed. Then, the Doppler frequency shift of the given system was analyzed and the method of the compensation for the Doppler frequency shift was given. And then, a data processing method of the system was given. Finally, the simulation proves the validity of the given system and the algorithm of the data processing.Chapter 7 is the summary of the dissertation. It also discusses future research areas to be further studied.