The System Design And Experiments Of The Self-aligning Micro-Pulse Lidar

Micro-pulse lidar is an effective tool for detecting atmospheric aerosol and cloud,which can improve the continuous observation of aerosol and cloud optical propertiesand spatial distribution. In addition to hardware system of lidar meeting the detectionneeds, a transmitter-receiver self-aligning system and a software system easy tooperate are essential for automatic observations.This paper is based on developing a self-aligning micro-pulse lidar system mixedhardware and software. Firstly, several micro-pulse lidar with higher degree ofautomation in the international and their parameters are introduced. Secondly, thedetection principle of lidar and Fernald method to inverse the atmospheric extinctioncoefficients are introduced.In the main part of the paper, transmitter-receiver self-aligning method is firstlydescribed, two commonly alignment methods and their applications are introducedand compared. This paper uses the self-aligning method based on maximizing thebackscattering optical signal received to adjust the transmitting optical axis. Secondly,in the design of lidar hardware system, we use a laser with532nm,6μJ and3kHz astransmitter, a two-dimensional adjusting mirror with stepper motor controlled toadjust the transmitting optical axis. The receiver is a compact Schmidt-Cassegraintelescope. PMT(Photomultiplier) works on photon counting mode to improve thedetection performance. The software system consists of four main components: thesoftware for the data acquisition, for the extinction coefficients and THI(Time-heightindication) inversion in the real time and for the transmitting optical axis manuallyand automatically adjusted, which are all designed by LabVIEW(Laboratory VirtualInstrument Engineering Workbench). The design processes and methods are analyzed. The software system can be better used in the data acquisition, data inversion, systemmonitoring and optical axis control of micro-pulse lidar. And then, mechanical designof the entire system is done.In the experiments, the lidar’s performance is tested. Atmospheric backscatteringdata and the extinction coefficients can be used to observe atmospheric state andaerosol distribution, THI figure can be used to observe temporal and spatial changesof the aerosol and clouds optical properties. Some results are showed and the methodsof calculating cloud bottom and top are analyzed. Finally, this paper is concluded andthe improvements of the system for the future are pointed out.