Experimental Research On Intensity Distribution Of Typical Target Echo Signal Of Lidar

Target recognition based on echo intensity is an important aspect of lidar target detection, so it is very necessary to investigate the echo intensity and its distribution of the target. In this paper, based on the two functions of the bidirectional reflectance distribution function（BRDF） and the laser radar cross section（LRCS）, which describe the target’s laser scattering characteristics, the target echo intensity is investigated.Firstly, it introduces the theories of BRDF, LRCS and the effect of laser propagation in atmosphere, and it investigates the integral relation between BRDF and LRCS and the relationship with the laser radar equation, at the same time, the numerical simulation method of laser atmospheric turbulence transmission based on FFT spectrum inversion method is studied, and FFT spectrum inversion method with the second harmonic compensation method can effectively improve the accuracy of the phase screen simulation;Secondly, it utilizes single station lidar to measure the unit-area LRCS of ten kinds of building materials, and it fits the measurement results based on BRDF model to obtain the optimal fitting results, and then the scattering distribution of the target in the whole space is obtained and based on the fitting results, the lidar equation based on the reflectivity is modified, and analyzes LRCS of four typical shape targets such as plane, cone, cylinder and sphere; Research results show that, the metal materials are better in the direction of the laser reflection than the non-metallic material, and the larger the roughness of the material is, the stronger the scattering ability is; the improved reflectivity based lidar equation can reduce the average error of the echo power from 50.87% to 5.06%; LRCS has a great relationship with the incidence angle of each point on the target, and the smaller incident angle is, the larger the target LRCS is;Finally, it extends lidar equation based on the theory of turbulence, and it carries on the echo simulation experiments of the laser imaging radar on the plane target based on the fitting unit-area LRCS in the turbulent and non-turbulent situation, respectively, at the same time, according to the echo image obtained by the laser imaging radar, the actual atmospheric refractive index structure constant is obtained, on which it is based, the echo distribution of the plane target at different distances is studied. Research results show that, for a given target, in the non-turbulent situation, the farther the distance of the target is, the more uniform the echo distribution is, and for the same transmitting power of uniform plane beam and Gaussian beam, under the same conditions, echo power for Gaussian beam is higher; targets in a given distance, the greater the turbulence intensity is, the more serious the echo intensity scintillation is, the more serious distortion of the echo power distribution is; calculated from the experimental data, under the condition of temperature 10.7℃and altitude 60 m, the atmospheric turbulence refractive index structure constant is 3.32×10^-16 m^-2/3, and for the atmospheric turbulence intensity based on the experiment, the farther the distance of the target is, the greater the normalized mean square error of the relative intensity of the echo is, the more serious the intensity scintillation is, and the more serious distortion of the echo power distribution is.