Experimental Research On LRCS Of Partially Coherent Light Rough Surface

The laser scattering characteristic of the target is one of the difficult problems of lidar application because it involves the geometry of the target,rough surface scattering and the complex dielectric properties of the material.In early laser coherent detection,the coherent light degenerates into partially coherent light due to the consideration of atmospheric turbulence.Compared with coherent light,partially coherent light has some advantages in suppressing the influence of intensity scintillation and phase fluctuation brought by turbulence.Particularly in the last decade,the coincidence imaging technology based on pseudothermal light has been paid more attention due to its unique performance.The above factors make the study of target scattering characteristics under partially coherent light get more attention,which has important theoretical significance and application value for laser target detection and new system imaging.In this paper,the laser radar scattering cross section(LRCS),an important parameter of rough surface target characteristics,is studied in depth with the theory of partially coherent light.Paper first introduces the important parameters to describe rough surface and the target features two important parameters of laser radar scattering cross section LRCS and bidirectional reflectance distribution function(BRDF).Adopting the Kirchhoff approximation of rough surface electromagnetic scattering theory,the paper analyzes the influences created by rough surface height fluctuation root mean square and correlation length and material dielectric constant to single and double stand scattering coefficient at typical laser wavelength.The effects of coherent beam length,beam width and rough surface parameters on the backscattering coefficient are simulated and analyzed by using a typical partial coherent beam-Gaussian Sheel beam(GSM)-and the expressions of rough surface scattering coefficient under GSM beam irradiation.This paper systematically carries out the experimental measurement of coherent and partially coherent light scattering characteristics of rough metal surfaces,studying a total of 13 samples,including a primary aluminum plate,nine different mesh sandblasted aluminum plates,a black aluminum oxide plate,and two paint materials with different roughness.Firstly,the roughness parameters of the sample and the overall spectral reflectance of the rough material were measured.And then the partially coherent beams generated by rotating ground-glass,the transverse coherent lengths were measured under different conditions,which provides comprehensive and reliable experimental parameters for the theoretical and experimental comparison of the scattering characteristics of partially coherent light rough surface.Finally,the target laser scattering automatic measurement system was used to measure the scattering coefficients of coherent light and partially coherent light at two wavelengths of 532 nm and 632.8nm.The angular distribution of scattering coefficients of single and double stations at 20° oblique incidence were theoretically and experimentally tested,and the two are in good agreement.This paper not only provides experimental basis for the theory verification of partially coherent rough surface scattering,but also provides theoretical basis for the study of the target partially coherent light scattering characteristics.