Research On Beam Array Deflection Technology Based On Risley-prisms-array Steering System

Risley prisms steering system consists of two consecutive wedge prisms which can steer a light beam to any point in a cone with different coaxial rotating combinations of two prisms based on refraction principle.Risley prism laser beam steering systems have the advantages of compact structure,high scan precision and speed,large field of view(FOV)and good dynamic performance.Risley prisms system can realize higher power,high beam quality,flexible beam control and structurally-expandable beam output,which provides a promising new method for large-angle beam or imaging boresight pointing adjustments.This dissertation focuses on the analysis and research of Risley-prisms-array-based beam steering system.To establish a more complete theoretical system,explore ways to effectively improve the system performance,and lay the theoretical and experimental basis for the engineering application of such systems.In this thesis,by using the non-paraxial ray tracing method,we obtained that prisms with 21-12 configuration can achieve a large deflection angle without blind coverage based on the relationship among the deflection angle of the light beam and the refractive index and the apex angle of the different types of single-aperture Risley prisms.Based on the first-order paraxial approximation vector synthesis method,the nonlinear analytical formula of the beam pointing control accuracy and the definite limit criteria were deduced.The mathematical model of a hexagonal-distributed 7-laser beam array based on rotational Risley-prisms-array was established.then the propagation of the Risley-prisms-array-based beam in free space in the presence or absence of deflection error is derived based on the Huygens-Fresnel principle,and the propagation of the Risley-prisms-array-based beam in turbulent atmosphere in the presence or absence of deflection error is derived based on the extended Huygens-Fresnel principle.Based on the theory of diffractive optical beam transmission and the temporal and spatial distribution of atmospheric turbulence,the related numerical simulation research platform of light source module,Risley-prisms-array module,atmospheric turbulence module,beam transmission module and performance evaluation module are established.The effect of Risley-prisms-array steering system on beam in near-field spot and farfield transmission efficiency is analyzed.Focusing on the investigation of changes in far-field beam quality and energy concentration by effects of beam compression,fill factors,aperture sizes,transmission distances and turbulence intensity.According to the application requirements,the deviation angles,the prism aperture and the propagation distance are reasonably selected by numerical calculation to reduce the influence of the deflected beam deformation and atmospheric turbulence.Considering that the deflection error will occur during the actual assembly and operation processing,the far-field intensity distribution characteristics of the deflected beam array with different deflection error are analyzed in the presence or absence of turbulence.Power in the diffraction-limited bucket is chosen to evaluate beam quality.Finally,a double aperture of Risley-prisms-based beam steering system is established,the far-field spot position of the non-deflected beam array is calibrated,and then the far-field interference pattern of the beam array under 29 different deflection angles is measured.The feasibility and effectiveness of the Risley-prisms-array steering system for beam array deflection are verified.