Three-dimensional High-Resolution Imaging With Laser Scanning Using Fiber Phased Array

The laser phased array radar uses the electro-optic characteristics of optical materials to form an optical phased array that can realize beam scanning without mechanical,and has the characteristics of flexible scanning,precise pointing,and automatic programming control.The optical fiber phased array coherent combined beam has high power and good quality,and it has broad application prospects in the long-distance laser three-dimensional detection and imaging of the target.The 3D imaging quality of fiber phased array scanning is limited by the parameters of the fiber array at the transmitting end and the size of the array,and the 3D imaging accuracy is closely related to the target ranging method and the beam modulation bandwidth.Based on the optical fiber phased array laser scanning system,this paper carries out the research of the 3D imaging algorithm under the low-pixel detector,and uses the software algorithm to improve the system's 3D detection imaging resolution.This thesis uses the far-field optical field transmission theory of the optical fiber phased array and the physical model of the optical fiber phased array beam scanning under the phase control of lithium niobate to simulate and analyze the optical field distribution and scanning characteristics of the optical fiber phased array.The combined beam quality after phase optimization and compensation based on the existing optical fiber array system is close to the theoretical limit,and the spatial resolution of the scanning system is analyzed based on the beam intensity distribution and beam angular width parameters of the coherent combined array.It is determined that the 8×8 array sub-beams are scanned in blocks to form a 64×64 spatially directed beam for three-dimensional imaging.Aiming at the 3D imaging system composed of the frequency modulation continuous wave ranging method and the 8×8 lowpixel detection array,the image degradation model is used to carry out the 3D imaging simulation study of the array beam scanning,and the resolution of the system detection image under the intensity and distance dimensions is analyzed.This thesis proposes a laser scanning three-dimensional high-resolution imaging algorithm based on a fiber phased array,improves the processing method of the difference frequency signal in the FM continuous wave multi-target ranging process,and demodulates the target according to the judgment value of the(signal frequency domain secondary peak value to the main peak value)More distance information.Under the constraint condition that the mean square error of the reconstruction result and the image interpolation result is the smallest,the distance information reconstructed by the priori information arrangement algorithm of topological structure in the low-resolution range image is used.The detailed information of the target reconstruction result is closer to the original image of the target distance.The number of pixels of the image reconstructed by the imaging algorithm is,and the image evaluation index is significantly improved.Finally,we deeply study the influence of Wiener filter constant on the reconstruction quality of high-resolution 3D imaging algorithm,and the result shows that the evaluation index of target algorithm reconstruction result is the best at that time.