Fast sampling based image reconstruction algorithm for sheared-beam imaging

Sheared-beam imaging (SBI) is an unconventional ground-based optical imaging technique. It breaksthrough the traditional optical imaging concept by using three coherent laser beams, which are laterallydisplaced at the transmit plane, to illuminate the target, reconstructing the target image from echo signals.However, the echo data sampling of the imaging system is still not fast enough to reconstruct the highresolution and clear image of the target when imaging the target that is at rapidly changing position andattitude. In order to solve this problem, in this work an image reconstruction method is proposed based on five-beam fast sampling. An emitted beam array arranged in the cross shape with a central symmetrical structure isproposed, and the encoding and decoding method of the imaging system are changed. With a single exposure,the echo signals carry more spectrum information of the target, and the number of reconstructed images can beincreased from 1 to 8, which quickly suppresses the speckle effect of the reconstructed image. Firstly, theprinciple of the imaging technique based on fast sampling is presented. Then, an image reconstruction algorithmbased on fast sampling is studied. Eight groups of phase differences and amplitude information of the target canbe extracted from echo signals. The wavefront phases are solved by the least-squares method, and wavefrontamplitude can be obtained by the algebraic operation of speckle amplitude. The target image is reconstructedby the inverse Fourier transform. The simulation results show that comparing with the traditional three-beamimage reconstruction method, the sampling times of echo data needed to obtain the same quality image arereduced from 20 to 5, which greatly reduces the sampling times of echo data and improves the sampling rate of echo data