| When light is transmitted in the inhomogeneous medium such as ocean,atmospheric turbulence,and biological tissues,light will be scattered and cannot travel in a straight line due to particles in the medium.And the information carried by the light will also be lost after multiple scattering and diffusion.The adverse effects of scattered light on imaging quality can be overcome by wave-front shaping technique,and combined with the optical memory effect,the real-time scattering imaging can be realized.Especially the wave-front shaping technique based on iterative search method have received widespread attention due to their simple optical paths,easy implementation,and strong anti-noise interference ability.However,the speed of iterative search method to restore the reference object image limits the overall imaging speed and hinders the development of technique.According to the above background,in order to solve the problem of the slow speed of common iterative search algorithms,the theoretical and experimental study on improving the speed and quality of iterative search algorithms has been investigated.The main content and research results are as follows:(1)An iterative search of wave-front modulation phase using hybrid particle swarm and genetic algorithm is proposed,and a model of wave-front modulation phase for scattering imaging is established based on the algorithm.In terms of imaging speed and imaging quality,the performance of the algorithm is compared with the genetic algorithm and particle swarm optimization algorithm which are commonly used in wave-front shaping technique.The results show that the hybrid algorithm performs better in imaging speed and image quality than the other two algorithms.Then several common image quality evaluation indexes are used as evaluation functions,the influence of the different evaluation functions on the scattering imaging effect is discussed based on the algorithm(2)A real-time iterative search and feedback experimental device for scattering imaging is built based on the LAB VIEW program.In the experiment,the performance of genetic algorithm,particle swarm optimization algorithm and the hybrid algorithm in imaging speed and quality were compared and analyzed,and the theoretical model is verified.The experimental results show that the saturation value obtained by the hybrid algorithm after convergence is higher than that of other algorithms with any population size.And compared with genetic algorithm,the hybrid algorithm can be used to reduce the running time by about 15%.Based on the hybrid algorithm,the influence of the image quality evaluation indicators on the restoration effect of the target image in multiple sets of scattering experiments is studied.It can be found that compared to PSNR and PCC,SSIM evaluates imaging quality from multiple dimensions such as structure and contrast which is more conducive to analyzing and describing image details during the imaging process.(3)The effect of scattering imaging at different transmission distances are simulated and analyzed.In the experiment,the influence of different transmission distances behind the scattering medium on the imaging effect under the same modulation strength is studied.It can be found that the average scattering imaging effect decreases with the increase of the scattered light transmission distance,which has a reference significance for future research on long-range scattering imaging.In this thesis,based on the hybrid particle swarm and genetic algorithm and evaluation function,the research on improving the speed and quality of scattering imaging is carried out.It provides reference for improving the efficiency of scattering imaging and long-distance scattering imaging,and has guiding significance in practical applications such as biomedical imaging and laser treatment. |
