Research On Deep Depth-of-Field Imaging And Tracking Of Moving Targets Based On Light Scattering

When incident light transmits through milk,ground glass and tissues or reflects from white paint,the multiple scattering effect of scattering medium makes the traditional optical imaging system not able for targets detection.To solve this problem,methods such as adaptive optics,wavefront modulation,image reconstruction and speckle correlation have been proposed to detect the targets located behind the scattering medium.However,all these methods devote to detect static targets located on a certain plane,and there is little research on imaging of targets on different object planes and tracking of dynamic targets located behind scattering medium.Accordingly,in this paper we make a study of this subject,and the content mainly involves origins and characters of speckle,depth of field extending of the speckle correlation imaging system,and moving targets tracking.Since the concept of speckle is employed throughout the thesis,the concept and the cause of speckle are introduced firstly in order to have a better understanding of the speckle.The speckle’s correlation function in horizontal and depth are derived in detail and the correlation curves are plotted,then the speckle size in horizontal and depth are obtained.On this basis,we discuss the angular correlation function of speckles which corresponds to the different sets of multiple scattering trajectories,and then the optical memory effect of the scattering medium is raised.Secondly,speckle correlation imaging theory is proposed based on the optical memory effect,and numerical simulations as well as experiments are constructed to prove the imaging theory.Real-time and non-invasive imaging through scattering medium is realized via speckle correlation imaging theory.Because of the longitudinal memory effect,depth of field of the speckle correlation system is limited.Relying on the linear properties of the speckle correlation imaging system,we use the deconvolution method for extending the depth of the field via measuring point spread function of the imaging system.At last,a scattering imaging system with deep depth-of-field is realized.Finally,a new method for tracking of moving targets through scattering medium is proposed.Tracking of the target moving on measurement plane parallel to the scattering surface is realized via cross correlation operation,while tracking of the target moving in the direction of the optical axis is realized by calculating the magnification of the imaging system.Thereafter,numerical simulations as well as experiments are conducted to prove the moving targets tracking method.The experiment results verify the high precision of our moving targets tracking method.Depth of field of speckle correlation imaging system is extended and tracking of moving targets that locate behind scattering medium is realized.All these work show potential possibility to extend the applications of scattering imaging further.