Research On Spatial Correlations And Imaging Techniques Of Random Optical Field

When a light wave travels through disordered media,the amplitude and phase of the outgoing wave exhibits random distributions due to the multiple scatterings induced by the spatially varying refractive indices.This greatly limits various applications utilizing light as energy or information carriers.With the continuously advancing skills of optical field manipulation,it’s now possible to reconstruct the incident wave information from scattered light or even to make use of the degrees of freedom provided by multiple scattering effects.In such a contemporary context,we aim to analyze the measurable wave information hidden in the scattered fields and explore several corresponding imaging techniques.Our treatments fell into two schemes: methods that rely on prior acquisition of medium information and methods that do not require such information.For the first kind,the main concern was the theory of the optical transmission matrix of disordered media which models the input-output relation as a black box.The measurement techniques of such matrices were achieved,and random matrix theory was invoked as a tool to analyze the intrinsic information and various contributing factors in the matrices.In particular,we focused on the utilization or suppression of the field-field correlations and realized field control means such as focusing and imaging.Besides,we were also able to further improve such controls through purposefully engineering the time reversal process.For the second scheme,we thoroughly studied the single-shot speckle autocorrelation and deconvolution techniques for imaging through scattering media.These two techniques were made possible by combining speckle information with linear system response theory.To achieve imaging within an extended depth of field,the axial variation of the point spread function of the system was derived,making the author successfully reconstruct the object at varying positions through a point spread function measured at only one position.As such speckle-based methods are implicitly subject to constraints governed by the optical memory effect,the thesis concludes with a study of the correlations of speckle patterns which characterize the memory effect.The main exploration was to find out the evolution of the speckle correlations with the varying incident parameters such as the topological charge,the polarization state or the order of the eigen channel.Such dependences were quantitatively demonstrated using experimental results.