The Application Of Sparse Model In Wavefront Coded Imaging System

Minimize relative aperture is a traditional method to extend the depth of field(DOF)of optical system,but it causes a decrease of optical power and resolution at the image plane.How to extend the depth of field of optical system but avoiding the deficiencies mentioned above is still a hot research topic in recent years.Wavefront coding is a new method to extend the depth of field,which was raised by Dowski.Unlike traditional method,the wavefront of imaging beam of wavefront coded system is modulated by a specially designed cubic phase mask in the aperture stop,and make optical transfer function of wavefront coded system is insensitive to the defocus.Therefore,with some simple filtering algorithms,we can achieve a large DOF optical system.The size of entrance pupil of wavefront coded system has not been changed,so it has large depth of field with maintaining higher resolution and illuminance at the image plane.This article mainly from two parts to study wavefront coding technology:the optical simulation of wavefront coded system and the post processing of intermediate images.Main works are as follows:First,a wavefront coded system was designed based on Cookie triplet system,the depth of field of this new system was 28 times larger than initial system.The focus invariance of modulation transfer function(MTF)was chosen as merit function in the design.The imaging characteristics of wavefont coded system was analyzed in the paper.Second,Wiener filtering algorithm was selected to restore intermediate images,and the quality of decoded images at different defocus positions was compared.For purposes of theoretical analysis,we compared the relationship between defocus insensitivity and recoverability of intermediate images in the paper.Third,the theoretical theory of sparse model in image processing was studied.The difference between PSFs of wavefront coded system was restored by using sparse model,so the quality of decoded images was improved.