Research On Image Enhancement Technology Based On Fourier Ptychography

With its rich spatial information and intuitive presentation,image information has been widely used in many fields,such as meteorology,resources,military,national defense and so on.However,the existence of diffraction blur leads to the problem of image quality degradation in optical imaging system,and the image contrast and resolution are difficult to meet the increasing imaging requirements.Increasing the aperture of the imaging system can effectively improve the imaging quality of the optical imaging system,but the current large aperture optical imaging system has high manufacturing cost and difficult development,which limits the further improvement of image quality to a certain extent.Therefore,how to effectively improve the equivalent aperture of optical imaging system and solve the problem of image degradation caused by diffraction blur is of great significance to the further development of optical imaging system,especially long-distance imaging system in the future.In view of the above problems,this paper studies the image enhancement technology based on Fourier ptychography,and studies the image enhancement effect of this technology from three aspects: model establishment,algorithm simulation and experimental verification.The specific work contents are as follows:Aiming at the problem of image quality degradation,starting from the imaging mechanism of optical imaging system,this paper analyzes the influence of diffraction blur on the imaging quality of optical imaging system,and establishes the diffraction blur model of long-distance imaging system.On this basis,the imaging process of the traditional macro Fourier ptychography imaging system is modeled,and three propagation processes of the light field are analyzed: I.the light field propagation process from the far-field object surface to the imaging lens,II.The light field characteristics of the lens at different scanning positions,and III.the light field propagation process from the imaging lens to the detector.Finally,in order to simulate the actual imaging process of equivalent far-field,it is proposed to realize far-field macro Fourier ptychography imaging at limited distance by using convergent spherical wave illumination,and the imaging model is optimized.In order to improve the equivalent aperture of the imaging system,a macro Fourier ptychography imaging technology based on matrix scanning is proposed in this paper.This technology obtains a series of conventional images under the aperture of the original imaging lens by spectrum scanning on the Fourier surface of the imaging system.The reconstruction algorithm is used to iterate the spectrum information of each sub aperture,synthesize a spectrum bandwidth equivalent to the large aperture imaging system,expand the equivalent aperture of the imaging system,and realize the image enhancement of the long-distance imaging system.Then,some key parameters of Fourier ptychography reconstruction algorithm are simulated by MATLAB,and the influence laws of synthetic spectrum size and adjacent aperture overlap rate on image enhancement effect are analyzed,which provides a basis for the optimization of the algorithm.Based on the above theoretical research and simulation analysis,this paper designs and develops a macro Fourier ptychography imaging system based on matrix scanning.The system includes laser active lighting module,scanning imaging module and software control module.Based on the completion of the system,the verification experiment of image quality improvement of long-distance image is carried out.Compared with the unprocessed image,it is proved that the system can improve the imaging contrast PSNR of long-distance target by2.15 times and the resolution by 30%,which effectively enhances the visual effect of macro imaging system.