Research On The Imaging Property Of Wavefront Coding Optical System And Its Application In Cell Phone Lens

Extending the depth of field has always being the researching hotspot of optical imagingsystem, for the optical imaging system with larger depth of field not only have more objectinformation, but also can correct or minimize some defocus-related aberration. Wavefrontcoding imaging technique has combined both traditional optical imaging technique and digitalimage processing technique perfectly. Its introduction of phase mask at the position of pupilof optical imaging system make the modulation transfer function and point spread functioninsensitive to the defocus-related aberration. In this way, we can gain the middle blurredimage of each defocus position, then restoring the middle blurred image of each defocusposition to their sharp clear images. Besides ensuring the flux and imaging resolution andextending the depth of field in optical imaging system, wavefront coding imaging techniquealso can inhibit the spherical aberration, chromatic aberration, astigmatism, Ptzvel (field)curvature, and the defocus-related aberration caused by the installation error and temperaturechanges. Owing to WFC with its unique characteristics, the method to extend the depth offield by using wavefront coding(WFC) technique is the researching foreland.This paper is mainly divided into the following four parts:(1) We obtained and analyzed the approximate expression of the peak position of PSF ofwavefront coding system with a CPM deduced, which is a family of the parabolas whosesymmetry axes are the focal plane. The approximate peak position is shown to be accurateexcept for a negligible oscillation along the optical axis. The NASR is proposed to evaluatethe performance of the CPM wavefront coding systems. Besides, it could be applied to theevaluation of the similarity and recoverability of MTF and to the optimization of phase maskparameters；(2) In order to analyze the effect of detector noise on the performance of wavefrontcoding system in the image restoration process, this paper simulates the detector noise byadding Gaussian random noise, uses direct inverse filtering, Wiener filtering andLucy-Richardson filter algorithms to restore the middle blurred image of the wavefrontcoding system at the focus position and the defocus position, then evaluates the restoredimages and shows the changes of performance of recovery filter with noise;(3) Using weights method with different defocus position degradation function toconstructed the weights of PSF. The theoretical idea is to make the quality of all the restored image of the defocus position similar to the real scene as much as possible. Andusing focus position PSF, the mean PSF and constructed weight PSF to restoring themiddle blurred images of wavefront coding system of different phase mask parameters,and evaluating the restored images;(4) Studying the application of wavefront coding imaging technique in the imaging ofcell phone lens. Combining the insensitivity of defocus of optical transfer function and therestoration of system to optimize the phase mask parameters of wavefront coding system. Awavefront coding optical imaging system of cellphone lens has been designed based on thephase mask parameters which are obtained by this method, and restoring the middle blurredimage of the system by using weights method. The experimental result shows that the depthof the field of the system has been extended40times.