Theory Research And Application Of The Decoding Algorithms Based On Wavefront Coding Imaging System

Wavefront coding hybrid optical-digital system is a two-step imaging system. A cubic phase mask is positioned on the pupil plane, in the image plane a defocus-insensitive but blurred intermediate image is acquired, the final sharp image can be given by using the digital image restoration algorithms. This technology can give large depth of field and improve the imaging quality. At present, the deblurring algorithms restrict the development of the technology. The restored image has serious boundary effect, loses more details and does not look natural.Firstly, we consider the process of the image convolution, and discuss the theory of the optical imaging, then take the process to the solution procedure of the linear equations in mathematics, further we analyze the building method of the linear blurring matrix on different boundary conditions, by using the Kronecker production, finally a matrix equations can be given which stands for the process of the image convolution. Then the Krylov subspace method is discussed and used to solve the matrix equations. Two kinds of domain iterative image deconvolution space algorithms based on the Krylov subspace are given such as generalized minimal residual method (GMRES), and transpose-free quasi-minimal residual algorithm. Both of them have excellent deconvolution effect, the first method constructs complete orthogonal basis and can give exact approximate solution; the second method needs less storage and less computation time than the GMRES method, which is a useful supplement of the first one. Then we combine the Tikhonov reguralization and anti-reflective-boundary conditons, and a space domain iterative algorithm with excellent deconvolution and noise suppression effect is given. Finally by using the three channel principle the space domain iterative color image algorithm is acquired, the experiment shows that the new algorithm can give smooth and natural restored image.Secondly, a novel image restoration algorithm based on boundary pre-processing in the space domain and fast computing in the frequency domain is proposed for the first time. By using the theory of the boundary conditions, we can get the image which is enlarged by the different boundary hypothesis, then the frequency filtering is used to find the restored result. The frequency property of the enlarged image and the effect to the boundary of the restored image are analyzed. Effectiveness and speediness of the proposed method was demonstrated by experiment results, which can give excellent deconvolution and noise suppression restored image and reduce the boundary ringing effect under the reflective and antireflective boundary condtions.Thirdly, the 10X and 40X wavefront coding microscopy based on the classical domestic micro objective are designed, which give excellent results by using proposed two algorithms. Although the optical performance of the classical domestic micro objective is poor, and the wavefront coding system could not give exactly similar PSF and MTF, but our proposed image restoration algorithms can still give satisfactory results.Finaly, we proposed to underwater imaging by using the wavefront coding system for the first time. The water's aberration and scattering can be modulated by the large aberrations introduced by the cubic phase mask, which can be eliminated by using the image restoration algorithm. The experiment showes that the contrast enhanced and more details restored image can be given. It is a validity and feasibility method.