| The optical system with large depth of field can not only obtain a broader object space, but also inhibit some of the defocus aberrations. The traditional methods of extending the depth of field were always based on narrowing aperture, which would reduce the image resolution. While the wavefront coding technology combine the optical encoding and digital decoding can extend depth of field without affecting other imaging performance. The research focused on two key technical issues of wavefront coding in application, including the high-precision manufacturing and assembly of optical encoding component and the image restoration algorithms. The main work of the paper is as follows,1. Through analyzing the characteristic of classical restoration algorithm, an improved Wiener filtering algorithm was proposed, which improved the image denoising and boundary ringing compared with the classical algorithms. The wavelet subband adaptive threshold algorithm was used to reduce image noise. The different threshold value was analyzed to deal with wavelet coefficient.2. The low frequency form error and intermediate frequency waviness in fabricating the cubic phase mask were also analyzed using Zernike polynomial fitting and user-defined surface type. The influence of typical sinusoidal shape error on image restoration in a typical Cooke triplet wavefront coding system was obtained finally.3. The impact of assembly errors of cubic phase mask on point spread function and modulation transfer function were theoretically deduced by simulating in coordinate deflection. The tolerance of assembly error could be defined by the above analysis. The effect of assembly error on image restoration was also analyzed by adding the cubic phase mask to a Cooke triplet optical system. By adjusting the orientation of ideal point spread function, the PSF transformation caused by angular error around Z-axis could be compensated, which increased the freedom of assembly of optical system. |
PDF Full Text Request