The Research Of Image Restoration Based On Phase Diversity Method

Due to atmosphere turbulence and optical system aberrations, large scale ground based electro-optical telescope can suffer from wavefront distortions, detracting from their intended diffraction-limited performance goals, even with large scale aperture. So designing a telescope which can overcome wave-front distortions is one of the most important tasks right now.It is well known that Phase Diversity (PD) method is competent for overcoming wavefront distortions. PD method can estimate both the wavefront phase and object, by exploiting the simultaneous collection of two or more short exposure images in focused and defocused channels, with known defocus phase as the prior information. It can sense discontinued wavefront and high-order aberrations, also work with extended scenes. It's a key method of the AO image restoration technology.In this paper, the error of PD theory is analyzed with the on going experiments. An auto-registration method is proposed by using the tip/tilt terms of Zernike polynomial. A reflective PD test-bed is designed. To verify the ability of image restoration and phase estimation of PD method, two experiments which are high-resolution imaging and phase estimation comparison by one camera are established. In order to get both of the focused and defocused images, we shift the high accurate translation stage at a certain distance. The Shack-Hartmann wave-front sensor is also used to observe the wave-front phase in real-time of the imaging system. Finally, the difference between the wave-front phase observed by Shack-Hartmann and the one estimated by PD method is discussed. Experiment results indicate that the estimated wave-front phase is highly according with the one detected by Shack-Hartmann and the resolution of the restored image can increase 12% compared with the origin image formed by focus plane. Moreover, PDS experiment with two cameras is also realized. Experiment results indicate that multi-frame and multi-channel method is better than former. So the PD method can be used as a good means to restore the degradative images in the large aperture electro-optical telescope.