Image Restoration in Horizontal Surveillance by Telescope

Abstract. A new method for restoring images degraded by atmospheric turbulence where the resulting point spread function varies across the field of view is discussed. Such cases occur in horizontal imaging by telescope close to the ground, especially during daytime when convective turbulence is worst. Each image frame of a captured movie sequence is exposed for a time short enough to freeze the effects of the turbulence, resulting in a random wobble and blurring of the image that is position and time dependent. Registration of each frame to a reference image is achieved either by a moving region-of-interest correlation or by a gradient-based optical flow method. In this paper, we discuss a new method, replacing correlation by a moving region-of-interest Wiener filter that came from experiments visualising turbulence in jet plumes. The resulting shift information is used to dewarp each frame of the sequence before averaging to provide a result corrected for motion-blur. Further deblurring is carried out by a variety of deconvolution techniques. The shift or blur information can also be used to visualise the intervening atmospheric turbulence.