Short-exposure Image Reconstruction with The Power Spectrum Extended (PSE) Method

Abstract

We analyze, in the framework of high angular resolution imaging, a novel image reconstruction method denoted as PSE (which stands for power spectrum extended). It works in the Fourier space, combining the information from both the average power spectrum of the images and a phase estimation from an ad-hoc shift-and-add process. PSE allows to perform image reconstruction up to the diffraction limit of the telescope from a series of short-exposure frames, with a refined lucky-imaging selection process. The method is well adapted to partially corrected adaptive-optics images, in particular in case of low Strehl corrections, and/or small diameter telescopes. In this paper we analyze the PSE technique by means of Monte-Carlo simulations and compare it with the ISFAS lucky-imaging method. Comparative performances were investigated using three metrics: Strehl ratio for reconstructed point-like sources, intensity ratio for binary stars, and least-square distance between images for a simulated artificial satellite. We found that PSE provides an improvement of a factor ∼2 over ISFAS on the Strehl ratio in the case of faint point sources. It seems also to give better images reconstruction on some kinds of extended objects (planets or binary stars with small magnitude difference). PSE has also the advantage to be very fast and well adapted to real-time image reconstruction.