Abstract

An adaptive optics (AO) system provides real-time compensation for atmospheric turbulence. However, an AO image is usually of poor contrast because of the nature of the imaging process, meaning that the image contains information coming from both out-of-focus and in-focus planes of the object, which also brings about a loss in quality. In this paper, we present a robust multi-frame adaptive optics image restoration algorithm via maximum likelihood estimation. Our proposed algorithm uses a maximum likelihood method with image regularization as the basic principle, and constructs the joint log likelihood function for multi-frame AO images based on a Poisson distribution model. To begin with, a frame selection method based on image variance is applied to the observed multi-frame AO images to select images with better quality to improve the convergence of a blind deconvolution algorithm. Then, by combining the imaging conditions and the AO system properties, a point spread function estimation model is built. Finally, we develop our iterative solutions for AO image restoration addressing the joint deconvolution issue. We conduct a number of experiments to evaluate the performances of our proposed algorithm. Experimental results show that our algorithm produces accurate AO image restoration results and outperforms the current state-of-the-art blind deconvolution methods.

Highlights

  • Because of the turbulent flow field, an imaging system with adaptive optics (AO) is interfered by heat, thermal radiation, and image transmission

  • Zhang et al proposed a multi-frame iterative blind deconvolution algorithm based on an improved expectation maximization algorithm for AO image restoration (RT-IEM algorithm) [12], which represents a more complex function to minimize

  • We present experimental results on AO images taken by a 1.2 m AO telescope (Yunnan Observatory, Yunnan, China) which uses the Hartmann–Shack wavefront sensor from the Chinese Academy of Sciences at Yunnan Observatory on 3 December 2006

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Summary

Introduction

Because of the turbulent flow field, an imaging system with adaptive optics (AO) is interfered by heat, thermal radiation, and image transmission. Zhang et al proposed a multi-frame iterative blind deconvolution algorithm based on an improved expectation maximization algorithm for AO image restoration (RT-IEM algorithm) [12], which represents a more complex function to minimize. This algorithm contains a cost function for the joint-deconvolution of multi-frame AO images, and it estimates the regularization terms. Our goal in this paper is to propose a new deconvolution scheme based on our frame selection method and the initial PSF estimation approach.

AO Image Degradation Model
Frame Selection Technique Based on Variance
PSF Model
Estimators with Poisson Statistics
Algorithm Implementation for AO Image Restoration
Experimental Results
The Restoration Experiment on Simulated Images
Restoration Experiments on Binary-Star AO Images
Sensitivity Analysis
Conclusions
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