29 December 2000 Enhancement of out-of-focus images using fusion-based PSF estimation and restoration
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In this paper, we propose an enhancement algorithm of out-of- focused images using fusion-based Point-spread-function (PSF) estimation and restoration. The proposed algorithm can make in-focused image by using only digital image processing techniques, and it requires neither infrared light/ultrasound nor focusing lens assembly operated by electrically powered movement of focusing lens. In order to increase accuracy in estimating the PSF of the defocus image, the proposed algorithm finds true and linear edges by using Canny edge detector, which is optimal edge detector and has good localization, estimates the step response across the edge for each pixel, computes the one-dimensional step response by averaging the step responses, estimates the two-dimensional PSF from the averaged step response, and then provides in- focused image by image restoration filter based on the estimated PSF. Finally, we execute fusion process, which can enhance the quality of the fused image by fusing restored images. There is a limit of the amount of out-of-focus, which can be recovered by the proposed algorithm. Moreover, the proposed algorithm is operating under assumption that an input image contains at least one piece-wise linear boundary between an object and background. In spite of above-mentioned limitations, the proposed algorithm can make acceptable quality of focused image by using only digital image processing.
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Joonshik Yoon, Joonshik Yoon, Jeong-Ho Shin, Jeong-Ho Shin, Joon-Ki Paik, Joon-Ki Paik, } "Enhancement of out-of-focus images using fusion-based PSF estimation and restoration", Proc. SPIE 4310, Visual Communications and Image Processing 2001, (29 December 2000); doi: 10.1117/12.411863; https://doi.org/10.1117/12.411863

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