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Extended fisheye lens model for practical geometric correction and image enhancement.

An extended fisheye lens model is presented to control the size ratio between the distorted and virtually undistorted images based on orthographic projection. The optimum size ratio is derived to correct the barrel distortion of a fisheye lens so that the maximum amount of the peripheral region is reconstructed with the minimum visual distortion. The geometric correction generates an aliasing artifact in the central region and a jagging artifact in the peripheral region. Based on the proposed lens model, a novel image enhancement algorithm is also presented to remove the aliasing and jagging artifacts in the geometrically corrected image. Experimental results demonstrate that the proposed enhancement method outperforms existing methods in the sense of objective and subjective measures.