Landweber-type iterative demosaicing for a single solid state color image sensor

Abstract

This paper presents a Landweber-type iterative demosaicking method for a single solid state color image sensor using three primary color filters of the Bayeris pattern. The iterative demosaicking method can restore a high-resolution color image much better than the existing non-iterative demosaicking methods using switchover-type interpolation filters. This paper, extending the idea of our previously presented image acquisition scheme using an imperfect image sensor with defect pixels, forms the iterative demosaicking method. Our previous scheme prepares a defect-pixel map in advance, and then takes a defocused image with an imperfect image sensor. Utilizing the defect-pixel map and the information that each pixel shares with its adjacent pixels, it recovers defect pixels and simultaneously sharpens the blurred image. As the recovery technique, we have formed the Landweber-type iterative algorithm. Taking it into account that decimated color pixels caused by the color filters correspond to defect pixels in the above recovery problem, we adapt our previous iterative recovery method to the demosaicking problem. Furthermore, to restrain the occurrence of false color caused by the demosaicking and simultaneously to preserve original hue variations as thoroughly as possible, this paper forms a hybrid demosaicking method that first applies the Landweber-type iterative algorithm to the interpolation of the green color component and then performs the interpolation of the red and the blue components with some existing hue- or chrominance-preserving-type method. Experiments using test images and color images really taken with a high-resolution digital color camera demonstrate that our hybrid demosaicking method reproduces a sharpened high-resolution color image without producing noticeable artifacts of false color.