Sharpening-demosaicking method for removal of image blurs caused by an optical low-pass filter

The optical low-pass filter used for a digital camera is formed by combining two types of doubly refractive crystal device. Since the filter cannot sharply cut off high frequency components and it reduces frequency components under the Nyquist frequency, images projected on the imaging surface are blurred. This paper presents a demosaicking method that simultaneously removes image blurs caused by the optical low-pass filter. Our sharpening-demosaicking method employs the Landweber-type iterative algorithm. Since the Bayer´s RGB color filter array is not necessarily proper for our method, we study another better color filter array, the WRB filter array where the W-filtering means that all the visible light passes through it. Our sharpening-demosaicking approach is formulated as the least square problem, but it has multiple solutions. To avoid the ambiguity, we introduce the frequency-band limitation corresponding to the mosaicking pattern of color filters, into the iterative algorithm.