IMAGE RESTORATION OF A SINGLE-CHIP IMAGE SENSOR

A signal processing method for estimating luminance is provided, for use with matrix patterned image sensors where elected sensor pixels (G), preferably green pixels, from which luminance-representative signals are taken, only occupy alternate horizontal and vertical positions in the matrix pattern. The method is designed for detecting luminance contour edges and/or stripes in an image so as to enable images obtained form the sensor to be enhanced. Each pixel site (Hc) which is at the centre of both a row and a column of five pixels, and which is not the site of an elected (green) pixel, is identified and, for each such identified site (Hc), the signals output from the immediately adjacent four pixels (Gn,Ge,Gs,Gw) in said row and column are processed to establish both signal amplitude and pixel position. A luminance value for the pixel at the identified site (Hc) is evaluated from the amplitude values (G2,G3) of the median pair of said signal amplitudes in accordance with an algorithm where decision taking is based upon the location of the pixels from which the two signals (G1,G2) of highest amplitude emanate. When the two signals (G1, G2) of highest amplitude emanate from pixels in the same row or column, a further signal processing step is undertaken to identify, in said row and column, the signal outputs from the two respective next adjacent pixels (H1,H4) to the pixels having the highest and lowest signal amplitudes (G1,G4), and the signal output from the pixel at the identified site (Hc), to enable an amplitude comparison to be made according to the result of which one of said median pair (G2,G3) is selected. Signal processing methods for use with colour, monochrome and mixed colour/monochrome image sensors are claimed, as well as a single-chip camera, and also a video camera system, in which the claimed signal processing methods are implemented. the two signals (G1,G2) of highest amplitude emanate from pixels in the same row or column, a