Color image reacting apparatus having a non-uniformity correction ROM with sections corresponding to red, green, and blue color separation filters

Claim 1

A color image reading apparatus, comprising a light source for illuminating a document bearing an image to be read, light directing means including at least one mirror and an optical objective, said light directing means being effective for directing light reflected by a strip of said image thus illuminated onto a series of cells of a charge-coupled device (CCD) for reading the strip by generating a series of response signals in response to a series of image pixels along the strip, an A/D converter operative on said series of response signals to provide corresponding series of digital signals, storing means for temporarily storing a series of digital signals obtained from said converter during a preliminary reading of a calibrated background sample strip, a read-only memory means having a plurality of memory cells corresponding to the series of cells of the CCD, the memory cells of said read-only memory means being sequentially addressed by both the series of digital signals obtained from said converter during the reading of the strip of said image and the series of digital signals stored in said storing means for supplying from each memory cell a digital output signal for a corresponding one of the image pixels along the strip of the image, the digital output signal being compensated for compound variations in the illuminating action of said light source and transfer functions of said at least one mirror, said objective and said CCD, said apparatus also comprising a number of filters selectable for being interposed between said image and said CCD, control means operable for selecting said filters in sequence so as to cause said CCD to generate in sequence a series of response signals associated with each one of said filters during said preliminary reading and for storing a corresponding series of digital signals obtained from said converter in said storing means, said read-only memory means comprising a number of sections corresponding to said number of filters, each section of the read-only memory means having a plurality of memory cells corresponding to the series of cells of the CCD, the cells of each section of the read-only memory means being sequentially addressed by both a series of digital signals obtained from said converter during a corresponding reading of the strip of said image through the associated filter and the corresponding series of digital signals stored in said storing means, the memory cells of the various sections of said read-only memory means so addressed supplying digital output signals representing corresponding ones of the image pixels along the strip of the image, the digital output signals being differently compensated according to the corresponding ones of the filters, and including half-tone coding means having a number of sections corresponding to the sections of said read-only memory means, each section of said coding means receiving the digital output signals supplied by the corresponding section of said read-only memory means for coding the digital output signals as patterns of black and white pixels indicative of the levels of the digital output signals.