Patent ID: 7936488

Claim:
An image reading apparatus comprising: a light source which sequentially emits lights having a plurality of colors with a plurality of wavelengths to an original; a lens which converges lights reflected from the original; a light receiver including a plurality of pixels, each of which receives lights converged by the lens and performs photoelectric conversion to obtain analog signals for respective colors; an analog-to-digital converter which analog-to-digital converts the analog signals obtained by the light receiver to obtain digital photoelectric conversion outputs, respectively; a correcting portion which corrects the digital photoelectric conversion outputs; a synchronizing circuit which synchronizes the corrected digital photoelectric conversion outputs from a same pixel with each color and outputs output signals for entire pixels; a color determining portion which receives the output signals from the synchronizing circuit, determines whether the output signals for respective colors from the same pixel are within predetermined ranges, respectively, and outputs, as dropout data, pixel position information of the pixel, the outputs signals from which are within the predetermined ranges, respectively; an image monochromating circuit which receives the output signals from the synchronizing circuit, multiplies the output signals by constant data defined for each color, respectively and adds the multiplied output signals from the same pixel to outputs the addition result as monochrome data; a data substituting portion which receives the monochrome data, substitutes the monochrome data corresponding to the pixel position information from the color determining portion with a level at which the pixel is determined as a white level in a binarizing process, and outputs a signal; and an output portion which binarizes the signal output from the data substituting portion and outputs the binarized signal.