US Patent 7852379 Image forming apparatus, image forming method, and computer program product

An image forming apparatus causes an illuminating unit and an imaging unit to equally split a predetermined exposure time into a plurality of split exposure times, and acquire an image with illumination and an image without illumination in each of the split exposure time. A luminance difference image for a particular split exposure time is calculated by subtracting the image without illumination from the image with illumination of the exposure time. The luminance difference images of all the split exposure times are integrated.