US Patent 7190384 Image forming apparatus and density unevenness preventing method

A system controller of a color thermal printer obtains a density profile of an image with respect to a feeding direction of a color thermal recording paper based on density of a test print measured by a CCD line sensor, and then extracts a density unevenness component, which fluctuates periodically, from the density profile. The system controller relates the density unevenness component in one period to a rotating position of a feed motor so as to create a period profile of a driving pulse to offset the unevenness component. When recording the image, the driving pulse is given to the feed motor based on the period profile, so that the drive of the feed motor is controlled.