Color printer using circulation period to control registration of images

Claim 1

A color printer, for use with color image data generating means which sequentially generates color image data corresponding to different colors of a multi-color image, for printing the multi-color image on a recording medium, said color printer comprising: a photo-sensitive body adapted to circulate in response to a print request signal from the color image data generating means; electrostatic latent image forming means for forming on said circulating photo-sensitive body an electrostatic latent image of color image data received from the color image data generating means and corresponding to a respective color of the multi-color image; developing means for developing the electrostatic latent image formed on said photo-sensitive body to form thereon a one-color toner image of the received color image data; conveying means for circulating a recording medium in synchronism with the circulating photo-sensitive body for transfer to the recording medium of the one-color toner image on said circulating photo-sensitive body; and image data request signal generation means for sequentially generating and applying image data request signals to the image data generating means, to request generation of color image data corresponding to a respective color of the multi-color image, said image data request signal generation means including: (a) image data request reference signal generating means responsive to the print request signal for generating an image data request reference signal; (b) clock means for generating a clock signal; (c) passage detecting means, responsive to each passage of a particular portion of said conveying means through a predetermined position during circulation of the recording medium, for generating passage detection signals; (d) first measuring means, response to the clock signal and to each passage detection signal, for measuring each respective circulation period of the recording medium on said conveying means between successive passage detection signals and for providing an output signal indicative thereof; (e) second measuring means, responsive to the clock signal and each output signal from said first measuring means, for controlling a synchronization interval for each respective image data request signal, each synchronization interval having a duration determined by the respective circulation period measured by said first measuring means, said second measuring means being responsive to termination of the synchronization interval for initiating a subsequent synchronization interval; and (f) means for generating a first image data request signal in response to the image data request reference signal and for generating a subsequent image data request signal in response to termination of the synchronization interval, so that the application to the image data generating means of each image data request signal subsequent to said first image data request signal occurs at a time synchronizing the circulation of said photo-sensitive body having the developed electrostatic image thereon with the circulation of the recording medium on said conveying means to cause sequential transfer of color toner images to the recording medium in registry to form a multi-color image on the recording medium.