Color image processing apparatus which accurately registers multiple color images by counting pulses from a timer reset by a drum index signal

摘要

In a color image processing apparatus according to the invention, a color image signal being photoelectrically obtained by a image reader is separated into red, blue and black color component signals. A laser scanner writes respective latent images corresponding to the color component signals on a cylindrical photoreceptor. Each of the respective latent images are written during one rotation of the photoreceptor. The initial writing positions of the respective latent images are registered by using a drum index signal generated in synchronization with the rotation of the photoreceptor. An optical output starts outputting an optical signal in response to the index signal or an encoder signal selected according to the copy mode.