US Patent 7369147 Image forming apparatus and control method thereof

An image forming apparatus includes a first writing control device configured to control a writing of a first latent image, a second writing control device configured to control a writing of a second latent image, and a criterion timing determination device configured to determine a criterion timing for a series of image forming operations based on an image forming instruction and to transmit to the first writing control device one of (i) a signal of the criterion timing, or (ii) a signal of a writing instruction determined based on the criterion timing. The first writing control device is configured to start a writing process of the first latent image based on one of the signal of the criterion timing or the signal of the writing instruction received from the criterion timing determination device, and to transmit a signal of a timing for starting a writing process to the second writing control device. The second writing control device is configured to start the writing process of the second latent image based on the signal of the timing for starting the writing process received from the first writing control device.