Patent ID: 6320682
Filing Date: 2001-11-20
Classification: H04N

Abstract:
An apparatus for forming a multi-color image, comprising:a rotatable image carrying member having a peripheral surface;a plurality of image forming means each having a charging device so that the plurality of image forming means form the multi-color image during a single rotation of the image carrying member on the peripheral surface;each scanning exposure device of the plurality of image forming means including a beam generator and a polygonal mirror and being controlled such that the polygonal mirror is rotated at a same rotational speed as the other scanning exposure devices and such that a beam scans the peripheral surface in an axial direction of the image carrying member;a first sensor for detecting the beam passing at a start reference position on the peripheral surface and for outputting a start reference signal;a second sensor for detecting the beam passing at an end reference position on the peripheral surface and for outputting a stop reference signal;measuring means for receiving the start reference signal and the stop reference signal sequentially for each scanning exposure device and for measuring a time between the start reference signal and the stop reference signal; andcontrol means for controlling a frequency of clock pulses to transmit image signals for each scanning exposure device based on the measured time of each scanning exposure device;wherein each scanning exposure device is provided with an index sensor to detect the beam passing at a beam reference position of each scanning exposure device and to output an index signal, the measuring means receives the index signal for each scanning exposure device and measures a time between the index signal and one of the start reference signal and the stop reference signal, and the control means controls a timing to start writing an image with the beam on the peripheral surface for each scanning exposure device.