Abstract: A laser beam printing machine according to the present invention includes a polygon mirror motor; a first control circuit which generates, in response to an error in rotation of the polygon mirror motor, a control signal which bring about the rotation of the polygon mirror motor to a target rpm and performs a PWM control; an output circuit which receives data for printing and, in response to the received data, outputs data for controlling a laser beam; a voltage controlled oscillator which generates clock pulses for determining the transmission timing of the data from the output circuit; and a second control circuit which controls, in response to the control signal, a control voltage of the voltage controlled oscillator to follow up the rotation fluctuation of the polygon mirror motor.

Abstract: In the present invention, data with regard to passing time of respective sides of a polygon mirror when a polygon motor is in a predetermined rotating condition is stored in a memory at the respective addresses, the memory is accessed in response to the rotation of the polygon mirror and the data on the side (reflection face) performing the scan on a photo sensitive drum are successively generated while corelating with the scan, a difference between a target rotating amount under a proper standard rotation of a particular side and an actual rotating amount of the particular side is obtained time to time for respective sides of the polygon mirror, which depends on the processing accuracy of the respective sides, thereby even the polygon motor having a poor processing accuracy can be controlled at the standard rotation so that the scanning speed by the rotation is brought about to a target value like a polygon motor having a high processing accuracy.

Abstract: A laser beam printing device for conducting the print includes a control circuit for controlling a rotation speed of a rotation mirror which reflects the laser beam to scan, an image processing circuit for outputting image information in synchronism with an origin pulse signal, and an origin sensor to receive the laser beam to generate a detection signal and to transmit the signal to the image processing circuit as the origin pulse signal. The control circuit receives the detection signal from the origin sensor as a signal for detecting the rotation speed of the rotation mirror.