| 摘要 |
PURPOSE:To reduce the cost of a device by performing PLL (Phase Locked Loop) control over a polygon mirror driving motor according to the deviation between the detection signal of a photodetecter which detects the scanning start point of a laser beam and a reference signal. CONSTITUTION:The photodetecter 5 which receives the laser beam at the start of the scanning of the laser beam is arranged at one side part of a photosensitive body and laser beams consisting of image signals of respective lines are modulated in synchronism with its detection signal to form a latent image on the photosensitive body, one by one line. The motor 2 which rotates a polygon mirror 1 is brought under the PLL control according to the deviation between the detection signal of the photodetecter 1 and the constant-period reference signal. Consequently, neither the mechanism of a rotary encoder which detects the rotation state nor an external circuit which controls it needs to be provided specially in the motor 1 and the device cost is reduced. |
