| 摘要 |
PURPOSE:To reduce the influence caused by a disturbance noise being pulsative and periodical, by controlling the intensity of a laser output beam by means of the average value of a beam from each reflection surface of a laser beam scanning polygon mirror. CONSTITUTION:An output beam from the laser diode 16 passes through the collimater lens system 4, is relfected by each surface of the polygon mirror 3, is projected on the photosensitive body 1 through the f-theta lens 2, and a modulation signal is written by horizontally scanning on the photosensitive body surface. In this case, prior to each horizontal scanning, a laser beam is led into the photodetector 6 through the reflection mirro 5, its output current is converted to voltage by the amplifier 7, it is integrated by the integrating circuit 8, the average value is derived by sample-holding 13 the integral output, and a drive current of the laser diode is varied in accordance with the output of the circuit 13. As a result, the light intensity of the laser beam on the photosensitive body 1 becomes constant. |
