| 摘要 |
PURPOSE:To generate a synchronizing signal at a proper timing by preparing divided sensors, which are arranged symmetrically with respect to the scanning direction of a light beam, from at least one of three uniformly arranged photosensors. CONSTITUTION:A light beam reception part 107 consists of six photo diodes P1 to P6, and three photo diodes and the other diodes are arranged adjacently in parallel and symmetrically with respect to the center of main scanning lines shown by an arrow, and three divided sensors (photosensors) are arranged symmetrically with respect to the scanning direction of the light beam. The total width of the beam reception part 107 in the main scanning direction is short for the purpose of sharpening the rise and the fall of detection and has a diameter defined by 1/e2 of the center intensity of the laser beam. Detection signals of photo diodes P1 to P6 are inputted to a processing circuit group constituting a light beam detecting mechanism and are amplified and are inputted to an arithmetic circuit for electric signal processing. |
