Patent ID: 6483529
Filing Date: 2002-11-19
Classification: B41J,G02B

Abstract:
A multibeam scanner for scanning an image forming area with a plurality of laser beams and forming a plurality of scanning lines corresponding to the plurality of laser beams in the image forming area, the multibeam scanner comprising:a plurality of beam emitting points that emit a plurality of laser beams, respectively; a scan position changing unit that changes scan positions at which the laser beams scan in the image forming area and in a non-image forming area; a timing controller that controls, in synchronism with the scan position changing unit, each of the plurality of beam emitting points to emit the laser beams during a respective beam emitting period one by one in the non-image forming area, the timing controller controlling the beam emitting point that last emits the laser beam among the plurality of the beam emitting points to emit the laser beam at a predetermined beam detecting position in the non-image forming area during its beam emitting period; a photoreceptor that detects each of the laser beams emitted one by one under the control of the timing controller, and outputs a beam amount signal indicating a beam amount of the laser beam; a beam amount controller that controls, based on the corresponding beam amount signals, the beam amounts of the laser beams emitted by the beam emitting points, respectively; a scan start timing detector that detects the last emitted laser beam at the predetermined beam detecting position in the non-image forming area, and determines a scan start timing upon the detection of the laser beam at the beam detecting position; and a scan controller that controls the beam emitting points, based on the scan start timing, to emit the laser beams, each of which beam amounts being controlled by the beam amount controller, thereby forming the plurality of scanning lines in the image forming area, wherein a time duration provided to the beam emitting point that last emits the laser beam under control of the timing controller in the non-image forming area is used not only for controlling the beam amount of the laser beam emitted from the beam emitting point that last emits the laser beam by the beam amount controller, but also for identifying the scan start timing, by use of the scan start timing detector during the time duration, for all laser beams, wherein the scan position changing unit comprises a deflector, that deflects the laser beams emitted by the beam emitting points, the deflector has a polygon mirror including a plurality of reflective surfaces and a plurality of edge portions provided between the reflective surfaces, and the timing controller inhibits the beam emitting points to emit the laser beams reaching any of the edge portions.