Patent ID: 7167288
Filing Date: 2007-01-23
Classification: G02B,H04N

Abstract:
1. An optical scanning unit comprising: an optical deflector that deflects light beams emitted from a plurality of light sources corresponding to each of a plurality of colors; a plurality of scanning optical systems that focuses the light beams deflected by the optical deflector on a writing area corresponding to each of the colors on a surface to be scanned; and a pixel-clock generating unit that causes the optical deflector to scan the light beams emitted from the light sources on the surface to be scanned along a scanning direction to shift phases of respective signals of a pixel clock that forms an image based on phase-shift data according to timing of a clock signal, wherein a photodetector that detects the light beams is arranged in at least two locations on a writing-start side and a writing-end side outside the writing area, and the optical scanning unit measures a scanning time, during which light beams pass through each photodetector arranged in one of the at least two locations, and corrects respective dot positions of image data in the writing area to arbitrary positions based on an amount of fluctuation of the scanning time measured.