Patent ID: 7355765

Claim:
An optical scanning apparatus that produces an electrostatic latent image on a target scanning surface by scanning a laser beam on the target scanning surface in a main scanning direction that is perpendicular to a sub-scanning direction in which the target scanning surface moves, the laser beam being periodically deflected by a rotating polygon mirror, comprising: a sync detection sensor for generating and outputting a sync detection signal that specifies a writing start position of the laser beam in the main scanning direction by detecting the laser beam at a place that is outside of an image domain of the target scanning surface in the main scanning direction, a pixel clock generation unit for generating and outputting a pixel clock that is synchronized with the sync detection signal that is output by the sync detection sensor, and a phase setting unit for changing a phase of the pixel clock output for each of a plurality of division periods that are formed by dividing a scanning period of the laser beam, wherein the phase setting unit is capable of carrying out a partial phase change that changes the phase in a time period shorter than one cycle of the pixel clock.