Patent ID: 6816293
Filing Date: 2004-11-09
Classification: G02B

Abstract:
A scanning optical device comprising light source means and an optical element having a refraction portion and a diffraction portion,wherein powers of said refraction portion and said diffraction portion are set such that an imaging position deviation in a main scanning direction on a surface to be scanned that is caused by a wavelength variation of a beam emitted by said light source means along with an environmental fluctuation of said scanning optical device, and an imaging position deviation in the main scanning direction on the surface to be scanned that is caused by a refractive index variation of a material of said optical element along with an environmental fluctuation are set to be in opposite directions at two ends of an effective scanning region, wherein an imaging position variation per unit mode hopping of said light source means is not more than 3 &mgr;m at the two ends of the effective scanning region, and wherein, letting &phgr;Ls and &phgr;Ds be powers of said refraction portion and diffraction portion, respectively, in a sub-scanning direction, those powers satisfy a condition: 1.0&lE;&phgr;Ls/&phgr;Ds&lE;2.6.