Patent ID: 6833940
Filing Date: 2004-12-21
Classification: G02B

Abstract:
An optical scanning apparatus comprising:a predetermined number M of light sources emitting a laser light beam; a first optical scanning lens system configured to perform a coupling process relative to the laser light beam emitted from the predetermined number M of light sources; a second optical scanning lens system configured to gather light of the laser light beam from the first optical scanning lens system in an approximately linear state extended in a main scanning direction; a rotary polygon mirror having a predetermined number N of deflective reflection surfaces and configured to receive and deflect the laser light beam gathered in the approximately linear state; and a third optical scanning lens system configured to gather the deflected laser light beam from the rotary polygon mirror to form a beam spot on an imaging surface, wherein the predetermined number M satisfies a condition: 3Ã—Rp/Rmax&gE;M&gE;Rp/Rmax, wherein Rp and Rmax are defined as: Rpâ‰¡(Dpi/25.4)Ã—(260Ã—Ppm)/N, Rmaxâ‰¡(5.4Ã—106)Ã—âˆš{N1.6/(A4Ã—t)}, respectively, wherein M is greater than two, Rp is a revolution number (rpm) of the rotary polygon mirror in a single beam mode, Rmax is a maximum revolution number (rpm) of the rotary polygon mirror, Dpi is a pixel density (dpi) in a sub-scanning direction, Ppm is a print speed (ppm)expressed in a number of A4-sized print pages in a landscape orientation, N is a number of the deflective reflection surfaces of the rotary polygon mirror, A is a radius (mm) of an inscribed circle with respect to the deflective reflection surfaces of the rotary polygon mirror, and t is a thickness (mm) of each deflective reflection surface of the rotary polygon mirror.