Patent ID: 7177060

Claim:
An optical scanning apparatus which makes a light beam scan on a surface-to-be-scanned in a main scanning direction, comprising: a deflector which comprises a deflection mirror surface reflecting an incident light beam, and displaces said deflection mirror surface about a drive axis which is approximately orthogonal to the main scanning direction, thereby deflecting the incident light beam in the main scanning direction; a light source which emits the light beam; a first optical system which shapes the light beam from said light source and makes the light beam impinge upon said deflection mirror surface at an acute angle with respect to a reference surface which is orthogonal to the drive axis, and from above or below relative to the reference surface in a direction of the drive axis; and a second optical system which makes the light beam form an image on the surface-to-be-scanned, wherein an intersecting line which is formed as said deflection mirror surface intersects the reference surface at the position of incidence of the incident light beam upon said deflection mirror surface is a reference line, and a direction which is orthogonal to the main scanning direction is a mirror width direction, and said first optical system shapes the light beam from said light source so that the size of a spot of the incident light beam formed on said deflection mirror surface is larger than the width of said deflection mirror surface in the mirror width direction, when an optical axis of the incident light beam is orthogonal to the reference line.