Optical scanning apparatus and image forming apparatus

An optical scanning apparatas in which a light beam scans on a surface-to-be-scanned in a main scanning direction, comprising:

• a deflector which comprises a movable member which has a deflection mirror surface which reflects an incident light beam toward the surface-to-be-scanned, first adjacent portions which are fixedly disposed adjacent to said movable member over a first distance from said movable member on the both sides of said movable member in a direction of a pivot axis which is approximately orthogonal to the main scanning direction, second adjacent portions which are fixedly disposed adjacent to said movable member over a second distance from said movable member in the main scanning direction, a frame in which said first adjacent portions and said second adjacent portions are formed integral with each other, a pair of electrodes each of which is fixedly attached to said frame at a predetermined position, and beams which elongate in the direction of the pivot axis and link said movable member to said first adjacent portions to thereby hold said movable member such that said movable member freely pivots about the pivot axis, said deflector making said movable member pivot about the pivot axis, 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 into an elongated cross sectional shape which elongates in the main scanning direction, and makes the light beam impinge upon said deflection mirror surface;
• and
• a second optical system which makes the light beam deflected by said deflection mirror surface form an image on the surface-to-be-scanned, wherein
• the second distance is longer than the first distance,
• said movable member and said beams are formed integral with each other,
• said beams are fixedly attached to said frame, and
• the light beam, by means of said first optical system is incident upon said deflection mirror surface from a front side of said deflection mirror surface in such a direction;
• that a beam plane includes the pivot axis and is orthogonal to the main scanning direction, the beam plane being a plane which is formed by an optical axis of said first optical system and a surface normal, which passes the pivot axis, to said deflection mirror surface when a pivot angle about the pivot axis of said movable member is zero;
• and
• that the optical axis is at an acute angle with respect to the surface normal to said deflection mirror surface.