Optical scanning device, and image forming apparatus equipped with the same

An image forming apparatus comprising:

• A photosensitive member;
• and
• an optical scanning unit for scanning photosensitive member,
• wherein said optical scanning unit comprises:
• a light source;
• a light deflector for deflecting a light beam emitted from said light source;
• a mirror for reflecting the beam deflected by said light deflector toward said photosensitive member;
• an optical box and a closing member mounted to said optical box, wherein said mirror is accommodated in a space defined by said optical box and said closing member;
• a pressing member for pressing said mirror to a seating surface of said optical box and for regulating a movement of said mirror in a direction of a normal line of a reflecting surface of said mirror, said pressing member pressing the surface of the mirror opposite to the reflecting surface toward the seating surface ;
• and a regulating portion for regulating movement of said mirror in a direction which is parallel to the seating surface and in which the mirror approaches the closing member, said regulating portion being a part of the optical box projecting toward the mirror from a plane coincident with the seating surface;
• wherein said mirror has a plurality of apex lines, and said pressing member and said regulating portion are disposed at positions which are remoter from said closing member than the apex line that is closest to said closing member, with respect to a direction perpendicular to a main scan direction.