Patent ID: 7158269

Claim:
A scanner comprising: a light-beam emitter for emitting a light beam; a light-beam deflector for deflecting said light beam to scan a scanning surface; a photo-detector provided at a position outside an image-forming scanning range of said scanning surface to detect a scanning light beam before said scanning light beam starts generating a scanning line in said image-forming scanning range; a rotatable member located in front of an incident surface of said photo-detector and positioned in a recess formed on an outer surface of a housing, said rotatable member being rotatable about a rotational axis perpendicular to a plane defined by said scanning light beam by said deflector; an optical, member that is provided on said rotatable member, said optical member allowing said scanning light beam to pass therethrough to be incident upon said incident surface of said photo-detector; and a device for adjusting rotational, position of said rotatable member about said rotational axis; wherein a through hole through which said optical member is inserted in said housing is formed at the bottom of said recess, and said optical member is inserted into said housing through said through hole.