Patent ID: 6850348

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 in 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 an adjusting device for adjusting rotational position of said rotatable member about said rotational axis and comprising a member, fixed to said housing, that presses said rotatable member against the bottom of said recess.