Patent ID: 7515322

Claim:
A beam scanning device, comprising: a light source to emit a light beam; an optical deflector to deflect the light beam; an optical system including a fθ lens to guide the defected light beam to a scan surface to form an image thereon; a synchronization detecting sensor to detect the deflected light beam outside an area of the image; a light blocking member configured to block the deflected light beam on an exit side of said fθ lens outside an effective scan area that includes the area of the image and also includes an optical path extending to said synchronization detecting sensor; and a metal housing accommodating said light source, said optical deflector, said optical system, said light blocking member, and said synchronization detecting sensor, wherein said light blocking member is separate from said fθ lens, and is configured to block the deflected light beam on the exit side of said fθ lens in a region that extends in a beam scan direction from a discontinuous point of said fθ lens to outside the effective scan area, wherein said light blocking member is a single integral piece made of a metal plate including: a first portion configured to block flare light of the light beam outside the effective scan area on an upstream side of a scan path of the light beam; a second portion configured to block flare light of the light beam outside the effective scan area on a downstream side of the scan path of the light beam; and engaging members provided on opposite ends of the metal plate to engage the metal housing, wherein the first portion and the second portion are two identical parts of the metal plate situated symmetrically on two sides, and are each situated at the exit side of the fθ lens and in close proximity to the fθ lens to extend outwards from the discontinuous point in the beam scan direction, wherein the metal plate further includes a connection plate configured to connect the first portion and the second portion and including the engaging members provided on opposite ends thereof, the first portion and the second portion being parts of the metal plate bent substantially at a right angle relative to the connection plate, and wherein, in an engaged position in which the light blocking member is attached to the housing, the connection plate is positioned above the fθ lens to extend substantially parallel to a side surface of the fθ lens, and the first portion and the second portion extend downward from the connection plate to block the flare light of the light beam passing through the fθ lens.