Patent ID: 8027073

Claim:
An apparatus comprising: a light source to emit a laser beam; a resonant scanning mirror, including a reflection surface to reflect the laser beam emitted from the light source, and to scan the reflected laser beam by oscillating the reflection surface; at least one detector to detect the reflected laser beam during the scanning of the reflected laser beam, and generate a synchronizing signal each time the reflected laser beam is detected; and at least one light blocking unit, separate from the at least one detector and spaced between the at least one detector and the resonant scanning mirror, to restrict a path over which the reflected laser beam is incident on the at least one detector to a predetermined path, wherein the laser beam passes the at least one light blocking unit with each scan in one direction, and wherein the laser beam is incident on the at least one detector only when the resonant scanning mirror is disposed at a reference position and is operating normally, and when the resonant scanning mirror is deviated from the reference position, or when a scanning area of the laser beam is asymmetrical with respect to a center line, even though the resonant scanning mirror is disposed at the reference position but is not operating normally, the light blocking unit prevents the laser beam from being incident on the at least one detector.