Patent ID: 8228580

Claim:
An optical scanner, comprising: a plurality of scanning optical systems each of which scans a different surface to be scanned and, each scanning optical system includes, a light source configured to emit a light beam, and a synchronization detector; and an optical deflector having a plurality of reflection surfaces each reflecting the light beam emitted from the light source to scan the surface, the optical deflector being commonly used in the plurality of scanning optical systems, wherein the synchronization detector of each scanning optical system is configured to receive the light beam deflected by the optical deflector and detect a timing to scan an effective area of the surface to be scanned with the deflected light beam before a scanning is started or after the scanning is completed, each of the plurality of scanning optical systems has at least one lens, the synchronization detector of each scanning optical system is positioned on a side of the optical deflector opposite to the light source with respect to a plane which passes through a longitudinal center of the at least one lens of one scanning optical system and a longitudinal center of the at least one lens of another scanning optical system, the plane being parallel to a rotational axis of the optical deflector, and no synchronization detectors being positioned on a same side as the light source with respect to the plane which passes through the longitudinal centers of the lenses, the plurality of scanning optical systems include at least one pair of scanning optical systems disposed on opposite sides of the optical deflector to each other, and the synchronization detector of one of the pair of scanning optical systems is disposed on a scanning end side where the scanning of the effective area of the surface to be scanned is finished to determine the scanning timing, and the synchronization detector of the other one of the pair of scanning optical systems is disposed on a scanning start side where the scanning of the effective area of the surface to be scanned is started to determine the scanning timing, wherein each of the plurality of scanning optical systems includes a light-flux dividing unit which is disposed between the light source and the optical deflector and is configured to divide light flux of the light beam emitted from the light source into a plurality of light fluxes, and a plurality of mirrors configured to reflect the plurality of light fluxes, respectively, from the light dividing unit such that the plurality of light fluxes enter the respective reflection surfaces of the optical deflector to have an angle of π/2 in a plane that is perpendicular to the rotational axis of the optical deflector.