Patent ID: 7477436

Claim:
A scanning optical system configured to scan laser light on a scanned surface in a predetermined scanning direction, comprising: a light source configured to emit the laser light; a converging element configured to converge the laser light emitted by the light source in the predetermined scanning direction; a deflector configured to deflect the laser light converged by the converging element so as to scan the laser light on the scanned surface in the predetermined scanning direction; and a scanning speed controlling element configured to control the laser light deflected by the deflector to be scanned on the scanned surface at a constant scanning speed, wherein the scanning optical system is configured to satisfy conditions (1) and (2): f > - K / M ( 1 ) W 2 ⁢ sin ⁢ ⁢ α > f ⁡ ( 2 - M / m ) - K / m > d ⁢ ⁢ W 2 ⁢ K ⁢ ⁢ sin ⁢ ⁢ α ( 2 ) where f represents a focal length of the converging element, K represents a scanning coefficient of the scanning speed controlling element, M represents a magnification of the scanning optical system in the predetermined scanning direction, W represents a scanning width of the laser light on the scanned surface, α represents an angle, on a scanning plane of the laser light deflected by the deflector in the predetermined scanning direction, between an optical axis of optical elements provided between the light source and deflector and the optical axis of the scanning speed controlling element, m represents a magnification of the scanning speed controlling element in the predetermined scanning direction, and d represents a distance from the deflector to the scanning speed controlling element.