Patent ID: 7151624

Claim:
A light scanning unit comprising: a composite light source comprising a plurality of light sources arranged adjacent to one another for emitting coherent light having different wavelengths, as a light beam; and an optical system comprising a collimator lens which is arranged on an approximately central axis of the light beam emitted by the composite light source and collimates the light beam emitted from the composite light source, a cylinder lens for condensing the light beam emitted from the collimator lens, and a polygonal rotating mirror for scanning the light beam condensed by the cylinder lens in a main scanning direction on an exposed surface of at least one exposed object, a half mirror, which splits the light beam emitted from the composite light source; an optical element, which comprises a band pass filter for transmitting light having a predetermined wavelength of the light beam split by the half mirror and splits light with respect to different wavelengths after being reflected by the polygonal rotating mirror; and a F-θ lens arranged on a light path between the half mirror and the band pass filter.