ILLUMINATION SYSTEM, ILLUMINATION UNIT AND IMAGE PROJECTION APPARATUS EMPLOYING THE SAME

摘要

An illumination optical system, an illumination unit, and an image projection device adopting the same are provided to effectively collect the light emitted from a lens optical system and the extra axial light by decreasing misalignment of a reflective direction of the extra axial light for the axial light generated from a reflecting optical system through the lens optical system although a light source is not shown as a point light source. An illumination optical system is composed of a light source(10) for emitting the diverging light; a reflecting optical system(11) for collecting the diverging light emitted from the light source; and a lens optical system(12) for projecting the light collected in the reflecting optical system. The reflecting optical system is a concave mirror having an aspherical surface. The lens optical system includes a focusing lens with an aspherical surface having the positive refractive power in center portions(11A,12A). The refractive power of the lens optical system is gradually reduced toward peripheral parts(11B,12B).