Light source device, and illuminating optical system and projector including the same

摘要

A light source device 150A includes a light source lamp 25 consisting of a discharge lamp 22 and an elliptical reflector 24, and an aspherical lens 30A. In the aspherical lens 30A, an incidence surface 30Ai is a plane surface, and an emission surface 30Ao is an aspheric concave surface. By forming the shape of the aspheric surface into the shape of a quadric surface of revolution determined on the basis of a predetermined expression, light of high parallelism can be emitted.