Patent ID: 8408709

Claim:
An illumination optical system, comprising: a first light source that emits a first light beam; a second light source that emits a second light beam; a light condensing optical system that condenses the first light beam and the second light beam; a polarization separation optical system that separates each of the first light beam and the second light beam into a first polarization component and a second polarization component; a ½ phase difference plate that converts a polarization state of the first polarization component to a polarization state equal to a polarization state of the second polarization component; a rod integrator that uniformizes spatial energy distribution of the first light beam and the second light beam that have undergone condensation by the light condensing optical system; and a relay optical system that forms an image of an exit face of the rod integrator on a region to be illuminated, wherein the light condensing optical system condenses the first polarization component onto a first region of an entrance face of the rod integrator, and condenses the second polarization component onto a second region of the entrance face of the rod integrator; and wherein the ½ phase difference plate is placed at the first region of the entrance face of the rod integrator or at a position conjugate with the first region of the entrance face of the rod integrator.