Patent ID: 6921176

Claim:
An illumination optical system, comprising: a first light source; a second light source having a different emission spectrum from an emission spectrum of the first light source; and a replacement optical system replacing light in a specific waveband in a luminous flux from the first light source with a luminous flux from the second light source, wherein the replacement optical system includes: a light synthesis device synthesizing and emitting a luminous flux incident from the first light source as a first linearly polarized luminous flux polarized in a first polarization direction and a luminous flux incident from the second light source as a second linearly polarized luminous flux polarized in a second polarization direction, a polarization rotating device selectively rotating only light polarized in the first polarization direction in the specific waveband in the luminous flux emitted from the light synthesis device to the second polarization direction and selectively rotating only light polarized in the second polarization direction in the specific waveband in the luminous flux emitted from the light synthesis device to the first polarization direction, and a polarizing device allowing only a linearly polarized luminous flux in the first polarization direction in the luminous flux emitted from the polarization rotating device pass through.