Illumination device, image display device, and projector

摘要

An illumination device includes: a light source unit that emits coherent light; and a diffractive optical element that diffracts the coherent light emitted from the light source unit and makes the diffracted light travel to an illuminated surface. The diffractive optical element is disposed such that the coherent light is incident in a state of being inclined with respect to a perpendicular line of a reference plane on which the diffractive optical element is disposed. Zero-order light, which is light other than the diffracted light, of light components emitted from the diffractive optical element travels to a position other than the illuminated surface.