Patent ID: 8414132

Claim:
A multiple-lights-combining illumination device, comprising: multiple light sources; multiple sub-rod integrators that respectively guide light from the multiple light sources; and a main rod integrator that guides light from the multiple sub-rod integrators, wherein each of the sub-rod integrators has reflection surfaces that are parallel to each other in a longitudinal direction, and has an entrance surface and an exit surface that are parallel or perpendicular to each other at ends thereof, the main rod integrator has reflection surfaces that are parallel to each other in a longitudinal direction, and has an entrance surface and an exit surface that are perpendicular to the reflection surfaces at ends thereof, and each reference optical axis that passes through an optical centroid portion of a light-emitting part of the light sources along a light emission direction is arranged so as to pass through substantially a center of the entrance surface of the respective sub-rod integrator, and the following relationship is satisfied: n 1 ·sin (θi−sin −1 (sin(θc)/n 1 ))>1 where θi represents an incident angle of each of the reference optical axes with respect to the reflection surface of the respective sub-rod integrator, θc represents an angle formed in air at the entrance surface of the respective sub-rod integrator by each of the reference optical axes and light at an outermost angle of effective incident light from the respective light source that is finally allowed to exit from the main rod integrator, and n 1 represents a refractive index of each of the sub-rod integrators.