Patent ID: 6870580

Claim:
An illumination optical system for guiding light from a light source unit having a light-emitting element and a reflector, and an integrator unit which is downstream from the reflector and an image display light valve element downstream from the integrator, wherein at least one curved mirror is disposed between said integrator unit and said image display light valve element; wherein said curved mirror is a parabolic mirror; and wherein said parabolic mirror has a form, in a cross section including an optical path of the light from said light source unit to said image display light valve element, satisfying the following conditional expression (1) or (2): f={−L±L[ 1+(tan θ) 2 ] 1/2 }/2 tan θ (1) f=L 2 (2) where θ≠90+180n (n being an integer) degrees in conditional expression (1); θ=90+180n (n being an integer) degrees in conditional expression (2); f is the focal length of the parabolic mirror (where f>0); L is the distance between the optical axis off luminous flux before reflection and z axis of the parabolic mirror; and θ is the optical axis bending angle caused by reflection of the parabolic mirror.