Patent ID: 8123366

Claim:
An illumination device comprising: a light source device including an ellipsoidal reflector with a reflecting concave surface and a light emitting tube having an emission center in the vicinity of a first focal position of the ellipsoidal reflector, an integrator rod that converts the illumination light beam from the light source device into light having a more uniform in-plane light intensity distribution, wherein: defining a first focal position and a second focal position of the ellipsoidal reflector in a cross-sectional plane in a first virtual plane including a center axis of the ellipsoidal reflector as F 1 and F 2 , respectively, and defining a first focal position and a second focal position of the ellipsoidal reflector in a cross-sectional plane in a second virtual plane including a center axis of the ellipsoidal reflector and perpendicular to the first virtual plane as F 1 ′ and F 2 ′, respectively, the ellipsoidal reflector has a rotationally asymmetrical concave shape having F 1 and F 1 ′ at the same position, and F 2 located between the F 2 ′ and the ellipsoidal reflector, the integrator rod is configured to have a size of a light entrance surface of the integrator rod in a direction perpendicular to the first virtual plane larger than a size of the light entrance surface of the integrator rod in a direction perpendicular to the second virtual plane, F 2 is located at the light entrance surface of the integrator rod, and F 2 ′ is located at a position within the integrator rod.