Illumination optical system and projector using the same

A projector comprising:

• an illumination optical system;
• a light modulation device for modulating light given from the illumination optical system according to image information;
• a projection optical system for projecting the modulated light;
• and
• a base frame for mounting a plurality of optical components disposed on a light path from the optical illumination system to the projection optical system,
• wherein the illumination optical system comprises:
• a light source;
• a lens array including a plurality of small lenses for dividing light emitted from the light source into a plurality of light bundles;
• and
• a superimposing lens system for superimposing the plurality of light bundles on the light modulation device,
• wherein the base frame includes a positioning section for positioning at least the superimposing lens system and is capable of being used in common for another illumination optical system;
• and
• the superimposing lens system comprises at least two lenses including a first lens and a second lens;
• the first lens being provided at a position nearest to the light source and mainly determining an F-number of the illumination optical system, and the second lens being provided at a position furthest from the light source and mainly determining a magnification of the illumination optical system,
• and wherein the F-number and the magnification of the illumination optical system are capable of being changed by replacing the first and second lenses with other lenses having different focal lengths, without changing the positions of the first and second lenses in the base frame.

An illumination optical system for illuminating a predetermined illumination area comprising:

• a light source;
• a lens array including a plurality of small lenses for dividing light emitted from the light source into a plurality of light bundles;
• a superimposing lens system that includes a plurality of lenses and superimposes the plurality of light bundles on the predetermined illumination area;
• and
• a base frame that disposes the plurality of lenses so as to be replaceable with other lenses having different focal lengths and is capable of being used in common for another illumination optical system,
• wherein the F-number and the magnification of the illumination optical system are capable of being changed by replacing the plurality of lenses with other lenses having different focal lengths, without changing the positions of the plurality of lenses in the base frame.