Patent ID: 8508717

Claim:
An illumination optical system which illuminates an irradiated plane with illumination light provided from a light source and which is used in combination with a projection optical system for projecting a pattern arranged on the irradiated plane onto a photosensitive substrate, the illumination optical system comprising: a diffuser which is arranged in an optical path of the illumination optical system and diffuses the illumination light incident on the diffuser; a spatial light modulator which is arranged between the diffuser and the irradiated plane and which includes a plurality of elements two-dimensionally arranged, each of the plurality of elements being controllable independently from one another and the plurality of elements receiving the illumination light diffused by the diffuser; a first optical system which is arranged in an optical path between the spatial light modulator and the irradiated plane and which distributes the light from the spatial light modulator to form a desirable light intensity distribution at a position optically conjugated with a pupil position of the projection optical system; and a second optical system which has an imaging optical system arranged in an optical path between the diffuser and the spatial light modulator.