Patent ID: 7236239

Claim:
An illumination system for illuminating a surface to be illuminated, with light from a light source, said illumination system comprising: a first optical integrator having a first cylindrical lens group, a second cylindrical lens group, a third cylindrical lens group and a fourth cylindrical lens group, for forming a plurality of first secondary light sources by use of light from the light source, wherein said first to fourth cylindrical lens groups are disposed along an optical axis direction of said illumination system; a second optical integrator for forming a second secondary light source by use of light from the first secondary light sources; a first collecting optical system for superposing light from the first secondary light sources on a light entrance surface of said second optical integrator; a second collecting optical system for superposing light from the second secondary light source on the surface to be illuminated; and a driving mechanism for decentering at least one of said first to fourth lens groups in a light path of said illumination system along a plane perpendicular to the optical axis, to shift an illumination range upon the light entrance surface of said second optical integrator thereby to adjust telecentricity of light illuminating the surface to be illuminated; wherein said first and third cylindrical lens groups have a refractive power with respect to a first direction being perpendicular to the optical axis, while said second and fourth cylindrical lens groups have a refractive power with respect to a second direction being perpendicular to the first direction; and wherein, when the illumination range is to be shifted in the first direction, said driving mechanism decenters one of said first and third cylindrical lens groups, and wherein, when the illumination range is to be shifted in the second direction, said driving mechanism decenters one of said second and fourth cylindrical lens groups.