Patent ID: 6055039
Filing Date: 2000-04-25
Classification: G03F

Abstract:
An illumination system, comprising:a fly's eye lens comprising lens elements each having an approximately oblong shape in section perpendicular to an optical axis of said illumination system, the oblong shape having a longer side and a shorter side; andan optical system for separating light from a light source into plural lights and for directing the plural lights toward said fly's eye lens along different directions, said optical system being arranged so that paths of the plural lights are juxtaposed along a lengthwise direction of the oblong shapes,wherein the following conditions are satisfied:.THETA.a>.THETA.bc; and.THETA.b.apprxeq..THETA.bc,in which a section A is taken along a plane parallel to the longer side of the lens elements and which includes the optical axis and a section B is taken along a plane parallel to the shorter side of the lens elements and which includes the optical axis, and in which in section A, a maximum angle defined between the optical axis and a light ray impinging on the lens elements is .THETA.a, in section B, a maximum angle defined between the optical axis and a light ray impinging on the lens elements is .THETA.b, in section A, the maximum angle defined between the optical axis and a light ray which can be transmitted by the lens elements is .THETA.ac, and in section B, the maximum angle defined between the optical axis and a light ray which can be transmitted by the lens elements is .THETA.bc.