Patent ID: 6259557
Filing Date: 2001-07-10
Classification: G02B

Abstract:
A dark field illumination apparatus comprising:a light source to supply an illumination light;a shaping system to shape a light beam from said light source to an approximately parallel beam having a ring-shaped section;a wavefront splitting type optical integrator having a plurality of elements, which forms a plurality of light source images based on the approximately parallel beam having the ring-shaped section which is incident onto an incidence plane of the plurality of elements, the light source images being arranged circularly on a predetermined plane; anda light collection optical system to collect light beams from said plurality of light source images formed on said predetermined plane to superimpose the collected light beams on an object plane,a rear focal plane of said wavefront splitting type optical integrator and a front focal plane of said light collection optical system being disposed so as to be approximately coincident with each other, a curvature radius of an incidence plane of the optical integrator and a curvature radius of an exit plane of the optical integrator being equal to each other, the predetermined plane being the exit plane, and the rear focal plane of the optical integrator and the exit plane of the optical integrator being substantially coincident with each other.