Patent ID: 7557997
Filing Date: 2009-07-07
Classification: G02B,G03F

Abstract:
1. An immersion objective optical system for making a first plane and a second plane optically conjugate with each other, wherein when a gas in the immersion objective optical system has a refractive index of 1 for used light, an optical path between the immersion objective optical system and the second plane is filled with a liquid having a refractive index larger than 1.5 for the used light, the immersion objective optical system comprising a boundary optical element whose surface on the first plane side is in contact with the gas and whose surface on the second plane side is in contact with the liquid, the immersion objective optical system satisfying the following condition: where Rb is a radius of curvature of the surface on the first plane side of the boundary optical element, Eb an effective diameter of the surface on the first plane side of the boundary optical element, and Nb a refractive index for the used light, of an optical material forming the boundary optical element.