Optical system illuminating surface to be illuminated, exposure apparatus, imprint apparatus, method for manufacturing article, optical element, and method for manufacturing optical system

Abstract

An optical system illuminating a surface to be illuminated includes a wavefront splitting type integrator configured to split the wavefront of incident light to form a plurality of light sources on the exit surface side, and an optical element whose surface is polished in a scanning direction using a polishing tool. The optical element is disposed between the wavefront splitting type integrator and the surface to be illuminated, and has a direction indicating portion indicating the scanning direction. The arrangement direction of the plurality of light sources in a plane perpendicular to the optical axis of the optical system is non-parallel to the scanning direction indicated by the direction indicating portion.

What is claimed is: 
     
         1 . A method for manufacturing an optical system for illuminating a surface to be illuminated, comprising:
 a disposing step of disposing an optical element on which a linear polishing mark is formed between an integrator that forms a plurality of secondary light sources from light from a light source and the surface to be illuminated,   wherein, in the disposing step, the optical element is disposed such that an arrangement direction of the plurality of secondary light sources in a plane perpendicular to an optical axis of the optical system is non-parallel to a direction in which the linear polishing mark extends.   
     
     
         2 . The method according to  claim 1 , wherein the optical element comprises a direction indicating portion indicating a direction in which the polishing mark extends. 
     
     
         3 . The method according to  claim 1 , wherein the optical element comprises a direction indicating portion indicating a scanning direction with a polishing tool for polishing a surface of the optical element. 
     
     
         4 . The method according to  claim 1 , wherein the optical element comprises a direction indicating portion is a surface formed in an outer periphery of the optical element and parallel to the direction in which the linear polishing mark extends. 
     
     
         5 . The method according to  claim 1 , wherein the optical element is an aspherical lens. 
     
     
         6 . The method according to  claim 1 , wherein the optical element is closest to the surface to be illuminated among a plurality of optical elements constituting the optical system. 
     
     
         7 . The method according to  claim 1 , wherein an angle formed between the arrangement direction of the plurality of secondary light sources and the direction in which the linear polishing mark extends is greater than or equal to tan−1 (C/P), where C is a size in the arrangement direction in a whole distribution of the plurality of secondary light sources formed by the integrator, and P is an external diameter of a light source among the plurality of secondary light sources. 
     
     
         8 . The method according to  claim 1 , wherein the plurality of secondary light sources are arranged in two directions perpendicular to each other and a direction oblique to the two directions, and the direction in which the linear polishing mark extends is non-parallel to the two directions and the oblique direction. 
     
     
         9 . The method according to  claim 1 , wherein the optical element is rotatable about the optical axis. 
     
     
         10 . The method according to  claim 1 , wherein the integrator is a wavefront splitting type integrator configured to split a wavefront of incident light to form the plurality of secondary light sources on an exit surface side. 
     
     
         11 . The method according to  claim 1 , the method further comprising:
 polishing a surface of the optical element by scanning in a scanning direction with a polishing tool,   wherein the linear polishing mark is formed on the polished surface of the optical element.   
     
     
         12 . The method according to  claim 1 , further comprising:
 measuring illuminance distribution on the surface to be illuminated, and   adjusting a rotation angle of the optical element about the optical axis using a result of measured illuminance distribution.   
     
     
         13 . A method for manufacturing an optical system for illuminating a surface to be illuminated, comprising:
 a polishing step of polishing a surface of the optical element by scanning in a scanning direction with a polishing tool,   a disposing step of disposing an optical element on which a linear polishing mark is formed between an integrator that forms a plurality of secondary light sources from light from a light source and the surface to be illuminated,   wherein, in the disposing step, the optical element is disposed such that an arrangement direction of the plurality of secondary light sources in a plane perpendicular to an optical axis of the optical system is non-parallel to a direction on the polished surface of the optical element corresponding to the scanning direction.