Patent ID: 7324187
Filing Date: 2008-01-29
Classification: G03B,G03F

Abstract:
1. An illumination optical system for illuminating a surface to be illuminated, with light from a light source, said illumination optical system comprising: a field stop disposed in a portion of a light path between the light source and the surface to be illuminated, said field stop being configured to regulate an illumination region upon the surface to be illuminated; and a sensor configured to monitor a quantity of light from the light source, wherein the light from the light source has a wavelength in a range of 20 nm to 5 nm, wherein said field stop includes a slit member having a slit-like opening and two light blocking plates configured to block light from the light source passing through opposite end portions of the slit-like opening of said slit member, and wherein said sensor is disposed on at least one of said two light blocking plates to monitor the quantity of light passing through at least one of the opposite end portions of the slit-like opening of said slit member.