Optical devices

Abstract

An illumination optical system for illuminating a photomask with a predetermined pattern comprises an optical system and an illumination system. The optical system has a plurality of light sources that emit pulsed light, a dividing part that divides the pulsed light emitted from the plurality of light sources into a first pulsed light and a second pulsed light, a delay optical system that guides the second pulsed light to a second optical path that is longer than the first optical path through which the first pulsed light passes, and a combining dividing part that combines the first pulsed light and the second pulsed light passing through the delay optical system and then divides the combined pulsed light before emitting it. The illumination system guides each of the pulsed light emitted from the optical system to the photomask to illuminate the photomask. none

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