ILLUMINATION DEVICE, PROJECTION DEVICE, SCANNER AND EXPOSURE DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an illumination device capable of accurately determining whether or not a characteristic of a diffractive optical element has changed with a simple configuration without losing necessary diffraction light.SOLUTION: An illumination device 10 includes: a light source 11; a diffractive optical element 12 for diffracting light L10 emitted from the light source, and for illuminating an illumination region by diffraction light L11; a first photodetector 13 for detecting at least one part of regular reflection light L12 reflected at an incident surface of the diffractive optical element; a second photodetector 14 for detecting at least one part of unnecessary diffraction light L13 generating at the diffractive optical element; and a determination part 15 for calculating a relative value of a first detection value of the first photodetector and a second detection value of the second photodetector, and based on the change in the relative value and in the first detection value, determining whether or not the characteristic of the diffractive optical element has changed.