OPTICAL ELEMENT AND OPTICAL APPARATUS

摘要

An optical element includes an optical surface having a multilayer film. The multilayer film comprises a stack that includes a first film having a first refractive index for a used wavelength and a second film having a second refractive index for the used wavelength smaller than the first refractive index. Outermost layers of the stack are configured by the first films. A film configuration of the stack has symmetry along with a stack direction. The predetermined conditional expressions are satisfied.

主权项

1. An optical element that includes an optical surface having a multilayer film,
wherein the multilayer film comprises a stack that includes a first film having a first refractive index for a used wavelength and a second film having a second refractive index for the used wavelength smaller than the first refractive index, wherein outermost layers of the stack are configured by the first films, wherein a film configuration of the stack has symmetry along with a stack direction, and wherein the following conditional expressions are satisfied:2UHUMtanΔH+UM2tanΔM-UH2tan2ΔHtanΔM2UHUMtanΔH+UH2tanΔM-UM2tan2ΔHtanΔM>0UH,M=nH,McosθiΔH,M=2πλinH,MdH,McosθH,M where λi is the used wavelength, θi is an incident angle of light incident on the multilayer film, nH is the first refractive index, nM is the second refractive index, dH is a physical thickness of the first film, and dM is a physical thickness of the second film.