Patent ID: 6310729
Filing Date: 2001-10-30
Classification: G02B

Abstract:
A dichroic mirror comprising:a transparent substrate;a dielectric multilayer film formed on said transparent substrate by alternately laying high refractive index layers, each having an optical thickness of .lambda./48, .lambda. being the designed central wavelength, and low refractive index layers, each having a refractive index lower than that of the high refractive index layers;a first transmittance regulating film formed between said dielectric multilayer film and said transparent substrate; anda second transmittance regulating film formed on said dielectric multilayer film at the side opposite to said transparent substrate,wherein said first and second transmittance regulating films are formed by alternately laying intermediate refractive index layers and low refractive index layers, said intermediate refractive index layers having a refractive index lower than that of said high refractive index layers and higher than the median of the refractive index of said high refractive index layers and that of said low refractive index layers.