Patent ID: 7535643

Claim:
A folding mirror comprising: a substrate; and a dielectric multilayered film formed on a surface of the substrate, the dielectric multilayered film comprising: a first period layer with a structure represented by a formula (0.58H1.16L0.58H) N1 ; a second period layer with a structure represented by a formula (0.8L1.6H0.8L) N2 ; and a third period layer with a structure represented by a formula (0.95L1.9H0.95L) N3 , wherein, H represents a thickness of a high refractive index layer being set at ¼ of a reference wavelength associated with the film, and L represents a thickness of a low refractive index layer being set at ¼ of a reference wavelength associated with the film, N1, N2, and N3 represent the numbers of repetitions of the structures, enclosed by the corresponding parentheses.