Patent ID: 7385760

Claim:
An optical element for reflecting and transmitting light comprising: a substrate; a thin film formed on the substrate, wherein the thin film reflects light in a predetermined reflection wavelength band so that the following condition is satisfied, 170°≦|Δ incidence −Δ reflection |≦190° where Δ incidence represents a phase difference between P-polarized light component and S-polarized light component of the incident light to the thin film, Δ reflection represents a phase difference between P-polarized light component and S-polarized light component of the light reflected by the thin film; and wherein the thin film transmits a light in a predetermined transmission wavelength band so that the following condition is satisfied, |Δ incidence −Δ transmission ≦10° where Δ transmission represents a phase difference between P-polarized light component and S-polarized light component of the transmitted light.