Patent ID: 8477414

Claim:
An optical element comprising: a first optical layer having a light emission surface; a wavelength-selective reflective layer provided on the first optical layer; and a second optical layer provided on the wavelength-selective reflective layer and having a light incidence surface, wherein the wavelength-selective reflective layer has a structure including at least five layers in which high refractive-index layers and metal layers are alternately laminated to each other, when a geometric film thickness L of the entire wavelength-selective reflective layer is 80 nm, a ratio α of an optical film thickness of the entire metal layers to an optical film thickness of the entire high refractive-index layers and a ratio β of an optical film thickness of a third high refractive-index layer from one of a first optical layer side and a second optical layer side to an optical film thickness of a first high refractive-index layer therefrom are included in a first region surrounded by the following formulas (1) to (4), when the geometric film thickness L of the entire wavelength-selective reflective layer is 90 nm, the ratio α and the ratio β are included in a second region surrounded by the following formulas (5) to (8), and when the geometric film thickness L of the entire wavelength-selective reflective layer is in a range of 80 to 90 nm, the ratio α and the ratio β are included in a space enclosed by the first region, the second region, and the following formulas (9) to (12) α=−0.0004β 2 +0.0053β+0.0065 (1) α=−1×10 −5 β 2 +0.0007β+0.0066 (2) α=−1×10 −5 β 2 +0.0005β+0.0119 (3) α=0.012114 (4) α=−0.0002β 2 +0.0039β+0.0087 (5) α=−3×10 −5 β 2 +0.0014β+0.0038 (6) α=−2×10 −5 β 2 +0.0006β+0.0112 (7) α=0.010589 (8) (β−0.5)/0.67=(α−0.01059)/0.00152478=(90− L )/10 (9) (β−5.5)/3.75=(α−0.01059)/0.00152478=(90− L )/10 (10) (β−10.4)/10.6=(α−0.01516)/0.00067768=(90− L )/10 (11) (β−0.8)/0.45=(α−0.01161)/0.0008471=(90− L )/10 (12).