| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical element, an optical system and optical equipment having an antireflection film that can maintain an excellent antireflection effect on a substrate composed of a material having a medium to low refractive index.SOLUTION: An optical element 100 is provided, which includes a substrate 110 made of glass transparent to light in a use wavelength region from 400 nm to 700 nm and an antireflection film 120 formed on the substrate. The antireflection film includes, successively from the substrate side, a first layer 122 as an inorganic oxide film essentially comprising silica, a second layer 124 as an inorganic oxide film, and a third layer 130 as a film containing silica fine particles. The antireflection film satisfies specific conditions in regard to a refractive index Nk of the substrate, a refractive index n1 and a physical film thickness d1 (nm) of the first layer, a refractive index n2 and a physical film thickness d2 (nm) of the second layer, and a refractive index n3 and a physical film thickness d3 (nm) of the third layer.SELECTED DRAWING: Figure 1 |
