Patent ID: 8199404

Claim:
An anti-reflection coating comprising first to seventh layers formed on a substrate in this order, said first layer being an alumina-based layer, said seventh layer being a porous, silica-based layer, and in a wavelength range of 400-700 nm, said substrate having a refractive index of 1.60-1.95, said first layer having an optical thickness of 37.5-112.5 nm, said second layer having a refractive index of 1.95-2.25 and an optical thickness of 35.5-60.0 nm, said third layer having a refractive index of 1.35-1.50 and an optical thickness of 24.5-41.5 nm, said fourth layer having a refractive index of 1.95-2.25 and an optical thickness of 210.5-250.0 nm, said fifth layer having a refractive index of 1.35-1.50 and an optical thickness of 12.5-32.5 nm, said sixth layer having a refractive index of 1.95-2.25 and an optical thickness of 27.5-45.0 nm, and said seventh layer having an optical thickness of 108.0-138.0 nm.