| 摘要 |
PURPOSE:To provide an antireflection effect to light incident at 45 deg. angle from a medium side by forming the antireflection film in such a manner that the even layers of multilayered films have the refractive index higher than the refractive index of a substrate, the refractive index of the even layers is lower than the refractive index of the substrate and the optical film thicknesses of the respective layers satisfy specific conditions. CONSTITUTION:The multilayered films of the antireflection film 7 consist of 7-layered films of the 1st to the 7th layers successively from the medium side toward the substrate 1 side. The refractive index of the even layers is higher than the refractive index of the substrate 1 and is in a 1.40 to 1.48 range. The optical film thicknesses of the respective layers are so set as to satisfy the conditions of equation I where the refractive index of the i-th layer is designated as ni, the optical film thicknesses of the i-th layer are designated as nind and i is 1 to 7 integer. In the equation, lambda0 denotes a designed main wavelength; nd is the refractive index of the optical glass substrate to d rays in a 1.50 to 1.54 range. The decrease in transmitted light 5 by the reflection loss on the surface of the optical parts to be used at 45 deg. angle with the incident light 3 is prevented in this way. |
