| 摘要 |
PURPOSE:To form an antireflecting film which is effective to a wide range of high- wavelength regions by using the same low-refractive index material to the odd layers of the antireflecting film which is formed of 6 layers and the same intermediate- refractive index material to the even layers in accordance with the specific conditions as the materials for the respective layers of the above-mentioned film. CONSTITUTION:The incident medium of the antireflecting film which is formed of the 6 layers is air and the material of a substrate 7 is SiO2. The low-refractive index material MgF2 which exhibits the refractive index lower than the refractive index of the substrate 7 is used for the odd layers 1, 3, 5 and the LaF3 which is the material different from the above-mentioned material and exhibits the refractive index higher than the refractive index of the substrate 7 is used for the even layers 2, 4, 6. The thicknesses of the respective layers are set at an about 0.3-0.6 range in total of the optical film thicknesses of the 4th-6th layers 4, 5, 6 with respect to a designed main wavelength lambda0. The film thicknesses have the prescribed range or value as a standard and the antireflection effect is lowered when the permissible range is exceeded. As a result, the respective layers are constituted of two kinds of the materials and the antireflecting film effective to a wide range of the wavelength regions is obtd. |
