| 摘要 |
PURPOSE:To obtain a reflection preventing film which increases in mechanical strength without any deterioration in optical characteristics and also has excellent moisture resistance by providing a diamond thin film as a protection layer on the reflection preventing layer. CONSTITUTION:A substrate made of infrared-light transmittive material [e.g. AgBr (reflective index: 2.17), etc.] having a high refractive index is coated with the reflection preventing layer 2 made of material [e.g. KCl (refractive indes: 1.46), etc.] with a refractive index close to the square root of the refractive index of said infrared-light transmitter to thickness t=lambda/4n (where lambda is the wavelength of light in use and (n) is the refractive index of the film), and the protection layer 3 coated with the diamond thin film to a 0.01-0.5mum thickness is provided over the reflection preventing layer 2. Thus, the protection layer 3 is provided over the reflection preventing layer 2 to increase the mechanical strength of the layer 2 without any deterioration in optical characteristics, and the moisture resistance of the reflection preventing layer is improved. |
