| 摘要 |
PURPOSE:To improve environmetal resistance of optical parts and to obtain stable optical characteristics by forming a multilayer film on a substrate in such a manner that the layer most distant from the substrate or the layer adjacent to the most distant layer is made a metal film and other layers are made dielectric films. CONSTITUTION:For example, a multilayered film 3 of at least five layers is formed on the slope of a first substrate 2 made of a transparent material in a prism form for a beam splitter 1. The outermost layer is a metal film 3a such as Al, Au, Pt, Ag, Cu, and Cr, and other layers are dielectric films 3b. The metal film 3a is made to adhere through an adhesive layer 4 to a second substrate 5 made of a transparent material in a prism form. Since the metal film 3a is present between the dielectric film 3b and the adhesive layer 4, the effect of the water content in the adhesive layer 4 on the dielectric film 3b due to changes in the environment can be prevented, and optical characteristics of the dielectric film 3b can be stabilized. |
