| 摘要 |
PURPOSE: To make it possible to produce a reflection mirror in a small size at a low cost with a simple constitution and to accurately reflect light by forming reflection films and thin films having respectively the same structures on both surfaces of a nearly parallel flat plate, thereby forming the reflection mirror. CONSTITUTION: The reflection mirror 16 has the parallel flat plate 16a and the reflection film 16b for polarizing luminous fluxes formed at one surface of this flat plate and has a thin film 16c of nearly the same structure as the structure of the reflection film 16b formed on the other surface of the parallel flat plate 16a. Accordingly, the stresses on the flat plate 16a by the reflection film 16b are offset by the stresses on the flat plate 16a by the thin film 16c. Then, the stresses generated in the flat plate 16a by the change in temp. and humidity are eliminated and, therefore, the flatness on the surface of the reflection film 16b of the reflection mirror 16 is maintained in high accuracy. Even if, therefore, the reflection mirror is constituted relatively thin, the flatness of the reflection surface is not impaired and the reflection mirror of the small size and light weight is produced at a low cost. |
