| 摘要 |
PURPOSE:To reduce the surface reflection of optical material by holding a transparent sheet of a specified thickness having a refractive index smaller than the refractive index of the optical material being a target in close contact with the surface of the optical material. CONSTITUTION:In a reduced pressure vacuum chamber, a film 22 [e.g., polyethylene sheet of thickness 33mu (optical thickness 50mu), refractive index 1.518] is compression-bonded and fixed on the surface of an optical material 21 (e.g., crystal quartz, refractive index 2.117 at wavelength 200mu), after which air is introduced into the chamber to let the film 22 be compression-bonded and held on the surface of the optical material 21. The provision of the abovementioned reflection reducing film enables the surface reflection at a wavelength 200mu to be made nearly zero. In case light other than the wavelength 200mu is a target, it is only required to make the optical thickness of the film 22 at 1/4 the target wavelength. The abovementioned method is particularly effective for far infrared region where thick film is required as a reflection reducing film. |
