| 摘要 |
PURPOSE:To obtain a high reflectivity over a wide band by constituting high refractive index layers of zinc sulfide layers and low refractive index layers of magnesium fluoride layers. CONSTITUTION:This mirror is constituted of the zinc sulfide layers 3a, 4a and magnesium fluoride layers 3b, 4b having small absorption in a 3-5mum wavelength range. A decrease in the reflectivity by absorption is, therefore, minimized. The high reflectivity is thereby obtd. over the wide band of the 3-5mum wavelength range. The high transmissivity to radio waves is obtd. and the sepn. of the IR rays and the radio waves of the wavelength range by reflection and transmission is permitted by using a semiconductor or dielectric belt of which the product of the square root of the dielectric constant and the thickness is integer times of 1/2 the space wavelength of the radio waves to be transmitted as a substrate 1.
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