| 摘要 |
PURPOSE:To obtain a dielectric filter which is less deteriorated with lapse of time by laminating dielectric materials having a high refractive index and low refractive index in multiple layers on substrates and heating the layers in a moist atmosphere. CONSTITUTION:Titanium dioxide and silicon dioxide are provided in a disk-shaped crucible 32 contg. a vapor deposition source 30 in a vacuum vessel 20 of an electron beam vapor deposition device and the crucible is rotated to a position where the radiation current from an electron gun 34 arrives so that said current comes to the crucible. The film thickness control of the respective layers of the dielectric materials is executed by placing a monitor substrate 12 in the position 11 and detecting the extreme value by a change in the transmissivity of rays from a light source, by which the thicknesses of the films formed on the substrates 22, 22... to be made into products on a dome 21 are controlled. Namely, the white light from the light source 31 passes the substrate 12 on which the thin film is deposited by evaporation. This light passes a single color filter 35 of, for example, lambda0 wavelength and arrives at a photodetecting element 32. The resultant change in the quantity of light is converted to a signal and the change in the transmissivity is displayed and recorded. The optical films are controlled by detecting the extreme value corresponding to lambda0/4.
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