| 摘要 |
PROBLEM TO BE SOLVED: To solve such a problem that when a raw material to be evaporated is preliminarily heated, a deposited material attached to a shutter drops down on the raw material and causes fluctuations of film-forming speed and unevenness of the raw material during film-forming of a optical multilayer film filter for DWDM having a large number of layers and degrades the characteristic of the optical multilayer film filter. SOLUTION: Plural sheets of shutters 10 covering the raw material 20 are disposed, switched and used in the way of film-forming of the optical multilayer film filter and thereby, it is prevented that an evaporated material is excessively attached to the shutter and drops down on the raw material.
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