| 摘要 |
PROBLEM TO BE SOLVED: To provide an ND filter which can have its transmissivity selected higher than before, makes its manufacturing method easy, and has nearly uniform transmissivity in the visible ray region. SOLUTION: The ND filter of thin-film constitution which controls the quantity of transmitted light is constituted by laminating at least a metal film 3 made of Al or Al alloy and Nb films 5 and 7 on a light-transmissive base material 1 across dielectric films 4, 6, and 8. COPYRIGHT: (C)2003,JPO
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