| 摘要 |
PROBLEM TO BE SOLVED: To expand extent of light quantity control by an optical filter more than before. SOLUTION: The optical filter having extinction action comprises a filter base 1, a 1st optical film 4A which is formed on the filter base and has a 1st gradation region 6, and a 2nd optical film 4B which is formed so that at least a part thereof is superposed on the 1st optical film in an optical axis direction and which has a 2nd gradation region 9. Further, end positions and length of the 1st gradation region and the 2nd gradation region 9 are made different from each other to change a changing ratio of transmissivity in a gradation extent. COPYRIGHT: (C)2006,JPO&NCIPI
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