| 摘要 |
PROBLEM TO BE SOLVED: To provide an ND filter that can decrease influences in degradation of resolution due to diffraction upon narrowing an aperture, and also to provide a luminous energy adjusting mechanism, a lens body tube and an imaging device having the ND filter. SOLUTION: The ND filter 13 has a filter portion 13A where a light flux passes in a triangular form having a first vertex A in a farther side from the optical axis OL within the plane. When virtual points a1 to a5 are determined by dividing a virtual line 21 into fractions, the line 21 connecting the first vertex A and a point D which halves the end side 16 of the filter portion 13A, the filter portion 13A comprises regions having constant optical densities along curved lines e1 to e5 that connect the respective virtual points a1 to a5 and the second and the third vertexes B, C of the triangle. COPYRIGHT: (C)2008,JPO&INPIT
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