| 摘要 |
In a housed state, a magnetic fluid 4 is positioned in a groove 11 and spaced from the outer circumference of a lens barrel 10, so that a fluorochemical surface modification film of the outer circumference of the lens barrel 10 can be prevented from deteriorating at a position to confront the magnetic fluid 4 in the housed state. Therefore, the deterioration of the fluorochemical surface modification film of the outer circumference of the lens barrel 10 does not proceed earlier at a local region, so that the premature wetting of the outer circumference of the lens barrel 10 with the magnetic fluid 4 can be prevented to elongate the lifetime of a light shielding device 1.
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