| 摘要 |
a pair of light intensity adjusting blades (16, 17) for adjusting light intensity by opening/closing the optical path of an imaging optical system; a base body (26) having a transmittance hole (26a) as an optical path of the imaging optical system and movably supporting the light intensity adjusting blades; a rotary arm (27) having engagement pins (27b, 27b) slidably engaged with the light intensity adjusting blades and moving the light intensity adjusting blades parallel to each other; a drive motor (18) for rotating the rotary arm; and an auxiliary adjustment blade (23) moved in the same direction as at least one of the light intensity adjusting blades for opening/closing the transmittance hole. When the transmittance hole is being closed, the light intensity adjusting blade and the auxiliary adjustment blade moved in the same direction close the transmittance hole in such a manner that the superimposed area of these blades in the thickness direction is gradually reduced. When the transmittance hole is being opened, the light intensity adjusting blade and the auxiliary adjustment blade moved in the same direction open the transmittance hole in such a manner that the superimposed area of these blades in the thickness direction is gradually increased.
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