| 摘要 |
A lens barrel includes a helicoid ring provided with a helicoid; a retractable rotational ring which is guided by the helicoid to move along an optical axis while rotating, wherein the retractable rotational ring includes a pair of split retractable rotational rings which are supported so as to integrally rotate and to be relatively movable in the optical axis direction with respect to each other; first and second slide-engaging portions provided on one and the other of the pair of split retractable rotational rings, wherein the first and second slide-engaging portions are slidably engaged with the helicoid; and a biasing device which biases the pair of split retractable rotational rings in opposite directions in the optical axis direction so that the first and second slide-engaging portions are pressed in opposite directions against an opposing pair of first and second guide surfaces, respectively, of the helicoid of the helicoid ring.
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