Patent ID: 7436602

Claim:
A lens barrel which accommodates a lens system, comprising: a helicoid ring provided with a helicoid on one of an inner and outer circumferential surface thereof; a retractable rotational ring which is guided by said helicoid of said helicoid ring to move along an optical axis of said lens system while rotating, wherein said 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 said optical axis direction with respect to each other; a first slide-engaging portion and a second slide-engaging portion provided on one and the other of said pair of split retractable rotational rings, wherein said first and second slide-engaging portions are slidably engaged with said helicoid of said helicoid ring; and a biasing device which biases said pair of split retractable rotational rings in opposite directions in said optical axis direction so that said first and second slide-engaging portions are pressed in opposite directions against an opposing pair of first and second guide surfaces, respectively, of said helicoid of said helicoid ring.