| 摘要 |
PURPOSE: A supporting structure for supporting a rotatable ring is provided to support a rotatable ring therein which rotates while advancing or retracting between an operating state and a non-operating state, wherein the support structure has a function of removing backlash and play in the rotatable ring, specifically in the operating state thereof. CONSTITUTION: The zoom lens is provided in the stationary barrel(22) with a helicoid ring. The helicoid ring is provided on an outer peripheral surface thereof with a male helicoid(18a) and a set of three rotational sliding projections(18b). The male helicoid(18a) is engaged with the female helicoid(22a), and the set of three rotational sliding projections(18b) are engaged in the set of three inclined grooves or the set of three rotational sliding grooves(22d), respectively. The helicoid ring is provided on threads of the male helicoid(18a) with an annular gear(18c) which is in mesh with the zoom gear(28). Therefore, when a rotation of the zoom gear(28) is transferred to the annular gear(18c), the helicoid ring moves forward or rearward in the optical axis direction while rotating about the lens barrel axis Z0 within a predetermined range in which the male helicoid(18a) remains in mesh with the female helicoid(22a). A forward movement of the helicoid ring beyond a predetermined point with respect to the stationary barrel(22) causes the male helicoid(18a) to be disengaged from the female helicoid(22a) so that the helicoid ring rotates about the lens barrel axis Z0 without moving in the optical axis direction relative to the stationary barrel(22) by engagement of the set of three rotational sliding projections(18b) with the set of three rotational sliding grooves(22d).
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