| 摘要 |
An interchangeable zoom lens assembly in which a part of the zooming lens groups is commonly used for focusing includes a stationary barrel to be mounted on a camera body, a cam ring fitted over or inside the stationary barrel, a manually operable zooming ring and a manually operable focusing ring. The cam ring is rotated relative to the stationary barrel in response to manual operation of the zooming ring and is moved relative to the stationary barrel in the direction of the optical axis of the zoom lens in response to manual operation of the focusing ring. A transmission mechanism moves the zooming lens groups for zooming in response to the rotation of the cam ring and to move the part of the zooming lens groups for focusing while keeping the remaining part of the zooming lens groups at rest in response to the movement of the cam ring in the direction of the optical axis. The focusing ring is located close to the rear end of the lens assembly and the lens assembly may further include a mechanism for automatically operating the focusing ring in response to a power drive from the camera body for automatic focusing or for power focusing.
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