1. Field of the Invention
The present invention generally relates to a zoom lens for use in a photographic camera, video camera or the like, and more particularly, to a lens barrel of a zoom lens of the type in which at least two lens groups can move in a linked body at the time of zooming.
2. Description of the Prior Art
FIG. 1 depicts a well known zoom lens having four lens groups, in which the first lens group L1 and the fourth lens group L4 move in a linked body.
Generally speaking, in a zoom lens having four lens groups, the first lens group L1 is greater in outer diameter than other three lens groups L2, L3 and L4. Accordingly, in consideration of the compactness of a lens barrel of the zoom lens, a stationary cam ring 1 fixedly mounted on the camera body and a movable cam ring 2 rotatable about the stationary cam ring 1 are so located behind the first lens group L1 as to encircle the second, third and fourth lens groups L2, L3 and L4. In this kind of zoom lens, it is necessary to connect the first and fourth lens groups L1 and L4 to each other by any suitable means. Conventionally, a lens holder 7 for holding the fourth lens group L4 is extended towards and connected to a lens holder 8 for holding the first lens group L1 through openings formed in lens holders 5 and 6 for holding the second and third lens groups L2 and L3, respectively.
However, extended portions 7' of the lens holder 7 for the fourth lens group L4 are required to pass between the first lens group L1 and the front ends of the stationary cam ring 1 and the movable cam ring 2. Accordingly, the stationary cam ring 1 and the movable cam ring 2 are restricted in length in the direction of the optical axis by the thickness of the extended portions 7' of the lens holder 7. In other words, lens holders 5 and 6 for securely holding the second and third lens groups L2 and L3 are restricted in their traveling length due to the restriction of the length of the stationary cam ring 1 and the movable cam ring 2. This is at a disadvantage when the traveling length of each lens group is relatively large. When a certain large traveling length is needed by all means, it is necessary to render the stationary cam ring 1 and the movable cam ring 2 to be greater in outer diameter than the first lens group L1. This is out of harmony with a compact lens barrel design goal.
USPTO Backgrounds
USPTO Backgrounds