US 5,196,963 A · Zoom lens device

Abstract

A movable lens barrel contains a front lens group and a rear lens group and moves along the optical axis during zooming. The front lens group moves together with the movable lens barrel during zooming, and moves relative to the movable lens barrel along the optical axis during focussing. The rear lens group moves within and relative to the movable lens barrel during zooming. A deviation of the focussing position takes place due to backlash of the drive mechanism of the movable lens barrel. This focussing position deviation is eliminated by changing the position of the front lens group as set for focussing, or by changing the position of the rear lens group as set for zooming, respectively in accordance with the zooming direction. In order to determine the set position of the front lens group, two tables are provided corresponding respectively to the zooming direction. Each table stores a plurality of lens setting positions, an optimum one of which is selected in accordance with the focal length and subject distance. In order to adjust the position of the rear lens group, two types of cam surfaces are provided which are selectively used in accordance with the zooming direction. In another embodiment, a double cam ring is provided which is rotated during zooming to determine the position of the rear lens group. Only immediately after the zooming direction changes, the double cam ring is slid along the optical axis by a predetermined amount.

Claims28

Dependent claims

A zoom lens device having a movable lens barrel movable in first and second directions along an optical axis between a wide-angle end position and a telephoto end position, and a zoom lens optical system supported by said movable lens barrel, said zoom lens device comprising:

first signal generating means for generating a first signal representing the direction of movement of said movable lens barrel;
second signal generating means for generating a second signal representing the amount of movement of said movable lens barrel;
third signal generating means for generating a third signal representing a lens position of a focussing lens of said zoom lens optical system, in accordance with said first and second signals and a signal representing subject distance;
and
means for setting said focussing lens to said lens position in accordance with said third signal during focussing.

2 more elements

A zoom lens device having a first lens holder holding a first lens group, a second lens holder holding a second lens group, and a movable lens barrel containing said first and second lens holders in a manner allowing said first and second lens holders to be movable along an optical axis, said movable lens barrel being adapted to move in first and second directions along said optical axis between a wide-angle end position and a telephoto end position during zooming, and said first lens holder moving together with said movable lens barrel along said optical axis during zooming and moving along said optical axis within said movable barrel during focussing to be set to a position corresponding to subject distance, said zoom lens device comprising:

a cam follower for moving said second lens holder along said optical axis;
a first cam surface for guiding said cam follower when said movable lens barrel moves in said first direction and for moving said second lens holder along said optical axis within said movable lens barrel;
a second cam surface for guiding said cam follower when said movable lens barrel moves in said second direction and for moving said second lens holder along said optical axis within said movable lens barrel;
and
switching means for bringing said cam follower into contact with one of said first and second cam surfaces when said movable lens barrel moves into said first direction and into contact with the other of said first and second cam surfaces when said movable lens barrel moves in said second direction.

2 more elements

A zoom lens device having a first lens holder holding a first lens group, a second lens holder holding a second lens group, and a movable lens barrel containing said first and second lens holders for movement of said first and second lens holders along an optical axis, said movable lens barrel moving in first and second opposite directions along said optical axis between a wide-angle end position and a telephoto end position during zooming, and said first lens holder moving together with said movable lens barrel along said optical axis during zooming and moving along said optical axis within said movable barrel during focussing to a position corresponding to a subject distance, said zoom lens device comprising:

a cam follower pin mounted on said second lens holder;
a cam ring guiding said cam follower pin, said cam ring being housed rotatably and slidably within said movable lens barrel, and rotating during zooming to move said second lens holder along said optical axis;
first means for moving said cam ring along said optical axis by a predetermined distance only immediately after a change in direction of movement of said movable lens barrel;
and
means biasing said second lens holder toward said cam ring.

2 more elements

Dependencies are inferred from the claim text.

Zoom lens device

Life of this patent

Zoom lens device

Life of this patent

Abstract

Claims28