Zoom lens unit and image pickup device

Abstract

There is provided a zoom lens unit excellent in shock resistance and space-saving. Second, third lens holders 29, 30 have shaft holes, into which shafts 27, 28 are inserted, so as to be movable in an optical axis direction. By first, second helical springs 31, 32 fitted to the shafts 27, 28, the second lens holder 29 is biased to a wall member 18 provided on a subject side, and the third lens holder 30 is biased to a wall member 19 provided on an image pickup element 12 side. As the power is turned off, the second lens holder 29 moves toward the subject side and, upon contact with the wall member 18, is stopped, while the third lens holder 30 moves toward the image pickup element 12 side and, upon contact with the wall member 19, is stopped.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not intended to limit the present invention, and wherein:

FIG. 1 is a perspective view of an image pickup device including a zoom lens unit of the present invention;

FIG. 2 is a perspective view in which an image pickup element is omitted from the state of FIG. 1, as viewed in another direction;

FIGS. 3( a) and 3(b) are schematic views of a drive mechanism for moving a second lens holder and a third lens holder of FIG. 1 in the optical axis direction;

FIG. 4 is a view showing a state that the second lens holder has been moved toward the image pickup element side;

FIG. 5 is a view showing a state that the third lens holder has been moved toward the subject side;

FIG. 6 is a view showing a positional relationship among a plane of the second lens holder, a first nut and a wall member;

FIG. 7 is a view showing a positional relationship among a plane of the third lens holder, a second nut and a wall member;

FIG. 8 is a view showing a makeup of a helical spring different from those of FIGS. 6 and 7; and

FIG. 9 is a perspective view of a zoom lens unit of a prior art.

Claims

1. A zoom lens unit comprising: a second lens group and a third lens group arrayed concentrically and in series in this order as from a subject side;a first shaft positioned so as to extend along an optical axis direction of the second lens group and the third lens group;a second shaft positioned so as to extend along the optical axis direction;a first wall member and a second wall member for supporting both ends of each of the first shaft and the second shaft, respectively;a second lens holder on which the second lens group is mounted and which has a shaft hole for insertion of the first shaft therethrough, the second lens holder being movable in the optical axis direction under guidance of the first shaft;a third lens holder on which the third lens group is mounted and which has a shaft hole for insertion of the second shaft therethrough, the third lens holder being movable in the optical axis direction under guidance of the second shaft; anda biasing part for biasing the second lens holder and the third lens holder in such directions as the second and third lens holders are distanced from each other.

2. The zoom lens unit as claimed in claim 1, further comprising a driving part for driving the second lens holder and the third lens holder in the optical axis direction against biasing force of the biasing part or using biasing force of the biasing part, and for, in a power-off state, moving the second lens holder by using biasing force of the biasing part until the second lens holder reaches either one of the first wall member and the second wall member while moving the third lens holder until the third lens holder reaches the other of the first wall member and the second wall member.

3. The zoom lens unit as claimed in claim 1, wherein the biasing part is composed of at least two biasing parts, first biasing part and second biasing part, and whereinthe first biasing part biases the second lens holder from an image pickup side toward a subject side, andthe second biasing part biases the third lens holder from the subject side toward the image pickup side.

4. The zoom lens unit as claimed in claim 1, wherein the biasing part is an elastic body.

5. The zoom lens unit as claimed in claim 4, wherein the elastic body is a helical spring.

6. The zoom lens unit as claimed in claim 5, further comprising a shaft positioned so as to extend along the optical axis direction, whereinthe helical spring is wound around the shaft.

7. The zoom lens unit as claimed in claim 6, wherein the shaft comprises the first shaft for guiding the second lens holder in the optical axis direction and the second shaft for guiding the third lens holder in the optical axis direction.

8. An image pickup device which includes the zoom lens unit as defined in claim 1.