Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2001-09-24
2004-09-21
Mai, Huy (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S703000, C359S706000
Reexamination Certificate
active
06795251
ABSTRACT:
BACKGROUND OF THE INVENTION
The present application relates to the following U.S. Patent Applications, all filed concurrently herewith on Sep. 24, 2001, and all of which are expressly incorporated herein by reference in their entireties: “ZOOM LENS MECHANISM” having attorney U.S. patent application Ser. No. 09/960,309, “LENS DRIVE MECHANISM” having application Ser. No. 09/960,382, “ECCENTRICITY-PREVENTION MECHANISM FOR A PAIR OF LENS-SUPPORTING RINGS” having application Ser. No. 09/960.515, “REDUCTION GEAR MECHANISM” having application Ser. No. 09/960.52 1, “RING MEMBER SHIFT MECHANISM AND LENS GROUP SHIFT MECHANISM” having application Ser. No. 09/960,518, “LENS BARREL” having application Ser. No. 09/961,231, “LENS BARREL” having application Ser. No. 09/960,516, “LENS BARREL” having application Ser. No. 09/961,233, “ZOOM LENS BARREL” having application Ser. No. 09/961,185, and “LENS BARREL” having application Ser. No. 09/961,232, each naming as inventors Hiroshi NOMURA et al.; and “LENS DRIVE CONTROL APPARATUS FOR ZOOM LENS SYSTEM HAVING A SWITCHING LENS GROUP” having application Ser. No. 09/961,186 and naming as inventor Norio NUMAKO.
1. Field of the Invention
The present invention relates to lens drive mechanisms, and more particularly, to lens drive mechanisms for alternatively moving two sub-lens groups toward and away from each other or moving the two sub-lens groups integrally.
2. Description of the Related Art
In a zoom lens system of the prior art, there are contradictory demands for a high zoom ratio and miniaturization. For example, in a two-lens-group zoom lens system which can be miniaturized, if the paths of the lens groups thereof (hereinafter, zoom paths) are determined (i.e., solutions for zoom paths) so that the zoom ratio becomes high, interference of the lens groups occurs on the telephoto side, or interference of a lens group and the image plane occurs on the wide-angle side. On the other hand, in a three-lens-group zoom lens system, the zoom ratio thereof can be made higher than that of a two-lens-group zoom lens system; however, miniaturization is difficult. Furthermore, if an attempt is made to obtain a higher zoom ratio, and if the power of these three lens groups is determined accordingly, precision on the operations of the zoom lens system cannot be obtained due to the mechanical structure thereof.
The assignee of the present application has proposed an unprecedented zoom lens system that meets the contradictory demands of high zoom ratio and miniaturization (U.S. patent application Ser. No. 09/534,307, Japanese Patent Application No. Hei 11-79572). This zoom lens system has the following characteristics: it includes a plurality of movable lens groups for varying the focal length; at least one of the lens groups is a switching lens group which includes two sub-lens groups, one of the sub-lens groups being a movable sub-lens group that can be selectively positioned at either one movement extremities in the optical axis direction with respect to the other sub-lens group; the movable sub-lens group of the switching lens group is positioned at an extremity of a short-focal-length zooming range, from the short focal length extremity to an intermediate focal length, and at the opposite extremity of a long-focal-length zooming range, from the intermediate focal length to a long focal length extremity; and zoom paths of the switching lens group and the other lens groups are discontinuous at the intermediate focal length and are defined to focus on a predetermined image plane corresponding to the position of the movable sub-lens group. There may be one or more intermediate focal lengths.
In such a zoom lens system, while the two sub-lens groups (i.e., the switching lens group) are moved to a mutually close position and mutually distant position during the switching between the short-focal-length side zooming range and the long-focal-length side zooming range, the two sub-lens groups can also be moved integrally regardless of zooming range to carry out focusing. In the case where the two sub-lens groups are alternatively moved toward and away from each other (i.e., to the mutually close position or mutually distant position) or moved integrally, if the sub-lens group frames, each of which supports one of the sub-lens groups, are individually guided, guide mechanisms for guiding the sub-lens group frames may interfere with each other when the sub-lens group frames are moved integrally. As a result, smooth guiding may be interrupted.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a simple lens drive mechanism that ensures smooth movements of two sub-lens groups toward and away from each other as well as smooth integral movements of the two sub-lens groups without causing interference between guiding elements.
In order to achieve the above object, a lens drive mechanism is provided, including a first sub-lens group frame and a second sub-lens group frame for supporting a first sub-lens group and a second sub-lens group, respectively, the sub-lens groups functioning optically in a mutually close position and in a mutually distant position, with respect to the optical axis thereof; a support frame for supporting the first sub-lens group frame and the second sub-lens group frame; a first linear guide mechanism provided between the first sub-lens group frame and the support frame, the first linear guide mechanism guiding the first sub-lens group frame while permitting movement thereof in the optical axis direction and preventing rotation thereof about the optical axis; a second linear guide mechanism provided between the second sub-lens group frame and the support frame, the second linear guide mechanism guiding the second sub-lens group frame while limiting rotation of the second sub-lens group frame at two extremities of rotation thereof over a predetermined angle, and linearly guiding the second sub-lens group frame in the optical axis direction at the two extremities of rotation; a lens frame shift mechanism for causing the first sub-lens group frame and the second sub-lens group frame to move to the mutually close position and the mutually distant position, in accordance with rotation of the second sub-lens group frame between the two extremities of rotation; and a linear displacement mechanism which integrally moves the first sub-lens group frame and the second sub-lens group frame in the optical axis direction, in the mutually close position and in the mutually distant position. A linear guide clearance of the first linear guide mechanism is larger than a linear guide clearance of the second linear guide mechanism.
In an embodiment, the first and second sub-lens groups form one of a plurality of variable lens groups for varying a focal length thereof, and the first and second sub-lens groups constitute a focusing lens group which advances or retreats in the optical axis direction while maintaining the mutually close position or at the mutually distant position, regardless of the focal length.
Preferably, the lens frame shift mechanism includes a cam surface and a follower provided on opposed surfaces of the first sub-lens group frame and the second sub-lens group frame, the cam surface and the follower being arranged so as to move the first sub-lens group frame and the second sub-lens group frame to the mutually close position and the mutually distant position as the second sub-lens group frame is rotated.
Preferably, the lens drive mechanism further includes a positioning recess formed as a continuation of the opposite ends of the cam surface, the positioning recess defining relative positions of the first sub-lens group frame and the second sub-lens group frame in the optical axis direction and in the circumferential direction by engaging with the follower when the first sub-lens group frame and the second sub-lens group frame are in the mutually close position and in the mutually distant position; and a biasing member for biasing the first and second sub-lens group frames to bring the positioning recess and the fol
Ishizuka Kazunori
Nomura Hiroshi
Sasaki Takamitsu
Takashima Maiko
Greenblum & Bernstein P.L.C.
Mai Huy
PENTAX Corporation
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