Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2001-09-24
2003-12-02
Schwartz, Jordan M. (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S703000, C359S704000, C359S823000
Reexamination Certificate
active
06657793
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens barrel suitable for use with a zoom lens system such as that proposed by the assignee of the present application in U.S. patent application No. 09/534,307 (Japanese Patent Application No. Hei 11-79572).
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 No. 09/534,307). 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.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a lens barrel suitable for use with a zoom lens system that includes the switching lens group as described above.
In order to achieve the above-mentioned object, a lens barrel having a zoom lens system is provided, the zoom lens system including a plurality of variable power lens groups which are movable in an optical axis direction for varying the focal length of the zoom lens system; wherein at least one of the variable power lens groups includes a switching lens group having two sub-lens groups, one of the sub-lens groups constituting a movable sub-lens group that is selectively positioned at one of two movement extremities, in the optical axis direction, with respect to the other of the sub-lens groups; the movable sub-lens group of the switching lens group is positioned at one of the movement extremities in a short-focal-length side zooming range from a short focal length extremity to an intermediate focal length, and at the other of the movement extremities in a long-focal-length side zooming range from the intermediate focal length to a long-focal-length extremity; zoom paths of the two sub-lens groups of the switching lens group and the other of the variable power lens groups are discontinuous at the intermediate focal length and are defined so that the zoom lens system forms an image on a predetermined image plane in accordance with a position of the movable sub-lens group; and the switching lens group is a focusing lens group which integrally advances and retreats in the optical axis direction regardless of the zooming range. The lens barrel includes a first sub-lens group frame for supporting one of the sub-lens groups; a second sub-lens group frame for supporting the other of the sub-lens groups; a switching lens group frame for supporting the first sub-lens group frame and the second sub-lens group frame in this order from object side in such a manner that allows the first and second sub-lens group frames to move in the optical axis direction; a lens shutter mechanism secured to the switching lens group frame on the image side of the second sub-lens group frame; and a focusing mechanism for making the second sub-lens group frame advance or retreat, depending on the object distance, with respect to a reference position provided by the lens shutter mechanism secured to the switching lens group frame. The first sub-lens group frame is moved along with the second sub-lens group frame in the optical axis direction in the long-focal-length zooming range and in the short-focal-length zooming range via the focusing mechanism.
In an embodiment, the first sub-lens group frame is maintained in a mutually close position with respect to the second sub-lens group frame in the long-focal-length zooming range and maintained in a mutually distant position with respect to the second sub-lens group frame in the short-focal-length zooming range; and the first sub-lens group frame is moved along integrally with the second sub-lens group frame by the focusing mechanism in the optical axis direction, in the mutually close position and in the mutually distant position.
In an embodiment, the switching lens group frame is moved so that the path of the lens shutter mechanism is not discontinuous between the short-focal-length zooming range and the long-focal-length zooming range, which extend on both sides of the intermediate focal length.
In an embodiment, a diaphragm mechanism is further secured to the switching lens group frame on the object side of the lens shutter mechanism.
According to another aspect of the present invention, a lens barrel having a zoom lens system, the zoom lens system including a plurality of variable power lens groups which are movable in an optical axis direction for varying the focal length of the zoom lens system, at least one of the variable power lens groups including a switching lens group having two sub-lens groups functioning optically in a mutually close position and in a mutually distant position, in the optical axis direction, the lens barrel includes a first sub-lens group frame for supporting one of the sub-lens groups; a second sub-lens group frame for supporting the other of the sub-lens groups; a switching lens group frame for supporting the first sub-lens group frame and the second sub-lens group frame in this order from object side in such a manner that allows the first and second sub-lens group frames to move in the optical axis direction; a lens shutter mechanism secured to the switching lens group frame on the image side of the second sub-lens group frame; and a focusing mechanism for making the second sub-lens group frame advance or retreat, depending on object distance, with respect to a reference position provided by the lens shutter mechanism secured to the switching lens group frame. The first sub-lens group frame is moved along with the second sub-lens group frame in the optical axis direction in the long-focal-length zooming range and in the short-focal-length zooming range via the focusing mechanism.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2000-293761 (filed on Sep. 27, 2000) which is expressly incorporated herein in its entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic drawing of a first embodiment of a zoom lens system having switching lens groups and the fundamental zoom path thereof, to which the present invention is applied.
FIG. 2
is a schematic drawing of a second embodiment of a zoom lens system having swi
Ishizuka Kazunori
Nomura Hiroshi
Sasaki Takamitsu
Takashima Maiko
Greenblum & Bernstein P.L.C.
Pentax Corporation
Schwartz Jordan M.
Stultz Jessica
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