Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
1999-09-08
2001-03-20
Mack, Ricky (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S704000
Reexamination Certificate
active
06204977
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens barrel having a plurality of advanceable and retreatable frame members for supporting photography lenses.
2. Description of the Related Art
In recent years, as zoom lenses have become increasingly longer in focal length, lens barrels have had to accommodate increasing amounts of advancing and retreating of lens groups. A zoom lens barrel proposed under such circumstances and disclosed in the Japanese Unexamined Patent Publication No. 2-89012 is adapted to drive first and second lens group supporting frames for larger amounts of advancing and retreating movements thereof by rotating a drive ring. Further, a first cam groove for moving the first lens group supporting frame back and forth and a second cam groove for moving a drive cam back and forth are provided in the drive ring. The second lens group supporting frame is driven through the drive cam to move back and forth.
However, in the zoom lens barrel disclosed in the Japanese Unexamined Patent Publication No. 2-89012, the first lens group supporting frame is directly driven by the drive ring to move back and forth, while the second lens group supporting frame is driven through the drive cam by the drive ring to move back and forth. Therefore, the advancing and retreating movements of the drive cam are about as much as those of movement of the first lens group supporting frame. Consequently, it is difficult to obtain large amounts of the lens groups. Further, this zoom lens barrel is not necessarily advantageous in the accuracy of the relative position between the first and second lens group supporting frames owing to the presence of the drive cam having a large lift amount.
SUMMARY OF THE INVENTION
The present invention is intended to solve the aforementioned problems. Accordingly, an object of the present invention is to provide a lens barrel which has a plurality of advanceable and retreatable frame members for supporting photographing lenses, is reduced in size, has frame members which have large amounts of advancing and retreating movements and is increased in focal length.
To achieve the foregoing object, according to an aspect of the present invention, there is provided a lens barrel that has a photography lens and comprises a first frame which has a straight groove in parallel with an optical axis of the lens and which also has a first oblique groove inclined with respect to the straight groove. The lens barrel further comprises a second frame which has a first cam-follower engaging with the first oblique groove of the first frame and which also has a second cam-follower. The lens barrel further comprises a third frame, which has a second oblique groove inclined with respect to the optical axis of the lens and engaging with the second cam-follower, and which also has a follower engaging with the straight groove of the first frame. The first frame is operative to transmit a driving force directly to the second and third frames. Thus, the second frame moves rectilinearly and the third frame moves rectilinearly with respect to the second frame.
REFERENCES:
patent: 5287137 (1994-02-01), Hara et al.
patent: 6018426 (2000-01-01), Funuhashi
patent: 6115190 (2000-09-01), Harai
patent: 2-89012 (1990-03-01), None
Mack Ricky
Olympus Optical Co,. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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