Zoom lens

Details Zoom lens Zoom lens

2001-01-23

2001-11-13

Lester, Evelyn A (Department: 2873)

Optical: systems and elements

Lens

With variable magnification

C359S715000, C359S740000

Reexamination Certificate

active

06317272

ABSTRACT:

BACKGROUND OF THE INVENTION
Recently, the image detector size in new video cameras being sold has been decreasing from about ⅓ of an inch in linear dimension to about ¼ of an inch in linear dimension. This has placed demands on the development of new zoom lenses for such cameras which are simple in design and yet have a sufficiently high optical performance. As such a zoom lens, rear-focus type lenses have been known in which the entire zoom lens is formed of four lens groups, with the first lens group and the third lens group being fixed in position. Power is varied by moving the second lens group along the optical axis and the image plane is made to remain at a fixed location as the power is varied by moving the fourth lens group along the optical axis. Moreover, lenses with a high variable power ratio, as described in Japanese Laid Open Patent Applications Nos. H8-005916 and H11-194269 have been known for use as zoom lenses for video cameras.
More recently, handy electronic still cameras, so-called digital cameras, have rapidly become popular, and zoom lenses of high variable power ratio have also been used in such electronic still cameras. However, the required degree of compactness is different among video cameras and digital cameras. Therefore, the overall length of zoom lenses for these two applications is also different. Namely, the size of the digital camera is much smaller, as it is desired that such cameras be capable of being carried in a breast pocket of a garment. Thus, the overall length of a zoom lens for a digital camera must be very small. Indeed, the desired overall length of a zoom lens for a digital camera is so small that none of the above-discussed prior art zoom lenses used in video cameras is sufficiently small. Therefore a zoom lens having a shorter overall length has been desired.
In digital cameras, the resolution required of the zoom lens employed has rapidly increased as the pixel size has decreased in linear dimension to about 3-4 &mgr;m. This has made the axial chromatic aberration at the telephoto end increases to the point that it is no longer of little concern.
BRIEF SUMMARY OF THE INVENTION
A first object of the present invention is to provide a zoom lens having a very short overall length so that the zoom lens can be used with a digital camera, while maintaining a high variable power ratio and excellent optical imaging properties. More particularly, a second object of the present invention is to provide a zoom lens having reduced axial chromatic aberration at the telephoto end.


REFERENCES:
patent: 5235466 (1993-08-01), Ono et al.
patent: 5267082 (1993-11-01), Ono et al.
patent: 5296696 (1994-03-01), Mihara
patent: 5313331 (1994-05-01), Mihara
patent: 5424869 (1995-06-01), Nanjo
patent: 5546231 (1996-08-01), Sato
patent: 5583698 (1996-12-01), Yamada et al.
patent: 5583699 (1996-12-01), Nakayama
patent: 5719708 (1998-02-01), Nagaoka
patent: 5798872 (1998-08-01), Uzawa
patent: 5940221 (1999-08-01), Okayama et al.
patent: 5963378 (1999-10-01), Tochigi et al.
patent: 5969879 (1999-10-01), Park
patent: 6101043 (2000-08-01), Kohno et al.
patent: 6104547 (2000-08-01), Nanba
patent: 6124983 (2000-09-01), Yahagi et al.
patent: 6166864 (2000-12-01), Horiuchi
patent: 6226130 (2001-05-01), Mukaiya et al.
patent: 8-5916 (1996-01-01), None
patent: 11-194269 (1999-07-01), None

Affiliated with

Also associated with

Rating

Zoom lens does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Zoom lens, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Zoom lens will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2606779