Zoom lenses

Details Zoom lenses Zoom lenses

1996-04-29

1998-02-10

Nelms, David C.

Optical: systems and elements

Lens

With variable magnification

359684, 359689, 359724, 359742, 359743, G02B 1515, G02B 1514, G02B 1300, G02B 308

Patent

active

057175250

ABSTRACT:
In order to reduce complexity and cost of fabrication of zoom lenses, the real image forming lens group module at the front of the zoom lens is replaced with a two-element group where one of the elements has a diffractive lens on a curved surface thereof instead of the usually cemented doublet of the front group, but with substantially the same aberrations as a front group with three elements, including a cemented doublet. Aberrations (chromatic and monochromatic) produced by the first and second groups remain corrected by the combination of these groups over the zoom range of the lens. A second group housing two-elements, one of which has a curved surface on which a diffractive lens is provided, may be also be used to replace the three-element second lens group and particularly the cemented doublet thereof. The two-element second group has substantially the same aberrations as the three-element group with a cemented doublet and the aberrations with zoom motion are corrected by the combination of the first and second groups even though each of them has two elements and a diffractive lens on a curved surface of one of their elements. The zoom lens thus maintains performance of zoom lenses having at least two additional elements and at lower cost than such zoom lenses with additional elements.

REFERENCES:
patent: 3044355 (1962-07-01), Cox et al.
patent: 4934795 (1990-06-01), Estelle
patent: 5013133 (1991-05-01), Buralli et al.
patent: 5268790 (1993-12-01), Chen
patent: 5301064 (1994-04-01), Sugi et al.

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