Optical: systems and elements – Lens – With variable magnification
Patent
1991-08-02
1992-10-27
Howell, Janice A.
Optical: systems and elements
Lens
With variable magnification
359749, 359689, G02B 1514
Patent
active
051594935
ABSTRACT:
Described herein is a retrofocus type wide angle lens system composed of a front group with a negative power and a rear group with a positive power, in which the front group is divided into a fixed group starting with a negative meniscus lens having a convex surface on the object side and terminating with a negative lens element having a concave surface on the image-forming side, and a corrective group starting with a positive lens element having a convex surface on the object side. The fixed group which is constituted by larger and heavier lens elements is held stationary relative to an image forming plane, while the corrective group of smaller and light-weight lens elements is movable in the direction of the optical axis concurrently with the rear group to vary the width of the air space between the respective groups at the time of focusing, thereby effectively correcting various aberrations which would otherwise occur in a conspicuous degree in infinite to near distance focusing.
REFERENCES:
patent: 4266860 (1981-05-01), Hayashi
patent: 4303311 (1981-12-01), Nakamura
patent: 4838666 (1989-06-01), Shiraishi
patent: 5000550 (1991-03-01), Takahashi et al.
Beyer James
Fuji Photo Optical Co., Ltd.
Howell Janice A.
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