1979-04-18
1982-01-12
Clark, Conrad J.
350458, G02B 1304, G02B 964
Patent
active
043102220
ABSTRACT:
The present invention relates to a retro-focus type wide angle lens which is compact despite its remarkably large field of view and well compensated for various aberrations.
This lens system consists of the first divergent lens group and the second convergent lens group in sequence from the side of the object, whereby the first divergent group consists of a plural number of meniscus lenses convex to the object in such a manner that the distortion is compensated for and a compact lens system is realized by forming the object side surface of the substantially zero first order power lens in the meniscus lenses non spherical. The meniscus lens with non-spherical surface is formed from plastic material, resulting in an inexpensive and light retro-focus type wide angle lens.
Further, the second convergent lens group is divided into two lens groups with a diaphragm as boundary, whereby in the object side lens group a meniscus lens concave to the object and a biconvex lens are arranged in sequence from the diaphragm to the object side so as to form an air lens having a divergent effect between both lenses, while in the image plane side lens group a lens concave to the image is arranged so as to eliminate the astigmatism and the spherical aberration.
REFERENCES:
patent: 3583791 (1971-06-01), Mori
patent: 3966306 (1976-06-01), Okudaira
patent: 4111558 (1978-09-01), Ikemori
patent: 4116536 (1978-09-01), Moscovich
Canon Kabushiki Kaisha
Clark Conrad J.
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