Optical: systems and elements – Lens – With light limiting or controlling means
Patent
1998-04-30
1999-07-13
Epps, Georgia
Optical: systems and elements
Lens
With light limiting or controlling means
359753, 359761, 359793, G02B 900, G02B 1304, G02B 962, G02B 904
Patent
active
059234792
ABSTRACT:
The invention provides an inexpensive wide-angle lens system which is well corrected for longitudinal chromatic aberration and chromatic aberration of magnification without recourse to any anomalous dispersion glass while a long enough back focus is fully ensured. The wide-angle lens system comprises a front lens group comprising at least one positive lens and having negative power as a whole, an aperture stop 10, and a rear lens group comprising at least one negative lens and a diffractive optical element 11 having a diffractive surface of positive power, and having positive power as a whole, and satisfies 0.005<f/f.sub.DOE <0.03 where f is a focal length of the wide-angle lens system and f.sub.DOE is a focal length of the diffractive surface provided that f.sub.DOE is free of power of a substrate.
REFERENCES:
patent: 4189211 (1980-02-01), Taylor
patent: 5148314 (1992-09-01), Chen
patent: 5691847 (1997-11-01), Chen
patent: 5774279 (1998-06-01), Kiriki et al.
Epps Georgia
Lester Evelyn A.
Olympus Optical Co,. Ltd.
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