Optical: systems and elements – Lens – With multipart element
Patent
1998-10-08
1999-08-31
Epps, Georgia
Optical: systems and elements
Lens
With multipart element
359663, 359689, 359784, 359749, G02B 308
Patent
active
059461446
ABSTRACT:
A wide-angle lens has a three-group configuration in which a plastic aspherical lens is used in the first lens group on the enlargement side, and predetermined conditional expressions concerning focal lengths of individual lenses constituting the first lens group are satisfied, whereby image quality is restrained from deteriorating due to changes in temperature, and a telecentric characteristic is attained such that no vignetting occurs in marginal luminous fluxes, thus making various kinds of aberration favorable and allowing the cost to be cut down. The first lens group G.sub.1 disposed on the enlargement side has a three-lens configuration in which the first lens L.sub.1 on the enlargement side and the third lens L.sub.3 on the reduction side are constituted by a plastic aspherical lens having a negative refracting power and a plastic aspherical lens having a positive refracting power, respectively. Letting the focal length of the first lens group G.sub.1 be F.sub.1, the focal length of the whole lens system be F, the focal length of the first lens L.sub.1 be f.sub.A, and the focal length of the third lens L.sub.3 be f.sub.B, the conditional expression (1) of -7.5<F.sub.1 /F<-3.0 and the conditional expression (2) of -1.8<f.sub.A /f.sub.B <-0.5 are satisfied.
REFERENCES:
patent: 4936657 (1990-06-01), Tejima et al.
patent: 5600488 (1997-02-01), Minefuji et al.
patent: 5812326 (1998-09-01), Tamada
Epps Georgia
Fuji Photo Optical Co., Ltd.
Snider Ronald R.
Spector David N.
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