Focal length changeable lens system

Details Focal length changeable lens system Focal length changeable lens system

1990-06-11

1992-02-04

Sugarman, Scott J.

Optical: systems and elements

Lens

Selective magnification by exchanging or adding a lens...

359764, G02B 1508, G02B 960

Patent

active

050863550

ABSTRACT:
The present invention provides a focal length changeable lens system which comprises a master lens group of a positive refractive power having at least one negative lens element made of a synthetic resin material; and a rear conversion lens group of a negative refractive power retractably arranged on the image side of the master lens group and having at least one positive lens element made of a synthetic resin material, in order to well compensate the change of back focal length of the lens system due to the change in temperature thereof without increasing the cost of the lens system.

REFERENCES:
patent: 3502393 (1970-03-01), Kazamaki et al.
patent: 3502394 (1970-03-01), Kobayashi
patent: 4429958 (1984-02-01), Yamaguchi
patent: 4576448 (1986-03-01), Ikari
patent: 4653872 (1987-03-01), Takahashi
patent: 4715693 (1987-12-01), Takase et al.
patent: 4768868 (1988-09-01), Wakamiya et al.
patent: 4770508 (1988-09-01), Yamada et al.
Gray, D. S., "Athermalization of Optical Systems", Journal of the Optical Society of Amer. vol. 38, No. 8, Jun. 1948, pp. 542-546.

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