Focal length changeable lens system

Details Focal length changeable lens system Focal length changeable lens system

1987-12-22

1991-01-08

Sugarman, Scott J.

G02B 1508

Patent

active

049830260

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: 4148548 (1979-04-01), Thompson
patent: 4469396 (1984-09-01), Neil
patent: 4653872 (1987-03-01), Takahashi
patent: 4715693 (1987-12-01), Takasa et al.
patent: 4768868 (1988-09-01), Wakamiya et al.
David S. Grey, Athermalization of Optical Sysems, Journal of the Optical Society of America, Jun. 1945, pp. 542-546.

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