Vari-focal lens system

Details Vari-focal lens system Vari-focal lens system

1994-07-01

1996-10-29

Epps, Georgia Y.

Optical: systems and elements

Lens

With variable magnification

359684, 359686, G02B 1514

Patent

active

055702333

ABSTRACT:
A vari-focal lens system comprising, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power and a fourth lens unit having a positive refractive power; and configured so as to be set at a focal length at a telephoto position thereof from that at a wide-angle position thereof by moving the first lens unit monotonically toward the object side, displacing the second lens unit monotonically toward the image side, setting the third lens unit at a location on the object side of its original setting at the wide-angle position and moving the fourth lens unit from a location thereof to focus the vari-focal lens system on an object effectively located at infinite distance so as to widen an airspace reserved between the third lens unit and the fourth lens unit as compared to the airspace at the wide-angle position. The vari-focal lens system can be focused by moving the fourth lens unit.

REFERENCES:
patent: 5032013 (1991-07-01), Shibayama
patent: 5134524 (1992-07-01), Hamano
patent: 5189558 (1993-02-01), Ishii et al.
patent: 5191476 (1993-03-01), Sato

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