Zoom lens and projector employing zoom lens

Details Zoom lens and projector employing zoom lens Zoom lens and projector employing zoom lens

2007-07-31

2008-09-09

Lester, Evelyn A. (Department: 2873)

Optical: systems and elements

Lens

With variable magnification

C359S680000, C359S683000, C359S686000, C359S689000, C359S691000, C359S684000

Reexamination Certificate

active

07423812

ABSTRACT:
In a thin projector for projecting an image from a light valve such as a DMD, a compact zoom lens comprises, in order, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens-group having a negative refractive power, and a fourth lens group having a positive refractive power. The fourth lens group is fixed while the focal length is being changed. The first and second lens group are movable on an optical axis in a direction from the enlarging side towards the reducing side over a range from a wide angle end to an intermediate range, and are movable on the optical axis in a direction from the reducing side towards the enlarging side over a range from the intermediate range to a telephoto end. The third lens group moves on the optical axis in a direction from the reducing side to the enlarging side over a range from the wide angle end to the telephoto end, whereby the focal length of the whole lens system of the zoom lens is changed.

REFERENCES:
patent: 6643072 (2003-11-01), Mihara
patent: 6888683 (2005-05-01), Itoh
patent: 6930839 (2005-08-01), Hagimori et al.
patent: 7304804 (2007-12-01), Hagimori et al.
patent: 2004/0051962 (2004-03-01), Mihara
patent: 2004-271668 (2004-09-01), None

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