| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens for projection which is suitable for a projector device using a DMD, which has high performance, which is compact, and which can achieve a wide angle of view and a high variable power ratio, without using a plurality of aspheric lenses. SOLUTION: The zoom lens for projection includes a first group G<SB>1</SB>having negative refractive power, a second group G<SB>2</SB>having positive refractive power, a third group G<SB>3</SB>having positive refractive power and a fourth group G<SB>4</SB>having positive or negative refractive power, in order from a magnification side. At variable power from a wide-angle end to a telephoto end, the second group G<SB>2</SB>, the third group G<SB>3</SB>and the fourth group G<SB>4</SB>are moved to the magnification side, and the first group G<SB>1</SB>is slightly moved to a reduction side. A following conditional expression (1) is satisfied. (1) 0.95<frw/frt<1.05: Where frw is a composite focal length of the second group G<SB>2</SB>, the third group G<SB>3</SB>and the fourth group G<SB>4</SB>at the wide-angle end, and frt is a composite focal length of the second group G<SB>2</SB>, the third group G<SB>3</SB>and the fourth group G<SB>4</SB>at the telephoto end. COPYRIGHT: (C)2008,JPO&INPIT
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