| 摘要 |
PROBLEM TO BE SOLVED: To provide a projection zoom lens capable of ensuring a wide view angle, an appropriate amount of back focus, high image quality, and a variable power ratio as high as about 1.3 to 2 times, and to provide a projection type display apparatus. SOLUTION: The projection zoom lens includes, in order from the enlargement side, first group G<SB>1</SB>with negative refractive power, second to fourth groups G<SB>2</SB>to G<SB>4</SB>with positive refractive power, a fifth group G<SB>5</SB>with negative refractive power, and a sixth group G<SB>6</SB>with positive refractive power. Subsequent to them, a cover glass 2 and DMD1 are disposed. When power is changed, four lens groups, namely the second to fifth groups G<SB>2</SB>to G<SB>5</SB>, are moved to have a zoom function. These four lens groups are located on the enlargement side at the tele-photo end rather than at the wide-angle end. The zoom lens satisfies the following conditional formulas (1) to (5): 0.10<¾M3¾×f3<0.50 (1), 0.20<¾M4¾×f4<1.00 (2),νd>55(3), Nd>1.70 (4), andνd>40 (5), wherein Mi is an amount of zoom movement from the wide-angle end of an i group to its tele-photo-end, fi is the focal distance of the i group,νd is the Abbe's number of the fourth group G<SB>4</SB>relative to a line (d), and Nd is the refractive index of the second group G<SB>2</SB>relative to the line (d). COPYRIGHT: (C)2008,JPO&INPIT
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