| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive zoom lens for projection, which can maintain telecentricity on reduction side while attaining a wide angle of view, and further attain a reduced size with high brightness and high performance. SOLUTION: The projection zoom lens includes, in order from the enlargement side, a negative first group G1, positive second, third and fourth groups G2, G3 and G4, a negative fifth group G5, and a positive sixth group G6, in which when magnification is changed from a wide angle end to a telescopic end, the gird group G3, the fourth group G4 and the fifth group G4 are moved along the optical axis toward the enlargement side. The zoom lens satisfies condition expressions: (1) 0.9<¾f1¾/fw<1.7 and (2) 55<νd4, wherein f1 is the focal distance of the first group G1, fw is the focal distance of the whole system at the wide angle end, andνd4 is the Abbe's number of glass material constituting positive lenses contained in the fourth group G4. COPYRIGHT: (C)2009,JPO&INPIT
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