| 摘要 |
PROBLEM TO BE SOLVED: To provide a two-group zoom projection lens mounted in a projection type display device using a digital micro-mirror device (DVD) and achieving miniaturization, a wide viewing angle and high performance. SOLUTION: The two-group zoom projection lens is constituted by disposing a first lens group G<SB>1</SB>having negative refractive power and a second lens group G<SB>2</SB>having positive refractive power in order from an enlargement side. The second lens group G<SB>2</SB>is constituted by disposing a front group and a rear group in this order from the enlargement side, and the front group is constituted by disposing two or more positive lenses and one or more negative lenses in order from the enlargement side, and the rear group is constituted by disposing one or more negative lenses and two or more positive lenses in order from the enlargement side. Then, one of the negative lenses in the front group is constituted by turning its concave surface to the enlargement side, and one of the negative lenses in the rear group is constituted by turning its concave surface to a reduction side. The zoom projection lens satisfies conditional expressions (1): n<SB>2i</SB>>1.75, (2): 0.8<D<SB>2</SB>/f<SB>2</SB><1.2 and (3): 0.6<f<SB>w</SB>/f<SB>2</SB><0.8 äprovided that n<SB>2i</SB>: the refractive index of glass material composing the negative lens in the first lens group on a d-line, D<SB>2</SB>: the entire length of the second lens group, f<SB>2</SB>: the focal distance of the second lens group and f<SB>w</SB>: the focal distance of the lens entire system at a wide angle end}. COPYRIGHT: (C)2007,JPO&INPIT
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