| 摘要 |
A bifocus lens system that is particularly suitable for being used in the portable machine, which not only can improve the incident angle but also can ensure miniaturization. The bifocus lens system comprises: a first lens group, a second lens group at wide angle side, and a second lens group at telephoto side, wherein the focal length can be changed by selectively arranging either of the first lens group and the second lens group on optical axis. A focal length of the first lens group is f1, a focal length of the second lens group at wide angle side is fw, and they satisfy the relation as: 1.0<f1/fw<1.4. A focal length of the second lens group at telephoto side is f2t, a total focal length of the whole lens groups at telephoto side is ft, they satisfy the relation: 0.8<|F2t/ft |<2.3
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