发明名称 Wide angle zoom lens of long back focal distance
摘要 A wide angle zoom lens of increased back focal distance comprising, from front to rear, a first lens unit of negative power, a second lens unit of positive power, and a third lens unit of positive power, the first and second lens units axially moving in differential relation to effect zooming, while holding the third lens unit stationary, and satisfying the following conditions: 2.0</=¦f1/fW¦</=3.2 0.33</=¦f1/f2¦</=0.8 where f1 and f2 are the focal lengths of the first and second lens units, respectively, and fW is the shortest focal length of the entire lens system.
申请公布号 US4838666(A) 申请公布日期 1989.06.13
申请号 US19870125571 申请日期 1987.11.25
申请人 CANON KABUSHIKI KAISHA 发明人 SHIRAISHI, AKIHIKO
分类号 G02B15/163;G02B15/22 主分类号 G02B15/163
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