Zoom lens having long back-focal distance


PURPOSE: To provide a zoom lens constituted of four groups for securing a long back-focal distance in which a color separation prism and a quick returning mirror, etc., can be arranged. CONSTITUTION: The zoom lens has a first lens group having positive refracting power, a second lens group 2 having negative refracting power, a third lens group 3 having negative refracting power, and a fourth lens group 4 having positive refracting power in order from an object side, executes zooming by moving the second and the third lens groups, and when focal distances in the third lens group and the wide end of a whole system are denoted as f 3 and fw, respectively, and the back-focal distance by air conversion is denoted as SK, the conditional expression of -0.3<fw/f 3 <-0.2,0.11<fw/sk'<0.1 is satisfied. COPYRIGHT: (C)1992,JPO&Japio




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Cited By (2)

    Publication numberPublication dateAssigneeTitle
    US-5841582-ANovember 24, 1998Fugi Photo Optical Co., Ltd.Zoom lens optical system
    US-5889619-AMarch 30, 1999Asahi Kogaku Kogyo Kabushiki KaishaZoom lens system