Auto-focusing optical system

Claim 2

An automatic focusing optical system comprising a main phototaking optical system formed to be an inverted telephoto lens, consisting of a front divergent lens group including at least one positive member and at least one negative member, the diameter of said positive member being larger than that of said negative member, and a first rear convergent lens group axially movable for focusing the image of the object; and a focused range determining optical system for forming the object image on a photoresponsive element including a second rear convergent lens group located in front of the photoresponsive element and an apertured inclined mirror placed between said front divergent lens group and said first rear convergent lens group for directing a part of the light rays from the object to the optical axis of said second convergent lens group, whereby the light rays from the object, passing through the negative member of the front divergent lens group and the aperture of said mirror, are focused by said first rear convergent lens group, and the light rays from the object, passing through the peripheral portion of said positive member outside of said negative member are reflected by the reflecting surface of said mirror toward said second convergent lens group.

Claim 3

An automatic focusing optical system according to claim 1, wherein said first rear group includes a sTop and three convergent components, the first component thereof being positioned between said mirror and said stop, thereby the remaining second and third positive components of said three components are axially moved in unison for focusing.

Claim 4

An automatic focusing optical system according to claim 2, wherein: a photo-taking lens is characterized by: A photo-taking lens is characterized by: a focal length f 80mm, relative aperture F/4.5, for use with a still camera; wherein: r1 174.94 d1 7.5 n1 1.62299 Nu 1 58.1 r2 -362.34 d2 0.1 r3 135.09 d3 13.5 n2 1.60311 Nu 2 60.7 r4 -104.02 d4 2.0 n3 1.75520 Nu 3 27.5 r5 10000.00 d5 3.7 n4 1.69895 Nu 4 30.0 r6 <42.672 d6 1.0 n5 1.51618 Nu 5 64.2 r7 50.88 d7 4.4 r8 -43.756 d8 1.2 n6 1.62041 Nu 6 60.3 r9 142.270 d9 39.538 r10 121.42 d10 4.0 n7 1.62041 Nu 7 60.3 r11 -48.713 d11 1.0 n8 1.62004 Nu 8 36.3 r12 -148.14 d12 10.877 r13 80.803 d13 4.7 n9 1.54814 Nu 9 45.9 r14 -1347.294 d14 0.7 r15 32.37 d15 10.4 n10 1.53172 Nu 10 48.9 r16 -209.947 d16 2.8 n11 1.7847 Nu 11 26.1 r17 44.615 d17 38.1 r18 137.03 d18 3.8 n12 1.62041 Nu 12 60.3 r19 -71.03 d19 3.0 r20 -31.35 d20 1.5 n13 1.744 Nu 13 44.9 r21 40.00 d21 4.9 n14 1.69895 Nu 14 30.0 r22 -1595.00 d22 0.1 r23 62.328 d23 4.0 n15 1.70154 Nu 15 41.1 r24 2466.00 and a range finder lens is characterized by: a focal length f 50mm, relative aperture F/0.8; r1 to r5 inclusive are common to the photo-taking lens and the range finder lens, wherein: r1 174.94 d1 7.5 n1 1.62299 Nu 1 58.1 r2 -362.34 d2 0.1 r3 135.09 d3 13.5 n2 1.60311 Nu 2 60.7 r4 -104.02 d4 2.0 n3 1.75520 Nu 3 27.5 r5 10000.00 dp5 67.0 rp6 -28.00 dp6 1.0 n4 1.68893 Nu 4 31.1 rp7 60.00 dp7 8.0 n5 1.691 Nu 5 54.8 rp8 -28.989 dp8 0.1 rp9 22.00 dp9 4.0 n6 1.74443 Nu 6 49.4 rp10 25.287 dp10 0.1 rp11 10.25 dp11 3.2 n7 1.80482 Nu 7 46.4 rp12 12.104 where r1, r2. . . rn represent the radii of curvature of the successive lens elements, d1, d2. . . dn 1 the center thicknesses or the intervertex air spaces of the successive lens elements, n1, n2. . . nk the refractive indices of the respective glass materials for d-line, and Nu 1, Nu 2 . . . Nu k the Abbe numbers of the respective glass materials.