Five-element copying zoom lens system

Claim 2

A copying zoom lens system consisting, in order from an object side: a first lens unit having a negative focal length; a second lens unit having a positive focal length; and a third lens unit having a negative focal length; wherein said lens system achieves zooming by changing both a distance between the first and second lens units, and a distance between the second and third lens units and by displacing said lens system with a distance between an object plane and an image plane being held constant; wherein each of said first and third lens units consists of a single negative lens element, and said second lens unit consists of a centrally disposed positive biconvex lens element that is disposed between two meniscus lens elements each having its concave surface directed toward said biconvex lens, said lens system having a five-group five-element configuration.

Claim 3

A zooming lens system according to claim 1, wherein said negative lens element of said first lens unit consists of a negative meniscus lens element that has its concave surface directed toward the object side, said negative lens element of said third lens unit consists of a negative meniscus lens element that has its concave surface directed toward the image side, said first and third lens units satisfying the following condition (1): ν.sub.1, ν.sub.5 <40 (1) where ν 1 and ν 5 are the Abbe numbers of the optical materials of which the first and third lens units are respectively made.

Claim 4

A copying zoom lens system according to claim 1 wherein said first and third lens units satisfy the following conditions (2) and (3): 1.0f<|f.sub.1 |, |f.sub.5 |<2.5f(f.sub.1, f.sub.5 <0) (2) -0.70<r.sub.1 /f, -r.sub.10 /f<-0.37 (3) where f is a focal length of the lens system for a magnification of -1.0×; f 1 is a focal length of the first lens unit; f 5 is a focal length of the third lens unit; r 1 is a radius of curvature of a surface of the first lens unit which is on an object side; and r 10 is the radius of curvature of a surface of the third lens unit which is on an image side.

Claim 5

A copying zoom lens system according to claim 2, wherein said first and third lens units satisfy the following conditions (2) and (3): 1.0f<|f.sub.1 |, |f.sub.5 |<2.5f(f.sub.1, f.sub.5 <0) (2) -0.70<r.sub.1 /f, -r.sub.10 /f<-0.37 (3) where f is a focal length of the lens system for a magnification of -1.0×; f 1 is a focal length of the first lens unit; f 5 is a focal length of the third lens unit; r 1 is a radius of curvature of a surface of the first lens unit which is on an the object side; and r 10 is the radius of curvature of a surface of the third lens unit which is on an image side.

Claim 6

A copying zoom lens system according to claim 1 wherein said second lens unit satisfies the following conditions (4) to (6): ν.sub.3 >46 (4) 0.45f>f.sub.3 >0.30f (5) 1.30>r.sub.3 /r.sub.4, r.sub.8 /r.sub.7 >1.05 (6) where ν 3 and f 3 signify an Abbe number and a focal length, respectively, of the positive biconvex lens element; r 3 and r 4 signify radii of curvature of surfaces on the object and image sides, respectively, of the meniscus lens element that is disposed on the object side of the biconvex lens element; and r 7 and r 8 signify radii of curvature of surfaces on the object and image sides, respectively, of the mesicus lens element that is disposed on the image side of said biconvex lens element.

Claim 7

A copying zoom lens system, according to claim 1: wherein, r i is the radius of curvature of the i-th lens surface numbered consequently from the object side, d i is the distance between the i-th and (i+1)-th lens surfaces, n i and ν i are the refractive index and Abbe number, respectively, of the lens having thickness d i , said lens satisfying the following table: ______________________________________ i r.sub.i d.sub.i n.sub.i ν.sub.i ______________________________________ 1 -46.446 1.254 1.80518 25.4 2 -86.176 2.000-4.551 3 17.200 5.080 1.83481 42.7 4 14.726 3.940 5 41.158 3.185 1.67790 55.3 6 -41.158 3.940 7 -14.726 5.060 1.83481 42.7 8 -17.200 2.222-5.056 9 86.176 1.254 1.80518 25.4 10 46.446 ______________________________________

Claim 8

A copying zoom lens system, according to claim 1: wherein, r i is the radius of curvature of the i-th lens surface numbered consequently from the object side, d i is the distance between the i-th and (i+1)-th lens surfaces, n i and ν i are the refractive index and Abbe number, respectively, of the lens having thickness d i , said lens satisfying the following table: ______________________________________ i r.sub.i d.sub.i n.sub.i ν.sub.i ______________________________________ 1 -47.713 2.225 1.76182 26.6 2 -90.337 2.000-4.860 3 17.191 5.344 1.80440 39.6 4 14.654 3.916 5 40.119 3.252 1.64000 60.1 6 -40.119 3.916 7 -14.654 5.344 1.80440 39.6 8 -17.191 2.222-5.400 9 90.337 2.225 1.76182 26.6 10 47.713 ______________________________________

Claim 9

A copying zoom lens system, according to claim 1: wherein, r i is the radius of curvature of the i-th lens surface numbered consequently from the object side, d i is the distance between the i-th and (i+1)-th lens surfaces, n i and ν i are the refractive index and Abbe number, respectively, of the lens having thickness d i , said lens satisfying the following table: ______________________________________ i r.sub.i d.sub.i n.sub.i ν.sub.i ______________________________________ 1 -47.701 1.800 1.74077 27.8 2 -91.192 2.000-4.905 3 17.115 5.522 1.77250 49.7 4 14.577 4.010 5 40.333 3.475 1.64000 60.1 6 -40.333 4.010 7 -14.577 5.522 1.77250 49.7 8 -17.115 2.222-5.445 9 91.192 1.800 1.74077 27.8 10 47.701 ______________________________________

Claim 10

A copying zoom lens system, according to claim 1: wherein, r i is the radius of curvature of the i-th lens surface numbered consequently from the object side, d i is the distance between the i-th and (i+1)-th lens surfaces, n i and ν i are the refractive index and Abbe number, respectively, of the lens having thickness d i , said lens satisfying the following table: ______________________________________ i r.sub.i d.sub.i n.sub.i ν.sub.i ______________________________________ 1 -47.963 3.000 1.80518 25.4 2 -87.548 2.000-4.890 3 17.041 5.200 1.83400 37.2 4 14.499 3.853 5 38.985 3.113 1.62041 60.3 6 -38.985 3.853 7 -14.499 5.200 1.83400 37.2 8 -17.041 2.222-5.433 9 87.548 3.000 1.80518 25.4 10 47.963 ______________________________________

Claim 11

A copying zoom lens system, according to claim 1: wherein, r i is the radius of curvture of the i-th lens surface numbered consequently from the object side, d i is the distance between the i-th and (i+1)-th lens surfaces, n i and ν i are the refractive index and Abbe number, respectively, of the lens having thickness d i , said lens satisfying the following table: ______________________________________ i r.sub.i d.sub.i n.sub.i ν.sub.i ______________________________________ 1 -46.804 1.800 1.64769 33.8 2 -99.643 2.000-4.909 3 17.387 5.742 1.72600 53.6 4 14.815 4.163 5 39.466 2.655 1.61800 63.4 6 -39.466 4.163 7 -14.815 5.742 1.72600 53.6 8 -17.387 2.222-5.453 9 99.643 1.800 1.64769 33.8 10 46.804 ______________________________________

Claim 12

A copying zoom lens system, according to claim 1: wherein, r i is the radius of curvature of the i-th lens surface numbered consequently from the object side, d i is the distance between the i-th and (i+1)-th lens surfaces, n i and ν i are the refractive index and Abbe number, respectively, of the lens having thickness d i , said lens satisfying the following table: ______________________________________ i r.sub.i d.sub.i n.sub.i ν.sub.i ______________________________________ 1 -42.953 2.465 1.80518 25.4 2 -74.129 2.000-4.753 3 17.140 5.430 1.80400 46.6 4 14.537 4.771 5 39.991 3.014 1.64000 60.1 6 -39.991 4.771 7 -14.537 5.430 1.80440 46.6 8 -17.140 2.222-5.280 9 74.129 2.465 1.80518 25.4 10 42.953 ______________________________________

Claim 13

A copying zoom lens system, according to claim 1: wherein, r i is the radius of curvature of the i-th lens surface numbered consequently from the object side, d i is the distance between the i-th and (i+1)-th lens surfaces, n i and ν i are the refractive index and Abbe number, respectively, of the lens having thickness d i , said lens satisfying the following table: ______________________________________ i r.sub.i d.sub.i n.sub.i ν.sub.i ______________________________________ 1 -41.458 1.544 1.80518 25.4 2 -72.482 2.000-4.497 3 17.112 5.473 1.77250 49.7 4 14.595 5.127 5 42.744 2.136 1.69680 55.5 6 -42.744 5.127 7 -14.595 5.473 1.77250 49.7 8 -17.112 2.222-4.996 9 71.630 1.084 1.80518 25.4 10 41.509 ______________________________________

Claim 14

A copying zoom lens system, according to claim 1: wherein, r i is the radius of curvature of the i-th lens surface numbered consequently from the object side, d i is the distance between the i-th and (i+1)-th lens surfaces, n i and ν i are the refractive index and Abbe number, respectively, of the lens having thickness d i , said lens satisfying the following table: ______________________________________ i r.sub.i d.sub.i n.sub.i ν.sub.i ______________________________________ 1 -41.222 1.411 1.80518 25.4 2 -71.989 2.000-4.450 3 17.073 5.611 1.72000 50.3 4 14.644 5.332 5 45.049 2.050 1.72916 54.7 6 -45.049 5.332 7 -14.644 5.623 1.72000 50.3 8 -17.073 2.222-4.953 9 71.989 1.000 1.80518 25.4 10 41.222 ______________________________________

Claim 15

A copying zoom lens system, according to claim 1: wherein, r i is the radius of curvature of the i-th lens surface numbered consequently from the object side, d i is the distance between the i-th and (i+1)-th lens surfaces, n i and ν i are the refractive index and Abbe number, respectively, of the lens having thickness d i , said lens satisfying the following table: ______________________________________ i r.sub.i d.sub.i n.sub.i ν.sub.i ______________________________________ 1 -42.568 4.892 1.78470 26.2 2 -68.855 2.000-5.717 3 17.101 5.761 1.80300 46.7 4 14.182 4.508 5 31.588 2.415 1.48749 70.1 6 -31.588 4.508 7 -14.182 5.761 1.80300 46.7 8 -17.101 2.000-5.717 9 69.433 4.711 1.78470 26.2 10 42.626 ______________________________________

Claim 16

A copying zoom lens system, according to claim 1: wherein, r i is the radius of curvature of the i-th lens surface numbered consequently from the object side, d i is the distance between the i-th and (i+1)-th lens surfaces, n i and ν i are the refractive index and Abbe number, respectively, of the lens having thickness d i , said lens satisfying the following table: ______________________________________ i r.sub.i d.sub.i n.sub.i ν.sub.i ______________________________________ 1 -41.365 2.397 1.80518 25.4 2 -71.166 2.000-4.898 3 16.973 5.652 1.72916 54.7 4 14.410 5.257 5 41.756 2.837 1.65160 58.5 6 -41.058 5.257 7 -14.526 5.731 1.72916 54.7 8 -17.078 2.000-4.898 9 71.033 2.949 1.80518 25.4 10 42.021 ______________________________________