High variable power ratio zoom lens

Claim 2

A zoom lens having, in succession from the object side, a first lens unit G1 having positive refractive power, a second lens unit G2 having positive refractive power, and a third lens unit G3 having negative refractive power, the spacing between said first lens unit G1 and said second lens unit G2 being increased and the spacing between said second lens unit G2 and said third lens unit G3 being decreased during the magnification change from the wide angle end to the telephoto end, said first lens unit G1 having at least one positive lens and at least one negative lens, said second lens unit G2 comprising, in succession from the object side, a front group GF of weak refractive power and a rear group GR of positive refractive power, said front group GF having at least one negative lens and at least one positive lens, said rear group GR having at least one positive lens and at least one negative lens, said third lens unit G3 having at least one positive lens and at least one negative lens, said zoom lens satisfying the following conditions: ##EQU3## ps where f1 is the focal length of said first lens unit G1, f2 is the focal length of said second lens unit G2, f3 is the focal length of said third lens unit G3, fF is the focal length of said front group GF, fR is the focal length of said rear group GR, fW is the focal length of the whole system at the wide angle end, and IIRT is the third-order comatic aberration coefficient of said rear group GR at the telephoto end when the focal length at the telephoto end is normalized into 1.

Claim 3

A zoom lens according to claim 1, further satisfying the following condition: -0.3≦f2fF≦0

Claim 4

A zoom lens according to claim 1, wherein said rear group in said second lens unit has, in succession from the object side, at least one positive lens LR1, at least one negative lens and at least one positive lens.

Claim 5

A zoom lens according to claim 1, wherein any positive lens and any negative lens in the rear group in said second lens unit are cemented together.

Claim 6

A zoom lens according to claim 1, further satisfying the following condition: -1.2≦R/fR≦-0.2, when the object side surface of the positive lens LR1 in the rear group in said second lens unit is a concave surface and the radius of curvature of the object side surface of said positive lens is R.

Claim 7

A zoom lens according to claim 1, having a stop between the front group and the rear group in said second lens unit.

Claim 8

A zoom lens according to claim 5, wherein only the rear group in said second lens unit is moved in a direction orthogonal to the optical axis to thereby effect the correction of image vibration.

Claim 9

A zoom lens according to claim 1, wherein the spacing between the front group and the rear group in said second lens unit is slightly varied during zooming.

Claim 10

A zoom lens according to claim 1, wherein the spacing between the front group and the rear group in said second lens unit is slightly varied during focusing.

Claim 11

A zoom lens according to claim 1, wherein the focusing from infinity to the close distance is effected by said third lens unit being moved toward the image plane.

Claim 12

A zoom lens according to claim 1, having the following lens data: ______________________________________ f = 39.00-102.00 F = 4.08-8.05 2ω = 57.20°-23.32° ______________________________________ r d ν n ______________________________________ 1 -114.155 1.50 33.9 1.80384 2 34.074 1.00 3 34.383 5.30 54.0 1.61720 4 -45.270 0.10 5 30.065 2.60 60.1 1.62041 6 73.586 (d6) 7 -22.875 1.10 46.5 1.80411 8 13.576 3.10 28.2 1.74000 9 -88.720 0.80 10 -491.918 2.00 64.1 1.51680 11 -19.079 2.00 12 (stop) 2.00 13 -14.370 5.70 69.9 1.51860 14 -9.069 1.40 23.0 1.86074 15 -13.774 0.10 16 70.726 2.70 69.9 1.51860 17 -26.349 (d17) 18 -47.072 3.40 27.6 1.75520 19 -18.922 2.20 20 -17.796 1.30 43.3 1.84042 21 -124.763 4.00 22 -16.876 1.40 55.6 1.69680 23 -46.779 (B.f) ______________________________________ (variable spacing during magnification change) ______________________________________ f 38.9998 69.9996 101.9998 d6 3.2347 10.3035 17.0677 d17 15.0298 7.2691 3.1954 B.f 8.9728 31.0851 48.8923 ______________________________________ (condition-corresponding values) ______________________________________ (1) f2/fF = -0.020 (2) f2/fR = 0.872 (3) fW/f1 = 0.623 (4) fW/f2 = 1.246 (5) fW/f3 = -1.609 (6) IIRT = 0.661 (7) D/fR = 0.159 (8) νP - νN = 46.9 (9) R/fR = -0.401 ______________________________________ where f is the focal length, F is the F number, 2 ω is the angle of view, the numbers at the left end in the above table represent the order from the object side, r is the radius of curvature of each lens surface, d is the spacing between adjacent lens surfaces, n and ν are the values of refractive index and Abbe number, respectively, for d line (γ=587.6 nm), f1 is the focal length of the first lens unit G1, f2 is the focal length of the second lens unit G2, f3 is the focal length of the third lens unit, fF is the focal length of the front group GF in the second lens unit, fR is the focal length of the rear group in the second lens unit, fW is the focal length of the whole system at the wide angle end, IIRT is the third-order comatic aberration coefficient of the rear group GR in the second lens unit at the telephoto end when the focal length at the telephoto end is normalized into 1, D is the on-axis lens thickness of the positive lens LR1 in the rear group, νP is the average value of the Abbe numbers of the positive lenses in the rear group GR, νN is the average value of the Abbe numbers of the negative lenses in the rear group GR, and R is the radius of curvature of the object side surface of the positive lens LR1 in the rear group.

Claim 13

A zoom lens having, in succession from the object side, a first lens unit G1 having positive refractive power, a second lens unit G2 having positive refractive power, and a third lens unit G3 having negative refractive power, the spacing between said first lens unit G1 and said second lens unit G2 being increased and the spacing between said second lens unit G2 and said third lens unit G3 being decreased during the magnification change from the wide angle end to the telephoto end, said first lens unit G1 having at least one positive lens and at least one negative lens, said second lens unit G2 comprising, in succession from the object side, a front group GF of weak refractive power and a rear group GR of positive refractive power, said front group GF having at least one negative lens and at least one positive lens, said rear group GR having, in succession from the object side, at least one positive lens LR1, at least one negative lens and at least one positive lens, said third lens unit G3 having at least one positive lens and at least one negative lens, said zoom lens satisfying the following conditions: ______________________________________ -0.3 ≦ f2/fF ≦ 0.3 0.7 ≦ f2/fR ≦ 1.3 0.4 ≦ fW/f1 ≦ 0.8 1.0 ≦ fW/f2 ≦ 1.5 1.0 ≦ fW/f3 ≦ 2.0, f3 < 0 0.1 ≦ D/fR ≦ 0.3 ______________________________________ where f1 is the focal length of said first lens unit G1, f2 is the focal length of said second lens unit G2, f3 is the focal length of said third lens unit G3, fF is the focal length of said front group GF, fR is the focal length of said rear group GR, fW is the focal length of the whole system at the wide angle end, and D is the on-axis lens thickness of said positive lens LR1.

Claim 14

A zoom lens having, in succession from the object side, a first lens unit G1 having positive refractive power, a second lens unit G2 having positive refractive power, and a third lens unit G3 having negative refractive power, the spacing between said first lens unit G1 and said second lens unit G2 being increased and the spacing between said second lens unit G2 and said third lens unit G3 being decreased during the magnification change from the wide angle end to the telephoto end, said first lens unit G1 having at least one positive lens and at least one negative lens, said second lens unit G2 comprising, in succession from the object side, a front group GF of weak refractive power and a rear group GR of positive refractive power, said front group GF having at least one negative lens and at least one positive lens, said rear group GR having, in succession from the object side, at least one positive lens LR1, at least one negative lens and at least one positive lens, said third lens unit G3 having at least one positive lens and at least one negative lens, said zoom lens satisfying the following conditions: ______________________________________ -0.3 ≦ f2/fF ≦ 0.3 0.7 ≦ f2/fR ≦ 1.3 0.4 ≦ fW/f1 ≦ 0.8 1.0 ≦ fW/f2 ≦ 1.5 1.0 ≦ fW/f3 ≦ 2.0, f3 < 0 0.1 ≦ D/fR ≦ 0.3 ______________________________________ where f1 is the focal length of said first lens unit G1, f2 is the focal length of said second lens unit G2, f3 is the focal length of said third lens unit G3, fF is the focal length of said front group GF, fR is the focal length of said rear group GR, fW is the focal length of the whole system at the wide angle end, and D is the on-axis lens thickness of said positive lens LR1.

Claim 15

A zoom lens according to claim 12, further satisfying the following condition: -0.3≦f2/fF≦0

Claim 16

A zoom lens according to claim 12, wherein any positive lens and any negative lens in the rear group in said second lens unit are cemented together.

Claim 17

A zoom lens according to claim 12, further satisfying the following condition: -1.2≦R/fR≦-0.2, when the object side surface of the positive lens LR1 in the rear group in said second lens unit is a concave surface and the radius of curvature of the object side surface of said positive lens is R.

Claim 18

A zoom lens according to claim 12, having a stop between the front group and the rear group in said second lens unit.

Claim 19

A zoom lens according to claim 15, wherein only the rear group in said second lens unit is moved in a direction orthogonal to the optical axis to thereby effect the correction of image vibration.

Claim 20

A zoom lens according to claim 12, wherein the spacing between the front group and the rear group in said second lens unit is slightly varied during zooming.

Claim 21

A zoom lens according to claim 12, wherein the spacing between the front group and the rear group in said second lens unit is slightly varied during focusing.

Claim 22

A zoom lens according to claim 12, wherein the focusing from infinity to the close distance is effected by said third lens unit being moved toward the image plane.

Claim 23

A zoom lens according to claim 12, further satisfying the following condition: -1.0≦IIRT≦3.0, where IIRT is the third-order comatic aberration coefficient of the rear group GR in said second lens unit at the telephoto end when the focal length at the telephoto end is normalized into 1.

Claim 24

A zoom lens according to claim 12, having the following lens data: ______________________________________ f = 38.96-101.99 F = 3.92-8.14 2ω = 57.32°-23.49° ______________________________________ r d ν n ______________________________________ 1 -270.801 1.50 43.3 1.84042 2 27.974 1.40 3 30.217 5.80 82.6 1.49782 4 -120.608 0.10 5 32.131 5.50 67.9 1.59319 6 -94.084 (d6) 7 -30.560 1.20 46.5 1.80411 8 15.695 3.00 27.6 1.74077 9 -63.482 1.40 10 -74.613 1.50 65.7 1.46450 11 -22.711 2.00 12 (stop) 2.00 13 -13.794 5.70 82.6 1.49782 14 -9.913 1.40 23.8 1.84666 15 -16.252 0.10 16 -46.718 2.00 70.4 1.48749 17 -17.605 0.10 18 58.479 1.70 70.4 1.48749 19 -51.884 (d19) 20 -25.121 3.00 25.4 1.80518 21 -20.048 5.20 22 -19.167 1.30 60.0 1.64000 23 -10668.908 5.00 24 -20.265 1.40 60.0 1.64000 25 -42.976 (B.f) ______________________________________ (variable spacing during magnification change) ______________________________________ f 38.9614 69.9603 101.9946 d6 4.8200 12.6413 16.3480 d19 13.6289 5.8075 2.1009 B.f 6.7975 28.2677 49.6732 ______________________________________ (condition-corresponding values) ______________________________________ (1) f2/fP = -0.057 (2) f2/fR = 0.920 (3) fW/f1 = 0.623 (4) fW/f2 = 1.246 (5) fW/f3 = -1.609 (6) IIRT = 0.862 (7) D/fR = 0.168 (8) νP - νN = 50.7 (9) R/fR = -0.406 ______________________________________ where f is the focal length, F is the F number, 2 ω is the angle of view, the numbers at the left end in the above table represent the order from the object side, r is the radius of curvature of each lens surface, d is the spacing between adjacent lens surfaces, n and ν are the values of refractive index and Abbe number, respectively, for d line (γ=587.6 nm), f1 is the focal length of the first lens unit G1, f2 is the focal length of the second lens unit G2, f3 is the focal length of the third lens unit G3, f F is the focal length of the front group GF in the second lens unit, fR is the focal length of the rear group GR in the second lens unit, fW is the focal length of the whole system at the wide angle end, IIRT is the third-order comatic aberration coefficient of the rear group GR in the second lens unit at the telephoto end when the focal length at the telephoto end is normalized into 1, D is the on-axis lens thickness of the positive lens LR1 in the rear group, νP is the average value of the Abbe numbers of the positive lenses in the rear group GR, νN is the average value of the Abbe numbers of the negative lenses in the rear group GR, and R is the radius of curvature of the object side surface of the positive lens LR1 in the rear group.

Claim 25

A zoom lens having, in succession from the object side, a first lens unit G1 having positive refractive power, a second lens unit G2 having positive refractive power, and a third lens unit G3 having negative refractive power, the spacing between said first lens unit G1 and said second lens unit G2 being increased and the spacing between said second lens unit G2 and said third lens unit G3 being decreased during the magnification change from the wide angle end to the telephoto end, said first lens unit G1 having at least one positive lens and at least one negative lens, said second lens unit G2 comprising, in succession from the object side, a front group GF of weak refractive power and a rear group GR of positive refractive power, said first group GF having at least one negative lens and at least one positive lens, said rear group GR having at least two positive lenses and at least one negative lens, said third lens unit G3 having at least one positive lens and at least one negative lens, said zoom lens satisfying the following conditions: ______________________________________ -0.3 ≦ f2/fF ≦ 0.3 0.7 ≦ f2/fR ≦ 1.3 0.4 ≦ fW/f1 ≦ 0.8 1.0 ≦ fW/f2 ≦ 1.5 1.0 ≦ fW/f3 ≦ 2.0, f3 < 0 0.1 ≦ D/fR ≦ 0.3 ______________________________________ where f1 is the focal length of said first lens unit G1, f2 is the focal length of said second lens unit G2, f3 is the focal length of said third lens unit G3, fF is the focal length of said front group GF, fR is the focal length of said rear group GR, νP is the average value of the Abbe numbers of the positive lenses in said rear group GR, and νN is the average value of the Abbe numbers of the negative lenses in said rear group GR.

Claim 26

A zoom lens having, in succession from the object side, a first lens unit G1 having positive refractive power, a second lens unit G2 having positive refractive power, and a third lens unit G3 having negative refractive power, the spacing between said first lens unit G1 and said second lens unit G2 being increased and the spacing between said second lens unit G2 and said third lens unit G3 being decreased during the magnification change from the wide angle end to the telephoto end, said first lens unit G1 having at least one positive lens and at least one negative lens, said second lens unit G2 comprising, in succession from the object side, a front group GF of weak refractive power and a rear group GR of positive refractive power, said first group GF having at least one negative lens and at least one positive lens, said rear group GR having at least two positive lenses and at least one negative lens, said third lens unit G3 having at least one positive lens and at least one negative lens, said zoom lens satisfying the following conditions: ______________________________________ -0.3 ≦ f2/fF ≦ 0.3 0.7 ≦ f2/fR ≦ 1.3 0.4 ≦ fW/f1 ≦ 0.8 1.0 ≦ fW/f2 ≦ 1.5 1.0 ≦ fW/f3 ≦ 2.0, f3 < 0 0.1 ≦ D/fR ≦ 0.3 ______________________________________ where f1 is the focal length of said first lens unit G1, f2 is the focal length of said second lens unit G2, f3 is the focal length of said third lens unit G3, fF is the focal length of said front group GF, fR is the focal length of said rear group GR, νP is the average value of the Abbe numbers of the positive lenses in said rear group GR, and νN is the average value of the Abbe numbers of the negative lenses in said rear group GR.

Claim 27

A zoom lens according to claim 23, further satisfying the following condition: -0.3≦f2/fF≦0

Claim 28

A zoom lens according to claim 23, wherein the rear group in said second lens unit has, in succession from the object side, at least one positive lens LR1, at least one negative lens and at least one positive lens.

Claim 29

A zoom lens according to claim 23, wherein any positive lens and any negative lens in the rear group in said second lens unit are cemented together.

Claim 30

A zoom lens according to claim 23, further satisfying the following condition: -1.2≦R/fR≦-0.2 when the object side surface of the positive lens LR1 in the rear group in said second lens unit is a concave surface and the radius of curvature of the object side surface of said positive lens is R.

Claim 31

A zoom lens according to claim 23, having a stop between the front group and the rear group in said second lens unit.

Claim 32

A zoom lens according to claim 27, wherein only the rear group in said second lens unit is moved in a direction orthogonal to the optical axis to thereby effect the correction of image vibration.

Claim 33

A zoom lens according to claim 23, wherein the spacing between the front group and the rear group in said second lens unit is slightly varied during zooming.

Claim 34

A zoom lens according to claim 23, wherein the spacing between the front group and the rear group in said second lens unit is slightly varied during focusing.

Claim 35

A zoom lens according to claim 23, wherein the focusing from infinity to the close distance is effected by said third lens unit being moved toward the image plane.

Claim 36

A zoom lens according to claim 23, further satisfying the following condition: -1.0≦IIRT≦3.0, where IIRT is the third-order comatic aberration coefficient of the rear group GR in said second lens unit at the telephoto end when the focal length at the telephoto end is normalized into 1.

Claim 37

A zoom lens according to claim 25, further satisfying the following condition: 0.1≦D/fR≦0.3 where D is the on-axis lens thickness of the positive lens LR1 in the rear group in said second lens unit.