Large aperture ratio zoom lens system

Claim 2

A large aperture ratio zoom lens system comprising in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens unit having negative refractive power, and a fourth lens group consisting of a front subunit and a rear subunit wherein said front subunit consists of a positive lens element, a positive lens element and a negative lens element and said rear subunit consists of one positive lens element, said fourth lens group having at least one aspherical surface.

Claim 3

A large aperture ratio zoom lens system comprising in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens unit having negative refractive power, and a fourth lens group consisting of a front subunit and rear subunit wherein said front subunit consists of a positive lens element, a positive lens element and a negative lens element and said rear subunit consists of two positive lens elements, said fourth lens group having at least one aspherical surface.

Claim 4

A large aperture ratio zoom lens system comprising in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens unit having negative refractive power, and a fourth lens group consisting of a front subunit and rear subunit wherein said front subunit consists of a positive lens element, a positive lens element and a negative lens element and said rear subunit consists of two positive lens elements, said fourth lens group having at least one aspherical surface.

Claim 5

A large aperture ratio zoom lens system according to claim 1 or 2 wherein the surface on the object side of the negative lens component in said front subunit is arranged as an aspherical surface.

Claim 6

A large aperture ratio zoom lens system according to claim 3 wherein said aspherical surface fulfills the conditions (1) and (2) shown below: |Δx|≦1.0×10.sup.-4 ·f.sub.IV (when y=0.1f.sub.IV) (1) 0<|Δx|≦1.6×10.sup.-3 ·f.sub.IV (when y=0.2f.sub.IV) (2) where, reference symbol f IV represents the focal length of the fourth lens group, reference symbol y represents the height of the aspherical surface from the optical axis, and reference symbol Δx represents the amount of deviation of the aspherical surface from the reference spherical surface in the direction of the optical axis.

Claim 7

A large aperture ratio zoom lens system according to claim 4 wherein said first lens group comprises a cemented doublet, which comprises a negative lens element and a positive lens element, and a positive lens component, and said positive lens component in said first lens group is arranged as a plastic lens having an aspherical surface.

Claim 8

A large aperture ratio zoom lens system according to claim 4 wherein said first lens group comprises a cemented doublet, which comprises a negative lens element and a positive lens element, and a positive lens component, said second lens group comprises a negative lens component and a cemented doublet which consists of a negative lens element and a positive lens element, said third lens group comprises a negative lens component, and said fourth lens group comprises a front subgroup and a rear subgroup wherein said front subgroup comprises a positive lens component, a positive lens component and a negative lens component, and said rear subgroup comprises a positive lens component and a positive lens component, and wherein the surface on the object side of said negative lens component constituting said front subgroup is arranged as an aspherical surface expressed by the formula shown below, said large aperture ratio zoom lens system being further arranged to have the following numerical data: ______________________________________ r.sub.1 = 91.0802 d.sub.1 = 1.1600 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 30.2915 d.sub.2 = 7.3000 n.sub.2 = 1.62012 ν.sub.2 = 49.66 r.sub.3 = -258.6038 d.sub.3 = 0.1700 r.sub.4 = 30.2583 d.sub.4 = 5.6000 n.sub.3 = 1.62374 ν.sub.3 = 47.10 r.sub.5 = 203.5944 d.sub.5 = 0.6005˜9.324˜15.617 r.sub.6 = 27.3251 d.sub.6 = 1.0400 n.sub.4 = 1.73400 ν.sub.4 = 51.49 r.sub.7 = 11.8094 d.sub.7 = 3.9500 r.sub.8 = -23.1741 d.sub.8 = 1.0400 n.sub.5 = 1.69680 ν.sub.5 = 55.52 r.sub.9 = 15.5878 d.sub.9 = 3.1000 n.sub.6 = 1.84666 ν.sub.6 = 23.88 r.sub.10 = 162.3555 d.sub.10 = 12.2489˜3.639˜3.876 r.sub.11 = -16.3682 d.sub.11 = 1.0000 n.sub.7 = 1.69680 ν.sub.7 = 55.52 r.sub.12 = -27.6950 d.sub.12 = 7.5084˜7.393˜0.856 r.sub.13 = 110.1269 d.sub.13 = 2.6726 n.sub.8 = 1.75700 ν.sub.8 = 47.87 r.sub.14 = -43.5026 d.sub.14 = ∞ 0.6433 r.sub.15 = ∞ (stop) d.sub.15 = 2.0000 r.sub.16 = 20.5138 d.sub.16 = 4.9219 n.sub.9 = 1.69680 ν.sub.9 = 55.52 r.sub.17 = -106.5718 d.sub.17 = 3.2576 r.sub.18 = -23.2475 (aspherical surface) d.sub.18 = 1.4025 n.sub.10 = 1.84666 ν.sub.10 = 23.88 r.sub.19 = 21.0405 d.sub.19 = 6.0991 r.sub.20 = 372.7992 d.sub.20 = 3.9223 n.sub.11 = 1.56873 ν.sub.11 = 63.16 r.sub.21 = -15.7166 d.sub.21 = 0.1342 r.sub.22 = 26.3505 d.sub.22 = 3.9299 n.sub.12 = 1.56873 ν.sub.12 = 63.16 r.sub.23 = -101.3900 f = 14˜42 F/2.0 coefficient of aspherical surface (r.sub.18) B = 0, E = -0.19088 × 10.sup.-4, F = -0.51486 × 10.sup.-7 G = 0.33866 × 10.sup.-9, H = 0.5000 × 10.sup.-13 ##STR1## ______________________________________ where, reference symbols r 1 through r 23 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 22 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 12 respectively represent refractive indices of respective lenses, reference symbols ν 1 through ν 12 respectively represent Abbe's numbers of respective lenses, reference symbol r represents the radius of curvature of the reference spherical surface for the aspherical surface, rererence symbol x represents the distance from an arbitrary point on the aspherical surface to the tangential plane which is tangential to the aspherical surface at the vertex thereof, reference symbol y represents the distance from said arbitrary point to the optical axis, and reference symbols B, E, F, G and H respectively represent the coefficients of aspherical surface.

Claim 9

A large aperture ratio zoom lens system according to claim 6 wherein said first lens group comprises a cemented doublet, which comprises a negative lens element and a positive lens element, and a positive lens component, said second lens group comprises a negative lens component and a cemented doublet, which comprises a negative lens element and a positive lens element, said third lens group comprises a negative lens component, and said fourth lens group comprises a front subgroup and a rear subgroup wherein said front subgroup comprises a positive lens component, a positive lens component and a negative lens component, and said rear subgroup comprises positive lens component and a positive lens component, said large aperture ratio zoom lens system being arranged that the surface on the object side of said positive lens component constituting said first lens group and the surface on the object side of said negative lens component constituting said front subgroup are respectively arranged as aspherical surfaces expressed by the formula shown below, said large aperture ratio zoom lens system being further arranged to have the following numerical data: ______________________________________ r.sub.1 = 85.0712 d.sub.1 = 1.1600 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 29.7580 d.sub.2 = 8.0000 n.sub.2 = 1.62374 ν.sub.2 = 47.10 r.sub.3 = -163.7286 d.sub.3 = 0.1700 r.sub.4 = 26.0710 (aspherical surface) d.sub.4 = 6.0000 n.sub.3 = 1.49109 ν.sub.3 = 57.00 r.sub.5 = 191.4729 d.sub.5 = 0.6002˜8.872˜14.853 r.sub.6 = 29.2330 d.sub.6 = 1.0400 n.sub.4 = 1.72916 ν.sub.4 = 54.68 r.sub.7 = 11.6601 d.sub.7 = 3.9500 r.sub.8 = -20.4964 d.sub.8 = 1.0400 n.sub.5 = 1.69680 ν.sub.5 = 55.52 r.sub.9 = 16.4230 d.sub.9 = 3.1000 n.sub.6 = 1.84666 ν.sub.6 = 23.88 r.sub.10 = 174.3451 d.sub.10 = 12.7187˜3.467˜4.077 r.sub.11 = -16.6009 d.sub.11 = 1.0000 n.sub.7 = 1.69680 ν.sub.7 = 55.52 r.sub.12 = -25.4742 d.sub.12 = 6.4669˜7.446˜0.856 r.sub.13 = 104.7398 d.sub.13 = 2.6726 n.sub.8 = 1.76200 ν.sub.8 = 40.10 r.sub.14 = -45.1397 d.sub.14 = 0.6433 r.sub.15 = ∞ (stop) d.sub.15 = 2.0000 r.sub.16 = 19.4140 d.sub.16 = 4.6702 n.sub.9 = 1.69680 ν.sub.9 = 55.52 r.sub.17 = -61.1447 d.sub.17 = 3.2247 r.sub.18 = -19.2492 (aspherical surface) d.sub.18 = 1.4025 n.sub.10 = 1.84666 ν.sub.10 = 23.88 r.sub.19 = 19.4429 d.sub.19 = 5.8839 r.sub.20 = 334.8746 d.sub.20 = 3.9217 n.sub.11 = 1.56873 ν.sub.11 = 63.16 r.sub.21 = -15.6686 d.sub.21 = 0.1342 r.sub.22 = 29.9458 d.sub.22 = 3.9010 n.sub.12 = 1.56873 ν.sub.12 = 63.16 r.sub.23 = -56.2051 f = 14˜42 F/2.0 coefficient of aspherical surface (r.sub.4) B = 0, E = -0.20399 × 10.sup.-6, F = -0.26140 × 10.sup.-9 G = -0.49659 × 10.sup.-12, H = 0 coefficient of aspherical surface (r.sub.18) B = 0, E = -0.10649 × 10.sup.-4, F = 0.46490 × 10.sup.-7 G = 0.75166 × 10.sup.-9, H = 0.5000 × 10.sup.-13 ##STR2## ______________________________________ where, reference symbols r 1 through r 23 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 22 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 12 respectively represent refractive indices of respective lenses, reference symbols ν 1 through ν 12 respectively represent Abbe's numbers of respective lenses, reference symbol r represents the radius of curvature of the reference spherical surface for the aspherical surface, reference symbol x represents the distance from an arbitrary point on the aspherical surface to the tangential plane which is tangential to the aspherical surface at the vertex thereof, reference symbol y represents the distance from said arbitrary point to the optical axis, and reference symbols B, E, F, G and H respectively represent the coefficients of aspherical surface.

Claim 10

A large aperture ratio zoom lens system according to claim 4 wherein said first lens group comprises a cemented doublet, which consists of a negative lens element and a positive lens element, and a positive lens component, said second lens group comprises a negative lens component and a cemented doublet, which comprises a negative lens element and a positive lens element, said third lens group comprises a negative lens component, and said fourth lens group comprises a front subgroup and a rear subgroup wherein said front subgroup comprises a positive lens component, a positive lens component and a negative lens component, and said rear subgroup comprises a positive lens component, said large aperture ratio zoom lens system being arrqnged that the surface on the object side of said positive lens component, which is located on the object side in said front subgroup, and the surface on the object side of said negative lens component constituting said front subgroup are respectively arranged as aspherical surfaces expressed by the formula shown below, said large aperture ratio zoom lens system being further arranged to have the following numerical data: ______________________________________ r.sub.1 = 50.8931 d.sub.1 = 1.1600 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 26.4712 d.sub.2 = 8.0000 n.sub.2 = 1.62012 ν.sub.2 = 49.66 r.sub.3 = 224.5904 d.sub.3 = 0.1700 r.sub.4 = 35.7052 d.sub.4 = 5.6000 n.sub.3 = 1.62280 ν.sub.3 = 57.06 r.sub.5 = 397.0655 d.sub.5 = 0.5936˜9.007˜16.202 r.sub.6 = 32.5210 d.sub.6 = 1.0400 n.sub.4 = 1.73400 ν.sub.4 = 51.49 r.sub.7 = 11.5208 d.sub.7 = 4.5000 r.sub.8 = -19.2961 d.sub.8 = 1.0400 n.sub.5 = 1.69350 ν.sub.5 = 50.81 r.sub.9 = 15.0067 d.sub.9 = 3.2000 n.sub.6 = 1.84666 ν.sub.6 = 23.88 r.sub.10 = 410.7138 d.sub.10 = 20.1171˜10.212˜4.885 r.sub.11 = -13.1594 d.sub.11 = 1.0000 n.sub.7 = 1.70154 ν.sub.7 = 41.21 r.sub.12 = -23.7756 d.sub.12 = 1.1800˜1.987˜0.859 r.sub.13 = ∞ (stop) d.sub.13 = 2.0000 r.sub.14 = 59.3543 (aspherical surface) d.sub.14 = 3.4701 n.sub.8 = 1.73400 ν.sub.8 = 51.49 r.sub.15 = -27.4634 d.sub.15 = 0.7734 r.sub.16 = 29.7635 d.sub.16 = 3.0017 n.sub.9 = 1.56873 ν.sub.9 = 63.16 r.sub.17 = -50.4782 d.sub.17 = 4.1000 r.sub.18 = 50.4461 (aspherical surface) d.sub.18 = 1.4029 n.sub.10 = 1.84666 ν.sub.10 = 23.88 r.sub.19 = 12.8741 d.sub.19 = 5.3524 r.sub.20 = 28.1332 d.sub.20 = 5.2458 n.sub.11 = 1.56873 ν.sub.11 = 63.16 r.sub.21 = -19.9751 f = 14˜42 F/2.0 coefficient of aspherical surface (r.sub.14 ) B = 0, E = -0.47194 × 10.sup.-4, F = 0.20828 × 10.sup.-6 G = -0.10733 × 10.sup.-8, H = -0.16497 × 10.sup.-10 coefficient of aspherical surface (r.sub.18) B = 0 , E = 0.79803 × 10.sup.-5, F = 0.11435 × 10.sup.-7 G = 0.17049 × 10.sup.-8, H = 0.50561 × 10.sup.-11 ##STR3## ______________________________________ where, reference symbols r 1 through r 21 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 20 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 11 respectively represent refractive indices of respective lenses, reference symbols ν 1 through ν 11 respectively represent Abbe's numbers of respective lenses, reference symbol r represents the radius of curvature of the reference spherical surface for the aspherical surface, reference symbol x represents the distance from an arbitrary point of the aspherical surface to the tangential plane which is tangential to the aspherical surface at the vertex thereof, reference symbol y represents the distance from said arbitrary point to the optical axis, and reference symbols B, E, F, G and H respectively represent the coefficients of aspherical surface.

Claim 11

A large aperture ratio zoom lens system according to claim 1 or 2 wherein said zoom lens system fulfills the conditions (3) and (4): 1.5f.sub.IV <l<2.2f.sub.IV ( 3) 0.14f.sub.IV <D<0.55f.sub.IV ( 4) where, reference symbol l represents the distance from the rear principal point of the negative lens component which constitutes the front subunit in the fourth lens group to the rear focal point of the zoom lens system as a whole, and reference symbol D represents the airspace between the front subunit and rear subunit in the fourth lens group.