Compact zoom lens system

Claim 2

A compact zoom lens system comprising a first lens group having positive refractive power and a second lens group having negative refractive power in the order from the object side wherein said first lens group comprises at least two positive lenses and at least one negative lens, and said second lens group comprises a positive lens and a negative lens in the order from the object side, said compact zoom lens system being arranged to be zoomed by varying the airspace between said first lens group and said second lens group, said compact zoom lens system being further arranged to fulfill the conditions (1) through (4) shown below: (1) 0.5<f 1 /f w <1.0 (2) 0.6<|f 2 |/f w <1.4, f 2 <0 (3) 0<D w /f w <0.5 (4) 0.1<P w /f w <0.5 where, reference symbols f 1 and f 2 respectively represent focal lengths of the first lens group and second lens group, reference symbol f w represents the focal length of the lens system as a whole in the wide position, reference symbol D w represents the airspace between the first lens group and second lens group in the wide position, and reference symbol P w represents the distance from the exit pupil to the rearmost surface of the lens system in the wide position.

Claim 3

A compact zoom lens system according to claim 1 wherein said first lens group is provided with an aspherical surface expressed by the formula shown below: ##EQU2## where, reference symbols x and y respectively represent values of coordinates in the coordinate system where the optical axis is traced as the x axis and the y axis is traced perpendicularly to the x axis taking the intersecting point between the aspherical surface and optical axis as the origin, reference symbol r represents the radius of curvature of the vertex portion of the aspherical surface, and reference symbols B, E, F, G, H, . . . respectively represent the coefficients of aspherical surface of the second order, fourth order, sixth order, eighth order, tenth order and so on.

Claim 4

A compact zoom lens system according to claim 1 wherein said second lens group is provided with an aspherical surface expressed by the formula shown below: ##EQU3## where, reference symbols x and y respectively represent values of coordinates in the coordinate system where the optical axis is traced as the x axis and the y axis is traced perpendicularly to the x axis taking the intersecting point between the aspherical surface and optical axis as the origin, reference symbol r represents the radius of curvature of the vertex portion of the aspherical surface, and reference symbols B, E, F, G, H, . . . respectively represent the coefficients of aspherical surface of the second order, fourth order, sixth order, eighth order, tenth order and so on.

Claim 5

A compact zoom lens system according to claim 1 further fulfilling the conditions (5) through (8) shown below: (5) 0.1<d/f 1 <0.5 (6) 0.1<r a /f 1 <0.7 (7) 0.1<|r b |/f 1 <1.0, r b <0 (8) 0.2<r c /f 2 <0.7, r c <0 where, reference symbol d represents the sum of thicknesses of positive lenses arranged between the negative lens in the first lens group and stop, reference symbol r a represents the radius of curvature of the surface on the image side of the negative lens in the first lens group, reference symbol r b represents the radius of curvature of the rearmost surface of the first lens group, and reference symbol r c represents the radius of curvature of the surface on the object side of the negative lens in the second lens group.

Claim 6

A compact zoom lens system according to claim 2 further fulfilling the conditions (5) through (8) shown below: (5) 0.1<d/f 1 <0.5 (6) 0.1<r a /f 1 <0.7 (7) 0.1<|r b |/f 1 <1.0, r b <0 (8) 0.2<r c /f 2 <0.7, r c <0 where, reference symbol d represents the sum of thicknesses of positive lenses arranged between the negative lens in the first lens group and stop, reference symbol r a represents the radius of curvature of the surface on the image side of the negative lens in the first lens group, reference symbol r b represents the radius of curvature of the rearmost surface of the first lens group, and reference symbol r c represents the radius of curvature of the surface on the object side of the negative lens in the second lens group.

Claim 7

A compact zoom lens system according to claim 3 further fulfilling the conditions (5) through (8) shown below: (5) 0.1<d/f 1 <0.5 (6) 0.1<r a /f 1 <0.7 (7) 0.1<|r b |/f 1 <1.0, r b <0 (8) 0.2<r c /f 2 <0.7 r c <0 Where, reference symbol d represents the sum of thicknesses of positive lenses arranged between the negative lens in the first lens group and stop, reference symbol r a represents the radius of curvature of the surface on the image side of the negative lens in the first lens group, reference symbol r b represents the radius of curvature of the rearmost surface of the first lens group, and reference symbol r c represents the radius of curvature of the surface on the object side of the negative lens in the second lens group.

Claim 8

A compact zoom lens system according to claim 4 wherein said first lens group comprises a positive lens, a negative lens and a positive lens in the order from the object side, said compact zoom lens system having the following numerical data: ______________________________________ f = 41.2˜58.2, F/4.6˜F/6.6 ______________________________________ r.sub.1 = 13.086 d.sub.1 = 41.9 n.sub.1 = 1.66680 ν.sub.1 = 33.04 r.sub.2 = 61.292 d.sub.2 = 1.66 r.sub.3 = -62.003 d.sub.3 = 1.20 n.sub.2 = 1.84666 ν.sub.2 = 23.78 r.sub.4 = 9.800 d.sub.4 = 2.95 r.sub.5 = 18.293 d.sub.5 = 9.83 n.sub.3 = 1.62004 ν.sub.3 = 36.25 r.sub.6 = -15.273 d.sub.6 = 2.00 r.sub.7 = ∞ (stop) d.sub.7 = D r.sub.8 = 206.959 d.sub.8 = 2.93 n.sub.4 = 1.51823 ν.sub.4 = 58.96 r.sub.9 = -28.114 d.sub.9 = 2.89 r.sub.10 = -18.949 d.sub.10 = 1.40 n.sub.5 = 1.83400 ν.sub.5 = 37.16 r.sub.11 = 157.752 D = 11.510˜2.500 f.sub.1 /f.sub.w = 0.78, |f.sub.2 |/f.sub.w = 0.96 D.sub.w /f.sub.w = 0.28, P.sub.w /f.sub.w = 0.269 d/f.sub.1 = 0.31, r.sub.a /f.sub.1 = 0.30 r.sub.b /f.sub.1 = -0.47, r.sub.c /f.sub.2 = 0.48 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represet thicknesses of respective lenses and airspaces between respective lenses, reference symbol n 1 , n 2 , . . . respectively represent refractive indices of respective lenses and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 9

A compact zoom lens system according to claim 4 wherein said first lens group comprises a positive lens, a negative lens, positive lens and a positive lens in the order from the object side, said compact zoom lens system having the following numerical data: ______________________________________ f = 41.2˜58.2, F/4.6˜F/6.6 ______________________________________ r.sub.1 = 14.909 d.sub.1 = 4.20 n.sub.1 = 1.73520 ν.sub.1 = 41.08 r.sub.2 = 48.227 d.sub.2 = 1.66 r.sub.3 = -35.192 d.sub.3 = 1.00 n.sub.2 = 1.80518 ν.sub.2 = 25.43 r.sub.4 = 15.566 d.sub.4 = 3.56 r.sub.5 = 48.548 d.sub.5 = 2.40 n.sub.3 = 1.56732 ν.sub.3 = 42.83 r.sub.6 = -65.407 d.sub.6 = 0.15 r.sub.7 = 47.955 d.sub.7 = 3.00 n.sub.4 = 1.59270 ν.sub.4 = 35.29 r.sub.8 = -20.866 d.sub.8 = 2.00 r.sub.9 = ∞ (stop) d.sub.9 = D r.sub.10 = -620.617 d.sub.10 = 2.96 n.sub.5 = 1.53172 ν.sub.5 = 48.90 r.sub.11 = 21.732 d.sub.11 = 2.44 r.sub.12 = -16.588 d.sub.12 = 1.10 n.sub.6 = 1.83400 ν.sub.6 = 37.16 r.sub.13 = 1107.775 D = 11.678˜2.353 f.sub.1 /f.sub.w = 0.78, |f.sub.2 |/f.sub.w = 0.99 D.sub.w /f.sub.w = 0.28, P.sub.w /f.sub.w = 0.269 d/f.sub.1 = 0.17, r.sub.a /f.sub.1 = 0.48 r.sub.b /f.sub.1 = -0.65, r.sub.c /f.sub.2 = 0.41 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of ourvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represet thicknesses of respective lenses and airspace between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 10

A compact zoom lens system according to claim 4 wherein said first lens group comprises a positive lens, a negative lens and a positive lens in the order from the object side, said compact zoom lens system having the following numerical data: ______________________________________ f = 41.2˜58.2, F/4.6˜F/6.6 ______________________________________ r.sub.1 = 13.269 d.sub.1 = 4.50 n.sub.1 = 1.72825 ν.sub.1 = 28.46 r.sub.2 = 46.496 d.sub.2 = 1.34 r.sub.3 = -111.600 d.sub.3 = 1.00 n.sub.2 = 1.80518 ν.sub.2 = 25.43 r.sub.4 = 8.804 d.sub.4 = 3.15 r.sub.5 = 16.153 d.sub.5 = 10.39 n.sub.3 = 1.54739 ν.sub.3 = 53.55 r.sub.6 = -13.748 d.sub.6 = 1.50 r.sub.7 = ∞ (stop) d.sub.7 = D r.sub.8 = -89.808 d.sub.8 = 3.00 n.sub.4 = 1.63980 ν.sub.4 = 34.48 r.sub.9 = -23.296 d.sub.9 = 3.13 r.sub.10 = -16.391 d.sub.10 = 1.10 n.sub.5 = 1.83400 ν.sub.5 = 37.16 r.sub.11 = -644.321 D = 11.762˜3.263 f.sub.1 /f.sub.w = 0.77, |f.sub.2 |/f.sub.w = 0.92 D.sub.w /f.sub.w = 0.29, P.sub.w /f.sub.w = 0.274 d/f.sub.1 = 0.33, r.sub.a /f.sub.1 = 0.42 r.sub.b /f.sub.1 = -0.44, r.sub.c /f.sub.2 = 0.43 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 11

A compact zoom lens system according to claim 6 wherein said first lens group comprises a positive lens, a negative lens and a positive lens in the order from the object side, said compact zoom lens system having the following numerical data: ______________________________________ f = 41.2˜58.2, F/4.6˜F/6.6 ______________________________________ r.sub.1 = 14.129 d.sub.1 = 4.16 n.sub.1 = 1.61293 ν.sub.1 = 37.00 r.sub.2 = 72.611 d.sub.2 = 1.51 r.sub.3 = -42.509 d.sub.3 = 1.79 n.sub.2 = 1.80518 ν.sub.2 = 25.43 r.sub.4 = 13.287 d.sub.4 = 1.71 r.sub.5 = 23.101 d.sub.5 = 11.48 n.sub.3 = 1.72342 ν.sub.3 = 37.95 r.sub.6 = -20.449 d.sub.6 = 0.71 r.sub.7 = ∞ (stop) d.sub.7 = D r.sub.8 = 33.696 d.sub.8 = 3.20 n.sub.4 = 1.49109 ν.sub.4 = 57.00 r.sub.9 = -32.105 (aspherical surface) d.sub.9 = 2.73 r.sub.10 = -18.890 d.sub.10 = 1.00 n.sub.5 = 1.81600 ν.sub.5 = 46.62 r.sub.11 = 52.554 D = 11.389˜0.658 f.sub.1 /f.sub.w = 0.84, |f.sub.2 |/f.sub.w = 1.06 D.sub.w /f.sub.w = 0.28, P.sub.w /f.sub.w = 0.249 d/f.sub.1 = 0.33, r.sub.a /f.sub.1 = 0.38 r.sub.b /f.sub.1 = -0.59, r.sub.c /f.sub.2 = 0.43 aspherical surface coefficients B = 0, E = -0.22901 × 10.sup.-4 F = -0.55448 × 10.sup.-7, G = -0.14686 × 10.sup.-8 H = 0.16617 × 10.sup.-10 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 12

A compact zoom lens system according to claim 5 wherein said first lens group comprises a positive lens, a negative lens and a positive lens in the order from the object side, said compact zoom lens system having the following numerical data: ______________________________________ f = 41.2˜58.2, F/4.6˜F/6.6 ______________________________________ r.sub.1 = 15.546 d.sub.1 = 4.85 n.sub.1 = 1.70154 ν.sub.1 = 41.24 r.sub.2 = 66.673 d.sub.2 = 1.66 r.sub.3 = -54.063 d.sub.3 = 1.36 n.sub.2 = 1.80518 ν.sub.2 = 25.43 r.sub.4 = 14.903 (aspherical surface) d.sub.4 = 3.96 r.sub.5 = 26.300 d.sub.5 = 6.11 n.sub.3 = 1.59551 ν.sub.3 = 39.21 r.sub.6 = -17.395 d.sub.6 = 1.50 r.sub.7 = ∞ (stop) d.sub.7 = D r.sub.8 = -385.202 d.sub.8 = 2.00 n.sub.4 = 1.51742 ν.sub.4 = 52.41 r.sub.9 = -24.449 d.sub.9 = 2.89 r.sub.10 = -18.103 d.sub.10 = 1.00 n.sub.5 = 1.79952 ν.sub.5 = 42.24 r.sub.11 = 1094.867 D = 11.207˜0.839 f.sub.1 /f.sub.w = 0.80, |f.sub.2 |/f.sub.w = 1.08 D.sub.w /f.sub.w = 0.27, P.sub.w /f.sub.w = 0.265 d/f.sub.1 = 0.19, r.sub.a /f.sub.1 = 0.45 r.sub.b /f.sub.1 = -0.53, r.sub.c /f.sub.2 = 0.41 aspherical surface coefficients B = 0, E = -0.26854 × 10.sup.-4 F = 0.45187 × 10.sup.-6, G = 0.92832 × 10.sup.-8 H = -0.14695 × 10.sup.-9 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.