Compact zoom lens system

Claim 2

A compact zoom lens system, comprising: four lens groups, first, second, third and fourth, wherein said first lens group has positive refractive power and is arranged as a compensator, said second lens group has negative refractive power and is arranged as a variator, said third lens group has positive refractive power and is arranged as a variator, said fourth lens group has negative refractive power and is arranged in the rearmost position; said first, second and third lens groups constituting a zooming sub-system having positive refractive power as a whole; said compact zoom lens system permitting movement of said second lens group and said third lens group along the optical axis for the purpose of zooming; said zoom lens system moving said first lens group in order to compensate for the movement of image surface caused when said second lens group and said third lens group are moved, wherein said first lens group and said third lens group are moved toward the object side, said second lens group are moved toward the image side and said fourth lens group are kept fixed when the focal length thereof is varied from the teleposition to the wide position, said zoom lens system being further arranged to fulfill the following conditions where reference symbol V 2 represents the magnification ratio of said second lens group between the telephoto and wide positions, and reference symbol V 3 represents the magnification ratio of said third lens group between the telephoto and wide positions

Claim 3

5<V 2 /V 3 <2.0.

Claim 4

5<V 2 /V 3 <2.0.

Claim 5

A compact zoom lens system according to claim 1 further comprising an aperture stop fixed at a pre-determined position independently of the movements of said first lens group, said second lens group and said third lens group given at the time of zooming.

Claim 6

A compact zoom lens system according to claim 1 further comprising an aperture stop arranged to be moved together with said third lens group at the time of zooming.

Claim 7

A compact zoom lens system according to claim 1 wherein said first lens group comprises at least three lens elements including a negative lens, said second lens group comprises four lens elements including two negative lenses, said third lens group comprises five lens elements including at least one negative lens, and said fourth lens group comprises a positive lens and a negative lens.

Claim 8

A compact zoom lens system according to claim 4 wherein said first lens group comprises a cemented doublet, which consists of a negative lens and a positive lens, and a positive lens.

Claim 9

A compact zoom lens system according to claim 5 arranged to be focused on an object at an extremely short distance by moving said third lens group toward the object side.

Claim 10

A compact zoom lens system according to claim 1 arranged to be focused on an object at an extremely short distance by moving said fourth lens group toward the image side.

Claim 11

A compact zoom lens system according to claim 1 arranged to be focused on an object at an extremely short distance by simultaneously moving said third lens group toward the object side and said fourth lens group toward the image side.

Claim 12

A compact zoom lens system according to claim 5 arranged to be focused on an object at an extremely short distance by simultaneously moving said third lens group toward the object side and said fourth lens group toward the image side.

Claim 13

A compact zoom lens system according to claim 2 further arranged to fulfill the following condition where reference symbol B 4 represents the magnification of said fourth lens group 1<B 4 <1.5.

Claim 14

A compact zoom lens system according to claim 3 further arranged to fulfill the following condition where reference symbol B 4 represents the magnification of said fourth lens group 1<B 4 <1.5.

Claim 15

A compact zoom lens system according to claim 4 further arranged to fulfill the following condition where reference symbol B 4 represents the magnification of said fourth lens group 1<B 4 <1.5.

Claim 16

A compact zoom lens system according to claim 5 further arranged to fulfill the following condition where reference symbol B 4 represents the magnification of said fourth lens group 1<B 4 <1.5.

Claim 17

A compact zoom lens system according to claim 6 further arranged to fulfill the following condition where reference symbol B 4 represents the magnification of said fourth lens group 1<B 4 <1.5.

Claim 18

A compact zoom lens system according to claim 7 further arranged to fulfill the following condition B 4 represents the magnification of said fourth lens group 1<B 4 <1.5.

Claim 19

A compact zoom lens system according to claim 8 further arranged to fulfill the following condition where reference symbol B 4 represents the magnification of said fourth lens group 1<B 4 <1.5.

Claim 20

A compact zoom lens system according to claim 3 wherein said first lens group comprises a negative lens, positive lens and a positive lens, said second lens group comprises a positive lens, a negative lens, a negative lens and a positive lens, said third lens group comprises a positive lens, a positive lens, a positive lens, a negative lens and a positive lens, and said fourth lens group comprises a positive lens and a negative lens, said compact zoom lens system being further arranged to have the following numerical data: ______________________________________ f = 61.5˜175.5, F 4 ______________________________________ r.sub.1 = 106.48 d.sub.1 = 2.5 n.sub.1 = 1.80518 ν.sub.1 = 25.4 r.sub.2 = 65.71 d.sub.2 = 1.2 r.sub.3 = 59.88 d.sub.3 = 7.5 n.sub.2 = 1.47069 ν.sub.2 = 67.4 r.sub.4 = -483.33 d.sub.4 = 0.15 r.sub.5 = 61.68 d.sub.5 = 5.2 n.sub.3 = 1.51633 ν.sub.3 = 64.2 r.sub.6 = 118.86 d.sub.6 (variable) r.sub.7 = -1825.47 d.sub.7 = 3.8 n.sub.4 = 1.617 ν.sub.4 = 62.8 r.sub.8 = -70.26 d.sub.8 = 0.12 r.sub.9 = 255.67 d.sub.9 = 1.48 n.sub.5 = 1.7725 ν.sub.1 = 49.7 r.sub.10 = 35.46 d.sub.10 = 5.2 r.sub.11 = -26.29 d.sub.11 = 1.48 n.sub.6 = 1.7859 ν.sub.6 = 44.2 r.sub.12 = 49.78 d.sub.12 = 1.4 r.sub.13 = 61.75 d.sub.13 = 4.6 n.sub.7 = 1.80518 ν.sub.7 = 25.4 r.sub.14 = -72.01 d.sub.14 (variable) r.sub.15 = 146.01 d.sub.15 = 3.5 n.sub.8 = 1.48749 ν.sub.8 = 70.2 r.sub.16 = -93.72 d.sub.16 = 0.12 r.sub.17 = 53.04 d.sub.17 = 4.4 n.sub.9 = 1.48749 ν.sub.9 = 70.2 r.sub.18 = -2191.73 d.sub.18 = 0.12 r.sub.19 = 23.72 d.sub.19 = 5.45 n.sub.10 = 1.48749 ν.sub.10 = 70.2 r.sub.20 = 52.78 d.sub.20 = 5.2 r.sub.21 = 127.72 d.sub.21 = 1.8 n.sub.11 = 1.80518 ν.sub.11 = 25.4 r.sub.22 = 23.39 d.sub.22 = 2.2 r.sub.23 = 51.19 d.sub.23 = 4.5 n.sub.12 = 1.64769 ν.sub.12 = 33.8 r.sub.24 = -79.16 d.sub.24 (variable) r.sub.25 = 210.61 d.sub.25 = 4 n.sub.13 = 1.65128 ν.sub.13 = 38.3 r.sub.26 = 257.53 d.sub.26 = 4.5 r.sub.27 = -35.09 d.sub.27 = 2 n.sub.14 = 1.7859 ν.sub.14 = 44.2 r.sub.28 = -56.42 ______________________________________ f d.sub.6 d.sub.14 d.sub.24 ______________________________________ 61.5 4.091 34.895 5.43 103.9 28.48 20.671 8.158 175.5 38.591 0.654 18.064 ______________________________________ L.sub.W = 171.2, L.sub.T = 184.1, f.sub.B = 54.4 f.sub.1 = 120, f.sub.2 = -34.5, f.sub.3 = 41, f.sub.4 = -125, V.sub.2 /V.sub.3 = 0.7623, β.sub.4 = 1.27 ______________________________________ wherein reference symbols r 1 through r 28 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 27 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 14 respectively represent refractive indices of respective lenses, reference symbols ν 1 through ν 14 respectively represent Abbe's numbers of respective lenses, reference symbol L W represents the overall length of the lens system in the wide position, reference symbol L T represents the overall length of the lens system in the teleposition, and reference symbol f B represents the back focal length of the lens system.

Claim 21

A compact zoom lens system according to claim 3 wherein said first lens group comprises a negative lens, positive lens and a positive lens, said second lens group comprises a positive lens, a negative lens, a negative lens and a positive lens, said third lens group comprises a positive lens, a positive lens, a positive lens, a negative lens and a positive lens, and said fourth lens group comprises a positive lens and a negative lens, said compact zoom lens system being further arranged to have the following numerical data: ______________________________________ f = 61.5˜175.5, F 4 ______________________________________ r.sub.1 = 109.68 d.sub.1 = 2.5 n.sub.1 = 1.78472 ν.sub.1 = 25.7 r.sub.2 = 56.36 d.sub.2 = 2 r.sub.3 = 59.15 d.sub.3 = 6 n.sub.2 = 1.56873 ν.sub.2 = 63.2 r.sub.4 = 195.29 d.sub.4 = 0.15 r.sub.5 = 55.98 d.sub.5 = 4.7 n.sub.3 = 1.56965 ν.sub.3 = 49.3 r.sub.6 = 253.84 d.sub.6 (variable) r.sub.7 = -377.57 d.sub.7 = 3.8 n.sub.4 = 1.6228 ν.sub.4 = 57.1 r.sub.8 = -68.13 d.sub.8 = 0.12 r.sub.9 = 54.53 d.sub.9 = 1.48 n.sub.5 = 1.7859 ν.sub.5 = 44.2 r.sub.10 = 27.34 d.sub.10 = 5.6 r.sub.11 = -25.31 d.sub.11 = 1.48 n.sub.6 = 1.7725 ν.sub.6 = 49.7 r.sub.12 = 55.99 d.sub.12 = 1.2 r.sub.13 = 64.98 d.sub.13 = 4.1 n.sub.7 = 1.84666 ν.sub.7 = 23.9 r.sub.14 = -119.67 d.sub.14 (variable) r.sub.15 = -396.99 d.sub.15 = 3.8 n.sub.8 = 1.48749 ν.sub.8 = 70.2 r.sub.16 = -44.98 d.sub.16 = 0.12 r.sub.17 = 85.66 d.sub.17 = 3 n.sub.9 = 1.48749 ν.sub.9 = 70.2 r.sub.18 = -207.78 d.sub.18 = 0.12 r.sub.19 = 21.78 d.sub.19 = 6.45 n.sub.10 = 1.48749 ν.sub.10 = 70.2 r.sub.20 = 48.17 d.sub.20 = 5.2 r.sub.21 = -3970.3 d.sub.21 = 1.8 n.sub.11 = 1.78472 ν.sub.11 = 25.7 r.sub.22 = 24.03 d.sub.22 = 2.2 r.sub.23 = 41.78 d.sub.23 = 4.5 n.sub.12 = 1.64769 ν.sub.12 = 33.8 r.sub.24 = -72.94 d.sub.24 (variable) r.sub.25 = 1192.6 d.sub.25 = 4 n.sub.13 = 1.5927 ν.sub.13 = 35.3 r.sub.26 = -168.94 d.sub.26 = 3 r.sub.27 = -42.25 d.sub.27 = 2 n.sub.14 = 1.7725 ν.sub.14 = 49.7 r.sub.28 = -127.95 ______________________________________ f d.sub.6 d.sub.14 d.sub.24 ______________________________________ 61.5 6.141 35.273 5.746 103.888 27.191 19.392 11.362 175.5 42.078 2.137 18.072 ______________________________________ L.sub.W = 170, L.sub.T = 185.3, f.sub.B = 53.7 f.sub.1 = 124, f.sub.2 = -34.5, f.sub.3 = 40 f.sub.4 = -125, V.sub.2 /V.sub.3 = 0.867, β.sub.4 = 1.32 ______________________________________ wherein reference symbols r 1 through r 28 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 27 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 14 respectively represent refractive indices of respective lenses, reference symbols ν 1 through ν 14 respectively represent Abbe's numbers of respective lenses, reference symbol L W represents the overall length of the lens system in the wide position, reference symbol L T represents the overall length of the lens system in the teleposition, and reference symbol f B represents the back focal length of the lens system.

Claim 22

A compact zoom lens system, comprising: four lens groups, first, second, third and fourth, wherein said first lens group has positive refractive power and is arranged as a compensator, said second lens group has negative refractive power and is arranged as a variator, said third lens group has positive refractive power and is arranged as a variator, said fourth lens group has negative refractive power and is arranged as the rearmost group of the lens system; said first, second and third lens groups constituting a zooming sub-system having positive refractive power as a whole; said fourth lens group being kept fixed when the focal length thereof is varied from the teleposition to the wide position; said compact zoom lens system permitting movement of said second lens group and said third lens group along the optical axis for the purpose of zooming; and said zoom lens system moving said first lens group in order to compensate for the movement of image surface caused when said second lens group and said third lens group are moved.

Claim 23

A compact zoom lens system, comprising: four lens groups, first, second, third and fourth, wherein said first lens group has positive refractive power and is arranged as a compensator, said second lens group has negative refractive power and is arranged as a variator, said third lens group has positive refractive power and is arranged as a variator, said fourth lens group has negative refractive power and is arranged as the rearmost group of the lens system; said first, second and third lens groups constituting a zooming sub-system having positive refractive power as a whole; said fourth lens group being kept fixed when the focal length thereof is varied from the teleposition to the wide position; said compact zoom lens system permitting movement of said second lens group and said third lens group along the optical axis for the purpose of zooming; and said zoom lens system moving said first lens group in order to compensate for the movement of image surface caused when said second lens group and said third lens group are moved.

Claim 24

A compact zoom lens system according to claim 19, wherein: said first lens group and said second lens group are moved toward the object side and said second lens group is moved toward the image side when the focal length thereof is varied from the teleposition to the wide position.

Claim 25

A compact zoom lens system, comprising: four lens groups, first, second, third and fourth, wherein said first lens group has positive refractive power and is arranged as a compensator, said second lens group has negative refractive power and is arranged as a variator, said third lens group has positive refractive power and is arranged as a variator, said fourth lens group has negative refractive power and is arranged in the rearmost position, said first, second and third lens groups constituting a zooming sub-system having positive refractive power as a whole; said compact zoom lens system permitting movement of said second lens group and said third lens group along the optical axis for the purpose of zooming; said zoom lens system moving said first lens group in order to compensate for the movement of image surface caused when said second lens group and said third lens group are moved, wherein said first lens group and said third lens group are moved toward the object side, said second lens group are moved toward the image side and said fourth lens group are kept fixed when the focal length thereof is varied from the teleposition to the wide position, said zoom lens system further arranged to fulfill the following condition where reference sybol β 4 represents the magnification of said fourth lens group

Claim 26

A compact zoom lens system, comprising: four lens groups, first, second, third and fourth, wherein said first lens group has positive refractive power and is arranged as a compensator, said second lens group has negative refractive power and is arranged as a variator, said third lens group has positive refractive power and is arranged as a variator, said fourth lens group has negative refractive power and is arranged in the rearmost position, said first, second and third lens groups constituting a zooming sub-system having positive refractive power as a whole; said compact zoom lens system permitting movement of said second lens group and said third lens group along the optical axis for the purpose of zooming; said zoom lens system moving said first lens group in order to compensate for the movement of image surface caused when said second lens group and said third lens group are moved, wherein said first lens group and said third lens group are moved toward the object side, said second lens group are moved toward the image side and said fourth lens group are kept fixed when the focal length thereof is varied from the teleposition to the wide position, said zoom lens system further arranged to fulfill the following condition where reference sybol β 4 represents the magnification of said fourth lens group

Claim 27

<β.sub. < 1. 5.

Claim 28

<β.sub. < 1. 5.