Telephoto lens system

Claim 2

A telephoto lens system comprising: a front lens group of a positive refractive power fixed on the optical axis; and a rear lens group of a negative refractive power consisting, from the object to the image side, of a first positive subunit fixed on the optical axis, a second negative subunit movable along the optical axis and a third positive subunit fixed on the optical axis, the second negative subunit being movable toward the image side for focusing to a close object.

Claim 3

The invention of claim 1, wherein the object side end surface of the first positive subunit is concave.

Claim 4

The invention of claim 2, wherein the lens system fulfills the following condition: 0.6<|φ'.sub.II-1 |/φ.sub.I <2.5 wherein: φ' II-1 represents the refractive power of the object side end surface of the first subunit; and φ I represents the refractive power of the front lens group.

Claim 5

The invention of claim 3, wherein the lens system further fulfills the following condition: 0.2f<F.sub.II-3 <0.7f wherein: F II-3 represents the focal length of the third positive subunit; and f represents the focal length of the whole lens system.

Claim 6

The invention of claim 4, wherein the range for F II-3 is as follows: 0.25f<F.sub.II-3 <0.65f.

Claim 7

The invention of claim 5, wherein the lens system further fulfills the following condition: 0.3<φ".sub.II-3 /|φ.sub.II-2 |<0.7 wherein: φ" II-3 represents the refractive power of the image side end surface of the third positive subunit; and φ II-2 represents the refractive power of the second negative subunit.

Claim 8

The invention of claim 6, wherein the range for φ" II-3 /|φ II-2 | is as follows: 0.31<φ".sub.II-3 /|φ.sub.II-2 |<0.68.

Claim 9

The invention of claim 7, wherein the lens system further fulfills the following conditions: |F.sub.I;II-1;II-2 |>2.5 f 0.4<D/F.sub.I <0.7 wherein: F I;II-1;II-2 represents the focal length of a part of the lens system defined between the front surface of the front lens group and the image side end surface of the second negative subunit upon infinity focusing; D represents the axial distance between the front surface of the front lens group and the object side end surface of the rear lens group; and F I represents the focal length of the front lens group.

Claim 10

The invention of claim 1, wherein the lens system fulfills the following condition: 0.25f<F.sub.II-3 <0.65f wherein: F II-3 represents the focal length of the third positive subunit; and f represents the focal length of the whole lens system.

Claim 11

The invention of claim 9, wherein the lens system further fulfills the following condition: 0.31<φ".sub.II-3 /|φ.sub.II-2 |<0.68 wherein: φ" II-3 represents the refractive power of the image side end surface of the third positive subunit; and φ II-2 represents the refractive power of the second negative subunit.

Claim 12

A telephoto lens system comprising: a front lens group of a positive refractive power fixed on the optical axis; and a rear lens group of a negative refractive power consisting of, from the object to the image side, a first fixed subunit, a second movable subunit and a third fixed subunit, the second subgroup being movable toward the image side for focusing to a close object, wherein the lens system fulfills the following condition: 0.25f<F.sub.II-3 <0.65f wherein F II-3 represents the focal length of the third fixed subunit; and f represents the focal length of the whole lens system.

Claim 13

A telephoto lens system comprising: a front lens group of a positive refractive power fixed on the optical axis; and a rear lens group of a negative refractive power consisting of, from the object to the image side, a first fixed subunit, a second movable subunit and a third fixed subunit, the second subgroup being movable toward the image side for focusing to a close object, wherein the lens system fulfills the following condition: 0.25f<F.sub.II-3 <0.65f wherein F II-3 represents the focal length of the third fixed subunit; and f represents the focal length of the whole lens system.

Claim 14

The invention of claim 11, wherein the lens system further fulfills the following condition: 0.31<φ".sub.II-3 /|φ.sub.II-2 |<0.68 wherein: φ" II-3 represents the refractive power of the image side end surface of the third fixed subunit; and φ II-2 represents the refractive power of the second movable subunit.

Claim 15

The invention of claim 12, wherein the first subunit consists of a negative meniscus lens element concave to the object side and a positive lens element.

Claim 16

The invention of claim 12, wherein the first subunit consists of a positive meniscus lens element concave to the object side.

Claim 17

The invention of claim 12, wherein the first subunit consists of a positive meniscus doublet concave to the object side.

Claim 18

A telephoto lens system comprising: a front lens group of a positive refractive power; a rear lens group of a negative refractive power consisting, from the object to the image side, of a first subunit having a concave object side end surface, a second subunit and a third subunit, wherein the lens system fulfills the following condition: 0.6<|φ'.sub.II-1 |/φ.sub.I <2.5 wherein: φ' II-1 represents the refractive power of the object side end surface of the first subunit; and φ I represents the refractive power of the front lens group.

Claim 19

A telephoto lens system comprising: a front lens group of a positive refractive power; a rear lens group of a negative refractive power consisting, from the object to the image side, of a first subunit having a concave object side end surface, a second subunit and a third subunit, wherein the lens system fulfills the following condition: 0.6<|φ'.sub.II-1 |/φ.sub.I <2.5 wherein: φ' II-1 represents the refractive power of the object side end surface of the first subunit; and φ I represents the refractive power of the front lens group.

Claim 20

The invention of claim 16, wherein the lens system further fulfills the following condition: 0.25f<F.sub.II-3 <0.65f wherein: F II-3 represents the focal length of the third subunit; and f represents the focal length of the whole lens system.

Claim 21

The invention of claim 17, wherein the lens system further fulfills the following condition: 0.31<φ".sub.II-3 /|φ.sub.II-2 |<0.68 wherein: φ" II-3 represents the refractive power of the image side end surface of the third subunit; and φ II-2 represents the refractive power of the second subunit.

Claim 22

The invention of claim 18, wherein the lens system further fulfills the following conditions: |F.sub.I;II-1;II-2 |>2.5f 0.4<D/F.sub.I <0.7 wherein: F I;II-1;II-2 represents the focal length of a part of the lens system defined between the front surface of the front lens group and the image side end surface of the second subunit upon infinity focusing; D represents the axial distance between the front surface of the front lens group and the object side end surface of the rear lens group; and F I represents the focal length of the front lens group.

Claim 23

A telephoto lens system according to the following parameters: ______________________________________ f = 295.0 F.sub.No. = 2.9 Radius of Axial Refractive Abbe Curvature Distance Index Number ______________________________________ ##STR17## r.sub.1r.sub.2r.sub.3r.sub.4r.sub.5r.sub.6 140.872-447.513115.956-701.292-474.476170.954 d.sub.1d.sub.2d.sub.3d.sub.4d.sub.5 16.000.4214.502.523.70 N.sub.1N.sub.2N.sub.3 1.495201.495201.68150 ν.sub.1ν.sub.2ν.sub. 2 79.7479.7436.64 d.sub.6 78.00 ##STR18## r.sub. 7r.sub.8r.sub.9r.sub.10r.sub.11r.sub.12r.sub.13r.sub.14r.su b.15r.sub.16r.sub.17r.sub.18 -131.706-216.400111.332508.815-1256.8-65.525366.046-228.6336 6.7591084.8-42.017-79.965. d.sub.7d.sub.8d.sub.9d.sub.10d.sub.11d.sub.12d.sub .13d.sub.14d.sub.15d.sub.16d.sub.17 2.501.354.003.006.501.853.151.7022.007.001.60 N.sub.4N.sub.5N.sub.6N.sub.7N.sub.8N.sub .9N.sub.10 1.654461.603111.717361.603111.67000 .603111.65446 ν.sub.4ν.sub.5ν.sub. ν.sub.7ν.sub.8ν.sub.9 ν.sub.10 33.86 60.7429.4260.7457.0 760.7433.86 ______________________________________

Claim 24

A telephoto lens system according to the following parameters: ______________________________________ f = 295.0 F.sub.No. = 2.9 Radius of Axial Refractive Abbe Curvature Distance Index Number ______________________________________ ##STR17## r.sub.1r.sub.2r.sub.3r.sub.4r.sub.5r.sub.6 140.872-447.513115.956-701.292-474.476170.954 d.sub.1d.sub.2d.sub.3d.sub.4d.sub.5 16.000.4214.502.523.70 N.sub.1N.sub.2N.sub.3 1.495201.495201.68150 ν.sub.1ν.sub.2ν.sub. 2 79.7479.7436.64 d.sub.6 78.00 ##STR18## r.sub. 7r.sub.8r.sub.9r.sub.10r.sub.11r.sub.12r.sub.13r.sub.14r.su b.15r.sub.16r.sub.17r.sub.18 -131.706-216.400111.332508.815-1256.8-65.525366.046-228.6336 6.7591084.8-42.017-79.965. d.sub.7d.sub.8d.sub.9d.sub.10d.sub.11d.sub.12d.sub .13d.sub.14d.sub.15d.sub.16d.sub.17 2.501.354.003.006.501.853.151.7022.007.001.60 N.sub.4N.sub.5N.sub.6N.sub.7N.sub.8N.sub .9N.sub.10 1.654461.603111.717361.603111.67000 .603111.65446 ν.sub.4ν.sub.5ν.sub. ν.sub.7ν.sub.8ν.sub.9 ν.sub.10 33.86 60.7429.4260.7457.0 760.7433.86 ______________________________________