Photographic lens of continuously variable focal length

Claim 2

A photographic lens of continuously variable focal length consisting of four lens groups comprising, in sequence from front to rear along an optical axis: (a) a first group (A) of converging refractive power; (b) a second group (B) of diverging refractive power; (c) a third group (C) of converging refractive power; and (d) a fourth group (D) of converging refractive power; (e) said lens groups being so dimensioned and arranged that a change in the focal length is effected by displacing diverging lens group B and converging lens group C along the optical axis relative to each other and relative to groups A and D while maintaining a constant back focus; said lens being characterized by the features that: (f) an iris diaphragm (BL) is located between group B and group C; (g) the third lens group C has a focal length which is numerically greater than the focal length of lens group B by a factor not less than 1.42 and not more than 1.73; (h) the fourth less group D is formed of two parts (D 1 and D 2 ) separated from each other by a clear air space; (i) the first part D 1 of the fourth lens group is of negative power; (j) the second part D 2 of the fourth group is of positive power; (k) said first part D 1 comprises a compound member formed of at least two elements; and (l) the focal length of said first part D 1 is numerically greater than the focal length of the third lens group C by a factor not less than 1.16 and not more than 1.42; the respective elements of the lens being dimensioned substantially in accordance with the data in the following table, the respective symbols in the table having the meanings explained in the accompanying specification: ______________________________________ Lens Thicknesses element Radii and Spacings n.sub.d V.sub.d ______________________________________ r.sub.1 + 421.790 I d.sub.1 3.0 1.75520 27.58 r.sub.2 + 64.470 d.sub.2 1.8 r.sub.3 + 69.282 II d.sub.3 10.5 1.69100 54.71 r.sub.4 - 453.140 d.sub.4 0.1 r.sub.5 + 64.470 III d.sub.5 7.0 1.69100 54.71 r.sub.6 + 339.850 0.5 d.sub.6 40.523 53.897 r.sub.7 + 113.824 IV d.sub.7 1.2 1.71300 53.83 r.sub.8 + 17.278 V d.sub.8 8.0 1.71300 53.83 r.sub.9 - 48.000 d.sub.9 1.0 r.sub.10 + 25.664 VI d.sub.10 3.2 1.75520 27.58 r.sub. 11 + 69.282 d.sub.11 2.0 r.sub.12 + 37.585 VII d.sub.12 3.0 1.75520 27.58 r.sub.13 + 79.431 55.797 d.sub.13 15.774 2.400 BL r.sub.14 ∞ iris diaphragm 15.245 d.sub.14 4.749 4.829 r.sub.15 + 1122.000 VIII d.sub.15 2.0 1.805518 25.43 r.sub.16 + 32.545 IX d.sub.16 8.0 1.61272 58.63 r.sub.17 - 57.460 d.sub.17 0.1 r.sub.18 + 99.283 X d.sub.18 4.2 1.71300 53.83 r.sub.19 - 172.776 d.sub.19 0.1 r.sub.20 + 127.721 XI d.sub.20 4.4 1.71300 53.83 r.sub.21 - 68.293 2.528 d.sub.21 13.024 12.944 r.sub.22 - 29.853 XII d.sub.22 1.0 1.71300 53.83 r.sub.23 + 20.834 XIII d.sub.23 4.5 1.76180 26.95 r.sub.24 + 227.110 d.sub.24 10.7 r.sub.25 - 1729.000 XIV d.sub.25 3.2 1.69100 54.71 r.sub.26 - 35.737 d.sub.26 4.1 r.sub.27 + 112.204 XV d.sub.27 2.2 1.80518 25.43 r.sub.28 + 32.315 d.sub.28 2.7 r.sub.29 + 82.939 XVI d.sub.29 3.3 1.46450 65.77 r.sub.30 - 35.228 d.sub.30 0.1 r.sub.31 + 97.166 XVII d.sub.31 4.1 1.60311 60.60 r.sub.32 - 22.386 XVIII d.sub.32 1.5 1.80518 25.43 r.sub.33 - 92.387 Back focus s' = 28.53 ______________________________________

Claim 3

A photographic lens of continuously variable focal length consisting of four lens groups comprising, in sequence from front to rear along an optical axis: (a) a first group (A) of converging refractive power; (b) a second group (B) of diverging refractive power; (c) a third group (C) of converging refractive power; and (d) a fourth group (D) of converging refractive power; (e) said lens group being so dimensioned and arranged that a change in the focal length is effected by displacing diverging lens group B and converging lens group C along the optical axis relative to each other and relative to groups A and D while maintaining a constant back focus; said lens being characterized by the features that: (f) an iris diaphragm (BL) is located between group B and group C; (g) the third lens group C has a focal length which is numerically greater than the focal length of lens group B by a factor not less than 1.42 and not more than 1.73; (h) the fourth lens group D is formed of two parts (D 1 and D 2 ) separated from each other by a clear air space; (i) the first part D 1 of the fourth lens group is of negative power; (j) the second part D 2 of the fourth lens group is of positive power; (k) said first part D 1 comprises a compound member formed of at least two elements; and (l) the focal length of said first part D 1 is numerically greater than the focal length of the third lens group C by a factor not less than 1.16 and not more than 1.42; the respective elements of the lens being so dimensioned that one of the refractive powers Δn/r of the lens differs by more than 0.05 times 1/fA from the corresponding refractive power of a lens dimensioned in accordance with the data in the following table, fA being the focal length of the converging first lens group A, and the respective symbols in the table having the meanings explained in the accompanying specification: ______________________________________ Lens Thicknesses element Radii and Spacings n.sub.d V.sub.d ______________________________________ r.sub.1 + 421.790 I d.sub.1 3.0 1.75520 27.58 r.sub.2 + 64.470 d.sub.2 1.8 r.sub.3 + 69.282 II d.sub.3 10.5 1.69100 54.71 r.sub.4 - 453.140 d.sub.4 0.1 r.sub.5 + 64.470 III d.sub.5 7.0 1.69100 54.71 r.sub.6 + 339.850 0.5 d.sub.6 40.523 53.897 r.sub.7 + 113.824 IV d.sub.7 1.2 1.71300 53.83 r.sub.8 + 17.278 V d.sub.8 8.0 1.71300 53.83 r.sub.9 - 48.000 d.sub.9 1.0 r.sub.10 + 25.664 VI d.sub.10 3.2 1.75520 27.58 r.sub. 11 + 69.282 d.sub.11 2.0 r.sub.12 + 37.585 VII d.sub.12 3.0 1.75520 27.58 r.sub.13 + 79.431 55.797 d.sub.13 15.774 2.400 BL r.sub.14 ∞ iris diaphragm 15.245 d.sub.14 4.749 4.829 r.sub.15 + 1122.000 VIII d.sub.15 2.0 1.805518 25.43 r.sub.16 + 32.545 IX d.sub.16 8.0 1.61272 58.63 r.sub.17 - 57.460 d.sub.17 0.1 r.sub.18 + 99.283 X d.sub.18 4.2 1.71300 53.83 r.sub.19 - 172.776 d.sub.19 0.1 r.sub.20 + 127.721 XI d.sub.20 4.4 1.71300 53.83 r.sub.21 - 68.293 2.528 d.sub.21 13.024 12.944 r.sub.22 - 29.853 XII d.sub.22 1.0 1.71300 53.83 r.sub.23 + 20.834 XIII d.sub.23 4.5 1.76180 26.95 r.sub.24 + 227.110 d.sub.24 10.7 r.sub.25 - 1729.000 XIV d.sub.25 3.2 1.69100 54.71 r.sub.26 - 35.737 d.sub.26 4.1 r.sub.27 + 112.204 XV d.sub.27 2.2 1.80518 25.43 r.sub.28 + 32.315 d.sub.28 2.7 r.sub.29 + 82.939 XVI d.sub.29 3.3 1.46450 65.77 r.sub.30 - 35.228 d.sub.30 0.1 r.sub.31 + 97.166 XVII d.sub.31 4.1 1.60311 60.60 r.sub.32 - 22.386 XVIII d.sub.32 1.5 1.80518 25.43 r.sub.33 - 92.387 Back focus s' = 28.53 ______________________________________

Claim 4

A photographic lens of continuously variable focal length consisting of four lens groups comprising, in sequence from front to rear along an optical axis: (a) a first group (A) of converging refractive power; (b) a second group (B) of diverging refractive power; (c) a third group (C) of converging refractive power; and (d) a fourth group (D) of converging refractive power; (e) said lens group being so dimensioned and arranged that a change in the focal length is effected by displacing diverging lens group B and converging lens group C along the optical axis relative to each other and relative to groups A and D while maintaining a constant back focus; said lens being characterized by the features that: (f) an iris diaphragm (BL) is located between group B and group C; (g) the third lens group C has a focal length which is numerically greater than the focal length of lens group B by a factor not less than 1.42 and not more than 1.73; (h) the fourth lens group D is formed of two parts (D 1 and D 2 ) separated from each other by a clear air space; (i) the first part D 1 of the fourth lens group is of negative power; (j) the second part D 2 of the fourth lens group is of positive power; (k) said first part D 1 comprises a compound member formed of at least two elements; and (l) the focal length of said first part D 1 is numerically greater than the focal length of the third lens group C by a factor not less than 1.16 and not more than 1.42; the respective elements of the lens being so dimensioned that one of the refractive powers Δn/r of the lens differs by more than 0.05 times 1/fA from the corresponding refractive power of a lens dimensioned in accordance with the data in the following table, fA being the focal length of the converging first lens group A, and the respective symbols in the table having the meanings explained in the accompanying specification: ______________________________________ Lens Thicknesses element Radii and Spacings n.sub.d V.sub.d ______________________________________ r.sub.1 + 421.790 I d.sub.1 3.0 1.75520 27.58 r.sub.2 + 64.470 d.sub.2 1.8 r.sub.3 + 69.282 II d.sub.3 10.5 1.69100 54.71 r.sub.4 - 453.140 d.sub.4 0.1 r.sub.5 + 64.470 III d.sub.5 7.0 1.69100 54.71 r.sub.6 + 339.850 0.5 d.sub.6 40.523 53.897 r.sub.7 + 113.824 IV d.sub.7 1.2 1.71300 53.83 r.sub.8 + 17.278 V d.sub.8 8.0 1.71300 53.83 r.sub.9 - 48.000 d.sub.9 1.0 r.sub.10 + 25.664 VI d.sub.10 3.2 1.75520 27.58 r.sub. 11 + 69.282 d.sub.11 2.0 r.sub.12 + 37.585 VII d.sub.12 3.0 1.75520 27.58 r.sub.13 + 79.431 55.797 d.sub.13 15.774 2.400 BL r.sub.14 ∞ iris diaphragm 15.245 d.sub.14 4.749 4.829 r.sub.15 + 1122.000 VIII d.sub.15 2.0 1.805518 25.43 r.sub.16 + 32.545 IX d.sub.16 8.0 1.61272 58.63 r.sub.17 - 57.460 d.sub.17 0.1 r.sub.18 + 99.283 X d.sub.18 4.2 1.71300 53.83 r.sub.19 - 172.776 d.sub.19 0.1 r.sub.20 + 127.721 XI d.sub.20 4.4 1.71300 53.83 r.sub.21 - 68.293 2.528 d.sub.21 13.024 12.944 r.sub.22 - 29.853 XII d.sub.22 1.0 1.71300 53.83 r.sub.23 + 20.834 XIII d.sub.23 4.5 1.76180 26.95 r.sub.24 + 227.110 d.sub.24 10.7 r.sub.25 - 1729.000 XIV d.sub.25 3.2 1.69100 54.71 r.sub.26 - 35.737 d.sub.26 4.1 r.sub.27 + 112.204 XV d.sub.27 2.2 1.80518 25.43 r.sub.28 + 32.315 d.sub.28 2.7 r.sub.29 + 82.939 XVI d.sub.29 3.3 1.46450 65.77 r.sub.30 - 35.228 d.sub.30 0.1 r.sub.31 + 97.166 XVII d.sub.31 4.1 1.60311 60.60 r.sub.32 - 22.386 XVIII d.sub.32 1.5 1.80518 25.43 r.sub.33 - 92.387 Back focus s' = 28.53 ______________________________________