Compact zoom lens

Claim 2

A compact zoom lens having, in order from the object side, a first positive lens group for focusing, a second negative lens group for variation of focal length, a third positive lens group for compensation of image position, and a fourth positive lens group for imaging, said compact zoom lens being a mechanical compensation type zoom lens arranged so that said second lens group is moved in the direction of the optical axis for the purpose of varying the focal length and so that the variation of final image position to be caused by the above movement is compensated for by moving said third lens group to form a locus of points concave toward the object side, said first lens group having a two-component, three-element lens configuration with one lens component composed of a positive cemented doublet consisting of a negative lens and a positive lens and the other lens component consisting of a positive lens; said second lens group having a three-component, four-element lens configuration with first, second and third lens components in order from the object side, said first lens component being a positive meniscus lens concave toward the object side, said second lens component being a negative biconcave lens having a concave surface with a small radius of curvature arranged toward the image side, and said third lens component being a negative cemented doublet consisting of a negative biconcave lens and a positive meniscus lens concave toward the image side; said third lens group comprising at least one positive lens; and said compact zoom lens fulfilling the following conditions: -∞<r.sub.B1 <-7|f.sub.B | -5|f.sub.B |<r.sub.B2 <-3|f.sub.B | -6|f.sub.B |<r.sub.B3 <-3|f.sub.B | d.sub.B2 <0.12|f.sub.B | wherein, r Bi is the radius of curvature of the ith lens surface in said second lens group in order from the object side, d Bi is the ith distance between lens surfaces in said second lens group in order from the object side, and f B is the focal length of said second lens group as a whole.

Claim 3

A compact zoom lens according to claim 1 wherein said fourth lens group has a six component, six-element lens configuration comprising first, second, third, fourth, fifth and sixth lens components in order from the object side, said first and second lens components of said fourth lens group being positive meniscus lenses concave toward the image side, said third lens component of said fourth lens group being a negative lens having a concave surface with a small radius of curvature arranged toward the image side, said fourth lens component of said fourth lens group being a positive biconvex lens having a large airspace with respect to said third lens component, said fifth lens component of said fourth lens group being a biconcave lens having a concave surface with a small radius of curvature arranged toward the object side, and said sixth lens component of said fourth lens group being a biconvex lens; and with said fourth lens group fulfilling the following conditions: 0.2f.sub.D <r.sub.D1 <0.32f.sub.D 0.25f.sub.D <r.sub.D3 <0.35f.sub.D 1.45<n.sub.D1 <1.6 1.45<n.sub.D2 <1.6 1.65<n.sub.D3 0.12f.sub.D <d.sub.D6 <0.22f.sub.D wherein, r Di is the radius of curvature of the ith lens surface in said fourth lens group in order from the object side, d Di is the ith distance between lens surfaces in said fourth lens group in order from the object side, n Di is the refractive index of the ith lens in said fourth lens group in order from the object side, and f D is the focal length of said fourth lens group.

Claim 4

A compact zoom lens according to claim 2 and further fulfilling the following conditions: 0.31f.sub.D <f.sub.D1.2 <0.4f.sub.D 0.9f.sub.D <f.sub.D1.3 <1.1f.sub.D wherein, f D1 .2 is the total focal length of said first and second lens components in said fourth lens group, and f D1 .3 is the total focal length of said first, second and third lens components in said fourth lens group.

Claim 5

A compact zoom lens according to claim 2 in which said third lens group comprises a positive cemented doublet consisting of a positive lens and a negative lens, and wherein said compact zoom lens is characterized by the following numerical data: ______________________________________ r d n νd ______________________________________ 1 72.103 1.80 1.80518 25.4 2 42.437 6.00 1.62299 58.2 3 a 155.302 0.10 4 78.339 4.50 1,62299 58.2 5 -786.439 b 6 -472.427 2.50 1.80518 25.4 7 -102.327 1.20 8 -119.002 1.00 1.69680 55.5 9 c 53.678 2.60 10 -46.650 1.00 1.69680 55.5 11 33.097 2.80 1.80518 25.4 12 98.419 d 13 90.909 3.90 1.62299 58.2 14 e -38.949 1.00 1.80518 25.4 15 -71.375 f 16 27.273 4.00 1.51112 60.5 17 117.351 0.20 18 28.692 4.00 1.51112 60.5 19 131.858 3.50 20 495.949 2.00 1.71735 29.5 21 28.214 15.70 22 g 55.013 4.00 1.56732 42.8 23 -52.646 2.50 24 -20.826 1.50 1.77250 49.6 25 154.757 3.00 26 73.842 4.00 1.59551 39.2 27 -62.938 ______________________________________

Claim 6

A compact zoom lens according to claim 2 in which said third lens group comprises a positive cemented doublet consisting of a positive lens and a negative lens, and wherein said compact zoom lens is characterized by the following numerical data: ______________________________________ r d n νd ______________________________________ 1 64.228 1.80 1.80518 25.4 2 39.623 6.00 1.62299 58.2 3 a 203.048 0.10 4 101.015 3.50 1.62299 58.2 5 -1280.761 b 6 -348.604 2.50 1.80518 25.4 7 -111.046 2.00 8 -160.931 1.00 1.69680 55.5 9 c 53.766 2.50 10 -44.851 1.00 1.69680 55.5 11 32.489 2.50 1.80518 25.4 12 99.412 d 13 93.728 3.50 1.62299 58.2 14 e -39.182 1.00 1.80518 25.4 15 -70.341 f 16 22.869 3.80 1.51112 60.5 17 107.930 0.20 18 30.775 3.80 1.51112 60.5 19 155.311 3.40 20 -282.485 1.90 1.71736 29.5 21 29.142 15.00 22 g 51.265 3.80 1.54072 47.2 23 -51.175 2.40 24 -17.964 1.50 1.77250 49.6 25 279.981 1.00 26 69.907 4.00 1.59270 35.3 27 -47.295 ______________________________________

Claim 7

A compact zoom lens according to claim 2 in which said third lens group comprises a positive cemented doublet consisting of a positive lens and a negative lens, and wherein said compact zoom lens is characterized by the following numerical data: ______________________________________ r d n νd ______________________________________ 1 65.376 1.80 1.80518 25.4 2 40.250 6.20 1.62299 58.2 3 a 217.791 0.10 4 101.646 3.52 1.62299 58.2 5 -1360.521 b 6 -290.812 2.50 1.80518 25.4 7 -108.018 2.01 8 -164.525 1.00 1.69680 55.5 9 c 54.256 2.45 10 -44.956 1.00 1.69680 55.5 11 32.841 2.55 1.80518 25.4 12 100.338 d 13 90.734 3.65 1.62299 58.2 14 e -40.123 1.00 1.80518 25.4 15 -72.381 f 16 24.136 3.87 1.51112 60.5 17 107.365 0.15 18 28.823 3.00 1.51112 60.5 19 115.031 4.00 20 ∞ 1.90 1.71736 29.5 21 28.170 15.00 22 g 52.379 3.80 1.56732 42.8 23 -52.379 2.40 24 -19.037 1.50 1.77250 49.6 25 230.640 2.40 26 73.097 4.50 1.59551 39.2 27 -55.397 ______________________________________