US 4,523,814 AGrant
Zoom Lens
Issue Date:1985-06-18
•11 Claims
•15 Drawing Sheets
Abstract
A zoom lens comprising, in order from the object, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power and a fourth lens group having a positive refractive power. The first through fourth lens groups are independently moved in an axial direction to vary the overall focal length. The zoom lens meets the following conditions: where F.sub.W is the overall focal length at the minimum end, (1) 0.25F.sub.W <F.sub.I <0.45F.sub.W (2) 1.65<n.sub.IV (3) 1.2f.sub.BW <f.sub.BT <0.95f.sub.BM F.sub.I is the focal length of the first lens group, n.sub.IV is the average refractive index, at d-line, of the lens elements constituting the fourth lens group, f.sub.BW and f.sub.BT are the backfocuses at the minimum and maximum ends of the overall focal length, respectively, and F.sub.BM is the backfocus at the intermediate end of the overall focal length.
Metadata
Assignee
- Asahi Kogaku Kogyo Kabushiki Kaisha
Inventor
- Sadao Okudaira
Application Information
Application Number:US 5062667
Filing Date:1983-06-21
Priority Date:1982-06-23
Art Unit:257
Classifications
IPC:
G02B 964G02B 1518
Field of Search:
350427
Patent Drawings (15 sheets)
Description
Background of the Invention
The present invention relates to a zoom lens with a highly variable power covering a wide-angle to telephoto range for use on 35 mm single-lens reflux cameras.
With the progress and development of zoom lens designing technology, zoom lenses have found widespread use as interchangeable lenses on 35 mm single-lens reflux cameras.
Wide-angle zoom lenses, standard zoom lenses, and telephoto zoom lenses are widely used today. To meet user's demands, in recent years there have been increasing numbers of zoom lenses including wide-angle to semi-telephoto capabilities and semi-wide-angle to telephoto capabilities. However, only a few zoom lenses are known which include a wide-angle capability with a covering angle of about 77.degree. to a telephoto capability with a covering angle of about 18.degree. and which are of high performance and compact for portability. Highly variable power zoom lenses which are compact and relatively high in performance, including wide-angle to telephoto capabilities, are also known for use on single-lens reflux cameras. Such zoom lenses achieve focusing by moving the overall lens system to prevent the diameter of a front lens from becoming increased due to ordinary focusing by a front lens group, thus acting as a varifocal lens. Alternatively, a varying focusing point due to zooming caused by focusing by other optical systems than the front lens group is corrected by a complicated mechanism, resulting in difficulty in the lens manufacture.
For example, U.S. Pat. No. 4,299,454 issued on Nov. 10, 1981 discloses a wide angle to long focus zoom lens, but has the following disadvantages.
The comparisons between the zoom lens according to the present invention and the zoom lens according to the disclosure of U.S. Pat. No. 4,299,454 will be made in terms of 35 mm SLR cameras.
(a) In the zoom lens according to U.S. Pat. No. 4,299,454 various aberrations would not be well compensated for. In particular, a spherical aberration is represented by approximately 1 to 3 mm at the telephoto end. According to the present invention, spherical aberration is represented by approximately 0.2 to 0.3 mm at the telephoto end. This distinction means that the lens system according to U.S. Pat. No. 4,299,454 would be put into practical use with great difficulty.
(b) The zoom lens according to U.S. Pat. No. 4,299,454 would be large in physical size beyond such a limit that it is acceptable as an interchangeable lens for SLR cameras in the market. More specifically, a diameter of the front lens of the zoom lens according to U.S. Pat. No. 4,299,454 ranges approximately from 75 to 80 mm. On the other hand, according to the present invention, a diameter of the front lens of the zoom lens is approximately 65 mm, which would easily be acceptable as an interchangeable lens for practical use.
(c) In the zoom lens according to U.S. Pat. No. 4,299,454, in spite that the front lens diameter is large as set forth in the item (b) above, an amount of marginal light is very small or represented by zero in some examples described in U.S. Pat. No. 4,299,454. Even if a thickness of an edge portion of each lens element would be made possibly thin while keeping the 35 mm camera image field size at 24.times.36 mm, the amount of marginal light would be still insufficient according to the disclosure of U.S. Pat. No. 4,299,454. This means that it would be difficult to put the zoom lens according to U.S. Pat. No. 4,299,454 into practical use.
(d) For the following reasons, in the zoom lens according to U.S. Pat. No. 4,299,454, it would be impossible to carry out a so-called front-lens-moving focusing and therefore, the lens system thereof must be of the overall-lens-moving focusing type, which has a serious disadvantage for the zoom lens. On the other hand, according to the present invention, the so-called front-lens-moving focusing may readily be achieved to enable practical short-distance focusing.
As described above, the zoom lens system disclosed in U.S. Pat. No. 4,299,454 may achieve the zooming but is difficult to realize.
Summary of the Invention
The present invention relates to a zoom lens which meets the requirements for high performance and compactness and at the same time is as capable of focusing through movement of a front lens group as well known zoom lenses.
Brief Description of the Drawings
FIG. 1 is a view showing a lens arrangement according to Example 1 of the invention;
FIGS. 2 through 5 are diagrams showing aberrations of Example 1, FIG. 2 being illustrative of those at a shortest focal length, FIG. 3 at a first intermediate focal length, FIG. 4 at a second intermediate focal length, and FIG. 5 at a longest focal length;
FIG. 6 is a view showing a lens arrangement according to Example 2 of the invention;
FIGS. 7 through 10 are diagrams showing aberrations of Example 2, FIG. 7 being illustrative of those at a shortest focal length, FIG. 8 at a first intermediate focal length, FIG. 9 at a second intermediate focal length, and FIG. 10 at a longest focal length;
FIG. 11 is a view showing a lens arrangement according to Example 3 of the invention;
FIGS. 12 through 15 are diagrams showing aberrations of Example 3, FIG. 12 being illustrative of those at a shortest focal length, FIG. 13 at a first intermediate focal length, FIG. 14 at a second intermediate focal length, and FIG. 15 at a longest focal length;
FIG. 16 is a view showing a lens arrangement according to Example 4 of the invention;
FIGS. 17 through 20 are diagrams showing aberrations of Example 4, FIG. 17 being illustrative of those at a shortest focal length, FIG. 18 at a first intermediate focal length, FIG. 19 at a second intermediate focal length and FIG. 20 at a longest focal length;
FIG. 21 is a view showing a lens arrangement according to Example 5 of the invention; and
FIGS. 22 through 25 are diagrams showing aberrations of Example 5, FIG. 22 being illustrative of those at a shortest focal length, FIGS. 23 and 24 at first and second intermediate focal lengths, and FIG. 25 at a longest focal length.
Detailed Description of the Preferred Embodiments
The present invention will hereinafter be described in detail.
According to the present invention, a zoom lens comprises, in order from the object, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power and a fourth lens group having a positive refractive power. The first through fourth lens groups are independently moved in an axial direction to vary the overall focal length. The zoom lens meets the following conditions:
(1) 0.25F.sub.W <F.sub.I <0.45F.sub.W
(2) 1.65<n.sub.IV
(3) 1.2f.sub.BW <f.sub.BT <0.95f.sub.BM
where F.sub.W is the overall focal length at the minimum end,
F.sub.I is the focal length of the first lens group,
n.sub.IV is the average refractive index, at d-line, of the lens elements constituting the fourth lens group,
f.sub.BW and f.sub.BT are the backfocuses at the minimum and maximum ends of the overall focal length, respectively, and
f.sub.BM is the backfocus at 0.78 times the maximum overall focal length.
In the zoom lens according to the invention, the first lens group is composed of a first lens component of a negative meniscus lens, a second lens component of a positive lens and a third lens component of a positive lens, the second lens group is composed of a fourth lens component of a negative lens, a fifth lens component of a negative lens, a sixth lens component of a positive lens and a seventh lens component of a negative lens, the third lens group is composed of an eighth lens component of a negative lens and a ninth lens component of a positive lens, and the fourth lens group is composed of two or more positive lenses of the fourth lens group being located at the frontmost position of the fourth lens group and one of the negative lenses of the fourth lens group being located at the rearmost position of the fourth lens group. The zoom lens further meets the following conditions:
(4) (n.sub.2 +n.sub.3)/2>1.75
(5) .nu..sub.7 -.nu..sub.6 >10
(6) n.sub.L >1.8
where n.sub.2 and n.sub.3 are the refractive indexes of the second and third lens components at d-line, respectively,
.nu..sub.6 and .nu..sub.7 are the Abbe numbers of the sixth and seventh lens components at d-line, respectively, and
n.sub.L is the refractive index, at d-line, of the netative lens located at the rear most position of the fourth lens group.
In embodiments of the invention, the zoom lens meets the following condition:
(7) 1.8<n.sub.IVn
where n.sub.IVn is the average refractive index, at d-line, of the three negative lenses of the fourth lens group.
The condition (1) is related to focusing effected by movement of the front lens group (first lens group) according to the present invention. If the focal length F.sub.I were greater than the upper limit, then the distance which the focusing lens should move would be increased, and the diameter of the front lens would be increased to maintain a sufficient shortest focal length thereof. If the focal length F.sub.I were smaller than the lower limit, then the optical lens would become more compact, but the spherical aberration caused in a telephoto mode would be increased. With existing glass materials, the first lens group would produce increased chromatic aberration in a telephoto mode and could not be corrected easily. More preferably, the condition (1) is further limited to the condition (1'), 0.28F.sub.W <F.sub.I <0.4F.sub.W.
The condition (2) is concerned with the average value of the refractive indexes of the lens elements of the first lens group. To keep a highly variable power including a wide-angle capability according to the present invention, the width of a ray of light is increased which passes through the fourth lens group and converges in the vicinity of the center of an image field in medium-telephoto and telephoto modes. It would therefore be extremely difficult to reduce the spherical aberration produced in the fourth lens group. Many highly variable power zoom lenses heretofore available have reduced the F-number of the lens in medium-telephoto to telephoto modes. According to the present invention, the zoom lens retains a sufficient degree of F-number in medium-telephoto and telephoto lenses. To this end, it is important that the spherical aberration produced by the fourth lens group be made as small as possible. If the average refractive index n.sub.IV in the condition (2) were smaller than the lower limit, then the radii of curvature of the lens elements of the fourth lens group would be reduced on the average, and the spherical aberration of the fourth lens group would be become greater, with the result that it would be difficult to design a zoom lens having the same degree of F-number in a telephoto mode as that the present invention seeks.
Where a highly variable power zoom lens including a wide-angle capability as according to the present invention is constructed of an optical system with four lens groups movable independently of each other, the lens groups are allowed to move freely in varying their powers. The conditions (3) serves to prescribe the movement of the fourth lens group to improve aberration correction. Unless the fourth lens group were moved to render the backfocus f.sub.BT larger than the lower limit in wide-angle to telephoto modes, it would be necessary to increase the power of the second lens group and to increase the number of lenses thereof to maintain the highly variable power that meets the requirements of the invention. If the number of the lens elements of the second lens group were increased, then the diameter of the front lens could not be reduced, resulting in an increase in the cost. Unless the fourth lens group were moved to render the backfocus f.sub.BT smaller than the upper limit in medium-telephoto to telephoto modes, the width of a ray of light into the fourth lens group covering in the vicinity of the center of an image field would become too large to maintain the degree of F-number as achieved by the examples of the invention. It would thus be difficult to correct the spherical aberration.
According to the present invention, the zoom lens system satisfying the above described basic conditions (1), (2) and (3) preferably meets the following conditions.
(4) (n.sub.2 +n.sub.3)/2>1.75
(5) .nu..sub.7 -.nu..sub.6 >10
(6) n.sub.L >1.8
The condition (4) relates to the average refractive index of the two positive lenses which constitute a part of the first lens group which is used as a focusing lens group. If the value, (n.sub.2 +n.sub.3)/2, would be smaller than 1.75, the radii of curvature of the second and third lenses would be rather short under the condition that the focal length of the first lens group be kept at the value defined by the condition (1) in view of the displacement of the first lens group for focusing in order to miniaturize the overall lens system. As a result, faults in performance would tend to be caused. More preferably, the condition (4) is further limited to the condition (4'), (n.sub.2 +n.sub.3)/2>1.77.
The condition (5) defines a difference in Abbe number between the positive sixth lens and the negative seventh lens which are cemented to each other in the second lens group. If the value, .nu..sub.7 -.nu..sub.6, would be smaller than 10, it would be difficult to suppress variation in chromatic aberration in the overall lens system of high-zoom-ratio to which the present invention is related.
The condition (6) defines the refractive index of the negative lens located on the final position of the fourth lens group. If the value, n.sub.L, would be smaller than 1.8, the radius of curvature thereof would become excessively small so that astigmatism would be remarkable over the entire zoom range and spherical aberration would be remarkable on the telephoto side. More preferably, the condition (6) is further limited to the condition (6'), n.sub.L >1.85.
The fourth lens group of the invention is preferably composed of, in order from the object, one or more positive lenses, a single negative lens having a surface of a smaller radius of curvature facing the object, a positive lens component including one or more positive lenses, a single negative lens having a surface of a smaller radius of curvature facing an image, two or more positive lenses, and a single negative lens having a surface of a smaller radius of curvature facing the object.
According to the present invention, it is preferable that the zoom lens system meet the following condition (7) as well as the basic condition (1) to (3).
(7) 1.8<n.sub.IVn
where n.sub.IVn is the average refractive index, at d-line, of the three negative lenses of the fourth lens group.
The condition (7) is directed to the average refractive index at d-line of the three negative lenses of the fourth lens group. If the average refractive index n.sub.IVn were smaller than the lower limit, then the radii of curvature of these negative lenses would become small, with the consequence that the astigmatism in the full zooming range and the spherical aberration in the telephoto mode would be rendered poor. Therefore, a sufficient degree of F-number in the telephoto mode is achieved by the examples of the invention could not be maintained unless the condition (7) were met. More preferably, the condition (7) is further limited to the condition (7'), 1.82<n.sub.IVn.
Data of examples of the zoom lens according to the present invention will be described. Designated in the tables at F is the focal length, r the radius of curvature of a lens, d a lens thickness or an inter-lens distance, n a refractive index at d-line, and .nu. the Abbe number of a lens with respect to d-line.
Example 1
Example 2
Example 3
Example 4
Example 5
Claims
What is claimed is:
1. A zoom lens comprising, in order from the object, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power and a fourth lens group having a positive refractive power, said first through fourth lens group being independently moved in an axial direction to vary the overall focal length, said zoom lens meeting the following conditions: (1) 0.25F.sub.W <F.sub.I <0.45F.sub.W, (2) 1.65<n.sub.IV, and (3) 1.2f.sub.BW <f.sub.BT <0.95f.sub.BM where F.sub.W is the overall focal length at the minimum end, F.sub.I is the focal length of the first lens group, n.sub.IV is the average refractive index, at d-line, of the lens elements constituting the fourth lens group, f.sub.BW and f.sub.BT are the backfocuses at the minimum and maximum ends of the overall focal length, respectively, f.sub.BM is the backfocus at an intermediate value of said overall focal length between said minimum and maximum ends.
2. The zoom lens according to claim 1, wherein said first lens group is composed of a first lens component of a negative meniscus lens, a second lens component of a positive lens and a third component of a positive lens, said second lens group is composed of a fourth lens component of a negative lens, a fifth lens component of a negative lens, a sixth lens component of a positive lens and a seventh lens component of a negative lens, said third lens group is composed of an eighth lens component of a negative lens and a ninth lens component of a positive lens, and said fourth lens group is composed of at least two positive lenses and at least two negative lenses, one of the positive lenses of the fourth lens group being located at the frontmost position of the fourth lens group and one of the negative lenses of the fourth lens group being located at the rearmost position of the fourth lens group, the zoom lens further meeting the following conditions: (4) (n.sub.2 +n.sub.3)/2>1.75, (5) .nu..sub.7 -.nu..sub.6 >10, and (6) n.sub.L >1.8 where n.sub.2 and n.sub.3 are the refractive indexes of said second and third lens components at d-line, respectively, .nu..sub.6 and .nu..sub.7 are the Abbe numbers of said sixth and seventh lens components at d-line, respectively, and n.sub.L is the refractive index, at d-line, of the negative lens located at the rearmost position of the fourth lens group.
3. The zoom lens according to claim 1, wherein said fourth lens group is composed of, in order from the object, at least one positive lens, a single negative lens having a surface of a smaller radius of curvature facing the object, a positive len component including at least one positive lens, a single negative lens having a surface of a smaller radius of curvature facing an image, at least two positive lenses, and a single negative lens having a surface of a smaller radius of curvature facing the object, said zoom lens meeting the following condition: (7) 1.8<n.sub.IVn where n.sub.IVn is the average refractive index, at d-line, of the three negative lenses of the fourth lens group.
4. The zoom lens according to claim 2, meeting the following conditions: (1') 0.28F.sub.W <F.sub.I <0.4F.sub.W, (4') (n.sub.2 +n.sub.3)/2>1.77, and (6') n.sub.L >1.85.
5. The zoom lens according to claim 3, meeting the following conditions: (1') 0.28F.sub.W <F.sub.I <0.4F.sub.W, and (7') 1.82<n.sub.IVn.
6. The zoom lens according to claim 5 further meeting the following chart: F = 28.805 - 132.342 No. r d n .nu. ______________________________________ 1 505.700 2.00 1.80518 25.4 2 69.120 1.88 3 71.400 9.84 1.72916 54.7 4 -444.818 0.15 5 66.300 5.69 1.88300 40.8 6 175.741 variable 7 184.399 1.20 1.88300 40.8 8 18.240 5.70 9 -119.280 1.30 1.81600 46.6 10 57.091 0.10 11 28.002 7.41 1.75520 27.5 12 -28.002 1.20 1.81600 46.6 13 75.000 variable 14 26.470 2.00 1.75520 27.5 15 22.339 2.00 16 33.299 3.30 1.77250 49.7 17 154.400 variable 18 31.120 4.50 1.61800 63.4 19 -206.849 2.22 20 -32.889 1.20 1.80518 25.4 21 -181.168 0.20 22 32.889 9.39 1.62041 60.3 23 -52.500 0.30 24 260.000 1.30 1.83481 42.7 25 24.157 2.30 26 35.862 4.84 1.48749 70.1 27 -61.411 0.20 28 104.599 5.06 1.66680 33.0 29 -36.800 3.21 30 -19.380 1.30 1.88300 40.8 31 -88.200 ______________________________________ variable F distance 28.806 50.037 103.062 132.342 ______________________________________ d6 1.200 15.420 34.470 44.580 d13 18.580 11.540 5.360 3.200 d17 17.820 10.030 2.540 0.800 ______________________________________ F.sub.I = 0.31F.sub.W n.sub.IV = 1.702 f.sub.BT = 0.91f.sub.BM = 1.54f.sub.BW (n.sub.2 + n.sub.3)/2 = 1.806 .nu..sub.7 -v.sub.6 = 19.1 n.sub.L = 1.883 n.sub.IVn = 1.841 ______________________________________
7. The zoom lens according to claim 5, further meeting the following chart: F = 28.801 - 132.316 No. r d n .nu. ______________________________________ 1 270.359 2.00 1.80518 25.4 2 66.762 1.40 3 68.597 9.39 1.72916 54.7 4 -1277.450 0.15 5 66.300 6.00 1.81600 46.6 6 218.700 variable 7 242.198 1.20 1.88300 40.8 8 18.768 5.70 9 -117.780 1.30 1.83481 42.7 10 50.845 0.10 11 28.598 7.41 1.80518 25.4 12 -28.598 1.20 1.88300 40.8 13 79.199 variable 14 27.300 2.00 1 80518 25.4 15 23.370 2.00 16 35.000 3.30 1.77250 49.7 17 349.704 variable 18 29.989 4.50 1.61800 63.4 19 6450.000 2.69 20 -31.514 1.20 1.80518 25.4 21 -226.050 0.20 22 34.871 8.80 1.56873 63.2 23 -54.300 0.30 24 118.902 1.30 1.83481 42.7 25 25.970 2.30 26 39.900 4.88 1.48749 70.1 27 -59.800 0.20 28 136.110 5.06 1.67270 32.1 29 -37.200 4.42 30 -19.600 1.30 1.88300 40.8 31 -65.243 ______________________________________ variable F distance 28.801 49.996 103.041 132.316 ______________________________________ d6 1.200 14.850 31.880 42.180 d13 19.210 11.910 5.270 3.200 d17 17.820 9.580 2.420 0.800 ______________________________________ F.sub.I = 0.32F.sub.W n.sub.IV = 1.696 f.sub.BT = 0.89f.sub.BM = 1.58f.sub.BW (n.sub.2 + n.sub.3)/2 = 1.773 .nu..sub.7 - .nu..sub.6 = 15.4 n.sub.L = 1.883 n.sub.IVn = 1.841 ______________________________________
8. The zoom lens according to claim 4 further meeting the following chart: F = 28.799 - 132.000 No. r d n .nu. ______________________________________ 1 442.230 2.00 1.84666 23.9 2 64.265 0.66 3 67.343 8.80 1.88300 40.8 4 2219.557 0.15 5 62.922 6.30 1.81600 46.6 6 215.088 variable 7 79.830 1.60 1.88300 40.8 8 17.527 5.96 9 -132.071 2.00 1.83481 42.7 10 35.927 0.10 11 25.661 7.41 1.71736 29.5 12 -17.565 1.50 1.83481 42.7 13 134.848 variable 14 29.523 1.50 1.84666 23.9 15 27.524 2.00 16 47.276 2.23 1.83481 42.7 17 464.510 variable 18 25.241 7.44 1.72916 54.7 19 -59.424 1.60 20 -31.754 8.43 1.84666 23.9 21 -14.981 1.30 1.76180 27.1 22 39.641 2.20 23 -181.678 3.23 1.83481 42.7 24 -39.108 0.20 25 47.277 10.06 1.48749 70.1 26 -23.660 1.00 27 -18.441 1.60 1.88300 40.8 28 -54.267 ______________________________________ variable F distance 28.799 50.000 103.000 132.000 ______________________________________ d6 0.804 15.060 28.638 43.895 d13 15.195 8.750 2.795 1.999 d17 16.603 10.798 3.736 0.800 ______________________________________ F.sub.I = 0.31F.sub.W n.sub.IV = 1.757 f.sub.BT = 0.75f.sub.BM = 1.43f.sub.BW (n.sub.2 + n.sub.3)/2 = 1.806 .nu..sub.7 - .nu..sub.6 = 14.6 n.sub.L = 1.883 ______________________________________
9. The zoom lens according to claim 4 further meeting the following chart: F = 28.792 - 131.983 No. r d n .nu. ______________________________________ 1 257.656 2.00 1.84666 23.9 2 63.576 9.10 1.72916 54.7 3 -555.009 0.15 4 57.585 5.80 1.88300 40.8 5 158.336 variable 6 194.661 1.20 1.88300 40.8 7 17.157 5.96 8 -111.536 1.30 1.88300 40.8 9 59.238 0.10 10 26.088 7.41 1.78470 26.2 11 -20.752 1.20 1.88300 40.8 12 66.129 variable 13 27.122 1.50 1.84666 23.9 14 24.218 2.00 15 38.908 2.80 1.61800 63.4 16 -278.161 variable 17 29.183 6.95 1.80400 46.6 18 -72.819 1.60 19 -38.303 13.22 1.80518 25.4 20 38.079 2.20 21 137.720 3.23 1.48749 70.1 22 -35.268 0.20 23 80.076 5.80 1.60342 38.0 24 -23.995 2.46 25 -19.152 1.30 1.88300 40.8 26 -60.514 ______________________________________ variable F distance 28.792 49.991 102.978 131.983 ______________________________________ d5 1.197 14.609 28.195 36.892 d12 17.381 11.386 5.101 3.197 d16 17.059 10.276 3.007 0.794 ______________________________________ F.sub.I = 0.37F.sub.W n.sub.IV = 1.717 f.sub.BT = 0.85f.sub.BM = 1.40f.sub.BW (n.sub.2 + n.sub.3)/2 = 1.806 .nu..sub.7 - .nu..sub.6 = 14.6 n.sub.L = 1.883 ______________________________________
10. The zoom lens according to claim 5 further meeting the following chart: F = 28.820 - 132.448 No. r d n .nu. ______________________________________ 1 377.370 2.00 1.80518 25.4 2 69.147 1.20 3 70.160 9.77 1.72916 54.7 4 -533.185 0.15 5 69.120 5.39 1.88300 40.8 6 178.352 variable 7 183.798 1.20 1.88300 40.8 8 18.372 5.70 9 -116.421 1.30 1.83481 42.7 10 57.600 0.10 11 27.915 1.00 1.80440 39.6 12 21.000 6.61 1.75520 27.5 13 -29.210 1.00 1.81554 44.4 14 76.700 variable 15 26.946 2.00 1.75520 27.5 16 22.606 2.00 17 33.306 3.30 1.75520 49.6 18 173.952 variable 19 31.800 4.50 1.61800 63.4 20 -289.338 2.36 21 -32.000 1.20 1.80518 25.4 22 -195.000 0.20 23 34.040 7.12 1.67000 57.4 24 -30.134 2.00 1.56873 63.1 25 -96.900 0.30 26 165.100 1.30 1.88300 40.8 27 25.064 2.30 28 37.980 5.08 1.48749 70.1 29 -51.300 0.20 30 193.485 5.06 1.66680 33.0 31 -36.395 4.32 32 -19.080 1.30 1.88300 40.8 33 -56.405 ______________________________________ variable F distance 28.820 50.020 103.075 132.448 ______________________________________ d6 1.187 13.367 35.417 44.753 d14 18.624 11.032 5.300 3.207 d18 17.831 9.590 2.630 0.781 ______________________________________ F.sub.I = 0.30F.sub.W n.sub.IV = 1.698 f.sub.BT = 0.94f.sub.BM = 1.59f.sub.BW n.sub.IVn = 1.857 ______________________________________
11. The zoom lens according to claim 1, wherein f.sub.BM is the backfocus at 0.78 times the maximum overall focal lenth.