GB2033604A - Zoom lenses having front focusing group - Google Patents

Abstract

A zoom lens having capability of focusing to a magnification of 1:2 through movement of only the front focusing group G1. A plurality of following groups G2 and G3 are movable to vary the equivalent focal length. The front focusing group G1 comprises a positive doublet L1, L2 followed by a positive singlet L3, the ratio of the optical power of the singlet to the optical power of the doublet being greater than zero but less than 2.0. The ratio between the equivalent focal length of the first group and the maximum equivalent focal length of the lens is between .4 and .67. The power of the focusing group is chosen in relation to the power of the lens at its long focal length to accomplish close focusing with minimal axial travel while providing good aberration correction. <IMAGE>

Description

SPECIFICATION Improvements in zoom lenses This invention relates to zoom lens.

In most zoom lenses, the first group of lens elements may be moved along the optical axis to achieve focusing from infinity to moderately close distances, typically having a magnification of 1/10 or less. To enable these lenses to focus still closer, in a macro or close focusing mode, the lens is adjusted by suitable repositioning of the zooming groups, or by other lens group repositioning.

An example of such optics is disclosed in U.S. Patent No 3,817,600, where the zooming elements are moved in a different relationship to achieve close focusing below two meters up to a magnification of 1:2.2 as close as eighteen inches from the front element.

A lens of this type has proven to be an optic and has been marketed as a Vivitar Series I Lens of 70-210mm equivalent focal length (EFL). In the close focusing mode, it is possible to achieve magnifications in the range of 1:2.2 to 1:5. However, this lens does require repositioning of the zooming groups for different movement for close focusing.

Attempted competitive lenses of lesser quality generally exhibit poor off-axis image quality caused by large amounts of astigmatism in the close focusing mode. In some cases, spherical aberration causing poor contrast is also introduced.

Conventional zoom lenses are characterized by a weak power (long focal length) first group which had been believed to be the best way to minimize aberration change due to focusing. Zoom lens objectives generally do have an optically strong front group.

The present invention consists in a zoom lens having a first group movable axially for focusing, a plurality of following groups movable axially of the lens to vary the equivalent focal length of the lens, said front focusing group comprising a positive doublet followed by a positive singlet

and .67 > F1 > .4 FL where 8s is the optical power of the singlet, 0D is the optical power of the doublet, F1 is the equivalent focal length of the first group, and FL is the maximum equivalent focal length of the lens.

One lens embodying the present invention is a mechanically compensated zoom lens having the capability of focusing continuously from infinity down to the macro or close focusing mode at the longer equivalent focal length (EFL) by small movement of a front focusing group, i.e. without switching the zooming groups into a close focusing mode. For purposes of definition, "macro" refers to ctose-up photography with image magnification, typically in the range of 1:2 magnification.

In the present embodiment the close focusing capability to a magnification of 1:2 is achieved by the appropriate design of the front focusing group in relation to the overall lens. This design overcomes the usual design shortcomings by having stability of spherical aberration with conjugate change, strong power, and simple construction. These generally are considered to be conflicting parameters. It is well known that the front group is required to be quite stable with respect to variation of spherical aberration over the focusing range. However, it is also desirable that the front group have strong power to provide a compact system and to reduce as much as possible the required focusing motion. In addition, it is mechanically convenient that the front group be of simple construction, so that the weight of the lens is reduced.This is particularly important for maintaining balance of a lens with a large focusing range, normally resulting in a long lens travel to achieve close focusing. It is also desirable to achieve the above-mentioned effects in an optical system having a relatively fast aperture.

It has been determined that by appropriate selection of the power of the front focusing group in relationship to the powers of the overall lens that close focusing as close as 20" to 24" from the front lens element can be achieved with a magnification of about 1:2.

This is achieved in a zoom lens in which the front focusing group has a given relationship to the overall power of the lens and where the elements of the focusing group have a given relationship as hereinafter described.

The invention wll now be described, by way of example, with reference to the accompanying drawings, in which Figures 1-4 are diagrammatic side views of lens embodying the invention.

A lens emboding the invention includes a strongly positive first group G1,which is adjustable axially for focusing of the optical system. A second component is a variator or negative component group variable along the optical axis for varying the equivalent focal length of the objective lens. This group G2 is movable along with, and relative to a third component group G3 which acts as a compensator to maintain a fixed image plane as the focal length of the optical system is varied. Although this lens is capable of focusing to extremely close distances, the zoom components G2 and G3 are not required to be independently adjustable to assist in the focusing of the optical system when in a macro or close focusing range. Group G4 is a fixed objective lens for relaying the image to the image or focal plane of the system.

In the optical design typifying the embodiments, the first positive group G1 comprises two positive components, a doublet L1, L2, followed by a positive element L3.

The elements of group G 1 satisfy the conditions: 0 < S/D < 2.0 where D designates the power of the doublet group within the front group G1 and s designates the power of the singlet lens within the front group. Also, .67 > F1 > .4 FL where F1 is the focal length of the first group, and FL is the long extreme equivalent focal length of the lens.

The parameters set forth are necessary for suitably balancing the aberrations of the lens system when the lens is focused across the intended broad range. Together, the conditions prevent or significantly reduce aggravation of spherical aberrations and astigmatism which may occur as the angles of the incident light rays change due to focusing of the lens on distant, and extremely close objects. Satisfaction of these parameters ensures a compact lens with a relatively short focusing motion. As set forth hereinafter, the dimensions, relationships, and parameters of the lenses are such as to satisfy the conditions as set forth above.

More specifically, the first parameter < S/D < 2.0 is required in order to yield the distribution of power necessary for stability of spherical aberration with respect to conjugate change.

The second parameter .67 > F, > .4 FL is required because of the relationship between the power 1 of the focusing group and the necessary focusing travel FT for a given object distance FD, namely F1 (mm) FD = FT where FD is the focusing distance, F1 is the EFL of the front focusing group and FT is the focusing travel of the front group from infinity to the closest focusing distance. As the power of group G1 increases, the F1 correspondingly decreases, the focusing distance FD decreases.

Moreover, if the power of the front group becomes too strong, it is impossible to satisfactorily correct the spherical aberration and astigmatism over a range of conjugates.

Particularly, the first lens group G1, as shown in Figure 1, includes a positive doublet subtending a negative element L1 and a biconcave element L2 formed as a cemented doublet of strong positive power, followed by a positive meniscus element L3 convex to the object. These elements are in fixed relation, adapted to be shifted axially as a group for focusing images of subjects at distances as close as 20 inches from the front element L1, regardless of the equivalent focal length of the lens. This selection of the relatively strong power in group G 1 reduces the focusing travel as will be apparent from the foregoing equation.

The variator or second lens group G2 is negative and is air-spaced from the first component by a variable amount. This variator group G2 includes a negative element L4 which is separated from a negative biconcave doublet L5, L6.

The compensator or third lens group G3 is of biconvex and of positive power and includes a negative meniscus L7 and a biconvex element L8. Group G3 is movable axially relative to the variator group G2 and the forward component of a fixed relay group G3.

The relay group G4 is divided into two separate widely spaced subgroups or components. The forward component has positive power and is fixed relative to the rear component of that group. The forward component includes a positive element L9 spaced from a doublet formed of positive element L10 and a negative element L1 1 forming a cemented doublet. The rear component, a negative component L12, is closely spaced to a positive component L13.

The foregoing preferred embodiment includes 13 elements arranged in the four component groups.

In the following tables, various embodiments of the invention are set forth for various EFL ranges, with the parameters of the invention. In the following prescription tables, the reference L followed by an arabic numeral indicates lens elements, the lens elements progressively from the object end to the image end of the lens. The reference surface numbers R are the progressive lens surfaces. Nd is the index of refraction of the lens elements. Vd is the dispersion of the lens elements as measured by the Abbe number. The spaces Z are spaces between lens groups which vary with change in equivalent focal length (EFL). Positive surface radii are struck from the right at the optical axis. Negative radii are struck from the left at the optical axis.

A lens as shown in Figure 1 scaled to an image frame of 24 x 36mm and EFL's of 101 mum to 195mm is substantially described in Table I.

TABLE I Axial Distance Element Surface Radii (mm) Between Surfaces (mm) Nd Vd S1 = 69.077 L1 3.0 1.7847 26.06 S2 = 44.817 L2 10.0 1.5101 63.43 S3 = -213.552 0.3 S4 = 92.077 L3 3.5 1.5101 63.43 S5 = 142.825 Z1 S6 = 600.754 L4 2.0 1.6583 57.26 S7 = 69.943 3.5 S8 = -71.613 L5 2.0 1.6910 54.70 59 = 32.133 L6 4.76 1.8467 23.83 S10 = 76.984 Z2 S11=74.163 L7 2.0 1.7847 26.06 S12 = 39.674 L8 6.29 1.5638 60.83 S13 = -96.905 Z3 S14 = 78.588 L9 3.0 1.5101 63.43 S15 = 693.028 0.3 S16 = 26.460 L10 5.826 1.5101 63.43 S17 = 427.148 L11 2.0 1.8061 40.74 S18 = 45.219 4.81 Aperture Stop 40.26 S19 = -18.927 L12 2.0 1.7725 49.62 S20 = -53.001 0.3 S21=412.053 L13 3.42 1.6727 32.17 S22 = -53.841 EFL Z1 Z2 Z3 101mm 2.81mm 31.68mm 3.72mm 152 18.84 14.89 4.50 195 25.51 1.33 11.37 A lens as shown in Figure 2 scaled to an image frame of 24 x 36mm and EFL's of 76.0mm to 200.1 mm is substantially described in Table II.

TABLE II Axial Distance Element Surface Radii (mm) Between Surfaces (mm) Nd Vd 51 = 100.120 L1 3.0 1.785 26.1 S2 = 58.560 L2 7.34 1.510 63.4 S3 = plano 0.3 S4 = 97.870 L3 5.15 1.510 63.4 S5 = -539.860 Z1 S6 = 205.760 L4 1.5 1.720 50.3 S7 = 70.027 3.74 S8 = -84.552 L5 1.5 1.720 50.3 S9 = 27.698 L6 4.51 1.785 25.7 S10 = 126.250 Z2 S11 = 104.624 L7 6.08 1.487 70.4 S12 = -32.924 L8 1.2 1.785 26.1 S13 = -51.566 Z3 S14 = 32.652 L9 6.24 1.573 57.5 S15 = -85.340 L10 2.0 1.806 40.7 S16=175.960 4.81 Aperture Stop 42.660 S17 = -19.451 L11 2.0 1.804 46.5 S18 = =37.265 0.3 S19 = 101.789 L12 2.27 1.673 3.22 S20 = -300.147 EFL Z1 Z2 Z3 76.00mm 1.73mm 37.58mm 12.09mm 125.00 26.25 23.15 2.00 200.1 39.92 1.48 10.00 Another embodiment of an optical system according to this invention is given in Table Ill. In this embodiment, group G1 is substantially the same as described with respect to Figure 2, S3 is plano and S5 is negative. Group G2 includes a first positive element L4 which forms a doublet with negative element L5. In this group G2 component, a negative element L6 is spaced slightly from the doublet and is spaced variably by a larger distance from group G3.

In group G3, the doublet is reversed with respect to Figure 2 in that L11 is a meniscus and L12 is a biconvex element. Group G4 has the same elemental configuration as Figure 2.

A lens as shown in Figure 2 scaled to an image frame of 24 x 36mm and EFL's of 72mm to 150 mm is substantially described in Table III.

TABLE Ill Axial Distance Element Surface Radii (mm) Between Surfaces (mm) Nd Vd S1 = 62.296 L1 3.0 1.7847 26.06 S2 = 41.370 L2 12.806 1.4875 70.44 S3 = -266.277 0.3 S4= 86.478 L3 4.095 1.4875 70.44 S5 = 2731.894 Z1 S6 = -259.053 L4 2.0 1.6910 54.70 S7 = 65.984 2.805 S8 = -71.603 L5 2.0 1.7433 49.22 S9 = 24.730 L6 4.755 1.8467 23.83 S10 = 72.248 Z2 S11 = 49.336 L7 2.0 1.8467 23.83 S12 = 25.951 L8 6.287 1.6667 48.30 S13 = -133.121 Z3 S14 = 22.123 L9 5.381 1.4875 70.44 S15 = -684.989 .L10 2.0 1.8042 46.50 S16 = 66.251 29.67 S17 = -14.503 L11 2.0 1.5310 58.20 S18 = -31.216 0.3 S19 = 120.523 L12 2.350 1.8040 46.50 S20 = -189.269 EFL Z1 Z2 Z3 72.0mm 1.6 27.051 0.3 111.0 14.289 13.162 1.5 150.0 19.843 0.3 8.809 Another twelve element form of the invention is generally similar to Figure 2. This lens differs from Figure 2 in that S3 is very weakly negative instead of plano, and S12 is positive, thus reversing the doublet forming group G3.

As scaled to a 24 x 36mm image frame and EFL's of 72mm to 203mm, this lens is substantially described in Table IV.

TABLE IV Axial Distance Element Surface Radii (mm) Between Surfaces (mm) Nd Vd S1 = 87.504 L1 3.000 1.7847 26.06 S2 = 57.456 L2 12.806 1.4875 70.44 S3 = -576.167 0.300 S4 = 110.904 L3 3.500 1.4875 70.44 S5 = -1960.632 Z1 S6 = -829.307 L4 2.000 1.6910 54.70 S7 = 84.246 3.075 S8 = -91.582 L5 2.000 1.7433 49.22 S9 = 29.357 L6 4.755 1.8467 23.83 S10 = 80.962 Z2 S11=76.817 L7 2.000 1.8467 23.83 S12 = 36.571 L8 6.287 1.6667 48.30 S13=-118.534 Z3 S14 = 25.919 L9 7.000 1.4875 70.44 S15 = -154.920 L10 2.000 1.8042 46.50 S16 = 92.608 39.753 S17 = -17.481 L11 2.000 1.8042 46.50 S18 = -37.440 2.029 S19 = 251.831 L12 2.452 1.7495 35.04 S20 = -69.558 EFL Z1 Z2 Z3 72.0mm 1.5mm 49.045mm 0.3mm 150.0 30.760 18.585 1.5 203.0 36.664 0.3 13.881 Another embodiment of the invention as shown in Figure 3, scaled to an image frame of 24 x 36mm and EFL's of 101 mm to 194mm, is substantially described in Table V.

TABLE V Axial Distance Element Surface Radii (mm) Between Surfaces (mm) Nd Vd S1 = 70.981 L1 3.0 1.7847 26.06 S2 = 45.725 L2 10.0 1.5101 63.43 S3 = -190.826 0.3 S4= 77.534 L3 3.5 1.5101 63.43 S5=115.121 Z1 S6 = -366.358 L4 3.829 1.8467 23.83 S7 = -49.175 L5 2.0 1.6910 54.70 S8=61.777 3.961 S9 = -53.090 L6 2.0 1.6583 57.26 S10 = 255.263 Z2 S11 = 93.727 L7 6.429 1.5638 60.83 S12 = -35.861 L8 2.0 1.7847 26.06 S13 = -71.255 Z3 S14 = 74.385 L9 2.629 1.5101 63.43 S15 = 259.362 0.3 S16 = 26.413 L10 5.653 1.5101 63.43 S17 = 366.100 L11 2.0 1.8061 40.74 S18 = 43.497 27.063 S19 = 112.212 L12 2.615 1.6727 32.17 S20 = -77.326 6.977 S21 = -24.455 L13 2.0 1.7725 49.62 S22 = -97.188 EFL Z1 Z2 Z3 101.0mm 2.812mm 29.314mm 3.744mm 152.0 18.190 13.176 4.503 194.0 24.580 0.3 10.990 Another embodiment of the invention is substantially as shown in Figure 3 differing in elemental configuration only that in negative group G3 the elements L7 and L8 are reversed. Such lens as scaled to an image frame of 24 x 36mm and EFL of 71.5mm to 146.5mm is substantially described in Table VI.

TABLE VI Axial Distance Element Surface Radii (mm) Between Surfaces (mum) Nd Vd S1 = 55.041 L1 2.50 1.785 26.1 S2 = 36.225 L2 8.50 1.510 63.4 S3 = -246.043 0.2 S4 = 86.032 L3 3.0 1.510 63.4 S5 = 380.808 Z1 S6=-192.163 L4 1.5 1.658 57.3 S7 = 51.582 2.56 S8 = -63.000 L5 1.5 1.691 54.7 S9 = 21.990 L6 3.6 1.785 26.1 S10 = 67.930 Z2 S11 = 54.447 L7 1.5 1.785 26.1 S12 = 27.783 L8 5.5 1.540 59.7 S13 = -85.292 Z3 S14 = 74.074 L9 2.5 1.510 63.4 S15 = -300.882 0.2 S16=18.412 L10 5.0 1.510 63.4 S17 = 153.957 L11 1.5 1.806 40.7 S18 = 31.629 2.25 Aperture 26.614 S19 = -13.655 L12 1.5 1.773 49.6 S20 = -23.408 0.2 S21 = 93.578 L13 3.5 1.673 3.22 S22 = -193.289 EFL Z1 Z2 Z3 71.5mm 1.50mm 22.89mm 3.49mm 110.0 14.45 11.83 1.60 146.5 20.58 1.00 6.30 The invention may be embodied in various lens forms. Figure 4 shows a zoom lens having thirteen elements in three moving groups, G1, G2 and G3. The first two groups G1 and G2 comprise elements L1-L6 in configurations previously described. The third group G3 comprises a positive meniscus L7, a doublet L8, L9, a biconvex element L10, a negative meniscus L11 and a closely spaced biconvex element L12 and a negative meniscus concave to the object. This lens has only two internal variable spaces Z1 and Z2; however, the front group G1 moves forward as the EFL increases, thus increasing the front vertex distance (FVD).

Another embodiment of the invention according to Figure 4, scaled to an image frame of 24 x 36mm and having EFL's of 51.6mm to 145.3mm is substantially described in Table VII.

TABLE VII Axial Distance Element Surface Radii (mm) Between Surfaces (mm) Nd Vd S1 = 154.274 L1 2.000 1.805 25.5 82 = 60.625 L2 7.482 1.603 60.7 S3 = -166.752 0.200 S4= 49.425 L3 4.711 1.487 70.4 S5 = 976.009 Z1 S6 = -111.965 L4 1.500 1.834 37.3 S7 = 29.937 4.683 S8 = -40.282 L5 1.500 1.487 70.4 S9 = 34.267 L6 4.190 1.847 23.8 S10 = -661.409 Z2 S11 = 58.780 L7 3.370 1.785 25.7 S12 = 588.325 0.200 S13 = 40.593 L8 6.062 1.518 59.0 S14 = -38.790 L9 1.500 1.805 25.5 S15 = 60.207 0.200 S16 = 29.884 L10 4.661 1.603 60.7 Aperture 15.024 S17 = 47.488 L11 1.500 1.834 37.2 S18 = 17.934 0.309 S19 = 18.509 L12 5.462 1.632 34.8 S20 = -62.404 6.297 S21 = -19.946 L13 1.500 1.834 37.3 S22 = -58.480 EFL Z1 Z2 BFL 51.6mm 2.00mm 36.18mm 38.66mm 65.0 5.63 29.28 42.82 80.1 9.14 21.50 46.04 145.3 16.17 1.00 59.53 As previously pointed out, there are certain parameters which must be satisfied to achieve the close focusing capability with minimum focusing travel. Table VIII sets forth the important parameters of each lens.

TABLE VIII Table K1 F1 KL FL F1/FL 8s/B .0096 104.17 .0051 195 .534 0.26 il .0092 109.13 .0050 201 .543 0.31 Ill .0124 80.65 .0066 150 .538 0.75 IV .0091 109.89 .0049 203 .541 1.00 V .0100 100.0 .0052 194 .515 0.33 Vl .0131 76.1 .0068 146.5 .519 1.91 VII .0147 67.9 .0069 145.3 .468 0.57 where K1 is the power of group G1, F1 is the EFL of group G1, KL is the power of the lens at its longest EFL, FL is the longest EFL of the lens s is the power of the second component L3 of the group G1, D is the power of the first component L1, L2 of group G.

To maintain compactness of the lens, where the lens is of the four group form, the telephoto ratio of the fourth group is maintained at .8 or less. The telephoto ratio is the ratio of the front vertex distance of group G4to its EFL.

It may thus be seen that the objects of the invention set forth as well as those made apparent from the foregoing description are efficiently attained. While preferred embodiments of the invention have been set forth for purposes of disclosure, modification to the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments of the invention and modifications to the disclosed embodiments which do not depart from the spirit and scope of the invention.

Claims (1)

1. A zoom lens having a first group movable axially for focusing, a plurality of following groups movable axially of the lens to vary the equivalent focal length of the lens, said front focusing group comprising a positive doublet followed by a positive singlet 0 < 6s < 2.0 0D and .67 > F1 > .4 FL where 8s is the optical power of the singlet, 8D is the optical power of the doublet, F1 is the equivalent focal length of the first group, and FL is the maximum equivalent focal length of the lens.

2. A zoom lens according to claim 1, wherein a second group following said first group is of negative power, said second group being a variator group including a negative singlet and a negative doublet.

3. A lens according to claim 2 wherein said variator group consists of a negative singlet followed by a negative doublet.

4. A lens according to claim 2 wherein said variator group consists of a negative doublet followed by a negative singlet.

5. A lens according to claim 2, further comprising a third group, said third group comprising a biconvex doublet.

6. A lens as in claim 2 wherein said third group consists of a leading negative element followed by a positive element.

7. A lens according to claim 5 further including a fourth group, said fourth group comprising a positive subgroup followed by a negative subgroup with a large separating air-space.

8. A lens according to claim 7 wherein said first subgroup consists of a positive singlet followed by a positive doublet.

9. A lens according to claim 7 wherein said first subgroup consists of a positive doublet.

10. A lens according to claim 7 wherein said second subgroup consists of a positive lens followed by a negative lens.

11. A lens as in claim 6 wherein said second subgroup consists of a negative lens followed by a positive lens.

12. A zoom lens according to claim 1, wherein the following groups include a second lens group of negative power, said second group being a variator group including a negative singlet and a negative doublet; a third lens group of positive power, said third group being a compensator group including a positive doublet and a fixed positive fourth group.

13. A lens according to claim 1 scaled to an equivalent focal length of 101 mm to 195mm substantially as described.

Axial Distance Element Surface Radii (mm) Between Surfaces (mm) Nd Vd S1 = 69.077 L1 3.0 1.7847 26.06 S2 = 44.817 L2 10.0 1.5101 63.43 53 = -213.552 0.3 S4 = 92.077 L3 3.5 1.5101 63.43 S5 = 142.825 Z1 S6 = 600.754 L4 2.0 1.6583 57.26 S7 = 69.943

3.5 S8 -71.613 L5 2.0 1.6910 54.70 59 = 32.133 L6 4.76 1.8467 23.83 S10 = 76.984 Z2 S11 = 74.163 L7 2.0 1.7847 26.06 S12 = 39.674 L8 6.29 1.5638 60.83 S13 = -96.905 Z3 S14 = 78.588 L9 3.0 1.5101 63.43 S15 = 693.028 0.3 S16 = 26.460 L10 5.826 1.5101 63.43 S17 = 427.148 L11 2.0 1.8061 40.74 S18 = 45.219

4.81 Aperture Stop

40.26 S19 = -18.927 L12 2.0 1.7725 49.62 S20 = -53.001 0.3 S21 = 412.053 L13 3.42 1.6727 32.17 S22 = -53.841 EFL Z1 Z2 Z3 102mm 2.81mm 31.68mm 3.72mm 152 18.84 14.89 4.50 195 25.51 1.33 11.37 where the lens comprises elements L1-L13 having surfaces S1-S22, the index of refraction is given by Nd, the dispersion is measured by the Abbe number as given by Vd, and Z1, Z2 and Z3 are the variable air-spacings at the indicated equivalent focal length (EFL).

14. A lens according to claim 1 scaled to an equivalent focal length of 76.0mm to 200.1 mm substantially as described.

Axial Distance Element Surface Radii (mm) Between Surfaces (mm) Nd Vd S = 100.120 L1 3.0 1.785 26.1 S2 = 58.560 L2 7.34 1.510 63.4 S3 = plano 0.3 54 = 97.870 L3 5.15 1.510 63.4 S5 = -539.860 Z1 S6 = 205.760 L4 1.5 1.720 50.3 S7 = 70.027

3.74 S8 = -84.552 L5 1.5 1.720 50.3 S9 = 27.698 L6 4.51 1.785 25.7 S10 = 126.250 Z2 S11 = 104.624 L7 6.08 1.487 70.4 S12 = -32.924 L8 1.2 1.785 26.1 S13 = -51.566 Z3 S14 = 32.652 L9 6.24 1.573 57.5 S15 = -85.340 L10 2.0 1.806 40.7 S16 = 175.960

4.81 Aperture Stop

42.660 S17 = -19.451 L11 2.0 1.804 46.5 S18 = -37.265 0.3 S19 = 101.789 L12 2.27 1.673 3.22 S20 = -300.147 EFL Z1 Z2 Z3 76.00mm 1.73mm 37.58mm 12.09mm

125.00 26.25 23.15 2.00

20.0 39.92 1.48 10.00 where the lens comprises elements L1 -L1 2 having surfaces S1-S20, the index of refraction is given by Nd, the dispersion is measured by the Abbe number as given by Vd, and Z1, Z2 and Z3 are the variable air-spacings at the indicated equivalent focal length (EFL).

15. A lens according to claim 1 scaled to an equivalent focal length of 72mm to 150mm substantially as described.

Axial Distance Element Surface Radii (mm) Between Surfaces (mm) Nd Vd S1 = 62.296 L1 3.0 1.7847 26.06 S2 = 41.370 L2 12.806 1.4875 70.44 S3 = -266.277 0.3 S4 = 86.478 L3 4.095 1.4875 70.44 S5 = 2731.894 Z1 S6 = -259.053 L4 2.0 1.6910 54.70 S7 = 65.984

2.805 S8 = -71.603 L5 2.0 1.7433 49.22 S9 = 24.730 L6 4.755 1.8467 23.83 S10 = 72.248 Z2 S11=49.336 L7 2.0 1.8467 23.83 S12 = 25.951 L8 6.287 1.6667 48.30 S13= -133.121 Z3 S14 = 22.123 L9 5.381 1.4875 70.44 S15 = -684.989 L10 2.0 1.8042 46.50 S16 = 66.251

29.67 S17 = -14.503 L11 2.0 1.5310 58.20 S18 = -31.216 0.3 S19 = 120.523 L12 2.350 1.8040 46.50 S20 = -189.269 EFL Z1 Z2 Z3 72.0mm 1.6 27.051 0.3 111.0 14.289 13.162 1.5 150.0 19.843 0.3 8.809 where the lens comprises elements L1-L12 having surfaces S1-S20, the index of refraction is given by Nd, the dispersion is measured by the Abbe number as given by Vd, and Z1, Z2 and Z3 are the variable air-spacings at the indicated equivalent focal length (EFL).

16. A lens according to claim 1 scaled to an equivalent focal length of 72mm to 203mm substantially as described.

Axial Distance Element Surface Radii (mm) Between Surfaces (mm) Nd Vd S1 = 87.504 L1 3.000 1.7847 26.06 S2 = 57.456 L2 12.806 1.4875 70.44 S3 = -576.167 0.300 S4 = 110.904 L3 3.500 1.4875 70.44 S5 = -1960.632 Z1 S6 = -829.307 L4 2.000 1.6910 54.70 S7 = 84.246

3.075 S8 = -91.582 L5 2.000 1.7433 49.22 S9 = 29.357 L6 4.755 1.8467 23.83 S10 = 80.962 Z2 S11 =76.817 L7 2.000 1.8467 23.83 S12 = 36.571 L8 6.287 1.6667 48.30 S13 = -118.534 Z3 S14 = 25.919 L9 7.000 1.4875 70.44 S15 = -154.920 L10 2.000 1.8042 46.50 S16 = 92.608

39.753 S17 = -17.481 L11 2.000 1.8042 46.50 S18 = -37.440

2.029 S19 = 251.831 L12 2.452 1.7495 35.04 S20 = -69.558 EFL Z1 Z2 Z3 72.0mm 1.5mm 49.045mm 0.3mm 150.0 30.760 18.585 1.5 203.0 36.664 0.3 13.881 where the lens comprises elements L1 -L12 having surfaces S1-S20, the index of refraction is given by Nd, the dispersion is measured by the Abbe number as given by Vd, and Zi, Z2 and Z3 are the variable air-spacings at the indicated equivalent focal length (EFL).

17. A lens according to claim 1 scaled to an equivalent focal length of 101 mum to 194mm substantially as described.

Axial Distance Element Surface Radii (mm) Between Surfaces (mm) Nd Vd S1 = 70.981 L1 3.0 1.7847 26.06 S2 = 45.725 L2 10.0 1.5101 63.43 53 = -190.826 0.3 54 = 77.534 L3 3.5 1.5101 63.43 S5 = 115.121 Z1 S6 = -366.358 L4 3.829 1.8467 23.83 S7 = -49.175 L5 2.0 1.6910 54.70 S8 = 61.777

3.961 S9 = -53.090 L6 20 1.6583 57.26 S10 = 255.263 Z2 S11 = 93.727 L7 6.429 1.5638 60.83 S12 = -35.861 L8 2.0 1.7847 26.06 S13 = -71.255 Z3 S14 = 74.385 L9 2.629 1.5101 63.43 S15 = 259.362 0.3 S16 = 26.413 L10 5.653 1.5101 63.43 S17 = 366.100 L11 2.0 1.8061 40.74 S18 = 43.497

27.063 S19 = 112.212 L12 2.615 1.6727 32.17 S20 = -77.326

6.977 S21 = -24.455 L13 2.0 1.7725 49.62 S22 = -97.188 EFL Z1 Z2 Z3 101.0mm 2.812mm 29.314mm 3.744mm 152.0 18.190 13.176 4.503 194.0 24.580 0.3 10.990 where the lens comprises elements L1 -L13 having surfaces S1-S22, the index of refraction is given by Nd, the dispersion is measured by the Abbe number as given by Vd, and Zi, Z2 and Z3 are the variable air-spacings at the indicated equivalent focal length (EFL).

18. A lens according to claim 1 scaled to an equivalent focal length of 76mm to 201 mum substantially as described.

Axial Distance Element Surface Radii (mm) Between Surfaces (mm) Nd Vd S1 = 55.041 L1 2.50 1.785 26.1 S2 = 36.225 L2 8.50 1.510 63.4 S3 = -246.043 0.2 S4 = 86.032 L3 3.0 1.510 63.4 S5 = 380.808 Z1 S6 = -192.163 L4 1.5 1.658 57.3 S7 = 51.582

2.56 S8 = -63.000 L5 1.5 1.691 54.7 S9 = 21.990 L6 3.6 1.785 26.1 S10 = 67.930 Z2 S11 = 54.447 L7 1.5 1.785 26.1 S12 = 27.783 L8 5.5 1.540 59.7 S13 = -85.292 Z3 S14 = 74.074 L9 2.5 1.510 63.4 S15 = -300.882 0.2 S16 = 18.412 L10 5.0 1.510 63.4 S17 = 153.957 L11 1.5 1.806 40.7 S18 = 31.629

2.25 Aperture

26.614 S19 = -13.655 L12 1.5 1.773 49.6 S20 = -323.408 0.2 S21 = 93.578 L13 3.5 1.673 3.22 S22 = -193.289 EFL Z1 Z2 Z3 71.5mm 1.50mm 22.89mm 3.49mm 110.0 14.45 11.83 1.60 146.5 20.58 1.00 6.30 where the lens comprises elements L1 -L13 having surfaces S1 -S22, the index of refraction is given by Nd, the dispersion is measured by the Abbe number as given by Vd, and Z1, Z2 and Z3 are the variable air-spacings at the indicated equivalent focal length (EFL).

19. A lens according to claim 1 scaled to an equivalent focal length of 51.6mm to 145.3mm substantially as described.

Axial Distance Element Surface Radii (mm) Between Surfaces (mm) Nd Vd S1 = 154.274 L1 2.000 1.805 25.5 S2 = 60.625 L2 7.482 1.603 60.7 S3 = -166.752 0.200 S4 = 49.425 L3 4.711 1.487 70.4 S5 = 976.009 Z1 S6 = -111.965 L4 1.500 1.834 37.3 S7 = 29.937

4.683 S8 = -40.282 L5 1.500 1.487 70.4 S9 = 34.267 L6 4.190 1.847 23.8 S10= -661.409 Z2 S11=58.780 L7 3.370 1.785 25.7 S12 = 588.325 0.200 S13 = 40.593 L8 6.062 1.518 59.0 S14 = -38.790 L9 1.500 1.805 25.5 S15 = 60.207 0.200 S16 = 29.884 L10 4.661 1.603 60.7 Aperture

15.024 S17 = 47.488 L11 1.500 1.834 37.3 S18 = 17.934 0.309 S19 = 18.509 L12 5.462 1.632 34.8 S20 = -62.404

6.297 S21 = -19.946 L13 1.500 1.834 37.3 S22 = -58.480 EFL Z1 Z2 BFL 51.6mm 2.00mm 36.18mm 38.66mm 65.0 5.63 29.28 42.82 80.1 9.14 21.50 46.04 145.3 16.17 1.00 59.53 where the lens comprises elements L1-L13 having surfaces S1-S22, the index of refraction is given by Nd, the dispersion is measured by the Abbe number as given by Vd, and Z1 and Z2 are the variable air-spacings at the indicated equivalent focal length (EFL).

20. A zoom lens constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.