Zoom lens

Abstract

A zoom lens having a large zoom ratio and capable of close focusing comprising a first positive grouping movable axially for focusing, a second negative grouping, and a third positive grouping movable simultaneously with the second grouping, but in opposite directions to vary the equivalent focal length of the lens. The third grouping may have sub-groupings movable at different rates in the same direction.

Description

This invention relates to zoom lenses for photographic purposes and more particularly relates to a relatively compact zoom lens having a zoom ratio of substantially five to one which is useful in still photography as well as motion photography.

Photographic lenses having the above-stated zoom range typically suffer from excessive size, weight, and complexity which make these lenses impractical for use in what is commonly referred to as 35 mm photography; that is, an image frame of 24.times.36 mm.

Many examples of zoom lenses covering a normal to telephoto range are disclosed in the prior art. Most of these are of the mechanically compensated type with two moving groups. A maximum zoom ratio usually attainable in such a lens of reasonably small size is a three to one. However, once the zoom ratio extends over a three to one range, the front vertex distance of the lens as well as the diameter thereof begins to grow very quickly with increased zoom ratio. In the case of most lenses, compromise is achieved between the optical performance of the lens and its physical characteristics.

There have been attempts to provide zoom lenses having a large zoom ratio and a small relative aperture. However, none of them is really a compact lens allowing for convenient handling and operation.

Reducing the overall length of the lens usually requires increasing the power of the zooming and stationary groups in the lens. This consequently leads to increased surface aberrational contributions and adversely affects the performance and manufacturability of the lens. The faster the lens, that is, the lower the relative aperture, the more difficult it is to reduce its size because of increased surface aberrational contributions produced by the large apertures. The optical designer has to be very careful not to design a lens of theoretically high optical capability which will be impossible to produce economically because of sensitivity to manufacturing variations.

The relative aperture of the lens is commonly designated by the ratio of the equivalent focal length (EFL) of the lens to the diameter of the entrance pupil of this lens. It is well known that if the location of the aperture stop of the lens is allowed to move axially with change of EFL, such construction can help to reduce the size of the front group by altering the location of the entrance pupil of the lens as a function of EFL, and still allow for a reasonably high speed of the lens.

Accordingly, the present invention provides a new and improved zoom lens design of large zooming ratio while maintaining a relatively small absolute diameter and a short front vertex distance (FVD). Briefly stated, a zoom lens embodying the invention comprises three lens groupings. The first or front lens grouping is of positive optical power and is used for focusing by limited axial movement thereof. However, it is not moved axially in the zooming mode. A second movable group of negative power moves toward the image plane as the focal length is varied from the lower value to the upper value. A third group of positive power moves in the direction opposite to the motion of the second group during zooming. The aperture stop is located within this third movable group and for simplicity of mechanical construction of the lens may move together with the grouping as a whole. Further, in accordance with the invention, the third grouping can be further divided into two sub-groupings, both the first and second sub-groupings being of positive power. The rear sub-grouping achieves a favorable balance of aberration correction while maintaining minimum size and weight of the lens by having a ratio of front vertex distance (FVD) to equivalent focal length (EFL) between 0.75 and 1.4 and is comprised of three groups, positive, positive, and negative.

The various groups and groupings of the lens also have certain optical relationships as hereinafter pointed out.

Lenses embodying the invention may have zooming ranges of substantially five to one, with semi-field angles of about 26.degree. at the lower EFL ranging to less than 6.degree. in the extreme telephoto position. For 35 mm photography, this will provide a lens with a rated EFL range of 40-200 mm.

An object of this invention is to provide a new and improved relatively compact zom lens having an increased zoom ratio.

Another object of this invention is to provide a new and improved zoom lens of increased zoom ratio having a capability for very close focusing at any EFL by movement of only a front focusing group.

A further object of this invention is to provide a new and improved zoom lens having a wide range of equivalent focal lengths and relatively fast speeds.

The features of the invention which are believed to be novel are particularly pointed out and distinctly claimed in the concluding portion of this specification. However, the invention both as to its organization and operation together with further objects and advantages thereof may best be appreciated by reference to the following detailed description taken in conjunction with the drawings, in which:

FIGS. 1a-1b, 2a-2b, 3a-3b, 4a-4b, 5a-5b, 6a-6b, 7a-7b, 8a-8b, 9a-9b and 10a-10b are diagrammatic views of lenses embodying the invention where each lens is shown in different operating position in each pair of figures related by the same numeral.

A lens embodying the invention may be considered to have three major groupings, GPI, GPII, and GPIII. Grouping GPIII will be described as having sub-groupings SGIIIa and SGIIIb. Within sub-grouping SGIIIb will be described a lens comprised of three groups G31, G32, and G33 which are of positive, positive, negative power, successively from the object to image side.

All elements of a lens are identified by the reference L followed by successive numerals from the object end to the image end. All radii of the lens elements are from a point on the optical axis A of a lens and are identified by the reference R followed by successive numerals from the first object end lens surface to the last image end lens surface. The radii are positive when struck from the right and negative when struck from the left.

The spacings D1, D2, and D3 in the drawings are the spacings which vary in axial dimension as the lens groupings move during a change in EFL. FP indicates the focal or image plane of the lens.

Each lens is shown in its minimum EFL position by a figure number followed by (a), and its maximum EFL position by a figure number followed by (b).

A lens embodying the invention, as shown in FIGS. 1a and 1b, comprises a first grouping GPI of positive power which is movable for focusing, but stationary during zooming and comprises elements L1, L2, and L3; a second negative grouping GPII of negative power which moves toward the image plane as the equivalent focal length of the lens is increased and comprises elements L4, L5, and L6; and a third positive grouping GPIII which moves toward the object as the equivalent focal length is increased, and comprises elements L7-L13.

L1, a bi-concave element, and L2, a bi-convex element form a doublet of overall negative power due to the large index of refraction of L1. L3, a bi-convex element, renders GPI of overall positive power.

Elements L4 and L5 are a doublet of overall negative power with L5 bi-concave. Grouping GPII further includes bi-concave element L6.

In the examples and FIGS. 1a and 1b, Grouping GPIII comprises two sub-groupings SGIIIa and SGIIIb. Sub-grouping SGIIIa is of positive power comprising a positive element L7 convex to the object with a large image side radius surface, and a very weak doublet L8, L9. Sub-grouping SGIIIb comprises a positive group G31 in the form of an element having a convex object side surface and an image side surface of much greater radius; a positive group G32 comprising elements L11 and L12; and a negative group G33 in the form of a negative meniscus L13, concave to the object.

To maintain the compact size and yet to allow for reasonably loose tolerances in manufacturing of this lens, the power of the sub-grouping SGIIIb should satisfy the following condition: ##EQU1##

Front vertex distance of FVD.sub.IIIb refers to the distance of the first object side surface of the rear sub-grouping SGIIIb to the focal plane when this subgrouping alone is focused at infinity.

If the upper limit is increased, the size of the lens becomes too big to allow for a compact, easy-to-handle package. On another hand, when the above-mentioned ratio becomes smaller than the lower limit, then the individual lens elements become very sensitive to manufacturing variations leading to increased difficulties producing the lens.

To achieve a favorable balance of aberrations, the sub-grouping SGIIIb is comprised of three groups G31, G32, and G33 of positive, positive, and negative optical power wherein the last group has meniscus shape concave towards the object.

Group G32 generally serves as an aberration corrector and may have a wide range of powers as hereinafter made apparent. Also, the absolute ratio of the power of groups G31 to G33 is of importance, as hereinafter pointed out.

FIGS. 1a and 1b illustrate a lens embodying the invention at its extreme lower and upper equivalent focal lengths respectively. The axial spaces D1, D2, and D3 vary to change the EFL as hereinafter stated.

A lens as shown in FIGS. 1a and 1b, which has a zoom range to subtend semi-field angles of 22.8.degree. to 6.3.degree., as scaled to an image frame of 24 mm.times.36 mm, and an EFL of 51.5 mm to 195 mm is set forth in Table I. BFL is the back focal length.

TABLE I______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = -331.909L1 2.000 1.847 23.8 R2 = 77.893L2 8.325 1.531 50.9 R3 = -105.577 0.200 R4 = 75.550L3 5.264 1.741 35.1 R5 = -738.126 1.000 (D1) R6 = -273.757L4 4.990 1.847 23.8 R7 = -39.174L5 2.000 1.697 55.5 R8 = 74.538 4.086 R9 = -53.121L6 1.500 1.697 55.5 R10 = 148.879 49.510 (D2) R11 = 46.961L7 4.902 1.608 40.0 R12 = -929.669 0.200 R13 = 726.860L8 6.485 1.587 51.7 R14 = -31.445L9 1.500 1.847 23.8 R15 = -260.591 10.825 (D3) R16 = 23.960L10 8.148 1.517 69.7 R17 = 249.885 11.397 R18 = 64.858L11 1.500 1.804 46.5 R19 = 16.770 0.467 R20 = 18.004L12 6.440 1.648 33.8 R21 = -46.653 2.692 R22 = -18.862L13 1.500 1.834 37.3 R23 = -106.740BFL = 40.106______________________________________

In the foregoing Table I, the iris defining the aperture stop is located between elements L6 and L7 and moves with sub-grouping SGIIIa. Positive radii are struck from the right and negative radii are struck from the left.

The spacings of the groupings at different equivalent focal lengths are given below in Table II.

TABLE II______________________________________EFL______________________________________Spacing 51.5 mm 85.00 mm 135.00 mm 195.00 mmD1 1.000 mm 15.525 mm 25.714 mm 31.992 mmD2 49.310 mm 31.944 mm 15.651 mm 2.000 mmD3 10.825 mm 5.460 mm 2.224 mm .500 mmf/No. 2.88 3.35 3.73 4.12______________________________________

The relative aperture as exemplified by f/No. varies from 2.9 at the lower EFL to 4.1 at the higher EFL due to the moving aperture stop, while the iris diameter stays fixed.

Thirteen examples of the invention are disclosed, and for purposes of comparison, the organization of the elements are set forth below.

TABLE III______________________________________TABLE GP1 GPII SGIIIa SGIIIb G31 G32 G33______________________________________I L1-L3 L4-L6 L7-L9 L10-L13 L10 L11, L13 L12IV & VI L1-L3 L4-L6 L7-L9 L10-L14 L10 L11, L13, L12 L14X L1-L3 L4-L7 L8-L10 L11-L15 L11 L12, L14, L13 L15VIII L1-L3 L4-L6 L7, L8 L9-L12 L9 L10, L12 L11XII & L1-L3 L4-L6 L7-L9 L10-L14 L10 L11, L13,XIV L12 L14XVI L1-L3 L4-L6 L7-L9 L10-L14 L10 L11, L13, L12 L14XVIII L1-L3 L4-L6 L7-L9 L10-L13 L10 L11, L13 L12XX L1-L3 L4-L6 L7-L9 L10-L14 L10 L11, L13, L12 L14XXII L1-L3 L4- L6 L7-L10 L10-L14 L10 L11, L13 L12XXIV & L1-L3 L4-L6 L7-L9 L10-L15 L10, L12, L14,XXV L11 L13 L15______________________________________

Another embodiment of the invention is set forth in FIGS. 2a and 2b. The structural form of the lenses differs in that grouping GPI has a first bi-convex element L1 followed by a bi-convex doublet L3, L4. Grouping GPII comprises a first bi-concave element L4 followed by a negative doublet L5, L6 with L5 bi-concave. Group G32 comprises a negative meniscus L11 and a spaced bi-convex element L12. Group G33 comprises a bi-concave element L13 and a bi-convex element L14.

The prescriptions of two lenses of this form are set forth in Tables IV and V. In both examples, the lens sub-tends a semi-field angle varying from 22.8.degree. to 6.3.degree., and is scaled for a 24.times.36 mm image frame with an EFL range of 51.5 mm to 195.5 mm.

TABLE IV______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refrac- No.ment Curvature (mm) (mm) tion N.sub.d V.sub.d______________________________________ R1 = 91.606L1 6.157 1.517 69.7 R2 = -204.977 0.200 R3 = 99.209L2 6.256 1.487 70.4 R4 = -121.897L3 2.000 1.847 23.8 R5 = -1311.231 1.000 (D1) R6 = -207.668L4 1.500 1.713 53.9 R7 = 39.369 4.571 R8 = -48.686L5 2.000 1.697 55.5 R9 = 39.043L6 4.988 1.847 23.8 R10 = -564.889 46.831 (D2) R11 = 54.481L7 5.338 1.607 56.7 R12 = -374.746 0.200 R13 = 77.405L8 7.895 1.581 40.9 R14 = -36.501L9 1.500 1.847 23.8 R15 = 194.707 9.109 (D3) R16 = 26.911L10 8.076 1.525 60.0 R17 = -1041.865 9.346 R18 = 52.178L11 1.838 1.559 64.4 R19 = 21.897 3.425 R20 = 28.087L12 5.298 1.627 34.6 R21 = -62.138 2.562 R22 = -23.600L13 1.500 1.834 37.3 R23 = 28.021 0.445 R24 = 28.914L14 4.385 1.619 35.4 R25 = -118.264BFL = 38.539______________________________________ TABLE V______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refrac- No.ment Curvature (mm) (mm) tion N.sub.d V.sub.d______________________________________ R1 = 101.687L1 7.471 1.487 70.4 R2 = -198.419 0.200 R3 = 95.447L2 7.353 1.487 70.4 R4 = -139.520L3 2.000 1.805 25.5 R5 = -5325.160 2.883 (D1) R6 = -190.880L4 1.500 1.773 49.7 R7 = 48.001 5.742 R8 = -58.215L5 2.000 1.697 55.5 R9 = 42.255L6 4.992 1.847 23.8 R10 = 2180.742 50.035 (D2) R11 = 154.385L7 3.104 1.847 23.8 R12 = -536.964 0.200 R13 = 34.221L8 8.851 1.487 70.4 R14 = -42.312L9 1.500 1.805 25.5 R15 = 124.660 5.006 (D3) R16 = 27.114L10 5.691 1.581 40.9 R17 = 167.817 6.077 R18 = 35.204L11 1.500 1.847 23.8 R19 = 22.920 1.620 R20 = 36.325L12 6.578 1.541 47.2 R21 = -83.500 8.928 R22 = -18.143L13 1.500 1.834 37.3 R23 = 114.343 0.617 R24 = 278.786L14 3.152 1.847 23.8 R25 = -35.211BFL = 38.552______________________________________

In Table IV the iris defining the aperture stop is located between elements L6 and L7, and moves with sub-grouping SGIIIa.

The spacings of the groupings at different equivalent focal lengths are given below in Table VI.

TABLE VI______________________________________EFL______________________________________Spacing 51.5 mm 85.00 mm 135.00 mm 195.00 mmD1 1.000 mm 13.307 mm 22.522 mm 27.537 mmD2 46.831 mm 30.407 mm 14.997 mm 2.000 mmD3 9.109 mm 4.571 mm 2.208 mm .500 mmf/No. 2.9 3.35 3.73 4.1______________________________________

In Table V, the iris defining the aperture stop is located between elements L10 and L11 and moves with sub-grouping SGIIIb.

The spacings of the groupings at different equivalent focal lengths are given below in Table VII.

TABLE VII______________________________________EFL______________________________________Spacing 51.5 mm 85.00 mm 135.00 mm 195.00 mmD1 2.883 mm 14.285 mm 23.334 mm 28.899 mmD2 50.035 mm 31.496 mm 15.039 mm 1.000 mmD3 5.006 mm 2.782 mm .994 mm .500 mmf/No. 2.95 3.5 3.7 4.1______________________________________

Another embodiment of the invention as shown in FIGS. 3a and 3b utilizes only twelve elements L1-L12. This embodiment differs primarily in that sub-groupings SGIIIa comprises only a bi-convex doublet L7, L8. Also, the forward components L10, L11 of group G3 are a doublet comprising a forward (object side) bi-convex element L10, and a rear meniscus L11. Grouping GPI again comprises three elements, but here in the form of a convex object side meniscus L1 and a bi-convex element L2 forming a doublet, followed by a positive meniscus L3, convex to the object.

The prescription of this lens is set forth in Table VIII. The lens subtends a semi-field angle of 22.8.degree. to 6.3.degree., and is scaled for an image plane of 24.times.36 mm with an EFL range of 51.5 mm to 195 mm.

TABLE VIII______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refrac- No.ment Curvature (mm) (mm) tiom N.sub.d V.sub.d______________________________________ R1 = 311.481L1 2.000 1.847 23.8 R2 = 68.476L2 9.718 1.589 62.6 R3 = -108.672 0.200 R4 = 50.060L3 4.222 1.690 31.0 R5 = 84.784 2.822 (D1) R6 = 508.164L4 5.563 1.847 23.8 R7 = -47.257L5 2.000 1.696 55.1 R8 = 41.931 5.239 R9 = -38.143L6 1.500 1.711 53.9 R10 = Infinity 47.717 (D2) R11 = 59.518L7 7.648 1.571 51.1 R12 = -30.945L8 1.500 1.831 24.2 R13 = -106.827 4.906 (D3) R14 = 22.295L9 7.351 1.487 70.4 R15 = 85.618 18.021 R16 = 54.725L10 5.731 1.631 34.2 R17 = -16.627L11 1.500 1.806 40.7 R18 = -68.855 2.363 R19 = -19.620L12 1.500 1.806 40.7 R20 = -53.856BFL = 38.547______________________________________

In the foregoing Table VIII, the iris defining the aperture stop is located between elements L6 and L7. Positive radii are struck from the right and negative radii are struck from the left.

The spacings of the groupings at different equivalent focal lengths are given below in Table IX.

TABLE IX______________________________________EFL______________________________________Spacing 51.5 mm 85.00 mm 135.00 mm 195.00 mmD1 2.822 mm 12.015 mm 25.282 mm 29.739 mmD2 47.717 mm 30.486 mm 15.603 mm 2.000 mmD3 4.906 mm 1.699 mm .788 mm .500 mmf/No. 2.8 3.3 3.6 4.0______________________________________

FIGS. 4a and 4b disclose an embodiment of the invention where the grouping GPI takes the same form as in FIGS. 2a-2b. However, grouping GPII includes a positive meniscus L5 behind the bi-concave element L4. Group G32 of sub-grouping SGIIIb comprises a bi-convex doublet L12, L13 followed by bi-concave element L14 and bi-convex element L15 of overall combined negative power.

This lens as further set forth in Table X has a lower EFL which is less than the diagonal of the image frame. The lens subtends semi-field angles of 27.8.degree. to 6.3.degree., and is scaled for a 24.times.36 mm image frame, with an EFL range of 41.00 mm to 195.00 mm.

TABLE X______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 87.088L1 6.073 1.487 70.4 R2 = -357.220 0.200 R3 = 81.894L2 6.904 1.517 69.7 R4 = -113.558L3 2.000 1.805 25.5 R5 = -741.212 1.000 (D1) R6 = -145.203L4 2.000 1.850 32.2 R7 = 29.227 5.027 R8 = -40.720L5 3.218 1.617 36.6 R9 = -28.743 0.329 R10 = -34.696L6 2.000 1.620 60.3 R11 = 30.644L7 4.602 1.847 23.8 R12 = -836.811 47.970 (D2) R13 = 244.236L8 3.347 1.847 23.8 R14 = -159.720 0.200 R15 = 37.449L9 7.464 1.487 70.4 R16 = -59.792L10 1.500 1.847 23.8 R17 = 128.574 14.245 (D3) R18 = 34.377L11 7.312 1.694 53.3 R19 = 125.375 12.722 R20 = 40.777L12 1.500 1.834 37.3 R21 = 17.194L13 8.377 1.529 51.6 R22 = -45.367 4.500 R23 = -23.943L14 1.500 1.850 32.2 R24 = 50.260 0.724 R25 = 56.060L15 3.971 1.847 23.8 R26 = -75.126BFL = 38.556______________________________________

In the foregoing Table X, the iris defining the aperture stop is located between elements L7 and L8 and moves with sub-grouping SGIIIa. Positive radii are struck from the right and negative radii are struck from the left.

The variable spacings of the groupings at different equivalent focal lengths are given below in Table XI.

TABLE XI______________________________________EFL______________________________________Spacing 41.0 mm 85.00 mm 135.00 mm 195.00 mmD1 1.000 mm 17.567 mm 26.928 mm 31.136 mmD2 47.970 mm 26.960 mm 13.815 mm 2.000 mmD3 14.245 mm 4.978 mm 2.626 mm .500 mmf/No. 2.95 3.5 3.7 4.1______________________________________

FIGS. 5a and 5b illustrate another lens embodying the invention where GP1 comprises a bi-convex doublet L1, L2 with L1 being a negative meniscus, and L2 is a positive with its shortest radius being convex to the object. Group G32 comprises a negative meniscus L11, and a bi-convex element L12 of overall positive power. Group G33 is a doublet comprising a bi-concave element L13 and a bi-convex element L14 of overall negative power.

Prescriptions of two lenses of this form are set forth in Tables XII and XIII. Both lenses subtend semi-field angles of 22.8.degree. to 6.3.degree., and are scaled to an image frame of 24.times.36 mm, with an EFL range of 51.5 mm to 195.0 mm.

TABLE XII______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 51.685L1 2.000 1.728 28.7 R2 = 35.419L2 11.322 1.487 70.4 R3 = -300.792 0.200 R4 = 70.392L3 4.236 1.487 70.4 R5 = 260.451 2.174 (D1) R6 = -218.893L4 1.500 1.773 49.6 R7 = 33.369 5.032 R8 = -50.332L5 1.500 1.697 55.5 R9 = 29.315L6 5.544 1.847 23.8 R10 = 372.944 39.191 (D2) R11 = 278.949L7 3.349 1.785 25.7 R12 = -112.134 0.200 R13 = 37.648L8 8.126 1.487 70.4 R14 = -46.741L9 1.500 1.728 28.7 R15 = 130.107 12.937 (D3) R16 = 30.554L10 5.344 1.589 61.3 R17 = 161.993 9.765 R18 = 53.104L11 1.500 1.805 25.5 R19 = 26.732 0.998 R20 = 35.956L12 4.621 1.603 60.7 R21 = -86.528 10.000 R22 = -20.688L13 1.200 1.773 49.6 R23 = 36.746L14 6.262 1.673 32.2 R24 = -36.746BFL = 38.550______________________________________ TABLE XIII______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refrac- No.ment Curvature (mm) (mm) tion N.sub.d V.sub.d______________________________________ R1 = 100.000L1 2.000 1.847 23.8 R2 = 61.777L2 8.540 1.487 70.4 R3 = -139.015 0.200 R4 = 57.007L3 4.333 1.487 70.4 R5 = 141.831 1.774 (D1) R6 = -219.606L4 1.500 1.773 49.7 R7 = 42.712 4.608 R8 = -50.056L5 2.000 1.697 55.5 R9 = 39.784L6 4.992 1.847 23.8 R10 = -1453.300 47.246 (D2) R11 = 93.289L7 3.836 1.805 25.5 R12 = -218.835 0.200 R13 = 37.170L8 7.645 1.487 70.4 R15 = -60.263L9 1.500 1.847 23.8 R15 = 74.160 8.989 (D3) R16 = 28.233L10 5.691 1.583 45.7 R17 = 161.805 8.196 R18 = 41.946L11 1.500 1.847 23.8 R19 = 23.983 1.133 R20 = 33.166L12 4.571 1.532 48.8 R21 = -115.744 11.000 R22 = -18.977L13 1.500 1.834 37.3 R23 = 73.633 0.505 R24 = 94.636L14 5.041 1.785 25.7 R25 = -31.880BFL = 38.550______________________________________

In the foregoing Table XII, the iris defining the aperture stop is located between elements L6 and L7. Positive radii are struck from the right and negative radii are struck from the left.

The spacings of the groupings at different equivalent focal lengths are given below in Table XIV.

TABLE XIV______________________________________EFL______________________________________Spacing 51.5 mm 85.00 mm 135.00 mm 195.00 mmD1 2.174 mm 12.738 mm 18.123 mm 22.250 mmD2 39.191 mm 25.950 mm 12.813 mm 2.000 mmD3 12.937 mm 8.055 mm 3.253 mm .500 mmf/No. 2.95 3.5 3.7 4.1______________________________________

In the foregoing Table XIII, the iris defining the aperture stop is located between elements L10 and L11 and moves with sub-grouping SGIIIb. Positive radii are struck from the right and negative radii are struck from the left.

The spacings of the groupings at different equivalent focal lengths are given below in Table XV.

TABLE XV______________________________________EFL______________________________________Spacing 51.5 mm 85.00 mm 135.00 mm 195.00 mmD1 1.774 mm 12.804 mm 23.690 mm 28.070 mmD2 47.246 mm 30.473 mm 15.272 mm 2.000 mmD3 8.989 mm 4.084 mm 2.537 mm .500 mmf/No. 2.95 3.5 3.7 4.1______________________________________

FIGS. 6a and 6b exemplify another embodiment of the invention which differs from the others primarily in that group G33 is a negative meniscus L14, concave to the object. Group G32 comprises a positive meniscus L11, a negative meniscus L12 fairly strongly concave to the image and a bi-convex positive element L13.

The lens subtends semi-field angles of 22.8.degree. to 6.3.degree.. A prescription of the lens as scaled to an image frame of 24.times.36 mm with an EFL range of 51.5 mm to 195.00 mm is given in Table XVI.

TABLE XVI______________________________________ Axial Distance Index of Abbe Radius of Between Surfaces Refrac- No.Element Curvature (mm) (mm) tion N.sub.d V.sub.d______________________________________ R1 = 94.324L1 6.157 1.517 69.7 R2 = -225.278 0.200 R3 = 107.461L2 6.256 1.487 70.4 R5 = -125.129L3 2.000 1.847 23.8 R5 = -998.950 1.000 (D1) R6 = -175.603L4 1.500 1.713 53.9 R7 = 42.006 4.571 R8 = -55.596L5 2.000 1.697 55.5 R9 = 38.480L6 4.988 1.847 23.8 R10 = -2603.400 46.933 (D2) R11 = 57.230L7 5.338 1.607 56.7 R12 = -355.668 0.200 R13 = 97.881L8 7.895 1.581 40.9 R15 = -38.031L9 1.500 1.847 23.8 R15 = 383.703 10.275 (D3) R16 = 26.072L10 8.076 1.517 69.7 R17 = 264.855 11.774 R18 = 57.188L11 2.581 1.487 70.4 R19 = 157.667 0.588 R20 = 132.141L12 1.500 1.786 43.9 R21 = 17.553 0.559 R22 = 18.852L13 6.418 1.648 33.8 R23 = -54.308 2.694 R24 = -20.096L14 1.500 1.800 42.3 R25 = -96.886BFL = 38.540______________________________________

The lens of the foregoing Table XVI has an iris defining an aperture stop between elements L6 and L7 which moves with sub-grouping SGIIIa. Positive radii are struck from the right and negative radii are struck from the left.

The spacings of the movable elements at different EFL's are given below.

TABLE XVII______________________________________EFL______________________________________Spacing 51.5 mm 85.00 mm 135.00 mm 195.00 mmD1 1.000 mm 13.397 mm 23.707 mm 29.111 mmD2 46.933 mm 30.323 mm 14.940 mm 2.000 mmD3 10.275 mm 5.303 mm 2.400 mm .500 mmf/No. 2.8 3.35 3.73 4.12______________________________________

FIGS. 7a and 7b show an embodiment of the invention where grouping GPI includes a doublet comprising negative meniscus L1 and bi-convex element L2, followed by bi-convex element L3. Grouping GPII comprises bi-concave element L4 and a bi-concave doublet L5, L6. Grouping GPIII includes a first sub-grouping SGIIIa comprising a positive element L7, and convex-concave doublet L8, L9; and sub-grouping SGIIIb which comprises a bi-convex element L10, a negative meniscus L11 convex to the object side with a bi-convex element L12, and finally a negative meniscus L13 convex to the image side.

This lens as further set forth in Table XVIII has a lower EFL of 51.5 mm and an upper EFL of 150 mm. The exampled lens subtends semi-field angles of 22.8.degree. to 8.2.degree. as scaled to an image frame of 24.times.36 mm.

TABLE XVIII______________________________________ Axial Distance Index of Abbe Radius of Between Surfaces Refrac- No.Element Curvature (mm) (mm) tion N.sub.d V.sub.d______________________________________ R1 = 43.818L1 2.00 1.805 25.5 R2 = 30.325L2 9.03 1.487 70.4 R3 = 660.800 0.20 R4 = 57.757L3 4.58 1.487 70.4 R5 = -2198.63 2.00 (D1) R6 = -172.476L4 1.50 1.786 43.9 R7 = 23.666 4.44 R8 = -37.599L5 1.50 1.487 70.4 R9 = 27.572L6 4.19 1.847 23.8 R10 = 215.640 28.88 (D2) R11 = 58.063L7 2.76 1.785 25.7 R12 = 451.184 .20 R13 = 40.879L8 6.43 1.487 70.4 R14 = -30.890L9 1.50 1.805 25.3 R15 = 179.032 4.64 (D3) R16 = 26.196L10 5.72 1.487 70.4 R17 = -122.438 11.13 R18 = 54.654L11 1.50 1.834 37.3 R19 = 17.104 0.37 R20 = 17.908L12 5.14 1.626 35.5 R21 = -77.945 5.29 R22 = -17.046L13 1.50 1.743 49.2 R23 = 40.228 38.50 (D4)______________________________________

In the foregoing Table XVIII the iris defining the aperture is located between elements L6 and L7 and moves with sub-grouping SGIIIa. Positive radii are struck from the right and negative radii are struck from the left.

The variable spacings of the grouping at different EFL are given below in Table XIX.

TABLE XIX______________________________________EFL______________________________________Spacing 51.5 mm 75 mm 100 mm 145 mmD1 2.0 mm 10.19 mm 12.71 mm 16.24 mmD2 27.88 mm 19.27 mm 11.31 mm 1.00 mmD3 4.64 mm 2.98 mm 1.75 mm 0.50 mmD4 38.50 mm 40.58 mm 47.24 mm 55.28 mmf/No. 3.2 3.3 3.7 4.1______________________________________

Another lens having fourteen elements and embodying the invention shown in FIGS. 8a-8b has the same general configuration as shown in FIGS. 5a and 5b with the exception that element L3 is bi-convex. This lens is set forth in Table XX. This lens has a lower EFL less than the diagonal of the image plane. This lens subtends semi-field angles of 29.6.degree. to 8.4.degree.. This lens as scaled to EFL's of 38.0 mm to 146.0 mm for an image frame of 24.times.36 mm is defined as follows:

TABLE XX______________________________________ Axial Distance Index of Abbe Radius of Between Surfaces Refrac- No.Element Curvature (mm) (mm) tion N.sub.d V.sub.d______________________________________ R1 = 84.075L1 2.000 1.824 32.4 R2 = 35.070L2 10.644 1.487 70.4 R3 = Infinity 0.200 R4 = 42.216L3 7.293 1.640 60.2 R5 = -551.202 1.417 (D1) R6 = 3577.318L4 1.500 1.773 49.6 R7 = 22.455 4.403 R8 = -36.651L5 1.500 1.697 55.5 R9 = 23.130L6 4.494 1.847 23.8 R10 = 305.162 27.789 (D2) R11 = 182.035L7 3.349 1.805 25.5 R12 = -83.526 .200 R13 = 31.013L8 6.560 1.487 70.4 R14 = -39.407L9 1.500 1.789 27.5 R15 = 83.438 19.239 (D3) R16 = 24.898L10 5.344 1.592 60.5 R17 = 131.219 4.888 R18 = 51.764L11 1.500 1.805 25.5 R19 = 22.511 1.477 R20 = 32.129L12 6.196 1.599 62.1 R21 = -44.403 6.00 R22 = -18.935L13 1.200 1.764 47.9 R23 = 31.004L14 7.807 1.692 36.9 R24 = -31.715BFL = 38.572______________________________________

In the foregoing Table XX, the iris defining the aperture stop is located between elements L6 and L7 and moves with sub-grouping SGIIIa. Positive radii are struck from the right and negative radii are struck from the left.

The variable spacings of the grouping at different EFL's are given below in Table XXI.

TABLE XXI______________________________________EFL______________________________________Spacing 38.0 mm 70.0 mm 110.0 mm 146.0 mmD1 1.417 mm 12.00 mm 17.61 mm 20.09 mmD2 28.58 mm 16.89 mm 8.25 mm 2.80 mmD3 19.24 mm 10.30 mm 4.49 mm .50 mmf/No. 2.95 3.32 3.7 4.1______________________________________

Another lens embodying the invention shown in FIGS. 9a and 9b has the same overall configuration as shown in FIGS. 7a and 7b. However, the lens as set forth in Table XXII has no relative movement between the sub-groupings of Grouping GPIII during zooming. This lens has elements L1-L13 as more specifically set forth in Table XXII.

The lens of Table XXII has an EFL range of 51.5 mm to 145.0 mm as scaled to an image frame of 24.times.36 mm with semi-field angles of 22.8.degree. to 8.5.degree..

TABLE XXII______________________________________ Axial Distance Index of Abbe Radius of Between Surfaces Refrac- No.Element Curvature (mm) (mm) tion N.sub.d V.sub.d______________________________________ R1 = 154.274L1 2.000 1.805 25.5 R2 = 60.625L2 7.482 1.603 60.7 R3 = 166.752 0.200 R4 = 49.425L3 4.711 1.487 70.4 R5 = 976.009 2.000 (D1) R6 = -111.965L4 1.500 1.834 37.3 R7 = 29.937 4.683 R8 = -40.282L5 1.500 1.487 70.4 R9 = 34.267L6 4.190 1.847 23.8 R10 = -661.409 37.179 (D2) R11 = 58.780L7 3.370 1.785 25.7 R12 = 588.325 0.200 R13 = 40.593L8 6.062 1.518 59.0 R14 = -38.790L9 1.500 1.805 25.5 R15 = 60.207 0.200 R16 = 29.884L10 4.661 1.603 60.7 R17 = Infinity 15.024 R18 = 47.488L11 1.500 1.834 37.3 R19 = 17.934 0.309 R20 = 18.509L12 5.462 1.632 34.8 R21 = -62.404 6.267 R22 = -19.946L13 1.500 1.834 37.3 R23 = -58.480BFL = 38.590______________________________________

In the foregoing Table XXII, the iris defining the aperture stop is located between elements L6 and L7, and moves with grouping GPIII. Positive radii are struck from the right and negative radii are struck from the left.

The variable spacings of the grouping at different EFL's are given in Table XXIII.

TABLE XXIII______________________________________EFL______________________________________Spacing 51.5 mm 65.00 mm 80.00 mm 145.00 mmD1 2.00 mm 5.63 mm 9.14 mm 16.17 mmD2 37.8 mm 29.28 mm 21.50 mm 2.00 mmf/No. 3.2 3.48 3.61 4.12______________________________________

Another embodiment of the invention as shown in FIGS. 10a and 10b utilizes fifteen elements L1-L15. This embodiment differs primarily in that group G31 of sub-groupings SGIIIa comprises an additional element in the form of a positive meniscus L11, convex to the object. Groupings GPI and GP2 and sub-grouping SGIIIa again each comprise three elements.

The prescriptions of two lenses of this form are set forth in Tables XXIV and XXV. In the example of Table XXIV, the lens sub-tends a semi-field angle varying from 22.7.degree. to 6.4.degree., and is scaled for a 24.times.36 mm image frame with an EFL range of 51.53 mm to 194.98 mm. In the example of Table XXV, the lens sub-tends a semi-field angle varying from 22.8.degree. to 6.4.degree., and is scaled for a 24.times.36 mm image frame with an EFL range of 51.44 mm to 194.05 mm.

TABLE XXIV______________________________________ Axial Distance Index of Abbe Radius of Between Surfaces Refrac- No.Element Curvature (mm) (mm) tion N.sub.d V.sub.d______________________________________ R1 = 61.614L1 3.000 1.805 25.5 R2 = 43.179L2 11.800 1.487 70.4 R3 = -262.146 0.200 R4 = 57.758L3 3.500 1.487 70.4 R5 = 84.442 32.117 (D1) R6 = -1317.271L4 1.500 1.804 46.5 R7 = 36.278 5.516 R8 = -44.483L5 1.500 1.773 49.6 R9 = 34.734L6 5.000 1.847 23.8 R10 = -219.127 3.250 (D2) R11 = 234.035L7 3.350 1.699 30.1 R12 = -89.453 0.200 R13 = 43.887L8 6.600 1.487 70.4 R14 = -58.165L9 1.500 1.785 26.1 R15 = 117.280 1.000 (D3) R16 = 43.796L10 4.200 1.487 70.4 R17 = 1423.188 0.200 R18 = 25.838L11 5.600 1.487 70.4 R19 = 64.901 4.495 R20 = 27.729L12 2.000 1.805 25.5 R21 = 18.696 8.570 R22 = 72.878l13 4.900 1.487 70.4 R23 = -31.396 2.125 R24 = -23.175L14 1.200 1.804 46.5 R25 = 43.273 0.571 R26 = 46.400L15 3.900 1.805 25.5 R27 = -124.368______________________________________ TABLE XXV______________________________________ Axial Distance Index of Abbe Radius of Between Surfaces Refraction No.Element Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 76.881L1 3.000 1.805 25.5 R2 = 48.966L2 12.250 1.487 70.4 R3 = -164.561 0.210 R4 = 45.744L3 3.500 1.517 64.2 R5 = 64.414 30.449 (D1) R6 = 230.226L4 1.500 1.713 53.9 R7 = 32.025 5.200 R8 = -39.590L5 1.500 1.773 49.6 R9 = 36.704L6 5.000 1.847 23.8 R10 = -235.177 3.750 (D2) R11 = -166.537L7 2.800 1.785 26.1 R12 = -72.127 0.200 R13 = 46.928L8 7.300 1.487 70.4 R14 = -50.494L9 1.500 1.785 26.1 R15 = 526.365 1.010 (D3) R16 = 64.334L10 4.200 1.487 70.4 R17 = -211.416 0.200 R18 = 29.665L11 5.450 1.487 70.4 R19 = 76.428 9.370 R20 = 26.516L12 2.000 1.847 23.8 R21 = 19.733 6.680 R22 = 64.036L13 5.200 1.487 70.4 R23 = -30.409 1.280 R24 = -25.289L14 1.200 1.804 46.5 R25 = 52.130 3.230 R26 = 62.262L15 4.280 1.805 25.5 R27 = -189.602______________________________________

In the foregoing Table XXIV the iris defining the aperture stop is located between elements L6 and L7, and moves with sub-groupings SGIIIa. Positive radii are struck from the right and negative radii are struck from the left.

The spacings of the groupings at different equivalent focal lengths are given below in Table XXVI.

TABLE XXVI______________________________________EFL______________________________________Spacing 51.35 mm 85.07 mm 135.12 mm 194.98 mmD1 32.12 mm 27.15 mm 15.69 mm 2.71 mmD2 3.25 mm 13.17 mm 24.65 mm 37.62 mmD3 1.00 6.00 mm 12.30 mm 22.24 mmf/No. 2.91 3.40 3.75 4.15______________________________________

In Table XXV, the iris defining the aperture stop is located between elements L6 and L7 and moves with sub-grouping SGIIIa. Positive radii are struck from the right and negative radii are struck from the left.

The spacings of the groupings at different equivalent focal lengths are given below in Table XXVII.

TABLE XXVII______________________________________EFL______________________________________Spacing 51.44 mm 84.39 mm 133.96 mm 194.05 mmD1 30.45 mm 25.55 mm 15.16 mm 2.64 mmD2 3.75 mm 13.95 mm 26.33 mm 40.44 mmD3 1.01 mm 7.12 mm 13.68 mm 22.38 mmf/No. 2.91 3.40 3.75 4.15______________________________________ TABLE XXVIII__________________________________________________________________________ Table F.sub.I f.sub.II f.sub.IIIa f.sub.IIIb fG31 fG32 fG33 RatioRatio ##STR1## RatioTelephoto SGIIIbRatioTelephoto__________________________________________________________________________I 1.98 -0.71 1.98 1.83 0.98 1.28 -0.53 3.79 0.54 0.9 0.81IV 1.80 -0.62 1.96 1.66 0.97 1.02 -0.52 3.79 0.54 0.9 0.85VIII 1.86 -0.62 2.17 1.53 1.15 1.51 -0.75 3.79 0.65 0.87 0.92X 2.07 -0.66 2.30 2.10 1.61 1.70 -1.02 4.76 0.63 0.97 0.94XII 1.47 -0.49 1.63 1.65 1.22 2.13 -1.04 3.79 0.85 0.9 0.93V 1.90 -0.65 2.13 1.53 1.06 2.13 -0.86 3.79 0.81 0.9 0.9XIII 1.72 -0.61 1.85 1.69 1.12 3.22 -1.12 3.79 1.00 0.9 0.89XVI 1.89 -0.65 1.95 1.73 1.07 1.42 -0.62 3.79 0.58 0.9 0.85XXII 1.62 -0.51 1.76 1.60 1.33 2.03 -1.64 3.84 1.27 1.13 1.01XVIII 1.26 -0.46 1.11 1.11 0.86 1.92 -0.79 2.82 0.92 0.99 0.96XX 1.32 -0.55 3.02 0.99 0.96 1.24 -0.71 2.82 0.74 1.03 1.1XXIV 1.89 -0.56 1.72 1.59 0.86 1.68 -0.69 3.78 0.80 0.94 0.90XXV 1.88 -0.58 1.97 1.58 0.96 1.30 -0.69 3.77 0.73 0.99 0.93__________________________________________________________________________ TABLE XXIX______________________________________TABLE f.sub.I /FVD .vertline.f.sub.II /FVD.vertline. f.sub.IIIa /FVD f.sub.IIIb /FVD______________________________________I 0.58 0.21 0.58 0.54IV 0.53 0.18 0.57 0.49VIII 0.56 0.19 0.66 0.46X 0.45 0.14 0.50 0.45XII 0.43 0.14 0.48 0.48V 0.56 0.19 0.62 0.45XIII 0.50 0.18 0.54 0.50XVI 0.55 0.19 0.57 0.51XXII 0.37 0.12 0.41 0.37XVIII 0.45 0.16 0.40 0.40XX 0.45 0.19 1.04 0.34XXIV 0.53 0.16 0.48 0.45XXV 0.50 0.15 0.53 0.42______________________________________

Tables XXVIII and XXIV show the focal lengths of the various groupings, sub-groupings and groups as follows, as well as other parameters where

FVD is the front vertex distance related to unity EFL at the lower limit EFL of the lens, f.sub.I is the EFL of grouping GPI related to unity EFL at the lower limit EFL of the lens, f.sub.II is the EFL of grouping GPII related to unity EFL at the lower limit EFL of the lens, f.sub.IIIa is the EFL of sub-grouping SGIIIa related to unity EFL at the lower limit EFL of the lens, f.sub.IIIb is the EFL of sub-grouping SGIIIb related to unity EFL at the lower limit EFL of the lens, f.sub.G31 is the EFL of group G31 related to unity EFL at the lower limit EFL of the lens, f.sub.G32 is the EFL of group G32 related to unity EFL at the lower limit EFL of the lens, f.sub.G33 is the EFL of group G33 related to unity EFL at the lower lmit EFL of the lens, Telephoto Ratio is the ratio of the front vertex distance of the lens to the upper EFL of the lens, Zoom Ratio is the ratio of the higher EFL of the lens to the lower EFL, ##EQU2## is the absolute ratio of the power of group G31 to the power of group G33, Telephoto Ratio SG.sub.IIIb is the ratio of the front vertex distance of sub-grouping SG.sub.IIIb to its equivalent focal length.

It will be noted that in all cases ##EQU3## is substantially equal to or greater than 0.5. Otherwise stated, ##EQU4##

In all examples given, it has been found that the object side surface of G33 should be concave to introduce the proper aberration corrections. If the foregoing ratio decreases below the expressed value, the aberration contribution of the object side surface of group G33 may become unacceptably large.

Usually ##EQU5## will be less than 1.45.

All lens examples will focus to a magnification of 1:4 at the longest focal length by virtue of the structure of the overall lens and the front focusing grouping GP1. The smaller the value of f.sub.1 the shorter the travel of grouping GPI to focus at close objects. As shown by the examples, the following relation is preferred to achieve this result.

2.5f.sub.I >f.sub.IIIa .gtoreq.0.9 f.sub.I where f.sub.IIIa and f.sub.I are as previously defined.

Also for proper aberration correction, the EFL f.sub.IIIa of sub-grouping SGIIIa should be substantially the same as or greater than the EFL f.sub.IIIb of sub-grouping SGIIIb or

3.2f.sub.IIIb >f.sub.IIIa .gtoreq.f.sub.IIIb

This relationship further permits the lens to close focus to magnifications of 1:4 with relatively small axial movement of grouping GPI. For example, the lens of Table XII may focus this close with only 7.05 mm of axial extension.

With reference to Table XXIX the following relations are obtained:

0.3.ltoreq.f.sub.I/FVD .ltoreq.0.6 0.10.ltoreq..vertline.f.sub.II/FVD .vertline.23 0.25 0.3.ltoreq.f.sub.IIIa/FVD .ltoreq.1.2 0.3.ltoreq.f.sub.IIIb/FVD .ltoreq.0.6 where f.sub.I, f.sub.II, f.sub.IIIa, f.sub.IIIb, and FVD are as previously defined.

As shown by the various examples, various lens forms may be made within the scope of the invention. Accordingly, the appended claims are intended to cover all modifications of the disclosed embodiments as well as other embodiments thereof which do not depart from the spirit and scope of the invention.

Claims

1. A zoom lens comprising from the object side a first positive grouping movable axially for focusing, a second negative grouping, and a third positive grouping, said second and third groupings being movable simultaneously axially of said lens but in the opposite direction for varying the equivalent focal length of said lens, said third grouping comprising a front and rear sub-groupings of positive optical power, said rear sub-grouping comprises three groups which from the object end are of positive, positive and negative optical powers, successively.

2. The lens of claim 1 where said sub-groupings move at different rates as the equivalent focal length of said lens is varied.

3. The lens of claim 1 where

0.75 <TR<1.4

where TR is the telephoto ratio of the rear sub-grouping.

4. The lens of claim 1 where the optical power of said first group of said sub-grouping has an absolute ratio to the optical power of said third group of said sub-grouping of 0.5 or greater.

5. The lens of claim 4 where said ratio has an upper limit of 1.45.

6. The lens of claim 4 where the object side surface of said third group is concave.

7. The lens of claim 1 where said third grouping has a first sub-grouping on the object side with equivalent focal length f.sub.IIIa and ##EQU6## where f.sub.I is the equivalent focal length of the first grouping.

8. The lens of claim 6 where ##EQU7##

9. The lens of claim 1 where

3.2 f.sub.IIIb >f.sub.IIIa .gtoreq.f.sub.IIIb

where f.sub.IIIa is the equivalent focal length of the first sub-grouping and f.sub.IIIb is the equivalent focal length of the second sub-grouping.

10. The lens of claim 7 where said first grouping comprises an object side doublet which is a negative meniscus and a bi-convex element, followed by a positive meniscus.

11. The lens of claim 7 where the front grouping is a doublet comprising a bi-concave element and a bi-convex element, followed by a bi-convex element.

12. The lens of claim 11 where the doublet is of negative optical power.

13. The lens of claim 1 where said third grouping has a first object side sub-grouping of positive power and said sub-grouping comprises from the object side a positive element and a doublet comprising a bi-concave element and a bi-convex element.

14. The lens of claim 1 where the second grouping has a first object side group comprising a negative element, and a doublet concave to the object side and convex to the image side.

15. The lens of claim 1 where the second grouping is, from the object side, a doublet comprising a bi-convex element and a bi-concave element followed by a negative element having a concave object side surface.

16. The lens of claim 1 wherein the second grouping comprises from the object side a negative optical power element, a positive meniscus element concave to the object side, and a doublet concave to the object side and convex to the image side.

17. The lens of claim 1 wherein said first sub-grouping comprises a doublet having a bi-convex element and a negative element.

18. The lens of claim 1 wherein said first sub-grouping is a doublet in the form of a negative meniscus and a bi-convex element, from the object side.

19. The lens of claim 1 wherein said first sub-grouping comprises a positive single element and a weak optical power doublet which includes a bi-convex element.

20. A zoom lens comprising from the object side a first positive grouping movable axially for focusing, a second negative grouping, a third positive grouping, said second and third groupings being movable axially simultaneously but in the opposite direction for varying the equivalent focal length of said lens, said third grouping comprising front and rear sub-groupings of positive optical power, said rear sub-grouping having a telephoto ratio of 0.75 to 1.4 and the ratio of the equivalent focal length of the first sub-grouping to that of the second sub-grouping of from 1.0 to 3.2.

21. The lens of claim 20 where said sub-groupings move at different rates as the equivalent focal length of the lens is changed.

22. A zoom lens comprising from the object side a first positive grouping movable axially for focusing, a second negative group, and a third positive grouping, said second and third groupings being movable simultaneously axially of said lens, but in opposite directions for varying the equivalent focal length of said lens, said third grouping comprising front and rear sub-groupings of positive optical power, said rear sub-grouping comprising from the object end a first positive group, a second positive group, and a third negative group, the absolute value of the ratio of the optical power of the first positive group to the third negative group being 0.5 or greater, said third negative group having a concave object side surface.

23. A lens according to claim 1 having semi-field angles of 22.8.degree. to 6.3.degree. as scaled to a 24.times.36 mm image frame defined substantially as follows:

______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = -331.909L1 2.000 1.847 23.8 R2 = 77.893L2 8.325 1.531 50.9 R3 = -105.577 0.200 R4 = 75.550L3 5.264 1.741 35.1 R5 = -738.126 1.000 R6 = -273.757L4 4.990 1.847 23.8 R7 = -39.174L5 2.000 1.697 55.5 R8 = 74.538 4.086 R9 = -53.121L6 1.500 1.697 55.5 R10 = 148.879 49.510 R11 = 46.961L7 4.902 1.608 40.0 R12 = -929.669 0.200 R13 = 726.860L8 6.485 1.587 51.7 R14 = -31.445L9 1.500 1.847 23.8 R15 = -260.591 10.825 R16 = 23.960 L10 8.148 1.517 69.7 R17 = 249.885 11.397 R18 = 64.858 L11 1.500 1.804 46.5 R19 = 16.770 0.467 R20 = 18.004 L12 6.440 1.648 33.8 R21 = -46.653 2.692 R22 = -18.862 L13 1.500 1.834 37.3 R23 = -106.740______________________________________ Where L1-L13 are lens elements from the object end to the image end successively. R1-R23 are the radii of the element surfaces successively from the object to image end. N.sub.d is the index of refraction of the elements, and V.sub.d is the dispersion of the elements as measured by th Abbe number.

24. A lens according to claim 1 having semi-field angles of 22.8.degree. to 6.3.degree. as scaled to a 24.times.36 mm image frame defined substantially as follows:

______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 91.606L1 6.157 1.517 69.7 R2 = -204.977 0.200 R3 = 99.209L2 6.256 1.487 70.4 R4 = -121.897L3 2.000 1.847 23.8 R5 = -1311.231 1.000 R6 = -207.668L4 1.500 1.713 53.9 R7 = 39.369 4.571 R8 = -48.686L5 2.000 1.697 55.5 R9 = 39.043L6 4.988 1.847 23.8 R10 = -564.889 46.831 R11 = 54.481L7 5.338 1.607 56.7 R12 = -374.746 0.200 R13 = 77.405L8 7.895 1.581 40.9 R14 = -36.501L9 1.500 1.847 23.8 R15 = 194.707 9.109 R16 = 26.911 L10 8.076 1.525 60.0 R17 = -1041.865 9.346 R18 = 52.178 L11 1.838 1.559 64.4 R19 = 21.897 3.425 R20 = 28.087 L12 5.298 1.627 34.6 R21 = -62.138 2.562 R22 = -23.600 L13 1.500 1.834 37.3 R23 = 28.021 0.445 R24 = 28.914 L14 4.385 1.619 35.4 R25 = -118.264______________________________________ Where L1-L14 are lens elements from the object end to the image end successively. R1-R25 are the radii of the element surfaces successively from the object to image end. N.sub.d is the index of refraction of the elements, and V.sub.d is the dispersion of the elements as measured by th Abbe number.

25. A lens according to claim 1 having semi-field angles of 22.8.degree. to 6.3.degree. as scaled to a 24.times.36 mm image frame defined substantially as follows:

______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 311.481L1 2.000 1.847 23.8 R2 = 68.476L2 9.718 1.589 62.6 R3 = -108.672 0.200 R4 = 50.060L3 4.222 1.690 31.0 R5 = 84.784 2.822 R6 = 508.164L4 5.563 1.847 23.8 R7 = -47.257L5 2.000 1.696 55.1 R8 = 41.931 5.239 R9 = -38.143L6 1.500 1.711 53.9 R10 = Infinity 47.717 R11 = 59.518L7 7.648 1.571 51.1 R12 = -30.945L8 1.500 1.831 24.2 R13 = -106.827 4.906 R14 = 22.295L9 7.351 1.487 70.4 R15 = 85.618 18.021 R16 = 54.725 L10 5.731 1.631 34.2 R17 = - 16.627 L11 1.500 1.806 40.7 R18 = -68.855 2.363 R19 = -19.620 L12 1.500 1.806 40.7 R20 = -53.856______________________________________ Where L1-L12 are lens elements from the object end to the image end successively. R1-R20 are the radii of the element surfaces successively from the object to image end. N.sub.d is the index of refraction of the elements, and V.sub.d is the dispersion of the elements as measured by th Abbe number.

26. A lens according to claim 1 having semi-field angles of 27.8.degree. to 6.3.degree. as scaled to a 24.times.36 mm image frame defined substantially as follows:

______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 87.088L1 6.073 1.487 70.4 R2 = -357.220 0.200 R3 = 81.894L2 6.904 1.517 69.7 R4 = -113.558L3 2.000 1.805 25.5 R5 = -741.212 1.000 R6 = -145.203L4 2.000 1.850 32.2 R7 = 29.227 5.027 R8 = -40.720L5 3.218 1.617 36.6 R9 = -28.743 0.329 R10 = -34.696L6 2.000 1.620 60.3 R11 = 30.644L7 4.602 1.847 23.8 R12 = -836.811 47.970 R13 = 244.236L8 3.347 1.847 23.8 R14 = -159.720 0.200 R15 = 37.449L9 7.464 1.487 70.4 R16 = -59.792 1.500 1.847 23.8 L10 R17 = 128.574 14.245 R18 = 34.377 L11 7.312 1.694 53.3 R19 = 125.375 12.722 R20 = 40.777 L12 1.500 1.834 37.3 R21 = 17.194 L13 8.377 1.529 51.6 R22 = -45.367 4.500 R23 = -23.943 L14 1.500 1.850 32.2 R24 = 50.260 0.724 R25 = 56.060 L15 3.971 1.847 23.8 R26 = -75.126______________________________________ Where L1-L15 are lens elements from the object end to the image end successively. R1-R26 are the radii of the element surfaces successively from the object to image end. N.sub.d is the index of refraction of the elements, and V.sub.d is the dispersion of the elements as measured by th Abbe number.

27. A lens according to claim 1 having semi-field angles of 22.8.degree. to 6.3.degree. as scaled to a 24.times.36 mm image frame defined substantially as follows:

______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 51.685L1 2.000 1.728 28.7 R2 = 35.419L2 11.322 1.487 70.4 R3 = -300.792 0.200 R4 = 70.392L3 4.236 1.487 70.4 R5 = 260.451 2.174 R6 = -218.893L4 1.500 1.773 49.6 R7 = 33.369 5.032 R8 = -50.332L5 1.500 1.697 55.5 R9 = 29.315L6 5.544 1.847 23.8 R10 = 372.944 39.191 R11 = 278.949L7 3.349 1.785 25.7 R12 = -112.134 0.200 R13 = 37.648L8 8.126 1.487 70.4 R14 = -46.741L9 1.500 1.728 28.7 R15 = 130.107 12.937 R16 = 30.554 L10 5.344 1.589 61.3 R17 = 161.993 9.765 R18 = 53.104 L11 1.500 1.805 25.5 R19 = 26.732 0.998 R20 = 35.956 L12 4.621 1.603 60.7 R21 = -86.528 10.000 R22 = -20.688 L13 1.200 1.773 49.6 R23 = 36.746 L14 6.262 1.673 32.2 R24 = -36.746______________________________________ Where L1-L14 are lens elements from the object end to the image end successively. R1-R24 are the radii of the element surfaces successively from the object to image end. N.sub.d is the index of refraction of the elements, and V.sub.d is the dispersion of the elements as measured by th Abbe number.

28. A lens according to claim 1 having semi-field angles of 22.8.degree. to 6.3.degree. as scaled to a 24.times.36 mm image frame defined substantially as follows:

______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 101.687L1 7.471 1.487 70.4 R2 = -198.419 0.200 R3 = 95.447L2 7.353 1.487 70.4 R4 = -139.520L3 2.000 1.805 25.5 R5 = -5325.160 2.883 R6 = -190.880L4 1.500 1.773 49.7 R7 = 48.001 5.742 R8 = -58.215L5 2.000 1.697 55.5 R9 = 42.255L6 4.992 1.847 23.8 R10 = 2180.742 50.035 R11 = 154.385L7 3.104 1.847 23.8 R12 = -536.964 0.200 R13 = 34.221L8 8.851 1.487 70.4 R14 = -42.312L9 1.500 1.805 25.5 R15 = 124.660 5.006 R16 = 27.114 L10 5.691 1.581 40.9 R17 = 167.817 6.077 R18 = 35.204 L11 1.500 1.847 23.8 R19 = 22.920 1.620 R20 = 36.325 L12 6.578 1.541 47.2 R21 = -83.500 8.928 R22 = -18.143 L13 1.500 1.834 37.3 R23 = 114.343 0.617 R24 = 278.786 L14 3.152 1.847 23.8 R25 = -35.211______________________________________ Where L1-L14 are lens elements from the object end to the image end successively. R1-R25 are the radii of the element surfaces successively from the object to image end. N.sub.d is the index of refraction of the elements, and V.sub.d is the dispersion of the elements as measured by th Abbe number.

29. A lens according to claim 1 having semi-field angles of 22.8.degree. to 6.3.degree. as scaled to a 24.times.36 mm image frame defined substantially as follows:

______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 100.000L1 2.000 1.847 23.8 R2 = 61.777L2 8.540 1.487 70.4 R3 = -139.015 0.200 R4 = 57.007L3 4.333 1.487 70.4 R5 = 141.831 1.774 R6 = -219.606L4 1.500 1.773 49.7 R7 = 42.712 4.608 R8 = -50.056L5 2.000 1.697 55.5 R9 = 39.784L6 4.992 1.847 23.8 R10 = -1453.300 47.246 R11 = 93.289L7 3.836 1.805 25.5 R12 = -218.835 0.200 R13 = 37.170L8 7.645 1.487 70.4 R15 = -60.263L9 1.500 1.847 23.8 R15 = 74.160 8.989 R16 = 28.233 L10 5.691 1.583 45.7 R17 = 161.805 8.196 R18 = 41.946 L11 1.500 1.847 23.8 R19 = 23.983 1.133 R20 = 33.166 L12 4.571 1.532 48.8 R21 = -115.744 11.000 R22 = -18.977 L13 1.500 1.834 37.3 R23 = 73.633 0.505 R24 = 94.636 L14 5.041 1.785 25.7 R25 = -31.880______________________________________ Where L1-L14 are lens elements from the object end to the image end successively. R1-R25 are the radii of the element surfaces successively from the object to image end. N.sub.d is the index of refraction of the elements, and V.sub.d is the dispersion of the elements as measured by th Abbe number.

30. A lens according to claim 1 having semi-field angles of 22.8.degree. to 6.3.degree. as scaled to a 24.times.36 mm image frame defined substantially as follows:

______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 94.324L1 6.157 1.517 69.7 R2 = -225.278 0.200 R3 = 107.461L2 6.256 1.487 70.4 R5 = -125.129L3 2.000 1.847 23.8 R5 = -998.950 1.000 R6 = -175.603L4 1.500 1.713 53.9 R7 = 42.006 4.571 R8 = -55.596L5 2.000 1.697 55.5 R9 = 38.480L6 4.988 1.847 23.8 R10 = -2603.400 46.933 R11 = 57.230L7 5.338 1.607 56.7 R12 = -355.668 0.200 R13 = 97.881L8 7.895 1.581 40.9 R15 = -38.031L9 1.500 1.847 23.8 R15 = 383.703 10.275 R16 = 26.072 L10 8.076 1.517 69.7 R17 = 264.855 11.774 R18 = 57.188 L11 2.581 1.487 70.4 R19 = 157.667 0.588 R20 = 132.141 L12 1.500 1.786 43.9 R21 = 17.553 0.559 R22 = 18.852 L13 6.418 1.648 33.8 R23 = -54.308 2.694 R24 = -20.096 L14 1.500 1.800 42.3 R25 = -96.886______________________________________ Where L1-L14 are lens elements from the object end to the image end successively. R1-R25 are the radii of the element surfaces successively from the object to image end. N.sub.d is the index of refraction of the elements, and V.sub.d is the dispersion of the elements as measured by th Abbe number.

31. A lens according to claim 1 having semi-field angles of 22.8.degree. to 8.2.degree. as scaled to a 24.times.36 mm image frame defined substantially as follows:

______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 43.818L1 2.00 1.805 25.5 R2 = 30.325L2 9.03 1.487 70.4 R3 = 660.800 0.20 R4 = 57.757L3 4.58 1.487 70.4 R5 = -2198.63 2.00 R6 = -172.476L4 1.50 1.786 43.9 R7 = 23.666 4.44 R8 = -37.599L5 1.50 1.487 70.4 R9 = 27.572L6 4.19 1.847 23.8 R10 = 215.640 .88 R11 = 58.063L7 2.76 1.785 25.7 R12 = 451.184 .20 R13 = 40.879L8 6.43 1.487 70.4 R14 = -30.890L9 1.50 1.805 25.3 R15 = 179.032 4.64 R16 = 26.196 L10 5.72 1.487 70.4 R17 = - 122.438 11.13 R18 = 54.654 L11 1.50 1.834 37.3 R19 = 17.104 0.37 R20 = 17.908 L12 5.14 1.626 35.5 R21 = -77.945 5.29 R22 = -17.046 L13 1.50 1.743 49.2 R23 = 40.228______________________________________ Where L1-L13 are lens elements from the object end to the image end successively. R1-R23 are the radii of the element surfaces successively from the object to image end. N.sub.d is the index of refraction of the elements, and V.sub.d is the dispersion of the elements as measured by th Abbe number.

32. A lens according to claim 1 having semi-field angles of 29.6.degree. to 8.4.degree. as scaled to a 24.times.36 mm image frame defined substantially as follows:

______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 84.075L1 2.000 1.824 32.4 R2 = 35.070L2 10.644 1.487 70.4 R3 = Infinity 0.200 R4 = 42.216L3 7.293 1.640 60.2 R5 = -551.202 1.417 R6 = 3577.318L4 1.500 1.773 49.6 R7 = 22.455 4.403 R8 = -36.651L5 1.500 1.697 55.5 R9 = 23.130L6 4.494 1.847 23.8 R10 = 305.162 27.789 R11 = 182.035L7 3.349 1.805 25.5 R12 = -83.526 .200 R13 = 31.013L8 6.560 1.487 70.4 R14 = -39.407L9 1.500 1.789 27.5 R15 = 83.438 19.239 R16 = 24.898 L10 5.344 1.592 60.5 R17 = 131.219 4.888 R18 = 51.764 L11 1.500 1.805 25.5 R19 = 22.511 1.477 R20 = 32.129 L12 6.196 1.599 62.1 R21 = -44.403 6.00 R22 = -18.935 L13 1.200 1.764 47.9 R23 = 31.004 L14 7.807 1.692 36.9 R24 = -31.715______________________________________ Where L1-L14 are lens elements from the object end to the image end successively. R1-R24 are the radii of the element surfaces successively from the object to image end. N.sub.d is the index of refraction of the elements, and V.sub.d is the dispersion of the elements as measured by th Abbe number.

33. A lens according to claim 1 having semi-field angles of 22.8.degree. to 8.5.degree. as scaled to a 24.times.36 mm image frame defined substantially as follows:

______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 154.274L1 2.000 1.805 25.5 R2 = 60.625L2 7.482 1.603 60.7 R3 = -166.752 0.200 R4 = 49.425L3 4.711 1.487 70.4 R5 = 976.009 2.000 R6 = -111.965L4 1.500 1.834 37.3 R7 = 29.937 4.683 R8 = -40.282L5 1.500 1.487 70.4 R9 = 34.267L6 4.190 1.847 23.8 R10 = -661.409 37.179 R11 = 58.780L7 3.370 1.785 25.7 R12 = 588.325 0.200 R13 = 40.593L8 6.062 1.518 59.0 R14 = -38.790L9 1.500 1.805 25.5 R15 = 60.207 0.200 R16 = 29.884 L10 4.661 1.603 60.7 R17 = Infinity 15.024 R18 = 47.488 L11 1.500 1.834 37.3 R19 = 17.934 0.309 R20 = 18.509 L12 5.462 1.632 34.8 R21 = -62.404 6.267 R22 = -19.946 L13 1.500 1.834 37.3 R23 = -58.480______________________________________ Where L1-L13 are lens elements from the object end to the image end successively. R1-R23 are the radii of the element surfaces successively from the object to image end. N.sub.d is the index of refraction of the elements, and V.sub.d is the dispersion of the elements as measured by th Abbe number.

34. A lens according to claim 1 having semi-field angles of 22.7.degree. to 6.4.degree. as scaled to a 24.times.36 mm image frame defined substantially as follows:

______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 61.614L1 3.000 1.805 25.5 R2 = 43.179L2 11.800 1.487 70.4 R3 = -262.146 0.200 R4 = 57.758L3 3.500 1.487 70.4 R5 = 84.442 32.117 R6 = -1317.271L4 1.500 1.804 46.5 R7 = 36.278 5.516 R8 = -44.483L5 1.500 1.773 49.6 R9 = 34.734L6 5.000 1.847 23.8 R10 = -219.127 3.250 R11 = 234.035L7 3.350 1.699 30.1 R12 = -89.453 0.200 R13 = 43.887L8 6.600 1.487 70.4 R14 = -58.165L9 1.500 1.785 26.1 R15 = 117.280 1.000 R16 = 43.796 L10 4.200 1.487 70.4 R17 = 1423.188 0.200 R18 = 25.838 L11 5.600 1.487 70.4 R19 = 64.901 4.495 R20 = 27.729 L12 2.000 1.805 25.5 R21 = 18.696 8.570 R22 = 72.878 L13 4.900 1.487 70.4 R23 = -31.396 2.125 R24 = -23.175 L14 1.200 1.804 46.5 R25 = 43.273 0.571 R26 = 46.400 L15 3.900 1.805 25.5 R27 = -124.368______________________________________ Where L1-L15 are lens elements from the object end to the image end successively. R1-R27 are the radii of the element surfaces successively from the object to image end. N.sub.d is the index of refraction of the elements, and V.sub.d is the dispersion of the elements as measured by th Abbe number.

35. A lens according to claim 1 having semi-field angles of 22.8.degree. to 6.4.degree. as scaled to a 24.times.36 mm image frame defined substantially as follows:

______________________________________ Axial Distance Index of AbbeEle- Radius of Between Surfaces Refraction No.ment Curvature (mm) (mm) N.sub.d V.sub.d______________________________________ R1 = 76.881L1 3.000 1.805 25.5 R2 = 48.966L2 12.250 1.487 70.4 R3 = -164.561 0.210 R4 = 45.744L3 3.500 1.517 64.2 R5 = 64.414 30.449 R6 = 230.226L4 1.500 1.713 53.9 R7 = 32.025 5.200 R8 = -39.590L5 1.500 1.773 49.6 R9 = 36.704L6 5.000 1.847 23.8 R10 = -235.177 3.750 R11 = -166.537L7 2.800 1.785 26.1 R12 = -72.127 0.200 R13 = 46.928L8 7.300 1.487 70.4 R14 = -50.494L9 1.500 1.785 26.1 R15 = 526.365 1.010 R16 = 64.334 L10 4.200 1.487 70.4 R17 = -211.416 0.200 R18 = 29.665 L11 5.450 1.487 70.4 R19 = 76.428 9.370 R20 = 26.516 L12 2.000 1.847 23.8 R21 = 19.733 6.680 R22 = 64.036 L13 5.200 1.487 70.4 R23 = -30.409 1.280 R24 = -25.289 L14 1.200 1.804 46.5 R25 = 52.130 3.230 R26 = 62.262 L15 4.280 1.805 25.5 R27 = -189.602______________________________________ Where L1-L15 are lens elements from the object end to the image end successively. R1-R27 are the radii of the element surfaces successively from the object to image end. N.sub.d is the index of refraction of the elements, and V.sub.d is the dispersion of the elements as measured by th Abbe number.

36. The lens of claim 1 wherein:

0.3.ltoreq.fI/FVD.ltoreq.0.6

0.10.ltoreq..vertline.fII/FVD.vertline..ltoreq.0.25

0.3.ltoreq.fIIIa/FVD.ltoreq.1.2

0.3.ltoreq.fIIIb/FVD.ltoreq.0.6

Where fI is the effective focal length of said first grouping, fII is the equivalent focal length of said second grouping, fIIIa is the equivalent focal length of said front sub-grouping, fIIIb is the equivalent focal length of said rear sub-grouping, and FVD is the front vertex distance of the lens.

37. The lens of claim 1 wherein the telephoto ratio of said rear sub-grouping is less than 1.