A main lens unit having a fixed focal length and consisting of a positive lens member is preceded by an afocal forward lens unit having a variable magnification and consisting of a positive forward lens member, a negative intermediate lens member which is axially movable to change the magnification, and a positive rear lens member. The intermediate lens member is arranged to direct divergent bundles of rays to said rear lens member. The rear lens member is arranged to convert said divergent bundles or rays into bundles of rays which are substantially parallel to the optical axis of the lens and to direct them to said main lens unit. The forward lens member is axially movable to control the position of the image plane. The lens is designed to meet the condition
fmin -f11 < 6y
where fmin is the smallest focal length of the lens, f11 the focal length of the intermediate lens member, and 2y the image field diagonal.
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1. A zoom lens, which comprises
a main lens unit having a fixed focal length and consisting of a positive lens member, and an afocal forward lens unit preceding said main lens unit and having a variable magnification, said forward lens unit consisting of a positive forward lens member, a negative intermediate lens member which is axially movable to change the magnification, and a positive rear lens member, the positive forward lens member of the afocal part consists of a negative meniscue meniscus lens element convex towards the front followed by two biconvex lens elements, said negative intermediate lens member consists of a negative meniscue meniscus convex toward the front followed by a negative doublet composed of a biconcave lens cemented to a positive lens element, said positive rear lens member consists of a biconvex lens element, said intermediate lens member being arranged to direct divergent bundles of rays to said rear lens member, said rear lens member being arranged to convert said divergent bundles of rays into bundles of rays which are substantially parallel to the optical axis of the lens and to direct them to said rear lens member, said forward lens member being axially movable to control the position of the image plane, and said lens being designed to meet the condition
fmin -f11 <6y where fmin is the smallest focal length of the lens, f11 the focal length of said intermediate lens member, and 2y the image field diagonal. 3. A zoom lens which comprises
a main lens unit having a fixed focal length and consisting of a positive lens member, and an afocal forward lens unit preceding said main lens unit and having a variable magnification, said forward lens unit consisting of a positive forward lens member, a negative intermediate lens member which is axially movable to change the magnification, and a positive rear lens member, said intermediate lens member being arranged to direct divergent bundles of rays to said rear lens member, said rear lens member being arranged to convert said divergent bundles of rays into bundles of rays which are substantially parallel to the optical axis of the lens and to direct them to said rear lens member, said forward lens member being axially movable to control the position of the image plane, said lens being designed to meet the condition
fmin -f11 < 6y where fmin is the smallest focal length of the lens, f11 the focal length of said intermediate lens member, and 2y the image field diagonal, said forward lens member consists of three lens elements, said intermediate lens member consists of three lens elements, said zoom lens having the following data:
where r1 to r21 are in millimeters the radii of curvature of boundary surfaces of lens elements, d1 to d20 are in millimeters the distances between adjacent vertices of adjacent boundary surfaces of lens elements, nd1 to nd11 are the indices of refraction and vd1 to vd11 are the Abbe numbers of the lens elements, all in a succession from the forward end to the rear end of the lens, s' is the back focal length and 2y the image diagonal, and which data unless otherwise stated are applicable to a setting for a mean focal length fM, which is the geometric mean of the shortest focal length fmin and the longest focal length fmax of the lens. 4. A zoom lens, which comprises
a main lens unit having a fixed focal length and consisting of a positive lens member, and an afocal forward lens unit preceding said main lens unit and having a variable magnification, said forward lens unit consisting of a positive forward lens member, a negative intermediate lens member which is axially movable to change the magnification, and a positive rear lens member, said intermediate lens member being arranged to direct divergent bundles of rays to said rear lens member, said rear lens member being arranged to convert said divergent bundles of rays into bundles of rays which are substantially parallel to the optical axis of the lens and to direct them to said rear lens member, said forward lens member being axially movable to control the position of the image plane, said lens being designed to meet the condition
fmin -f 11 < 6y where fmin is the smallest focal length of the lens, f11 the focal length of said intermediate lens member, and 2y the image field diagonal, said forward lens member consists of three lens elements, said intermediate lens member consists of three lens elements, said zoom lens having the following data:
where r1 to r21 are in millimeters the radii of curvature of boundary surfaces of lens elements, d1 to d20 are in millimeters the distances between adjacent vertices of adjacent boundary surfaces of lens elements, nd1 to nd11 are the indices of refraction and vd1 to vd11 are the Abbe numbers of the lens elements, all in a succession from the forward end to the rear end of the lens, s' is the back focal length and 2y the image diagonal, and which data unless otherwise stated are applicable to a setting for a mean focal length fM, which is the geometric mean of the shortest focal length fmin and the longest focal length fmax of the lens. 2. A zoom lens as set forth in
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This invention relates to a zoom lens, particularly a camera lens, preferably a lens for Super-8 film, which lens comprises an afocal forward lens unit having a variable magnification and a main lens unit having a fixed focal length. The forward lens unit comprises a positive forward lens member, which is succeeded by a negative intermediate lens member and a positive rear lens member, and the main lens unit consists of a positive lens member. For a change of the magnification, the negative intermediate lens member is slidable along the optical axis and the forward lens member performs the compensating movement required to maintain the image in the same position. The divergent bundles of rays behind the second lens member leave the positive third lens member in a direction which is substantially parallel to the axis and pass through the diaphragm area to the main lens unit.
In conventional lenses of this kind it has been difficult to reduce the mechanical dimensions, namely, the overall length of the lens and the diameter of the forward lens member unless the performance was adversely affected. The performance of a zoom lens may be defined by a performance number Z, which can be calculated by the formula
Z= 2 yD/fmin
Where 2y is the image field diagonal, D the zoom ratio and fmin the smallest focal length of the lens. As is known, the zoom ratio defines the ratio of the largest to the smallest focal length. If the zoom ratio and the smallest focal length are predetermined, the diameter of the forward lens member will depend in the lenses of the type in question, on the overall length of the lens and that overall length will highly depend on the negative focal length of the intermediate lens member. To some extent, the overall length may be influenced by the ratio of the focal length of the forward lens member to the focal length of the main lens unit. Although this ratio may be freely chosen, a relatively long focal length of the main lens unit is preferably associated with a relatively short focal length of the forward lens member. As a result, there may be a negative distance between infinitesimally thin lens elements which replace the forward and intermediate lens members. Such of embodimentsin millimeters the radii of curvature of boundary surfaces of lens elements, d1 to d20 are in millimeters the distances between adjacent vertices of adjacent boundary surfaces of lens elements, nd1 to nd11 are the indices of refraction and vd1 to vd11 are the Abbe numbers of the lens elements, all in a succession from the forward end to the rear end of the lens. Except where otherwise stated, these data are applicable to a setting for a mean focal length fv, which is the geometric mean of the shortest focal length fmin and the longest focal length fmax of the lens s' is the back focal length and 2y the image field diagonal.
| TABLE I |
| ______________________________________ |
| r1 + 5.308 |
| d1 = 0.08 |
| nd 1 = 1.805 |
| d 1 = 25.4 |
| r2 + 1.750 |
| d2 = 0.07 |
| r3 + 2.104 |
| d3 = 0.28 |
| nd 2 = 1.603 |
| d 2 = 60.6 |
| r4 - 25.054 |
| d4 = 0.01 |
| r5 + 1.660 |
| d5 = 0.28 |
| nd 3 = 1.658 |
| d 3 = 50.9 |
| r6 - 30.293 |
| fmin fM fmax |
| r7 + 7.378 |
| d7 = 0.06 |
| nd 4 = 1.658 |
| d 4 = 50.9 |
| r8 + 0.648 |
| d8 = 0.14 |
| r9 - 1.310 |
| d9 = 0.06 |
| nd 5 = 1.670 |
| d 5 = 47.1 |
| r10 + 0.800 |
| d10 = 0.14 |
| nd 6 = 1.805 |
| d 6 = 25.4 |
| r11 + 23.022 |
| fmin fM fmax |
| r12 + 1.767 |
| d12 = 0.10 |
| nd 7 = 1.689 |
| d 7 = 49.5 |
| r13 - 17.389 |
| d13 = 0.50 |
| r14 + 0.544 |
| d14 = 0.18 |
| nd 8 = 1.713 |
| d 8 = 53.8 |
| r15 - 5.043 |
| d15 = 0.11 |
| r16 - 0.985 |
| d16 = 0.20 |
| nd 9 = 1.785 |
| d 9 = 26.1 |
| r17 + 0.474 |
| d17 = 0.20 |
| r18 - 2.559 |
| d18 = 0.12 |
| nd 10 = 1.641 |
| d 10 = 60.1 |
| r19 - 0.744 |
| d19 = 0.01 |
| r20 + 0.690 |
| d20 = 0.17 |
| nd 11 = 1.641 |
| d 11 = 60.1 |
| r21 - 4.020 |
| s' = 0.59 |
| fmin = 0.575 |
| fM = 1.018 |
| fmax = 1.800 |
| 2y = 0.440 |
| ______________________________________ |
It is apparent from FIG. 2 that the glasses which may be used to make the lens elements L1 to L6 of the first and second lens members need not meet high requirements as regards the index of refraction or the Abbe number. The hatched fields represent the values of nd and vd of the glasses used for lens elements L1 to L6. It is apparent that none of these glasses has an Abbe number which is less than 25 or higher than 61. The following values are apparent for Table II
Glasses for which 25 < vd > 28: 1.75 ≦ nd ≦ 1.810
Glasses for which 28 < vd < 31: 1.717 ≦ n d ≦ 1.75
Glasses for which 31 < vd < 48: 1.624 ≦ nd ≦ 1.717
Glasses for which 48 < vd < 53: 1.610 ≦ n d ≦ 1.660
Glasses for which 53 < vd < 61: 1.600 ≦ nd ≦ 1.630
The lens defined in the subsequent Table II has a zoom ratio of about 2.6 and its smallest focal length is about 1.4 times the image field diagonal. In this case too, the free diameter of the foremost lens element in millimeters does not exceed 12 times the performance number Z. The lens is also excellently corrected throughout the focal length range; the image has a high contrast and a high resolution in any focal length setting and is flat as far as to the edge and free of color errors and distortion. To enable the use of lens member IV of Example I as a main lens unit, the zoom supplement has been designed to have substantially the same residual errors as the supplement of Example I.
| TABLE II |
| ______________________________________ |
| r1 + 4.661 |
| d1 = 0.07 |
| nd 1 = 1.805 |
| d 1 = 25.4 |
| r2 + 1.423 |
| d2 = 0.05 |
| r3 + 1.567 |
| d3 = 0.25 |
| nd 2 = 1.604 |
| d 2 = 53.6 |
| r4 - 25.437 |
| d4 = 0.01 |
| r5 + 1.427 |
| d5 = 0.25 |
| nd 3 = 1.624 |
| d 3 = 47.0 |
| r6 - 25.437 |
| fmin fM fmax |
| r7 + 64.139 |
| d7 = 0.06 |
| nd 4 = 1.717 |
| d 4 = 48.0 |
| r8 + 0.646 |
| d8 = 0.14 |
| r9 - 1.254 |
| d9 = 0.05 |
| nd 5 = 1.622 |
| d 5 = 53.2 |
| r10 + 0.710 |
| d10 = 0.14 |
| nd 6 = 1.755 |
| d 6 = 27.6 |
| r11 flat |
| fmin fM fmax |
| r12 + 1.967 |
| d12 = 0.10 |
| nd 7 = 1.623 |
| d 7 = 58.1 |
| r13 - 4.076 |
| d13 = 0.50 |
| r14 + 0.544 |
| d14 = 0.18 |
| nd 8 = 1.713 |
| d 8 = 53.8 |
| r15 - 5.043 |
| d15 = 0.11 |
| r16 - 0.985 |
| d16 = 0.20 |
| nd 9 = 1.785 |
| d 9 = 26.1 |
| r 17 + 0.474 |
| d17 = 0.20 |
| r18 - 2.559 |
| d18 = 0.12 |
| nd 10 = 1.641 |
| d 10 = 60.1 |
| r19 - 0.744 |
| d19 = 0.01 |
| r20 + 0.690 |
| d20 = 0.17 |
| nd 11 = 1.641 |
| d 11 = 60.1 |
| r21 - 4.020 |
| fmin = 0.606 |
| fM = 0.979 |
| fmax = 1.581 |
| 2y = 0.440 |
| ______________________________________ |
The data in Tables I and II are subject to the following tolerances: The curvature of individual surfaces may vary to an extent corresponding to a variation of the focusing power of the respective lens member by ±10 percent; the thicknesses may vary up to ±10 percent of the respective lens member; the refractive indices may vary by up to ±0.03 and the Abbe numbers by up to ± 5.
Muszumanski, Trude, Gela, Helmut
| Patent | Priority | Assignee | Title |
| 4297007, | Apr 24 1979 | Polaroid Corporation | Optical apparatus and method for changing a zoom camera to a fixed focus camera |
| Patent | Priority | Assignee | Title |
| 3074317, | |||
| 3506337, | |||
| 3580662, |
| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Dec 18 1975 | Karl, Vockenhuber | (assignment on the face of the patent) | / | |||
| Dec 18 1975 | Raimund, Hauser | (assignment on the face of the patent) | / |
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