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Патент USA US3059546

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350-427
SEARCH ROOM
SR
0R
V
3,059,536
Oct. 23, 1962
3,059,536
A. COX ETAI
ZOOM LENS SYSTEM
Filed May 26. 1961
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3,059,536
Fr‘
United States Patent 0 ice
Patented Oct. 23, 1962
2
1
cave, cemented doublet component 1.25-1.25 predominant
3,059,536
ly concave forwardly. The doublet L25—L26 has a col
ZOOM LENS SYSTEM
lective internal contact surface R9 and the mean refrac~
Arthur Cox, Park Ridge, and Walter J. Johnson, Munde
lein, Ill., assignors to Bell & Howell Company, Chi
cago, 111., a corporation of Illinois
Filed May 26, 1961, Ser. No. 112,855
1 Claim. (Cl. 88-57)
tive index of the lens L25 exceeds that of the lens L25.
5 The stationary member 23 is a positive doublet L27 pre
dominantly convex rearwardly, and forms a substantially
afo'cal lens system with the members 21 and 22, it being
possible to use this afoca'l system as an attachment or
This invention relates to a zoom lens, and more par
built in with the prime lens member 24 or with other
ticularly to a zoom lens highly corrected over a large 10 prime lenses. The prime lens member 24 behind ‘the stop
range of magni?cation.
An object of the invention is to provide a minaturized
25 includes a front positive singlet L28 predominantly con
vex forwardly, a biconcave singlet L29 predominantly con
zoom lens highly corrected over a large range of magni
cave forwardly, a positive meniscus singlet L30 concave
?cation.
forwardly and a rear :biconvex singlet L31- The lenses
Another object of the invention is to provide a com 15 L21 to L3, have spherical surfaces or radii of curvature
pact inexpensive zoom lens highly corrected over a mag
R21 to R41, axial thicknesses t2, to t3;, and axial separa
ni?cation range of at least three to one.
tions s21 to sag. The separation s25 of the components
It is to be understood that the terms “front” and “rear”
L27 and L28 is sufficient to provide clearance for the stop
as herein used refer to the ends of the objective respec
25 and a known ?lter member (not shown) which may be
tively nearer the long and short conjugates thereof.
20 selectively inserted into and removed from the space be
In the accompanying drawings forming a part hereof,
the single FIGURE illustrates -a zoom lens described here
tween the components L27 and L28.
The equivalent focal length of the above-described lens
in and embodying the invention, and shows the zoom lens
is variable over at least a three to one range of magni?
in the long, equivalent focal length adjustment thereof.
cation while maintaining a high degree of optical cor
The invention provides a miniaturized zoom lens or 25 rection for a large aperture of at least f/1.8 throughout
variable equivalent focal length objective having a front
the range.
positive member, an intermediate negative member and
A preferred example of the zoom lens forming a speci?c
a rear positive member. The front positive member is _
embodiment of the invention and having a magnification
movable non-linearly during zooming and preferably is
adjustable for focusing also. The intermediate negative
range of about three to one is constructed in conformity
30 with the following table wherein dimensions are in terms
member is movable linearly for zooming, and ‘the rear
member is ?xed. Preferably, the front member includes
a front positive doublet and a rear positive singlet, the
intermediate negative member has a front negative menis
cus singlet and a biconcave rear doublet, and the rear 35
member comprises a rear prime lens group and a front
of inches and the refractive indices for the sodium D line
and the Abbe dispersion numbers are respectively desig
nated at nd and V:
-
[?/LS. E.F.L.=1.1737 Telephoto, .6490 Median, .3604 Wide Angle.
-
B.F.L.=.2525]
singlet separated by a stop from the prime lens group
and forming an afocal system with the front and inter
mediate members.
Referring now in detail to the drawings, the zoom lens 40
shown therein includes a front lens member 21, an inter
mediate lens member 22 and a rear lens member made up
of a component or member 23 and a prime lens or mem- ‘
ber 24 with a stop 25 positioned between the‘mem-bers 23
and 24. ‘The members 23 and 24 are stationary or ?xed, 45
and, during zooming, the member 21 is moved non
linearly relative thereto, ?rst moving to the left from its
extreme telephoto position shown in FIG. 1 until it reaches
the position thereof shown in FIG. 2, which is the inter
mediate zooming position of unit magni?cation, and then 50
moves to the right to its extreme wi
grown in FIG. 3.
1
i
.
'
-~
mem r 21 also is adjustable rela
' 've to t e members 22, 23 and 24 for focusing for dif
’- ferent object distances, and any focus of the zoom lens for‘
any_ settinggqf thehmember 21 is correct for all zoomingl 55
psitions. D?'?rig zoomi?gf'the’membef?wis'movable
to the e t linearly relative ‘to the member 21 from its ex
treme telephoto position shown in the‘ drawing to its ex
treme wide angle position. A suitable lens mounting and
zooming structure for the zoom lens disclosed herein is 60
disclosed and claimed in co-pending application Serial No.
854,732 ?led November 23, 1959, by F. W. Mellberg and
assigned to the common assignee.
The front member 21 comprises a front biconvex,
cemented doublet 1.21-1.22 and a rear singlet L23 pre 65
dominantly convex forwardly and spaced closely to the
doublet Law-L22, and having a dispersive internal cont-act
surface R22. The mean refractive index of the lens L21
While the invention is thus described, it is not wished
exceeds that of the lens L22. The linearly movable nega
to be limited to the precise details described, as changes
70
tive zooming member 22 comprises a front negative
may be readily made without departing‘ from the spirit
meniscus singlet L24 convex forwardly and a rear bicon
of the invention.
8,059,536
4
3
What is claimed is:
A zoom lens constructed in substantial compliance with
the following table in which dimensions are in terms of
inches, and proceeding from front to rear L21 to L33 desig
mate the lenses, R21 to R41 the radii of curvature of the
surfaces, in to tn the axial thicknesses, s21 to s28 the axial
separations, nd the indices of refraction for the sodium D
line and V the Abbe dispersion numbers:
No references cited.
[f./1.8. E.F.L.=1.1737 Teleghg‘ti, .?égozmlvledlan, .3604 Wide Angle. 10
hi=.061
na=1.751
m=.210
nd=1.620
15
an=.005
t2a=.150
72d=1.620
.810 Telephoto
t24=.039
has
nd=1.617
m==.120
t25=.036
tu=.097
1id=1.751
25
.0503 Telephoto
na=1.751
30
nd=1.620
72d=1.620
35
nd=1.620
nd=1.751
40
na=1.651
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