350-47 l.

SROR/SEARCH ROO

2.854,890

VOct. 7, 1958

JRO MUKAHIGH APERTURE WIDE ANGLE LENS

2,854,890

Filed Jan. 4, 1956

T23 as-001
0-001
0.
-2%. 0SPHERICAL ABERRATION ASTIGMATIC ABERRATION DISTORTION ABERRATIONINVENTOR.

BY uro ?uw
Arrorway--United States Patent Office2,854,890
Patented Oct. 7, 1958

1.

2
-the heavy solid line D is the graph of the distortion
aberration for each angle of incidence.
The specific data for one embodiment of the lens array

2,854,890
HIGHAPERTURE WIDE ANGLE LENSJiro Mukai, Musashino City, Tokyo, Japan, assignor toCanon
porationCamera
of JapanCompany, Inc., Tokyo, Japan, a cor

Application January 4, 1956, serial No. 557,374
Claims priority, application Japan January 14, 1955
2 Claims. C. 88-57)of the instant invention is:
If:10

rt as0.579

r =1.787

a 0,369
r as0,573

Ts as 0.267

2a=60°

E: 1.8Ns, 6584

Nas1,6584
Na1,6987

as -0.297
This invention relates to high aperture wide angle 15
N=16204
lenses in which major image distortion and astigmaticf = -0.215
Nsal. 5750differences are elimination without introducing an increasers a -3.299
in the other abberation as such as is observed and con
N=1. 6779
c-0.422
stitute vital defects in the prior known wide angle lenses
having a wide aperture of F:1.8.
20
res 4,250
A clearer concept of the scope and purpose of thisris -1.057
invention may be obtained from the following description,
taken in connection with the attached drawing, in which: ,Fig. 1 shows a sectional view of one illustrative em
In this invention, when the condition of
bodiment of the wide angle lens having a total angle of 25
sixty degrees with an aperture of F:1.8 according to this
0.3 farC0.45 f, 0.2 fars<0.35 finvention; andis given for the meniscus lens group LL3 and theFigs. 2 to 4 inclusive show the aberration graphs spheriindex of refraction for the d-line of the lenses
cal, astigmatic and distortional, of the lens of this invention.
30 L1, L2, L4 L-8, L7 is given aS 1.6<N1, NC1.67,1.6<N, N, NC1.72, the lens array is kept at a Petzval
The structure of the lens according to this invention
sum of about 0.25, the image is flat and, in addition,
comprises four air spaced groups of a total of seven
the astigmatic difference is less, see Fig. 3. Facing thelenses, the first group being a positive meniscus lens Lt.
positioned with its convex surface towards the object, the cemented convex surface r of lens group LL3 towards
second group being a meniscus lens comprising a posi 35 the object serves effectively to reduce the chromatic aber

By observing the relations
tive lens L2 and a negative lens La cemented together and ration of magnification.
f for the thickness of the second group
positioned with its convex surface and cemented surface da-dg0.13
along the optical axis 0.18 fadsaO.28 f for the distancer towards the object, the third group being a meniscus
lens comprising three lenses L4, L5 and L6 cemented in along the optical axis between lenses La and L4, andthe order of positive, negative and positive, positioned 40 0.16 farC0.25 f for the radius of curvature of thecemented surface of L4, L5, coma aberration around 20with its concave surface towards the object, having rof picture angle in the image field can be minimized.
of the two cemented surfaces strongly curved towards theThe differences in the indices of the refraction of d-line
object, and the fourth group is a positive convex lens L.
The following conditions must be satisfied by the lenses in lenses L5 and L should be chosen above 0.08 for theof the instant invention, where the successive radii of purpose of reducing coma aberration. By so doing, very
results will be obtained as shown in thecurvature in the direction from the object to the image satisfactoryaberration graphs of Figs. 2 to 4. Notwithstanding its .
side are designated by r with an increasing subscript, the highof F:1.8, the wide angle objective of theaxial spacings between lenses by d with similarly increas instantaperture
invention has a greatly reduced and essentiallying subscripts, the indices of refraction of the d-lines of 50 eliminatedimage curvature and astigmatic difference as
the optical glass of the successive lenses by N with simi
to prior known wide angle lens arrays and withlarly, increasing subscripts, the dispersive powers of such compared
the stated advantages does not adversely affect the otherlenses by V with similarly increasing subscripts, and f aberrations.
the effective focal length of the complete lens array:
What I claim is:
55 1. A high aperture wide angle photographic objective(1)
0.3 farC0.45f
0.2 fars<0.35 f(2)d--da-(0.13 f
0.18 fads<0.28 fof seven lenses divided into four groups air-spaced fromeach other comprising a first positive meniscus lens with
(3) 0.16f-rC0.25 f
its convex surface facing the object side of the objective,(4)(Ns-Ns)>0.08(5) 1.6<(N1, N2)<1.67 1.6<(N, N N)<1.72 60 the second group is a second positive meniscus lens anda first negative meniscus lens cemented to each other
In Fig. 2, the heavier chain line S1 is the spherical aber with the cemented convex surfaces thereof facing suchration graph of the spectrum d-line, the fine chain line
side, the third group is a third positive meniscus
S is the graph showing the deviation of the spectrum objectlens, a second negative meniscus lens, and a fourth posi
d-line from the sine condition, the heavy solid line S3 thetive meniscus lens cemented at the adjacent faces andspherical aberration graph of the spectrum g-line, and the 65 withthe concave surface of the third group toward suchfine broken line S the graph of the deviation of the object side, and the fourth group is a bi-convex lens,
spectrum g-line from the sine condition, of the lenses of in which the radii of curvature r subscript of the in
the invention. In Fig. 3, the heavy solid line As is thedividual lens surfaces in succession from the object side ofgraph of the sagital field curvature, and the fine broken the objective, the distances d subscript along the opticalline A that of the meridional field curvature. In Fig. 4, 70 axis of the lens thicknesses and air spacings, and the2,854,890

3.

refractive indices N subscript of the d-line of the individual lenses, satisfy the relations:
0.3 farC0.45 f
0.2 fars(0.35 f
da-dg0.13 f

0.18 fadsC0.28 f
0.16 farC0.25 f(N-Ns)>0.08
and

1.6<(N,N)<1.67

4.

the dispersion factors, V subscript of the individual lenses,
are:
f=100Lens

L1---------------

F:18
Radir

r is 0,579
r is1.787

r is 0.369
L4--------------r is 0.573
L!--------------ris 0,267
r = -0.297
L4--------------r = -0.215
LS--------------rs = -3.299
L6--------------r = -0.422
ros 4,259
Lt.--------------ris -1.057

Including angles 60
Thicknesses
andDistances dd = 0,097
da0.005
da0.079

d =s0,032

Nw

Nu. 6584 WS0.8
w-N=1.6584 Was 50.8
N=16987 V30.

where f is the effective focal length of the entire obdi se), 230
jective.
2. A high aperture wide angle photographic objective
dis so,055 Nas1. 6204 Wab0.3
of seven lenses. air spaced into four groups comprising
d so. 026 N=1.5750 Wis 4.3
a first positive meniscus lens of which the convex sur
ds=0, 069 N=1. 6779 W=55,3
face faces the object side of the objective, a second posi
do so. 00.
tive meniscus lens is cemented to a first negative meniscus
lens to constitute the second group of which the cemented
do=0.083 Nr. 6935 Weas5.3
convex surfaces face such object, side, a third positivemeniscus lens is cemented to a second negative menis
cus lens which in turn is cemented to a fourth posi
References Cited in the file of this patenttive miniscus lens to constitute the third group of 25
UNITED STATES PATENTS
which the concave surface and the cemented interfaceof the second negative and the fourth positive meniscus
2,130,760 Warmisham ----------- Sept. 20, 1938
lenses are toward such object side, and a first biconvex
2,389,016 Wynne ---------------- Nov. 13, 1945
lens in which the radii of curvature, r subscript of the2,611,295
Schade --------------- Sept. 23, 1952
individual lens surfaces in succession from the object 30 2,645,973 Ito ------------------- July 21, 1953
side of the objective, the distances, d subscript, along theFOREIGN PATENTS
optical axis of the lens thicknesses and the air spacings,
323,138 Great Britain ---------- Dec. 24, 1929
and the refractive indices, N subscript of the d-line and