"UUHI
Patented July 2, 1940
2,206,195
UNITED STATES PATENT OFFICE
2,238,195
TELESCOPE EYEPIECE
Albert Kiinig, Jena, Germany, assignor to the
?rm of Carl Zeiss, Jena, Germany
Application December 14, 1938, Serial No. 245,657
In Germany December 24, 1937
8 Claims.
The present invention concerns a telescope eye
piece comprising three convergent elements ax
ially spaced by air, in which the sum of the dis
tances apart of the elements amounts to at most
one-third of the focal length of the eyepiece, and
in which the rear element, 1. e., the element fac
ing the eye, is a single lens and in which the me
dial element contains at most one layer of ce
ment, the front, 1. e., object side, lens of this
10 medial element and that lens of the front element
which lies next thereto being convergent, and at
least one surface of one of these two lenses being
a cemented surface.
When the convergent re
fractive powers are produced predominantly by
15 the parts near the eye and in particular by the
eye-lens, an eyepiece of the said kind has, as is
often desired, the property that the distance
apart of the exit pupil and the rear surface of
the eye-lens is comparatively great as compared
20 to the total focal length of the eyepiece.
When the curvature of the rear surface of the
eye-lens is within the said limits, the demands on
the correction of the image outside the optical
axis can be arrived at if, according to the inven
25 tion, the rear surface of the rear element has a
(01. 88-57)
hand, a simple construction of the eyepiece hav- h
ing an especially good correction of the astigma
tism of oblique pencils can be arrived at when
the front element is a single lens whose front sur
face has a refractive power which is suitably at _
most one-quarter of that of the entire eyepiece. '
The Figures 1, 2 and 3 of the accompanying
drawings illustrate schematically on a reduced
scale three constructional examples of the inven
tion in elevational sections. In each of these
three examples, the focal length amounts to 100 10
units of measurement.
The ?rst example (Figure 1) comprises a front
element consisting of two cemented lenses I and
II, a medial element constituting a single lens III,
and a rear element constituting a single lens IV. 15
In the second constructional example (Figure 2),
the front element is a single lens V, the medial
element consists of two cemented lenses VI and
VII, and the rear element is a single lens VIII. 20
The front element of the third constructional ex
ample (Figure 3) consists of three cemented lens
es IX, X and XI, the medial element of two lenses
XII and XIII, and the rear element is a single
lens XIV. The front focal planes of the three
constructional examples are indicated by the foci 25
curvature the magnitude of which lies between
F1, F2 and F3, respectively, and the image ?eld
the refractive power of this lens and the nega
tive value of this power, and if, further, at least diaphragms B1, B2 and B3, respectively. The po
eleven-twentieths of the algebraic sum of the sitions of the exit pupils of the three construc
30 refractive powers of the cemented surfaces of tional examples are indicated by the pupil cen
tres P1, Peand P3, respectively. 1‘ designates the"
the said convergent lenses of the medial ele
ment and the front element are produced by one radii and d the thicknesses of the lenses. D sig
of these cemented surfaces, and if the numerical - ni?es the free diameters of the image-?eld dia
value of this sum is greater than one-twelfth of phragms and l the distances. The kinds of glass
36 the sum of the numerical values of the curvatures used are determined by the respective refractive ~35
of those surfaces of the said two lenses which face indices no for the D-llne of the solar spectrumv
each other. By refractive power of a cemented and by the Abbe conditions v.
The following Table 1 shows the kinds of glass,
surface is to be understood the quotient of the dif
the Table 2 the diameters D of the image-?eld
ference of the refractive indices of the lenses ce
40 mented to each other, divided by the radius of diaphragms, the Table 3 the distances 1 and
thicknesses d, and the Table 4 the radii of our
curvature of the cemented surface. This re
fractive power is positive with a convergent and vature r of the three constructional examples.
negative with a divergent cemented surface.
Table 1
To obtain an especially great distance apart of
45 the exit pupil and the eye-lens, it is further ad
vantageous to provide that the rear surface of
the medial element of the eyepiece is convex to
ward the eye and has a refractive power amount
ing conveniently to at most half the refractive
50 power of this element, and that the medial ele
ment of the eyepiece is a single lens. The correc
tion of the image outside the optical axis, espe
cially for coma, is facilitated by using as a front
element three cemented lenses the medial lens
55 of which is preferably divergent.
On the other
"D
LensesI VII, XIII ............................... _.
I
1.7174
29.5
Lenses 1i,111,1v,v,vr,vm,1x, xi,xn,xrv__.-_ 1.5163
64.0
Lens X.
33.9
..
1.6477
50
Table 2
D1=108
D2=115
D3=125
55
2
2,206,195
Table 3
mented surface of said two convergent lenses
amounting to at least eleven-twentieths of the
11:55.0
(11:: 6.7
1': = 0.6
do =23.O
(12:43.3
l z2= 1.4
la =67.0
19 =2o.o
(13:16.7
la= 1.4
(14:16.7
14:92.0
m l5=68.0
d9 =37.9
dic= 6.3
d1i=52.0
Z10: 0.6
d12=363
1113: 6.3
Zn: 0.6
d14=22.2
Z12=69.0
d5=30.0
la= 0.6
(15:40.0
15 d1= 6.7
,
Table 4
n=-- 472
To =— 140
1‘17=+121.5
rz=+ 120
Tl0=+ 183
1'1a=-—151
=- 120
7'11=— 114
r19=+200
2° r4=+ 19o
m=—l450
T20=—174
T6=— 447
rs=+ 112
Ti3=+ 101
114:”
1‘21=—326
r22=+ 93
T15=+ 367
n3=+460
T7=+1000
25 Ta=+ 740
I claim:
1‘1s=— 121.5
1. An optical system for telescope eyepieces,
comprising a front, a medial and a rear element,
said elements b‘n
and axially
30 space y air, the sum of the distances apart of
said elements being at most one-third of the
focal length of said system, said rear element
being a single lens, the numerical value of the
curvature of the rear surface of said lens being
smaller than the numerical value of the refrac
tive power of said lens, said medial element con
sisting of at least one lens and at most two lenses,
said front element consisting of at least one
lens, the front lens of said medial element and
40 that lens of said front element which faces this
front lens of said medial element being con
vergent, at least one optically effective surface of
one of said two convergent lenses being a cement
ed surface, the refractive power of one cemented
surface of said two convergent lenses amounting
to at least eleven twentieths of the algebraic sum
of the refractive powers of all cemented sur
faces of said convergent lenses, the numerical
value of last said sum being greater than one
twelfth of the sum of the numerical values of
the curvatures of those surfaces of said con
vergent lenses which face each other.
2. In an optical system according to claim 1,
said medial element consisting of two cemented
lenses.
3. An optical system for telescope eyepieces
comprising a front, a medial and a rear element,
said elements being convergent and axially
spaced by air, the sum of the distances apart of
said elements being at most one—third of the
focal length of said system, said rear element
being a single lens, the numerical value of the
curvature of the rear surface of said lens being
smaller than the numerical value of the refrac
tive power of said lens, said medial element con
sisting of at least one lens and at most two lens
es, the rear surface of said medial element being
convex, said front element consisting of at least
one lens, the front lens of said medial element
and that lens of said front element which faces
this front lens of said medial element being con
vergent, at least one optically effective surface
algebraic sum of the refractive powers of all ce
mented surfaces of said convergent lenses, the
numerical value of last said sum being greater
than one-twelfth of the sum of the numerical
values of the curvatures of those surfaces of said
convergent lenses which face each other.
4. In an optical system according to claim 3,
the refractive power of said convex surface of 10
said medial element being at most half as great
as the refractive power of said medial element.
5. An optical system for telescope eyepieces,
comprising a front, a medial and a rear element,
said elements being convergent and axially spaced 15
by air, the sum of the distances apart of said
elements being at most one-third of the focal
length of said system, said rear element being a
single lens, the numerical value of the curvature
of the rear surface of said lens being smaller than 20
the numerical value of the refractive power of
said lens, said medial element consisting of at
least one lens and at most two lenses, said front
element consisting of three lenses, said three
lenses being cemented to each other, the front
lens of said medial element and that lens of said
front element which faces this front lens of said
medial element being convergent, at least one
optically effective surface of one of said two con
vergent lenses being a cemented surface, the re 30
fractive power of one cemented surface of said
two convergent lenses amounting to at least
eleven twentieths of the algebraic sum of the re
fractive powers of all cemented surfaces of said
convergent lenses, the numerical value of last 35
said sum being greater than one twelfth of the
sum of the numerical values of the curvatures of
those surfaces of said convergent lenses which
face each other.
6. In an optical system according to claim 5,
the medial lens of said front element being di 40
vergent,
7. An optical system for telescope eyepieces,
comprising a front, a medial and a rear ele
ment, said elements being convergent and axially '
spaced by air, the sum of the’distances apart of 45
said elements being at most one-third of the
focal length of said system, said rear element be
ing a single lens, the numerical value of the cur
vature of the rear surface of said lens being
smaller than the numerical value of the refrac 60
tive power of said lens, said medial element con
sisting of at least one lens and at most two
lenses, said front element being a single lens, the
front lens of said medial element and that lens of
said front element which faces this front lens of 56
said medial element being convergent, at least
one optically effective surface of one of said two
convergent lenses being a cemented surface, the
refractive power of one cemented surface of said
two convergent lenses amounting to at least 60
eleven-twentieths of the algebraic sum of the
refractive powers of all cemented surfaces of said
convergent lenses, the numerical value of last
said sum being greater than one-twelfth of the
sum of the numerical values of the curvatures 65
of those surfaces of said convergent lenses which
face each other.
8. In an optical system according to claim 7,
the refractive power of the front surface of said
front element amounting to at most one-quarter 70
of the refractive power of said optical system.
of one of said two convergent lenses being a ce
mented surface, the refractive power of one ce
ALBERT KbNIG.
H”)