Wide angle eyepiece with long eye-relief distanc

Eichenthal, J.

Gelles, R.

Rosin, S.

English

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https://ntrs.nasa.gov/search.jsp?R=19710015381 2020-03-17T02:59:37+00:00Z
Oct. 14, 1969 S. ROSIN ETAL 3,472$577 
WIDE ANGLE LONG EYE-RELIEF EYEPIECE 
Filed March 4, 196 
I.VVENI$ORS 
SEYMOUR' &@?s"/N 
RUB/N G6ZLES 
B y  JUDAX E/CXK/r/P"MAI 
3,472,573 United States Patent O6ce Patented Octe 14, 1969 
1 2 
may best be described in lay terms as molding h e  surface 
3,472,577 deliberately to achieve the desired results, using noemilii 
WIDE ANGLE EOhG EYE-REI,IEF EYEPIECE my trace methods to arrive at  the miurion. 
Scjmour Rosin, hIias\.!pccgua I'ark, Ruhin Gelles. Far Mathematically. the procedure is as follows: The sur- 
Rockaway, and Judah Eichenthal, Brooklyn, N.Y., as- face may be described by the equation 
signors, by mcsne assignment$, to the United States of 
A~nerica as represented by the Adn~inistrator of the Na- 
tional Aeronautics and Space Administration x= 
Filed Mar. 4, 1966, Ser, No. 532,006 
Int. CI. GOSb 3/04, 1 3 / J S  whare r is the railius of curvature a t  the axis of the siiur- 
U.S. CI. 350-189 6 Clailns 10 face. The process involves variation of the constants b, c, 
d,  etc. until the s and t astigmatic curves are where 
desired. 
ABSTRACT O F  THE DISCLOSURE While the eyepiece lens may be a ~Iano-convew lens 
A wide angle, long eye-relief eyepiece having power, 
astigmatism, and coma corrections incorporated into a 
single clement which is solely responsible for mono- 
chromatic performance and a zero power triplet correct- 
ing for lateral color ahberation. The single element may 
he either pl;ino-convex or  double convex. Also, a negative 
field lens properly aspherized to eliminate spherical ab- 
beration may be included. 
This invention relates to an cycpiece having wide angle 
application, and more'particularly rc1;ctes to a novel wide 
angle eyepiece which has a relatively* long eye-relief or  
giea!er thzn normal eye clearance from the final lens of 
the eyepiece wherein substantially all power, astigma- 
tism and coma corrections are incorporated into a single 
element which is solely responsible for the monochromatic 
perfornxnce of the eyepiece, while a zero power triplet 
corrects for lateral color aberration. 
Many applications of optical instruments require a 
relatively !ong eye-relief distance so that the eye can be 
placed at a distance somewhat greater from the final lens 
of the eyepiece than usual. In particular, various visual 
instruments used in spacecraft, such as the Apollo space- 
craft: have need for eyepieces with longer than usual 
eye-relief and reIati\'ely short axial length because of its 
~!nusual environmental condition. In the design of eye- 
pieces. the aberrations of major concern are astigmatism 
and lateral color. The next aberration of consequence is 
coma with its degree of correction determining the maxi- 
mum usable evit pupil areas. Spherical and axial color 
aberrations are relatively unimportant and may he handled 
by minor adjustments in the remainder of the optical 
system. Petzvwl curvature and distortion aberrations are 
gcncrally accepted without attempts to correct these aher- 
raticlnr. 
Wide angle eyepieces are known to the art, and arc 
generally dcsiqned to incorporate a close grouping of 
highly convergent elements with deep curves required for 
color correction. The amount of axial distance occupied 
by the glass, howevcr, m:ckcc, it difficult to shift the princi- 
p;tl plane5 back far enough toward the eye to obtain 
longer than usual eye clearance without running into se- 
vere lens curvatures a t  the same time. 
The principle o f  the present invention is to construct a 
wide angle eyepiece which also provides a rel:ctively large 
eye clearance by using a single elenlent for the provision 
of pou.er. astigmatism and coma correction so that this 
single element completely controls the nionochromatic 
rxxforman~.e of the eycpicce. The principal points of the 
eycpicr:~ ;ire then identic:~l wilh those of this element 
which ic, I hc onc nc:~rest the cyc. I .:~tcr:il color corrections 
arc f l ~ c n  :~cco~nplisl~ccl in :I  7 C F O  powcr grouping Iociitcd 
hctwccn thi\ Icns :~ntl  thc foc:~l pl:~nc. 
'l'hc rlrc:in\ hy which Ihi\ is; :~ccon~pli\lictl is to con.;tr~rct 
:I{ Ic;rk,t one of 111c s~~rf:iccs o f  (hi\ Icn.; o f  a strongly non- 
spherical form :~ntl to choose the cocfficienls of this sur- 
face so ;IS to control the astigmatic curves. This proce3s 
with the aspheric-correction in&rwra(ed into the convex 
surface, it is also possible to use a two-surface convex 
lens with the power shared between the two surfaces and 
the aspheric correction applied to either of the surfaces. 
Thus, an additional degree of freedom is mTndie available 
for aberration correction. In addition, a negative field 
lens which is properly aspherized to eliminate spherical 
aberration of the exit pupil may be additionally i n c o r p  
rated into the evepiece. 
~ c c o r d i n g l ~ ;  a primary object of this invention is to 
provide a novel wide angle eyepiece which has a field of 
25 view of a t  least 60". 
Another object of this invention is to provide: a novel 
wide angle eyepiece which has a re'laiively long eye-relief 
distance. 
Yet another object of this invention is to provide a 
30 novel wide angle eyepiece wherein all of the p o w r ,  astig- 
matism and coma corrections are incorprated into a 
single element which is solely responsible for mono- 
chromatic performance of the eyepiece while lateral color 
corrections are obtained from a zero power grouping 
35 which could take the form of a triplet lens. 
These and other objects of this invention will become 
apparent when reading the following description md a- 
companying drawings, in which: 
FIGURE 1 is a side cross-sectional view taken through 
40 the optical axis of an eyepiece constructed in accordance 
with the invention. 
FIGURE 2 is a view similar to FIGURE 1 which shows 
a second embodiment of the invention. 
Referring first to FIGURE 1, there is illustrated therein 
45 a first embodiment of the present invention incorporating 
a plano-convex lens 10 having an optical axis 19, with 
the planar ~urface  12 of lens 10 facing the exit pupil 13. 
Note that the spacing from surface 12 to exit pupil 13 is 
approximately 2 3 j ~  inches which e:xceeds the 2 inch focal 
Go length of the eyepiece. A triple lens 14 compoed of a 
convex lens 15a in surface-to-surflace contact with hi;8ano- 
concave lens 15b and 15c is then spaced from %ens 10 to 
complete the long eye-relief system. 
The following Table 1 defines %ens curvatures and 
'' other lens details for the system of FIGURE B in terms 
of surfaces 12, 16, 17, 18, 19 and 20 where all units are 
in millimeters: 
whcrc I:.i:. 5 0 4 7 ;  13.1.. 12.73, pi~pil 57 15 
In lhc \pccilic dc+ign in accordance witla the invention, 
\~irf:~cc 16 is prefer:rhly de\ipnerl lo have an ;c\phoic 
surf:~ce 1:tthcr tli;cn the \pIicric;d srrrface indiwted in 
'Pablc I in oltler lo prcvent it 5cverc &>reakdowra of the  
3,472, 
3 
~rstigmatic sual'aces. Iu particular, a third order analysis 
for a flak tangentian field indicates that the surface 16 
ihould follow the following equation: 
The surface configuration of surface 16 could vary from 5 
that of Equation 2 since a ray trace of Equation 2 \how? 
in asphesic salrface breakdown somewliat beyond % the 
-Id cf view I hers, the surface 16 could be further motli- 
ed by the ;~dditson 01 another term ,I\ followq: 10  
7 Qhl\ n~odif i~at~on will keep the astigm~rtic sur fucc\ 
(#rader control over the full 60" ficld of vicw. The zero 
power (riplet 14 of FICiURE 1 provides very good control 1; 
SOP the lateral color aberration with this aberration belng 
co~iidcrabiy less than that found with conventional eye- 
.. cces The dl\tortion will be moderate and opposite to 
ihat lasuaiiy experienced with a conventional eyepiece and 
 ill be barrel shaped at the eye rather than the usual pin- 20 
-,lashion shape, li should, however, be noted that other 
s,plet lens forms or groupings could be used where the 
group will have substantially zero power. Thus, the group 
C O L ? I ~  take the form of a central concave lens interposed 
between two convex lenses; and could further include 25 
~ w o  doublets, serving as a triplet in various orientations 
~ i i b  respect to one anlother. 
The major drawback with the design of FIGURE 1 
yncorwrating Equation 3 for the surface 16 is that coma 
correction is limited so that the exit pupil 13 should be 30 
In addition, surface 46 is also aspherized and follows 
a curvature identified as follows: 
The lens of Fl<;ilJKl: 2 is :In cycpiccc used with ;I I X 
lclcscope having a liclcl o f  vicw o f  60". Nolc that the 
surfi~cc 47 lics i n  tltc focal plitnc. 
C;~lcul;~lions show Lh;11 the i~n ;~gc  is cxccllcnt wvcr a 
relalive aperture of 1::4 or more. Morcovcr, the optical 
quality and surface iiccusacy ol' thc lenses is about that 
of spectacle lenses so that standard manufacli~ring tech- 
niques can be used. 
We claim: 
1. A wide angle, long cye-relief eyepiece comprising a . 
first lens having at least a first convex surface; a substan- 
tially zero power lens grouping spaced from said first 
lens and having an optical axis coaxial with the optical 
axis of said first lens; an exit pupil; said convex lens inter- 
posed between said exit pupil and said zero power lens 
grouping; the surface of said first lens facing said exit 
pupil spaced from said exit pupil by greater th,an three- 
fourths of the focal length of said first lens; said first lens 
having a focal length of approximately two inches and 
the convex surface being aspheric and having the general 
equation of: 
iestrncted to 5 mlllirneters or less. However, coma correc- 2. The device as set forth in claim 1 which includes a 
iaon can be considerably improved by modifying the negative field lens spaced from said zero power lens 
aspherlc trace of Eciuation 3, particularly by slightly grouping facing the side of said zero power lens grouping iowerlng the db~olute values of the y4 power and ye power from said first lens. 
coeFi~lenti 33 3. The device as set folth in claim 1 wherein said first 
i n  TliGbRF I ,  lens 10 is shown as a plano-convex lens. lens is a plano-convex lens. 
F8CralRE 2 zliiisiratea a modification of the eyepiece of 4. The device as set forth in c l ,~ i~n  1 wherein silid 
-!sJIJR& 1 whzrcln a convex lens replaces lens 10 of aspheric surface has the general 
1 IGLJRE i and a negative field lens properly aspherized 
added to eilrninate spherical aberration at the exit 40 x = - 1 . 2 5 ~  10-2~2+9.147 x 10-?y4- 1.75 X 10-10~8 
pugti 5. A wide angle, long eye-relief eyepiece comprising a , Rcferrlag now to FIGURE 2 and as mentioned above, first lens having at least a first convex surface; a substan- 
tie main eyeprece lens is lens 30 which is convex at both tially zero power lens grouping spaced from said first 
,ides A modlfied arlplet 31 replaces the triplet 14 and 15 lens and having an optical axis coaxial with the optical 
composed of convex lens 32 faced on either side by plano- 45 axis of said first lens; an exit pupil; said convcx lens 
concave lenses 33 and 34. In order to correct for spherical interposed between said exit pupil and said zero power 
aberration a& the exit pupil for the complete instrument, lens grouping; the surface of said first lens facing said 
a negailve field lens 35 is provided in the manner described exit pupil spaced from said exit pupil by greated than 
~ r a  U S. Patent 2,588,414 in the name of Rosin. three-fourths of the focal length of said first lens; said 
The coristapts used in the system of FIGURE 2 are first lens having a focal length of approximately two 
listed in the following Table 2 which lists the constants inches and the convex surface being aspheric and having 
for surfaces 40, 411, 42, 43, 44, 45, 46 and 47: the general equation of: 
T A B L E  2 
~=8.2453 X 10-3y2-8.0624 x 10-?y4+ 1.9744 
Free 55 X 10-lly6-9.2216X 10-16ys 
SurYscc Radius Aperture Separation Qlsss 
where x and y define a tangential field. 
40. PA y 80 22.4 Lag17  788504 
4 1 - c Q  1 , 85 . 3  6. The device as set forth in claim 5 which includes a 
42 .. ?!dno 77 5 I 6 ~ 1 1  784257 negative field lens spaced from said zero power lens 
4.J ?L 5 1  70 
44 - .. - ;2 5') 67 
31.H 5 1 SF11 LaK17 &4"57 7XX504 grouping away from said fint lens: said negative, field 
45. P i d n n  FA I F  3 GO lens having an aspheric surface generally following the 
46 . -3VJ 14 4'1 J.'J ZK7 508611 
47 Piano 48 .... . equation: 
x=: 1.6659x 10-3y2-4.204Ox 10-8y4-4.7293 x 10-lOys 
shere E F 41.09,  B.F.=18.93; pupil=--57.15 
a s  pre~iously p i n t 4  out, the desired aspheric cor- References Citcd 
:ectlon previously applied to surface 16 in FIGURE 1 ('" 
Cdn now be applied to either of surfaces 40 or 41 of lens UNITFI) SI ATES I'ATEN7 S 
30 so that  he power of lens 30 is shared between two 1,968,222 7/1934 Richter. 
5drfaces 40 and 41 lrhe two convex surfaces 40 and 41 2,719,457 10/ 1955 Tripp --------------- 350--24 
further provide an additional degree of freedom for mak- 
swg the aberration correction. 7 0  JOHN K. CORBIN, Primary Examiner 
In FIGURE 2, surface 40 has been selected to receive 
the aspheric correction curvature, which is defined as fol- U.S. C1. X.R. 
iows: 3 5 k 2 2 5 ,  230, 234 


Wide angle long eye relief eyepiece Patent

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