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NOV- 5, 1946- '
B. E. LUBOSHEZ
2,410,667
. ARTIFICIAL_HORIZON FOR SIGHTING INSTRUMENTS
Filed April 18, 1944 '
2 Sheets-Sheet 1
FIG; 2.
BENJAMIN E. LUB OSHE’Z V
INVENTOR f
I byWWI-TURN];
- NOV. 5, 1946.
I B_ EILUBOSHEZ
'
2,410,667 I
ARTIFICIAL HORIZON FOR SIGHTING INSTRUMENTS
FiledlApril 18, 1944
2 Sheets-Sheet '2
13
47
BENJAMN E. L UB OSHEZ
’
INVENTOR
ATTORNEYS
' 'Patented'Nov. 5, 1946
- ' ‘2,410,667
umra
S
TBS PATENT
2,410,667
ARTgIFICIAL HORIZON FOR. SIGHTING‘
'
INSTRUMENTS
Benjamin E. Luboshez, Rochester, N. Y., assignor I
to Eastman Kodak Company, Rochester, N. Y.,
a corporation of New Jersey
_
Application April 18, 1944, Serial No. 531,582. -
17 Claims. (Cl. 88——23)
instruments for determining the horizontal direc
Still another object is to provide an arti?cial _
tion in relation to a point of observation, and par- '
horizon of. the type set forth which comprises a
ticularly to an improved arti?cial horizon for such
instruments.
‘
‘
In such ‘instruments ordinary bubble levels
v pattern made up of the optically combined images
of two or more individualk?ducial marks so that
the individual parts of the pattern appear to move
independently asv the instrument is tltlted in
are generally used for the arti?cial horizon. The
main disadvantage of the ordinary bubble level
used on such instruments lies in the fact that the
size of the bubble varies with changes in tempera
ture and must be adjusted from time to time ac
‘ cordingly. Furthermore, the sensitivity of such
2
the ball is free from spin so that it will come to
rest at its lowermost position on said race.
This invention ' relates to improved sighting
different directions.
10
.
.
The novel features that I consider character
.istic of my invention are set forth with particu
larity’in the .‘appended claims. The ‘invention
itself, however, both as to its organization and
it is impossible to vary the one without changing
its methods'of operation, together with additional ‘
the other. It ‘has been proposed to use solid .15 objects and advantages thereof, will best be under
stood from the following description of speci?c
“bubbles” rolling on a concave spherical surface
embodiments when read in connection with the
to overcome the‘undesirable variations in the
accompanying drawings in which, '
A
sizes of the bubbles due to temperature changes.
Fig. 1 is a schematic showing of an .artiflcia
Whether the horizon used has been an
‘ordinary bubble or a solid “bubble" the image 20 .horizontal horizon constructed in accordance with
one embodiment of the present invention and
appearing in the instrument has been in the form
shown in operative association with asextant,
of a simple bright disk (as with illuminated solid
Figs. 2 and 3 show two different forms which
“bubbles”) or in the form of a pale disk with. a
the horizon images might be,
' ’ '
bright periphery such as is usual with the»
ordinary bubble assembly. In both cases, when 25 Fig. 4 is a diagrammatic view of another em
bodiment of the present arti?cial horizon in
such horizons are used on celestial instruments,
association with a sextant, ‘
1. e., sextants, it is difficult to see a star when it
Fig. 5 shows a plurality of masks bearing differ
lies within the disk. Accordingly, it is the usual
ent. ?ducial marks mounted on a rotatably
practice with such. instruments to place the star
image more orless along the side of the bubble 30 mounted disk for selective use.
a level varies with the size of the bubble, and r
image.
One object of the present invention is to pro
vide an improved arti?cial horizon for use with
Like reference characters refer to correspond
ing- parts throughout the drawings.
‘ .
Brie?y, an‘ artificial horizon according to the
present invention comprises a ball having a re
sighting instruments that shall be entirely free
‘from ‘the objections to the prior art structures 35 ?ecting surface in rolling contact with an arcuate
'
race which is ?xed to the sighting instrument
Another object is to provide an arti?cial horizon
so that the chord of the surface of the race is
of the type set forth which is free from variation
horizontal when the instrument is in use. The
in size due to temperature changes; which can be
ball naturally seeks the lowest point on the rolling
varied in shape or size according to the object 40 “surface as the instrument is tilted‘ and acts the
being observed by the instrument without a?ect
same as a level. The image of one or more ?ducial
ing the sensitivity of the same; and the sensi
marks are projected onto the surface of the ball
tivity of which can be varied without-altering "
and are in turn reflected and/or directed into
‘he shape or size of ‘the image of the arti?cial
the viewpoint. of the instrument simultaneously .
45 with the image of the object being sighted upon.‘
horizon.
'
Still another objectis to provide an arti?cial
Although for purposes of disclosing the arti?cial
horizon which when associated with a particular
horizon constituting the present invention, I have
instrument will provide an image at the viewpoint
shown it in association with a sextant, it is pointed
of the instrument which moves in unison across
out that the invention is not limited to use
the ?eld of view with the object being sighted 50 with a sighting instrument of this particular type
upon as the instrument as a whole is moved.‘
but it is believed that it will be obvious to those
Another object is to provide an arti?cial horizon
skilled in the art that said arti?cial horizon is
of the type set forth which includes a ball having
applicable to any sighting instrument, such as
a re?ecting surface which is in rolling contact‘
theodolites, celestial, and terrestrial telescopes,
with an arcuate race, and which race is such that 55 etc., in which the horizontal direction in rela- mentioned above.
aerate?
tion to the point of observation is desirable or
necessary.
'
. \
three different masks 2d’ are arcuately spaced
on the supporting disc D which is rotatably sup
1
Referring now to Fig. 1, my arti?cial horizon
is shown in association with a well—known type
of sextant which includes a frame it, a ?xed
mirror H, and a pivoted index mirror l2. Light
from a celestial body it strikes the index mirror
l2 and is re?ected to the ?xed mirror H from
which it is then re?ected to the viewpoint of the
instrument, all as shown in full line bearing 10
directional arrows. When directing a bubble 'image to theviewpoint, such a sextant may in
clude a transparent re?ector M inclined to. the
.sight axis add a lens-re?ector combination it
‘composed of a lens it backed up by a mirror ll. 15
Divergent rays from a bubble are adapted to pass
through the transparent re?ector it and then
through the lens it ‘to the mirror it and back
through the lens it to the transparent’ re?ector
ported ina partial ring 28' ?xed to the frame of
the sextant. ‘The edge of the disc D may be
grasped by the ?ngers through the slot S in the
ring 26' and an indexing mechanism including
a spring-pressed ball B located in the ring and
adapted to engage notches N in the edge of the
disc D may be provided.
The image of the fiducial. mark on the ‘mask
is re?ected to the uppermost portion of the roll
ing ball by a transparent re?ector 29. The image
of the ?ducial mark formed in the sphere is re
?ected through the transparent reflectorsv 29 and .
it in turn to the lens-re?ector combination l5
which renders the diverging bundles of rays par
allel so that when they finally reach the ob
server's eye after reflection at M the image of the
?ducial mark appears at in?nity. At the same
in the form of collimated light which it is re .20 time, light from‘ the celestial object is received
?ected to the viewpoint. This optical system for
directing a collimated image of the bubble to the
‘by the index mirror i2 which, when correctly ad
justed, sends thelight to the fixed mirror H and
viewpoint of the. sextant may be referred to as the
then through the transparent re?ector M to the
secondary optical system of the instrument, the
eye at the viewpoint of the instrument. Thus the
system being used for directing an image of the 25 observer sees both the celestial object and the
object being sighted upon to the viewpoint being
image of the ?ducial mark in the ?eld of view
referred to as the primary optical system of the
at the same time and can adjust the angular
instrument; and sighting instruments having
position of the index mirror to obtain coin
these two optical systems are Well known.
cidence.
_
Coming now to the present invention, my ar 30
According to this invention, the image of the
ti?cial horizon is designed to replace the ordinary
arti?cial horizon may be of any desired shape.
bubble level as generally used, and one embodi- '
It may, for example, take the form of a single
ment of it will now be described. As shown in
bright ring of any desired dimensions, or of sev
Fig. 1, the present arti?cial horizon may com-,
eral concentric rings, so that the image of a star
prise .a metal ball it having a polished re?ecting v
or planet can be easily located at the center
surface, a spherical concave rolling surface, or
thereof while the sun and moon images can like
race, it of a certain radius, of the damping ?uid
wise be conveniently centered.
F, and the lower half of a. glass chamber 20, the
ring arrangement, Fig. 2, is most convenient when
bottom 2! of which is roughened and painted a
matte black to avoid re?ections. The glass cham
The concentric
mixed observations of the sun, moon, planets and
40 stars are being made, since there is no need to
ber is sealed with a glass lid 22, an annular space
{id-being left around the margin of the lid for
expansion of the ?uid due to temperature
changes, and to trap-any air bubbles which might
be formed in the ?uid. The d'imping ?uid and 45
the glass of the container are selected so as to
have substantially the same refractive index.
The chamber is ?xed to the lower part of the
adjust the size of the horizon between observa
tions. Another convenient form, unattainable
with ordinary bubble levels, is provided by two
bright lines at right angles, or two pairs of par- ' I
allel lines closely spaced and crossing at right
angles, see Fig. 3. .In the latter case, the images
of stars and planets can be easily located at the
center of the small central square and the sun
and moon i regard 'to the crossed lines. It will
frame of the sextant by a bracket 25 in optical
alignment with the lens-re?ector combination it.
Also ?xed to the frame I 0 of thesextant, above
mark reflected by the ball will be reduced due to
and to one side of the chamber, is a ?ducial mark
the convex nature of the re?ecting surface. For
be appreciated that the image of the ?ducial
and means for illuminating the same. While
this reason, the actual size of the‘fiducial mark
should be larger than the desired image thereof ,
the ?ducial marks may be of, any form, I have
found that a particularly good one for this pur 55 which constitutes the horizon at the viewpoint of
pose is an illuminated transparent opening in an
the instrument.
In sighting instruments utilizing arti?cial hori
opaque mask. As shown, an opaque mask. 25 is
slidably mounted in a holder 26 ?xed to the frame
zons it is desirable, if not necessary, that the
image of the object being sighted upon and the
it. This mask includes one or more transparent
patterns having any con?guration desired and 60 image of the ?ducial mark constituting the hori
mark the image of which is to constitute ,the
zon appear in the same focal plane and move in
unison across the field of view as the instrument
horizon. This mark is illuminated from the rear
as a whole is tilted.
. which when’ illuminated form a. bright ?ducial
This result is obtained in
by an opal diffusing glass El and a light source
28. A plurality of masks of. different patterns 65
may be provided so that the form of the flducial»
mark may be varied to suit di?erent objects being
the present instance as follows. The virtual
image ofthe ?ducial mark formed in the re
?eeting surface of the ball will be formed at a
point within the ball and at a depth approxi
sighted upon. In Figs. 2 and 3 there is shown . mately one-fourth of the diameter thereof. Ac
cordingly, as the ball rolls along the surface the
two convenient forms of ?ducial marks that the
individual masks may provide. Instead of hav 70 pointsat which this virtual image is formed in
ing the masks slid into position in the holder
di?erent positions of the ball along the race will
individually as shown, a series of them may be
de?ne a locus‘ which is a curved path concentric
disposed upon a rotatablbe disk so that the de
to the ball race and spaced ‘above said race by a
distance equal to approximately three-fourths of
tating the disk, as shown in Fig. 5. As shown, 75 the diameter of the ball. If the focal length of
sired one may be brought into position by ro
2,410,007
the lens l6, twice traversed, is equal to the radius
per se will be designated by the same reference
of the locus of the virtual image formed by re
characters as in the ?rst embodiment.
?ection in the ball and if the lens I6 be located
According to this embodiment of the invention,
at the center of curvature of said locus, the image
the arti?cial horizon includes two separate roll
of the mark will appear in the focal plane of the 6 ing balls each limited to movement in one plane
' object being sighted upon, or at in?nity in this
only. One moves in a vertical plane parallel to,
instance, at all times.
or containing, the viewpoint of the instrument
Referring to Fig. 1, it will be noticed that when
' and the object being sighted upon; and the other
the instrument is in an absolutely horizontal po
in a vertical plane at right angles to this. The
sition the ball will be centered on the rolling 10 ?rst, is optically linked with the ?eld of- view
surface and the re?ected axial ray of the ?du
so that a horizontal line movable up and down
cial mark will strike the top of the ball and lie
is seen by the observer at in?nity in the present
on the radius of curvature of the race passing
sextant, or in the focal plane of an objective
through the center of the'ball so that the horizon
if one is used in the instrument; and the second
will appear exactly at the center of the ?eldof 15 causes a similar but vertical line to appear in'
view. However, when the instrument is tilted, the
the ?eld of view. When the instrument is held
object being sighted upon will move across the
steady, the point of intersection appears ?xed
?eld and so will the image of the ?ducial mark. ,
in the ?eld of view. ‘Usually, since a sextant is
In order to make the image‘ of the object sighted
held in the hand upon moving platforms, the
upon and the image of the ?ducial mark move 20 lines move back and forth over the ?eld, and
in unison across the ?eld of view as the instru
insofar as the observer is concerned, it is the
_ ment is tilted, the optical distance between the
point of intersection that appears to move.
?ducial mark and the point on the sphere where
The. main advantage when using two separate
the radius of curvature of the race passing
rolling balls, instead of one, lies in the fact that
~ through the center of the ball enters the re?ect 25 each ball, being con?ned to movement in one
ing portion of the sphere, is substantially equal
plane only, can move in a race in the form of a
to the radius of curvature of the path of said
V-groove (or ‘between two rails) so that spin
point of entrance. In other words, with the parts
is no longer possible, and at the same time any
in the relative ,positions shown in Fig. 3, the ra
dirt that might collect falls down between the
diusof curvature'of the race passing throughthe 30 guides out of harm's way.
center of the ball enters the ball at the top or
As shown in Fig. 4, each ball 36 and 31 rolls
along its own arcuate V-groove race. Each of
at the point 11:. Now the optical distance a+b
between the mark and this point of entrance is
these races would be preferably sealed in a cham
made equal to the radius of curvature of the locus
ber ?lled with a suitable fluid for damping the
or path de?ned by this point of entrance as the 35 movements of the ball, as in the embodiment de
ball rolls along the race. When the locus of
the point of entrance is referred to, I do not in
fer that the point ‘x rolls around with the ball,
scribed above, but for sake of clarity this added
structure has been omitted. The ball 31 con
trols the horizontal lines and the ball 36 the
but I mean that for every position of the ball
vertical lines of the horizon pattern, by virtue
on the race the ‘radius of curvature of the race
of the optical means to be explained. The ball 31
containing the center of the ball ‘will enter the
ball at a given point and the locus of these re
rolls (in the plane of the drawings) within the
spective points of entrance will be a curved path
concentric to the ‘race.
There may be some instances where arti?cial’
horizons of the type including the ball rolling
on a spherical concave race-might be objected
arcuate V-groove race 39 along two curved lines
of contact 40. The curvature of the path is ?xed
according to the sensitivity required and is tied
up with the optical constants of the system. The
ball 36 controls the vertical line and rolls in a
similar arcuate V-groove race (shownendwise in
to for- the reason that the spinning of the ball
section) the two curved’ lines of contact being
would not be sufficiently damped to allow the
indicated at 4|. The radius of curvature of the
ball to come to rest at the lowest position on 50 two ball races is the same for the type of instru
the race,‘and that this would introduce error.
ment illustrated, but, as will be explained later,
Another objection which might be raised in such
these radii may differ in modi?ed forms‘of the
apparatus.
an instrument is that the collection of dirt at
the lowest point on the race would prevent free
In Fig. 4 there is shown three separate optical
rolling of the ball. Although the second objec 55 systems linked together so that the celestial
tion does not appear to be a serious one, for it
object being viewed is seen on an eye-piece at the
would be possible to construct a sealed chamber
same time as the horizontal and vertical ?ducial
that would remain free from dirt, the ?rst ob
lines, everything being simultaneously in focus
jection is more important, and the eifect might
(i. e., appearing at in?nity) and both lines and
well prove to be serious in practice on airplanes 60 object moving across the ?eld in the same direc
and ships due to violent pitching, rolling and
tion and atthe same rate whenever the instru
yawing.
'
ment is tilted through a small angle.
In Fig. 4 I have shown an arti?cial horizon,
Referring now to Fig. 4, rays from the celestial
including rolling balls, which is entirely free of
object l3 are received by the adjustable index mir
the two objections mentioned and which has the
ror I 2 which re?ects them to the ?xed mirror I I
whence they are reflected to the viewpoint after
added advantage that the arti?cial horizon can
they have traversed the transparent re?ector l4. .
be a composite pattern of individual v?ducial
These rays are shown in full line. All parts shown
marks which are capable of individual adjust-3
in Fig. 4, including an index mirror l2, which is
. ment as the instrument is tilted. For purposes
70 rotatable about an axis perpendicular to the plane
of disclosure, this embodiment of arti?cial hori
in ‘the drawings (but excepting the rolling balls
36
and 31), are ?xed relatively to the sextant
type described above, although it is not limited
frame i0 and, hence, move whenever it is moved.
to use with such an instrument; and accord
ingly, the corresponding parts of the sextant 75 The second optical system is that concerned
with the horizontal ?ducial line. The rays be
zon is shown in association with a sextant of the
asides-2"
:17
6
longing to this system are shown in broken dot
and dash lines. A narrow slit 42 in an opaque
mark 5! always appears at the center of curva
ture of said path. As before, a virtual image of
mask 43 and running perpendicular to the plane
?ected upwardly through transparent re?ector 55
to the mirror 56, thence, to the transparent‘ mir
of the drawing is illuminated through a diffusing
plate 49 by a lamp 44. Rays from slit 42 are
5| is formed in the ball and the rays are re=
ror 48 and up to the'plate I4 to the lens-re?ector
received by the polished metal ball 31 after re?ec
combination 15. The optical distance from the
tion from the semi-transparent mirror 45 and
virtual image in the ball 36 is made equal to the
other mirrors 46 and 41. In practice, the actual
focal length of the lens it, twice traversed, so that
method. adopted to bring the rays around from
parallel rays ?nally emerge at the viewpoint and
10
slit 42 to re?ector 45 and ball 31 would depend
as before ?ducial mark 5|,moves in unison with
upon the space available and the disposition of
any movements of , the object i3 being observed.
the instrument. As in the previously described \ Hence,'the intersection point of the images of the
embodiment, the optical distance from the slit
?ducial marks 42 and 5| always move in unison
42 to the point on the reflecting portion of- the
with the image of the object being sighted upon
15
ball at which a radius of curvature of_ the race
39 containing the center of the ball enters the
ball surface is equal to the radius of curvature of
and all that is necessary is to rotate the index -
mirror 12 until coincidence is obtained.
Inasmuch as the lines of rolling contact between
the locus, or curved path, of said imaginary points
the balls and their races are spaced above the
of entrance. Thus the slit 42 is, in effect, always
bottom of the groove, any dirt that might tend to
at the center of curvature of the path~of the vir 20 collect in the groove would fall to the- vertex there
tual image in the ball surface whatever. the ball’s
of'and not collect on the points of the grooved
position.
walls where they would impede free rolling con
The highly polished ball 3‘? acting as a convex
tact of the ball. As shown, the bottom of the ball
mirror re?ects the rays up through the half
races 38 and 39 may be provided with a channel
transparent mirror 45 and another similar mir 25 60 running lengthwise of the race. This channel
ror 48, then through the glass plate H to the
will serve to collect any foreign matter which
\
mirror-lens
combination l5. The focal length I
might tend to collect on the guiding ‘surfaces of
of the lens it, twice traversed, is equal to the ra-‘
dius of curvature of the path of the virtual image
_ the race so that such foreign matter will not im
pede the free rolling of the ball.
of 42 as seen in 31 and the lens i6 is positioned 30
In this embodiment of the invention, a single
at the center of curvature of said path, so that
lamp 44 and a single lens-mirror combination I5
rays diverging from the ball-mirror 37 to the lens
has been utilized. With other embodiments, the
mirror combination are thereby rendered par
two optical systems—-that for the horizontal ?du-'
allel to each other and these rays are reflected by
cial mark and that for the vertical-—may be quite
35
plate l4 to the viewpoint of the instrument. An
independent. The onlyadvantage in such a mod
image of the horizontal slit 42 is,v,therefore, seen
i?cation is the possibility of making the sensitiv
at in?nity. Slight rotations of the instrument as
ities diiferent for the two systems,’ the horizontal
a whole about an‘ axis perpendicular to the plane
being more sensitive than the vertical. The main _
of the drawing, cause the ball 31 to roll along
disadvantage is that the introduction of ‘two re
its race 39 and, hence, the image of 42 appears to 40 fiectors such as plate l4 in the light path would
move in the field of view. However, owing to the
involve a loss of about 10 per cent of the inci
speci?ed relationship between the curvature, the
dent light from the star instead of only 5 per
focal length, and the optical distances, this movecent. This loss of light is an important factor in
ment is in the same direction, and at exactly the
a sextant where the object sighted upon is a faint
same rate as the movement of the image of the
star, but when sighting on the moon or sun with
object (e. g., star) across the field of view, so ‘
a sextant, or when using instruments which are
that coincidencernay be obtained in any part of
used to sight objects which are well illuminated,
the ?eld.
this loss of light due to the inclined plate 54 is not
The third optical system, whose rays are shown
so important.
50
in simple broken lines. concerns the vertical ?du
From the above description it is believed that
- cial line. This ?ducial line may conveniently take
the form of two parallel lines a few minutes of arc
> those skilled in the art will appreciate the fact
that an arti?cial horizon constructed in accord
apart (as seen in the eye-piece), since small
ance with the present invention overcomes many
errors in obtaining coincidence with the vertical
long standing disadvantages possessed by ordi
line are of no consequence. Coincidence with the .55_ nary bubble levels, and possesses many advan
horizontal line may then be obtained with the
tages over known arti?cial horizons, In the ?rst
celestial body anywhere between the two vertical
place, the size of the image of the ?ducial mark,
lines. This simpli?es the problem of holding the
or pattern, constituting the horizon is not varied
instrument steady. The third optical system is
by changes in temperature as is the size of the
60
exactly similar to the second optical system pre
bubbles in ordinary levels. In the second place,
viously described. An opaque mask 50 is provided
the shape and size of the horizon may be altered
with a vertical transparent slit 5! (or pair of
without changing the sensitivity of the device, or
parallel slits) in the plane of the drawing, and
vice versa. This could not be done with ordinary
which slit is illuminated by the lamp 44 through
bubble levels. Thirdly, the con?guration and size
a diffusing plate 52. The rays after re?ection 05 of image of the ?ducial marks may be readily
from mirrors 53 and 54 are received by the half
changed in accordance with the type of object be
transparent mirror 55 from which they are re
ing sighted upon, and for the purpose of facilitate
?ected to the re?ecting surface of the ball 35.‘
ing bringing the image of the object and ?ducial
As before, the optical distance between the slit
5| and the point on the surface of the ball at 70 mark into coincidence.
Although Ihave shown and described certain
which the radius of curvature of the race 38 con-,
speci?c ‘embodiments of my invention, I am fully
taining the center of the ball enters the ball sur
face, is equal to the radius of curvature of the ~ aware that many modi?cations thereof are pos
sible. My invention, therefore, is not to be re
path of said point of entrance in the ball as the
latter rolls along the race so that the ?ducial 76 stricted to the precise details of construction
2,410,667
10
shown and described, but is intended to cover all
modi?cations coming within the scope of the ap
pended claims.
being spherically concaved to provide a rolling
surface, a sphere in said chamber in rolling con
tact with the bottom thereof and having a re
‘
Having thus described my invention, what I
claim as new and desire to secure by Letters Pat
ent of the United States is:
1. An arti?cial horizon for use with a movable
' sighting instrument including a sight axis and
?ecting surface, the top of said chamber includ
ing a window of transparent material extending
over the range of possible movement of said
sphere, a damping ?uid in said chamber and im
mersing said sphere. the material forming the
window and the damping ?uid having substan
comprising an arcuate ball race ?xed to the in
strument to move therewith and disposed so that 10 tially the same index of refraction, an illumi
a chord of said race lies in a vertical plane which » nated target bearing suitable ?ducial marks ?xed
is parallel to the sight axis, a ball having a re
to the instrument to move therewith and spaced
?ecting surface in rolling contact with said race
from said chamber, and means including said
optical system for projecting an image of said
and con?ned thereby to move in a curved path,
a target ?xed to said instrument to move there 15 targetthrough said window and onto the top oi’v ' '
with, means ?xed to the instrument to move
said sphere,and for directing the image re?ected
therewith for projecting an image of said target
from the surface of said sphere to the viewpoint,
onto the uppermost portion of the surface of said
the curvature of said rolling surface being such
ball and-for directing the target image re?ected
in relation to said optical system that the image
from the surface of said ball along the sight axis 20 of the target and the image of the object being
of .the instrument to the viewing point and con
sighted upon will move in unison across the ?eld
of view as the instrument as a whole is moved
stitute the horizon, the curvature of said ball race
being such that the image of ‘the target and the
about any horizontal axis intersecting the vertical
image of the object being sighted upon will move
plane containing a .chord of said race.
8. An artificial horizon according to claim 7
in unison across the ?eld of view as the instru 25
ment as a whole is- moved about any axis inter
secting a vertical plane containing a chord of
said race.
'
.
-
_
- in which the underside of the top of the enclosed
chamber is provided with an expansion recess
which is outside of the normal range of move
ment of the sphere and which is not ?lled with
2. An arti?cial horizonsaccording to claim 1 in
which the target comprises a member spaced from 30 the damping ?uid, said expansion recess account
ing for expansion of the ?uid due to temperature
said ball and bearing a suitable ?ducial mark,
changes and for trapping any air bubbles which
means for illuminating said mark, and means for
might occur in the ?uid.
.
_
‘
directing an image of said mark upon the upper
most portion of the surface of said ball.
9. An arti?cial horizontal according to claim
3. An arti?cial horizon according to claim 1 in 35 '7 in‘ which the enclosed chamber is composed
which the target comprises a mask provided with
in its entirety of a transparent material having a
a transparent opening, means for diffusely illu
refractive index substantially the same as that
minating said opening and means for projecting
of the damping ?uid, contained therein, the bot
an image of said opening upon the uppermost
tom wall of said chamber being non-re?ecting
and non-transmitting with regards to light.
Portion of the ball.
'
4. An arti?cial horizon according to claim
10. An arti?cial horizon'for use in combination
1 in which the target comprises a member bear
with a sighting instrument including a sight axis
‘ing a suitable ?ducial mark, means for illuminat
and an optical system for projecting the image of
ing said mark, and means for projecting an image
a ?ducial mark to the viewpoint which is to indi
of said mark upon the uppermost portion of the 45 cate thehorizon, and comprising in combination ,
surf-ace of the ball, the parts being so arranged
a pair of arcuate ball races ?xed to the instru
that the optical distance between the ?ducial
ment to move therewith, and oriented with re
mark and the point on the ball where a radius of
spect to one another so that the chord of one
curvature of the race, passing through the center
race is substantially in a plane parallel to a ver
of the ball, enters the re?ecting portion of the 50 tical plane including the sight axis of the instru
ball is substantially equal to the radius of curva
ment, and the chord of the other race is at an
ture of the locus de?ned f by the path of said
angle to the chord of said ?rst mentioned race, a
point of entrance as the ball rolls along said race.
ball having a polished re?ecting surface in roll
5. An ‘arti?cial horizon according to claim
ing contact with each race; a pair of ?ducial lines
1 in which the target comprises a member spaced
?xed to said instrument in spaced relation, one
, above and to one side of the ball and bearing a
of said ?ducial lines being normally horizontal
suitable ?ducial mark, means for illuminating
and perpendicular to the plane of the ?rst ball _
said mark, and in which the means for project
race, the other of said ?ducial lines being nor
ing an image of said marks on the surface of
mally vertical and parallel to the plane of the
said ball comprises a transparent re?ecting plate 60 ?rst ball race; means for projecting an image of
inclined to the radii of curvature of said ball race.
each one of the ?ducial lines onto different ones
6. An arti?cial horizon according to claim 1
of said balls; and means for projecting the images
in which the target comprises a plurality of in
' of said ?ducial lines from the individual balls
dividual ?ducial marks which are so mounted
into said optical system in intersecting relation
on the instrument that they can be interchange
ship .to provide a horizon, the curvature of said
ably positioned in operative relationship with
ball races being such that the point of intersec
the means for projecting their image onto the
tion of the images of said ?ducial lines and the
‘image of the object being sighted upon will move
ball.
.
_
7. An arti?cial horizon for use with a sighting
in unison across the .?eld of view as the instru
instrument including a ‘sight axis and an optical 70 ment as a whole is rotated about any horizontal
system for projecting?the image of a ?ducial
axis perpendicular to the plane of said ball races
mark to the-viewpoint and which mark is to in
and any horizontal axis parallel to the planes
dicate the horizon, and’ comprising in combina
containing said ?rst mentioned horizontal axes.
tion an enclosed chamber ?xed to the instrument
11. An arti?cial horizon according to claim 10 '
to move therewith, the bottom of said chamber 75 in. which the optical distance from the individual
9,410,687?’
?ducial lines to ‘the point on the surface of the
hall where a radius of curvature of the race, pass
ing through the center'of the ball, enters the re—
the instrument, of an artificial horizon compris
ing an arcuate ball race attached to the instru
?eeting portion of the ball is substantially equal
to the radius of curvature of the locus de?ned by
the path of said point of entrance as the ball rolls
in rolling engagement with said race and having
ment so that a chord of the race is substantially
horizontal when the instrument is in use, a ball
a re?ecting surface, an illuminated ?ducial mark
attached to said instrument, and optical means
for directing an image of said mark to the upper
12. An arti?cial horizon according to claim 10
most ‘portion of the surface or said ball from
in which the ball races are V-grooves the bottom
of which is provided with an elongated recess 10 which it is in turn directed to said secondary op
tical system, the curvature of said race being.
running lengthwise of the groove and extending
such that the image of the ?ducial mark re?ect
below the vertex of the groove.
ed by said ball and the image of the object being
13. An arti?cial horizon according to claim 10
along said 18.90.
sighted upon will move in unison across the ?eld
in which said races are oriented so that the chord
of one is substantially horizontal and lies in a 15 of view as the instrument as a whole is moved
about ‘any horizontal aids intersecting a- vertical
vertical plane containing the sight axis of the
plane‘containing a chord of said race.
instrument, and the other race is horizontal and
16. An instrument according to claim 15 in
extends at right angles to the ?rst mentioned
which the optical distance between said ?ducial
race, a mask having a horizontal slit, a mask
having a vertical slit, means for diffusely illumi 20 mark and the point on the ball where a radius of
curvature of the race, passing through the cen
hating each or said slits whereby they constitute
ter of the ball, enters the re?ecting portion of
?ducial lines, an optical system for projecting an
the ball is substantially equal to the radius of
image of the horizontal slit onto the ?rst men
curvature of the locus de?ned by the path of said
tioned ball, a second optical system for project
point of entrance as the ball rolls along said race.
ing an image of the vertical slit onto the second
17. In-an instrument for determining the hori
mentioned ball, and means for directing said two
images into said optical system of the instrument
zontal direction in relation to a point of observa
tion'the combination with a primary optical sys
in combined relation so that they form an arti
tem for directing an image of the objected sight
?cial horizon in the-form of a cross the two ele
ments of which are individually movable rela-, 30 upon to a viewpoint, a secondary optical system
associated with said primary system to direct an
tive one to the other.
_
image of an arti?cial horizon into and along the
14. An arti?cial horizon for use with a sighting
sight axis to the viewpoint, said secondary sys- ‘
instrument and comprising in combination‘ a Q
tem including a transparent re?ector cutting
rolling sphere having a re?ecting surface,v an
arcuate race for supporting ‘said sphere, in roll 35 across said' sight axis and inclined thereto, a
re?ector lens combination located vertically
ing contact therewith, said race being attached
to said instrument in ?xed relation thereto so 1 above said transparent re?ector and adapted to
receive diverging image forming rays passing ~
that a chord of the race is substantially horizon
through said re?ector and to return them to the
tal when the instrument is in use, a ?ducial mark
?xed to said instrument to move therewith, means 40 upper surface thereof in collimated form, of an
connected to said instrument for projecting an
arti?cial horizon comprising an arcuate ball race
fastened to the instrument and located below the
image of said ?ducial mark onto the surface of
sight axis thereof in optical alignment with said
said sphere, means for directing the image of said
mark in the sphere to the sight axisof the in
re?ector-lens combination, a ball in rolling en- '
‘ strument, the curvature of said race, being such 45 gagement with said race and having a, re?ecting
surface, a ?ducial mark ?xed to said instrument
that the image of the ?ducial mark and the image
to move therewith, means connected to said in
of the object being sighted upon will move in
strument for directing an image of said ?ducial
unison across the ?eld of view as the instrument
mark onto the upper surface-of said ball and
as a whole is moved about any horizontal axis
which image is re?ected to said re?ector lens
intersecting the vertical plane containing a
combination and in turn by said transparent re
chord of said race.
?ector to the viewpoint of the instrument, the
15. In an instrument for determining the hori
radius of curvatureof said race being equal to the
zontal direction in relation to a point of observa
focal length of said lens of said re?ector-lens
tion the combination with a primary optical sys
combination so that the image of the ?ducial
tem for directing an image of the object sighted
upon to arviewpoint, a secondary optical sys
mark will appear at in?nity and will move in
tem associated with said primary optical system ' unison across the ?eld of view with. the image of
the object being sighted upon as the instrument
to direct an image of an arti?cial horizon to said
as a whole is moved about any horizontal axis
viewpoint where it is viewed simultaneously with
the object being sighted upon, said secondary QD-_ 60 intersecting a vertical plane containing a chord '
tical system including a transparent re?ector at
of said race.
BENJAMIN E. LUBOSHEZ.
an angle to and cutting across the sight axis of
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