A Distance Measurer.
Year: 1889

page_text: Date of Application, 19th Feb., 1889
Complete Specification Left, 19th Nov., 1889-Accepted, 21st Dec., 1889
PROVISIONAL SPECIFICATION.
A Distance Measurer.
I JOHN PHILIP NOLAN, of 34 Half Moon Street Piccadilly my temporary address
and of Ballenderry Tuam my permanent address, Lieutenant Colonel Retired do
hereby declare the nature of this invention to be as follows:-
My invention is an instrument for rapidly measuring distances; the instrument
consists of a double telescope and of a detached prism and of a base fit to receive
these at either end but the base need not necessarily be special and may be some
article in common use. The double telescope is composed of two telescopes giving
real images and of a prism.
The telescopes should be soldered or joined together with the axii parallel these
axii should be at such a distance apart that when the right eye of a man looks into
the right telescope his left eye can look into the left telescope, a prism is placed in
front of the object glass of one telescope (say the left) and it is best to fasten it
permanently to this telescope.
In the focus of one telescope (say the right) is a scale j in the focus of the other
(the left) is a screwing needle.
The whole double telescope including its attached prism is mounted on three
springs, compressed by three screws which give the double telescope motion in every
direction.
Attached to this double telescope, there is also a slide or other fixture which
renders the double telescope capable of being attached to one end (say the right) of
the base.
The detached prism is mounted on two springs with a similar slide attachment.
Both prisms are made with six sides (including the top & bottom) though if the
long angle is cut off there are seven sides without any optical change.
Two sides of each prism are made smooth & left plain these two sides are at right
angles to each other."
Two other sides or faces are cut at an angle of forty five degrees to each other
and coated with reflecting metal.
The top & bottom sides or faces may be left rough.
Each prism trends light through a right angle (or so reflects it).
One plain face of the detached prism faces an object viewed; the other plain
face faces the telescope prism.
One plain face of the telescope prism faces the detached prism the other looks into
its telescope.
The base may be any bar tube or rifle but is sensibly longer than the distance
between the axii of the two telescopes of the double telescope.
It may have fittings to receive the double telescope & the detached prism at
either end.
Opera glasses & other glasses of the Galilean description do not give real images
so are excluded from this invention.
The needle has a male screw cut round a part of it, so that the needle can be
screwed into a fixture in (say) the left telescope; the point of the needle is in the
focus of this telescope.
The needle may be replaced by a web or wire but not with advantage.
The scale is marked on glass.
The formula for marking the scale is
Distance is to optical base as the optical focal length of scale telescope is to the
interval, seperating the mark on the scale-representing the distance-from the
G. 1:.
the souls

page_text: HE IS te maTK ON The scale representing 400 yards should be marked at one
fortieth of an inch from the infinity line on the scale.
The instrument is set true, by bringing one image of an object on the point of the
needle and the other image of the same object on its distance mark on the scale
(the distance of the object having previously been carefully measured) and the
needle being screwed until this is possible.
Observations are taken, by resting the instrument on a support, then making the
faces of the prisms parallel and opposite to each other-that is the opposing faces
of the two prisms-and by bringing one image of an object on the point of the
needle and the other image on the vertical centre of the scale, both being effected
with the aid of the five spring adjusting screws.
Then the needle is pointed on an object (by moving the whole instrument) and the
second image of this object will appear on the scale at the place corresponding to
its actual distance that is the true distance of the object.
One eye (say the left) is used to point the needle one eye (say the right) to read
the distance.
Vision of the two images of the same object may be obtained according to light
and other circumstances either simultaneously with the two eyes or in rapid alterna-
tion of the eyes by winking or closing one eye at a time.
The optical base is the distance from the axis of the direct telescope to the centre
of the detached prism.
Dated this Nineteenth day of February 1889.
"
COMPLETE SPECIFICATION.
A Distance Measurer.
I JOHN PHILIP NOLAN of Ballenderry Tuam Ireland, Lieutenant Colonel Retired,
do hereby declare the nature of this invention and in what manner the same is to
be performed to be particularly described and ascertained in and by the following
stateinent:-
"
My Invention has for its object to provide an apparatus for measuring distance in
a reliable and accurate manner, the said apparatus being simple in construction and
capable of being, used with facility.
I employ a telescope fitted with a glass prism and constructed as hereinafter
described. This telescope is placed at one end of a bar or rod constituting what is
hereinafter referred to as a base," at the opposite end of which base is placed a
glass prism of the same form as the prism of the double telescope. A special base
may be provided or it may be constituted by any convenient article in common use
but, it must be so placed that when in use the double telescope and the separate prism
lie in the same plane, and the distance between the double telescope and the said
separate prism must be sensibly greater than the distance between the eyes of the
observer. The double telescope consists of two single telescopes giving real images,
the said telescopes being fixed together with their axes parallel to each other and at
such a distance apart that the eyes of the observer may look simultaneously into both
the, telescopes.
1
Permanently secured in front of the object glass of one of the two telescopes is a
prism of similar form to that of the separate prism and in the focus of this

page_text: telescope is the end of a pointer or needle which is adjustable radially at right
angles to the optical axis of the telescope. Cross wires may be substituted for the
needle if desired but the use of a needle is preferable.
In the focus of the other telescope is a glass plate having a scale of distances
marked in any convenient manner upon it.
Each of the two prisms hereinbefore referred to is arranged to reflect a ray of light
through a right angle.
In order that my Invention and the way in which it may be carried out in
practice may be clearly understood, I will now proceed to describe the same 'with
reference to the accompanying Drawings wherein Figure 1 is a plan and side
elevation of one of the two similar prisms. Figure 2 is a diagram for explaining
the principle of the instrument. Figure 3 is a sectional plan of the double telescope
with a side elevation of the prism. Figure 4 is a side elevation of the same with its
supports. Figure 5 is an end view of the supports. Figure 6 is an underside view
of a portion of Figure 4. Figure 7 is a side clevation and Figure 8 a plan of the
separate prism and its supports and Figures 9 and 10 shew in plan and in end
elevation respectively a guide or holder adapted to receive either the double telescope
or the detached prisun, one of these guides or holders being fixed at each end of the
"base."
Referring to Figure 1, it will be seen that the prisms are formed with two
adjacent sides, A B B C, at right angles to one another, the remaining
sides Ad D, CD, making each an angle of 112° with the sides A, B, and
B, C, respectively, the angle A DC being therefore 45°. For convenience in
mounting the portion d Dc of the prism shewn in dotted lines may be removed
without producing any optical change in the prism as far as its applicability
to this Instrument is concerned.
•
The sides A B B C, are ground smooth and polished and the sides A d'and Cc,
are prepared in the same way and covered with a reflecting metal. The side'd, c,
and the remaining surfaces at top and bottom of the prism may be left rough. Any
rays of light entering the prism through either of its sides A B B C, as indicated
in dot and pick lines at any angle thereto within certain limits will be reflected so
that the reflected ray will leave the prism through the other smooth side at right
angles to the direction of the entering ray as shewn by the dot and_pick_lines__
Referring now to Figure 2, the one prism (1,) is placed at one end of the
base 1, 2, and the similar prism (2,) is affixed to one of the tubes 8, of the double
telescope 8, 9, (Figure 3). It is intended that one plain side of the separate
prism 1, should face the object viewed, the other plain side facing and being
parallel to one of the plain sides of the prism 2,.attached to the double telescope, the
other plain side of the prism 2 heing viewed through the telescope. 8. The con-
struction and arrangement of the double telescope are illustrated in Figures 3 and 4,
wherein 8 and 9 are the two telescopes, 2 is the prism, 3 the lenses of the telescopes,
4 the needle which lies horizontally and is formed with a screw thread and a square
head 5 so that it may be adjusted (at right angles to the optical axis) in the boss 6
on the exterior of the telescope 8 which boss is so formed as to protect the needle
from accidental blows, the small set screw 31 being for the purpose of retaining the
needle in its adjusted position. 7 is the glass plate fixed in tlie. telescope 9 and
carrying the scale of distances before referred to, which scale may be cut or otherwise
marked horizontally across the glass in any usual or convenient way. The two
telescopes 8, 9, are connected together by the bars 10 and are carried by the
bearers 11, which are attached to a spring 12. The spring 12 is bent at 13 as shewn
in Figure 4, and bent again at 14 as is shewn more clearly in Figure 5, and is
secured by screws to an enlargement 15 upon the middle arm 16 of the support 17
which is received in a guide or holder 18. The screw 19 (having a handle 20)
bears upon the spring 12 at 21 and is screwed into or out from a hole in the piece 15
so that it may draw the portion 21 of the spring towards the support 17 or permit
it to move away therefrom and so cause the two telescopes to receive a small amount
of rotation, about an imaginary-axis lying below and parallel with them. A screw 22

page_text: acts, upon the portions 21, 23 of the spring 12 and by drawing them together or
permitting them to move apart gives the two telescopes movement in a vertical
plane, about an imaginary horizontal axis lying near 13. A third screw 24 is
screwed into the armi 25 of the support 17, (Figure 6) and acts upon the spring
arm 16, moving the free end of that arm horizontally to the right or left upon a
guide pin 26, and as the telescopes are carried by the spring 12 secured to the
enlargement 15
upon the
arm, they receive rotation in the horizontal plane about an
imaginary vertical axis near to 27. By these means, the double telescope may receive
the necessary movements as hereinafter described.
The support 17 has attached thereto a spring 28 with a projection 29 thereupon,
which projection, when the support is placed in the guide or holder 18, (Figures 9
and 10) engages with a recess 30 therein and ensures the support, taking up a proper
position.
The separate prism (Figures 7 and 8) is carried by and in supports and guides
similar to those of the telescope except that the prism is adjustable laterally and also
about a horizontal axis parallel with the centre bar 16 of its support and not about a
horizontal axis at right angles thereto, the last mentioned adjustment being required
only by the telescopes.
The screws 19, 22, 24 are for adjustments made by the maker of the instrument,
and will not require to be operated by the user of the instrument except for such
small re-adjustment as may be rendered necessary by the straining of the apparatus
or other accidental causes.
The sides A B, of each of the prisms 1 and 2, should be so mounted with relation
to their supports by the maker of the instrument that only a small if any further
adjustment by the screws, is needed to bring these faces of the prisms parallel to one
another.
The scale hereinbefore referred to is cut on glass or photographed on glass from
a drawing.
The formula used in graduating the scale is :—

page_text: and then turning the screw 24 until the vertical centre of the scale and the point of
needle are both on the object.
The detached prism can be adjusted sufficiently square by operating its screws 22 24
and looking along its outside edges until it is obviously opposite the telescope prism
or this adjustment may be tested more neatly by putting a candle opposite the eye
picce of the prism telescope and observing that the reflected candle light from the
detached prisim is thrown towards the centre of the telescope prism.
The telescope prism may be adjusted sufficiently nearly parallel (the instrument
being levelled) by pointing the whole instrument at the roof of a house and observing
that when the scale and needle are both on the ridge of the roof the ridge will also
appear in the detached prism half way up the vertical height of the said prism when
the eye of the observer is placed just in front of the telescope prism at its vertical
centre.
Similarly when the eye is placed above the telescope prism 2 over the vertical
centre line of the side which is opposed to the detached prism the edge of a house
should lie upon the vertical centre line of the opposed side of the detached prism
if the scale and needle are both pointing at the edge of the house.
There are however numerous other well known ways of ensuring that the prisms
are opposite and parallel to each other. Absolutely perfect paralellism is not
essential to fairly accurate observation.
The principle of the apparatus may now be understood by reference to the
diagram Figure 2 in which 0 is the object at a distance O. 1 from the end of the
base 1, 9 the length of .the base being the distance between the centre of the object
glass of the direct telescope 9 and the centre of the detached prism 1. 7 is the scale
glass of the telescope 9 and 0 1, 2, 3 is the path of the rays from the object ()
when the prisms are adjusted parallel in the manner hereinbefore described.
It is evident that if the prisms 1, 2 have their opposing faces truly parallel and
their centres in the same plane the rays of light from the object 0 will be in the
focus of the telescope 8 but the rays from the same object passing into the companion
telescope 9 will give an image on the scale therein at a point 4.
The scale 7 and the image of any object viewed through the telescope
also the
reflected image and the point of the needle in the telescope 8 may be seen either
simultaneously by both eyes of the observer or else in succession by rapidly
winking or opening and closing one eye at a time according to light and other
circumstances.
It may be seen that the distance 10, 4 upon the scale glass 7 bears a ratio to the
optical base 1, 9 which is the same as the ratio between the distance 10, 9 (measured
between the scale glass 7 of the telescope 9 and its object glass) and the unknown
distance of the object 0 from the end 1 of the base, for the triangles 190 and 10, 4, 9
are similar provided that the scale telescope 9 is a simple telescope but if it is a
compound telescope (that is a telescope with a concave lens between the object, glass
and the scale) then the optical focal length of the telescope is substituted for the
actual length 10, 9 in calculations for making the scale.
The point 10 upon the scale 7 is that upon which when the instrument is set
the scale telescope image of an object at an infinite distance would fall when the
point of the needle touches the prism image of the object and this point is marked,
the mark being known as the "infinity mark." The graduations for finite distances
upon the scale will be separated from the infinity mark by intervals varying inversely
with the distances of the objects from the prism 1 and directly with the optical base
and with the optical focal length of the scale telescope.
To set the instrument, the maker by means of the screws 19, 22, 24 places the
prisms 1 and 2 parallel to one another and then choosing an object at a known
distance say 1200 yards for example, moves the base of the instrument until the
image of the object rests upon the 1200 yards mark upon the scale, by this means
the reflected image in the prism telescope will be caused to lie in the optical focus of
that telescope and the needle should be screwed in or out until its point touches

page_text: the said image when the small screw 31 should be screwed in to lock the needle 4
permanently in place.
To use the instrument the operator need only move the base until the image of the
object whose distance he desires to ascertain is brought to the point of the needle 4
in the telescope 8 by which time another image of the object will appear upon the
scale 7 in the other telescope 9 at a graduation which shall indicate the true distance
of the object from the prism 1. An important feature of the apparatus is that the
observer uses both eyes in the manner hereinbefore stated in looking at the two images
and he has no need to move his head, any movement of which would prevent steadiness
and cause inaccuracy.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what I
claim is
First. In instruments for measuring distances a double or binocular telescope
consisting of two telescopes connected together parallel with each other and giving
real images one of the said telescopes being fitted with a prism and a needle or its
equivalent and the other telescope having a scale of distances the whole being for use
in combination with a separate prism mounted on a base at a distance from the
telescope prism which is sensibly greater than the distance between the eye pieces
of the telescopes substantially as herein before described with reference to the
accompanying drawings.
Second. In instruments for measuring distances supports for the adjustment of
telescopes or of prisms the said supports being constructed and arranged substantially
as hereinbefore described and illustrated in Figures 4, 5, 6, 7 and 8 of the accom-
panying drawings.
Third. The combination and arrangement of parts constituting an apparatus or
instrument for measuring distances upon the plan explained with reference to the
Figure 2 of the accompanying drawings.
Fourth. The arrangement and combination of parts constituting the measuring
instrument hereinbefore described and shewn in Figures 3 to 10 of the accompanying
drawings.
101 1
1000