A New or Improved Telemeter or Range Finder."
Year: 1897

page_text: "A New or Improved Telemeter or Range Finder."
I, WILLIAM LIONEL WYLLIE A.R.A., of Hoo Lodge, Hoo Saint Werburgh, Near
Rochester, in the County of Kent, do hereby declare the nature of this invention
to be as follows:-
This invention relates to a new or improved telemeter or range finder and has
for its object the production of an instrument not liable to get out of order, more
accurate than those now in use, cheap to manufacture, and above all requiring
no calculation or adjustment, shewing at a glance the desired range, it
fore be used by unskilled persons.
may there-
The following are the principles on which I construct my telemeter or range
finder.
The distance from a given point above the level of the sea to the horizon is a
constant and known quantity and the water line of any object which is visible
will appear to approach the line of the horizon according to its distance from the
observer. Moreover an object of known size will appear smaller in exact propor-
tion in receding from the spectator.
•
In carrying these principles into effect I construct a telescope capable of
holding between the lenses certain glass screens on which are engraved suitable
scales which on looking through the telescope or range finder appear between the
observer and the object or enemy.
For naval use, these screens will be made for certain fixed heights, for instance,
the bridge, and fore top, the person using the finder will make a red line on the
scale coincide with the horizon and read off the distance shown by that line on
the screen which corresponds with the water line of the vessel he is engaging or
other object.
Instead of screens so divided other screens may be inserted shewing the visible
sizes of objects of known dimensions at stated distances, for instance, take the
average height of a soldier, and a scale can be made shewing his apparent size at
distances at 300, 500, 1000, or any number of yards.
When the telemeter or range finder is used from a fort or like structure it will
be possible to mount it on a turn-table fitted with depression ring so as to enable
it to be used even when the horizon is obscured by fog or darkness.

page_text: "A New or Improved Telemeter or Range Finder."
I, WILLIAM LIONEL WYLLIE A.R.A., of Hoo Lodge, Hoo Saint Werburgh, near
Rochester in the County of Kent, 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 statement:-
This invention relates to a new or improved telemeter or range finder and has
for its object the production of an instrument not liable to get out of order, more
accurate than those now in use, cheap to manufacture, and above all requiring
no calculation or adjustment, shewing at a glance the desired range; it may there-
fore be used by unskilled persons.
A telemeter or range finder constructed according to this invention consists
essentially of an ordinary terrestial telescope having a specially graduated or
scaled screen interposed between the object glass and the eye piece.
•
In the accompanying drawing which illustrates one form iny invention may
assume:-
Figure 1 is a view in side elevation-partly in section-of an ordinary terrestial
telescope adapted for use as a telemeter or range finder.
Figure 2 is a diagramatic view showing the principle involved in scaling or
graduating the screen, and
Figure 3 is a view of the screen on an enlarged scale.
The principles involved in the construction of a telemeter or range finder
according to this invention are as follows:-
The distance from a given point above the level of the sea to the horizon is a
constant and known quantity and the water line of any object which is visible
appears to approach the line of the horizon according to its distance from the
observer. Also that an object of known size appears smaller in exact proportion
in receding from the observer.
In carrying these principles into effect I construct or adapt an ordinary tele-
scope A in such a manner as to allow a specially scaled or graduated screen B
to be inserted and held between the object glass and the eye piece and also to
provide means whereby the distance between the said screen B and the object
glass is made constant or unalterable. The usual erector or combination of lenses
used in terrestial telescopes for reversing the image is placed either in the eye
piece or between the screen and the object glass. The eye piece is of the usual
construction.
I prefer to so construct my telemeter or range finder that the screen may be readily
inserted, either by forming a slot in the tube as shown on the drawing or by
securing it in place from the eye piece end by a screwed ring in a manner similar
to that employed for securing the lenses in position, so as to allow of differently
marked or graduated screens being employed.
The screen is preferably made of glass but it may be made of other transparent
or semi-transparent material and to ensure the best results should be optically.
worked or have both its surfaces true and parallel with each other.
The scale or divisions 6 marked on the screen as shown in Figure 3 may be
formed thereon in any suitable manner but preferably by means of photography.
The relative positions or the distances apart of these division marks are arrived
at in a manner which will be clear on reference to Figure 2 wherein Y-Z repre-
sents a segment of the earth's surface, X the eye of the observer and X-Z the
horizontal line.
The distance between the eye of the observer X and the earth's surface Y is
equivalent to the height above the level of the sea at which the instrument is

page_text: to be used. If the line Y-Z is now divided into equal divisions say of 1000
yards each as shown, then lines drawn from those points to the eye of the observer
will intersect a radial line x-r, and the points at which these lines intersect will
furnish the data from which the screen may be scaled or graduated. It will be
understood that each division may be subdivided in a similar manner into as
many parts or distances as may be found desirable and also that a separately
scaled or graduated screen is required for each height above sea level at which
the instrument is to be used, for instance in a telemeter for naval use, the height
of the ships bridge above the sea level would be used for determining the scale
of one screen and the height of the conning tower for another screen.
In using this telemeter or range finder the observer makes the top horizontal
line on the screen coincide with the horizon and reads off the distance shown
by that mark or line on the screen which corresponds with the water line of the
vessel or other object whose range or distance he wishes to ascertain. -l'or
instance in Figure 3 of the accompanying drawing the water line of the ironclad C
is shown coinciding with the mark 5000 its range or distance from the observer
is therefore 5000 yds, similarly the cruiser D is at a range or distance of 3500 yds
and so on.
Instead of screens divided in the manner herein before described other screens
may be used for showing the visible sizes of objects of known dimensions at stated
distances, for instance, taking the average height of a man, a scaled screen can
easily be produced showing his apparent size at different distances, for example
at distances of 700, 800 and 1000 yds. Very small angles can also be measured
with great ease if a screen is used marked with degrees, minutes and seconds.
When the telemeter or range finder is used from a fort or like structure it will
be possible to mount it on a turntable fitted with depression ring so as to enable
it to be used even when the horizon is obscured by fog or darkness.
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:-
(1) A telemeter or range finder constructed substantially as herein before,
described and shown.
(2) A telemeter or range finder so constructed or arranged as to embody the
principle that from a given point above sea level to the horizon is a constant and
known quantity and that the water line of any object which is visible appears to
approach the line of the horizon according to its distance from the observer.
(3) A telemeter or range finder so constructed or arranged as to embody the
principle that an object of known size appears smaller in exact proportion in
receding from the observer.
(4) A telemeter or range finder consisting essentially of a telescope having a
specially graduated or scaled screen interposed between the object glass and the
eye piece as set forth.
100X