Improvements in Distance Measuring Instruments or Telemeters.
Year: 1894

page_text: Date of Application, 26th June, 1894
Complete Specification Left. 26th Mar., 1895-Accepted, 26th June, 1895
PROVISIONAL SPECIFICATION.
Improvements in Distance Measuring Instruments or Telemeters.
JAMES HENRY STEWARD 406 Strand London Optician do hereby declare the
nature of this invention to be as follows:-
The adaptation to reflecting instruments of the sextant type of an exact
adjustment for 90 degrees and a movement of the index glass by means of a
cam so shaped that the reflected angles during the movement are less than 90°.
one
The objects of these improvements are first, to permit of two instruments being
used together for the purpose of finding the range of moving objects or
instrument and an optical square, and second for permitting the observer to retire
along the base from the first position and to ensure perfect alignment with the
mark chosen as an extension of the base, the said mark forming an approximate
right angle to the object being measured.
1004
COME LEID
Improvements in Distance Measuring Instruments or Telemeters.
1, JAMES HENRY STEWARD, 406 Strand, London Optician 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 :-
The adaptation to reflecting instruments of the sextant type of an exact
adjustment for 90 degrees and a movement of the index glass by means of a cam
so shaped that the reflected angles during the movement are less than 90°.
The objects of these improvements are first, to permit of two instruments being
used together for the purpose of finding the range or distance of moving objects,
or for one instrument and an optical square to be used together, and second, for
permitting the observer to retire along the base from the first position as hereafter
explained to ensure perfect alignment with the mark chosen as an extension of the
base the said mark forming an approximate right angle with the object being
measured.
In order that this may be better understood I append drawings, first shewing
the instrument in perspective, second, a section of the instrument and the cam
refered to as controlling the index mirror so as to reflect angles less than a right
angle, third, the method of taking moving objects, and fourth that of taking the
distance of a fixed object where the observer retires along a base line. In Fig. 1.
the improved telemeter is shewn as used when making an observation, the index
mirror A is controlled by the cam C. an extension of mount of mirror Q (Fig. 2)
heing kept pressed against it by means of a spring R (Fig. 2) so as to ensure a
movement directly the end of cylinder D is revolved. The horizon mirror B. is con-
trolled by a screw finishing in the cogged head E, and an independent collar Fican
be set to correspond with zero G when the mirrors reflect a right angle, and clamped
by screw H. The shutter is to close the opening where the cam C. Fig. 1 is seen,
when the instrument is not in use. Fig. 2 shews a sectional view of the instrument

page_text: and the line of vision over the two mirrors placed normally at 45° to each other
and another line of vision reflecting a right angle by double reflection from the
mirrors, also Fig. 2 the cam causing them to move through a few degrees of angle
less than 45° and by reflection less than 90: the screw, E reaching to the horizon
glass mount Benables the horizou glass 13 to be moved so that it reflects a few
degrees more or less than a right angle. The lever Q (Fig. 2) connecting the
index glass A to the cam by pressure of spring R bringing pin S (Fig. 2) against
it makes a certainty of response or alteration directly the end of cylinder and with
it the enin C is turned. Fig. 3 shows the method of finding the distance of moving
objects. An assistant or second observer being at A a definite distance away,
say 30 yards, using a right angle instrument, such as an optical square, or another
telemeter sei to zero (90°) and moving about forward or backward on the first
observer who remains as a pivot and to whom he is attached by a cord or tape.
attached in preferener to the waist belt keeps the object coincident by reflection
with the observer's instrument on which a sighting vane is fixed to assist in making
perfect coincidence. The observer at B Fig. 3 using the improved telemeter
moves the cylindrical end of the instrument and so keeps the assistant coincident
by reflection with the object. At a given signal, such as ON, the observer stops
turning the end of instrument and reads off the distance on the senle in yards or
units of measurement employed for the connecting line or tape forming the base.
Fig. 5 shews how the instrument can be used as an optical square for when set to
its true zero as explained, by putting toothed wheel so that arrow on revolving
collar F, & G zero (Fig. 1) correspond, & K agrees with zero on the revolving end of
instrument, if the observer looks at O through the instrument he will seo an object
or objects in true line of C and can erect a perpendicular, or on locking at C
& pivoting himself until he sees by reflection he will know any object on line C
will be at right angles to 0. The reason of having the collar F to revolvo
independently of cogged head of screw E and clamp at will by means of screw H
is that, the screw E may wear at the point or on being taken out replaced
differently & so the cogged head would require turning before a right angle was
reflected. If this were done the collar could be released by screw II, reset to G
& clamped by H.
In measuring the distance of inaccessible objects by one observer only, several
methods may be adopted with this improved telemeter but one considered a good
plan is now described as generally applicable, the others being variations of this
method.
Taking illustration in Fig. 6. the observer stands at A and with the telemeter
pointed in the direction of C. finds by pivoting himself, & slightly revolving the
instrument in his thumb and fingers, until he sees the object O by reflection he
then looks for a well defined object near the right angle C, and sees one at D.
or D' (called the mark). He then turns the rogged head screw above alluded
to (E) until O & D. or D' are coincident, now retiring along the line D. A.
or DA. for 30 yards or other measure of 30 units or any multiple or aliquot part
of sume and at the end E or E' he again looks at the mark D or D' and turning
the end of telemeter until he brings the reflection of O in coincidence with D or D
whichever he first chose as a mark. The numbered divisions shewn opposite
zero K Fig. 1 on fixed cylindrical portion of instrument will be the range of the
object.
If a proportion of 30 is used for the base A E, or A E' (Fig. 6) a similar
proportion must be used on result shewn on instrument, for instance if 15 is used
instead of 30 & which is half the normal base, the result shewn must be halved to
get the correct distance, and if 60 is used for base the result shewn on instrument
must be doubled.
In telemeters of this class previously introduced the cam was so arranged that the
reflected angle was greater than a right angle and so the observer lind to move
forward for the second observation and could not by himself keep perfect dressing
with Dor D', without going twice over some part of the ground, and they could

page_text: not under any circumstances take the range of a moving object by any of the
published methods of use.
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. The application to telemeters and other similar reflecting instruments of
the sextant type, of an independent collar to the screw that regulates the horizon
glass so that notwithstanding the position of the screw the collar can be set to
zero substantially for the purpose as set forth and figured and described.
2. The application to telemeters and reflecting distance measuring instruments
of a cam so arranged that it moves an index mirror through an arc so as to
reflect with another known as the horizon glass an angle less than 90 degrees
instead of greater as was previously the case with this class of instrument in the
manner aforesaid and substantially as figured and described.
3. An improved telemeter or distance measuring instrument substantially as
figured and described.
.