IMPROVEMENT IN OPTICAL INSTRUMENTS
Year: 1883

page_text: LETTERS PATENT to Donald Roderick Cameron Lieutenant Colonel Royal
Artillery of K, House, New Barracks, Sheerness for an Invention of AN
IMPROVEMENT IN OPTICAL INSTRUMENTS
PROVISIONAL SPECIFICATION left by the said Donald Roderick Cameron
at the Office of the Commissioners of Patents on the 29th September 1883.
DONALD RODERICK CAMERON, Lieutenant Colonel Royal Artillery of K House,
New Barracks Sheerness AN IMPROVEMENT IN OPTICAL INSTRUMENTS
To make it possible to see simultaneously and with clear definition through
telescopes and kindred optical instruments--two or more points at widely different
distances: and I accomplish this end by subdividing what is known as the object
glass into two or more adjustable parts so that each of them shall be capable of
separate focussing with the eye picce and be adapted simultaneously to objects at
as many different distances as there are parts of my modified object glass.
In using the words "parts of my modified object glass"-I do not confine my
meaning to a single lens in two or more parts, but include any combinations of
lenses adapted to bring rays of light from objects at different distances in the field
of view simultaneously to a focus with the eye piece of the instrument.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Donald Roderick Cameron in the Patent Office on the 11th March
1884.
DONALD RODERICK CAMERON, Lieutenant Colonel Royal Artillery, of K. House,
New Barracks, Sheerness "AN IMPROVEMENT IN OPTICAL INSTRUMENTS
"
This Invention has for its object the construction and arrangement of Telescopes
and of kindred optical instruments in such manner that they may be used to see
simultaneously and with precise definition, points or objects at different focal
distances.
In order to carry my invention into practical effect, I separate, or subdivide
without actual separation, what is known as the object glass or object piece into
two or more adjustable parts, so that each of them shall be capable of separate
focussing with the eye piece, and be adapted simultaneously to objects at as many
different distances as there are subdivisions of my modified divided or subdivided
object glass or object piece.
In using the words "subdivisions of my modified divided or subdivided object
glass or object piece," I do not limit or confine my meaning to a single lens or
reflector, but I include any combination of lenses or of reflectors, with or without
lenses, adapted to bring rays of light from objects at different focal distances in the
field of view, simultaneously to a focus with the eye piece of the instrument; and
in order that my invention may be more clearly understood, I will proceed to
explain, by the aid of the accompanying diagram and letters of reference marked
thereon, a mode in which the same when applied to terrestrial telescopes may be
carried out the external parts of the instrument being referred to by the capital
letters and the internal by the italic.
A. A. The exterior tube.
B. B. A short internal tube, firmly attached to A. A. so as to form part of the
same, in which the tube carrying the crossed wires or webs, and cyc piece, slides
when focussing.
.
C. Object glass or object piece. To admit of the close approach of the semilens c
to the object glass C. the object glass may preferably be attached by a screw
formed on the exterior of A A.
D. The tube carrying the crossed wires or webs at its inner extremity, and the
eye piece. It is provided with a suitable stop E, to prevent the crossed wires or
webs being pushed in beyond the principal focus of the object glass C.
E. The stop hereinbefore described.
F. Actuating screw for operating short internal tube a. a.
[
G. Casing or cover ou exterior of A A. which covers the slot or opening and
protects the actuating screw F.
a a A short internal tube (provided with lugs b b or their equivalent to enable
it to be actuated by a screw) sliding in the exterior tube A A. At the object end
of this short tube a a a converging semilens or other suitable or desired portion of
such a lens is placed, having its optical axis coincident with the optical axis of tho
telescope, so as to move with a aby the aid of the actuating screw F operated by
the milled head, as shown in the diagram. The extent to which a. a. may be
moved in the tube A. A is shown by the dotted lines of the part in its extreme
position at the eye piece end of the telescope, and it may be adjusted by means of
the screw F, to any part of this range of motion found suitable by the observer.
Actual contact however between the lenses C and c, and between the lens c and
the tube D carrying the crossed wires or webs, is prevented, as exposing the lenses
to injury.

page_text: A longitudinal slot or opening in the tube A. A is necessary to enable the
lugs b b which connect the internal tube a. a. with the external operating or
actuating screw F to move. As this opening would admit light and dust into
the interior, I cover both opening and screw, with a suitable casing G in order to
prevent it.
Assuming that the telescope above described is directed to an object from which
rays are focussed by the action of the object glass alone at the crossed wires; then
the image of a nearer object is formed by the same glass at the same time, but at
a more remote point than the crossed wires. If now another converging lens of
adequate power be suitably interposed between the object glass C and the
crossed wires, the image of the nearer object may be brought up to the crossed
wires. But a part of the second converging lens may be removed, and the
remaining portion will suffice to form an inage of the nearer object at the crossed
wires while the rays from the more distant object refracted by the lens C and
unobstructed by the portion left of the second lens, will simultaneously form an
image of the more distant object also at the crossed wires; and both of these images
may be simultaneously viewed through the eye piece.
In the case above described, the object glass and semilens together, are an
illustration of what I have referred to as a "noditied object piece."
The whole of the object glass and semilens concerned in forming an image of
the nearer object, are an illustration of what I have referred to as a "subdivision
of the object piece."
The object glass C considered separately with reference to the image which it
alone forms of the more distant object, is an illustration of another "subdivision of
the object piece."
Similarly in reflecting telescopes, reflectors may be combined with reflectors or
with lenses, to obtain images of objects at different distances, so as to be
simultaneously visible through an eye piece.
Having now described my invention of "An improvement in optical instruments"
and the manner in which the same is to or may be performed or brought into
practical use, I desire to state that I do not claim any of the parts separately as
new and of my invention as the same have been used before nor do I limit or
confine myself to the precise arrangements and details described and as shown in
the accompanying diagram as the same may be modified without departing from
the nature of my said Invention, but what I do claim as of my invention, and
desire to have protected by Letters Patent is :-
The application of an adjustable divided or subdivided object glass, or object
piece, in combination with other parts forming a telescope or kindred optical
instrument, whereby the instrument inay be adapted to view simultaneously objects
at as many different distances as there are divisions or subdivisions of the object
glass or object piece.
In witness whereof I the said Donald Roderick Cameron have hereunto set my
hand and seal this Sixth day of March in the year of Our Lord One thousand eight
hundred and eighty four.