IMPROVE- MENTS IN LENSES
Year: 1860

page_text: LETTERS PATENT to Richard Archibald Brooman, of 166, Fleet Street,
in the City of London, Patent Agent, for the Invention of "IMPROVE-
MENTS IN LENSES."-A communication from abroad by Charles C. Harri-
Sealed the 12th April 1861, and dated the 13th October 1860.
PROVISIONAL SPECIFICATION left by the said Richard Archibald
Brooman, at the Office of the Commissioners of Patents, with his
Petition, on the 13th October 1860.
I, RICHARD ARCHIBALD BROOMAN, of 166, Fleet Street, in the City of
London, Patent Agent, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN LENSES," (communicated to me from abroad by Charles
C. Harrison, of New York) to be as follows:-
This Invention consists in an improved construction of lens for optical
instruments designed primarily for use in cameras for taking photographs,
daguerreotypes, and other pictures, but is also adapted to microscopes, tele-
scopes, and similar instruments. The importance of obtaining a picture free
from distortion in the camera is well known, as is also that of securing the
largest field with any given aperture.
This improvement overcomes the difficulties hitherto experienced in each of

page_text: these points producing an image in which all the lines shall be parallel and
the flat field, as well as enabling the use of an aperture capable of taking in
a field, the extreme rays of which shall converge at so great an angle as ninety
degrees without distorting the image. This is accomplished by making a
compound lens consisting of an achromatic combination of two lenses, which
are meniscuses, the outer surfaces of which are segments of similar spheres,
and which lenses are so placed in the combination that their axes shall
coincide, and their outer surfaces form portions of a sphere of like diameter.
At a and b in the accompanying Drawings is shown an achromatic meniscus,
a being a concavo-convex lens of crown glass, and 6 a meniscus of flint glass.
The outer surface of a is a portion of a sphere of any desired diameter. The
outer surface of band the inner surface of a will coincide, so that the two may
be cemented together in a manner well known. Opposite to this a lens of like
construction, a', ', is so placed that the axes of the two will coincide, and their
surfaces if produced would form a complete globe, as indicated in Figure 1.
Now if the combination is properly made to insure perfect achromatism, it is
clear that the focal point of each compound lens will be the centre of the
sphere.
The operation will be as follows:-Any object being properly placed as c
will be exactly reproduced on the opposite side as at c', and of the same size if
at the same distance, or of sizes proportional to the respective distances, for it
is clear that whatever be the angle at which the rays are refracted to the
centre d of the sphere, they will so pass out through the opposite lens as to
restore the angle of incidence of the entering rays, and will thus unite to
produce the image upon a plane parallel with that from which the incident
rays proceeded.
In Figure 2 the two lenses are shown as mounted for use, the representation
being that of a longitudinal section in the plane of the axes of the lenses. A
diaphragm is fitted centrally between the aperture, being shewn at e, and thus
the whole forms the object glass of the camera.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Richard Archibald Brooman in the Great Seal Patent
Office on the 13th April 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, RICHARD
ARCHIBALD BROOMAN, of 166, Fleet Street, in the City of London, Patent 3.
Agent, send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirteenth day of October, in the year of our
Lord One thousand eight hundred and sixty, in the twenty-fourth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Richard Archibald Brooman, Her special licence that I, the said
Richard Archibald Brooman, my executors, administrators, and assigns, or
such others as I, the said Richard Archibald Brooman, my executors,
adminstrators, and assigns, should at any time agree with, and no others, from
time to time and at all times thereafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle of
Man, an Invention for "IMPROVEMENTS IN LENSES," (communicated to me from
abroad by Charles C. Harrison, of New York,) upon the condition (amongst
others) that I, the said Richard Archibald Brooman, my executors or adminis-
trators, by an instrument in writing under my, or their, or one of their hands
and seals, should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and cause the
same to be filed in the Great Seal Patent Office within six calendar months
next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Richard Archibald Brooman, do hereby
declare the nature of the said Invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and by the
following statement thereof, reference being had to the Drawings hereunto
annexed, that is to say :-
This Invention consists in an improved construction of lens for optical
instruments, designed primarily for use in cameras for taking photographs,
daguerreotypes, and other pictures, but is also adapted to microscopes, tele-
scopes, and similar instruments. The importance of obtaining a picture free
from distortion in the camera is well known, as is also that of securing the
largest field with any given aperture.
This improvement overcomes the difficulties hitherto experienced in each of
these points, producing an image in which all the lines shall be parallel and
the field flat, as well as enabling the use of an aperture capable of taking in
a field, the extreme rays of which shall converge at so great an angle as ninety
degrees without distorting the image. This is accomplished by making a
compound lens consisting of an achromatic combination of two lenses which are
meniscuses, the outer surfaces of which are segments of similar spheres, and
which lenses are so placed in the combination that their axes shall coincide,
and their outer surfaces form portions of a sphere of like diameter.

page_text: At a and b, in the accompanying Drawings, is shown an achromatic meniscus,
a being a concavo-convex lens of crown glass, and 'b a meniscus of flint glass.
The outer surface of a is a portion of a sphere of any desired diameter. The
outer surface of and the inner surface of a will coincide, so that the two
may be cemented together in a manner well known. Opposite to this, a lens
of like construction a, b, is so placed that the axes of the two will coincide,
and their surfaces if produced would form a complete globe, as indicated in
Figure 1. Now, if the combination is properly made to insure perfect achro-
matism, it is clear that the focal point of each compound lens will be the
centre of the sphere.
The operation will be as follows:-Any object being properly placed as c,
will be exactly reproduced on the opposite side as at c³, and of the same size if
at the same distance, or of sizes proportional to the respective distances, for it
is clear that whatever be the angle at which the rays are refracted to the
centre d of the sphere, they will so pass out through the opposite. lens as to
restore the angle of incidence of the entering rays, and will thus unite to
produce the image upon a plane parallel with that from which the incident
rays proceeded.
In Figure 2, the two lenses are shown as mounted for use, the represen-
tation being that of a longitudinal section in the plane of the axes of the lenses.
A diaphragm is fitted centrally between the aperture being shewn at E, and
thus the whole forms the object glass of the camera.
And having now described the nature of the said Invention and in what
manner the same is to be performed, I declare that I claim, the construction
of lenses for optical instruments in manner and for the purposes herein-before
described and illustrated in the accompanying Drawings.
In witness whereof, I, the said Richard Archibald Brooman, have here-
unto set my hand and seal, this Thirteenth day of April, One thousand
eight hundred and sixty-one.