IMPROVEMENTS IN THE MANUFACTURE OF ACHROMATIC LENSES
Year: 1881

page_text: LETTERS PATENT to Nathan Lazarus, of No. 76, Elgin Road, St. Peter's Park,
Paddington, in the County of Middlesex, Optician, for an Invention of
"IMPROVEMENTS IN THE MANUFACTURE OF ACHROMATIC LENSES."
PROVISIONAL SPECIFICATION left by the said Nathan Lazarus at the Office
of the Commissioners of Patents on the 5th October 1881.
"
NATHAN LAZARUS, of No. 76, Elgin Road, St. Peter's Park, Paddington, in
the County of Middlesex, Optician. IMPROVEMENTS IN THE MANUFACTURE OF
ACHROMATIC LENSES."
The object of my said Invention is to construct achromatic lenses in such a
manner that they may be cheaper, lighter, and more simply manufactured.
The means whereby I carry out my said Invention is as follows:-I take two
pieces of glass, each being of different material, such as crown glass and flint glass,
and having horizontally ground and then polished, one side of which I weld or
cement such polished surfaces together, whereby they become practically one glass.
I then grind and polish such glass as one in the usual manner, each face being
ground to its proper curve, according to the purpose for which it is required.
By this method of manufacture it is possible to make achromatic lenses
as thin as any lenses now made from any one kind of material, thus enabling them
to be used in the manufacture of spectacles and eye glasses, purposes to which
they have never been applied.
The process by which I join the glasses is perinanent, never showing the defects
which after a time are observed in all lenses manufactured by the old process.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Nathan Lazarus in the Great Seal Patent Office on the 5th April
1882.
NATHAN LAZARUS, of No. 76, Elgin Road, St. Peter's Park, Paddington, in
the County of Middlesex, Optician. "IMPROVEMENTS IN THE MANUFACTURE OF
ACHROMATIC LENSES."
The object of my said Invention is to construct achromatic lenses in such a
manner that they may be cheaper, lighter, and more simply manufactured.
The means whereby I carry out my said Invention is as follows:-I take two
pieces of glass, each being of different material, such as crown glass and flint glass,
and having one side of each first horizontally ground and then polished. I weld
or cement such polished surfaces together, whereby they become practically one
glass. I then grind and polish such glass as one in the usual manner, cach
face being ground to its proper curve, according to the purpose for which it is
required.
By this method of manufacture it is possible to make achromatic lenses as thin
as any lenses now made from any one kind of material, thus enabling them to be
used in the manufacture of spectacles and eye glasses, purposes to which they have
never yet been applied.
Tho junction of the glasses is permanent, and they never show the defects
which after a time are observed in all other lenses manufactured by the old
process.
Having thus described and ascertained the nature of the said Invention, and in
what manner the same is to be performed, what I claim is,-
The improvements in the manufacture of achromatic lenses, by the means, in
the manner, and for the purposes substantially as herein before set forth.
In witness whereof, I, the said Nathan Lazarus, have hereunto set my hand
and scal, this Fifth day of April, in the year of our Lord One thousand
eight hundred and eighty two.