IMPROVEMENTS IN STEREOSCOPES.
Year: 1855

page_text: LETTERS PATENT to Antoine François Jean Claudet, of Regent Street,
in the Parish of St. James, Westminster, in the County of Middlesex,
Photographis Artist for the Invention of "IMPROVEMENTS IN STEREOSCOPES.
PROVISIONAL SPECIFICATION left by the said Antoine François Jean
Claudet at the Office of the Commissioners of Patents, with his Petition,,
on the 8th March 1855.
I, ANTOINE FRANÇOIS JEAN CLAUDET, of Regent Street, in the Parish of
Saint James; Westminster, in the County of Middlesex, Photographic Artist,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
STEREOSCOPES," to be as follows:-
.
1. The first improvement is the making the interior of the stereoscope near
the end at which the pictures to be viewed are placed, of such a form that the
rays of light entering the stereoscope from the lid or opening which lights the
pictures cannot be reflected from the interior on the pictures, or the frame
upon which they are, and thence to the eye of the observer; the pictures and
the frame carrying them are herein afterwards called the slide. The improved
form is like an ordinary stereoscope for about half the distance from the end at
which the eye pieces are inserted, and then the sides and also the top and.

page_text: bottom are rather enlarged, and are made in a curved form instead of being
straight. The rule which will give the form required is that all parts lighted
by the opening or lid, and which could otherwise be reflected to the eye of the
observer shall be curved, so that the tangent of the curve at any point shall
make with the slide an angle greater than ninety degrees.
2. The second improvement is the placing at the inner end of a short tube,
of about half an inch, upon which the eye piece is fixed, a continuation of
such tube, ending about half way between the slide and the eye, and next the
slide by an opening of such a size and form as to allow the picture to be seen,
and at the same time wholly to hide the frame. These continued tubes are not
cylindrical, but are made of four flat sides expanding in a length of about one
inch, and then these four sides in another length of about one inch extend in
contracting; these continued tubes being in fact composed of two truncated
pyramids having their bases turned towards each other, forming a small chamber
at the end of each eye tube, having its opening of the form and size mentioned.
They are blackened within, and such blackness and the form given to them
cause the interior not to be noticed by the eye, and not to be reflected on the
picture, and when they are used no portion of either picture is seen, except
where the two pictures coalesce and form one picture by the refraction of the
lenses, and an effect is produced as if the object represented in the picture
formed by the coalescing pictures were seen through a door, window, or other
opening in a space beyond such opening. But in order to insure this effect,
care must be taken to have the two corresponding sides of the two openings
forming an angle smaller than any two corresponding points of the first plane
of the picture; for if these conditions were inverted, although the openings of
the tubes should be considerably before the picture, still they would appear as
if situated beyond the picture.
3. The third improvement is an arrangement which enables persons whose
eyes
are at different distances apart to use the improved instrument without difficulty
and without any adjustment being required. The tubes in which the two eye
glasses are fixed are placed about two and a half inches apart, as usual, but
have a diameter of one inch, being from one quarter to three-eighths of an
inch more than is generally the case. Each eye glass is a semilens, care being
taken not to employ any part of the lens beyond the centre, which for eyes
the greatest distance apart would produce a divergence instead of a convergence.
When the form of lens used is the meniscus, the concave side is turned towards
the eye in order to prevent the reflection of extraneous objects, and the lens is
mounted flush with the outer end of the tube. Of the semilens in each eye
piece the only portion used (the rest being covered by a frame or varnish

page_text: or other suitable means) is a horizontal space of a quarter of an inch in height,
extending across the tube in a direction of the diameter of the lens.
4. The fourth improvement is a convenient mode of adjusting the foci of the
lenses to the focal length usually required by the varieties of long, common, and
short sight. This improved mode of adjustment is obtained by connecting the
sliding parts of the two tubes by a cross piece attached to a stem entering the
apparatus between the two tubes and sliding in a groove. On each side of
the groove are three marks, with which a pin or mark on the slide may be made
to coincide; that nearest the eye pieces is marked long sight, the middle one
common sight, and the third short sight. By pulling out or pushing in the
sliding piece carrying the moveable part of the eye tubes, the index is brought
to the line required for each sight, and the focus of the instrument is at once
adjusted to one of the three divisions, so as to suit the observer. The distance
between the marks for each sight should be about one-third of an inch.
5. The fifth improvement is a mode of mounting several slides on a revolving
frame, and exhibiting them to view in succession, the eye tubes being closed
while the change of picture is made. A frame is used with square ends, and
having each side just larger than a slide. The ends are connected at the
corners by pieces of metal slightly countersunk to prevent the slides falling off.
At one end is a groove to receive the end of the slide, and at the other end a
catch pressed by a slight spring fixes the slide and retains it in its place, and at
the same time gives great facility for changing the slides. When four slides
are arranged on the frame, it appears like a square box or block, of which the
slides form the sides. At each end is an axle passing through the side of the
stereoscope, which is prolonged to receive it. In front, towards the observer,
and below and rather at one side of the eye pieces, is a handle, by pulling which
a bar is drawn out that has upon it a rack, which turns a toothed wheel about
two inches in diameter. This toothed wheel works upon an inner ratchet wheel
and turns the frame, but being made to move freely on the axle has no effect
when returning to its original position. To the axle at the other end of the
frame is fixed a wheel, also about two inches in diameter, having four catches
answering to the four sides of the frame, and into these catches as the frame is
turned round a small bolt bevilled on one side is pressed by a spring, allowing
the frame to turn when the handle is pulled out, but retaining it in its place
when the handle is pulled back. The bar with the handle attached to it is
drawn back and retained in its original position by a weight or spring. The
rack work is so arranged upon the bar that the bar may be pulled out about
half an inch before the rack work acts upon the toothed wheel. A small shutter
closing upwards is hinged to the interior of the stereoscope under the eye pieces

page_text: so as to shut them when it is closed. A small arm attached to a weak spiral
spring which is coiled round the bar presses up the lid, and closes it while the
bar is being drawn out the first half inch, and the spring then acts on the arm
and keeps the shutter closed during the rest of the outward pull, which turns.
the frame and changes the picture, and as the bar returns to its place the spring
still keeps the shutter closed until the last half inch of the return pull, when
the arm opens the shutter; thus the shutter is closed before and during the
whole change of the picture. The frame may be made with a different number
of sides, and a corresponding adaptation of the other parts, but for glass slides
the four-sided frame is best, as it avoids shadows. It is obvious that other
mechanical means may be applied to obtain the movements required.
6. The sixth improvement is the use for each eye piece of the central part
of a whole lens instead of a half lens, so that the pictures are seen through
the lenses at or very near to their centres; but in this case the axes of the
eyes of the observer must converge in order to produce coalescence of
the pictures. The vertical lines and objects seen thus appear straight and
of the natural form instead of being curved, as when seen through the half
lenses generally used. By the use of the central parts of whole lenses the
spherical and chromatic aberrations will also be greatly obviated. No. 3 is
not applicable to the whole lenses.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Antoine François Jean Claudet in the Great Seal Patent
Office on the 7th September 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ANTOINE
FRANÇOIS JEAN CLAUDET, of Regent Street, in the Parish of St. James,
Westminster, in the County of Middlesex, Photographic Artist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eighth day of March, in the year of our Lord
One thousand eight hundred and fifty-five, in the eighteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Antoine François Jean Claudet, Her special, license that I, the said
Antoine François Jean Claudet, my executors, administrators, and assigns, or
such others as I, the said Antoine François Jean Claudet, my executors,
administrators, 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

page_text: the United Kingdom of Great Britain and Ireland, the Channel Islands, and
Isle of Man, an Invention for "IMPROVEMENTS IN STEREOSCOPES," upon the
condition (amongst others) that I, the said Antoine François Jean Claudet, by
an instrument in writing under my hand and seal, 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 Antoine François Jean Claudet, do
hereby declare the nature of my said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained in and
by the following statement, reference being had to the Drawings hereunto
annexed, and to the letters and figures marked thereon, the same letters
referring throughout to similar parts (that is to say) :-
One of my improvements is the giving to the interior of the casing or box of
the stereoscope such a form that no part of it can be reflected from the pictures
or the frame upon which they are to the eye of the observer; such reflection is
a defect of ordinary stereoscopes. The pictures and the frame carrying them
are herein afterwards called the slide.
Figure 1 represents the ordinary shape of the casing of the old stereoscopes,
but the sides are sometimes straight instead of curved; this Figure is a sectional
top view; Figure 2 is an outside plan view of the improved form of stereo-
scope, as seen from the top; Figure 3 is an outside view of the same from the
end at which are the eye pieces; Figure 4, an outside view of the same from
the other end at which the slide is placed; Figure 5 is a side view of the same;
Figure 6 is a vertical section of the same on the line E, F, Figure 2; Figure 7,
a section thereof on the line A, B, Figure 4. These Figures shew that the
inside and outside curved lines of the casing correspond. Figure 8 is another
section taken on the line C, D, Figure 7. A perpendicular from the tangent
at any point which could otherwise be reflected of the curve of the interior of
the casing must make with the slide such an angle as will not reflect it to the
eye of the observer.
Another of my improvements consists in placing within the outside casing
two chambers, so adjusted that the inner end of each eye tube shall be central
with the open end of one of the chambers. These chambers are blackened
throughout, within, and also on the outside, towards the slide, and they end
about half way between the slide and the eye, and the end of each chamber
towards the slide has an opening corresponding to the form of the picture.
These openings allow the pictures to be seen freely, and wholly hide the frame:

page_text: In Figure 2, a, a, are the eye pieces; b, b, the outer casing; c, c, the inner
chambers; d is the lid or flap to admit light when the pictures to be viewed are
not transparent; e, e, apertures to admit the slides.
Another of my improvements consists of an arrangement of the lenses of the
eye pieces, which enables persons whose eyes are at different distances apart to
use the instrument without any adjustment being required to suit the different
observers, as is the case in the old form of stereoscope. This improvement is
shewn in Figures 3, 7, and 8, and consists in making each eye piece out
of a half lens, and if the meniscus form be used the concavé side should be
towards the eye, in order to the prevention so far as possible of reflection from
the lens. The only transparent parts of the lenses through which the observer
can view the pictures are the central horizontal strips f, f; the other portions
of the lenses are blackened and rendered opaque.
Another improvement is a convenient mode of adjusting the foci of the
lenses to the focal length usually required by the varieties of long, common,
and short sight. This improved mode of adjustment is obtained by connecting
together the sliding parts g, g, of the two eye tubes by a cross piece which is
fixed on to the inner end of the sliding parts of the two tubes, and which cross
piece carries with it a small arm, upon which is mounted an index. This index
works through a slot in the outer casing, and as the tubes are pushed inwards
or drawn outwards, indicates on the graduated scale fixed outside of the casing
of the stereoscope the required sight. The line nearest the eye is marked
long sight, the middle one common sight, and the third short sight. The
distance between the marks for each sight should be about half of an inch.
Another of my improvements is a mode of mounting several slides on a
revolving frame, and exhibiting them to view in succession. This will be
understood by reference to Figures 9 and 10, which shew a transverse and a
portion of a horizontal section of a stereoscope having my revolving frame
intended to carry four slides; the internal form of the stereoscope with its inner
chambers and improved eye pieces being the same as before described. h, h, h,
are the grooves for carrying the slides h'; i is the axis upon which the frame
j, j, revolves; k and are a ratchet wheel and pall, which prevent the frame
revolving while the picture is being viewed. In order to give rotation to the
franie and change the picture to be viewed, it is only necessary to turn the
screw m.
A further improvement in the exhibition of the revolving frames is the
following: Figure 11 is a sectional side clevation, Figure 12 a plan view,
Figure 13 a transverse section on the line G, H, in Figure 12. j is the
revolving frame; i is the axis, and k and the ratchet wheel and pall; and h,

page_text: the
groove carrying the slide h'; n, n, m, n, are elastic plates, which are drawn
back to admit the slides being placed in the grooves h; these plates have
projecting pieces 0, 0, 0, 0, on their sides, that retain the slides in their places;
p and q are two standards, within which the frame revolves. Upon the end of
the revolving frame next the standard p is mounted a small toothed wheel r
gearing into the rack s. Inclosed in a chamber behind this toothed wheel are
the ratchet wheel k and the pall 7. On the other end nearest the standard 9
is mounted the wheel t, having four catches von its periphery, into which
works the bolt u. This is fully seen at Figure 14, and the edge view
Figure 15, which shews an elevation of the standard q, the wheel t, and bolt u
with the spiral spring w beneath it. Beneath the toothed wheel r is mounted
the bar, which is made to work easily by means of the springs a', x'. This
bar carries with it the fixed collar y, and the sliding collar y', between which is
mounted a spiral spring. Upon the edge of the collar y' is screwed the bent
arms, the end of which turns the shutter moving upon the studs z", 2". At
the other end of the bar is mounted the bent arm 1. The bar a being drawn
forward towards the eye pieces compresses the spiral spring between the
collars ย and y', and brings forward the rack s under the toothed wheel r,
which causes the revolving frame j to turn, and with it the wheel t, until the
bolt enters one of the catches v, when one of the slides is brought into
position to be viewed by the observer. Just as the bolt u takes into the
catch v, the bent arm 1 is brought into contact with the back side of the
revolving frame j, in order to give steadiness to it. As it adds to the effect of
the change of the pictures that such change should not be seen by the
observer, the shutter is made to cover the interior ends of the eye pieces
during the change. This is effected by the beginning of the motion forward
of the bar x, before described, which brings forward the collar y¹ carrying the
bent arm z, which causes the shutter ¹ to rise to the position shewn in
Figure 11. By the collar y pressing against the inside of the frame at 2, 2,
by the compression of the spiral spring, the shutter z¹ is kept closed while
the rack travels forward, giving partial rotation to the frame j.. Upon the bar
being brought back to its original position by means of the weighted cord
passing under the pulley 3 and over the pulley 4, the shutter ¹ becomes open,
and takes the position shewn by the red lines in Figure 11, as soon as the
spiral spring no longer acts upon the sliding collar. y', and not before. Although
I have described the revolving frame as only carrying four slides, yet, when
desired, it may be so arranged as to carry a larger number, either by encreasing
the number of sides of the revolving frame, or by means of a series of slides
being so connected together as to form an endless band revolving over and

page_text: with the frame in a vertical position. To do this it will be only necessary to
alter the external shape of the box so as to admit of the slides hanging beneath
the revolving frame, or the slides may revolve horizontally as an endless band
over two revolving frames. And when it is required that an apparatus should
be formed in order that several persons may be enabled to view pictures at the
same time, it is only necessary to mount several sets of apparatus, such as
described in Figure 11, within any polygonal formed box or chamber.
Another of my improvements is the use for each eye piece of the central
part of a whole lens, instead of a half lens, so that the pictures are seen through
the lenses at or very near to their centres. In this case the lenses will not
cause the two pictures to coalesce, and be seen as one, but the axes of the
eyes of the observer must converge in order to produce coalescence. Many
persons will find it difficult to produce the necessary convergence of the axes
of the eyes, and some may be unable to produce it; by a little practice, how-
ever, most persons will obtain 'the right degree of convergence. By the use of
the central parts of whole lenses the vertical lines and objects shewn in the
pictures will appear straight and of the natural form, instead of being curved,
as when seen through the half lenses generally used. By the use of the
central parts of whole lenses, the spherical and chromatic aberrations will also
be greatly reduced. The mode before described of arranging the lenses for
observers whose eyes are at different distances apart is not applicable to the
use of the central parts of whole lenses unless the exterior parts of the hori-
zontal strips of the lenses beyond the centres be also blackened and rendered
opaque, as such parts would, if used by the observer, produce divergence of
the pictures.
Having now fully described my said Invention, I rest my claims to
novelty,―
Firstly, in giving such curvature in form, as before described, to the interior
of the outer casing of, and providing interior chambers to, the stereoscopes,
so as to greatly reduce the reflection which takes place in ordinary stereo-
scopes, and to shut out from the sight of the observer all extraneous objects.
Secondly, in the adaptation of the lenses so as to obviate the necessity of
any adjustment to suit observers whose eyes are at different distances apart, as
before described.
Thirdly, in obtaining, by the means of an index, the ready adjustment of the
foci of the eye pieces to the three usual varieties of sight.
Fourthly, in the application to stereoscopes of a revolving frame or frames
carrying a series of slides, whether caused to revolve by hand or by suitable
machinery.

page_text: Fifthly, in shutting off the sight of the revolving frame while the pictures
are being changed by means of the rising and falling of the shutter, as before
described.
And, lastly, in the use of central parts of whole lenses for the eye pieces,
and so avoiding the distortion of objects.
In witness whereof, I, the said Antoine François Jean Claudet, have
hereto set my hand and seal, this Seventh day of September, in the
year of our Lord One thousand eight hundred and fifty-five.
Signed, sealed, and delivered by the above-
named Antoine François Jean Claudet,
in the presence of
THOMAS DRY, Solicitor,
25, Lincoln's Inn Fields.
A. CLAUDET. (L.B.)