Apparatus for the Conversion of Light Waves into Electrical Waves, for the Transmission of such Electrical Waves to a Distance, and for the Reconversion of such Electrical Waves into Light Waves; also for Recording such Waves upon Suitably Prepared Surfaces.
Year: 1898

page_text: Date of Application, 27th Oct., 1898-Accepted, 27th Oct., 1899
COMPLETE SPECIFICATION.
Apparatus for the Conversion of Light Waves into Electrical Waves,
for the Transmission of such Electrical Waves to a Distance, and
for the Reconversion of such Electrical Waves into Light Waves;
also for Recording such Waves upon Suitably Prepared Surfaces.
I, ALFRED EDOUARD LARDEUR, F.G.S., of Clare House, 85, Abbeville Road,
Clapham Park, in the County of London, Manufacturer, 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:
-
This invention relates primarily to apparatus for the conversion of light waves
into electrical waves, for the transmission of such electrical waves, and for the
reconversion of such electrical waves into light waves.
It consists of two parts, one of which, termed the transmitter, fulfils the
same function as the transmitter in a telephone, except that in this case a picture
or light waves are received instead of sound waves, this transmitter is in electrical
communication with a second apparatus, termed the receiver, in which tho
electrical waves are reconverted into light waves, and where the picture is
rendered visible.
In order that my invention may be more fully understood, I will now proceed
to describe the same with reference to the drawings accompanying this specifi-
cation, in which Figure 1 is a diagrammatic view of the transmitter, Figure 2
a diagrammatic view of the receiver, Figure 3 shews a modified form of the
receiver, Figs. 4 and 5 are views shewing a method of recording the electrical
waves and of reproducing such waves respectively. Figs. 6 to 11 shew details
hereinafter referred to.
The same letters of reference are employed to denote the same parts in all
the views.
With reference to Figure 1, a is a chamber, preferably a vacuum chamber (in
order to exclude sound waves), 6 a lens, and c is a screen constructed in the follow-
ing manner. Copper wire gauze, or other suitable material is pressed into a layer
of molten selenium, so that the selenium, when cold, well fills up the openings
in the gauze, and that the front side of the screen offers to the light a surface
entirely of selenium.
A screen of selenium alone may be used, when sufficiently coherent, or in
some cases non-conducting gauze or the like may be used..
The screen is shewn detached at Figure 11.
In front of the screen c I mount two discs d, d, capable of revolving in circum-
ferential supports. The method of supporting these discs is shewn at Figure 6,
from which it will be seen that they are supported by brackets 2, attached
to the walls of the chamber a. At Figure 7 is shewn in side view part of one
of the discs, with a toothed ring 3 fixed to the back of it. Suitable clock or other
mechanism mounted on the top of the chamber at 4 (Figure 1), drives these
discs d, d, by means of the toothed rings 3. The discs d, are composed of
vulcanite or any other suitable substance impervious to light. The disc d has
radial slots, as shewn at 5 Figure 8, whilst the disc d is furnished with groups

page_text: of perforations, such groups being either more or less in number than the slots
on the discs d. The object of the arrangement of the slots and perforations
is that only one ray of light at one time shall pass through and impinge upon
the selenium screen c. One way of arranging the slots and perforations is shewn
at Figures 8 and 9, g Figure 9 shews the perforations.
Thus if the discs are rotated in the same directions at different velocities, or in
opposite directions at the same or different velocities, it will be seen that passage
is allowed to only one ray of light at a time.
The screen c of selenium is interposed in the circuit of an electric battery, or
other source of electricity, the wires of which communicate with the receiver.
6 Figure shews a frame, which may be used when it is desired to transmit a
picture or message. The picture, message or the like, on translucent material,
is fixed in the said frame, and light is allowed to enter through the aperture
from which the lens has been removed.
The receiver, shewn at Figure 2, is constructed as follows:-A is the contain-
ing chamber, B a lens, and D, D are discs, rotating synchronously with the
discs, d, d, and actuated in a similar manner by mechanism at 4. In this case
the disc D (see detached sectional view at Figure 10) forms the continuation of
a soft iron axle h: around this axle h is fitted an electrical coil i, which is in
the circuit of the selenium screen and the battery, so that when the electrical
current passes through the coil, the axle and consequently the disc are magnetised.
The axle is supported in a suitable standard.
The disc D bears upon that surface towards the lens bars or strips of metal t
exactly corresponding in form and position to the slots in the disc d. The other
disc 1), is made of vulcanite or other non-magnetic material, and is provided
with pins k, made preferably of soft iron and set in positions corresponding exactly
to the positions of the perforations on the disc d'. 7 shews a diaphragm, stretched
across the chamber A and made of a foil of a metal capable of being attracted
by a magnet. I prefer to silver that surface of the diaphragm which is towards
the lens. m shews an electric lamp for casting light upon the foil if found
necessary.
The action of this apparatus is as follows:-
A current is kept flowing through the circuit. When a ray of light passes
through the coincident apertures of the discs d, d¹, the conductivity of the
selenium is impaired and consequently the strength of the current in the circuit
is less. The result is that the magnet 1) is magnetised to a lesser degree. Now,
at this moment, owing to the synchronous rotation of the discs d, d and D), D',
respectively, the bar on the face of the disc D, and the pin on the disc D',
which are in contact, will be that bar and that pin corresponding to the slot
and perforation coincident at that moment. The result will be that an attraction
will be exerted upon the foil, corresponding in position to the position of the
apertures at that moment open to the ray of light, and in extent to the intensity
of that ray of light. Owing to the rapid rotation of the discs, the observer
will see a complete picture.
If desired a lens may be provided at the front of the chamber A, and the image
cast upon a suitable screen.
Figure 3 shews a form of receiver to be used when it is desired to obtain
permanent records upon suitably prepared surfaces.
In this case D, and D' are discs similar to those already described and rotated
in the same manner. The disc D is made of a material which is a good con-
ductor of electricity, and bas bars t¹ upon its face, similar in all respects to those
described in the case of the receiver shewn at Figure 2, except that they are
not necessarily made of soft iron. The disc D' is provided with pins k', similar
in position to those of the disc D in Figure 2, but in this case composed of
copper, brass or other suitable electro-conductive material. In this case more-
over the disc 1 is a non-conductor of electricity. u shews a hinged flap or
frame, made of conducting material. The flap is shewn turned down and in

page_text: section at n¹. Across this frame is stretched a film o, composed for example of
insoluble gelatine, or paper impregnated with potassium iodide, or other sub-
stance subject to change of colour when decomposed by electricity. p is a ter-
minal in connection with the flap n, g another terminal in connection with the
disc D. These terminals are electrically connected with the battery and the
transmitter.
The action of this apparatus is similar to that described in the first part of
the invention, with the exception that in this case the effect is electrical instead
of magnetic, the current passing through the film or paper and darkening it in
such a manner as to reproduce the writing or picture transmitted.
With reference to Figures 4 and 5, Figure 4 shews the recording apparatus
and Figure 5 the reproducing apparatus. shews a cylinder of vulcanite, wax
or other suitable material, mounted upon a standard r. To this cylinder is
imparted simultaneous rotary and longitudinal motion, which may be effected
in a similar way to that used in the case of phonographic cylinders. s is a electro-
magnet, provided with a contact breaker w.
The current from the battery passes through the coil of the magnet. s. and
back by way of the contact breaker w. u is a point formed or fixed on the back
of the contact breaker, which makes a series of depressions upon the cylinder ",
of greater or less depth, according to the intensity of the current.
In this manner a record is made of the electrical waves.
Fig. 5 shews the reproducing apparatus. is the cylinder bearing the records;
are standards supporting the cylinder ; w is a contact-breaker, and u a
point similar to the point u, Fig. 4. The contact-breaker is in the electrical
circuit of a receiver such as that shown at Fig. 2 or that at Fig. 3. Thus, when
the cylinder is given motion (the same as that imparted to it in the recorder,
Fig. 4) the point on the contact-breaker is actuated by the depressions in
the cylinder, and electrical waves, similar to those which produced the records,
are set up in the circuit.
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. Apparatus for the conversion of light waves into electrical waves, for the
transmission of such electrical waves to a distance, and for the reconversion of
such electrical waves into light waves; also for recording such waves upon
suitably prepared surfaces; substantially as set forth.
2. Making the transmitter and receiver of apparatus for the conversion of light
waves into electrical waves and for the reconversion of such electrical waves into
light waves air-tight, so that the air may be exhausted therefrom, for the pur-
pose of excluding atmospheric vibrations.
3. In apparatus such as that specified in the transmitter, the combination of
two discs, rotating in the same direction at different velocities or in opposite
directions at the same or different velocities, such discs being provided with
apertures so arranged that during the rotation of the said discs only one aperture
on one disc coincides with one aperture on the other disc at the same time.
4. In apparatus such as that specified in the transmitter, the discs as described
in combination with a seleniuni screen, for the purpose set forth.
5. In apparatus such as that specified in the receiver, two discs rotating
synchronously with the discs in the transmitter, one of such discs (forming the
extension of the core of an electro-magnet) having strips of soft iron, and the
other (a non-magnetic disc) having pins of the same metal, such strips and pins
corresponding respectively in arrangement to the slots and perforations in the
discs in the transmitter, in combination with a diaphragm of metal capable of
being attracted by magnetism, all for the purposes set forth.
6. In apparatus such as that specified: a receiver provided with two discs
rotating synchronously with the discs in the transmitter, one of such discs

page_text: having strips of metal, and the other (of insulating material) having metal pins
such strips and pins corresponding respectively in arrangement. to the slots
and perforations in the discs in the transmitter, in combination with a frame of
conducting material for the reception of a suitably prepared film or paper, all for
the purposes set forth.
7. In apparatus such as that specified': the combination with the transmitter
of recording..mechanism.
8. Recording mechanism substantially as and for the purpose set. forth.
9. In apparatus such as that specified: the combination. with the receiver of
reproducing mechanism.
10. Reproducing mechanism substantially as and for the purpose set forth.
Dated this 4th day of March 1898
BROWNE & Co.,
Agents for the Applicant, 9, Warwick Court, Gray's Inn, W.C.