The earliest attempts to send pictures and to see electrically date back
some fifty years, being practically coincident with efforts to transmit
sound electrically.
At first a metallic circuit was employed to carry the impulses
representing picture values, but when radio was available several
workers immediately began the adaptation of their apparatus to radio
circuits.
Some remarkably fine examples of pictures transmitted by both wire and
radio have been produced in recent months; most of them showing the
lines, but some of them without lines at all, _i. e._, true photographic
results.
And as the transmission of images from living subjects in action differs
from “still” pictures only in that they are more rapidly formed, it
naturally followed that the solution of this problem should also be
undertaken.
When radio service to the eye shall have a comparable development with
radio service to the ear, a new era will indeed have been ushered in,
when distance will no longer prevent our seeing our friend as easily as
we hear him.
Our President may then look on the face of the King of England as he
talks with him; or upon the countenance of the President of France when
exchanging assurances of mutual esteem.
The general staff of our Navy and Army may see at headquarters all that
a lens looks upon as it is carried aloft in a scouting airplane over
battle front or fleet maneuvers.
And from our easy chairs by the fireside, we stay-at-homes can watch the
earth below as a great ship, like the Shenandoah, carries our flag and a
broadcasting lens, over the mountains and plains, the cities and farms,
the lakes and forests, of our wonderful country.
In due course, then, folks in California and in Maine, and all the way
between, will be able to see the inaugural ceremonies of their
President, in Washington; the Army and Navy football games at Franklin
Field, Philadelphia; and the struggle for supremacy in our national
sport, baseball.
The new machine will come to the fireside as a fascinating teacher and
entertainer, without language, literacy, or age limitation; a visitor to
the old homestead with photoplays, the opera, and a direct vision of
world activities, without the hindrance of muddy roads or snow
blockades, making farm life still more attractive to the clever
country-bred boys and girls.
Already audible radio is rapidly changing our social order; those who
may now listen to a great man or woman are numbered in the millions. Our
President recently talked to practically the whole citizenship of the
United States at the same time.
When to this audible radio we add visible radio, we may both hear and
see great events; inaugural ceremonies, a football, polo, or baseball
game; a regatta, mardi gras, flower festival, or baby parade; and an
entire opera in both action and music.
Educationally, the extension worker in our great universities may then
illustrate his lecture, for the distant student can see as well as hear
him by radio.
It is not a visionary, or even a very difficult thing to do; speech and
music are carried by radio, and sight can just as easily be so carried.
To get music by radio, a microphone converts sound into electrical
modulation, which, carried by radio to distant places, is then changed
back into sound and we hear the music.
To get pictures by radio, a sensitive cell converts light into
electrical current, and at radio distances changes these currents back
into light values, and one may see the distant scene; for light is the
thing of which pictures are made, as music is made of sound.
To further show the close relation, it might be added that in receiving
sets these same electrical values can be put back either into sound with
headphones or into light with a radio camera; although it may be
admitted that such radio signals do not make much sense when with
headphones one listens to the pictures.
Already radio vision is a laboratory demonstration, and while it is not
yet finished and ready for general public introduction, it soon will be,
for it should be borne in mind that animated pictures differ from still
pictures only in the speed of presentation, and the sending of “still”
pictures by radio is now an accomplished fact, radio photographs of no
mean quality, examples of which appear as illustrations in this volume.
Just as is done in radio photographs the picture surface is traversed by
a small spot of light moving over the picture surface in successive
parallel adjacent lines, with the value of the lines changed by the
incoming radio signals to conform to a given order, the order being
controlled by the light values of the scene at the distant sending
station.
In sending pictures electrically, there have been but two methods
employed, perhaps the only methods possible; namely (_a_) a cylinder
mechanism; and (_b_) a flat surface.
Without exception, every scheme which had attained any degree of
success, before the author adopted flat surfaces, has depended upon
synchronous rotation of two cylinders, one at the sending station with
the picture thereon to be sent; and the other at the receiving station
where the picture is to be put.
Perhaps the very obviousness of the cylinder scheme, and that there are
no patents to prevent, explains why it has been employed by so many. And
there have been many workers in this line of endeavor; for example, in
England, Lord Northcliff, Sir Thompson, Mr. Evans and Mr. Baker; in
France, MM. Armengaud, Ruhmer, Rignoux, Fournier, and Belin; in Germany,
Paul Nipkow, Dr. Anchutz, and Dr. Korn.
In America, Mr. Ballard, Mr. Brown, and Mr. Amstutz, the latter
deserving particular mention, for, from a distant picture, a swelled
gelatine print, he engraved a printing plate which could be put directly
on a printing press for reproduction.
All these many workers have adopted the cylinder method of sending and
receiving, and all have arrived at approximately the final stage of
development permitted by concurrent science.
It may be well to explain that, in these older schemes, the picture to
be sent is wrapped around the cylinder, usually a cylinder of glass
where light sensitive cells are employed, mounted on a rotating shaft,
which also has longitudinal displacement.
The light values which make up the picture are converted into electric
current of corresponding values and put upon a wire or other channel
which delivers them to the distant receiving station.
At the receiving station a suitable film-like sheet (paper, for example)
is wrapped around a cylinder similar to that at the sending station. As
this cylinder is rotated and longitudinally advanced under a stationary
point in contact with the paper on the cylinder, a spiral is traced
thereon. As the incoming electrical current represents picture values,
and as the two cylinders are turning in exact synchronism, a picture
duplicate of that at the sending station appears thereon. After the
picture is completed the paper sheet can then be taken off the cylinder
and flattened out for such use as may be desired.
It is quite obvious that vision by radio and radio movies can never be
attained by a cylinder method, for as the picture must appear to the eye
complete, by reason of persistence of vision, it naturally follows that
the eye must make up the whole picture from a single focal plane.
The attainment of “television” or Radio Vision, as it is now coming more
commonly to be called, requires that the sending shall be from a flat
plane, and reception on a flat plane, and a modulation which will give
not only the high-lights and shadows but the halftones as well.
These “flat planes” may, of course, be the focal planes of the lenses
employed at the receiving station, and from the focal depth of the lens
at the sending station where the picture may perhaps be taken from
living actors in the studio or from an outdoor scene.
At the receiving station the “flat surface” may be a photographic plate,
a white wall, or a miniature of the usual “silver sheet” of the motion
picture theatre.
It may aid in a clearer and quicker understanding of the text if the
words telephone and television be limited to metallic circuit service,
while radio phone and radio vision is applied to radio carried signals,
and this designation will be employed in the following pages.
[Illustration: [Projector]]
[Illustration: [Photographs]]
This and succeeding pages are examples of photographs received by radio
from a distance, by the Jenkins system, some of them from Washington to
Philadelphia, and represent the best work done in 1922, 1923, and 1924.
[Illustration: [Photographs]]
[Illustration: [Photographs]]
[Illustration: [Photographs]]
[Illustration: [Photographs]]
[Illustration: [Photographs]]
[Illustration: [Photographs]]