Success in sending pictures by radio from flat photographs and receiving
them on flat photo negative plates (and subsequently of radio vision),
really began with the perfection of automatic machines for the making of
these prismatic rings, for by means of these prisms and a light
sensitive cell at the sending station the light values which make up the
picture are converted into electrical values, and broadcast.
So to put this picture on a radio carrier wave we simply slice up the
picture (figuratively) into slices one-hundredth of an inch in width, in
the best pictures, by sweeping the picture across the light sensitive
cell by means of these rotating prismatic rings. With each downward
sweep the picture is moved one-hundredth of an inch to the right until
the whole picture has crossed the cell, the cell converting the light
strengths of the different parts of each such slice into corresponding
electrical values.
The process very much resembles a bacon slicer in the market, each slice
showing fat and lean. Similarly these imaginary slices of our picture
show light and dark parts, and these lights and shadows moving across
the sensitive cell produce corresponding strength of electric current,
modulating the radio carrier wave of the broadcasting set accordingly.
Further, of course, it is immaterial whether the current modulation is
taken directly from a flat photograph, from a solid object, or from an
outdoor scene at which the transmitter is pointed.