Who Invented Television

by

R. J. Reiman, Historian

Inventors anticipated the public demand for television before the advent of radio broadcasting. So many participated in the development that it is impossible to answer the question "Who invented television?", but a few were so important as to be recognized as pioneers.

Paul Nipkow proposed the first practical mechanical scanner in Germany in 1884. The scanner was a rotating disk with holes arranged in a spiral around its edge. Light passing through the holes as the disk rotated produced a rectangular scanning pattern or raster which could be used to either generate an electrical signal from the scene for transmitting or to produce an image from the signal at the receiver. As the disk rotated, the image was scanned by the perforations in the disk, and light from different portions of it passed to a photocell. The number of scanned lines was equal to the number of perforations and each rotation of the disk produced a television frame. In the receiver, the brightness of the light source would be varied by the signal voltage. Again, the light passed through a synchronously rotating perforated disk and formed a raster on the projection screen. Mechanical viewers had the serious limitation of resolution and brightness.

John Logie Baird, a Scottish engineer-inventor, successfully promoted a television system based on the Nipkrow principle, received backing and sold transmitters and receivers. Laboratories in the United States and Great Britain worked to develop an all-electronic system. In Britain, the Electric and Musical Industries, Ltd., provided a system along with Baird's, and these were experimentally used to broadcast television programs by the BBC in November 1936. The EMI system won overwhelmingly. An American inventor, Charles Francis Jenkins, followed with a rotating ring whose thickness varied and increased around its circumference, forcing a rotating prism. By using two rings overlapping at right angles, a beam could be made to scan both horizontally and vertically, which unfortunately produced small, dim and fuzzy images. Jenkins' system, like Baird's, failed on the basis of poor quality.

AT&T first demonstrated a television system developed by one of Bell Lab's scientists, Herbert Ives, again based on the Nipkow disks. GE also demonstrated a mechanical system developed by Ernst Alexanderson. David Sarnoff, however, would turn to research for a successful electronic system.

In the 1920's, Alan A. Campbell-Swinton, a prominent electrical engineer in London, proposed a system that would use CRT's displaying the picture at the receiver, with electromagnetic scanning to form the raster. His transmitter tube, using a chamber filled with gas which could conduct electrons, was not suitable. Credit for the first practical TV signal-generator of pickup must be shared by Vladimir K. Zworykin and Philo T. Farnsworth, who invented the iconoscope and the image dissector respectively. Successful electronic TV would follow.