WHAT JOHN Baird did for the promotion of the mechanical television system in England, Zworykin did in the United States for an all-electronic colour television system (1925).

Early years

Vladimir Zworykin was born on July 30, 1889 in Maurom, Russia. He obtained in 1912 a degree in electrical engineering from the St. Petersburg Institute of Technology. He then went to the College de France, Paris to begin research work on X-rays under the famous physicist Paul Langerin (1872-1946), but returned to Russia in 1914. He served in the army as a radio officer.In 1910, he came under the tutelage of Boris Rosing, Professor in Charge of laboratory projects at the institute, who introduced Zworykin to his experiments of transmitting pictures by wire. Together, they exhibited a television system, using a mechanical scanner in the transmitter and an electronic tube in the receiver.Rosing disappeared during the Bolshevik Revolution (1917); but Zworykin escaped from Russia. He travelled widely and landed in the U.S. in 1919. He became an American citizen in 1924.Then he worked as a book-keeper to learn English. In 1920, he joined the Westinghouse Electric Corporation; shortly afterwards, he enrolled as a research student at the University of Pittsburgh. He graduated with a Ph.D degree in Physics in 1926, at the age of 37.

Iconoscope

Zworykin invented the iconoscope, the first electronic-scanning television camera. The principle was to focus an image on a screen made up of many photoelectric cells, each insulated, which developed a charge that depended on the intensity of the light at that point. An electron beam directed on the screen was scanned in parallel lines over the screen, discharging the photoelectric cells and producing an electrical signal.

Reconstruction of signals

Zworykin used the cathode-ray tube invented in 1897 by Karl Braun (1850-1918) to produce the image in a receiver. The Braun tube (called kinescope) had an electron beam focused by magnetic and electric fields to form a spot on a fluorescent screen.The beam was deflected by the fields in parallel lines across the screen, and the intensity of beam varied according to the intensity of the signal. In this way, it was possible to reconstruct the electrical signals into an image.With an early version of the system, Zworykin managed (1923) to transmit the simple picture of a cross.It was not until after he moved in 1929 to the Radio Corporation of America (RCA) that any real progress was made towards the commercial utilisation of his invention. RCA funded Zworykin's research. He made improvements to his iconoscope, allegedly using an imaging section, which was similar to the patent of P. T. Farnsworth (the farm boy to have conceived the basic principles of electronic television at the age of 13 years!). Patent litigation followed, with RCA paying Farnsworth royalties.By the mid-1930s it was clear that the future of television lay with such all-electronic systems, rather than the electro-mechanical scanner pioneered by John Baird (1888-1946). Zworykin died at the age of 93 (July 29, 1982).Zworykin was awarded in 1967 the National Medal of Science by the National Academy of Sciences and was included in 1977 in the U.S. National Inventors Hall of Fame.R. PARTHASARATHY