okaforpeacee

@ladyprowess · 08 Dec 2021

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When was Coloured TV invented?

Colour television was an excited but not a new idea In the late 19th century. A Russian scientist by the name A.A.

Polumordvinov devised a system of spinning Nipkow disks and concentric cylinders with slits covered by red, green, and blue filters. But he was far ahead of the technology of the day; even the most basic black-and-white television was decades away. In 1928, Baird gave demonstrations in London of a colour system using a Nipkow disk with three spirals of 30 apertures, one spiral for each primary colour in sequence. The light source at the receiver was composed of two gas-discharge tubes, one of mercury vapour and helium for the green and blue colours and a neon tube for red.

The quality, however, was quite poor.
In the early 20th century, many inventors designed colour systems that looked sound on paper but that required technology of the future. Their basic concept was later called the “sequential” system.

They proposed to scan the picture with three successive filters coloured red, blue, and green. At the receiving end the three components would be reproduced in succession so quickly that the human eye would “see” the original multicoloured picture. Unfortunately, this method required too fast a rate of scanning for the crude television systems of the day. Also, existing black-and-white receivers would not be able to reproduce the pictures. Sequential systems therefore came to be described as “noncompatible.”

An alternative approach—practically much more difficult, even daunting at first—would be a “simultaneous” system, which would transmit the three primary-colour signals together and which would also be “compatible” with existing black-and-white receivers. In 1924, Harold McCreary designed such a system using cathode-ray tubes. He planned to use a separate cathode-ray camera to scan each of the three primary-colour components of a picture. He would then transmit the three signals simultaneously and use a separate cathode-ray tube for each colour at the receiving end. In each tube, when the resulting electron beam struck the “screen” end, phosphors coated there would glow the appropriate colour. The result would be three coloured images, each composed of one primary colour.

A series of mirrors would then combine these images into one picture. Although McCreary never made this apparatus actually work, it is important as the first simultaneous patent, as well as the first to use a separate camera tube for each primary colour and glowing colour phosphors on the receiving end. In 1929 Herbert Ives and colleagues at Bell Laboratories transmitted 50-line colour television images between New York City and Washington, D.C.; this was a mechanical method, using spinning disks, but one that sent the three primary colour signals simultaneously over three separate circuits.

1950 the FCC approved CBS’s colour television and corresponding broadcast standards for immediate commercial use. However, out of 12 million television sets in existence, only some two dozen could receive the CBS colour signal, and after only a few months the broadcasts were abandoned. Then, in June 1951, Sarnoff and RCA proudly unveiled their new system.

The design used dichroic mirrors to separate the blue, red, and green components of the original image and focus each component on its own monochrome camera tube.

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