Video camera tube

In older video cameras, before the mid to late 1980s, a video camera tube or pickup tube was used instead of a charge-coupled device (CCD) for converting an optical image into an electrical signal. Several types were in use from the 1930s to the 1980s. The most commercially successful of these tubes were various types of cathode ray tubes or "CRTs".Any vacuum tube which operates using a focused beam of electrons ("cathode rays") is known as a cathode ray tube. However, in the popular lexicon "CRT" usually refers to the "picture tube" in a television or computer monitor. The proper term for this type of display tube is kinescope, only one of many types of cathode ray tubes. Others include the tubes used in oscilloscopes, radar displays, and the camera pickup tubes described in this article.



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                 The  word "kinescope" has also become the popular name for a film recording made by focusing a motion picture camera onto the face of a kinescope cathode ray tube, a common practice before the advent of video tape recordingVideo camera tubes typically had a certain maximum brightness tolerance. If that limit were exceeded, such as by pointing the camera at the sun, sun-reflecting shiny surfaces, or extremely bright point light sources, the tube detecting surface would instantly "burn out" and be rendered insensitive on part or all of the screen. The only remedy was replacing the video tube.In June 1908, the scientific journal Nature published a letter in which Alan Archibald Campbell-Swinton, fellow of the Royal Society (UK), discussed how a fully electronic television system could be realized by using cathode ray tubes (or "Braun" tubes, after its inventor, Karl Braun) as both imaging and display devices.But Campbell-Swinton noted that the "real difficulties lie in devising an efficient transmitter", and that it was possible that "no photoelectric phenomenon at present known will provide what is required".He later expanded on his vision in a presidential address given to the Röntgen Society in November 1911. The photoelectric screen in the proposed transmitting device was a mosaic of isolated rubidium cubes.This concept for a fully electronic television system was later popularized by Hugo Gernsback as the "Campbell-Swinton's Electronic Scanning System" in the August 1915 issue of the popular magazine Electrical Experimenter.In a letter to Nature published in October 1926, Campbell-Swinton also announced the results of some "not very successful experiments" he had conducted with G. M. Minchin and J. C. M. Stanton. They had attempted to generate an electrical signal by projecting an image onto a selenium-coated metal plate that was simultaneously scanned by a cathode ray beam.These experiments were conducted before March 1914, when Minchin died, but they were later repeated by two different teams in 1937, by H. Miller and J. W. Strange from EMI. and by H. Iams and A. Rose from RCA.

 Both teams succeeded in transmitting "very faint" images with the original Campbell-Swinton's selenium-coated plate, but much better images were obtained when the metal plate was covered with zinc sulphide or selenide,or with aluminum or zirconium oxide treated with caesium.Nevertheless, there is no evidence that Campbell-Swinton ever considered using zinc compounds instead of selenium in the transmitting device. A description of a CRT imaging device also appeared in a patent application filed by Edvard-Gustav Schoultz in France in August 1921, and published in 1922.