Cathode Ray Tube: The History
CRTs---or cathode ray tubes---are specialized vacuum tubes where images are created by using electron beams to strike a phosphorescent screen. The invention of the Geissler tube by the German glass blower Heinrich Geissler in 1855 produced the first permanently sealed discharge tube. This showed that gas flows when an electric current passes through it at a low pressure.
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Early Cathode Ray Technology
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In 1897, German physicist Karl Ferdinand Braun introduced a CRT that had a fluorescent screen. He made the first cathode ray tube scanning device, which became known as the cathode ray oscilloscope. It emitted a visible light when hit by a beam of electrons.
Cathode Ray Tubes Used In Televisions
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Russian scientist Boris Rosing used a CRT in the receiver of a television in 1907. The Rosing transmitter was the first one that made use of mirror-drum scanning--transmitting crude geometrical patterns onto the television screen. In 1931, Allen DuMont made the first commercially viable CRT for television.
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Components of a Cathode Ray Tube
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The design of CRTs consisted of an electron gun that first produces a narrow beam of electrons from the anodes. The deflecting coils in the CRT then generate an extremely low frequency electromagnetic field, allowing for a constant adjustment of the direction of the electron beam. The intensity of the beam differs and produces a small, bright and visible spot upon striking the phosphor-coated screen.
How CRT Produces Images On The Screen
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In order to create an image on a television screen or computer monitor, complex signals are applied to the deflecting coils and apparatus that controls the intensity of the electron beam. This races the spots across the screen in a sequence of horizontal lines called the raster. The scanning happens at a very fast rate, so the eye sees a constant image on the entire screen. When viewed in front, the spot moves similar to the eye movement upon reading single-column page text.
Decline and Resurgence of CRT
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In mid-2000, the demand for CRT began to decline due to its heavy size and the development of other display technologies. Consumers favored the thin, wall-mounted flat panels and found bulky CRTs impractical; however, in the first quarter of 2008, demand for CRT increased due to the decline and consolidation of plasma display producers. It has also become useful in displaying photos with high pixels, and is still favored in the printing and broadcasting industries.
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