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The cathode ray tube (CRT) is a vacuum tube containing one or more electron guns, and a phosphorescent screen used to view images.〔(【引用サイトリンク】title=History of the Cathode Ray Tube )〕 It has a means to accelerate and deflect the electron beam(s) onto the screen to create the images. The images may represent electrical waveforms (oscilloscope), pictures (television, computer monitor), radar targets or others. CRTs have also been used as memory devices, in which case the visible light emitted from the fluorescent material (if any) is not intended to have significant meaning to a visual observer (though the visible pattern on the tube face may cryptically represent the stored data). The CRT uses an evacuated glass envelope which is large, deep (i.e. long from front screen face to rear end), fairly heavy, and relatively fragile. As a matter of safety, the face is typically made of thick lead glass so as to be highly shatter-resistant and to block most X-ray emissions, particularly if the CRT is used in a consumer product. Since the mid 2000s, CRTs have largely been superseded by newer display technologies such as LCD, plasma display, and OLED, which have lower manufacturing costs, power consumption, weight and bulk. The vacuum level inside the tube is high vacuum on the order of 〔(Topic 7 | The Cathode-Ray Tube ). aw.com. 2003-08-01〕 to 〔(repairfaq.org – Sam's Laser FAQ – Vacuum Technology for Home-Built Gas Lasers ). repairfaq.org. 2012-08-02〕 In television sets and computer monitors, the entire front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster. An image is produced by controlling the intensity of each of the three electron beams, one for each additive primary color (red, green, and blue) with a video signal as a reference.〔(【引用サイトリンク】url=http://computer.howstuffworks.com/monitor7.htm )〕 In all modern CRT monitors and televisions, the beams are bent by ''magnetic deflection'', a varying magnetic field generated by coils and driven by electronic circuits around the neck of the tube, although electrostatic deflection is commonly used in oscilloscopes, a type of diagnostic instrument.〔 ==History== Cathode rays were discovered by Johann Hittorf in 1869 in primitive Crookes tubes. He observed that some unknown rays were emitted from the cathode (negative electrode) which could cast shadows on the glowing wall of the tube, indicating the rays were traveling in straight lines. In 1890, Arthur Schuster demonstrated cathode rays could be deflected by electric fields, and William Crookes showed they could be deflected by magnetic fields. In 1897, J. J. Thomson succeeded in measuring the mass of cathode rays, showing that they consisted of negatively charged particles smaller than atoms, the first "subatomic particles", which were later named ''electrons''. The earliest version of the CRT was known as the "Braun tube", invented by the German physicist Ferdinand Braun in 1897.〔Ferdinand Braun (1897) ("Ueber ein Verfahren zur Demonstration und zum Studium des zeitlichen Verlaufs variabler Ströme" ) (On a process for the display and study of the course in time of variable currents), ''Annalen der Physik und Chemie'', 3rd series, 60 : 552-559.〕 It was a cold-cathode diode, a modification of the Crookes tube with a phosphor-coated screen. In 1907, Russian scientist Boris Rosing used a CRT in the receiving end of an experimental video signal to form a picture. He managed to display simple geometric shapes onto the screen, which marked the first time that CRT technology was used for what is now known as television.〔 The first cathode ray tube to use a hot cathode was developed by John B. Johnson (who gave his name to the term Johnson noise) and Harry Weiner Weinhart of Western Electric, and became a commercial product in 1922. It was named by inventor Vladimir K. Zworykin in 1929.〔Albert Abramson, ''Zworykin, Pioneer of Television'', University of Illinois Press, 1995, p. 84. ISBN 0-252-02104-5.〕 RCA was granted a trademark for the term (for its cathode ray tube) in 1932; it voluntarily released the term to the public domain in 1950.〔"RCA Surrenders Rights to Four Trade-Marks," Radio Age, October 1950, p. 21.〕 The first commercially made electronic television sets with cathode ray tubes were manufactured by Telefunken in Germany in 1934.〔(Telefunken ), Early Electronic TV Gallery, Early Television Foundation.〕〔(1934–35 Telefunken ), Television History: The First 75 Years.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cathode ray tube」の詳細全文を読む スポンサード リンク
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