Electrostatic deflection is commonly used in oscilloscopes. In modern CRT monitors and televisions the beams are bent by magnetic deflection, using a deflection yoke. In color devices, an image is produced by controlling the intensity of each of three electron beams, one for each additive primary color (red, green, and blue) with a video signal as a reference. In CRT television sets and computer monitors, the entire front area of the tube is scanned repeatedly and systematically in a fixed pattern called a raster. The term cathode ray was used to describe electron beams when they were first discovered, before it was understood that what was emitted from the cathode was a beam of electrons. CRTs have also been used as memory devices, in which case the screen is not intended to be visible to an observer. A CRT on a television set is commonly called a picture tube. The images may represent electrical waveforms ( oscilloscope), pictures ( television set, computer monitor), radar targets, or other phenomena. The only visible differences are the single electron gun, the uniform white phosphor coating, and the lack of a shadow mask.Ī cathode-ray tube ( CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen.
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