Flat-panel displays can also be made in very large sizes whereas 40 in (100 cm) to 45 in (110 cm) was about the largest size of a CRT. Since the mid-late 2000's, CRTs have been superseded by flat-panel display technologies such as LCD, plasma display, and OLED displays which are cheaper to manufacture and run, as well as significantly lighter and less bulky. CRTs make up most of the weight of CRT TVs and computer monitors.
The face is typically made of thick lead glass or special barium-strontium glass to be shatter-resistant and to block most X-ray emissions. As such, handling a CRT carries the risk of violent implosion that can hurl glass at great velocity.
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The interior is evacuated to 0.01 pascals (1 ×10 −7 atm) to 0.1 micropascals (1 ×10 −12 atm) or less, to facilitate the free flight of electrons from the gun(s) to the tube's face without scattering due to collisions with air molecules. Ī CRT is a glass envelope which is deep (i.e., long from front screen face to rear end), heavy, and fragile. 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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