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.
The rear of a 14-inch color cathode-ray tube showing its deflection coils and electron guns Typical 1950s United States monochrome television set Snapshot of a CRT television showing the line of light being drawn from left to right in a raster pattern Animation of the image construction with interlacing method Color computer monitor electron gunĪ 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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