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cathode ray tube (CRT)

Cathode ray tubes (CRT), also commonly referred to as electron beam tubes, are the components on which the image is displayed. It is therefore the central display component of screens, monitors and televisions.

Electron beam tubes consist of an emitting system, the cathode which generates the electron beam, a focusing and deflecting system in which the electron beam is focused and deflected in vertical and horizontal directions, the accelerating system and the phosphor screen. The acceleration system ensures that the electron beam hits the luminescent screen at a certain speed and triggers a light emission there. The phosphor screen is coated with phosphor, which emits light when electrons strike it.

The structure explained refers to monochrome screens; in color screens, the structure is in triplicate, since the electron beams for the colorsred (R), green (G) and blue (B) are generated individually, controlled in brightness, focused and deflected. All color cathode ray tubes work with additive color mixing according to the RGB color model.

Structure of a color cathode ray tube (CRT)

Structure of a color cathode ray tube (CRT)

The luminescent screen of color CRTs differs from monochrome CRTs. It consists of individual color phosphors that are distributed in dots or stripes across the luminescent screen. The electron beam for a particular color may only hit the corresponding color phosphor. This is ensured by a mask that is placed directly behind the luminescent layer. Depending on the process, this mask has small holes, known as the shadow mask, small slits, or it consists of thin strips, known as the strip mask, known as the trinitron tube.

Pinhole mask technique

Pinhole mask technique

Most frahling techniques use raster imaging. Here, the electron beam scans the luminescent screen periodically, line by line from left to right and frame by frame from top to bottom. The display on the screen is controlled by brightness. The inertia of the human eye and the afterglow of the phosphors benefit human perception.

Another display technology that also uses emitting electrons is the SED display, but this is a flat screen.

Informations:
Englisch: cathode ray tube - CRT
Updated at: 13.12.2008
#Words: 332
Links: beam, image, display, system, focusing
Translations: DE
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