Chromatron

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Sony Chromatron color television

At the beginning of the 1950s, the Radio Corporation of America (RCA) brought a compatible electronic color television system to series production, which could reproduce usable color images with the help of a shadow mask picture tube when the normal black and white video bandwidth was exhausted. Three electron beams were modulated with the color video signals, the shadow mask , each with a hole for a color triple behind it on the screen, mechanically ensured that the electron beams transmitted at different angles of incidence hit the corresponding color phosphor. The 15-inch color picture tube 15GP22 used at that time achieved a maximum deflection angle of 45 ° for the picture width. Extensive convergence correction circuits were necessary so that the three color images on the screen came together. The luminescent materials were so faint that the room had to be darkened for color television . In addition, a good 80% of the beam power was absorbed by the shadow mask and converted into heat.

Ernest O. Lawrence developed from 1951 Chromatron - color picture tube , which with improved brightness compared to the shadow mask picture tube should make do with only one electron gun instead of three electron guns. The three phosphors for the primary colors red, green and blue were attached to the screen instead of color triples in the form of vertical color stripes. Fine, vertical wires were attached behind the colored strips inside the tube, which were supposed to statically deflect the electron beam onto the red, green or blue phosphor by means of an electrical control pulse. Since only one electron beam was used for the three primary colors, the complex convergence circuits as in the case of the shadow mask picture tube were also omitted, and the tube could work with an enlarged deflection angle of 72 ° (instead of 45 ° as in the first shadow mask picture tube).

However, the technicians could not get the associated problems under control, the fine wire threads in front of the screen could not be held stable enough in their position, the high control voltages of up to 8  kV led to arcing in the picture tube, so that it was never mass-produced came.

The Japanese company SONY experimented with the Chromatron at high cost in the 1960s, but finally abandoned the idea, but based on it developed the Trinitron picture tube , which took over the light strips and the fine vertical wires instead of a shadow mask from the Chromatron nevertheless with three separate cathodes, but now worked in an electron system for the three primary colors.

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