| 摘要 |
PURPOSE: A beam index type cathode ray tube is provided to prevent a mis-match of the split screen of the cathode ray tube by minimizing influences of terrestrial magnetic field on the electron beam. CONSTITUTION: A beam index type cathode ray tube comprises a face panel(12) having a screen portion with an inner surface on which a phosphor screen is formed, and a skirt portion formed by bending, in a rearward direction, the circumference of the screen portion; a funnel coupled to the rear of the face panel, and which has one or more necks; electron guns mounted in each of the necks, and which scans electron beams to the area corresponding to the phosphor screen in accordance with the scanning direction; a plurality of deflection yokes mounted on the outer surface of the funnel, and which deflect electron beams emitted from the electron guns; index phosphors arranged on a black matrix; an optical detector mounted on the outer surface of the funnel, and which detects index signals generated from the index phosphors; a first coil unit(46) wound on the skirt portion along the outer surface of the face panel; second coil units(42a,42b) wound on the outer surface of the longer side skirt portion of the face panel; third coil units(44a,44b) wound on the outer surface of the shorter side skirt portion of the face panel; a terrestrial magnetic field sensor(52) for sensing the direction and intensity of the terrestrial magnetic field affecting the cathode ray tube; and a terrestrial magnetic field correction unit(50) connected to the first, second and third coil units and the terrestrial magnetic field sensor, and which generates a correcting magnetic field having an intensity similar to the intensity of the terrestrial magnetic field sensed by the terrestrial magnetic field sensor and a direction opposite from the direction of the terrestrial magnetic field.
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