| 摘要 |
PURPOSE: A beam index type cathode ray tube is provided to obtain a fine beam diameter by reducing the divergence effect of electron beam emitted from the main focus lens toward the phosphor screen. CONSTITUTION: A beam index type CRT comprises a phosphor screen(2) formed on an inner surface of a panel(4), and which has an index stripe(20); a funnel(6) coupled to a rear surface of the panel, and which has a transparent light receiving window(6a); an electron gun(10) mounted at an inner periphery of a neck part(8) extended from the funnel, and which has a cathode and a plurality of electrodes, and emits electron beams toward the phosphor screen; an optical detector(12) attached to the outer surface of the light receiving window, and which detects an index light emitted from the index stripes; an index circuit part(14) for converting the electrical signal detected by the optical detector into an index signal, synchronizing the index signal with a color signal and transmitting the correct color signal to the electron gun; and a unit for permitting the electron beam to have a fine beam diameter by controlling an equipotential line formed in the portion of the main focus lens opposed to the phosphor screen.
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