Importance

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Abstract

The disclosure relates to an apparatus and method for forming a scanning electron beam for use in a flat screen cathode ray tube device. An analog addressing method enables scanning of one axis of the screen of the CRT device. During scanning, all portions of a sheet of electrons emitted by a line cathode are deflected at any given time and blocked by an analog horizontal-positioning deflection grid except for one narrow portion disposed along the length of the line cathode. At the one portion, a narrow beam of electrons is formed. The grid contains an address plate and a load plate. The load plate creates a voltage gradient causing each location along its horizontal axis to be at a distinct voltage. Horizontal scanning is accomplished by applying a varying central voltage to the address plate. This varying voltage will be matched by an equal voltage at a single predetermined location along the horizontal axis of the load plate adjacent to which electrons can pass undeflected in the form of a beam. At all other locations along the horizontal axis, unequal voltages on the plates deflect electrons in the sheet passing between them and cause the electrons to be blocked. Vertical scanning is accomplished by varying the voltage difference between two parallel vertical deflection plates between which the scanned electron beam passes. The disclosure also relates to the use of electromagnetic rather than electrostatic deflections in producing a scanning electron beam from a line cathode. In addition, the disclosure relates to multiple beams for scanning and producing of color images.

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First Claim