CRT beam landing spot size correction apparatus and method
AssigneesSony Corporation, Sony Electronics Inc.
InventorToshiyuki Ogura
Life of this patent
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Abstract
A 90 percent electron gun aperture astigmatism is used in conjunction with a four-pole electromagnet to make a CRT electron beam just focus point and minimum beam width occur closer to the same focus voltage. A single grid may have the 90 percent astigmatism, or astigmatisms in two or more grids may combine to produce an effective 90 percent astigmatism. A four-pole electromagnet is positioned around the focusing grid and current driving the electromagnet is varied with beam position during normal operation.
Claims11
An apparatus for correcting electron beam landing geometry in a cathode ray tube, the apparatus comprising:
- a source of electrons producing an electron beam;
- a plurality of grids, wherein each grid in the plurality of grids has a unique aperture and each grid in the plurality of grids is positioned such that the electron beam passes through each unique aperture, and wherein each unique aperture has an astigmatism such that the product of the astigmatisms of each unique aperture is substantially equivalent to a 90 percent astigmatism in a single aperture.
A method of correcting electron beam landing geometry in a cathode ray tube, the method comprising the acts of:
- providing a source of electrons for producing an electron beam;
- providing a plurality of grids, wherein each grid in the plurality of grids has a unique aperture and each grid in the plurality of grids is positioned such that the electron beam passes through each unique aperture, and wherein each unique aperture has an astigmatism such that the product of the astigmatisms of each unique aperture is substantially equivalent to a 90 percent astigmatism in a single aperture.
Dependencies are inferred from the claim text.