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US 5,489,824 AGranted
Deflection system with a controlled beam spot
AssigneeRCA Thomson Licensing Corporation
InventorsMichael D. Grote, Jeffrey P. Johnson, Dennis J. Bechis
Life of this patent
Estimating the term…
Abstract
A deflection apparatus produces a field gradient that reduces a tendency of a major axis of a beam spot to become elongated at each corner, at each end of a horizontal axis and at each end of a vertical axis of a display screen relative to the beam spot at the center of the display screen. A beam spot stigmator causes the beam spot to be substantially anastigmatic at each of the corners, the end of the horizontal axis and the end of the vertical axis of the display screen.
Claims10
A deflection apparatus, comprising:
- a cathode ray tube including an evacuated glass envelope, a display screen disposed at one end of said envelope and an electron gun assembly disposed at a second end of said envelope, said electron gun assembly producing an electron beam that forms a beam spot at each of electron beam landing locations on said screen;
- a first horizontal deflection coil for producing a first horizontal deflection field and a first vertical deflection coil for producing a first vertical deflection field in a main deflection region of a beam path of said electron beam that varies in a manner to vary the electron beam landing location of said beam spot such that a shape of said beam spot tends to become distorted when said beam spot is at a first beam landing location relative to when said beam spot is at a second beam landing location;
- means for producing in a first region of said beam path a first nonuniform field containing a time varying field portion not produced by any of said first horizontal and said first vertical deflection coils, said first nonuniform field producing an electron beam lensing action with respect to a cross section of said electron beam in said first region in a manner that varies in accordance with beam landing location for substantially reducing the tendency of said beam spot to become distorted;
- and
- a beam spot stigmator for producing a time varying, second nonuniform field that varies in accordance with beam landing location in a second region of said beam path that is at a different distance from said display screen than said first region, for producing an electron beam lensing action with respect to a corresponding cross section of said electron beam in said second region in a manner that varies in accordance with beam landing location to maintain said beam spot anastigmatic when said beam spot is at each of said first and second beam landing locations.
2 more elements
A deflection apparatus, comprising:
- a cathode ray tube including an evacuated glass envelope, a display screen disposed at one end of said envelope and an electron gun assembly disposed at a second end of said envelope, said electron gun assembly producing an electron beam that forms a beam spot at each of electron beam landing locations on said screen;
- a plurality of deflection coils including a first horizontal deflection coil for producing a first horizontal deflection field and a first vertical deflection coil for producing a first vertical deflection field in a main deflection region of a beam path of said electron beam that varies in a manner to vary the electron beam landing location of said beam spot such that a shape of said beam spot tends to become distorted when said beam spot is at a first beam landing location relative to when said beam spot is at a second beam landing location, said plurality of deflection coils producing in a first region of said beam path a first nonuniform field containing a time varying field portion, said first nonuniform field producing an electron beam lensing action with respect to a cross section of said electron beam in said first region in a manner that varies in accordance with beam landing location for substantially reducing the tendency of said beam spot to become distorted;
- and
- a beam spot stigmator for producing a time varying, second nonuniform field that varies in accordance with beam landing location in a second region of said beam path that is at a different distance from said display screen than said first region, for producing an electron beam lensing action with respect to a corresponding cross section of said electron beam in said second region in a manner that varies in accordance with beam landing location to maintain said beam spot anastigmatic when said beam spot is at each of said first and second beam landing locations.
1 more element
Dependencies are inferred from the claim text.