Display device and cathode ray tube
AssigneeU.S. Philips Corporation
InventorLambert J. Stil
Life of this patent
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Abstract
A display device comprising a deflection unit and a cathode ray tube having an in-line electron gun. The electron gun comprises a main lens portion having means to generate a main lens field and a quadrupole field. During operation, the intensity of the fields is dynamically varied. The electron gun comprises a prefocusing lens portion having means of generating a prefocusing lens field and a further quadrupole field. During operation, the intensity of said fields is controlled so that a dynamic cylindrical lens is formed in the prefocusing lens portion. By virtue thereof, an improved picture reproduction can be obtained.
Claims10
A display device comprising a cathode ray tubed and a deflection unit, said cathode ray tube including an electron gun for producing a plurality of coplanar electron beams, said electron gun having a main lens portion, through which said beams pass, said display device including means for producing in said main lens portion a main lens field and a quadrupole lens field having dynamically varying strengths, characterized in that the display device further includes means for producing a cylindrical lens field having a dynamically varying strength through which said beams pass before entering the main lens portion, said cylindrical lens field effecting substantially no variation of the beam cross-sectional sizes in a first direction parallel to the plane of the beams while effecting a substantial variation of the beam cross-sectional sizes in a second direction transverse to said plane.
A cathode ray tube comprising an envelope supporting a luminescent screen and containing an electron gun for producing a plurality of coplanar electron beams for impinging on said screen, said electron gun having a main lens portion, through which said beams pass, and including means for producing in said main lens portion a main lens field and a quadrupole lens field having dynamically varying strengths, characterized in that the electron gun further includes means for producing a cylindrical lens field having a dynamically varying strength through which said beams pass before entering the main lens portion, said cylindrical lens field effecting substantially no variation of the beam cross-sectional sizes in a first direction parallel to the plane of the beams while effecting a substantial variation of the beam cross-sectional sizes in a second direction transverse to said plane.
Dependencies are inferred from the claim text.