Cathode-ray tube
AssigneeU.S. Philips Corporation
InventorsJan Bijma, Henricus W. M. Linssen
Life of this patent
Estimating the term…
Abstract
By making the first grid of an electron gun for a cathode-ray tube to extend in the manner of a funnel in such manner that on the side of the second grid the aperture is elongate and mainly a quadrupole lens action is obtained, it is possible to obtain in the corners and at the edge of the display screen a spot which is surrounded by considerably less haze than the known construction having an elongate aperture in the first grid.
Claims15
A cathode ray tube comprising, in an evacuated envelope, an electron gun for generating an electron beam, said electron gun including a cathode centered about an axis, a first grid positioned adjacent said cathode and spaced therefrom along said axis and a second grid spaced along said axis from said first grid, said first and second grids each having a portion extending normal to said axis and having an aperture formed therethrough at said axis, the aperture in said first grid defining a first opening on the side thereof adjacent said cathode of a shape such that a substantially axially symmetric electric lens is formed in the region between said cathode and said first grid, said aperture of said first grid further defining a second opening on the side of said first grid adjacent said second grid, said second opening being elongated in a direction normal to said axis and having a cross-sectional area larger than the cross-sectional area of said first opening, so that said first and second grids form a non-rotationally symmetric electron lens in the region therebetween.
In a cathode ray tube having an electron gun, including a quadrupolar lens, for generating an electron beam, deflection means for deflecting said beam and a screen for producing a spot in response to said beam, said electron gun having a cathode, a first grid and a second grid spaced in that order, whereby no other electrodes are between said first grid and cathode, and wherein said first grid has an aperture for said beam that is shaped to compensate for the astigmatic effect of said quadrupolar lens;
- the improvement in said electron gun for reducing haze in said spot at the corners and edge of said screen wherein the end of said aperture in said first grid towards said cathode is substantially rotationally symmetrical and the end of said aperture towards second grid is elongated and has a cross-section greater than the end thereof towards said cathode grid.
Dependencies are inferred from the claim text.