| 摘要 |
<p>A cathode-ray tube comprising in an evacuated envelope an electron gun for generating at least one electron beam which is focused on a display screen to form a spot and which is deflected in two mutually perpendicular directions so that a raster is written on the display screen. The electron gun comprises a cathode which is centered on an axis, a first grid at some distance therefrom along the axis and a second grid at some distance from the first grid, the first and second grids each having a part which is perpendicular to the axis and which comprises an aperture around the axis. The aperture in the first grid, on the side of the second grid, is elongate in a direction coinciding with one of the deflection directions and, on the side of the cathode, is elongate in a direction perpendicular to the elongate direction of the aperture on the side of the second grid. The dimensions and the depths of the portions of the aperture on the side of the second grid and on the side of the cathode are chosen so that, for the beam operating current range of the cathode-ray tube, substantially one cross-over is formed in an astigmatically-focused electron beam, thereby improving near the second grid, spot quality.</p> |
