| 摘要 |
<p>The tube has an in-line electron gun directing three electron beams through a shadow mask on to the phosphor screen. In order to improve coincidence of the three rasters by reducing coma distortion a shield cup (20) is fitted over the end of the electron gun and has apertures (22, 23, 24) in the bottom (21) of the cup for the three beams. High permeability magnetic members may be arranged on the cup bottom (21) to act as field control members. In order to avoid mis-convergence due to coma distortion even at high deflection frequencies the present invention provides narrow cuts (25) radiating from the apertures (23, 24) for the outside electron beams. Cuts may also be provided in field control members round these apertures. </p> |
