| 摘要 |
<p>A colour display tube comprising an in-line electron gun which has a first and a second lens electrode which produce an electron-optical lens field for focusing the electron beams on a display screen of the cathode ray tube, one of said lens electrodes having a correction element (29) for correcting the astigmatism of the lens field, the correction element having three apertures (30,31,32), the outer apertures of which are formed such that, in operation, an electric field having a six-pole component is generated for the outer electron beams in the correction element. As a result thereof, the outer electron beams produce an improved image on the display screen. The six-pole fields generated in the correction element correct the negative effect of six-pole fields occurring in the lens field. In an embodiment, the outer apertures (30,32) are in the shape of a trapezium. <IMAGE></p> |
