| 摘要 |
<p>The invention relates to a cathode ray tube having an electron gun (10) which is provided with a so-called Aberration Reducing Triode (15). The ART (15) pre-focuses the electron beam (EB) such that outer rays in the pre-focus lens (20) are near the center of the electron beam (EB) in the main lens (30). Spherical aberrations are reduced, thereby. However, under given circumstances, moirepattems can appear in the image formed on the display screen (50), especially in parts of the image having a low brightness. According to the present invention, the pre-focus lens (20) in the ART (15) is arranged such that the pre-focusing effect thereof is reduced when the beam current of the electron beam (EB) is below a predetermined threshold beam current. This reduces or eliminates the moirepattems.</p> |
