| 摘要 |
<p>PHN 10.896 9 20.6.1984 Display tube. A display tube comprising in an evacuated envelope (1) an electron gun system (6) for generating and focusing by means of a focusing lens at least two electron beams (28 to 35) on a display screen (5), which electron beams are deflected by deflection means and describe a frame on the display screen. The electron gun system (6) comprises at least two electron sources (20 to 26) the electrons of which in each electron beam are accelerated immediately after the electron source by means of an electric field having a field strength exceeding 600 V/mm, the central paths (36) of the electron beams extending substantially parallel to each other, all beams being converged by the focusing lens in or in the immediate proximity of the focus of the focusing lens, after which each separate beam is focused on the display screen by the focusing lens to form a spot also in the case of deflection by the deflection means. The astigmatism and the coma of the focusing lens, especially for objects not situated on the axis, decreases rapidly with decreasing object potential with the beam aperture angle being kept the same. The electrons leaving the source at a low potential are then accelerated in a strong electric field exceeding 600 V/mm. In this manner, nearly immediately after the electrons have left the electron source, a very slim electron beam is obtained which maintains its slimness up to the display screen. The effect of the field curvature of the focusing lens is also considerably reduced by said slim beams. If all electron beams through the focusing lens converge in or in the immediate proximity of the focus of the focusing lens, a minimum of aberrations as a result of the deflection is obtained. The electron sources are preferably P-N cathodes or diode electron guns.</p> |
