| 摘要 |
<p>A television camera tube comprising in an evacuated envelope (1) a diode electron gun for generating an electron beam, comprising, centred along an axis (20) successively, a cathode (33) having an emissive surface (37) extending substantially at right angles to the said axis, an anode (10) having a flat part (105) which extends substantially at right angles to the axis and having in its centre a portion (106) which extends in the direction of the cathode and whose inner and outer walls (107, 108) converge to the axis (20), which outer wall (108) changes into an apical surface (109) which is substantially parallel to the emissive surface (37) and which has a central aperture (110). If a flat electrode which is electrically connected to the anode is connected at a distance d from the apical surface on the side of the anode remote from the cathode, d being between 4 and 25 times the distance from the apical surface (109) to the emissive surface (37), which flat electrode (102) has a central aperture (133) which has a diameter which is substantially equal to the diameter of the electron beam at the area of the electrode, the return beam (100) passing through the diaphragm (9) with small deflection angles of the electron beam in the non-focused condition is captured by said flat plate-shaped electrode (102) and the number of secondary electrons varies to a considerably lesser extent than without said plate-shaped electrode (102). The observability of interference signals is reduced thereby.</p> |
