| 摘要 |
<p>An apparatus for correcting electron-beam alignment comprises monitoring means for monitoring the shading of the electro-optical tube image, adjustment means for decreasing the tube target bias voltage so that a measurable shading is introduced in the tube image, as monitored by the monitoring means, and control means for varying the tube alignment until the monitoring means monitors a minimum average shading, which condition is considered to indicate optimum beam alignment. In an apparatus for setting the beam current the beam current is switched off during fields scans so that the target charge excedes that produced by the operationel peak light level. The beam current is adjusted so as to discharge this increased target charge. Preferably, the camera tube is subjected to the operational peak light level and the beam current is switched off for two consecutive fields scans. This ensures that the target charge is at least twice that produced by the operational peak light level and that both odd and even fields are alternately discharged. </p> |
