| 摘要 |
<p>RCA 76,325 An apparatus for sensing electron beam focus on the display screen of a kinescope comprises a photodiode adapted to detect the light output from an area on the kinescope display screen. A signal having a frequency equal to the scanned excitation rate of the individual screen phosphor element areas being excited by a deflected electron beam is developed from the photodiode output. The variation in the amplitude of this signal is an indication of electron beam focus condition.</p> |
