| 摘要 |
PURPOSE:To prevent images from degrading even tough scanning line intervals are changed by allowing the spot sizes of electron beams to change in conformity with the variation of scanning line intervals. CONSTITUTION:Change over switches 6 are provided between electron beam focusing electrodes of a pickup tube 1 and an electron beam focusing power source 5 interlocked with the operations of a switch 4. Whenever the scanning line intervals are changed over by the switch 4, the connections of the electron beam focusing power source 5 are automatically changed so that the variations of focusing voltages permit the spot sizes of the electron beams to be changed over. In other words, such automatic adjustment operations include: if the scanning line interval (d) is changed over wider, the spot size (r) becomes larger and on the contrary to above situations, if its intervals (d) is changed over narrower, its spot size becomes smaller. As a result, the above satisfactory situations are maintained in all cases.
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