| 摘要 |
PURPOSE:To correct deterioration in focus due to changes of beam current by using simple constitution by shunting a power source current of a high tension generating circuit and flowing to the correcting coil of a focusing device. CONSTITUTION:In a cathode-ray tube, a convergent magnetic field is generated by a convergent magnetic field generating device 2 to converge an electron beam. The power source current IH of a high tension generating circuit 6 changed by beam current Ib is adjusted by a resistance 10 for adjusting correcting current so as to set it to the optimum correcting current value in the direction of current in the same direction as a convergent magnetic field generated by a main coil 3 and let flow. Thereby, deterioration in focus due to changes of beam current Ib is corrected. As the most suitable focusing condition can be maintained without depending on changes of beam current, a display picture of high quality can be obtained by this constitution.
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