| 摘要 |
PURPOSE:To prevent the scanning distortion of a beam even if a scanning speed is increaed during overscanning, by making the quantity of the beam greater during effective scanning than that during the overscanning. CONSTITUTION:A horizontal overscanning pulse PH is applied to a terminal 20, and a vertical overscanning pulse PV is applied to a terminal 21. Those pulses PH and PV are applied to a driving circuit 23 for the electrode G1 of an image pickup tube through an OR gate 22. Then, a beam control signal is applied to the electrode G1 of the image pickup tube from the G1 driving circuit 23 during an overscanning period to raise the voltage of the electrode G1, so the quantity of a beam is increased. Consequently, even when the scanning speed of the beam is increased, the beam is never saturated. For this purpose, the charge of the circumferential part of an effective scanning area is discharged sufficiently to eliminte the scanning distortion of the beam. |
