| 摘要 |
PURPOSE:To attain accurate and quick adjustment by applying a measuring voltage deviated respectively toward positive/negative value from a voltage of the predicted nearly best focaus point, measuring the focus quantity and obtaining the best focus voltage through the arithmetic operation. CONSTITUTION:Plural different measuring voltage deviated respectively toward the positive/negative value from the voltage of the predicted nearly best focal point are generated with switching from a measuring voltage generating section 54 of a process processing circuit 5 and they are applied to a focus electrode of a cathode ray tube 1 via the focus voltage generator 4. The focus of the pattern displayed on the cathode ray tube 1 is measured by a pattern size measuring section 55 in matching with the voltage changeover timing. A main arithmetic section 56 obtains a vicinity voltage including the best focus voltage point by each data representing the measured value and the data representing each measured voltage.
|
