| 摘要 |
PROBLEM TO BE SOLVED: To obtain a dynamic focus correction circuit capable of surely performing the optimum correction of spot shape with a simple configuration. SOLUTION: The dynamic focus correction circuit is provided with a current detection means 20 that detects a peak value and a bottom value of a current flowing through an electromagnetic quadrupole coil 8, a control means 50 that supplies a prescribed peak control variable and a prescribed bottom control variable to a first power supply section and a second power supply section respectively, the first power supply section 16 that is connected to other terminal of a first chock coil 2, applies feedback control to a supplied current on the basis of the peak value detected by the current detection means 20 and the peak control variable supplied from the control means 50, and the second power supply section 17 that is connected to other terminal of a second chock coil 9, applies feedback control to a supplied current on the basis of the bottom value detected by the current detection means 20 and the bottom control variable supplied from the control means 50.
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