| 摘要 |
PROBLEM TO BE SOLVED: To prevent the distorsion of an image to avoid a measurement error, and hold Z-directional high rigidity without extending a scanner by calculating and correcting the circular displacement in vertical direction by the circular scanning of a piezoelectric scanner. SOLUTION: A Z-directional circular displacement arithmetic part 10 determines the Z-directional circular displacement errorΔh by use of the sensor output and the displacement detected values from X, Y displacement sensors. Sensors for detecting the Z-directional displacement are provided in three positions of the center and X, Y directions of a cylindrical piezoelectric scanner within the X, Y planes of the scanner, and the correction quantity is determined on the basis of their detected displacements and the X, Y-directional displacements, and a compensating quantity is added to the applied voltage from a Z-directional servo control system to correct the Z-displacement circular error. The Z-directional applied voltage to the piezoelectric scanner is regulated and controlled by the Z-servo control system, whereby the Z- directional measurement error is corrected. Since the Z-directional displacement error by the circular displacement of the scanner 6 is calculated, converted into a corrected voltage, and applied to an electrode 7 to perform a feedback control, the Z-directional circular displacement error can be removed.
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