| 摘要 |
PURPOSE:To simplify the constitution of a phase detector to obtain precise position information which does not include an interpolation error, by eliminating the interpolation error from detected information in accordance with a preliminarily stored interpolation error. CONSTITUTION:The clock of a clock generator 10 of a phase detector of the DPM system is inputted to an exciting wave oscillator 11, and an exciting wave S11 having a period T is generated and is inputted to a phase detector 12. The exciting wave S11 is converted to a phase by the detector 12 to obtain a position phase wave S12, and the phase of this phase wave S12 and that of said wave S11 are compared with each other by a phase comparator 13 to output a phase difference signal S13. This phase difference signal S13 is operated by a position computing element 14 to obtain position information having a phase difference of a prescribed period or shorter, and this position information is stored preliminarily in an interpolation error storage device 21. Position information obtained by the computing element 14 is corrected with the interpolation error stored in the storage device 21 by a position compensator 22, and precise position information is applied to a position integrator 15.
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