| 摘要 |
PROBLEM TO BE SOLVED: To detect and adjust an error or deviation, with the passage of time, of a displacement amount detection device (encoder).SOLUTION: A displacement amount detection device comprises: first and second detection heads outputting two-phase signals having a phase difference of 90° outputted in accordance with relative movement with respect to a scale part 20 with which scales of a wavelengthλare formed; and error detection/evaluation means for detecting and evaluating an error of the displacement amount detection device. The error detection/evaluation means adds or subtracts balanced modulated signals obtained by modulating the two-phase signals having the phase difference of 90° with quadrature signals in a frequency (f). An amplitude and a deflection angle of information for each error factor are obtained by being separated and extracted, as sinusoidal signals of a fundamental term and a high-order term of the wavelengthλpeculiar for an error factor deteriorating a signal definition of the two-phase signals, from envelope information of an amplitude component of a resultant phase modulation signal or from amplitude information obtained by performing polar coordinate transformation on the two-phase signals. The amplitude and the deflection angle are evaluated in comparison with an amplitude and a deflection angle for each term which is set with an interpolation error allowable for the displacement amount detection device as a reference. |
