Encoder output signal correction apparatus and method

摘要

A third harmonic distortion corrector is equipped for correcting a third harmonic distortion contained in a two-phase sinusoidal signals with different phases output from an encoder. A third harmonic calculator/detector calculates the amplitude a₃ and the phase phi₃ of the third harmonic using Fourier analysis, based on change in radius r of the Lissajous waveform output from a r-theta converter. The third harmonic distortion corrector corrects the third harmonic distortion of the two-phase sinusoidal signal A 4, B 4 based on the amplitude a₃ and the phase phi₃ of the third harmonic calculated.