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Abstract

A linear motor drive system which is substantially not influenced by deviations in shape of slits, uneveness of distribution of light, and high order high harmonic components of a sensor signal, and which comprises a linear optical encoder having high sensor accuracy and which enhances the position detecting resolution of the encoder without use of high frequency clock generator.The system comprises means for detecting the movement of the slider of the linear pulse motor by use of a linear optical encoder and means for feedback control of the motor based on the sensor signal, wherein a photodiode array is extended over a plurality of rows of slits on a scale plate; a diffuser is mounted between a light source and the scale plate, and n photodiodes are provided within one pitch of the slit, the width of one photodiode in the direction of the array is set at p.sub.0 /(n+1), and the width of a gap between the photodiodes is set at p.sub.0 .multidot.n(n+1). In another embodiment, a phase modulating encoder is provided and the position of the slider is found with an average value of several measured values of phase differences between the phase modulated signal outputted from the encoder and to which a dither signal is added and the reference signal whose phase is not modulated.

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