Patent ID: 7301348

Claim:
An electrostatic encoder comprising: a scale; a sensor head provided to face the scale, and movable relative to the scale in a predetermined direction; a pair of receiving coupling electrodes formed on the scale, and extending in the predetermined direction; transmitting coupling electrodes provided on the sensor head, and located to face the pair of receiving coupling electrodes; digital electrodes provided on the scale to extend from the receiving coupling electrodes in a direction perpendicular to the predetermined direction, and arranged at a predetermined pitch; two pairs of interdigital electrodes provided on the sensor head, and located to face the digital electrodes of the scale; a voltage applying portion configured to apply an alternating voltage to the transmitting coupling electrodes; and a potential difference detecting portion configured to detect a potential difference between the interdigital electrodes of each of the two pairs of interdigital electrodes of the sensor head, wherein the two pairs of interdigital electrodes of the sensor head are arranged at the same pitch, and said each pair of interdigital electrodes are spaced apart from each other by a predetermined distance in the predetermined direction.