Patent ID: 6879405

Claim:
A displacement pickup comprising: a movable scale having defined thereon a first area where positional information is recorded with a predetermined pitch and a second area where positional information is recorded with a pitch different from that in the first area; a first reading means for reading the positional information recorded in the first area; a first phase detecting means for detecting a first phase on the basis of the positional information read by the first reading means; a second reading means for reading the positional information recorded in the second area; a second phase detecting means for detecting a second phase on the basis of the positional information read by the second reading means; a phase comparing means for comparing the first and second phases with each other; and a signal selecting means for generating a plurality of signals according to a result of the comparison from the phase comparing means and selecting an arbitrary one of the plurality of signals on the basis of the positional information read by the first reading means, the first and second areas being formed on the scale to be displaceable equal distances in the same measuring direction.