| 主权项 |
1. A displacement detection apparatus comprising:
a scale unit having a measurement plane provided with at least two track units having a scale whose repetition pitch is constant, wherein pitch directions, which are directions in which the repetition pitch in each of the at least two track units is the shortest, are different from one another; and a detection head unit having at least three or more detection units configured to read the scale and to output a signal in accordance with the read scale, wherein one of the at least two track units is a reference track unit and for the reference track unit, the at least one detection unit is arranged in opposition thereto, the remaining track unit (s) of the at least two track units is a sub-track unit, for the sub-track unit, the at least one detection unit is arranged in opposition thereto, and when the scale unit and the detection head unit move relatively along the measurement plane of the scale unit, the at least three or more detection units detect displacement in two orthogonal directions on a plane parallel to the plane along which the detection head unit moves. |
