Displacement detection apparatus and method of correcting error of scale used for displacement detection apparatus

A displacement detection apparatus comprising:

• a scale on which a plurality of marks are periodically disposed;
• a first position detection sensor and a second position detection sensor configured to detect positions of the marks;
• and
• a processor configured to perform a calculation processing of an output signal from each of the first position detection sensor and the second position detection sensor,
• wherein the first position detection sensor and the second position detection sensor are disposed at a distance L from each other in a relative movement direction so as to be movable relative to the scale, and
• wherein the processor calculates a correction value P′ of a mark pitch P of the plurality of marks using the distance L, a first time TPK required for K marks of the plurality of marks to pass a detection position by one of the first position detection sensor and the second position detection sensor, and a second time TL required for a specific mark of the plurality of marks, which is measured at the same time of the measurement of the first time TPK, to move the distance L.