| 摘要 |
A scale 2 has marks S1 whose pitch interval changes along a measurement direction X1 in a manner that can be approximated to a quadratic or higher-order polynomial. A comparing unit 6 calculates a difference between first relative position information and second relative position information per unit displacement in a position where a first displacement detecting unit 9 is arranged. Then, an absolute position computing unit 7 computes an absolute position in the measurement direction X1 with respect to the scale 2 based on absolute position information and the relative position information of at least one of the first relative position information and the second relative position information, and outputs the absolute position. |
