Patent ID: 8886350

Claim:
A displacement calculation method for calculating a displacement of a target point based on displacements of a plurality of reference points arranged in a grid on a surface of a substrate, along a first coordinate axis direction and a second coordinate axis direction that intersect each other, the method comprising: a step of obtaining position information of a plurality of reference points defined on a substrate surface; a step of detecting, by a computing device, displacements of reference points in the vicinity of a target point in first and second coordinate axis directions based on said position information; a step of performing a computation for a displacement of said target point, wherein said step of performing the computation comprises, for displacements in one coordinate axis direction of said first and second coordinate axis directions, of said reference points in the vicinity of said target point, A: a first spline calculation step of calculating a first spline curve that indicates a relationship between displacement values and first coordinate axis values of reference points included in each group, said reference points included in said each group being aligned in said first coordinate axis direction and having a same second coordinate axis value, B: a first spline-indicated-value calculation step of calculating, as a first spline-indicated value, a value indicated by said first spline curve of said each group at a first coordinate axis value of said target point, C: a first sub-spline calculation step of calculating a first sub-spline curve that indicates a relationship between first spline-indicated values of respective groups and second coordinate axis values of said respective groups, and D: a first sub-spline-indicated-value calculation step of calculating a value indicated by said first sub-spline curve at a second coordinate axis value of said target point; and outputting the displacement of the target point.