Application of correlation curve fitting to improve the absolute displacement measurement using speckle correlation

Displacement measurement using a database of speckle patterns is one method for producing a low cost, non-contact, high resolution displacement measurement. However, this method requires a large number of database patterns that limits the measurement range and speed, especially in two dimensions. Appropriate curve fitting helps reduce the number of required database patterns, making it feasible to develop an absolute scale for machine tools based on speckle correlation. The curve used for fitting is the autocorrelation function of the speckle pattern, referred to here as the correlation curve.