A novel pitch evaluation method based on a cross-correlation filter

A cross correlation filter ̶ a half period of sinusoidal waveform sequence (pT period), is applied to filter the topographical signal (p period )of 1D arbitrary-form grating against positions. It, as a template, cross-correlate with the signal and the noise that coexists with signal is eliminated if pT  p. After filtering, the distance between any two adjacent waveform peaks along the direction perpendicular to 1D grating lines is one pitch value, the peak-detection (PD) method. In this method, the pitch average and uniformity can be calculated