Pitch evaluation of gratings based on a digital image correlation technique

The digital image correlation (DIC) technique used for metrological grating evaluation is presented in this paper. A CCD camera is used to acquire the grating image, and the DIC technique together with the peak-position detection method is used to evaluate the grating pitches. The theoretical analysis and simulations are performed to confirm that the performance of our technique is as accurate as the Fourier transform (FT) technique, and is capable of noise resistance. As an example, the uniformity of the grating fabricated in our laboratory is measured using this method. The experimental results show that this grating has a peak-to-valley uniformity of 48nm during a long range of 35mm, and our technique has a higher repeatability than the FT technique in our measurement strategy. This work should be of great significance for the evaluation of metrological grating for optical encoders. •Digital image correlation technique presented here has a high accuracy, and it is more stable than FFT technique.•Only a CCD camera is employed in our measurement, which is time-saving and low-cost.•The measurement results of a home-made grating show that the grating has a peak-to-valley uniformity of 48 nm with a standard deviation of 12 nm.