Method to overlay an interference field over a grating using only the grating's profile symmetry.

We theoretically present and experimentally validate a method to overlay the interference field (for making straight-line holographic gratings) with a real grating and a derived method to measure the lateral shift between two real gratings. The methods rely only on the real gratings' profile symmetry, and they are robust against variations of the real gratings' profile parameters and functional form.