Absolute fringe order calculation using optimised multi-frequency selection in full-field profilometry

We present novel algorithms using multi-frequency analysis for full-field profilometry. The technique provides absolute order of interference in an interferogram. The process is based on an optimisation criterion to utilise the minimum number of projected fringe frequencies to give the largest possible measurement dynamic range. The algorithms presented have been generalised for n frequencies. A set of solutions for three-frequency interferometry is presented that satisfies the optimisation criterion. Results are presented for 3 projected fringe frequencies and we demonstrate by simulation that the approach is indeed optimal. The algorithms given are generic and are equally applicable to any metrological measurement using interferometry.