Dynamic fringe pattern generation using an electrically tunable liquid crystal fabry-perot cell for a miniaturized optical 3-D surface scanning profilometer

We demonstrated a dynamic fringe pattern generation method by using an electrically tunable liquid crystal (LC) Fabry-Perot (FP) cell. In our LC-FP cell, the multiple interferences within the cavity produce concentric ring-type patterns projected on a flat surface because the resonant mode conditions determined by the optical path lengths are circularly symmetric to the slightly diverging single input beam. The projected fringe patterns can be continuously varied with increasing the diameters of the interference rings since the resonant mode conditions can be electrically controlled by changing the effective refractive index of the LC layer. The resonant mode analysis shows that the real surface profiles can be obtained by comparing the amount of distortions of the projected fringe patterns. Our dynamic fringe pattern generation properties, achieved by using single input beam and single LC-FP cell, can be used for miniaturizing optical 3-D surface scanning profilometers.