Optical Metrology by Fringe Processing on Independent Windows Using a Genetic Algorithm

We present a method to retrieve the phase of a fringe pattern based on the window fringe pattern demodulation technique (WFPD). The overlapped phase similarity criterion is avoided in the proposed method, and it is substituted by a second order smoothness criterion. The fringe processing on independent windows (FPIW) method can measure physical quantities from closed and near sub-sampled fringe patterns by a simplified cost or fitness function. The fringe image is divided into a set of partially overlapping windows. In these sub-images the estimated phase is modelled as a parametric analytic-function, and its parameters are optimized using a genetic algorithm (GA). This analytic-function is used to estimate the phase in the area framed by the window. Phases from all windows are sequentially spliced to retrieve the whole phase field. A media filter is applied over the entire phase field to smooth the irregularities that appear in the junctures between windows.