Retrieval of instantaneous frequency from digital holograms based on adaptive windows

In recent years, time-frequency analysis methods have been significantly developed for the processing of fringe patterns. Among such methods, the short-time Fourier transform (STFT) has been proven a valid method to process noisy fringe patterns. In this paper, the complex phasor and the STFT are used to retrieve instantaneous frequency from a series of holograms based on adaptive windows. Continuous phase maps are calculated by integration of the extracted instantaneous frequency, and phase unwrapping is effectively avoided in both temporal and spatial domains. The validity of this method is verified by an experiment. In addition, a comparison between conventional temporal phase unwrapping and the STFT is presented.