Wavelength scanning distance interferometry using inflection point retrieval for phase unwrapping

A real-time wavelength scanning distance interferometry is proposed. The interference signal generated by the light wavelength modulation is transformed into preliminary conversion signal with the two summarized waveform transformation laws. Inflection points of the interference signal are retrieved with two complementary methods which are discontinuity point judgment (DPJ) and the adjacent null points distance judgment (ANPDJ). Based on the preliminary conversion signal and the retrieved inflection points, the orthogonal signal is constructed. Displacement is calculated after demodulating the phase shift with the orthogonal demodulation algorithm. When millimeters distance is measured, the fluctuation of the measured result is around micrometers in about one hour. The measurement complexity and cost are all decreased, while, ideal measurement results can still be obtained. The approach can be used in a multitude of applications.