An algorithm is proposed to process the interference signals of white-light interferometer in order to obtain the surface
height/depth profile of a sample by using the maximum envelope method. Via a low-pass filter, the DC signal of the
interference signal is obtained, and then a preprocessed signal which is the difference of the interference signal and its
DC one is calculated. After that, the envelope of the preprocessed signal is obtained by using Hilbert transform, and then
the height is estimated by the following peak detector. Based on this algorithm, the surface morphology of the sample is
reconstructed. In our experiment, a step of 75 nm was set for a PZT motor, the scanning span in z-axis was 10.5 μm, and
a 50-fold Mirau interferometer was used. In addition, a polynomial fitting can be used further for the peak detection of
this envelope to improve the accuracy. Moreover, a spatial low-pass filter can be utilized to smooth the height profile.