A measurement system based on M-Z interferometer is set up to obtain the phase information and characterize the surface topography of the grating.By using Fourier transform method and phase unwrapping technique,the interferogram obtained by the measurement system is processed and then the structure parameters of the grating such as height,period and angle are calculated.The result shows that this measurement method and system can measure the surface topography of optical phase element accurately,and has pra...