The present invention provides a band-pass filter, being capable of fitting a frequency spectrum area having phase information in a frequency spectrum image, to obtain a spectrum information corresponding to the phase information during the process of obtaining the phase information from the frequency spectrum image with respect to an object's surface profile. In another embodiment, the present invention further provides a method to optimize the spectrum range of the band-pass filter so as to enhance measuring accuracy and efficiency while restoring the surface of the object. In addition, by employing the foregoing method, the present invention further provides a measurement system for measuring three-dimensional surface shapes in which a deformed fringe pattern with respect to the measured object's surface is acquired and the phase information is obtained from the fringe pattern according to the foregoing method so as to restore the surface profile of the measured object.