Phase-shifting AFM moire method

In this paper, a phase shifting technique for atomic force microscope (AFM) scanning moire method is proposed. The phase shifting is realized in four steps from 0 to 2π by a piezo-scanner in AFM. The measurement method and experimental techniques are described in detail. For demonstration, this method is applied to determine the phase distribution in AFM moire of a 1200 lines/mm holographic grating used to measure thermal deformation in a QFP electronic package.