inverse Fourier transform

Fourier transform is a method that transforms a function of certain variables into the function of the variables conjugate to the certain variables. On the other hand, "inverse Fourier transform" is a method that transforms the Fourier-transformed function into a function of the original variable. For example, when a crystal potential as a function of position is Fourier-transformed, crystal structure factors are obtained as a function of wavenumber. Next, when the crystal structure factors are inverse-Fourier-transformed, the crystal potential as the function of position is obtained. In TEM imaging, Fourier transform and inverse Fourier transform of the specimen are automatically executed, so that the diffraction pattern and structure image are obtained at the back focal plane and the image plane, respectively.

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