18.11.2 Inverse 2D FFT

2D IFFT is a fast algorithm for two-dimensional discrete Fourier transform (2D IDFT), which can be defined as follows:

f(x,y)=\sum_{u=0}^{M-1}\sum_{v=0}^{N-1} F(u,v)e^{j2\pi(ux/M+vy/N)}

It works on a two dimensional array of data, and is capable of reconstructing a 2D signal from its spectrum. However, the reconstruction is correct only when certain controls in both the 2D FFT and 2D IFFT dialog boxes are properly set: if DC Shift Center is checked in the fft2 dialog, Undo Shift should be checked in the ifft2 dialog. Conversely, if DC Shift Center is not checked, Undo Shift should be cleared.

Inverse 2D FFT IFFT2.png

To use 2D IFFT:

  1. Make a matrix book active.
  2. Select Analysis: Signal Processing: FFT: 2D IFFT from the Origin menu.

Topics covered in this section: