The
Fourier transform (detailed
mathematics) of a function ƒ(x) is defined as:
Image
processing in Fourier space is performed in a similar way as
image formation in the TEM:
1.
the Fourier transform of an image, e.g. a HRTEM image, is calculated.
Periodic structures in the image give rise to sharp spots in the
resulting diffraction pattern.
2 Masks
could be selected that allow only some spots or other parts of the
information present in reciprocal space to contribute to the image
formed by inverse FT. In TEM, similar effects are achieved by the
use of aperatures.
3.
A filtered image is calculated by inverse FT.
