The filtering operation removes scales associated with high frequencies, and the operation can accordingly be interpreted in Fourier space.

The zeroth order (the low frequencies in Fourier space) then passes through the hole and interferes with the rest of beam.

Signal combination in Fourier space is an alternative approach for removal of certain frequencies from the recorded signal.

The notation is used because in Fourier space, these equations indicate that the vector points parallel and perpendicular to the direction of the wavevector, respectively.

Therefore, a single high-fidelity signal can be constructed by combining the low-noise parts of the signals in Fourier space.

Determining the defocus value and compensating for the contrast changes imposed by the objective lens (done in Fourier space)

Indexing and refining the lattice (done in Fourier space)

Extracting amplitudes and phase values at the refined lattice positions (done in Fourier space)

For a more accurate calibration, however, an analysis in Fourier space is necessary.

Using multiple transmitters at different frequencies and locations, a dense data set in Fourier space can be built for a given target.