ess.imaging.tools.resolution.normalized_radial_spectrum

ess.imaging.tools.resolution.normalized_radial_spectrum(image)

Return the normalized, radially averaged Fourier-amplitude spectrum.

Parameters:

image (DataArray) – A two-dimensional image sampled on equally spaced square pixels. Pixel coordinates are not used; the frequency is expressed per image pixel.

Returns:

DataArray – Fourier-amplitude spectrum with a dimensionless frequency coordinate in cycles (line pairs) per pixel. Each coordinate is the mean frequency magnitude in its radial bin. Only bins up to 0.5 cycles per pixel are included, inside the circle bounded by the axial Nyquist frequencies. The zero-frequency amplitude is normalized to one.

Notes

This is an amplitude spectrum, not a power spectrum. It can be used to inspect the measured and reference spectra underlying modulation_transfer_function().