The van Cittert–Zernike theorem: a fractional order Fourier transform point of view

Abstract The transfer of the coherence by a multielement optical system is studied, within the framework of the fractional Fourier transform. The results show that, the van Cittert–Zernike theorem can be expressed in terms of the fractional order Fourier transforms of the mutual intensities over surfaces M 1 and M 2 ; which allows, among others, to situate this theorem in a quite general context.