Fig. 2
From: Pushing the resolution limit of coherent diffractive imaging
Free-space optical field propagation. a the Ewald sphere effect. b the propagation geometry of the Rayleigh-Sommerfeld diffraction. Here, U(ξ, η, 0) and U(x, y, z) represent the optical fields of source plane and observation plane, respectively; ξ and η are coordinate variables in the source plane; x, y, z are coordinate variables in the observation plane of the Cartesian space and xc, yc, and z are coordinate variables in the real ES space; dx and dy are pixel size in the Cartesian space. ∑ is the optical field region of the source plane. z and r represent the optical field propagation distance between the source plane and the observation plane and the relative distance of the coordinate positions in the source plane and the observation plane, respectively. θ represents the diffraction angle. dΩ is the pixel solid angle
