Fig. 1

a An aperture composed of four squares arranged symmetrically along the cartesian coordinates and obstructed by a circular annulus placed in the center of diameter 128 pixels and annular width 16 pixels. Each square has dimensions 128 × 128 pixels compared with the whole matrix of dimensions 1024 × 1024 pixels. b An aperture composed of four squares arranged symmetrically along the cartesian coordinates and obstructed by a square annulus placed in the center of width 16 pixels. Each square has dimensions 128 × 128 pixels and shifted by 256 pixels along the coordinates. c An aperture composed of two squares arranged symmetrically along the y-axis, and two rectangles arranged along x-axis and obstructed by an annular rectangle placed in the center. Each square has dimensions 128 × 128 pixels and shifted by 256 pixels along the coordinates, and each rectangle has dimensions 128 × 512 pixels and shifted by ± 256 pixels from the x-axis. d An aperture composed of a square of dimensions 640 × 640 pixels