2D representation of the occulter, the modulus , and the phase ∠Ψz(x, y) of the diffraction. The transition region between light and shadow is a rectangular zone of 80 mm × 60 mm with a central position at 720 mm. From top to bottom: Panel a: circular sharp-edged occulter. Panel b: serrated occulter Nt = 512 and Δ = 10 mm. Panel c: serrated occulter Nt = 1024 and Δ = 20 mm.