Dashed lines: PSF expected from applying geometrical optics to a parabolic profile with a sinusoidal profile error with A = 0.1 μm and T = 10 mm (Eq. (14)). The parabolic profile parameters take on reasonable values R₀ = 15 cm, f = 10 m, and L₁ = 300 mm. The detector has a resolution of 20 μm. Solid lines: computed PSF for decreasing λ, using Eq. (9). a) λ = 500 Å, dominated by aperture diffraction. b) λ = 70 Å, first-order scattering dominates and the second-order peaks start to appear. c) λ = 10 Å: multiple orders have become visible. d) λ = 0.5 Å: high-order peaks are almost completely blended, and the PSF now resembles the geometrical optics result.