Fresneldiffrakció
Fresneldiffrakció, or Fresnel diffraction, is a description of near-field diffraction effects that occur when light passes through an aperture or around an obstacle and is observed at distances where the wavefront remains curved. It is named after Augustin-Jean Fresnel. In contrast to Fraunhofer (far-field) diffraction, the geometry and the curvature of the wavefront play a central role in shaping the interference pattern.
The calculation relies on the Fresnel diffraction integral. The complex amplitude at a point in space is
A key concept is the Fresnel number, F = a^2/(λ z) for a circular aperture of radius a
Typical examples include diffraction by a straight edge, a circular aperture, or small obstructions, where features