Diffraction which occurs for (near the aperture), where F is the Fresnel number. The wavefunction of the diffracted wave is given by
where k is the wavenumber, is the wavelength, R is the distance from the aperture, is the aperture factor, and the integral is taken over the aperture.
Diffraction, Fraunhofer Diffraction, Fresnel Diffraction--Circular Aperture
