This is a phenomenon in which an interference pattern is created by the reflection of light between a spherical and an adjacent flat surface.
When collimated and coherent light is used, such fringes are obtained. Generally, interference of two plane waves results in straight fringes.
A typical Digital Speckle Pattern Interferogram (DSPI), depicting a vibration mode (@ 220 Hz) of a rough aluminum plate.
Depicting wavefront from a deformable mirror. Note, the mirror was made flat at the center and concave at the edges.
"In optics, the Fraunhofer diffraction equation is used to model the diffraction of waves when the diffraction pattern is viewed at a long distance from the diffracting object, and also when it is viewed at the focal plane of an imaging lens."
"In optics, the Fresnel diffraction equation is used to calculate the diffraction pattern created by waves passing through an aperture or around an object, when viewed from relatively close to the object."