Wavefront sensors are devices used to measure the aberrations of an optical wavefront. They are commonly used in adaptive optics systems, lens testing, and ophthalmology. Shack-Hartmann wavefront sensors are specifically used to describe an imaging system, and are widely used in adaptive optics systems.
Shack-Hartmann wavefront sensors (SHWFSs).
Image Credit: Edmund Optics Inc. | Thorlabs