Shack–Hartmann wavefront sensor

The design of this sensor improves upon an array of holes in a mask that had been developed in 1904 by Johannes Franz Hartmann as a means of tracing individual rays of light through the optical system of a large telescope, thereby testing the quality of the image.

The fundamental principle seems to be documented even before Huygens by the Jesuit philosopher, Christopher Scheiner, in Austria.

[8] Shack–Hartmann sensors are used in astronomy to measure telescopes and in medicine to characterize eyes for corneal treatment of complex refractive errors.

[9][10] Recently, Pamplona et al.[11] developed and patented[12] an inverse of the Shack–Hartmann system to measure one's eye lens aberrations.

The magnitude of this shift provides data to estimate the first-order parameters such as radius of curvature and hence error due to defocus and spherical aberration.

Shack–Hartmann system in clinical optics: Laser creates a virtual light source in the retina. The lenslet array creates spots in the sensor according to the wavefront coming out of the eye.
Inverse of the Shack–Hartmann system in clinical optics: A set of patterns is displayed on the screen, the user aligns/overlaps them in a single image pressing buttons.
A schematic illustration of a SHWFS.
Operations of a single lenslet in a SHWFS.