Shack-Hartmann
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A Hartmann-Shack or Shack-Hartmann is a type of wavefront sensor. It is commonly used in adaptive optics systems. It consists of an array of lenses (called lenslets) of the same focal length. Each is focused onto a photon sensor (typically a CCD array or quad-cell). The local tilt of the wavefront across each lens can then be calculated from the position of the focal spot on the sensor. Any phase aberration can be approximated to a set of discrete tilts. By sampling an array of lenslets all of these tilts can be measured and the whole wavefront approximated.
Since only tilts are measured the Shack-Hartmann can not detect discontinuous steps in the wavefront.
The design of this sensor was proposed by the German Hartmann in 1900 [1] and built by Shack and Platt in 1971 [2]. Therefore the common terminology is Hartmann-Shack (or as proposed by Shack and Platt 'Hartmann-screen'), while in the US there is prevalence to place the US-American Shack at the front in other countries the historical sequence is used. The fundamental principle seems to be documented even before Huygens by a Jesuit philosopher named Scheiner [3] in Austria.
