The fast (optics) and the furious (design): challenging optical design for multiple reference wavefront sensors on 8- to 100-m telescopes

We present the optical design of the layer-oriented wavefront sensors for two 8m class telescopes. By a combination of fast optics and "stars enlargers" it is possible to shrink the pupil image in a way to fit the available detectors. These concepts are then extended to the design of a wavefront sensor for a 100 m class telescope.