Editing Catadioptric system (section)

== Early catadioptric systems ==
Catadioptric combinations have been used for many early optical systems. In the 1820s, [[Augustin-Jean Fresnel]] developed several catadioptric lighthouse reflector versions of his [[Fresnel lens]].<ref>[https://books.google.com/books?id=-LkUAAAAYAAJ&dq=earliest+catadioptric&pg=PA634 The Encyclopædia Britannica, 1911]</ref> [[Léon Foucault]] developed a catadioptric microscope in 1859 to counteract aberrations of using a lens to image objects at high power.<ref>[https://books.google.com/books?id=UbMRmyxCZmYC&dq=earliest+catadioptric&pg=PA214 William Tobin, The life and science of Léon Foucault: the man who proved the earth rotates William Tobin,  page 214]</ref> In 1876 a French engineer, A. Mangin, invented what has come to be called the [[Mangin mirror]], a concave glass reflector with the silver surface on the rear side of the glass. The two surfaces of the reflector have different radii to correct the aberration of the spherical mirror. Light passes through the glass twice, making the overall system act like a [[triplet lens]].<ref>[https://books.google.com/books?id=i35NCLLiglIC&dq=mangin+mirror+was+invented+by&pg=PA65 Optical design fundamentals for infrared systems By Max J. Riedl]</ref> Mangin mirrors were used in searchlights, where they produced a nearly true parallel beam. Many [[Catadioptric system#Catadioptric telescopes|Catadioptric telescopes]] use negative lenses with a reflective coating on the backside that are referred to as “Mangin mirrors”, although they are not single-element objectives like the original Mangin, and some even predate Mangin's invention.<ref name="telescope-optics.net">[http://www.telescope-optics.net/catadioptric_telescopes.htm - Vladimir Sacek, telescope-optics.net, Notes on AMATEUR TELESCOPE OPTICS, CATADIOPTRIC TELESCOPES, 10.2.1]</ref>