abstract:A Schmidt corrector plate is an aspheric lens which is designed to correct the spherical aberration in the spherical primary mirror it is combined with. It was invented by Bernhard Schmidt in 1931, although it may have been independently invented by Finnish astronomer Yrjö Väisälä in 1924 (sometimes called the Schmidt-Väisälä camera).
Opticssystemconsistsof asphericalprimarymirrorMBat the southern end, a reflectingSchmidt corrector ma at the northern end, with the focal platein between.