Soleil's compensator (1845)

Copyright: Musées de la Communauté d’Agglomération du Niortais / Renaud Berthrand

The electromagnetic theory of light defines a light beam as an electric field whose components are in a plane perpendicular to the direction in which the beam travels. The Soleil compensator is an optical component, a quartz wedge compensator, that extends the optical path of one component of the electric field to another. This invention considerably simplified the design of instruments.