Babinet's goniometer (1839)



Copyright: Lebée Inventaire Général / École Polytechnique
 

The goniometer designed by physicist and astronomer Jacques Babinet, measures the angular deviation of a light beam passing through an object or substance, and induced by the difference in optical index. This makes it possible—in mineralogy for example—to measure the refractive indices of crystals and the orientation of their crystallographic axes.