An Etymological Dictionary of Astronomy and Astrophysics

An optical element consisting of two small angle → prisms,
joined together at their bases, used to produce two
→ coherent sources. The thin double prism refracts the light from a source into two overlapping beams, which produce
→ interference fringes. With this experiment Fresnel was able to produce interference without relying upon → diffraction to bring the interfering beams together.

See also: → Fresnel diffraction; → bi-; → prism.