What is a “null”?

A “null corrector” is the historical name to describe an optical assembly used with an interferometer to test non-spherical optics, usually large aspheric mirrors.

The word “null” was adapted for CGH patterns that achieve this same goal.

The region of a CGH that sends light to your test optic for direct measurement of its transmitted or reflected wavefront is called the “null pattern”.

Learn more about the history of CGHs as Null Correctors.