Phase shifting diffraction interferometer

US5548403A · kind A · utility

Assignee

• The Regents of the University of California · US

Inventor

• Gary E. Sommargren · Madison, US

Key dates

• Filing date: Nov 28, 1994
• Grant date: Aug 20, 1996
• Expiry date: Nov 28, 2014

Classification

• Technology area (CPC G): Physics
• CPC primary: G01B2290/70
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.