Phase shifting interferometer

US5933236A · kind A · utility

Assignee

• The Regents of the University of California · US

Inventor

• Gary E. Sommargren · Madison, US

Key dates

• Filing date: May 23, 1997
• Grant date: Aug 3, 1999
• Expiry date: May 23, 2017

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. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement 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.