Scanning interferometer for aspheric surfaces and wavefronts

US6879402B2 · kind B2 · utility

Assignee

• Zygo Corporation · US

Inventor

• Michael Kuchel · Oberkochen, DE

Key dates

• Filing date: Nov 15, 2002
• Grant date: Apr 12, 2005
• Expiry date: Mar 18, 2023

Classification

• Technology area (CPC G): Physics
• CPC primary: G01J9/02
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Interferometric scanning method(s) and apparatus for measuring rotationally and non-rotationally symmetric test optics either having aspherical surfaces or that produce aspherical wavefronts. A spherical or partial spherical wavefront is generated from a known origin along an optical axis. The test optic is aligned with respect the optical axis and selectively moved along it relative to the known origin so that the spherical wavefront intersects the test optic at the apex of the aspherical surface and at radial positions where the spherical wavefront and the aspheric surface intersect at points of common tangency. An axial distance, ν, and optical path length, p, are interferometrically measured as the test optic is axially scanned by the spherical wavefront where ν is the distance by which the test optic is moved with respect to the origin and p is the optical path length difference between the apex of an aspherical surface associated with the test optic and the apex of the circles of curvature that intersect the aspherical surface at the common points of tangency. Coordinates of the aspherical surface are calculated wherever the circles of curvature have intersected the aspherica…