The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 05, 2002
Filed:
Sep. 14, 1999
Takashi Gemma, Tokyo, JP;
Hiroshi Ichihara, Yokohama, JP;
Hajime Ichikawa, Yokohama, JP;
Shigeru Nakayama, Kawasaki, JP;
Bruce Jacobsen, Tokyo, JP;
Nikon Corporation, Tokyo, JP;
Abstract
Apparatus and methods are disclosed for measuring the surface topography of a test surface, such as a spherical or aspherical surface of a refractive or reflective optical element. The test surface is measured by detecting the state of interference fringes generated by interference of a reference light beam and a measurement light beam that interacts (e.g., reflects from) the test surface. The reference and measurement beams are produced by a point light source having a reflective surface. The point light source is disposed between a source of input light and the test surface. The measurement beam (after interacting with the test surface) and the reference beam are caused to interfere with each other to produce a first interference-fringe state. The distance between the point light source and the test surface can be changed between production of the first interference-fringe state and production of a second interference-fringe state. The profile of the test surface is determined by analyzing the resulting interference fringes. A null element can be used to convert a spherical wavefront of the measurement beam into an aspherical wavefront corresponding to the aspherical test surface, or to convert an aspherical wavefront generated by reflection of a spherical wavefront from an aspherical test surface into a spherical or planar wavefront.