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:
May. 25, 1999
Filed:
Sep. 08, 1997
Joseph C Marron, Ann Arbor, MI (US);
Kurt W Gleichman, Saline, MI (US);
ERIM International, Inc., Ann Arbor, MI (US);
Abstract
A system for interferometric inspection of an object includes a number of improvements to reduce spurious reflections and provide precision measurement of large objects. A neutral density filter of absorptive glass is used as an attenuator to reduce undesirable reflections which may otherwise result in detector saturation. A wedge-shaped beam splitter having at least one anti-reflective surface is also utilized to reduce unwanted reflections. The system uses multiple wavelength interferometry to provide range information for an object. Additional improvements in precision may be provided by using a wavelength calibration device such as an etalon, a wavemeter, or a reference cell having relatively narrow transmission peaks, to improve the accuracy in determining the laser wavelengths. The wavelength information may be used to more precisely determine range values for the object. The various improvements in precision and accuracy facilitate use of differing optical path lengths for the reference beam and object beam so that overall system size and complexity is reduced.