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:
Jun. 06, 2000
Filed:
Oct. 30, 1998
David Stephenson, Madison, CT (US);
Xavier Colonna de Lega, Middletown, CT (US);
Zygo Corporation, Middlefield, CT (US);
Abstract
The optical assembly of a GDI instrument is configured to deviate or steer stray beams away from the pupil of the instrument's imaging device and/or to suppress stray beams. Stray beam deviation is optimized by selecting particular wedge and/or tilt configurations that achieve the desired stray beam deviation while avoiding or at least minimizing phase offset at the optimum metrology plane. Stray beam suppression can be achieved by providing the diffractive groove profile of the instrument's optical assembly with smooth edges. The resultant profile facilitates effective diffraction order management as well as a reduction in back reflection. The invention is particularly well-suited for use with a GDI instrument in which the optical assembly comprises first and second diffraction gratings. In this case, any average phase offset that remains after setting wedge and/or tilt can be eliminated by inserting a suitable compensating plate between the first and second diffraction gratings or between the second diffraction grating and the object.