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:
Dec. 09, 2003
Filed:
Apr. 26, 2001
Creo SRL, St. James, BB;
Abstract
A method and apparatus are disclosed for a two-dimensional Moiré type absolute position encoder and an associated control system. A reticle having a pattern variation in two orthogonal directions is illuminated with radiation from a source which is structured so as to create a two dimensional Moiré interference at the reticle. Radiation pulses from the radiation source are multiplexed in time and the resulting interference fringes are converted into electronic signals using a detector. A controller uses the electrical signals to determine the absolute position of the reticle in two dimensions to within the area of a particular cell. After determining the particular cell location, the controller also employs the signals from the groups of radiation stripes to calculate an accurate position of the reticle within the cell.