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. 13, 1994
Filed:
Jan. 03, 1994
Claude Tinet, Paris, FR;
Thomson-CSF, Paris, FR;
Abstract
The present invention concerns an arrangement for reading an optically readable carrier having a substrate with diffractive tracks with respective longitudinal axes and formed of a succession of irregularities with respect to a smooth reference surface. The irregularities have a width of at most two microns and a variable length equal to or greater than their width and these irregularities have closed contours in the reference surface. The closed contours are diffractive along the entire extent in order to provide for a diffraction of light of a particular light spot focused and centered on a single one of the tracks and substantially occupying the width of the single track. Each of the irregularities has a data element stored along the entire length of the contour and successive irregularities along a track are separated by clearance spaces at least as long as the width of the irregularities in the reference surface. Information is contained in the data elements and is indicated by the continuous extent of the closed contours and by the extent of each of the clearance basis. The irregularities with the contours are such that light emerging from the track has a spatial distribution representing an amount of track misregistration between the spot and the axis of the track. The tracks have a pitch from one track to the next of at least two times the width of an irregularity and a reflective coding is providing on the reference surface and on the irregularities.