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. 19, 2013
Filed:
Jun. 15, 2006
Holger Hofmann, Thousand Oaks, CA (US);
Alan Bruce Hamersley, Newbury Park, CA (US);
John Matthew Town, Ojai, CA (US);
Holger Hofmann, Thousand Oaks, CA (US);
Alan Bruce Hamersley, Newbury Park, CA (US);
John Matthew Town, Ojai, CA (US);
Thomson Licensing, Boulogne-Billcourt, FR;
Abstract
The present principles provide a way to place a multilevel grayscale image, visible with the bare eye in the data area of an optical disc. This feature can be used to authenticate a legitimate disc, since the image features are lost when copying a disc either with a PC recording drive or by a pirate creating a data set to be used on a laser beam recorder to produce forged ROM discs. The modulation rules are selectively varied during disc writing in a way to change the distribution of pit/land lengths, so that the at least three (3) different diffraction properties are generated, and therefore produce at least three (3) distinct looks to the bare eye.