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. 30, 2009
Filed:
Jul. 07, 2005
Hsi-chun Wang, Taipei, TW;
Pei-chi Hsiao, Shangzhu Village, TW;
Chi-ming Lien, Xinzhuang, TW;
National Taipei Normal University, Taipei, TW;
Abstract
A method of watermark with hybrid halftone dots that is suitable for a printed shadow image. The watermark patterns that are composed of amplitude modulation (AM) and frequency modulation (FM) halftone dots (their concentration has been calibrated) cannot be perceived beyond a certain distance by the human eye. This is done through outputting the density calibration chart to choose the proper density parameters, which are applied to the manufacture process of the watermark with hybrid halftone dots. The hidden patterns of a watermark need to be pre-processed first, and thereby making the image blocks of AM and FM halftone dots to be combined smoothly. The copy machine, the lenticular lens and the optical scanner can detect the hidden watermark in the printed shadow image. Each secured document possesses a different serial number to achieve the document-version control.