Transparent Watermarking for Physical Authentication

Invention Summary:

Physical watermarks such as raised seals and standard watermark labels enable the authentication of important financial and legal documents, identification cards and art work. Many of the known methods like using barcodes, infrared inks and standard watermarks can be easily copied or reverse engineered. Hence, there is a demand for authentication tools that are uncommon, difficult to copy or reverse engineer.

Researchers from Rutgers University have developed a transparent watermark imaging device. The device makes use of multiview imaging for measuring the reflectance over a range of viewing and illumination angles to instantly reveal the unknown Brewster angle of a watermark consisting of a spatially varying deposition of materials with different refractive index.  Multi-angle illumination and observation allows a simple imaging procedure. The device enables reading of transparent watermarks with information coded in a spatial variation of refractive index that are invisible to the human eye.

Market Applications:

Authentication for:

  • Legal documents such as ID cards, passports
  • Bank cards and credit cards
  • Art works
  • Luxury goods


  • Applicable to a wide variety of physical products
  • Invisible - difficult to be duplicated
  • Multiview imaging – no need to position the coding in specific orientation

Intellectual Property & Development Status:

US Patent 7,699,236, available for licensing and/or research collaboration


Dana KJ, Livescu G and Makonahalli R. Transparent watermarking using bidirectional imaging. 2009 IEEE Computer Society Conference on Computer Vision and Pattern Recognition Workshops, Miami, FL, 2009.

Rutgers ID: 2004-128
Physical Sciences
Lisa Lyu
Licensing Manager
Kristin Dana
Yicheng Lu
Gabriela Livescu