Tuesday, February 12, 2008

US Patent 7328851 - Quantum dot color coding

US Patent 7328851

This patent from Xerox (priority 10/31/2006) includes some broad claims focusing on quantum dots to achieve a multicolor fluorescent glyph for marking items. Claim 1 reads:

1. Machine readable code comprising a set of distinguishable symbols including at least a first symbol for encoding zeroes and a second symbol for encoding ones, wherein the first symbol exhibits a first color during machine reading and the second symbol exhibits a second color during machine reading, wherein the first color and the second color are recognized as different by the machine under machine reading conditions, wherein the first color and the second color are provided by fluorescent marking materials including quantum nanoparticles.

Based on the file history the "novel" feature that the attorney argued was that the marking material was quantum nanoparticles.

Unfortunately there seems to be many pieces of prior art that were overlooked such as:

US Patent 6617583- "A novel encoding system and methods for determining the location and/or identity of a particular item or component of interest is provided. In particular, the present invention utilizes a "barcode" comprising one or more sizes of semiconductor nanocrystals (quantum dots) having characteristic spectral emissions, to either "track" the location of a particular item of interest or to identify a particular item of interest. " (from abstract)

US Patent 6633370-"Quantum dots, semiconductor nanocrystals and semiconductor particles used as fluorescent coding elements" (title)

US Patent 7077329- "Spectral coding by fluorescent semiconductor nanocrystals for document identification and security applications" (title)