This invention relates generally to systems for authenticating articles, methods for authenticating articles, and processes for marking articles for later authentication. This invention relates particularly to mechanisms and methods for detecting indicia which may include graphic images and/or characters and for comparing the detected indicia with predetermined indicia to verify the articles"" authenticity if the detected indicia are recognized. This invention relates more particularly to detection, discrimination, and recognition of fluorescent indicia rendered detectable by illumination of articles with ultraviolet light.
The counterfeiting of articles of many kinds has become a serious problem worldwide, causing great loss of revenues to legitimate businesses and to individuals. Counterfeiting has produced articles that are very difficult to distinguish from the genuine articles, taking sales revenues from the producers of genuine articles and impacting legitimate business"" reputations when the counterfeit articles have inferior quality and/or non-existent manufacturers"" support. Similarly, problems and losses occur due to counterfeiting of articles used for financial transactions or identification, such as credit cards, drivers"" licenses, passports, and immigration documents. Even when genuine articles have been marked with authentication markings such as watermarks, special papers, and holograms which are difficult to replicate, counterfeiters have managed to produce articles that appear genuine. The general availability of newer replication technology such as high-resolution image scanners, laser copiers and printers, and color-accurate color copiers and printers has enabled counterfeiters to produce more credible counterfeit articles. These technological developments of replication hardware continue to make rapid progress, as do the computer hardware and software that support them. Thus it is useful to have additional ways to mark articles for authentication with greater security. Greater security may be achieved by making authentication markings more difficult for counterfeiters to detect and interpret, by incorporating greater complexity into the markings, and by making replication by counterfeiters more difficult. Combining multiple kinds of marking indicia can further increase the complexity of detection, interpretation, and replication, thus providing even better security. Considering the security issue from another point of view, it is not desirable to use the same means that generated the visible appearance of an article to authenticate it, as the visible appearance is becoming easier to replicate. Invisible indicia that cannot be reproduced by common visible graphic copying and printing means can provide improved security, especially when combined with complex images, patterns, and/or characters.
In this specification, the following terms or abbreviations are used with the meanings listed here:
CCDxe2x80x94charge coupled device
DSPxe2x80x94digital signal processor
excitation timexe2x80x94a characteristic time for a fluorescent emission to be excited after ultraviolet illumination of a fluorescent substance begins
extinction timexe2x80x94a characteristic time for a fluorescent emission to decay exponentially from its initial emission intensity IO to intensity IO/e
IRxe2x80x94light in the infrared portion of the spectrum
OCRxe2x80x94optical character recognition
registrationxe2x80x94the conventional definition of this term in the fields of graphic communication and printing, as defined, for example, in xe2x80x9cGlossary of Graphic Communicationsxe2x80x9d compiled by Pamela Groff and published by Graphic Arts Technical Foundation (Prentice-Hall, Inc., Upper Saddle River, N.J., 1998) at pages 245-246.
UVxe2x80x94light in the ultraviolet portion of the spectrum
visible/IRxe2x80x94light either entirely in the visible portion or entirely in the infrared portion, or partly in both visible and infrared portions of the spectrum
visible/UVxe2x80x94light either entirely in the visible portion or entirely in the ultraviolet portion, or partly in both visible and ultraviolet portions of the spectrum
Many methods have been known to authenticate valuable articles. Some known methods include imprinting a white-light hologram or imprinting reflective and diffractive indicia which display distinctive images that are difficult to counterfeit. Other known methods include incorporation of distinctive fibers into the articles, such fibers being detectable by visual observation, microwave irradiation, or other means. U.S. Pat. No. 4,921,280 describes fibers made luminescent by a dyeing process employing rare-earth compounds, which fibers may be incorporated into articles requiring authentication.
It is known that documents may be authenticated by marking the documents with substances such as inks or dyes that appear invisible or relatively unnoticeable to the naked eye in ordinary visible illumination, but that fluoresce when illuminated with ultraviolet light, revealing marks that serve to identify the legitimate document. These methods depend on substances that are not easily or inexpensively identified by a counterfeiter, and not easily or inexpensively duplicated or mimicked by a counterfeiter. When using these methods, it is desirable to use substances such as dyes or inks that fluoresce in narrow spectral bands which are distinguishable by sufficiently narrow-band detectors, but not readily distinguishable by eye. In U.S. Pat. No. 4,146,792 by Stenzel et al., these methods are extended to include dyes containing rare-earth elements whose fluorescence is influenced by the chemical environment of the fluorescing atoms in a non-fluorescing matrix, and the detection is refined to include detection of predetermined fine structure in the line spectrum of emitted light. Yet another class of authentication methods uses substances which fluoresce in the infrared portion of the electromagnetic spectrum when illuminated by light in the visible portion of the spectrum.
In U.S. Pat. No. 4,642,526 by Hopkins and assigned to the assignee of the present invention, a source of ultraviolet light is made self-modulating at a predetermined frequency. Detection of the secondary radiation, filtering of the detected signal, and demodulation of the filtered signal at the predetermined frequency allow the system of Hopkins"" invention to detect the fluorescent marks despite interference from ambient light sources.
Marking products with indicia such as bar codes using fluorescent substances such as inks or dyes is also known in the prior art, both for the purposes described above and for providing identification on the products without detracting from the products"" appearance as normally viewed in visible light. U.S. Pat. No. 4,983,817 by Dolash et al. describes methods and apparatus for reading bar codes printed with fluorescent substances, while compensating for variations in background reflectance over the area printed with the bar code. U.S. Pat. No. 5,064,221 by Miehe et al. shows the use of fluorescent substances added to ink ribbon used for printing original documents, in order to distinguish the originals from copies. In many of the known authentication methods using fluorescence, the fluorescent identifying substance may be incorporated into the article during the article""s manufacture. In U.S. Pat. No. 4,451,521 by Kaule et al., for example, luminophores are incorporated into paper during its manufacture. Some of the fluorescent substances used in the prior art for authentication purposes contain heavy metals, which are not as safe or environmentally benign as substances not containing such heavy metals. While fluorescent substances have been used in many ways in the prior art to mark articles with indicia for interpretation by human observers, to our knowledge neither optical character recognition (OCR) systems nor image verification systems have been combined with fluorescent markings and UV light illumination to provide improved authentication methods.
The technology of automatic pattern recognition is described in a large body of literature including numerous patents, especially in the application area of optical character recognition (OCR). Many of the recent developments in OCR technology (especially in recognition logic software) are usable with the present invention albeit with some adaptation to the type of light source and to such contrast conditions as may differ from those encountered with conventional OCR scanners having conventional visible/IR light sources.
It is an object of this invention to provide an improved authentication system which can detect and recognize complex authenticating indicia such as graphic images and alphanumeric characters. It is another object of the invention to provide an authentication system which can be readily automated to provide authentication that does not depend on human subjective judgment. It is another object of the invention to combine the use of substances which fluoresce under UV illumination, detectors capable of detecting fluorescent radiation, and image or character recognition techniques to enable the creation and authentication of articles with improved security. Another object of the invention is to enable the use of character or image indicia for authentication printed with substances that are safer and less likely to harm the environment than substances containing heavy metals. Another object of the invention is to enable the use of character or image indicia for authentication printed with substances that have sufficiently short extinction times to enable fast scanning. Another object is to enable capture of complex indicia without undue loss of resolution or smearing of details. Another object is to enable robust identification of articles of mail using mail bar codes such as xe2x80x9cPostNETxe2x80x9d codes printed with fluorescent substances. Another object of the invention is to enable the use of fluorescent indicia for authentication that are more complex than bar codes or simple arrays of dots and/or lines, and that allow a higher density of information per unit area than conventional bar codes. Another object is to provide an authentication system that makes counterfeiting and fraudulent labeling of articles including documents more difficult and expensive to accomplish. Another object is to provide a system that can mark articles for authentication without unduly compromising their aesthetic appearance. Another object is to provide authentication marks that are not easily removed. Another object is to provide flexible methods of authenticating articles that can be practiced in the field of use without requiring special printing press equipment. Another object is to provide an authentication system that can be re-programmed by a user to use various authentication criteria within its range of graphic image and character recognition capabilities.
An authentication system in accordance with this invention combines a source of ultraviolet light (and optionally a scanning mechanism) with apparatus for capturing and recognizing either graphic images or characters or both, where the graphic images and/or characters have been previously made with fluorescent substances that may be invisible under ordinary visible light, but are rendered detectable by the ultraviolet light. As in conventional optical character recognition (OCR), the characters may be conventional alphanumeric or other natural-language characters readable by human readers once they are made visible.
The authentication system has a housing enclosing its optical paths, a source of at least UV light, a detector for detecting graphic images or characters, conversion of the detector signal to digital form, a memory storing predetermined indicia, recognition logic, and indicators. The system may also include a scanning mechanism and optical filters to select predetermined wavelengths of fluorescent light. The detector may be capable of detecting both fluorescent images and normal visible images, and the authentication system may incorporate switching mechanisms to allow multiplexed acquisition of fluorescent and normally visible images produced by visible/IR or visible/UV illumination.
The authentication system can work in conjunction with processes performed in accordance with this invention, for marking articles with indicia selected from a predetermined set of graphic images and characters readable by optical character recognition and/or by image comparison. That process can include printing fluorescent graphic images or characters in registration (or in predetermined mis-registration) with substantially identically-formed images or characters previously printed with visible substances and/or with fluorescent substances of different characteristic fluorescent wavelength. The recognition logic of the authentication system can include comparison of these two (fluorescent and visible/IR, fluorescent and visible/UV, or two different fluorescent) images with each other. The process can also include printing fluorescent graphic images or characters with a multiplicity of fluorescent substances having distinct fluorescent wavelengths and excitation or extinction times, and printing those in overlay with registration or with predetermined registration offset. The registration offset may be selected to produce a predetermined stereo image when properly viewed by a human observer, thus allowing xe2x80x9cfirst orderxe2x80x9d authentication by visual inspection using suitable filters. Similar first order authentication may be provided by printing graphic image or character indicia which are both fluorescent and partially visible without UV illumination. Another overlay method uses two graphic images or character indicia, each incomplete in itself, with unconnected but complementary segments. When the two complementary segments are combined with appropriate registration, a complete recognizable graphic image, word, or natural language phrase is formed.
Other objects, uses, advantages and features of the invention will become apparent to those skilled in the art from the following descriptions of preferred embodiments.