Dr. Robert A. Lee Profile

Dr. Robert A. Lee

Principal Research Scientist at CSIRO

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Publications (4)

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Proceedings Article | 9 February 2006 Paper

New applications of modulated digital images in document security

Robert Lee, Patrick Leech, Lawry McCarthy, Gerhard Swiegers

Proceedings Volume 6075, 60750C (2006) https://doi.org/10.1117/12.642440

KEYWORDS: Printing, Modulation, Digital watermarking, Polymers, Photography, Micromirrors, Data hiding, Nickel, Electron beam lithography, Reflectivity

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In previous work we have demonstrated that selective masking, or modulation, of digital images can be used to create documents and transparent media containing covert or optically variable, overt images. In the present work we describe new applications and techniques of such "modulated digital images" (MDI's) in document security. In particular, we demonstrate that multiple hidden images can be imperceptibly concealed within visible, host images by incorporating them as a new, half-tone, printing screen. Half-toned hidden images of this type may contain a variety of novel features that hinder unauthorized copying, including concealed multiple images, and microprinted-, color-, and various fadeeffects. Black-and-white or full color images may be readily used in this respect. We also report a new technique for the embossing of multiple, covert- or optically variable, overt-images into transparent substrates. This method employs an embossing tool that is prepared using a combination of electron beam and greytone lithography. Two approaches may be used: (i) a double-sided "soft" emboss into curable, transparent, lacquer layers, and (ii) a single-sided "hot" emboss in which multiple, dithered images consisting of distinctly-sloped microprisms are impressed into the substrate. Technique (ii) requires a novel, electron-beam-originated master dye.

Proceedings Article | 3 June 2004 Paper

Micromirror array nanostructures for anticounterfeiting applications

Robert Lee

Proceedings Volume 5310, (2004) https://doi.org/10.1117/12.523919

KEYWORDS: Mirrors, Micromirrors, Diffraction gratings, Photomasks, Reflectivity, Printing, Computer programming, Biometrics, Image processing, Diffraction

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The optical characteristics of pixellated passive micro mirror arrays are derived and applied in the context of their use as reflective optically variable device (OVD) nanostructures for the protection of documents from counterfeiting. The traditional design variables of foil based diffractive OVDs are shown to be able to be mapped to a corresponding set of design parameters for reflective optical micro mirror array (OMMA) devices. The greatly increased depth characteristics of micro mirror array OVDs provides an opportunity for directly printing the OVD microstructure onto the security document in-line with the normal printing process. The micro mirror array OVD architecture therefore eliminates the need for hot stamping foil as the carrier of the OVD information, thereby reducing costs. The origination of micro mirror array devices via a palette based data format and a combination electron beam lithography and photolithography techniques is discussed via an artwork example and experimental tests. Finally the application of the technology to the design of a generic class of devices which have the interesting property of allowing for both application and customer specific OVD image encoding and data encoding at the end user stage of production is described. Because of the end user nature of the image and data encoding process these devices are particularly well suited to ID document applications and for this reason we refer this new OVD concept as biometric OVD technology.

Proceedings Article | 3 June 2004 Paper

Modulated digital images for biometric and other security applications

Lawry McCarthy, Robert Lee, Gerhard Swiegers

Proceedings Volume 5310, (2004) https://doi.org/10.1117/12.528099

KEYWORDS: Biometrics, Modulation, Photography, Glasses, Composites, Information security, Computer programming, Image registration, Diffraction gratings, Printing

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There are, in general, two ways for an observer to deal with light that is incorrect in some way (e.g. which is partially out of focus). One approach is to correct the error (e.g. by using a lens to selectively bend the light). Another approach employs selective masking to block those portions of the light which are unwanted (e.g. out of focus). The principle of selective masking is used in a number of important industries. However it has not found widespread application in the field of optical security devices. This work describes the selective masking, or modulation, of digital images as a means of creating documents and transparent media containing overt or covert biometric and other images. In particular, we show how animation effects, flash-illumination features, color-shifting patches, information concealment devices, and biometric portraiture in various settings can be incorporated in transparent media like plastic packaging materials, credit cards, and plastic banknotes. We also demonstrate the application of modulated digital images to the preparation of optically variable diffractive foils which are readily customized to display biometric portraits and information. Selective masking is shown to be an important means of creating a diverse range of effects useful in authentication. Such effects can be readily and inexpensively produced without the need, for example, to fabricate lenses on materials which may not be conducive in this respect.

Proceedings Article | 1 October 1991 Paper

Pixelgram: an application of electron-beam lithography for the security printing industry

Robert Lee

Proceedings Volume 1509, (1991) https://doi.org/10.1117/12.47117

KEYWORDS: Diffraction gratings, Diffraction, Holography, Electron beams, Photography, Optical design, Electron beam lithography, Security printing, Computer security, Security technologies

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Following the development of the Catpix I diffraction gratings structure first used on the 1988 Australian plastic $DLR10 banknote and more recently on the Singapore plastic $DLR50 banknote, the CSIRO Australia, Division of Materials Science & Technology has developed a new optical security and anti-counterfeiting technology known as Pixelgram (or Catpix 2). The Pixelgram, which is subject to patent, is an optically variable device based on a computerized procedure for producing an optically variable version of any given input picture, e.g., a photograph. When a Pixelgram is observed under a given source, such as a fluorescent tube, the image of the original input picture appears at particular angles of view. At other angles, the image varies in both contrast and brightness and can even appear as the photographic negative of the original input picture at some angles of view. As well as its ability to generate optically variable text and graphical images, Pixelgram has the unique capability of being able to display easily recognizable small scale optically variable images of the human face of near photographic clarity. Pixelgram optical security device master plates are produced by a technique borrowed from the microelectronics industry and known as electron beam lithography. In this technique, millions of microscopic grooves are written individually by a finely focused electron beam scanning across a glass plate coated with an electron sensitive material. On a typical Pixelgram there are approximately 2,000 million individual polygons etched into the plate by the electron beam. This corresponds to more than 10,000 megabytes of binary data. The only known electron beam lithography systems that have been able to write such large data files with the required precision are the Cambridge Instruments EBMF 10.5 and EBML 300 electron beam systems.

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