WO1995004665A1 - Donnees imprimees incrustees, procede et appareil afferents - Google Patents

Donnees imprimees incrustees, procede et appareil afferents Download PDF

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Publication number
WO1995004665A1
WO1995004665A1 PCT/GB1994/001710 GB9401710W WO9504665A1 WO 1995004665 A1 WO1995004665 A1 WO 1995004665A1 GB 9401710 W GB9401710 W GB 9401710W WO 9504665 A1 WO9504665 A1 WO 9504665A1
Authority
WO
WIPO (PCT)
Prior art keywords
data
screen
carrier
pattern
embedded data
Prior art date
Application number
PCT/GB1994/001710
Other languages
English (en)
Inventor
Graham Stewart Brandon Street
Original Assignee
Hardy Business Forms Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB939316581A external-priority patent/GB9316581D0/en
Priority claimed from GB939322575A external-priority patent/GB9322575D0/en
Application filed by Hardy Business Forms Limited filed Critical Hardy Business Forms Limited
Publication of WO1995004665A1 publication Critical patent/WO1995004665A1/fr

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M3/00—Printing processes to produce particular kinds of printed work, e.g. patterns
    • B41M3/14—Security printing
    • B41M3/146—Security printing using a non human-readable pattern which becomes visible on reproduction, e.g. a void mark

Definitions

  • This invention is concerned with the field of halftone printing, in which the weight of ink per unit area is controlled by varying, within an array of printed dots, the size of each dot relative to the spaces between neighbouring dots.
  • the dots are typically very small and are not noticed individually.
  • the invention is concerned with the embedding of information by the relative positioning of the printed dots.
  • the regular array used in halftone printing known as a screen, has a pitch of typically 0.02" to 0.002", corresponding to a spatial frequency of 50 to 500 dots per inch. It is normal to vary the size and shape of these dots, but not the phase of one part of the array with respect to another.
  • This invention seeks to exploit the characteristics of Moire patterns by using these to embed, in a printed document, information in the form of a shift of phase and/or rotation of the dot pattern relative to a decoding screen, at a plurality of locations.
  • a carrier of embedded data comprises at least two screens, a first of said screens comprising a first plurality of substantially similar first elements, the centre of gravity of each element of said first plurality being located at a corresponding point within a first extending regular array of points, and a second of said screens comprising a second plurality of substantially similar second elements, the centre of gravity of each element of said second plurality being located at a corresponding point within a second extending regular array of points, wherein there is a difference between said first array and said second array, said difference comprising a relative phase shift between said arrays and/or a difference between the spacing between adjacent points within said first array and the spacing between adjacent points within said second array and/or the relative orientation of the axes of the first array with respect to the axes of the second array.
  • the screens are printed on the same substrate and the embedded data at a location on the substrate comprises elements of the first screen and is substantially void of elements of the second screen.
  • the difference between the first array and the second array is substantial so that, in use, a matching reference pattern, combined and substantially aligned with the first screen provides a pattern of interference comprising regions of constructive and/or destructive interference at locations where the first screen is present, said regions having dimensions substantially greater than the spacing between adjacent elements of the first screen, and there is no substantial simultaneous interference with the second screen, whereby embedded data is observed where the first screen is present.
  • a plurality of screens may each comprise embedded data at respectively different locations and/or for respectively different spectral components of an illummant so that, in use, a reference pattern comprising a respective plurality of matching sub-patterns provides interference at each respective location and/or for each respective spectral component.
  • the screen with embedded data may be printed with ink containing a UV fluorescent dye so that, in use, it is only observed when illuminated with UV light.
  • the embedded data may take the form of a bar code or its two- dimensional equivalent.
  • a reader of embedded data comprises means for locating an embedded data carrier; reference means comprising a reference pattern located in close proximity to said carrier or an image thereof; and means for viewing and/or detecting, in use, the interference pattern formed by the superposition of a screen of said carrier or an image thereof and said reference pattern, whereby said data is read.
  • Means may be provided for moving the data carrier and/or the reference means relative to each other so that, in use, the interference pattern is changed.
  • One such means is a piezo ⁇ electric transducer.
  • the reference pattern is partially transparent. Typically, it comprises a regular array of light absorbing and/or blocking elements.
  • the reference pattern comprises different sub-patterns so that in use different regions of the data carrier are referenced to different ones of said sub- patterns .
  • the reader is provided with electro-optical means, such as an array of photo-detectors or a CCD camera, as viewing and/or detection means co-located with the plane of the interference pattern or an image thereof for recording and/or analysing said pattern.
  • electro-optical means such as an array of photo-detectors or a CCD camera
  • means such as a frame grabber and data store, is provided for capturing the different interference patterns produced, at successive instants in time, by corresponding movement of the data carrier relative to the reference means, so that the data corresponding to the different interference patterns may be subsequently processed. Combination of such data allows the embedded data to be extracted.
  • a method for reading embedded data comprises detecting the location of a plurality of elements of a data carrier; associating each element with one of at least two screens, each said screen having a respectively different extending regular array of points and each element having its centre of gravity coincident with a different one of said points; and associating embedded data with regions of one of said screens, said regions being distinct from each other.
  • Figure 1 is a diagrammatic representation of a halftone screen with phase embedded information in accordance with the invention.
  • Figure 2 is a diagrammatic representation of a reference pattern for use in decoding the information embedded in the screen of Figure 1.
  • Figure 3 is the result of combining the screen of Figure 1 with the pattern of Figure 2 i n accordance with the invention.
  • Figure 4 shows a reading device for use in accordance with the invention.
  • Figure 5 is a representation of the formation of a Moire pattern between a regular screen pattern and a spaced reference pattern.
  • Figure 6 is a two dimensional Moire caused by the rotation of a screen and a matching reference pattern.
  • Figure 7 shows diagrammatically how embedded data can be related to the phase of the grid pattern at a given location m accordance with the invention.
  • Figure 8 illustrates a system for capturing image data in accordance with the invention.
  • a printed screen pattern with phase embedded information is illustrated in Figure 1.
  • Each small area bounded by two pairs of adjacent lines of the regular hatched pattern 1 represents the cell or space available for an element of a halftone screen.
  • the hatched pattern is not itself printed, in practice, and is employed here for diagrammatic clarity. Instead, an array of substantially similar dots, each with its centre of gravity at the centre of its corresponding cell, is printed.
  • a diamond shape would produce the inverse (negative) of the hatched pattern illustrated with the gaps between adjacent dots providing the lines as illustrated.
  • the degree to which each dot fills its respective cell determines the weight of the screen and thus the density of the printed document. Providing this density is maintained, the position of each dot relative to its neighbours is not normally significant for conventional printed material.
  • the word "REAL" becomes clearly visible because there are substantial density changes in the regions where there is, through a mismatch, destructive interference between the patterns. This mismatch is caused by a relative lateral displacement, in effect a phase shift, between the screen of Figure 1 and the reference pattern of Figure 2 and, by definition, their corresponding arrays, each of which has the same spatial frequency in this embodiment.
  • the paper of the document comprises one substrate with two screens printed on it. One of these comprises the embedded data, the other its surroundings.
  • the data at any specific location comprises elements of one of the screens and is void of elements of the other screen.
  • a simple reader for viewing such embedded information is shown in Figure 4.
  • a carrier 6 supports the printed document 7.
  • plate 8 is lowered 10 and edge illuminated by a strip light 11.
  • some diffusion may be provided, if necessary, at its top surface, by incorporating a white backing layer underneath each of the opaque dots of reference pattern 9. The space between the dots the surface remains transparent for viewing.
  • the spatial frequency of pattern 9 need not be the same as that of the screen of document 7.
  • the formation of a so-called Moire pattern between these spatial frequencies is illustrated with the aid of Figure 5 which shows, in section, two patterns in a spaced configuration.
  • a printed pattern 12 is spaced from a transmission reference pattern 13 by a distance t .
  • this separation is achieved w ⁇ th a glass substrate as shown in Figure 4 and the actual thickness of this glass would be t x n, where n is the refractive index of the glass, in order to compensate for the latter.
  • the pitch of pattern 12 is Pa. and that of pattern 13 is p 2 .
  • the transmission of light is optimal in the directions indicated by the bundles of rays 14 to 17 thus forming a modulated light pattern of maximum contrast at plane 18.
  • a pattern (having a finite period of its own and often referred to as a Moire) is produced by a mismatch between the periods of a data-carrying printed pattern and a corresponding reference pattern.
  • This mismatch can be between the intrinsic wavelengths of each respective pattern, or can result from a deliberate misalignment of two regular and equivalent patterns.
  • the typical dimensions of the regions of constructive and destructive interference (in other words a dimension comparable to half the wavelength of the Moire) , when there is substantial alignment between the printed screen pattern and the reference pattern will be substantially greater than the spacing between the adjacent dots or elements comprising the screen or reference pattern.
  • the latter effect is illustrated in Figure 6.
  • two hatch patterns have been superimposed and one is rotated by a small amount with respect to the other.
  • the invention may be applied in a number of ways.
  • the information embedded m the printed screen may simply be made visible to the user by use of a suitable reference pattern.
  • the screen which carries the embedded information may be printed using ink which only becomes visible when subjected to UV light, when it fluoresces in the visible region.
  • the reference pattern may be composed of regions each of which has a different spatial frequency and/or orientation.
  • a series of data bits may be encoded within the document so that, when read either simultaneously or in sequence, such bits form a bar code or its two-dimensional equivalent.
  • a scanning device could be used to digitise the detailed structure of a printed document and the position of the digitised screen in certain regions of the document may be used as the spatial phase datum for other data-carrying regions. In this manner, the data is spatially phase encoded.
  • a single document may comprise screens in different colours.
  • the phase of each of these may be modified in accordance with the invention.
  • a specific colour may be used to provide the reference screen.
  • Patterns may be comprised of hexagonal close packed arrangements or have different periods in two orthogonal directions. Screen dots need not be square or diamond shaped, but may be elongate or round.
  • the embedded data may be encoded by use of a pattern having a pitch which substantially matches the reference pattern, whilst the surrounding pattern does not do so, either because its pitch is sufficiently different or because it is laid down at an angle which causes a substantial mismatch with the reference pattern.
  • a large time varying modulation of image density will be observed at any point in regions of embedded data, when the reference pattern is moved relative to it, and little or no modulation will be observed in the surrounding regions.
  • a suitable choice of CCD camera and image magnification may be used to ensure this.
  • the reference pattern is caused, by use of a small transducer, to move in three small increments, each of one quarter of the intrinsic pitch of the pattern, then four mages nay be observed.
  • the density value ( ⁇ to V-. ) of the four different but closely related images may be approximated by expressions having a periodic form, such as: -
  • V x M s ⁇ n(kx + p) + B (1)
  • V 2 M sm(kx + 90 + p) + B (2)
  • V 3 M s ⁇ n(kx + 180 + p) + B (3)
  • V 4 M s ⁇ n(kx ->- 270 + p) + B (4)
  • a video camera having the appropriate resolution and a suitable frame grabber and data store may be used to capture the images successively, provided the movement of the reference pattern relative to the data carrier is synchronised with the image capturing process.
  • a clear image of the embedded data may be extracted for display on a suitable display device, such as a graphics terminal .
  • this data may be directly processed by suitable software to carry out the required validation procedure or other data processing requirement.
  • Figure 8 illustrates apparatus for use in accordance with the above principles.
  • Document 23 is illuminated by lamp 24 and an image thereof is produced by lens 25 in the plane of a transparent plate 26 which carries a reference pattern (not shown).
  • the reference pattern matches that of the screen used to print the embedded data on to document 23, after allowing for the reduction in scale introduced by lens 25.
  • Condenser lenses 27A and 27B re-image the combination of the document's image and the reference pattern through the pupil of a CCD camera 28.
  • Provided the scale and orientation of the pattern on plate 26 match that of the image of document 23, a Moire pattern is created and captured by camera 28.
  • a position transducer 29 of the piezo-electric bimorph type has two electrodes.
  • the transducer When a voltage is applied across these through terminals 30A and 30B, the transducer flexes and moves plate 26 in its own plane. The distance moved is proportional to the voltage applied. In this way, the phase relationship between the pattern of the decoder (reference pattern) and the pattern of dots cn the printed document is altered in accordance with the invention.
  • frame store 31 is used to capture the resulting sequence of images which are then processed as already described.
  • a second transducer may provide movement of decoder 26 in a direction orthogonal to that provided by transducer 29. This can be advantageous where the array of dots m the pattern is two-dimensional in order to deal with registration errors, different screen orientations and two-dimensional analysis of the Moire as indicated above.
  • the reference pattern in the embodiment of Figure 8, there is no spatial separation between the reference pattern and the corresponding image of document 23, and this composite image is imaged directly onto the CCD array of camera 28. In this manner both embedded and conventionally printed data are captured without loss of resolution.

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  • Life Sciences & Earth Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • Editing Of Facsimile Originals (AREA)

Abstract

L'invention concerne un article qui comprend des données incrustées dans la trame (1) d'un procédé d'impression en demi-teintes. Les données (2-5) sont codées par le positionnement des centres de gravité d'éléments individuels ou points, composant une ou plusieurs trames utilisées pour imprimer un document, de façon différente de la variation normale du poids de ces points par rapport à leur espacement, ce qui donne des variations de densité pour les éléments imprimés en demi-teintes classiques. Un appareil rend immédiatement visibles ces données incrustées en donnant des interférences entre la trame (1) comportant les données (2-5) et un motif de référence à fréquence spatiale similaire. Une autre solution consiste à détecter ces données (2-5) par un procédé d'imagerie électronique dans lequel le mouvement commandé du motif de référence par rapport à la trame imprimée donne une série d'images qui sont traitées conjointement pour extraire les données incrustées (2-5). On peut remplacer l'utilisation d'un motif de référence physique par le balayage d'un document et l'établissement de références entre les positions des points de la trame en un endroit et des positions différentes. Cette invention est utile notamment dans le domaine des impressions de documents de sécurité car elle permet d'incorporer des dispositifs de sécurité et d'autres données incrustées dans des documents imprimés en demi-teintes.
PCT/GB1994/001710 1993-08-10 1994-08-08 Donnees imprimees incrustees, procede et appareil afferents WO1995004665A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB9316581.9 1993-08-10
GB939316581A GB9316581D0 (en) 1993-08-10 1993-08-10 Embedded printed data-method and apparatus
GB9322575.3 1993-11-02
GB939322575A GB9322575D0 (en) 1993-11-02 1993-11-02 Embedded printed data-metod and apparatus

Publications (1)

Publication Number Publication Date
WO1995004665A1 true WO1995004665A1 (fr) 1995-02-16

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PCT/GB1994/001710 WO1995004665A1 (fr) 1993-08-10 1994-08-08 Donnees imprimees incrustees, procede et appareil afferents

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Country Link
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Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999012742A1 (fr) * 1997-09-08 1999-03-18 The House Of Questa Ltd. Procede d'impression a securite renforcee permettant d'imprimer des documents proteges
EP0930979A1 (fr) * 1996-10-10 1999-07-28 Securency Pty. Ltd. Documents de securite a auto-verification
EP0961239A3 (fr) * 1998-04-16 2001-02-28 Digimarc Corporation Formation de filigranes numériques et de billets de banque
EP0981113A3 (fr) * 1998-07-31 2001-03-14 Digimarc Corporation Formation de filigranes numériques et méthodes pour documents de sécurité
WO2001039138A1 (fr) * 1999-11-29 2001-05-31 Ecole Polytechnique Federale De Lausanne (Epfl) Procedes et appareils servant a authentifier des documents grace a l'utilisation du profil d'intensite de motifs moirage
NL1015611C2 (nl) * 2000-07-04 2002-01-08 Security Brains B V Werkwijze voor het genereren van een beveiligingskenmerk, product voorzien van een basispatroon met ten miste ÚÚn beveiligingskenmerk en werkwijze en inrichting voor het detecteren van een beveiligingskenmerk.
US6343138B1 (en) 1993-11-18 2002-01-29 Digimarc Corporation Security documents with hidden digital data
WO2003019483A1 (fr) * 2001-08-22 2003-03-06 Mikhail Vasilievich Shovgenyuk Element graphique destine a la protection des billets de banque, papiers valeurs et documents et procede de fabrication
US6549638B2 (en) 1998-11-03 2003-04-15 Digimarc Corporation Methods for evidencing illicit use of a computer system or device
WO2003068522A1 (fr) * 2002-02-15 2003-08-21 Ascent Systems Software Limited Impression de securite
DE102004022976A1 (de) * 2004-05-10 2005-12-08 Clemens Brüntrup Offset-Reproduktion GmbH Steganographisches Druckverfahren und Verifikationssystem
US7488002B2 (en) 1998-07-02 2009-02-10 Securency Pty Limited Security and/or value document
EP1965581A3 (fr) * 2007-02-28 2009-11-18 Xerox Corporation Détection d'images à lustre différentiel
US8009893B2 (en) 1995-05-08 2011-08-30 Digimarc Corporation Security document carrying machine readable pattern
WO2017108035A1 (fr) * 2015-12-23 2017-06-29 Bundesdruckerei Gmbh Article imprimé, procédé d'authentification d'un article imprimé et système d'articles

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GB1138011A (en) * 1965-07-06 1968-12-27 Canadian Bank Note Co Ltd Improvements in printed matter for the purpose of rendering counterfeiting more difficult
GB1352839A (en) * 1970-07-31 1974-05-15 Nat Res Dev Methods of and apparatus for effecting optical measurement and analysis
DE3338828A1 (de) * 1982-10-28 1984-05-03 Dainippon Screen Seizo K.K., Kyoto Verfahren zur erzeugung von halbtonpunkten in einer halbtonplattenaufzeichnungsvorrichtung
US4649324A (en) * 1984-12-03 1987-03-10 Polaroid Corporation Method and apparatus for adjusting CRT geometry
DE3932505A1 (de) * 1989-09-28 1991-04-11 Gao Ges Automation Org Datentraeger mit einem optisch variablen element und verfahren zu seiner herstellung
EP0520363A1 (fr) * 1991-06-25 1992-12-30 Canadian Bank Note Company, Ltd. Images latentes contenant des phases décalées de microimpression
EP0534720A1 (fr) * 1991-09-24 1993-03-31 Raphael L. Levien Marques d'alignement

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1138011A (en) * 1965-07-06 1968-12-27 Canadian Bank Note Co Ltd Improvements in printed matter for the purpose of rendering counterfeiting more difficult
GB1352839A (en) * 1970-07-31 1974-05-15 Nat Res Dev Methods of and apparatus for effecting optical measurement and analysis
DE3338828A1 (de) * 1982-10-28 1984-05-03 Dainippon Screen Seizo K.K., Kyoto Verfahren zur erzeugung von halbtonpunkten in einer halbtonplattenaufzeichnungsvorrichtung
US4649324A (en) * 1984-12-03 1987-03-10 Polaroid Corporation Method and apparatus for adjusting CRT geometry
DE3932505A1 (de) * 1989-09-28 1991-04-11 Gao Ges Automation Org Datentraeger mit einem optisch variablen element und verfahren zu seiner herstellung
EP0520363A1 (fr) * 1991-06-25 1992-12-30 Canadian Bank Note Company, Ltd. Images latentes contenant des phases décalées de microimpression
EP0534720A1 (fr) * 1991-09-24 1993-03-31 Raphael L. Levien Marques d'alignement

Cited By (30)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6343138B1 (en) 1993-11-18 2002-01-29 Digimarc Corporation Security documents with hidden digital data
US6345104B1 (en) 1994-03-17 2002-02-05 Digimarc Corporation Digital watermarks and methods for security documents
US6771796B2 (en) 1994-10-21 2004-08-03 Digimarc Corporation Methods for identifying equipment used in counterfeiting
US8009893B2 (en) 1995-05-08 2011-08-30 Digimarc Corporation Security document carrying machine readable pattern
US7991182B2 (en) 1995-05-08 2011-08-02 Digimarc Corporation Methods for steganographic encoding media
US6449377B1 (en) 1995-05-08 2002-09-10 Digimarc Corporation Methods and systems for watermark processing of line art images
US6427020B1 (en) 1995-05-08 2002-07-30 Digimarc Corporation Methods and devices for recognizing banknotes and responding accordingly
EP1147912A2 (fr) * 1996-10-10 2001-10-24 Securency Pty. Ltd. Documents de sécurité incorporant des moyens de vérification
US6761377B2 (en) 1996-10-10 2004-07-13 Securency Pty Ltd Self-verifying security documents
EP0930979A1 (fr) * 1996-10-10 1999-07-28 Securency Pty. Ltd. Documents de securite a auto-verification
US6273473B1 (en) 1996-10-10 2001-08-14 Securency Pty Ltd Self-verifying security documents
EP0930979A4 (fr) * 1996-10-10 2000-01-12 Securency Pty Ltd Documents de securite a auto-verification
EP1147912A3 (fr) * 1996-10-10 2001-11-07 Securency Pty. Ltd. Documents de sécurité incorporant des moyens de vérification
US6467810B2 (en) 1996-10-10 2002-10-22 Securency Pty Ltd Self-verifying security documents
US7040664B2 (en) 1996-10-10 2006-05-09 Securency Pty Ltd Self-verifying security documents
WO1999012742A1 (fr) * 1997-09-08 1999-03-18 The House Of Questa Ltd. Procede d'impression a securite renforcee permettant d'imprimer des documents proteges
EP0961239A3 (fr) * 1998-04-16 2001-02-28 Digimarc Corporation Formation de filigranes numériques et de billets de banque
US7488002B2 (en) 1998-07-02 2009-02-10 Securency Pty Limited Security and/or value document
EP0981113A3 (fr) * 1998-07-31 2001-03-14 Digimarc Corporation Formation de filigranes numériques et méthodes pour documents de sécurité
US6724912B1 (en) 1998-07-31 2004-04-20 Digimarc Corporation Digital watermarking of physical objects
US6674886B2 (en) 1998-11-03 2004-01-06 Digimarc Corporation Method and system for recognizing security documents
US6549638B2 (en) 1998-11-03 2003-04-15 Digimarc Corporation Methods for evidencing illicit use of a computer system or device
WO2001039138A1 (fr) * 1999-11-29 2001-05-31 Ecole Polytechnique Federale De Lausanne (Epfl) Procedes et appareils servant a authentifier des documents grace a l'utilisation du profil d'intensite de motifs moirage
NL1015611C2 (nl) * 2000-07-04 2002-01-08 Security Brains B V Werkwijze voor het genereren van een beveiligingskenmerk, product voorzien van een basispatroon met ten miste ÚÚn beveiligingskenmerk en werkwijze en inrichting voor het detecteren van een beveiligingskenmerk.
WO2003019483A1 (fr) * 2001-08-22 2003-03-06 Mikhail Vasilievich Shovgenyuk Element graphique destine a la protection des billets de banque, papiers valeurs et documents et procede de fabrication
WO2003068522A1 (fr) * 2002-02-15 2003-08-21 Ascent Systems Software Limited Impression de securite
DE102004022976A1 (de) * 2004-05-10 2005-12-08 Clemens Brüntrup Offset-Reproduktion GmbH Steganographisches Druckverfahren und Verifikationssystem
DE102004022976B4 (de) * 2004-05-10 2010-09-16 Clemens Brüntrup Offset-Reproduktion GmbH Steganographisches Druckverfahren und Verifikationssystem
EP1965581A3 (fr) * 2007-02-28 2009-11-18 Xerox Corporation Détection d'images à lustre différentiel
WO2017108035A1 (fr) * 2015-12-23 2017-06-29 Bundesdruckerei Gmbh Article imprimé, procédé d'authentification d'un article imprimé et système d'articles

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