Patent ID: 12220934

DESCRIPTION OF THE INVENTION

FIG.1Ashows a sequence of the first eight halftone cell levels2ato2hat the base of a halftone mountain consisting of 8×8 halftone cells1. The lowest level2arepresents the largest possible halftone dot with here 64 exposed halftone elements. The halftone dot, labeled3a, thus has a complete 100% tone value of the color and is shown opposite. The uppermost eighth halftone level2hconsists of 57 exposed halftone dots, corresponding to a tone value of the halftone dot3hof 89%. In between here are six further halftone levels2b,2c,2d,2e,2fand2gwith 63 to 58 exposed and thus black halftone elements. This then includes the halftone dots3b,3c,3d,3e,3fand3gwith a non-exposure of all halftone elements near the corners. Next to this sequence of halftone cell planes, a corresponding gray wedge or halftone wedge4is shown for the halftone cell planes. This corresponds to the known amplitude modulated approach, where different tone values are represented by different planes.

FIG.1Bshows another sequence of the first eight halftone/raster cell levels at the base of a halftone/raster mountain consisting of 8×8 halftone/raster cells1, but with exposure of the halftone elements at other locations in the halftone cell. Thus, the lowest halftone cell2ais again fully exposed and corresponds to plane2aofFIG.1a. However, since the individual halftone planes are exposed in a different sequence, the shape of the halftone dot on the highest plane21fis different, but the tonal value of 89% and thus the halftone remain the same, as shown by the corresponding gray wedge or halftone wedge4to the halftone cell planes, which is identical toFIG.1A.

Between these planes, which are identical in gray tone, there are here six further halftone planes2b,21a,21b,21c,21dand21ewith 63 to 58 exposed and thus black halftone elements. In each case, the non-exposed halftone elements in the lower right corner135have been left unexposed, so that then the halftone elements3b,31a,31b,31c,31dand31eremain with a substantially lower right light area, while all other three halftone element areas near the corners are exposed and shown in black.

FIG.2Ashows a halftone mountain consisting of 64 halftone planes with halftone dots that become smaller towards the top, whereby a centrally symmetrical exposure with a central halftone cell area136is provided, as is the case for a typical prior art printed image. Reference numerals6,7and8relate to three plane regions of the halftone mountain, which are then described in greater detail inFIG.3A. Typically, halftone mounts are designed to produce square round, round, diamond or ellipsoidal halftone dots.

FIG.2Bshows a halftone mountain as shown inFIG.2A, but with halftone dots becoming smaller asymmetrically towards the top. The exposed halftone cells or halftone elements tend towards a corner with increasing exposure, in this case the halftone cell corner area137. Reference numerals12,13,14and15refer to four plane areas of the halftone mountain, which are then described in greater detail inFIG.3A.

FIG.2Cshows a halftone mountain as shown inFIG.2A, but with the halftone dot assignment changing asymmetrically in various ways towards the top, with the exposed halftone cells forming a U-shaped halftone dot138at mid-height and approaching the T-shape as halftone dot139towards the top. Further up, in the last levels before the peak141located at one, here the rear, side edge, a bar-shaped halftone dot140is formed. The reference signs12,13,14and15refer to four plane areas of the raster mountain, which are then described in greater detail inFIG.3A.

FIGS.2A,2B and2C, although shown independently of each other, are united by the corresponding gray wedge or halftone wedge5to the halftone cell planes shown inFIG.2A,FIG.2BandFIG.2Con the same drawing sheet next to them inFIG.2D. In other words, the tone value is the same for the corresponding height of the corresponding plane of the halftone mountain, so the halftone dot appears the same to the observer, as will be explained later in connection withFIG.4.

FIGS.3A,3B and3Cshow, on the one hand, the halftone mountain1according toFIG.2Ain three cut parts6,7or8on the left and a view of the halftone plane9,10or11with black colored halftone elements of the exposed elements of the uppermost halftone plane of the associated section6,7or8on the right. The bottom section6covers a tonal range from 100% to about 66%, the middle section7from 66% to 32%, and the top from 32% to 2%. The respective uppermost halftone planes9,10,11have a more or less symmetrical shape compared to each other. The bottom plane6represents a raster cell100with 8×8 raster elements102. In this raster cell100, some raster elements are now “printed” or exposed and thus form the raster dot101, which is shown here in black. Here, black can stand for any color in the given printing color space, including black on a white/bright background or vice versa.

FIGS.3D,3E,3F and3Gshow, on the one hand, the halftone mountain1according toFIG.2Bin four cut parts12,13,14and,15, respectively, on the left side and a view of the halftone plane of the associated section16,17,18and19, respectively, on the right side. The lowest section12covers a tonal range of 100% to about 69%, the lower middle section13covers a tonal range of 70% to 44%, the upper middle section14covers a tonal range of 43% to 16%, and the top section15covers 15% or less. The respective uppermost halftone planes16,17,18and11′ have the shape of a corner, which can also be seen as a diminishing triangle. For the middle upper plane14, it can now be clearly seen that for the raster cell100with its 8×8 raster elements102, there are now some raster elements printed asymmetrically with respect to the center, thus forming the asymmetrically printed raster dot101.

FIGS.3H,3I,3J and3Kshow, on the one hand, the halftone mountain according toFIG.2Cin four cut parts19,20,21and22on the left and a view of the halftone plane of the associated section23,24,25or11″ on the right. The lowest section19covers a tone value from 100% to about 70%, the lower middle section20covers a tone value from 69% to 37%, the upper middle section21covers a tone value from 36% to 25%, and the top 22 covers a tone value of 24% or less. The respective uppermost halftone planes23,24,25,11″ have shapes which develop from a circle open on the left, i.e. a U-shape23, via a T-shape24of the halftone elements102of the plane to a bar25or a single exposed halftone element102as a decentralized halftone dot11″. The bar25is located at a side edge150of the halftone cell100Essentially, at least for a predetermined number of tone values, a predetermined shape of the printed screen dot deviating from usual point-symmetrical or axis-symmetrical shapes.

FIG.4shows three halftone tiles26a,26band26c, each consisting of sixteen halftone cells, one above the other in a spatial representation, which are characterized by an increasing tonal value from halftone tile26ato halftone tile26c. At the same time, the halftone dots differ significantly in shape. For example, the individual halftone dots of halftone tile26aare a continuous line on the left edge of the respective halftone dot, from which a downwardly directed hook protrudes as an exposed area. The individual halftone dots of the halftone tile26bconsist of a continuous line at the left edge of the respective halftone dot, from which a line ending in front of the opposite edge is exposed in the upper third of the halftone dot. The individual halftone dots of the halftone tile26bcomprise a continuous line at the left edge of the respective halftone dot, from which a line ending before the opposite edge is exposed in the upper third of the halftone dot. The individual halftone dots of the halftone tile26cthen consist only of a continuous line at the left edge of the respective halftone dot. The gray areas27a,27band27cnext to it on the right side ofFIG.4, which are also superimposed, symbolize the perceived halftones or gray tones correspondingly from dark to light, seen from bottom to top.

FIG.5Ashows on the left a predefined halftone dot28aexecuted as a line and predefined for the exposure. Here, predefined means defined as electronic data for, for example, pixel-by-pixel laser exposure. This definition is then here the definition of a color in multicolor printing, preferably the top color. This results in a visually related object after printing, symbolized by the arrow160, which will have a slightly different shape29adue to the specifics of printing such as ink, substrate and machine parameters, to name a few. A copy made from this printout, i.e., a scan followed by a printout of the scan, will have deviations from the halftone dots printed in the original, which can be detected using machine pattern recognition. The cause of the halftone dot shapes of the copy30alie, for example, in inaccuracies of the scan, a renewed color separation and a repeated halftone image process in the printing of the then copied printout, all these factors which can be subsumed under copying errors being represented by the arrow170.

FIG.5Bshows a (lying) L-shaped halftone dot28bandFIG.5Cshows a hook-shaped halftone dot28c. The deviations during printing explained forFIG.5Aoccur here as a lying printed L29band as a printed hook29c, respectively, whereby then with a scan and a subsequent print copy30band30c, respectively, even further differences arise which can be detected with a pattern recognition.

FIG.6Ashows a sequence of four clearly distinguishable halftones. The tone becoming brighter from left to right is accompanied by a clearly changing halftone dot shape23,24,25and11′, respectively.

FIG.6bshows a sequence of ten halftones that are distinct from each other. The tone, which becomes brighter as it is shown from left to right in two rows, is accompanied by a changing halftone dot shape31,23,32,33,34,35,24,36,25and37.

These are predetermined halftone dot shapes corresponding to a known symmetrical tone value, whereby in the detection zone these halftone dot shapes replace the usual shapes. Different asymmetric halftone dot shapes with the same tone value can also be provided in different areas of a detection zone, or these are defined as different, i.e. two or more detection zones. In this case, these halftone mountain geometries are predetermined and the assigned plane (height) is defined in its corresponding tone value.

FIG.7shows a block diagram of a process representation of the encoding of the halftone dots up to the verification of the encoded halftone dots, starting from the provision of a first image for the evaluation of the optimal image sections for the intended encoding according to the invention38up to the authentication of the original print according to the instructions of a dedicated application program46.

It is assumed that for the printing area in a detection zone of an image on a package, the RIP process has been modified according to the invention. In this case, the halftone peaks have been designed in a decidedly and deterministically predetermined asymmetrical manner, so that these have been implemented in the printing process in accordance with the halftones to be printed. The modifications leading to a coding have been made in such a way that the print coverage of the corresponding color of the print coverage corresponds to the rest of the normal print image. Thus, there is a printed product, for example packaging, on which at least a part of the image, namely the part that lies in a detection zone, has been modified in relation to the RIP process in accordance with the invention. Several detection zones with different print occupancies can be provided.

This print image available to the user, which was created by printing according to arrow160inFIG.5, can now be an original or a copy, whereby a copy is usually characterized by the fact that someone has photographed or scanned an original, i.e. according to arrow170inFIG.5, in order to create a data set which is intended for printing a copy of the print image.

The process sequence shown inFIG.7is divided into a design phase, which comprises all process steps up to and including printing and definition of the descriptor, and the actual authentication phase, which comprises all actions of the user to accomplish authentication of the original print. During this phase, an electronic print template is generated with the halftone dots modulated according to the invention. Then, after printing, a predetermined image38is available, for example from the subject of a package, to be evaluated in terms of protection according to the invention. This subject can be assigned one or more detection zones39, i.e. one or more areas in which the CtP process has been modified according to the invention. Of course, the detection zone can also comprise the entire subject.

In the next step40, the halftone mountain geometry is determined by setting suitable threshold parameters in the halftone image process. This means that the dot shape to be applied to the original and thus to be printed is determined for a large number of halftone dots. This is not, as is usual with the amplitude-modulated halftone process, a symmetrical mapping of the halftone dot as inFIGS.1A and1nthe representation for three color halftones inFIGS.3A,3B and3C, but deterministically specified a clearly asymmetrical mapping, so that halftone dots16are detected for a darker color tone and halftone dots17or18for a lighter color tone.

Now, the halftone dots16,17or18to be detected are not optimal dots as shown inFIG.3D,3E or3F, but are of poorer quality as indicated inFIG.5AtoFIG.5Cfor print images29a,29band29c, but not as poor as print images30a,30bor30C indicate.

For this purpose, in the method, in a step41, a descriptor for the recognition of these characteristic halftone dot shapes is calculated and made available for authentication. The descriptor is a pattern recognition algorithm adapted to the pattern consisting of the halftone dot shapes. Descriptors can be predefined or are predefined and are adapted with regard to printing techniques used, printing papers, etc., whereby one speaks of training, whereby EP 2 921 989 A1 shows a possible procedure.

The descriptor can be trained and better matched to the sample in a further step42, which is not a mandatory step, but beneficial to increase the reliability of the authentication. Training can be based either on original prints, e.g., galley proofs, or on print-typical image changes due to ink and paper properties, printing processes, and machine-typical influences. Following step41or42, the descriptor is stored in a database in a storage step43and made available to the process control program via a server in a provision step44.

The following steps serve to prepare the mobile device for authentication and authentication itself. For this purpose, the user has installed an application program45for raster authentication according to the invention on a mobile device and, after synchronization with the server, has parameterized it with the selected descriptor script and, in an authentication step46, performs the necessary comparison according to the instructions of the application in order to decide whether the photographed detection zone is an original or a copy.

FIG.8A, followed byFIG.8B, shows an exemplary representation of an authentication carried out in accordance with the invention according to control instructions by a control program installed on a smartphone starting from the start of the same48via the touch screen47up to the display of the authentication result on this touch screen47as an output unit. The start occurs by touching the corresponding icon48on the display47of the mobile device in step54, which may be a tablet computer in addition to a smartphone, until the authentication result53is displayed in the last step59. In between, a display of the image data49taken with the camera of the portable portable communication device is switched on the screen in a preselection step55. This may be followed by the pre-setting of a rough visualization frame50in a selection step, where a guiding symbol51shifts the section to a detection zone52or, better, encourages the user to take an enlarged image of this section in a shifting step57. The usual aids such as autofocus or zoom are possible here. It can also be provided that the control program allows several detection zones52to be approached, i.e. steps56to58are repeated several times with different detection zones52. Essential is the recording of the detection zone52from an image section which then has a matrix of image points corresponding to the CCD or image sensor, which in a comparison step59are viewed either close to the original printed images29a,29bor29cof the predefined halftone dots or rather the printing of a copy of these after the images30a,30bor30c, with which the authentication result is then displayed.

REFERENCE NUMERALS LIST

1Raster element2Fully exposed raster cell (all raster elements are printing elements).2bAs2a, but one raster element unexposed2cAs2a, but two opposite halftone elements unexposed2dAs2a, but with three unexposed halftone elements at the corners.2eAs2a, but with four unexposed halftone elements at the corners.2fAs2e, but with two unexposed halftone elements of one of the corners, thus with a total of five unexposed halftone elements.2gAs2e, but with two unexposed halftone elements at each of the opposite corners, thus with a total of six unexposed halftone elements.2hAs2e, but with two unexposed halftone elements at each of three corners, for a total of seven unexposed halftone elements.3ato3hIdealized shape of halftone points corresponding to planes2ato2h21aAs2b, but two unexposed halftone elements at one corner, tone value as2c21bAs21a, but three unexposed halftone elements at one corner, tone value as2d21cAs2b, but four unexposed halftone elements at one corner, tone value as2e21dAs2b, but five unexposed halftone elements at one corner, tone value as2f21eAs2b, but six unexposed halftone elements at one corner, tone value as2g21fAs2b, but seven unexposed halftone elements at one corner, tone value as2h31ato31fIdealized shape of the halftone points corresponding to planes21ato21f4Gray wedge corresponding to the adjacent rows of halftone point shapes3ato3hor3a,3b,31ato31f.5Gray wedge corresponding to the adjacent representation of threshold values for a successive decrease in the exposure of halftone elements (halftone mountain). The gray wedge spans the entire spectrum of gray tones from 100% tonal value (black) to 0% (white).6Symmetrical halftone mountain with a tone value from 100% to 66%.7Symmetrical halftone mountain with a tone value of 68% to 32%.8Symmetrical halftone mountain with a tone value of 31% to 1.6%.9The halftone dot shape of the uppermost halftone mountain6is characterized by twenty-two unexposed halftone elements, the outer shape being more or less symmetrical.10The halftone dot shape of the uppermost halftone mountain7is characterized by forty-three unexposed halftone elements, with the outer shape being more or less symmetrical.11The halftone dot shape of the uppermost halftone mountain8is characterized by sixty-three unexposed halftone elements or consists of a single exposed halftone element.11′ exposed corner element11″ exposed single side edge element12Halftone mountain with a tone value from 100% to 69%. The shape of the halftone mountain is asymmetrical.13Halftone mountain with a tone value of 70% to 44%. The shape of the halftone mountain is asymmetrical.14Halftone mountain with a tone value of 43% to 16%. The shape of the halftone mountain is asymmetrical.15Halftone mountain with a tone value of 15% to 1.6%. The shape of the halftone mountain is asymmetrical.16The halftone dot shape of the uppermost halftone mountain12is characterized by 20 unexposed halftone elements, the outer shape being asymmetrical with essentially one corner unexposed.17The halftone dot shape of the uppermost halftone mountain13is characterized by 36 unexposed halftone elements, the outer shape being asymmetrical with essentially one corner unexposed.18The halftone dot shape of the uppermost halftone mountain12is characterized by ten exposed halftone elements, the outer shape being asymmetrical with substantially one corner exposed.19Halftone mountain with a tone value from 100% to 70%. The shape of the halftone mountain is strictly asymmetrical.20Halftone mountain with a tone value of 69% to 37%. The shape of the halftone mountain is strictly asymmetrical.21Halftone mountain with a tone value of 36% to 25%. The shape of the halftone mountain is strictly asymmetrical.22Halftone mountain peak with a tone value of 24% to 1.6%. The shape of the raster mountain is strictly asymmetrical.23The halftone dot shape of the uppermost halftone mountain19is characterized by nineteen unexposed halftone elements, the outer shape being strictly asymmetrical and essentially unexposed in the center and at one corner.24The halftone dot shape of the uppermost halftone mountain20is characterized by twenty-four exposed halftone elements, with the outer shape approaching a “T”.25The halftone dot shape of the uppermost halftone mountain21is characterized by sixteen exposed halftone elements, with the outer shape corresponding to a bar on one side of the halftone cell.26aRaster tile consisting of sixteen raster cells, where the exposed raster elements take the form of a bar on the left side of the raster cells.26bRaster tile consisting of sixteen halftone cells, where the exposed halftone elements take the form of two bars aligned at a 90° angle to each other. The tone value is higher than in the halftone tile shown above.26cHalftone tile consisting of sixteen halftone cells, with the exposed halftone elements assuming a complex shape. The tonal value is even higher than in the aforementioned halftone tiles.27ato27cVisually perceived gray values corresponding to the halftone tiles described in26ato26c.28aBar-shaped halftone dot according to output file for exposure28bAngular halftone point according to the output file for the exposure.28cHalftone point with double angle shape according to output file for exposure29ato29cDistortions of the halftone dot shapes in the original print (exemplary) starting from the specified halftone dot shapes according to halftone dots28ato28c30ato30cDistortions of the halftone dot shapes in the copy (exemplary) starting from the halftone dot shapes of the original according to halftone dots29ato29c31to37Asymmetrically shaped halftone dots with decreasing tonal value and constantly changing, simpler shapes.38Evaluate a given image, e.g. from the subject of a package, with regard to protection according to the invention.39Selecting at least one detection zone40Determine raster mountain geometry by setting appropriate threshold parameters in the raster image process.41Calculate descriptor for recognition of characteristic halftone dot shapes.42Train descriptor (not a mandatory step). The training can be done either on the basis of original prints, e.g. from galley proofs, or by print-typical image changes due to color and paper properties, printing process and machine-typical influences43Deposit descriptor on a database44Make descriptor available via a server45Install an app for the halftone authentication according to the invention on a mobile device and parameterize it with the selected descriptor script after synchronization with the server.46Execute authentication as instructed by the app47Display of a mobile device, e.g. a smartphone48Symbol of an app for the authentication method according to the invention49Image to be examined with regard to originality50Gross orientation framework51Visual guidance symbolism52Detection zone; the mobile device is now in a suitable position to take an image of the detection zone.53Authentication result54Start App55Select image56Selecting the approximate position of the detection zone57Software (app) guides the user to the optimal position58Execute authentication59Authentication result is presented135Unexposed corner136Exposed central tip137Exposed corner tip138U shaped halftone dot139T shaped halftone dot140Bar shaped halftone dot141Exposed tip at one side edge150Side edge of a halftone cell