WO2008100173A1

WO2008100173A1 - Printed product production method and a printed product produced by means of said method

Info

Publication number: WO2008100173A1
Application number: PCT/RU2007/000073
Authority: WO
Inventors: Alexei Vadimovich Zaitsevsky
Original assignee: Zuev, Boris Alexandrovich
Priority date: 2007-02-15
Filing date: 2007-02-15
Publication date: 2008-08-21

Abstract

The inventive method for producing a printed product can be used for the mass production of printed products, for example banknotes, securities etc.,which are provided with counterfeit protection means in the form of a latent array of encoded digital information. The inventive method consists in transmitting a main visible image to a carrier with the aid of an ordered screen and in introducing inhomogeneity items into the structure of said screen for transmitting a latent encoded digital information array to the same carrier. According to said invention, the width of each area of the ordered screen used for placing one element is selected according to the value of a corresponding bit of digital information to be encoded, wherein the elements which form the main image are located at the same distance from the front boarder of the area in the reading order of encoded information irrespective of the tone colour of the transmissible image.

Description

METHOD FOR PRODUCING PRINTED PRODUCTS AND PRINTED PRODUCTS MADE BY THIS METHOD.

Technical field

The invention relates to printing and, more specifically, relates to a method for the manufacture of printed products containing, in addition to the visible image, hidden coded digital information, as well as a printed product made in this way.

State of the art

The coding of digital information in an array of graphics is known. In particular, in patent EP 1605395, A, a method is described for encoding digital information in a graphic array of dots by shifting them relative to a regular position, but not as a raster transmitting a visible image.

Known as described in patent EA 002934, In a method of manufacturing a printed product by transferring to a medium using an ordered raster the main visible image and introducing inhomogeneities into the structure of this raster to transmit a coded array of digital information to the same medium. The following possible variants of introducing the indicated inhomogeneities are listed in this patent: changing the shape of individual elements of the raster, changing the angle of construction of the element of the raster, shifting the individual elements of the raster, changing the density of the elements, raster, changing the period, changing the size. Some of these changes concern only one element of the raster, the change of which is significant. Some changes require additional changes to neighboring elements of the raster for visual compensation, as a result of which such an element should not be considered as an independent element, but as a group of elements, while the area required for encoding one bit increases. In the description of this patent, a fragment of the raster structure containing the modified element and its surrounding elements is called a supercell. Compensation of visual distortion of shades caused by a change in one element of the raster is carried out by changing the shape and area of neighboring elements in such a way that the total area of the supercell elements is the same, both in the case of the changed element and in the case of ordinary raster elements. However, in printing there is the effect of dot-dot dot gain, this effect cannot be described by a linear function, and it has different meanings for different types of raster. The spreading effect can be neglected if the raster is large enough, but in this case the protective effect is reduced, the amount of encoded information is also reduced, and the screened image is rippled in the eyes. Otherwise, the dot gain effect will tone out areas with different raster elements. Possible algorithms for compensating for the nonlinear spreading effect for an inhomogeneous raster are not presented in this method, although their necessity is mentioned. On the other hand, recognition of information hidden in a raster is no less difficult than encoding it. Despite the well-known information presented in the description of the patent about the imperfection of existing printing methods, the issue of stable decoding has not been analyzed.

Disclosure of invention

The basis of the invention is the task of creating such a method of manufacturing a printed product containing, in addition to the main image, hidden encoded digital information that would allow quite simple and reliable decoding of the recorded digital information and at the same time ensure accurate transmission of the main image at a high recording density of digital information.

The problem is solved in that in the method of manufacturing printed products by transferring to the medium using an ordered raster the main visible image and introducing inhomogeneities into the structure of this raster to transmit to the same medium a hidden encoded array of digital information, according to the invention, the width of each region of the ordered raster, designed to accommodate one element, choose more or less depending on the value of the corresponding bit of digital information to be encoded In this case, the elements forming the main image are placed at the same distance from the front border of the region (hereinafter cells) in the direction of reading the encoded information regardless of the transmitted hue of the visible image.

In this case, it is advisable to compensate for the spreading effect by linearizing separately for a raster with a larger and for a raster with a smaller width of the region intended to accommodate one element.

In this case, it is possible to determine the value of the encoded bit of digital information by the value of the interval between the boundaries of the transitions from the background to the filling of two adjacent raster elements in the horizontal (lowercase) direction.

In order to more accurately convey the image, it is preferable to use elements of a circular shape to fill in the light and dark portions of the rasterized image and elements having the shape of a “line” to transmit neutral tones.

To facilitate decoding, it is desirable that the encoded digital information be duplicated repeatedly within the rasterized image.

In this case, it is advisable to record duplicated information in rows, placing them one under the other with each subsequent row shifted to the left by an integer bit value approximately equal to the square root of the total number of bits of the encoded information, with the formation of blocks having essentially equal height and width.

In a preferred embodiment, neighboring blocks contain identical information, but recorded in reverse order.

In the most preferred embodiment, the number of blocks and their location in the raster of the main image is selected taking into account the possibility of restoring all encoded digital information from at least several fragments of different blocks if the whole block could not be recognized.

The problem is also solved by the fact that a printed product containing a medium with an ordered raster transferred to it by the main visible image and a hidden encoded array of digital information is manufactured by the method described above.

Brief Description of the Drawings

The invention is further explained in the description of specific variants of it implementation and the accompanying drawings, in which: FIG. 1 shows an enlarged view of a fragment of a raster with cells of different widths in accordance with the encoded digital information; FIG. 2 is a section of a printed product according to the invention containing a visible image and encoded digital information; FIG. 3 is a fragment of a raster with encoded digital information grouped in blocks.

Advantageous Embodiments of the Invention

A method of manufacturing a printed product according to the invention consists in applying a main visible image, as well as a hidden coded array of digital information, to a medium, for example, a sheet of paper, cardboard or to the surface of a package. The cells of the printed raster, with which the image is transmitted, according to the invention, have a different width, which depends on the bit value of the encoded digital information. A wider cell 1 is used to encode the value of the “O” bit (see FIG. 1), and a narrower cell 2 is used to encode the value of the “1” bit. In this case, all elements of the raster 3 are located at the same distance from the front boundary of the corresponding cell from the hue of the image transmitted by this element. In the described method, when encoding digital information, the repetition period T of the raster elements 3 is significant. A larger period Tl corresponds to zero, a smaller period T2 corresponds to one. It is algorithmically easier to determine the position of the transition from the background to the fill for each element, rather than calculate the position of the center of the element. When encoding information on the magnetic strip of a plastic card, the position of the polarity reversal, rather than the peak of the magnetic field, is also determined. But unlike the principle of recording onto a magnetic strip, this method does not require synchronization of the hue stream read in one or several lines with a certain predetermined sequence for subsequent decoding. In addition, in contrast to a number of well-known coding solutions for printed products, where it is necessary to compare the coordinates of a significant point with the coordinates of a certain standard, which itself does not contain information, in the method according to the invention each element 3 of the raster is significant and its the value can be set even in a short excerpt of the raster. In order to be able to determine the encoded value of the raster element from the transition from the background to the fill, its front (conditionally, from left to right) edge is always placed in the same place of a separate cell, regardless of the percentage of its filling. An example of cells with different percentage filling, but with a constant leading edge position (transition from background to fill) of the elements is shown in FIG. 2. Here, all the elements of the raster are adjacent to the front border of the corresponding cell, however, they can be located at a certain distance from this border, it is only necessary to fulfill the condition of equality of this distance for all elements of the raster.

In addition, this figure shows that raster elements of various shapes were used to convey neutral and contrasting shades of the image. In cells with 50% coverage, the shape of the raster element is selected — the line (zone I in FIG. 2), for the lighter and darker portions of the image — the circle (zones II and III, respectively). Thanks to this modification of the form, the color rendering quality when printing visible and latent images remains at the same level as with conventional screening.

Encoding information in a raster is only possible where the raster is present. However, there are many places on rasterized images where the filling is absent or is continuous. Ideally, for encoding hidden information, the percentage filling over the entire image area should be in the range of 30-70%. This image looks gray and opaque. In addition, even in such an image, some of the elements of the raster may not be printed or erased in the process of using a printed product with a printed image. In a preferred embodiment of the method for reliable reading of recorded digital information, it is repeatedly duplicated within the rasterized image. The easiest option is string coding, like placing text on a piece of paper. But in a motley image, it is easier to find a certain concentric region with a satisfying raster filling condition than a significantly elongated strip into which the required amount of information could be recorded.

In the most preferred embodiment, the information is recorded not in rows from raster elements, but in blocks of the most compact form. To form such blocks, information is encoded in rows (from left to right), each the next line exactly repeats the previous one (meaning digital content) and is located in the raster below the previous one, but shifted to the left by an integer value of bits, approximately equal to the square root of the total number of bits of encoded information. This ensures cyclic duplication of the array of encoded information. Thanks to this arrangement of information, its reading becomes possible both in line-by-line decoding and in decoding by blocks, the size of which vertically and horizontally is essentially the same. The number of blocks and their location in the raster of the main image is chosen so that all encoded digital information can be restored from at least several fragments of different blocks.

Due to this, after the recognition algorithm detects duplicated information and then determines the coordinates of all blocks, the information can be restored even from fragments from different blocks, if not a single whole block in the image could be recognized.

Since the read and highlighted information is cyclically closed, the beginning and end of the recording are not defined. To indicate the beginning and end of the sequence, a certain digital code can be added to the digital array, which will lead to an increase in the volume of the encoded array. The preferred option is to record encoded information in neighboring blocks in reverse order. In this case, the algorithm identifies the end and the beginning of the recording based on the “mirror” display in the recognized information.

To indicate the beginning of the encoded sequence and its end, two bits are needed - the zero bit at the beginning and one at the end. Thus, the correct decoding sequence for a given digital array and its copy recorded in the reverse order is detected. Information recorded in the reverse order provides the required redundancy of information stored in the raster to the same extent as information recorded in the normal direction.

In FIG. Figure 3 shows a fragment of a raster structure, divided into cells intended for filling with individual elements of the raster. In this case, the width of the cells has a size corresponding to the value of the bits of the encoded digital information. In this figure, the letters A, B, C, and D indicate, as an example, areas of possible reading of encoded information. Letters A and B indicate examples of line reading areas, examples of block reading are denoted by the letters C and D. In the reading examples denoted by the letters A and C, the recognized information has the usual sequence, and in examples B and D the reverse. The first and last bits in the sequence are overhead and indicate, respectively, the beginning and end of the recording. The selection of a significant block is carried out on the basis of the repetition of information. The determination of the beginning and end in a certain closed sequence is carried out by determining the boundaries of the “mirror” display of information and the values of the first and last bit in the selected sequence.

The maximum possible amount of encoded information depends on how the provided image is suitable for encoding and what kind of raster line is used. For example, under ideal conditions with a lineature of 500 lpi, one square inch of the image can store 24 kilobytes of information or ZZOOO characters in 6-bit encoding. The maximum value of the lineature should be determined based on the technical capabilities of the printing equipment, and for stable decoding, multiple duplication of the encoded array is important. The software designed to build rasters with hidden information evaluates the encoding result and provides the user with information about the encoding ability and the actually discovered redundancy of the recorded information in the generated raster. When encoding digital information, any character encoding tables, any data compression algorithms, as well as encryption can be used.

Since cells 1 and 2 of the raster have different widths, the dot gain for the raster elements formed in different cells will be different. In this method, the errors introduced by the spreading effect are overcome by linearization, which is carried out separately for the raster with cells 1 of greater width and for the raster with cells 2 of smaller width. Linearization is carried out according to the results of test printing, on the basis of which the exact ratio between the specified hue of the rasterized image and the printed result for all shades for both raster variants is established. When constructing a raster for each type of cell, the corresponding linearization schedule is used. Thanks to this linearization, it is possible to print images storing hidden information with the same lineature as simple images without loss of quality. Quality loss is possible only with significant increase in lineature. For example, with a minimum size of an element that can be reproduced by a conventional offset printing machine of 20 microns and a lineature of 500 lpi, the smallest reproducible hue in wide cell 1 will be 13%, and in narrow cell 2 it will be 19%. These losses can be invisible when rasterizing backgrounds containing a certain ripple or texture. In addition, the indicated value of 500 lpi is very high, and not every scanner can distinguish hidden information even on the original. To read information from a raster, the maximum lineature of which exceeds 200 lpi, a scanner with an optical resolution of more than 600 dpi should be used.

The advantage of this method of manufacturing printed products is the actual use of only two lineatures with a small difference in their values, as a result of which the raster looks relatively smooth. In addition, a sufficiently high recording density is provided, since in this case, not groups of elements are used to record information, but individual elements, each of which is significant.

Industrial applicability

The method according to the invention is suitable for use in the mass production of printed products having anti-tampering means in the form of a hidden array of coded digital information, for example, in the manufacture of such protective articles as banknotes, securities, labels, packaging, etc. P.

Claims

CLAIM

1. A method of manufacturing printed products by transferring to the medium using an ordered raster the main visible image and introducing heterogeneities into the structure of this raster for transmitting to the same medium a hidden encoded array of digital information, characterized in that the width of each region of the ordered raster is designed to accommodate one element, choose greater or lesser depending on the value of the corresponding bit of digital information to be encoded, while the elements forming the new image is placed at the same distance from the front of the region in the direction of reading the encoded information, regardless of the transmitted hue of the visible image.

2. The method according to p. 1, characterized in that the compensation of the dot gain effect is carried out by linearization separately for the raster with a larger width of the region and for the raster with a smaller width of the region intended to accommodate one element.

3. The method according to p. 1 or 2, characterized in that the value of the encoded bit of digital information is determined by the size of the interval between the boundaries of the transitions from the background to the filling of two adjacent raster elements in the horizontal direction.

4. The method according to p. 1, characterized in that they use elements of a circular shape to fill in the light and dark areas of the rasterized image and elements having the shape of a "line" to transmit neutral colors.

5. The method according to p. 1, characterized in that the encoded digital information is repeatedly duplicated within the rasterized image.

6. The method according to p. 5, characterized in that the duplicated information is written in lines that are arranged one below the other with each subsequent line shifted to the left by an integer value of bits approximately equal to the square root of the total number of bits of the encoded information, with the formation of blocks having, essentially equal height and width.

7. The method according to p. 6, characterized in that the neighboring blocks contain identical information, but recorded in the reverse order.

8. The method according to p. 6, characterized in that the number of blocks and their location in the raster of the main image is selected taking into account the possibility of restoring the entire