JP2012187738A - Printed matter capable of discriminating genuineness, and method of authenticating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed matter capable of discriminating genuineness of securities, such as a bank note, a stock certificate, a bond, various certificates, and important documents, and to provide a method of authenticating the printed matter.SOLUTION: The printed matter includes at least one image on a substrate, has a center point for each image, in which a plurality of concentric printing element units centered on the center point are concentrically arranged, the respective concentric image units are concentrically arranged so that the plurality of printing elements have at least two kinds of intervals according to information to be embedded in an area between a starting circle having a first radius from the center point and an ending circle having a second radius, and a frequency component according to the information to be embedded is extracted when analyzing the frequency with respect to the area formed of the plurality of concentric printing element units.

Description

  The present invention relates to a printed matter capable of authenticating authenticity for precious printed matter such as banknotes, stock certificates, securities such as bonds, various certificates and important documents, and an authentication method for the printed matter.

  Countermeasures against counterfeiting and alteration are important elements in printed matters such as banknotes, stock certificates, securities such as bonds, various certificates and important documents. There are two methods for preventing counterfeiting and alteration of printed materials: a method of using a design with a lot of geometric patterns in the design, and a method of embedding invisible information in the printed material by some means and reading the invisible information by some means.

  A typical example of the former is one that uses a geometric pattern such as a background pattern, a colored pattern, or a relief pattern that is widely used in the design of securities prints, etc., but forgery or alteration using the geometric pattern. As a preventive measure, there is one in which a pattern is constituted by a set of curved lines having a basically fixed line width as shown in FIG. In domestic banknote manufacturing factories, it is called the “Saimon pattern” and in overseas banknote manufacturing factories, it is also called Guilloche. Such a pattern of line expression is excellent in counterfeiting and has been used with the intention of preventing counterfeiting on banknotes and the like since the 19th century.

  On the other hand, as shown in FIG. 1B, there is a geometric pattern constituted by a set of solid portions in which a printed image line forms a certain area. In domestic banknote factories, when it is formed by an intaglio printing method, it is sometimes called a white pattern.

  These patterns take into account design such as the design of printed matter, and use colors that are difficult to be extracted by a photoengraving device or reproduced by a copying machine, or have a complicated image line configuration for scanning input / output of a copying machine and a scanner. Although the role of anti-counterfeiting has been heightened by generating moire, recently there has been a drawback that the anti-counterfeiting and anti-counterfeiting effect has not been brought about due to the advent of highly functional photoengraving devices or copiers. is there.

  In addition, as shown in FIG. 1C, when formed by the offset printing method, it may be called a grid pattern. The pattern as shown in FIG. 1 (c) is also called a shimultan pattern at overseas banknote factories, and such a surface expression pattern started in the 20th century when offset printing was developed.

  The purpose of preventing the counterfeiting of the pattern shown in FIG. 1C is that the respective contours of a plurality of graphic areas are printed at a constant distance of several hundred μm, and the plurality of graphic areas are different colors. Is being printed by. That is, since the same pattern cannot be expressed unless it has high printing accuracy, it has been considered that there is an anti-duplication effect. However, today, plate making / printing methods with high accuracy such as CTP have been developed, and the effect as a forgery prevention measure applying high printing accuracy has already been lost.

  Therefore, as a solution for such a problem, a machine reading inspection method that can process a large amount and at high speed in authenticity determination is widely adopted. Today's machine-reading inspection methods for printed materials include tributaries such as functional inks such as magnetic ink, infrared reflection absorption ink, and fluorescent ink, and detection of materials such as fibers, materials, and chemicals that form printing media. However, these technologies are caused by specific electromagnetic waves that cannot be detected by humans. Many of these technologies depend on the suitability of materials for producing printed matter, and are only applied to products that are economical in terms of production cost. I can't.

  Further, as a method that does not particularly take into consideration the production cost of the printed matter, there is an optical reading method for a pattern on the printed matter to which a printing material such as visible visible ink can be applied. OCR, OMR, bar code, two-dimensional code, etc. are known as relatively easy optical reading methods, but the figures used in these optical reading methods have no design and are used for existing products. If the design, specification changes are required.

  In addition, these optical reading methods are also widely available in the market, and since the code can be seen as a printed image line, there is a risk of decoding and tampering, which is insufficient for use as a countermeasure against forgery and alteration. It is.

  Furthermore, there is a series of techniques generally called electronic watermarks as a method for providing reading information without changing the design such as the design by the optical reading method. An electronic watermark is also called a concealed image or a digital watermark, and is a technique for embedding copyright information in a document file or a printed material of a copy function or a DTP technique with advanced functions. As a well-known representative technique for printed materials, there is a method called frequency utilization type.

  Electronic watermarks are said to have little deterioration in frequency characteristics even in duplicates. Recently, digital watermarks are often applied to digital images distributed on the Internet for the purpose of copyright protection. In addition, since it has an effect on printed matter, it is often used for posters.

  It is a continuous gradation (photographic gradation) pattern that an electronic watermark can exert the most effect. Since the continuous tone (photo gradation) pattern is multi-valued image data, there is sufficient redundancy, so not only the frequency-based type but also the pixel replacement type, the pixel space usage type, the quantization error diffusion type, etc. A method is proposed, and there are many literatures and patent applications.

  However, a set of curved lines such as a background pattern, a stencil pattern, and a relief pattern used for securities is basically a binary image, so there is little redundancy and it is difficult to embed an electronic watermark. The problem is that reading accuracy is low due to weak reading signals.

  Therefore, the present inventors have described "a printed matter and a discrimination method capable of determining authenticity and a method for embedding information in the printed matter" (Patent Document 1), "a printed matter and a discrimination method capable of determining authenticity, and the printed matter." According to the “embedding method of information” (patent document 2) and “printed material and authentication method of the printed material” (patent document 3), a print image line composed of a free curve group such as a background pattern and a colored pattern is mechanically generated. There has already been filed a printed matter characterized by identification. However, since these inventions are techniques applied only to the chromatic pattern by the line representation shown in FIG. 1 (a), the so-called white chromatic pattern in FIG. It cannot be applied to the pattern of surface expression as shown in Sasame Saimon pattern.

Japanese Patent Application No. 2001-001519 Japanese Patent Application No. 2002-050606 Japanese Patent Application No. 2005-096758

  The present invention has been made in view of the above points, and in a printed matter having artistic properties such as securities composed of securities line drawings and the like, by modulating the line images for securities at a level that humans cannot visually recognize. The purpose is to embed information without losing its artistic effect. In addition, in order to strengthen the signal of information used in the conventional information embedding and reading technology, it is achieved by performing concentric line processing on the solid portion where the printed image line forms a certain area. It is.

  The present invention comprises at least one image on a substrate, has a center point for each image, and a plurality of concentric image line units centered on the center point are concentrically arranged, and each concentric image line is The unit is concentric so that there are at least two types of intervals depending on information to be embedded in a plurality of lines in a region between a starting circle having a first radius and an ending circle having a second radius from the center point. The frequency component corresponding to the information to be embedded is extracted when frequency analysis is performed on an area formed by a plurality of concentric image line units.

  Further, at least two kinds of intervals according to the present invention are printed matter capable of authenticating authenticity, which is selected from a plurality of preset intervals set for each piece of information to be embedded.

  In addition, the stroke width of the start circle, the stroke width of the end circle, and the stroke widths of the plurality of stroke lines in the region between the start circle and the end circle of the present invention are any one selected from 30 μm to 80 μm. The non-drawing line width of the plurality of drawing lines in the region between the start circle and the end circle is selected from at least two types of non-drawing line widths from 30 μm to 380 μm. It is a printed matter capable of authenticating authenticity.

  The image of the present invention is a printed matter capable of authenticity determination, wherein the image is divided into a plurality of regions by white lines.

  Further, the image of the present invention is a printed matter capable of authenticating authenticity, characterized in that white information is formed in the image.

  In addition, the image of the present invention further includes a plurality of curved lines having a width different from the line width and the non-line width formed on the image, and further comprising a plurality of curved lines in or around the image. Possible prints.

  In addition, the image of the present invention further includes a dummy image, and the dummy image is formed in or around the image, and is solid-printed at a density substantially equal to the density of the image. Print.

  Further, the present invention is an authentication method for printed matter capable of authenticating authenticity, wherein the reading unit obtains image data including an area formed by a plurality of concentric image line units, and the image processing unit converts the image data into image data. A frequency analysis is performed, a frequency component is generated, and a determination unit authenticates a printed matter that can be determined by comparing and comparing the frequency component and a frequency component according to predetermined information to be embedded. Is an authentication method for printed matter that can be determined as authenticity.

  According to the present invention having the above-described configuration, information embedded in a digital device such as a scanner or a copying machine can be detected by a digital device such as a scanner or a copying machine, but the Fourier transform or specific frequency can be detected on the digital device. The embedded information can be analyzed by performing operations such as extraction and inverse Fourier transform.

  In addition, since the image line used in the present invention cannot recognize the information with human vision even in single color printing, the artistic effect of the print image line is not reduced.

  In addition, compared to the technology that embeds and reads invisible information described in the prior art, the signal strength of the information is very large because the image processing with high regularity is given a highly regular signal processing. Easy to read.

  Because of these effects, the present invention activates actions such as reading invisible information given to banknotes, securities, various certificates, important documents, etc. with a digital device and stopping the operation of the digital device based on that information. It is effective to make it.

It is the figure which showed the example of the line drawing for securities used for securities, bills, etc. It is explanatory drawing which showed the FFT pattern obtained by inputting the image of the printed matter which has arbitrary figure areas with an optical scanner, and also Fourier-transforming. It is explanatory drawing which showed the structure of the concentric drawing line unit which has a predetermined | prescribed width | variety in a normal line direction, and is each comprised concentrically centering | focusing on the center point P. FIG. 10 is an explanatory diagram showing 13 intensity characteristics in an FFT pattern obtained by inputting a printed product having a plurality of concentric line units with an optical scanner and further performing Fourier transform. It is a pattern block diagram which has one type of figure area group among several figure areas. FIG. 10 is an explanatory diagram showing 13 intensity characteristics by FFT patterns obtained by inputting a printed matter having a plurality of graphic areas with an optical scanner and further performing Fourier transform. FIG. 10 is an explanatory diagram showing 13 intensity characteristics with an FFT pattern obtained by inputting a printed matter having a plurality of graphic regions and dummy images or line drawing patterns with an optical scanner and further performing Fourier transform. It is explanatory drawing by which the printed matter which has a some figure area | region and a dummy image or a line drawing pattern was shown. It is a figure which shows the authentication method of the printed matter which can authenticate authenticity.

  Embodiments of the present invention will be described below in detail with reference to the drawings based on examples. The line drawing for securities used for securities, banknotes, etc. is composed of a plurality of lines made of curves or straight lines as shown in FIG. In the present invention, an image line that constitutes such a line drawing for securities is referred to as a fine line.

  In addition, as for the pattern of line expression shown in FIG. 1 (a), it is possible to mechanically identify the fine line by the prior art, but it is shown in FIG. 1 (b) or FIG. 1 (c). It was not possible to mechanically recognize the surface expression pattern. Therefore, a fine line was applied to provide a desired spatial frequency in the surface expression pattern. The principle will be described with a simple graphic example.

  For example, the pattern shown in FIG. 2A is an 8-bit pattern composed of 1024 × 1024 pixels in which a graphic region 2 printed in the same print color on the printed material 1 is image-input with a resolution of 1200 dpi by an optical scanner. It is a grayscale image. FIG. 2B is an FFT pattern obtained by Fourier transforming the pattern shown in FIG. In addition, in order to explain the feature of the spatial frequency in an easy-to-understand manner, a frequency intensity graph is overlaid on the fourth quadrant of the FFT pattern in FIG. In the pattern configuration shown in FIG. 2, there is no significant feature in the spatial frequency.

  Therefore, the printed matter of the present invention is characterized in that the image line configuration of the graphic region 2 is arranged with concentric image lines, and the intervals in the normal direction of the concentric image lines are different. FIG. 3 is an explanatory diagram conceptually showing the image line structure of the present invention. It has a graphic group consisting of image lines L printed in the graphic area 2, and a plurality of image lines L are formed by a plurality of concentric image line units 3 having the same configuration in concentric circles with the center point P as the center. Yes.

  FIG. 3 (a) briefly explains the image line configuration of the present invention. The concentric drawing unit 3 has a predetermined width (referred to as “unit width”) in the normal direction, and is configured concentrically around the center point P. Specifically, the concentric image line unit 3 is composed of, for example, the image lines L1 to L6, and the image lines L1 to L6 have diameters so as to maintain a predetermined interval around the center point P. They are arranged in different sizes. The spatial frequency can be characterized by the difference in the distances d1 to d5 in the normal directions of the image lines L1 to L6. In the present invention, this is confidential information on the printed matter 1. Here, the intervals d1 to d5 are distances from the center to the center of each of the adjacent image lines in the image lines L1 to L6. The start and end of repetition of the concentric image line unit 3 are the same, and the image line L1 and the image line L6 are shared.

  For example, the interval may be determined in advance corresponding to the profile constituting the information to be embedded in advance. Here, the intervals d1 to d5 are set by a profile table as shown in Table 1.

  In order to embed information matching the profile name “kiuchi” in the concentric drawing unit 3 based on the profile table of Table 1, the interval d1 between the drawing line L1 and the drawing line L2 is set to 60 μm. The distance d2 between the line L2 and the image line L3 is 90 μm, the distance d3 between the image line L3 and the image line L4 is 150 μm, the distance d4 between the image line L4 and the image line L5 is 110 μm, and the distance d5 between the image line L5 and the image line L6 is set. What is necessary is just to arrange | position to 170 micrometers, respectively.

  The unit width is 580 μm, which is the sum of these intervals. In the graphic region 2, the concentric drawing unit 3 having such a configuration is arranged along the normal direction of the concentric circle. As shown in FIG. 3B, the image line width W of the image lines L1 to L6 is set to be smaller than the minimum interval of the intervals d1 to d5 in order to avoid coupling with adjacent image lines. Here, it was set to 33 μm.

  The same effect can be obtained even if the relationship between black and white (negative / positive) is reversed. For example, the image lines L1 to L6 may be formed in white, and the intervals d1 to d5 may be formed in black.

  Next, a means and method for identifying the information of the printed matter in which the information is embedded by the above information embedding method will be described. The printed matter 1 is read by an image input device such as a scanner, and the read result is held as bitmap data (an example of “digital image data” of the present invention). Then, the bitmap data is Fourier transformed.

  The pattern shown in FIG. 4A is an 8-bit grayscale image composed of 1024 × 1024 pixels obtained by inputting the print 1 with an optical scanner at a resolution of 1200 dpi. The graphic region 2 on the printed material 1 is composed of a plurality of concentric image line units 3 shown in FIG. 3, and the concentric image line units 3 constituting the graphic region 2 are thin image lines, so that they are slightly visible. It is a grade which can confirm a striped pattern. FIG. 4B is an FFT pattern obtained by Fourier transforming the pattern shown in FIG. Similarly to FIG. 2, in order to explain the feature of the spatial frequency in an easy-to-understand manner, a frequency intensity graph is superimposed on the fourth quadrant of the FFT pattern of FIG. 4B.

An example of how the embedded information is identified will be described using the FFT pattern obtained by the Fourier transform shown in FIG. 4B as an example. There are several specific means for identifying the embedded information of the printed matter according to the present invention from the FFT pattern. Here, three means are listed.
(1) In a read image processing apparatus such as a computer, an FFT pattern corresponding to predetermined embedded information is stored in advance, and the FFT pattern of bitmap data read from a printed material is compared with an FFT pattern stored in advance. Identification (pattern matching).

(2) A density distribution curve of a k-th peak of Fourier transform data corresponding to predetermined embedding information (referred to as a density distribution curve that is the kth peak from the inside out of the peaks in the FFT pattern) is prepared in advance. This is compared with the density distribution of the k-th peak of the Fourier transform data of the bitmap data read from the printed matter.

(3) The intensity I (k) at the k-th peak position of the FFT pattern of the bitmap data read from the printed material is calculated by the following equation (1).

  Here, N is the number of concentric drawing units 3 in the whole drawing line, n is the number of concentric drawing lines in the concentric drawing unit 3, and xij is a concentric drawing given by the following equation (2). The numerical value which normalized the space | interval of the i-th concentric drawing line in the line unit 3, and the j-th concentric drawing line with the unit width | variety is represented.

  By recognizing the value of the intensity I (k) at the k-th order peak position of the FFT pattern from these equations (1) and (2), it is easy to solve the simultaneous equations by solving the simultaneous equations. It is possible to determine the arrangement, thereby identifying the embedded information.

  As an example, the identification of the printed matter 1 having the concentric drawing unit 3 in which the profile “kiuchi” shown in Table 1 is embedded will be described. It is assumed that a digital image of the printed material 1 is read and subjected to Fourier transform to obtain an FFT pattern. In the image input device, it can be immediately seen from the first-order peak position of the FFT that the unit width is 580 μm.

  Then, by reading the relative intensity of the FFT pattern at the 1st, 2nd, 3rd, 4th and 5th order peaks, respectively, applying this to the above formulas 1 and 2, and solving the simultaneous equations by the least square method, It is possible to solve the arrangement of the divisional concentric drawing lines in the concentric drawing line unit 3, that is, the arrangement of the intervals between the concentric drawing lines.

  As described above, since the peak intensity of a clear FFT pattern can be obtained, information can be embedded and read by giving variations to the concentric drawing unit 3 and arranging them regularly. An array of five intervals of interval d1 to interval d5 is used, but there is no limitation on the number of intervals, and an FFT having a characteristic peak position frequency and intensity corresponding to any interval sequence. It can be recognized from the pattern.

  In this embodiment, Fourier transform is used to analyze the embedded information. However, the method is not limited to Fourier transform as long as the method can physically analyze the structure of the unit drawing line.

  As described above, by including a concentric drawing line in an arbitrary graphic region, the characteristics of the spatial frequency in the concentric drawing line are shown as intensity characteristics in the FFT pattern. Note that the intensity characteristic varies depending on the interval between the concentric drawing lines. The difference in pattern can be identified by the difference in intensity characteristics in the FFT pattern. The printing color used for the graphic area 2 is not limited at all. Furthermore, the number of graphic areas 2 is not limited at all.

  From the above, the printed matter capable of authenticating authenticity of the present invention includes at least one image on the substrate, has a center point for each image (in the above description, a graphic), and has a plurality of center points. Concentric drawing units are arranged concentrically, and each concentric drawing unit is arranged in a region between the center point P and the end circle having the first radius R1, as shown in FIG. A plurality of lines are arranged concentrically so as to have at least two kinds of intervals according to information to be embedded. Further, the radius R1 is a start circle, and a plurality of lines are arranged concentrically so as to have at least two kinds of intervals according to information to be embedded in a region between end circles having the second radius R2. Furthermore, the radius R2 is a start circle, and a plurality of lines are arranged concentrically so as to have at least two types of intervals according to information to be embedded in a region between end circles having a third radius R3. That is, the printed matter capable of authenticating authenticity is characterized in that a frequency component corresponding to information to be embedded is extracted when frequency analysis is performed on an area formed by a plurality of concentric image line units. The starting point or starting circle line forming the image, the ending circle line, and the starting point or the area between the starting circle and the ending circle are drawn individually. It is in a situation where it is not visible or difficult to see. The image can be visually recognized with a striped pattern such as a ripple with the naked eye. In order to visually recognize with a striped pattern such as a ripple with the naked eye, the line width of the start circle, the line width of the end circle, and the line widths of a plurality of lines in the region between the start circle and the end circle are 30 μm. It is a drawing line unified to any drawing line width selected from -80 μm, and the non-drawing line width of the plurality of drawing lines in the region between the start circle and the end circle is from 30 μm to 380 μm. At least two types of non-line widths must be selected. The substrate described above is not particularly limited, such as paper and plastic sheet. Further, the design of the image described above is not particularly limited as long as a plurality of concentric image line units can be formed in the region. The image line configuration for Embodiment 1 and Embodiment 2 shown below is the same as described above.

  The present invention has a plurality of fine lines having regularity in the graphic area of the surface expression, so that it can be identified in a high-resolution input image by a digital device such as a scanner or a copying machine, but it is visually recognized by humans. By assigning difficult fine and regular parts, analyzing the correlation of the intervals of line drawings for digital securities on the obtained printed matter, and identifying the information embedded in the printed matter, it is possible to determine authenticity It is possible to perform actions such as stopping the operation of a digital device such as a copying machine used for counterfeiting based on the information.

(1) Embodiment 1
The first embodiment is an example in which the effect is exhibited even if the graphic area including the concentric drawing lines has an arbitrary area shape and arrangement. The first embodiment will be described in detail with reference to the drawings.

  As described above, the pattern shown in FIG. 1B is an example of a pattern composed of surface representations, and is composed of a geometric pattern composed of a set of portions that can be observed in a solid shape in which a printed image line forms a certain area, Sometimes referred to as a white pattern. In addition, the pattern shown in FIG. 1C is an example of a pattern composed of a surface expression, which is also called a sash pattern or shimultan pattern. It is. For example, as shown in the pattern configuration diagram having a plurality of graphic regions in FIG. 5, the graphic region group 4 includes all of the patterns shown in FIG. That is, FIG. 5A is characterized in that the pattern shown in FIG. 4A is divided into a plurality of regions by white lines. Further, the present invention is not limited to the outline drawing line, and can form outline information in the image. The information referred to here is not particularly limited to characters, figures, designs, and the like. The printed matter capable of authenticating authenticity according to the present invention forms an outline image or outline information, so that the forger cannot determine that the information is embedded in the image. It becomes.

  FIG. 6A is an 8-bit grayscale image composed of 1024 × 1024 pixels obtained by inputting the printed material 1 having the pattern configuration shown in FIG. 5 with an optical scanner at a resolution of 1200 dpi. The graphic region group 4 arranged in a grid pattern on the printed matter 1 is composed of the concentric drawing unit 3 shown in FIG. 3, and the concentric drawing unit 3 constituting the graphic region 4 is a thin drawing line. Only a slight stripe pattern can be confirmed visually. Although the center of the concentric drawing line is the center of the entire pattern shown in FIG. 6A, the effect of the present invention is not hindered wherever the center of the concentric drawing line is.

  FIG. 6B is an FFT pattern obtained by Fourier transforming the pattern shown in FIG. As in FIG. 2, in order to explain the feature of the spatial frequency in an easy-to-understand manner, a frequency intensity graph is superimposed on the fourth quadrant of the FFT pattern in FIG. 6B. Since the same concentric drawing unit 3 as in FIG. 4 is used, the frequency intensity graph matches the intensity ratio in FIG. Similarly to FIG. 4, if the value of the intensity I (k) at the k-th peak position of the FFT pattern is recognized by the above Equation 1 and Equation 2, the concentric circles in the unit can be easily solved by solving the simultaneous equations. It is possible to determine the arrangement of the line-shaped image lines, thereby identifying the embedded information.

  As described above, by including a concentric drawing line in an arbitrary graphic region, the characteristics of the spatial frequency in the concentric drawing line are shown as intensity characteristics in the FFT pattern. Note that the intensity characteristic varies depending on the interval between the concentric drawing lines. The difference in pattern can be identified by the difference in intensity characteristics in the FFT pattern. The print colors used for the graphic region group 4 may all be the same color, or may be different for each graphic region 4. Further, the printing color is not limited at all.

(Embodiment 2)
The image formed on the printed matter that can be determined as authenticity is formed with concentric lines that are visually recognized as striped patterns by the naked eye, in addition to areas that are visually recognized as striped patterns with the naked eye. It is possible to further include a dummy image made of solid printing formed at the same density as that of the remaining area. For example, as shown in FIG. 7, it is possible to further include a line drawing pattern 6 in addition to the graphic area 5. The printed matter capable of authenticating authenticity according to the present invention forms a dummy image or a line drawing pattern, so that the forger cannot determine that information is embedded in the image. However, when a line drawing pattern is formed in an image, it is necessary to use a line drawing pattern having a spatial frequency component different from the spatial frequency component of a region formed by concentric drawing lines. That is, the line drawing patterns having different spatial frequency components need to be formed with a width different from the line drawing width and the non-line drawing width formed in the region visually recognized as a striped pattern by the naked eye formed with concentric drawing lines. .

  FIG. 7B is an FFT pattern obtained by Fourier transforming the pattern shown in FIG. As in FIG. 2, in order to explain the feature of the spatial frequency in an easy-to-understand manner, a frequency intensity graph is superimposed on the fourth quadrant of the FFT pattern in FIG. 7B. Since the same concentric drawing unit 3 as in FIG. 4 is used, the frequency intensity graph matches the intensity ratio in FIG. Similarly to FIG. 4, if the value of the intensity I (k) at the k-th peak position of the FFT pattern is recognized by the above Equation 1 and Equation 2, the concentric circles in the unit can be easily solved by solving the simultaneous equations. It is possible to determine the arrangement of the line-shaped image lines, thereby identifying the embedded information.

  Further, as shown in FIG. 8, in addition to the graphic area 5, it is possible to further include a solid printed graphic area 7 as a dummy image. Since the graphic area 7 is composed of solid printing formed at a density substantially equal to the density of the graphic area 5 formed by the concentric drawing unit 3, the difference between the graphic area 5 and the graphic area 7 is recognized by visual observation. I can't do it. This combination of graphic areas makes forgery more difficult.

  As described above, by including a concentric drawing line in an arbitrary graphic region, the characteristics of the spatial frequency in the concentric drawing line are shown as intensity characteristics in the FFT pattern. Note that the intensity characteristic varies depending on the interval between the concentric drawing lines. The difference in pattern can be identified by the difference in intensity characteristics in the FFT pattern. The print colors used for the graphic area group 5 may all be the same color, or may be different for each graphic area 5. Further, the printing color is not limited at all.

  The present invention is a technique for embedding invisible information or an image composed of lines of a group of lines composed of concentric lines at regular intervals. On the other hand, since the image forming means for printing by today's digital copying machine is generally operated at 600 dpi or less, the image line structure shown in the present embodiment is a solid pattern in a copy form. End up. As a result, the information to be embedded can be made secret information, and the effect of preventing forgery is improved.

  A slight striped pattern (individual lines cannot be observed with the naked eye) is observed in the graphic area formed by concentric lines, but at least part of the graphic area is solid with the naked eye. In order to be visually recognized, a part of the concentric line unit 3 is selected from a line width of 30 μm to 80 μm and a non-line of line selected from a non-line width of 30 μm to 380 μm. Must be arranged alternately and have portions. The standard of the image line width and the non-image line width is derived from the resolution in general human vision based on physiological knowledge. In the Landolt ring target used in the visual acuity test, the minimum readable threshold that is simply converted under certain conditions (distance 250 mm, visual acuity 1.0) is about 73 μm in slit width. When the image line width of 30 μm to 80 μm is 80 μm or more, each image line can be seen independently, and a region formed by concentric image lines cannot be visually recognized as a striped pattern like a ripple. On the other hand, when the Landolt ring index is converted into a 5 × 5 matrix, a figure of about 380 μm or less cannot be read with the naked eye. Therefore, if the non-image line width of 30 μm to 380 μm is 380 μm or more, each image line can be seen independently, and a region formed by concentric image lines cannot be visually recognized as a striped pattern like a ripple. . Further, the anti-counterfeiting effect can be enhanced by having the above configuration in a part of the concentric drawing unit 3 so as not to be resolved by a commercially available digital hard copy. On the other hand, when the image line width and the non-image line width are 30 μm or less, there may be a problem in reproducibility in the offset printing method. That is, in the transfer of ink from the printing plate to the printing substrate, the expansion of the image line is unavoidable due to the physical flow characteristics caused by the printing pressure (also called dot gain in the printing industry). For example, when the expansion of the image line spreads by 10 μm around the image line, if the non-image line width is designed to be 20 μm, the image lines are naturally combined. As a result, an image line selected from an image line width of 30 μm to 80 μm and a non-image line selected from a non-image line width of 30 μm to 380 μm are alternately displayed on a part of the concentric image line unit 3. This is because, by having the portions arranged, the difference between the image line and the non-image line provided in the concentric image line unit 3 is clarified and the frequency intensity at the spatial frequency is increased.

  The outline of the region may be formed by an image line. Further, the plurality of areas may have different print colors.

  With the above configuration, the region formed by the concentric drawing lines is visually recognized as a solid shape with the naked eye although a slight striped pattern is observed, so that information appears in the concentric drawing lines at first glance. Since it cannot be determined that it has been granted, it has an excellent anti-counterfeit effect. In addition, when a frequency analysis is performed on a region formed by concentric drawing lines, a predetermined frequency component is extracted, so that it is possible to determine whether the region is true or false.

  As shown in FIG. 9, the authentication method for a printed matter that can be determined as authenticity is obtained by acquiring image data including a region formed by a plurality of concentric image line units by a reading unit and converting the image data into image data by an image processing unit. Performs frequency analysis, generates frequency components, and authenticates printed matter that can be checked for authenticity by comparing and comparing frequency components according to predetermined information to be embedded by the determination unit It becomes.

  Since the frequency component is a component of a region formed by concentric circles, it is possible to extract a frequency component that is clearer than before, so erroneous recognition of a predetermined frequency component in comparison verification There is nothing to do.

  The concentric drawing line is preferably a concentric drawing line or a curved drawing line obtained by extracting a part of the concentric drawing line. By using a concentric drawing line or a curved drawing line obtained by extracting a part of the concentric drawing line, a clear frequency component can be obtained.

  It is preferable that the pattern formed on the printed matter capable of authenticity determination is a pastel color. Pastel color is a term that commonly refers to colors with low saturation and high brightness, and there is no clear standard in various color marking systems, but securities such as banknotes, stock certificates, bonds, various certificates and important Pastel patterns have been used for a long time because of the effect of being difficult to reproduce in the background pattern used for precious printed matter such as documents. By forming a pattern with such pastel colors, design harmony can be achieved even for products that conventionally require anti-counterfeiting, and at the same time, it is effective as an anti-counterfeiting measure. It works.

  In addition, in a straight line instead of a concentric circle, when obtaining an inverse spatial distance from the spatial frequency coordinate, for example, when viewed with an FFT pattern, the display from the low frequency to the high frequency extends from the center (0 point) of the two-dimensional coordinate axis to the entire periphery. Is displayed. In such a spatial frequency calculation method, a concentric drawing line is characterized in that it tends to appear as a strong signal around the entire circumference. For example, FIG. 2 (b), FIG. 4 (b), FIG. 6 (b). This is because it is possible to know a clear intensity characteristic as seen in the frequency intensity graph displayed in the fourth quadrant on the FFT pattern shown in FIG. The intensity characteristic of the spatial frequency is also affected by the brightness of the printing color. Generally, the intensity characteristic becomes clearer as the brightness is lower, but sufficient intensity characteristic can be obtained even in the pastel color as described above. . Therefore, forming a pattern with concentric lines is advantageous in identifying information embedded in a printed material.

  As mentioned above, although the embodiment of the present invention has been described based on examples, the present invention is not limited to such examples, and is effective not only in monochrome printing but also in the case of using a plurality of colors. Will never change. Therefore, it goes without saying that there are various embodiments within the scope of the technical matters described in the claims.

DESCRIPTION OF SYMBOLS 1 Printed matter 2 Graphic area 3 Concentric drawing unit 4 Graphic area 5 Graphic area 6 Line drawing pattern 7 Graphic area d1 Interval d2 Interval d3 Interval d4 Interval d5 Interval L Image line L1 Image line L2 Image line L3 Image line L4 Image line L5 Image Line L6 Image line P Center point R1 Start circle (end circle)
R2 start circle (end circle)
R3 start circle (end circle)
W Stroke width

Claims (8)

Comprising at least one image on a substrate;
Each image has a center point, and a plurality of concentric drawing units centered on the center point are concentrically arranged,
Each of the concentric image line units has at least two types according to information to be embedded in a plurality of image lines in a region between a start circle having a first radius and an end circle having a second radius from the center point. Are arranged concentrically so as to have an interval of
A printed matter capable of authenticating authenticity, wherein a frequency component corresponding to the information to be embedded is extracted when frequency analysis is performed on an area formed by the plurality of concentric image line units.   2. The printed matter capable of authenticating authenticity according to claim 1, wherein the at least two kinds of intervals are selected from a plurality of preset intervals for each piece of information to be embedded. The stroke width of the start circle, the stroke width of the end circle, and the stroke widths of the plurality of stroke lines in the region between the start circle and the end circle are any one selected from 30 μm to 80 μm It is a line with the same line width,
2. The non-image line width of a plurality of image lines in a region between the start circle and the end circle is selected from at least two types of non-image line widths from 30 [mu] m to 380 [mu] m. Or the printed matter of 2 which can authenticate authenticity.   4. The printed matter according to claim 1, wherein the image is divided into a plurality of regions by white lines in the image. 5.   5. The printed matter according to claim 1, wherein white information is formed in the image.   2. The image according to claim 1, further comprising a plurality of curved lines having a width different from a line width and a non-line width formed on the image, in the image or around the image. The printed matter according to any one of 5, wherein the authenticity can be determined.   2. The image according to claim 1, wherein the image further includes a dummy image, and the dummy image is formed in or around the image and is solid-printed at a density substantially equal to the density of the image. The printed matter according to any one of 6, wherein the authenticity can be determined. A method for authenticating printed matter according to any one of claims 1 to 7,
The reading unit obtains image data including an area formed by the plurality of concentric drawing line units,
The image processing unit performs frequency analysis on the image data to generate a frequency component,
A printed matter capable of authenticating authenticity is characterized by authenticating the printed matter capable of determining authenticity by comparing and comparing the frequency component and a frequency component corresponding to predetermined information to be embedded by a determining unit. Authentication method.

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