JP2012141729A - Authenticity determination method, authenticity determination device, authenticity determination system, and color two-dimentional code - Google Patents

Abstract

PROBLEM TO BE SOLVED: To build a system which is inexpensive and relatively robust for an authenticity determination method using metamerism.SOLUTION: An image reading unit 110 acquires multiband images by causing an image pickup device 111 to image an identification code, which has predetermined information coded therein, to be printed on a printing medium by using metamerism. Based on each of the multiband images, for each band, an area pixel value determination unit determines pixel values of first and second areas in which two colors in a relation of metamerism are to be printed, respectively. A spectral spectrum estimation unit 233 estimates a spectral reflection spectrum of the first area by using learning data of a color in the first area and the pixel value for each band in the first area, and a spectral reflection spectrum of the second area by using learning data of a color in the second area and the pixel value for each band in the second area. An authenticity determination unit 236 determines authenticity of the identification code by using the spectral reflection spectrum of the first area and the spectral reflection spectrum of the second area.

Description

  The present invention relates to an authenticity determination method, an authenticity determination device, an authenticity determination system, and a color two-dimensional code using conditional colors.

  The main anti-counterfeiting measures for printed materials include those that use inks that cannot be seen unless they are exposed to special illumination, such as fluorescent inks and infrared inks, those that apply processing that cannot be reproduced by general printing presses such as watermarks and micro letters, and holograms For example, they are difficult to counterfeit and cannot be copied because they are glossy, and are used for cash vouchers and banknotes.

  Also, some forgery prevention measures are printed using two colors of ink having a relation of conditional color (metamerism) (see, for example, Patent Document 1). Conditional color refers to a phenomenon that appears to be the same color under a natural light source such as sunlight or a fluorescent lamp, but looks different when viewed through a special light source or through a filter. Forgery prevention measures using conditional color are used, for example, for cherry blossom petals in passports. When copying with a color copier, a difference occurs in the colors of the two types of ink that were the same color under normal light, and it is found that the product is a counterfeit product. Many of the anti-counterfeiting technologies mentioned above improve the fastness by combining a plurality of methods.

  In recent years, a method of photographing irregular paper fiber information to obtain unique authenticity information, a paper material in which the polarizing fiber is inserted, and utilizing the pattern change of the polarizing fiber observed through the polarizing plate are utilized. A method for determining authenticity and a method using DNA information as an authenticity determining material have been developed. These are very robust, but expensive and require a highly accurate detector for reading.

  Incidentally, in the field of identification codes, two-dimensional codes have become widespread instead of one-dimensional codes (mainly bar codes). A representative example of the two-dimensional code is a QR code (registered trademark). QR codes are not limited to black, and color QR codes are also widely used in advertisements and magazines. It is also resistant to dirt, and most mobile phones now have a reading function.

  Another example of the color two-dimensional code is a color code (ColorCode (registered trademark)). The color code is a two-dimensional code that uses four-color patterns of red, green, blue, and black. It is coded with color information and color arrangement information, and design is added if the color arrangement is not destroyed. be able to. A technique has also been proposed in which this color code is printed with fluorescent ink, is normally invisible, and can be read when photographed by irradiation with ultraviolet rays (see, for example, Patent Document 2).

Japanese Patent Publication No. 60-58711 JP 2008-181477 A

  As described above, since the conventional general authenticity determination methods improve the fastness by combining a plurality of methods, the manufacturing cost tends to increase as the fastness increases. In recent years, forgery technology has also progressed, and it is difficult for the naked eye to determine authenticity with a high-definition scanner or printer, and even special ink, watermarks, and holograms can be forged. In addition, the authenticity determination method with a high degree of robustness alone is expensive to manufacture and requires an expensive device for authentication.

  In this regard, the authenticity determination method using colors of the same condition can be created at a relatively low cost. However, it is difficult to determine by visual observation alone, and a high-accuracy detector such as a spectroscope capable of reading spectral reflection spectrum information is necessary for authenticity determination.

  The present invention has been made in view of such a situation, and an object thereof is to provide a technique for constructing an inexpensive and relatively robust system in an authenticity determination method using conditional color.

  An authentication method according to an aspect of the present invention is an identification code in which predetermined information is encoded, and an identification code to be color-printed on a print medium using a condition color is imaged by an imaging element to obtain a multi-code. Obtaining a band image; obtaining a pixel value of each of the first area and the second area for which two colors having the same color relationship are to be printed from each of the multiband images; and The spectral reflectance spectrum of the first area is estimated using the color learning data of one area and the pixel value of each band of the first area, and the color learning data of the second area and the pixel value of each band of the second area. The authenticity of the identification code is determined using the step of estimating the spectral reflectance spectrum of the second area using the, and the spectral reflectance spectrum of the first area and the spectral reflectance spectrum of the second area. Comprising the steps of, a.

  Another aspect of the present invention is also an authenticity determination method. The method includes an identification code in which predetermined information is coded, and an identification code to be color-printed on a printing medium using a color of the same condition is captured by an image sensor to obtain a multiband image; Obtaining the pixel values of the first area and the second area to be printed with two colors having the same color relationship from each of the multiband images, the multiband pixel values of the first area, Determining the authenticity of the identification code using the multi-band pixel values of the two areas.

  Yet another embodiment of the present invention is an authenticity determination system. This authenticity determination system includes an imaging device for imaging an identification code encoded with predetermined management information, and an authenticity determination device for determining the authenticity of the identification code captured by the imaging device. In the system, the identification code is an identification code to be color-printed on the print medium using a condition color, and an identifier for accessing the authenticity determination device is further coded. An image pickup device for picking up a multiband image of the identification code, an identification code reading unit for detecting management information and an identifier from the multiband image picked up by the image pickup device, and an identity determination device using the identifier via a network And a first communication unit that accesses the management information and the multiband image to the authenticity determination device. The authenticity determination device includes a second communication unit that receives management information and a multiband image from the imaging device, and a first area and a second area in which two colors having the same color are printed for each management information. A comparison area holding unit for holding, a comparison area acquiring unit for acquiring the first area and the second area from the comparison area holding unit corresponding to the management information received by the second communication unit, and receiving by the second communication unit An area pixel value specifying unit that specifies, for each band, pixel values of the first area and the second area acquired by the comparison area acquiring unit from each of the multiband images that are acquired, and for each band of the specified first area The spectral reflectance spectrum of the first area is estimated using the pixel value and the color learning data of the first area, and the pixel value and the color learning data of the second area for each band of the specified second area are estimated. The authenticity of the identification code is determined using the spectral spectrum estimation unit that estimates the spectral reflection spectrum of the second area, and the spectral reflection spectrum of the first area and the spectral reflection spectrum of the second area estimated by the spectral spectrum estimation unit. An authenticity determination unit.

  Yet another embodiment of the present invention is an authenticity determination device. This apparatus is an identification code that is to be color-printed on a print medium using conditional color, and has a first area and a second area on which two colors having predetermined management information and conditional color are to be printed. Image pickup for picking up multiband images of identification codes in which position information of each area, true values of colors of the first area and the second area, and true values of color differences of the first area and the second area are coded The pixel values of the first area and the second area from the element, the identification code reading unit for detecting the position information, the true value of the color and the true value of the color difference from the image captured by the image sensor, and the multiband image, respectively. Is determined by estimating the spectral reflection spectrum of the first area using the pixel value for each band of the specified first area and the learning data of the color of the first area. Spectral spectrum estimation unit for estimating spectral reflection spectrum of second area using pixel value for each band of second area and color learning data of second area, and color of first area detected by identification code reading unit The true value of the second area and the measured value of the color calculated from the spectral reflectance spectrum of the first area estimated by the spectral spectrum estimation unit, the true value of the color of the second area detected by the identification code reading unit, and The second comparison with the color measurement value calculated from the spectral reflectance spectrum of the second area estimated by the spectral spectrum estimation unit, and the true value of the color difference detected by the identification code reading unit and the spectral spectrum estimation unit are estimated. An authenticity determination unit that determines the authenticity of the identification code based on a third comparison of the measured values of the color difference between the first area and the second area based on the measured values.

  Yet another aspect of the present invention is a color two-dimensional code. This color two-dimensional code is a color two-dimensional code in which predetermined information printed on a print medium is coded, and each two-color code is printed in two colors having a condition of the same color in the two-dimensional code area. Two regions are formed.

  Note that any combination of the above-described components and a representation of the present invention converted between a method, an apparatus, a system, a recording medium, a computer program, and the like are also effective as an aspect of the present invention.

  According to the present invention, an inexpensive and relatively robust system can be constructed in the authenticity determination method using conditional color.

It is a figure which shows an example of a QR code. It is a figure which shows an example of the spectral reflection spectrum of the color a and the color a 'which have the relationship of a condition color. FIGS. 3A to 3D are diagrams for explaining a method of creating conditional color matching. FIGS. 4A to 4E are diagrams for explaining a color arrangement example using conditional color in the color QR code. It is a figure which shows an example of the spectral sensitivity characteristic of the color filter with which an image pick-up element is mounted | worn. It is a figure which shows the structure of the authenticity determination system which concerns on Example 1. FIG. 3 is a flowchart for explaining an operation example of the authenticity determination system according to the first embodiment. It is a figure for demonstrating a color comparison area and trimming. FIGS. 9A to 9C are diagrams illustrating the relationship between the measured value of the difference spectrum calculated by the difference spectrum calculation unit and the true value of the difference spectrum held in the difference spectrum true value holding unit. It is a figure which shows the structure of the authenticity determination apparatus which concerns on Example 2. FIG. 10 is a flowchart for explaining an operation example of the authenticity determination device according to the second embodiment.

  First, as a premise for explaining the authenticity determination method for a color two-dimensional code according to the embodiment of the present invention, a method for creating the color two-dimensional code will be described. Hereinafter, an example in which a QR code is used as the two-dimensional code will be described.

  FIG. 1 is a diagram illustrating an example of a QR code. First, a QR code reading procedure will be briefly described. A QR code reader (not shown) (for example, a mobile phone, a smartphone, a dedicated device, etc.) images the QR code. Then, the captured image is grayed out and binarized according to the brightness. The QR code reader recognizes the direction and position of the captured QR code by detecting the cutout symbols 10 formed at the three corners except the lower right corner of the QR code. The QR code reader rotates and moves the image based on the recognition result, and cuts out a QR code area from the image.

  Next, the QR code reader detects the timing pattern 20 from the QR code and counts the number of modules in the timing pattern 20 to determine the QR code version. The timing pattern 20 is formed between the cut-out symbols 10 in the seventh column and the seventh row with the upper left corner of the QR code as the origin. The QR code reader performs distortion correction and the like, extracts each module from the QR code, and decodes it according to a predetermined algorithm.

  Hereinafter, a color QR code in which a color is added to the background as in the present embodiment will be considered. In order to read the color QR code, when the color of the background portion and the QR code portion is grayed and binarized, the background portion has a contrast sufficient to distinguish it as bright and the QR code portion as dark. Need to be. According to a certain standard, it is sufficient that the contrast between light and dark is 60% or more and the whiteness of the background is 85%. If this contrast is maintained, a color may be added to the background as shown in FIGS. 4A to 4D described later, and a color is added to the QR code itself as shown in FIG. 4E. May be.

  In the color QR code according to the present embodiment, the background portion or the QR code itself includes a conditional color. The two colors having the same color relationship have a portion different from the portion where the spectral reflection spectra match. That is, it may appear the same color or a different color depending on the lighting conditions.

  FIG. 2 is a diagram showing an example of the spectral reflection spectrum of the color a and the color a ′, which have a relationship of the same color. The horizontal axis of the graph shown in FIG. 2 indicates the wavelength [nm], and the vertical axis indicates the spectral reflectance [%]. In this example, the color a and the color a ′ appear to be different colors in the wavelength region of about 520 to 625 nm, but appear to be the same color in other visible light regions. In this embodiment, the difference in spectral reflection spectrum is used for authenticity determination.

  FIGS. 3A to 3D are diagrams for explaining a method of creating conditional color matching. In the following description, cyan is C, magenta is M, yellow is Y, black is K, red is R, green is G, and blue is B. In each of FIGS. 3A to 3D, the left figure shows the color a, and the right figure shows the color a '.

  FIG. 3A shows an example in which the color a is printed in CMYK and the color a ′ is printed in CMYK (the dot ratio is different from the color a). That is, normal CMYK process printing is performed by changing the halftone dot ratio between the color a and the color a ', and the color of the condition is created. Spectral reflection if ink, paper, printing conditions (for example, filter characteristics of scanner, conversion from acquired RGB value to CMYK ratio of printing machine, halftone dot reproducibility) are different from real ones if it is just forgery by color copier Since there is a difference in the spectrum, authenticity can be determined.

  FIG. 3B shows an example in which the color a is printed with special color ink and the color a 'is printed with CMYK. In order to improve the fastness, it is effective to use not only CMYK ink but also spot color ink. For example, DIC Color Guide (registered trademark), which is a sample collection of special color inks from DIC Corporation, includes a DIC process color guide printed with a CMYK halftone dot ratio with the smallest color difference. In this way, when the color a is printed with the special color ink and the color a 'is printed with the CMYK halftone dot ratio of the color close to the special color ink, it is easy to create the condition color. Further, since the spectrum shape of the spot color ink has a characteristic that is not included in the spectrum shape of the CMYK ink, the authenticity determination is relatively easy.

  However, because special color ink was originally created for the purpose of reproducing colors that cannot be reproduced with CMYK ink, the color difference between the special color part (solid) and the CMYK part (halftone dot) is large, and anti-counterfeiting is applied. It is easy to understand. Further, when magnifying and observing with a magnifying glass or the like, it will be understood that different printing is performed in the special color portion and the CMYK portion.

  FIG. 3C shows an example in which the color a and the color a ′ are printed with the special color ink. That is, two colors having a small color difference and different spectrum shapes are used in the special color ink. However, since such combinations are limited only in DIC spot color inks, it is necessary to consider and select spot color inks manufactured by various companies when using a plurality of color conditions.

  FIG. 3D shows an example in which the color a is printed by replacing at least one of the CMYK inks with the special color ink, and the color a ′ is printed by the CMYK. If this method is used, both the color a and the color a 'are CMYK halftone prints even when viewed in an enlarged manner, and it is difficult to understand that anti-counterfeiting has been performed. In addition, since it is difficult to measure the spectral reflection spectrum of only dots, it is difficult to specify the spot color ink used, and the fastness is high.

  Note that it is also conceivable that the color “a” is CMYK ink and a special color ink is added to process printing with five colors, and the color “a ′” is CMYK printing. However, unless a special color ink similar in color to any one of CMYK is used, it can be seen that the color a 'includes dots of a color different from that of normal printing when viewed in an enlarged manner. Basically, a process printing machine performs four-color printing, and five-color printing is performed twice.

  Although not shown in the figure, a method using a special ink having a characteristic unique to a spectrum and having confidentiality in at least one of the color a and the color a ′ is conceivable. Since the spectrum has unique characteristics, it is easy to determine the authenticity and the fastness is very high. The reason why the special ink has high fastness is that it is difficult to obtain because it is not a common ink, and it is difficult to forge. However, it is expensive to produce a desired special ink.

  Table 1 below is a table in which the contents of the five methods described above are summarized in the order of low to high fastness. From these methods, the designer may select and use a method suitable for the application and cost. Even for existing spot color inks, counterfeiting is difficult unless it is specified what number of spot color inks of which company are used for printing. Even if it is specified, the spectrum changes depending on the paper and the printing press, so that it is relatively difficult to reproduce the spectrum shape. In the method shown in FIGS. 3B to 3D, specially produced special ink may be used instead of the special color ink.

  FIGS. 4A to 4E are diagrams for explaining a color arrangement example using conditional color in the color QR code. In each of FIGS. 4A to 4D, the lower figure shows the background in which the conditional color is arranged, and the upper figure is the color QR generated by overlapping the background shown in the lower figure and a predetermined QR code. The code is shown. In the color QR code area, at least one set of two areas each printed with two colors having the same color relationship is formed. The background and the two-dimensional code are colored with a contrast that can be read by a QR code reader (not shown).

  FIG. 4A shows an example in which the color a and the color a ′, which are in the condition of the same color as the background, are divided into two equal colors. In FIG. 4A, the left half of the background is colored with a color a, and the right half is colored with a color a '. It should be noted that, instead of being equally divided into vertical halves, it may be equally divided into horizontal halves, right diagonal halves, left diagonal halves, or may not be divided equally. For example, the left 2/3 of the background may be colored with the color a, and the right 1/3 may be colored with the color a '.

  FIG. 4B shows an example in which the background is basically colored with the color a, and the background includes a plurality of small areas colored with the color a ′. In FIG. 4B, small areas colored with a color a ′ are formed at two locations, the upper left and the lower center.

  FIG. 4C shows an example in which a plurality of sets of conditional colors are arranged on the background. In FIG. 4C, in addition to the combination of the color a and the color a ′, the combination of the color b and the color b ′ and the color c and the color c ′ is used. In FIG. 4C, the background is divided into a mosaic pattern, and each block is arranged in one of color a, color a ', color b, color b', color c and color c '.

  FIG. 4D shows another example in which a plurality of sets of conditional colors are arranged on the background. Also in FIG. 4D, in addition to the combination of the color a and the color a ′, the combination of the color b and the color b ′ and the color c and the color c ′ is used. In FIG. 4D, as compared with FIG. 4C, an arbitrary picture (here, a bear with a balloon) is drawn on the background. In FIG. 4D, colors other than color a, color a ', color b, color b', color c and color c 'are also used.

  FIG. 4E shows an example in which the QR code itself is formed using conditional color. In FIG. 4E, the QR code is printed with the color d and the color d 'having the same color relationship. More specifically, the entire area of the QR code is basically colored with the color d ', and a plurality of small areas colored with the color d are included in the area. In FIG. 4 (E), small areas that are colored in color d are formed at two locations, the upper left and the lower center. Although not shown, even when the QR code itself is formed using conditional color, a plurality of sets of conditional color may be arranged.

  The color QR codes in FIGS. 4A to 4E have a characteristic that it is difficult to counterfeit because it is difficult to understand at first glance that conditional colors are included. If the color a and the color a ′ having the same color relationship are adjacent to each other as shown in the lower diagram of FIG. 4A, it may be detected that the colors are slightly different. If the code is stacked, the camouflage effect makes it difficult to see the boundary. If the color a ′ is dispersed as shown in FIG. 4B, the color difference between the color a and the color a ′ can be made more difficult to feel.

  Further, by using a combination of a plurality of condition color equivalents as shown in FIG. 4C, it is possible to make it difficult to distinguish a place having a condition color match relationship. In addition, when a combination of a plurality of condition-like colors is used, it is necessary to reproduce a plurality of spectra when counterfeiting, thereby increasing the fastness. Further, as shown in FIG. 4D, design properties other than the pattern can be given to the background.

  The color QR code according to the embodiment of the present invention is printed on a predetermined print medium (for example, paper, fabric). Various information is coded and included in the color QR code. For example, a product code is included. The product code is a code (for example, a JAN barcode standardized by JIS-X-0501) indicating an article to which a QR code is attached. The JAN barcode includes a country code, a manufacturer code, and a merchandise item code. A lot number or an individual number may be used instead of the product code.

Further, as will be described later, the authentication of the color QR code according to the embodiment of the present invention may or may not pass through an authenticity determination server or an authenticity determination PC (hereinafter, an example using a server). . When passing through the authentication server, server address information (for example, URL (Uniform Resource Locator)) for accessing the authentication server must be included in the color QR code. Therefore, when passing through the authentication server, the color QR code includes, for example, the following information.
“Product No.20546879 manufactured by Japan XX Company http // www .... (authentication server URL)”

On the other hand, when not passing through the authenticity determination server, it is necessary to determine the authenticity using only the information included in the color QR code. Therefore, if the color QR code does not include the position information (for example, defined by XY coordinates) printed in the same color and indicating the area to be compared and the true value of the color information in the comparison area. Don't be. In the embodiment of the present invention, the color information and the L ^* a ^* b ^* true value of the printed area with the color a in the relation of metamerism, the printed color a 'Area L ^* a ^* b ^* Specified by the true value and the true value of the color difference between the color a and the color a ′. Further, it is desirable that the true values of the position information and the color information are encrypted and decrypted by the QR code reader. Based on the above, when not passing through the authentication server, the color QR code includes, for example, the following information.
“Product No. 20546879, manufactured by Japan XX Corporation, comparison area position, L ^* a ^* b ^* true value, true value of area color difference”

  Hereinafter, the authenticity determination method according to the embodiment of the present invention will be outlined. In the present embodiment, the above-described color QR code is imaged under a white light source by an image sensor (for example, a charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS)). Is grayed out and binarized according to the brightness, and the content contained in the code is read from the luminance information by an existing QR code reading application, and at the same time, 6-band color information for each pixel Is acquired, and the acquired color information is compared with the true color information of the read QR code, and authenticity determination is performed.

  Although it is conceivable to use a spectroscope (measurement is possible every 2 nm) for acquiring color information, the spectroscope is fine in wavelength step and highly accurate, but is expensive and increases the amount of data. Therefore, it is not very suitable for acquiring a spectral image with an inexpensive apparatus. Further, it is conceivable to use a hyperspectral camera (measurable every 2 to 10 nm) or a multiband spectrum camera (measurable every 10 to 100 nm). These are now often used to acquire spectral images. However, if a liquid crystal tunable filter is used or if the number of filters is large, it will be expensive.

  Therefore, a method for estimating the spectral reflection spectrum using the measurement results of several bands has been proposed, and in this embodiment, authenticity determination is performed using this method. In the following, an example in which a spectral reflection spectrum is estimated from the measured values of the RR′BB′GG′6 band, assuming a relatively inexpensive and simple authentication system will be described.

  FIG. 5 is a diagram illustrating an example of spectral sensitivity characteristics of a color filter attached to the image sensor. The horizontal axis of the graph shown in FIG. 5 indicates wavelength [nm], and the vertical axis indicates transmittance [%]. Many image sensors used in general digital cameras are equipped with three primary color filters (RGB filters) arranged in a Bayer array. The image sensor outputs RGB three-band pixel signals. In this embodiment, two types of three primary color filters having different spectral sensitivity characteristics are used in order to acquire 6-band pixel signals. That is, an R′G′B ′ filter in which the wavelength band of the RGB filter is shifted to the short wavelength side is used.

  As shown in FIG. 5, the R′G′B ′ filter has a spectral sensitivity characteristic that interpolates the dead band of the RGB filter. An RGB filter is attached to the image sensor to obtain RGB 3-band pixel signals, and then an R′G′B ′ filter is attached to obtain R′G′B′-band pixel signals. Thereby, a total of 6-band pixel signals can be acquired. Each filter of RR′BB′GG ′ may be fixedly attached to the image sensor. In this case, 6-band pixel signals can be acquired by one shooting, but the resolution decreases.

Example 1
FIG. 6 is a diagram illustrating a configuration of the authenticity determination system 300 according to the first embodiment. The first embodiment corresponds to the case where there is an authentication determination server as described above. As described above, the color QR code is an identification code that is color-printed on the print medium using the condition color. When passing through the authentication server, management information such as a product code and an address or identifier (for example, URL) for accessing the authentication device 200 are encoded in the color QR code.

  The authenticity determination system 300 includes an imaging device 100 and an authenticity determination device 200. The imaging device 100 and the authenticity determination device 200 are configured to be able to communicate via a predetermined network (for example, the Internet).

  The imaging device 100 corresponds to the QR code reading device described above. More specifically, a mobile phone with a camera function, a smartphone with a camera function, a digital camera with a communication function, a dedicated device with a communication function, and the like are applicable. The authenticity determination device 200 corresponds to the authenticity determination server described above. When the mobile phone and the smartphone are employed as the imaging device 100, the base station can be accessed by wireless communication via the mobile phone network, and data can be exchanged with the authenticity determination device 200. Further, when the imaging apparatus 100 is equipped with a wireless LAN function, the access point can be accessed by wireless communication, and data can be exchanged with the authenticity determination apparatus 200.

  The imaging apparatus 100 includes an image reading unit 110, a control unit 120, a communication unit 130, and a display unit 140, and is an apparatus for imaging a printed color QR code. The image reading unit 110 includes an image sensor 111, an image processing unit 112, and an identification code reading unit 113.

  The image sensor 111 captures a color QR code. An RGB filter and an R′G′B ′ filter as shown in FIG. 5 are mounted on the incident surface side of the image sensor 111 and imaged twice, thereby obtaining a 6-band image. Note that the imaging apparatus 100 is preferably provided with a white light source to be illuminated and configured to block external light. It is desirable that the user shoots so that the object to be measured is uniformly illuminated during shooting so that the regular reflection component of the light source does not enter the lens.

  The image processing unit 112 performs image processing such as binarization, rotation, movement, and enlargement / reduction of the color QR code image captured by the image sensor 111 and supplies the processed image to the identification code reading unit 113. The identification code reading unit 113 detects the product code and the URL from the image processed by the image sensor 111. The 6-band image captured by the image sensor 111 and the product code and URL detected by the identification code reader 113 are supplied to the controller 120. Note that the 6-band image supplied to the control unit 120 is preferably subjected to image processing such as rotation, movement, and enlargement / reduction by the image processing unit 112.

  The control unit 120 controls the entire imaging apparatus 100 in an integrated manner. The communication unit 130 accesses the authenticity determination device 200 via the network using the URL read by the identification code reading unit 113, and transmits the product code and the 6-band image to the authenticity determination device 200. Further, the authenticity determination result determined by the authenticity determination device 200 is received. The display unit 140 displays the authentication result received from the authentication device 200.

  The authenticity determination device 200 includes a communication unit 210, a display unit 220, a control unit 230, and a storage unit 240, and is a device for determining the authenticity of the color QR code imaged by the imaging device 100. As a result of authenticity determination, if it is determined to be authentic, it can be considered that the color QR code has been authenticated as valid. Therefore, the authenticity determination device 200 can be considered as an authentication device.

  The communication unit 210 receives a product code and a 6-band image from the imaging apparatus 100. Further, the authenticity determination result is transmitted to the imaging apparatus 100 by a method described later. The display unit 220 displays predetermined information. In the present embodiment, the authentication process and the authentication result are displayed.

  The control unit 230 comprehensively controls the authenticity determination device 200 as a whole. More specifically, the control unit 230 includes a comparison area acquisition unit 231, an area pixel value calculation unit 232, a spectral spectrum estimation unit 233, a difference spectrum calculation unit 234, a correlation coefficient & RMS calculation unit 235, and an authenticity determination unit 236. .

  These configurations can be realized by an arbitrary processor, memory, or other LSI in terms of hardware, and can be realized by a program loaded in the memory in terms of software, but here by their cooperation. Draw functional blocks. Therefore, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  The storage unit 240 includes a measurement spectrum characteristic holding unit 241, a light source spectral characteristic holding unit 242, a camera spectral sensitivity characteristic holding unit 243, a learning spectrum characteristic holding unit 244, a comparison area holding unit 245, and a difference spectrum true value holding unit 246.

  The measurement spectral characteristic holding unit 241 temporarily holds a 6-band image measured by the imaging apparatus 100. The light source spectral characteristic holding unit 242, the camera spectral sensitivity characteristic holding unit 243, and the learning spectral characteristic holding unit 244 hold characteristic information necessary for spectral reflectance spectrum estimation. Specific examples of these characteristic information will be described later.

  The comparison area holding unit 245 holds, for each product code, position information of the first area and the second area in which two colors having the same color relationship are printed. The difference spectrum true value holding unit 246 holds the true value of the difference spectrum between the spectral reflection spectrum of the color of the first area and the spectral reflection spectrum of the color of the second area.

  The comparison area acquisition unit 231 acquires the first area and the second area corresponding to the product code received by the communication unit 210 from the comparison area holding unit 245. The area pixel value calculation unit 232 calculates, for each band, the average pixel values of the first area and the second area acquired by the comparison area acquisition unit 231 from each of the 6-band images received by the communication unit 210.

  The spectral spectrum estimation unit 233 uses the average pixel value for each band of the first area calculated by the area pixel value calculation unit 232 and the learning data of the first area held in the learning spectrum characteristic holding unit 244, and Estimate the spectral reflection spectrum of one area. Similarly, using the average pixel value for each band of the second area calculated by the area pixel value calculation unit 232 and the learning data of the second area held in the learning spectrum characteristic holding unit 244, the spectrum of the second area is used. Estimate the reflection spectrum. A method for estimating the spectral reflection spectrum will be described later.

  The difference spectrum calculation unit 234 calculates a difference spectrum between the spectral reflection spectrum of the first area estimated by the spectral spectrum estimation unit 233 and the spectral reflection spectrum of the second area. The correlation coefficient & RMS calculation unit 235 calculates a correlation coefficient R and a mean square deviation RMS between the measured value of the difference spectrum and the true value of the difference spectrum held in the difference spectrum true value holding unit 246.

  The authenticity determination unit 236 determines the authenticity of the color QR code using the spectral reflection spectrum of the first area and the spectral reflection spectrum of the second area estimated by the spectral spectrum estimation unit 233. In this embodiment, the authenticity determination unit 236 determines the authenticity of the color QR code based on the correlation coefficient R calculated by the correlation coefficient & RMS calculation unit 235 and the mean square deviation RMS. More specifically, when the correlation coefficient R is larger than a predetermined first set value and the mean square deviation RMS is smaller than a predetermined second set value, it is determined to be genuine, and this condition is not satisfied Judged as fake.

  FIG. 7 is a flowchart for explaining an operation example of the authenticity determination system 300 according to the first embodiment. First, the imaging device 111 of the imaging apparatus 100 captures the color QR code and acquires a 6-band image formed by 6-band pixel values (RR′GG′BB ′ pixel value in this embodiment). (S10). The identification code reading unit 113 detects the product code and the URL from the captured QR code image (S12). The communication unit 130 accesses the authenticity determination device 200 using the URL, and transfers the product code and the 6-band image (S14).

  The comparison area acquisition unit 231 of the authenticity determination device 200 reads out the color comparison area corresponding to the product code transferred from the imaging device 100 from the comparison area holding unit 245 (S16). In the two color comparison areas forming the set, the color a and the color a ′ having the same color relationship are arranged.

  The area pixel value calculation unit 232 trims the area of color a and the area of color a ′. Then, averaging of the RR′GG′BB ′ value is calculated for each of the trimmed areas (S18). Therefore, six values to be the basis of spectral reflection spectrum estimation are generated for each area.

  FIG. 8 is a diagram for explaining the color comparison area and trimming. In FIG. 8, an area a in which a color a having a conditional color relationship is arranged and an area a ′ in which a color a ′ is arranged are formed in a square region 30 where a QR code is formed. When comparing the colors of area a and area a ′, color mixing due to printing misalignment or ink bleeding is likely to occur at each area boundary, and therefore a range several pixels inside the area boundary (the shaded area in FIG. 8). Then, the average value of the pixel values is calculated for each band. Note that a median value may be used instead of the average value.

  Returning to FIG. 7, the spectral spectrum estimation unit 233 estimates the spectral reflection spectrum of each area using the RR′GG′BB ′ average value calculated in step S <b> 18 (S <b> 20). More specifically, the process of measuring the measured spectral reflection spectrum with the sensitivity of each channel of the camera (corresponding to the above band) is modeled as a linear matrix calculation, formulated as an inverse matrix problem, and the unknown Estimate the spectral reflectance spectrum. The actually measured spectral reflection spectrum is a spectrum obtained by multiplying a plurality of known spectral reflection spectra held in the learning spectrum characteristic holding unit 244 and the light source spectral characteristics held in the light source spectrum characteristic holding unit 242. . The sensitivity of each channel of the camera is held in the camera spectral sensitivity characteristic holding unit 243. As the estimation method, winner estimation, multiple regression analysis, Markov estimation, principal component analysis, or the like can be used. In this specification, an example using the winner estimation will be described later.

  The difference spectrum calculation unit 234 calculates a difference spectrum between the spectral reflectance spectrum of the area a estimated by the spectral spectrum estimation unit 233 and the spectral reflectance spectrum of the area a ′ (S22).

  9A to 9C are diagrams showing the relationship between the measured value of the difference spectrum calculated by the difference spectrum calculation unit 234 and the true value of the difference spectrum held in the difference spectrum true value holding unit 246. is there. FIG. 9A shows the spectral reflection spectrum of area a, and FIG. 9B shows the spectral reflection spectrum of area a ′. FIG. 9C shows the measured value of the difference vector between the spectral reflection spectrum of area a and the spectral reflection spectrum of area a ′ and the true value of the differential spectrum held in the differential spectrum true value holding unit 246 in the same graph. It is drawn in.

  Returning to FIG. 7, the correlation coefficient & RMS calculation unit 235 calculates the correlation coefficient R and the mean square deviation RMS between the measured value and the true value of the difference spectrum (S24).

  The correlation coefficient R is calculated by the following (formula 1), and the mean square deviation RMS is calculated by the following (formula 2).

Here, xi is a value indicating the differential reflectance at the wavelength i of the differential spectrum measurement value x. yi is a value indicating the differential reflectance at the wavelength i of the differential spectrum true value y.

  If the correlation coefficient R is larger than the first set value and the mean square deviation RMS is smaller than the second set value (Y in S26), the authenticity determination unit 236 determines that the color QR code is genuine ( When the condition is not satisfied (N in S26), it is determined as a fake (S30). The flowchart of FIG. 7 shows an example in which the first set value is 0.98 and the second set value is 0.05, but these set values are not limited to these values. The designer can reduce or optimize the genuine rejection rate and the fake acceptance rate by adjusting these set values based on experiments and simulations. If it is desired to simplify the system, it is also conceivable to make an authenticity determination using only the correlation coefficient R.

  The communication unit 210 returns the authentication result of the authentication device 200 to the imaging device 100 (S32). The display unit 140 of the imaging apparatus 100 displays the authentication result (S34).

(Example 2)
Next, Example 2 will be described. The second embodiment corresponds to the case where the above-described authentication server is not passed. In the second embodiment, it is conceivable to incorporate the function of the authenticity determination device 200 into the imaging device 100 in the first embodiment as it is. However, since the imaging device must hold a color comparison area corresponding to the product code and a database storing the color information, it is difficult to reduce the size and weight of the device unless the number of data is small.

Therefore, if authentication can be performed only with information included in the color QR code, authentication can be performed on a stand-alone basis even with a relatively small, light, and inexpensive device. In this case, the color QR code itself needs to include the position of the color comparison area and the true value of the color information. The color information is the true value of the difference spectrum between the color comparison areas in the first embodiment, but the data amount is too large to include it in the color QR code. In the second embodiment, L ^* a ^* b ^{* of} each color comparison area and color difference ΔE ^* ab between color comparison areas are used instead of the difference spectrum information. Further, the position information of the color comparison area and the true value of the color information (that is, the true value of L ^* a ^* b ^* of each color comparison area and the true value of the color difference of the color comparison area) are encrypted, and an authenticity determination device to be described later It is desirable to have a configuration in which only 400 can be decoded.

  FIG. 10 is a diagram illustrating a configuration of the authenticity determination device 400 according to the second embodiment. The authenticity determination device 400 includes an image reading unit 410, a control unit 420, a storage unit 430, and a display unit 440. The image reading unit 410 includes an image sensor 411, an image processing unit 412, and an identification code reading unit 413. The configuration of the image reading unit 410 according to the second embodiment is basically the same as that of the image reading unit 110 according to the first embodiment. Hereinafter, differences will be described.

The identification code reading unit 413 reads the product code, the position information of the first area and the second area to be the color comparison area, and the L ^* a ^* b ^{* of} the first area from the image processed by the image sensor 411 ^. , The true value of L ^* a ^* b ^* in the second area, and the true value of the color difference between the first area and the second area are detected. 6-band image captured by the image sensor 411, product code detected by the identification code reader 413, position information of the first area and the second area, the true value of L ^* a ^* b ^* of the first area, The true value of L ^* a ^* b ^* in the second area and the true value of the color difference between the first area and the second area are supplied to the control unit 420.

  The control unit 420 includes a comparison area acquisition unit 421, area pixel value calculation unit 422, spectral spectrum estimation unit 423, L * a * b * calculation unit 424, color difference calculation unit 425, and authenticity determination unit 426. These configurations can be realized by an arbitrary processor, memory, or other LSI in terms of hardware, and can be realized by a program loaded in the memory in terms of software, but here by their cooperation. Draw functional blocks. Therefore, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  The storage unit 430 includes a measurement spectral characteristic holding unit 431, a light source spectral characteristic holding unit 432, a camera spectral sensitivity characteristic holding unit 433, and a learning spectral characteristic holding unit 434. Since these are the same as the measurement spectral characteristic holding unit 241, the light source spectral characteristic holding unit 242, the camera spectral sensitivity characteristic holding unit 243, and the learning spectral characteristic holding unit 244 of the first embodiment, description thereof will be omitted.

  The comparison area acquisition unit 421 acquires the first area and the second area detected by the identification code reading unit 413. The area pixel value calculation unit 422 calculates, for each band, the average pixel value of the first area and the second area acquired by the comparison area acquisition unit 421 from each of the 6 band images read by the image reading unit 410. .

  The spectral spectrum estimation unit 423 uses the average pixel value for each band of the first area calculated by the area pixel value calculation unit 422 and the learning data of the first area held in the learning spectrum characteristic holding unit 434. Estimate the spectral reflection spectrum of one area. Similarly, using the average pixel value for each band of the second area calculated by the area pixel value calculation unit 422 and the learning data of the second area held in the learning spectrum characteristic holding unit 434, the spectrum of the second area is used. Estimate the reflection spectrum.

  The L * a * b * calculation unit 424 calculates the value of L * a * b * of the first area from the spectral reflection spectrum of the first area estimated by the spectral spectrum estimation unit 423. Similarly, the value of L * a * b * of the second area is calculated from the spectral reflection spectrum of the second area estimated by the spectral spectrum estimation unit 423.

  The color difference calculation unit 425 calculates the difference between the L * a * b * value of the first area and the L * a * b * value of the second area, which is calculated by the L * a * b * calculation unit 424. To do. In this embodiment, both ΔE * ab values are used as the color difference between them. A method of calculating these L * a * b * values and ΔE * ab values will be described later.

  The authenticity determination unit 426 calculates the true value of the color of the first area detected by the identification code reading unit 413 and the measured value of the color calculated from the spectral reflection spectrum of the first area estimated by the spectral spectrum estimation unit 423. Comparison, comparison between the true value of the color of the second area detected by the identification code reading unit 413 and the measurement value of the color calculated from the spectral reflection spectrum of the second area estimated by the spectral spectrum estimation unit 423, and identification Based on the comparison between the true value of the color difference detected by the code reading unit 413 and the true value of the color difference between the first area and the second area calculated by the spectral spectrum estimation unit 423, the authenticity of the color QR code is determined. To do. A specific example of this determination process will be described later. The display unit 440 displays the authenticity determination result determined by the authenticity determination unit 426.

  FIG. 11 is a flowchart for explaining an operation example of the authenticity determination apparatus 400 according to the second embodiment. First, the image sensor 411 of the image reading unit 410 captures the color QR code, and generates a 6-band image formed by 6-band pixel values (RR′GG′BB ′ pixel value in this embodiment). Obtain (S40). The identification code reading unit 413 detects the product code, the color comparison area position, the true value of L * a * b * in each color comparison area, and the true value of the color difference between the color comparison areas from the captured QR code image ( S42).

  The comparison area acquisition unit 421 specifies the color comparison area detected by the identification code reading unit 413, and the area pixel value calculation unit 422 averages the RR'GG'BB 'values of the respective color comparison areas (S44). As in the first embodiment, the area pixel value calculation unit 422 may trim the color comparison area and then average the RR′GG′BB ′ values of the trimmed area (see FIG. 8).

  The spectral spectrum estimation unit 423 estimates the spectral reflection spectrum of each color comparison area using the RR'GG'BB 'average value calculated by the area pixel value calculation unit 422 (S44). An example using Wiener estimation as described above in the first embodiment will be described later.

The L * a * b * calculation unit 424 calculates the L * a * of the color comparison area from the value of the spectral reflection spectrum of the color comparison area estimated by the spectral spectrum estimation unit 423 (hereinafter referred to as a measured value of the color comparison area). The value of b * is calculated (S46). Hereinafter, a method for calculating L * a * b * will be described in detail. As a prerequisite, Reflectance (lambda) an estimate of a color comparison area, light source D ₆₅ standard light source, CIE a Toiro function is human spectral sensitivity (1964) and _{X 10 Y 10 Z 10 Color Matching} Function. Under this precondition, tristimulus values XYZ are calculated from the following (Equation 3).

  L * a * b * is calculated from the tristimulus value XYZ value calculated by the above (formula 3) by the following (formula 4).

Under the D ₆₅ standard light source, X _n = 95.045, Y _n = 100, Z _n = 108.892 are used.

  The color difference calculation unit 425 compares ΔE * in order to compare the measured value of L * a * b * with the true value of L * a * b * detected from the color QR code by the identification code reading unit 413. ab is calculated (S48). The color difference calculation unit 425 calculates ΔE * ab by the following (formula 5).

ΔL *, Δa *, Δb * are measured values of L *, a *, b * calculated from measured values of the color comparison area, and L *, detected from the color QR code by the identification code reading unit 413. Each difference with the true value of a * and b * is shown.

  The authenticity determination unit 426 compares the measured value of the color comparison area with the true value of the color comparison area for each color comparison area. It is determined whether or not the difference between the measured value and the true value is small (S50). For example, if ΔE * ab is smaller than a predetermined third set value (10 in this embodiment) (Y in S50), it is determined that the possibility of authenticity is high. On the other hand, if ΔE * ab is greater than or equal to the third set value in at least one of the color comparison areas (N in S50), at least one color in the color comparison area read from the color QR code is a real color. The authenticity determination unit 426 determines that the color QR code is a fake (S58).

  As a result of the determination in step S50, if the possibility of authenticity is high, the color difference calculation unit 425 calculates ΔE * ab between the color comparison areas (between the first area and the second area described above) (S52). The authenticity determination unit 426 compares ΔE * ab calculated by the color difference calculation unit 425 with ΔE * ab detected from the color QR code by the identification code reading unit 413 (S54). If the two substantially match (Y in S54), the authenticity determination unit 426 determines that the color QR code is genuine (S56). On the other hand, if the two do not substantially match (N in S54), the authenticity determination unit 426 determines that the color QR code is a fake (S58).

  If the authenticity is determined only by the color difference between the color comparison areas, there is a possibility that the color difference becomes the same value even if it is a completely different combination of colors (for example, yellow and green conditions and the like). Therefore, in step S50, it is confirmed using the value of L * a * b * that the color in each color comparison area is close to each true value color.

  The display unit 440 displays the authenticity determination result by the authenticity determination unit 426 (S60). The designer can reduce or optimize the genuine rejection rate and the fake acceptance rate by adjusting the third set value and the range of coincidence based on experiments and simulations.

  Here, a method of estimating the spectral reflection spectrum from the multiband image using the Wiener estimation method by the spectral spectrum estimation unit 233 according to the first embodiment and the spectral spectrum estimation unit 423 according to the second embodiment will be described.

When an object (a color QR code in this embodiment) is imaged through a multiband broadband filter with a camera, the spectrum of light incident on an image sensor (for example, a CCD element) corresponding to the coordinates (x, y) of the image The distribution is given by t (λ) E (λ) r (x, y; λ). Here, t (λ) is the spectral transmittance of the i-th filter, E (λ) is the spectral radiance of illumination, and r (x, y; λ) is the image coordinates (ie, pixel position) (x , Y) shows the spectral reflectance of the object. Also, S (λ) is the total spectral performance that combines the spectral transmittance of the lens and the spectral sensitivity of the image sensor. At this time, the sensor response v _i (x, y) obtained in each element is obtained by integrating the incident light t (λ) E (λ) r (x, y; λ) and the spectral S (λ) in the wavelength region. Therefore, it is expressed by the following (formula 6).

Here, m represents the number of multiband bands. The spectral product S (λ) was assumed to be zero outside the visible light range of wavelength 400 to 700 nm.

Next, in order to simplify mathematical handling, the spectral distribution is discretized and expressed using vectors and matrices. When v is represented by a row vector having m elements representing sensor responses of m bands, and r is represented by a row vector composed of l elements representing the spectral reflectance of the object, the above (formula 6) is It is expressed using a vector matrix as shown below (Formula 7).

Here, the coordinates (x, y) of the image are omitted. The matrix F is a matrix T (see (Equation 8) below) in which row vectors t representing the spectral transmittance of the i-th filter are combined, and an l × l diagonal matrix corresponding to the spectral sensitivity of the illumination and the camera. Using the matrices E and S, it is defined as (Equation 9) below.

  The Wiener estimation is a method for minimizing the mean square error E between the spectral reflectance r of the plurality of learning data samples and the estimated spectral reflectance (r tilde). expressed.

<> Represents an ensemble average for a spectral reflectance sample.

Considering the following (Equation 11), an estimation matrix G for estimating the spectral reflectance (r tilde) from the sensor response vector is considered.

At this time, an estimation matrix that minimizes the mean square error E expressed by the above (formula 10) is given by the following (formula 12).
Here, R _rv (see (Expression 13) below) represents a cross-correlation matrix of spectral reflectances r and v regarding the sample, and R _vv (see (Expression 14) below) represents an autocorrelation matrix of v. R _rr (see (Expression 15) below) represents an autocorrelation matrix of r.

Therefore, the above (formula 12) can be rewritten as the following (formula 16).

Further, when the noise n is included in the sensor response, the above (Expression 7) becomes the following (Expression 17).

The autocorrelation matrix R _nn of noise n is expressed as (Equation 18) below.

Thus, the Wiener estimation gives an estimation matrix that minimizes the mean square error of the estimated value by a simple linear operation when the statistics of the signal and noise are known. Here, if the input spectrum and the noise spectrum are uncorrelated, an estimation matrix that minimizes the mean square error is given by (Equation 19) below.

As a result, when the estimation matrix G is obtained, the spectral reflectance of the object at the coordinates (x, y) of the image obtained by multiband imaging of the measurement object is set as v, and the estimated spectral reflectance (r tilde) from the above equation (11). ). For example, when v is an RR′GG′BB ′ value (6 bands) and spectral reflectance data is obtained every 2 nm from 400 nm to 700 nm, it is expressed as (Equation 20) below.

  As described above, according to the present embodiment, a condition-colored portion is added to the color two-dimensional code, so that it is inexpensive but relatively robust (that is, has a relatively high anti-counterfeit effect) and An authentication system can be created. For example, a color such as a condition ink produced using process ink, special color ink or special ink is put in the QR code, and the content of the QR code is authentication server address or information necessary for authentication (for example, comparison area position information, condition Color information of the same color). Accordingly, it is possible to easily determine the authenticity of the image picked up by the image pickup element without requiring a device such as a spectroscope. In addition, by performing authentication in the visible light region, it is possible to perform authentication in the imaging wavelength range of a general camera image sensor (CCD image sensor or CMOS image sensor) without using a special measuring instrument, and an inexpensive system. Can be built. Thus, the cost of the system can be reduced by performing authenticity determination using the condition color in the visible light region.

  In addition, since the anti-counterfeiting measures so far cannot be immediately invalidated even if forgery is detected, it has been difficult to prevent the spread of damage caused by counterfeit products already on the market. On the other hand, according to the authenticity determination system according to the first embodiment, by authenticating through the authenticity determination server, the counterfeit distribution information can be grasped at an early stage, and a quick response when a counterfeit is detected becomes possible. That is, if the system is monitored, it is possible to immediately and efficiently take measures such as collecting discovery information of counterfeit products and invalidating the code when a counterfeit is detected.

  Further, according to the authenticity determination system according to the first embodiment, the position information and color information of the color comparison area are stored on the authenticity determination server side. Therefore, the contents of the QR code need only be the product code and the authentication server address, and the amount of information can be reduced. On the other hand, the reader side does not need an arithmetic function for authenticity determination, and only needs to be able to capture an image. Therefore, although it is necessary to consider illumination and external light, it can be incorporated into a small and lightweight portable device such as a mobile phone or a smartphone. However, the environment must be able to connect to the network.

  On the other hand, the authenticity determination device according to the second embodiment can determine the authenticity standalone without being connected to a network. However, the amount of information included in the QR code increases. In addition, hardware with specifications that allow calculation for authenticity determination must be installed. Therefore, there is a high possibility that it will be larger at a higher cost than the reading apparatus according to the first embodiment. Thus, both have advantages and disadvantages, and may be appropriately selected according to needs.

  The present invention has been described based on some embodiments. It is understood by those skilled in the art that these embodiments are exemplifications, and that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. By the way.

  In the first and second embodiments, the case where the condition color is one set has been described, but a plurality of sets may be used. In that case, if it is determined that all groups are genuine, the color two-dimensional code is determined to be genuine. In addition, when there are a large number of sets of color of the same condition, the color two-dimensional code may be determined to be genuine when a predetermined authentication rate (for example, 80%, 90%, 95% or more, etc.) is exceeded. Further, as the authenticity determination method by the authenticity determination server according to the first embodiment, the difference between the spectral reflectance spectra is not calculated, but the color difference ΔE * ab between the two colors having the same color relationship described in the second embodiment is determined. A method may be adopted. Conversely, if the authenticity determination device according to the second embodiment is a high-spec device, the method for determining the difference in the spectral reflectance spectrum described in the first embodiment may be employed as the authenticity determination method. The display unit 140 may be provided outside the imaging device 100 in the first embodiment, and the display unit 440 may be provided outside the authenticity determination device 400 in the second embodiment.

  In the first and second embodiments, the authenticity determination may be performed directly from the six values of RR′GG′BB ′ without estimating the spectral reflection spectrum. The difference between the measured value of RR'GG'BB 'in the first area and the true value of RR'GG'BB' in the first area, and the measured value of RR'GG'BB 'in the second area and the above If at least one of the differences from the true value of RR′GG′BB ′ in the second area is equal to or greater than a predetermined fourth set value, it is determined to be a fake. If both of these differences are smaller than the fourth set value, the difference between the measured value of RR'GG'BB 'in the first area and the measured value of RR'GG'BB' in the second area, If the true value of the difference between RR′GG′BB ′ of one area and the RR′GG′BB ′ of the second area substantially matches, it is determined to be genuine, and if it does not approximately match, it is determined to be fake. This method does not have high authentication accuracy, but can greatly reduce the amount of calculation. Therefore, it is suitable for simple authentication.

  In addition, in the case of a printed matter having characteristics peculiar to a certain wavelength, a filter and a determination method may be optimized so as to compare by paying attention to the specific wavelength. The adjustment of the number of bands and the band wavelength range is an example, but is not limited to these adjustments. In the first and second embodiments, an example in which six bands are detected has been described. However, by increasing the number of bands, it is possible to further improve the accuracy of spectral shape reproduction.

  In addition, although the QR code is given as an example of the identification code that should be the object of authenticity determination, the present invention is not limited to this. For example, if the amount of information to be included in the identification code can be compressed, a one-dimensional code such as a barcode can be adopted. In addition, it is desirable to use light-resistant ink in order to prevent deterioration of the printed matter on which the identification code is printed. Further, the surface of the printed material may be coated with UV-cutting property, water resistance, solvent resistance, low oxygen transmission rate, low water vapor transmission rate and the like.

  DESCRIPTION OF SYMBOLS 100 Imaging device, 111 Image sensor, 113 Identification code reading part, 130 Communication part, 200 Authentication determination apparatus, 210 Communication part, 231 Comparison area acquisition part, 232 Area pixel value calculation part, 233 Spectral spectrum estimation part, 236 Authentication determination part 245 comparison area holding unit, 300 authenticity determination system, 400 authenticity determination device, 411 imaging device, 413 identification code reading unit, 421 comparison area acquisition unit, 422 area pixel value calculation unit, 423 spectral spectrum estimation unit, 424 L * a * b * calculation unit, 426 authenticity determination unit.

Claims (7)

A step of obtaining a multiband image by imaging an identification code in which predetermined information is coded and an identification code to be color-printed on a print medium using a conditional color, by an imaging device;
Obtaining, from each of the multiband images, the pixel values of the first area and the second area in which the two colors having the same color relationship are to be printed, for each band;
The spectral reflectance spectrum of the first area is estimated using the color learning data of the first area and the pixel value for each band of the first area, and the color learning data of the second area and the second area Estimating a spectral reflection spectrum of the second area using pixel values for each of the bands;
Determining the authenticity of the identification code using the spectral reflectance spectrum of the first area and the spectral reflectance spectrum of the second area;
A method for determining authenticity, comprising: A step of obtaining a multiband image by imaging an identification code in which predetermined information is coded and an identification code to be color-printed on a print medium using a conditional color, by an imaging device;
Obtaining, from each of the multiband images, pixel values of a first area and a second area in which two colors having the same color relationship are to be printed;
Determining the authenticity of the identification code using the multiband pixel values of the first area and the multiband pixel values of the second area;
A method for determining authenticity, comprising: The imaging device has two types of three primary color filters having different spectral sensitivity characteristics,
The authenticity determination method according to claim 1 or 2, wherein the step of acquiring the multiband image acquires a 6-band image from the imaging device. An authentication system comprising: an imaging device for imaging an identification code encoded with predetermined management information; and an authenticity determination device for determining the authenticity of the identification code imaged by the imaging device,
The identification code is an identification code to be color-printed on a print medium using a conditional color, and an identifier for accessing the authenticity determination device is further encoded.
The imaging device
An image sensor for capturing a multiband image of the identification code;
An identification code reading unit for detecting the management information and the identifier from the multiband image captured by the image sensor;
A first communication unit that accesses the authentication device using the identifier via a network and transmits the management information and the multiband image to the authentication device;
The authenticity determination device includes:
A second communication unit that receives the management information and the multiband image from the imaging device;
For each management information, a comparison area holding unit that holds a first area and a second area in which two colors having the same color relationship are printed,
A comparison area acquisition unit for acquiring the first area and the second area from the comparison area holding unit corresponding to the management information received by the second communication unit;
An area pixel value specifying unit that specifies, for each band, pixel values of the first area and the second area acquired by the comparison area acquiring unit from each of the multiband images received by the second communication unit;
A spectral reflectance spectrum of the first area is estimated using the pixel value for each band of the specified first area and the learning data for the color of the first area, and the pixel value for each band of the specified second area is A spectral spectrum estimation unit that estimates the spectral reflection spectrum of the second area using the learning data of the color of the second area;
An authenticity determination unit that determines the authenticity of the identification code using the spectral reflection spectrum of the first area and the spectral reflection spectrum of the second area estimated by the spectral spectrum estimation unit;
An authentication system characterized by comprising: The identification code to be color-printed on the print medium using the condition color, and the positions of the first area and the second area where the predetermined management information and the two colors having the condition color are to be printed respectively Imaging for capturing a multiband image of an identification code in which information, the true value of each color of the first area and the second area, and the true value of the color difference between the first area and the second area are coded Elements,
An identification code reading unit that detects the position information, the true value of the color, and the true value of the color difference from an image captured by the image sensor;
An area pixel value specifying unit for specifying the pixel values of the first area and the second area for each band from each of the multiband images;
A spectral reflectance spectrum of the first area is estimated using the pixel value for each band of the specified first area and the learning data for the color of the first area, and the pixel value for each band of the specified second area is A spectral spectrum estimation unit that estimates the spectral reflection spectrum of the second area using the learning data of the color of the second area;
A first comparison between a true value of the color of the first area detected by the identification code reading unit and a color measurement value calculated from the spectral reflection spectrum of the first area estimated by the spectral spectrum estimation unit; A second comparison between the true value of the color of the second area detected by the code reading unit and the measured value of the color calculated from the spectral reflectance spectrum of the second area estimated by the spectral spectrum estimation unit, and the identification code Based on a third comparison between the true value of the color difference detected by the reading unit and the measured value of the color difference between the first area and the second area based on the measured value estimated by the spectral spectrum estimating unit, An authenticity determination unit for determining authenticity;
An authenticity determination device comprising: 6. The authenticity determination device according to claim 5, wherein the color and the color difference are defined by an L ^* a ^* b ^* display system. A color two-dimensional code in which predetermined information printed on a print medium is encoded,
A color two-dimensional code characterized in that two regions each printed with two colors having the same color relationship are formed in the two-dimensional code region.