JP6979694B2 - Authentication system, authentication method and authentication program that authenticates hidden images or hidden information - Google Patents

Description

The present invention relates to an authentication system, an authentication method, and an authentication program for authenticating a hidden image or hidden information by collating the information extracted from the hidden image or hidden information printed on the printed matter with the genuine information.

In recent years, valuable printed materials such as banknotes, securities and toll tickets, and certificates that authenticate individuals such as driver's licenses, passports and insurance certificates have always been newly prevented from being forged or tampered with by third parties. It is required to include invisible information (hidden image or hidden information for anti-counterfeiting) for the purpose. Therefore, Japanese Patent No. 4649658 (Patent Document 1) discloses an authentication system capable of reading invisible information as described above. FIG. 1 shows the configuration of the authentication system disclosed in Patent Document 1.

Further, the image reading device 100 provided with the authentication system disclosed in Patent Document 1 is a "net dot printed matter" composed of a region that does not absorb infrared rays and a region that absorbs infrared rays (referred to as an IR image or an embedded image). When reading 105, the illumination unit 104 illuminates the mesh dot printed matter 105, and an image pickup unit (camera) 103 having sensitivity in the IR region is used for taking a picture. Then, the technique of visually confirming the embedded pattern by the observer by the display monitor of the authentication terminal 102 is disclosed.

In Patent Document 1, the IR image is subjected to image processing (Hartley transform) so that it can be matched with the genuine image, and the IR image in which the QR code (registered trademark) information is embedded is on the floor. It is disclosed that hidden information such as personal information is extracted after performing the key conversion.

Next, Japanese Patent Application Laid-Open No. 9-147178 (Patent Document 2) describes a copy-prevention pattern input as an image using a CCD camera or an optical scanner in a printed matter on which a copy-prevention pattern having a latent image is printed. By performing predetermined image processing (binarization processing, image expansion processing, contraction processing of the same amount as when expansion is performed), a binarized image in which a latent image is a prominent connecting component is recognized. , A method for reading and inspecting a printed matter for determining authenticity by collating with a genuine image and an apparatus thereof are disclosed.

Conventionally, in authenticity determination of printed matter, it depends on material suitability such as detecting functional inks such as magnetic inks, infrared reflection absorbing inks, fluorescent inks, and materials made of fibers, materials, chemicals, etc. that form a printing medium. However, in the read inspection method for printed matter disclosed in Patent Document 2, a pattern printed with a printing material applicable to a commonly used printing ink can be optically read.

Next, Japanese Patent Application Laid-Open No. 2008-152450 (Patent Document 3) concatenates an edge image of a latent image pattern by extracting a perimeter pattern as a concatenated region by performing expansion and contraction calculations. The size of the area and the position information can be obtained. Then, by comparing the size and position information of the connecting region with the preset reference values, the authenticity determination device for the paper sheets and the paper leaves that determine the authenticity of the paper leaves having a latent image pattern. The authenticity discrimination method is disclosed.

Further, the authenticity discriminating method and its apparatus disclosed in Patent Document 3 are used to project in the direction of the perimeter in the regions at both ends of the perimeter pattern region even if the paper leaves are tilted. Since the position of the universal line at both ends can be detected, the bright and dark universal line pattern can be extracted from the paper sheets with high accuracy and efficiency regardless of the tilt angle.

Next, Masato Kiuchi, Susumu Kiuchi, "Discovery and Utilization of Visible Image Regions in Phase Modulation Patterns", Journal of the Printing Society, Japan Printing Society, November 2011, Vol. 48, No. 5, p.325 In −334 (Non-Patent Document 1), an invisible image area and a visible image area are arranged in a printed matter (hereinafter referred to as “security printed matter”) for which security is required, and the invisible image area is a latent image. It can be composed of a part and a background part. It is disclosed that the configuration imparts rich design and a clear switch effect when an invisible image appears to a security printed matter.

Regarding the confidentiality of the invisible image region, Non-Patent Document 1 states that the image line A constituting the latent image portion and the image line A'constituting the background portion cancel each other out in a bright and dark state. It is disclosed that the embedded latent image is not recognized by the observer, and the observer can see only the visible image having a design.

Here, the principle of easily expressing (exposing) an invisible image by superimposing a discriminator (for example, a lenticular lens) on the printed area of the printed matter and discriminating the authenticity will be described in detail with reference to FIG. explain.

First, FIG. 2 shows an enlarged view of the print area. As shown in FIG. 2, the print area has an area composed of an image line A, which is also called a latent image portion, and an image line A', which is also called a background portion. Further, since a region C called a visible image region exists between the image line A and the image line A', the pattern is usually visible to the observer.

Further, as shown in FIG. 2, the image lines A are arranged in parallel at intervals Sv, forming an invisible image region. The distance between the image lines A'is the same as that of the image line A, and the image lines A'also form an invisible image region.

As shown in FIG. 2, the region in which the image line A, the image line C, the image line A'and the image line C are combined is repeated at the interval (pitch) Sv. The combination area is the smallest unit area.

The areas of the image line A and the image line A'are the same or substantially the same, and the brightness of the image line A and the brightness of the image line A'are complementary in that one is bright and the other is dark. It is in a light-dark relationship) and is designed to offset the brightness. Therefore, the image formed by the image line A and the image line A'is not easily visually recognized by the observer. As a result, the latent image (invisible image) can be hidden in the print area.

During normal observation, by arranging the artistic pattern in the visible image area (area C), the effect of improving the design (aesthetics) of the printed matter can be obtained. ) Is used to reveal (visualize) only one of the image line A (latent image portion) and the image line A'(background portion) so that the observer can visually recognize the invisible image.

For example, as shown in FIG. 2, when the center position (line) of the lenticular lens 8 is superimposed on the center line L1 of the image line A, the observer visually recognizes the image line A (latent image portion) as a positive image. be able to. Similarly, when the center position (line) of the lenticular lens 8 is superimposed on the center line L2 of the image line A', the observer visually recognizes the image line A'(background portion) as a negative image for the latent image portion. Can be done.

Further, by rotating the discriminator, it is possible to reveal different invisible images that do not depend on the image line A or the image line A'.

Therefore, FIG. 3 shows an enlarged view of a print area in which the image lines B and B'are 90 ° different from the image line A or the image line A', and the image lines B and B'are arranged in the print area. As shown in FIG. 3, in the print area, the image lines B are arranged in parallel at intervals of Sh, forming an invisible image area. The distance between the image lines B'is the same as that of the image line B, and the image lines B'also form an invisible image region.

As shown in FIG. 3, the region where the image line B, the image line C, the image line B'and the image line C are combined is repeated at the interval (pitch) Sh. The combination area is the smallest unit area.

As shown in FIG. 3, when the center position (line) of the lenticular lens 8 is superimposed on the center line L3 of the image line B, the observer causes the image line B (latent image portion) as described in FIG. ) Can be visually recognized as a positive image. Similarly, when the center position (line) of the lenticular lens 8 is superimposed on the center line L4 on the image line B', the observer visually recognizes the image line B'(background portion) as a negative image with respect to the latent image portion. can do.

Further, by mixing the image line A, the image line A', the image line B, and the image line B'in the print area, the latent image portion and the background portion printed in the print area can be made multi-directional. Then, it is considered that the latent image to be manifested, that is, the image to be visually recognized can be dramatically switched by changing the direction of the determination tool with respect to the printed area in which the latent image is multidirectional.

As an example of a print area in which the latent image portion and the background portion are multidirectional (bidirectional), an enlarged view of the print area in which the print area shown in FIG. 2 and the print area shown in FIG. 3 are mixed is shown. , FIG. 4. In FIG. 4, the image line A and the image line A'are arranged in parallel at a distance of Sv / 2, and the image line B and the image line B'are arranged in parallel at a distance of Sh / 2. The visible image area D is formed in the print area excluding A, the image line A', the image line B, and the image line B'. Although not shown, the image lines A are arranged in parallel at a distance of Sv, and the image lines B are arranged in parallel at a distance of Sh. The same applies to the drawing lines A'and the drawing lines B'.

When the print area is configured in this way, as shown in FIG. 4, when the center position (line) of the lenticular lens 8 is laterally superimposed on the center lines L1 and L2, the image line A (latent image portion) is displayed by the observer, respectively. ) Can be visually recognized as a positive image, and the image line A'(background portion) can be visually recognized as a negative image with respect to the latent image portion.

Similarly, when the center position (line) of the lenticular lens 8 is superimposed on the center lines L3 and L4 in the vertical direction, the observer sees the image line B (latent image portion) as a positive image and the image line B'(background). The part) can be visually recognized as a negative image with respect to the latent image part. That is, by switching between the vertical placement and the horizontal placement of the lenticular lens 8, the effect of dramatically switching the decoded invisible image (image switching effect) is obtained.

In addition, Hieizan-ji, "Partial latentization by error diffusion method in checker pattern carrier screen image", IPSJ Instruction 2015, pp. 753-758 (Non-Patent Document 2) discloses a technique of replacing each pixel of a secret image with two types of checker patterns and converting the secret image into a checker pattern carrier screen image. As a result of this conversion, the number of pixels of the checker pattern carrier screen image becomes four times (equal to 2 × 2 times) that of the secret image.

In Non-Patent Document 2, the checker pattern carrier screen image can be decoded by performing sampling processing using a commercially available digital camera, that is, the checker pattern carrier screen image is reduced by the liquid crystal finder of the digital camera. It is disclosed that the process of resampling the carrier screen image for display can be utilized in the decryption process of the secret image.

Here, a technique for making a secret image latent (latent image) by converting it into a checkered pattern carrier screen image will be described.

First, the process of converting the secret image into the checker pattern carrier screen image is a process of converting each pixel into a checker pattern of 2 × 2 pixels different from each other, as shown in FIGS. 5 and 6.

Here, regarding the arrangement of the checker pattern in the checker carrier pattern image, the positions of the lower left, the lower right, the upper left and the upper right are (0,0), (1,0), (0,1) and the positions of the lower left, the lower right, the upper left and the upper right when viewed from the center. Let it be (1,1).

Regarding the conversion method, for example, as shown in FIG. 5, if the pixel of the secret image to be converted is white, the pixel is a black pixel at the position (0,0) and (1,1) of the checker pattern pixel. , And the positions (1,0) and (0,1) are replaced with a 2 × 2 size checker pattern in which white pixels are arranged.

On the other hand, if the pixel of the secret image to be converted is black as shown in FIG. 6, the pixel is a white pixel at the positions (0,0) and (1,1), and (1,0) and ( It is replaced with a 2 × 2 size checker pattern in which black pixels are arranged at positions 0 and 1). In such a conversion, the checker pattern is replaced with a 2 × 2 pixel checker pattern in which the black pixels and the white pixels of the carrier screen image are the same, so that the difference in brightness does not appear. Due to this feature, the observer cannot easily see the checkered pattern carrier screen image.

Next, it is explained that the secret image can be decoded by performing the process of thinning out the pixels (reduction process) on the checker pattern carrier screen image after conversion. The process of thinning out the pixels at a predetermined ratio is the process of reducing the image.

First, if the pixels located at (0,1) or (1,0) of the checker pattern are selected and displayed with respect to the checker pattern carrier screen image, the white pixels of the secret image are decoded by the white pixels as before. Similarly, the black pixels of the secret image are displayed after being decoded. In this way, the secret image (positive image) is decoded.

On the other hand, if the pixels located at (0,0) or (1,1) of the checker pattern are selected and displayed with respect to the converted checker pattern carrier screen image, the white pixels of the secret image are inverted. , The black pixel is selected and displayed, and similarly, the black pixel of the secret image is inverted and the white pixel is selected and displayed. In this way, the black-and-white inverted image (negative image) of the secret image is decoded.

A specific character character ('A','B') is converted into a checker pattern as a secret image, and pixels corresponding to (0, 1) or (0, 1) of a 2 × 2 size checker pattern are selected. Then, a secret image (positive image) is decoded and displayed as an example is shown in FIGS. 7 and 8.

Japanese Patent No. 4649658 Japanese Unexamined Patent Publication No. 9-147178 Japanese Unexamined Patent Publication No. 2008-152450

Masato Kiuchi, Susumu Kiuchi, "Discovery and Utilization of Visible Image Region in Phase Modulation Patterns", Journal of Printing Society, Japan Printing Society, November 2011, Vol. 48, No. 5, p.325-334 Hieizan-ji, "Partial latentization by error diffusion method in checker pattern carrier screen image", IPSJ Instruction 2015, pp. 753-758

The authentication system disclosed in Patent Document 1 must read invisible information using a camera having sensitivity in the IR region, and cannot read invisible information using, for example, a commercially available digital camera.

Further, since the hidden image and information for authentication are embedded only by printing the symbol for authentication, they cannot be collated at the same time as the information of the certificate provided with the IC chip.

Next, in the read inspection method for printed matter disclosed in Patent Document 2 and its apparatus, when complicated image processing (binarization, image expansion, expansion) is performed on the copy protection pattern obtained by inputting. It is necessary to perform the same amount of shrinkage). Further, since the copy prevention pattern (the portion to which the latent image is applied) to be handled is composed of a set of image lines having two or more lines, it is not possible to easily determine the authenticity by a discriminator.

Next, in the latent image pattern handled by the paper leaf authenticity discrimination device and the paper leaf authenticity discrimination method disclosed in Patent Document 3, characters and patterns can be confirmed when visually observed from a special angle. It's like that.

Further, in the security printed matter disclosed in Non-Patent Document 1 and the authenticity determination method thereof, since the observer determines the authenticity by visual recognition using a determination tool, it is difficult to perform the authenticity determination in a large amount and at high speed. ..

Next, in Non-Patent Document 2, the secret image is decoded by adjusting the shooting distance, angle, etc. using a general compact digital camera for the latent image technique using the checker pattern carrier screen image. Although the method of doing so is disclosed, the decoded image is accompanied by a remarkable striped pattern. Such a striped pattern is an obstacle to the separation of each character area and the background area of the secret image. Such a striped pattern makes it very difficult to perform a series of processes of recognizing each character area as a concatenated area (concatenated component), comparing it with a character pattern, and performing pattern matching (pattern recognition). ..

In view of the above circumstances, the present invention reduces an image (hereinafter referred to as an original image) taken by using a commercially available image pickup device (for example, a digital camera) while moving a reference point for the reduction process (thinning process). By performing image processing such as decoding an invisible image and then taking a difference from the visible image, a striped pattern (striped pattern) is generated when the invisible image is decoded. Even in such a case, it is an object of the present invention to provide an authentication system, an authentication method, and an authentication program capable of easily extracting a character area and easily performing OCR processing.

The above object of the authentication system according to the present invention is a print area composed of a visible area on which a visible information or a visible image is printed and an invisible area consisting of a hidden image portion and a background portion on which a hidden image or the hidden information is printed. An image capture unit that includes an image capture unit that captures a printed matter in which the image is arranged, and an authentication terminal that authenticates the concealed image or the concealed information. The image capture unit is a lighting unit that irradiates the printed matter with light. And an image pickup unit that captures the printed matter and acquires the original image of the printed area, the authentication terminal is provided with a predetermined pixel in the captured image as a reference point, and the reference point is used as a reference. The original image is reduced at a predetermined reduction rate to generate a reduced image, and the reduced image is enlarged at a magnification that is the inverse of the reduction rate with the reference point as a reference, and the number of pixels of the original image. The same interpolation processing as is performed to generate an enlarged image, the operation of subtracting the brightness value of each pixel of the original image from the brightness value of each pixel of the enlarged image is performed, and the difference image data is generated to generate the difference. The background area and the character area are separated from the image data, the reference point is shifted in a predetermined direction in pixel units, the character area extracted from the difference image data is collated with the character pattern, and OCR is performed. Is performed, and the concealed image or the concealed information is authenticated.

Further, the above object of the authentication system according to the present invention is composed of a visible region on which visible information or a visible image is printed, and an invisible region including a hidden image portion or a background portion on which a hidden image or hidden information is printed. An authentication system including an image capture unit that captures a printed matter in which a print area is arranged and an authentication terminal that authenticates the hidden image or the hidden information, and the image capture unit irradiates the printed matter with light. The authentication terminal includes an illumination unit and an image pickup unit that captures an image of the printed matter and acquires an original image of the print area. The authentication terminal is provided with a predetermined pixel in the captured image as a reference point, and the reference point is used as a reference point. The original image is reduced at a predetermined reduction rate to generate a reduced image, and the reduced image is enlarged at a magnification that is the inverse of the reduction rate with the reference point as a reference. An enlarged image is generated by performing an interpolation process that is the same as the number of pixels, and a calculation is performed in which the brightness value of each pixel of the original image is subtracted from the brightness value of each pixel of the enlarged image to generate difference image data. By labeling the difference image data, a label number is generated, the label number is stored in the label area so that a one-to-one correspondence with the difference image data can be attached, and the label number is stored based on the label number. The background area and the character area are separated from the difference image data, the reference point is shifted in a predetermined direction in pixel units, and the character area extracted from the difference image data and the character pattern are collated. , OCR and authenticate the concealed image or the concealed information.

Further, the object of the authentication system according to the present invention is that a plurality of minimum unit areas having a predetermined area are arranged at a predetermined pitch in the print area, and the minimum unit area has a first image and a second image. The third image is arranged at the predetermined pitch, and the third image is arranged in a region where the first image and the second image do not exist. Is composed of the first image, the background portion is composed of the second image, the visible region is composed of the third image, the first image, and the second image. And the third image are arranged so as to be parallel to each other in a linear region, and when one of the first image and the second image is optically on. , The other is off, or there is a complementary relationship such that the sum of the brightness value of the first image line and the brightness value of the second image line becomes a predetermined brightness value, and the latent image unit The positive image is formed by the background portion, and the negative image of the latent image portion is formed by the background portion, or the width of the minimum unit region is 1 mm or less, or the area of the first image line. And the area of the second image is the same or substantially the same, or the reference point is a pixel whose brightness value or gradation data does not change before and after the reduction process, or the above. In the printed matter, the concealed image or the concealed information is given by the net dot composition by the pattern composed of the dots arranged periodically, or the concealed information is a QR code (registered) that cannot be recognized by the naked eye. By being (trademark), or when the secret image is embedded in the invisible region and the pixels of the secret image are black, it is converted into the first checker pattern of 2 rows and 2 columns, and the pixels of the secret image are white. In the case of, the first checker pattern and the black and white are inverted into the second checkered pattern of 2 rows and 2 columns, which is converted into the hidden image, or from the IC chip embedded in the printed matter to the IC reader. By collating the information read by the writer with the concealed information acquired based on the character area by the OCR and determining the authenticity of the printed matter, or by the image pickup unit being a CCD line sensor camera or a CCD. This is achieved more effectively by being an area sensor camera.

Further, the above object of the authentication method according to the present invention is composed of a visible region on which visible information or a visible image is printed, and an invisible region including a hidden image portion or a background portion on which a hidden image or hidden information is printed. It is an authentication method for authenticating the hidden image or the hidden information by using an authentication system including an image acquisition unit and an authentication terminal in a printed matter in which a print area is arranged, and the image acquisition unit is used to perform the above-mentioned. A step of photographing a printed matter and acquiring an original image of the print area, and using the authentication terminal, a predetermined pixel in the photographed image is provided as a reference point, and the original image is obtained with the reference point as a reference. Using the authentication terminal and a step of reducing the image at a predetermined reduction rate to generate a reduced image, the reduced image is enlarged at an enlargement rate that is the inverse of the reduction rate, with the reference point as a reference. Using the step of generating an enlarged image by performing an interpolation process that is the same as the number of pixels of the original image and the authentication terminal, the brightness value of each pixel of the original image is calculated from the brightness value of each pixel of the enlarged image. A step of performing a subtraction operation to generate a difference image data, a step of separating a character area and a background area other than the character area from the difference image data by using the authentication terminal, and a step of using the authentication terminal. A step of shifting the reference point in a predetermined direction on a pixel-by-pixel basis, a step of collating the character area extracted from the difference image data with a character pattern using the authentication terminal, and performing OCR, and the authentication. It is accomplished by comprising a step of authenticating the concealed image or the concealed information based on the result of the OCR using a terminal.

Further, the above object of the authentication method according to the present invention is composed of a visible region on which visible information or a visible image is printed, and an invisible region consisting of a hidden image portion or a background portion on which a hidden image or hidden information is printed. It is an authentication method for authenticating the concealed image or the concealed information by using an authentication system including an image capture unit and an authentication terminal in a printed matter in which a print area is arranged, and the image capture unit is used to perform the above-mentioned. Using the step of photographing a printed matter and acquiring the original image of the print area and the authentication terminal, a predetermined pixel in the photographed image is provided as a reference point, and the original image is obtained with the reference point as a reference. Using the authentication terminal and the step of reducing the image at a predetermined reduction rate to generate a reduced image, the reduced image is enlarged at an enlargement rate that is the inverse of the reduction rate, with the reference point as a reference. Using the step of generating an enlarged image by performing an interpolation process that is the same as the number of pixels of the original image and the authentication terminal, the brightness value of each pixel of the original image is calculated from the brightness value of each pixel of the enlarged image. A step of performing a deduction operation to generate a difference image data, a step of generating a label number by labeling the difference image data using the authentication terminal, and a step of generating the difference image using the authentication terminal. Using the step of storing the label number in the label area and the authentication terminal so that a one-to-one correspondence with the data can be attached, the character area and the character area from the difference image data based on the label number. The step of separating the background area other than the above, the step of shifting the reference point in a predetermined direction on a pixel-by-pixel basis using the authentication terminal, and the step of shifting the reference point in a predetermined direction using the authentication terminal, and the step of extracting from the difference image data using the authentication terminal. It is achieved by including a step of collating a character area and a character pattern and performing OCR, and a step of authenticating the hidden image or the hidden information based on the result of the OCR using the authentication terminal. To.

Further, the above object of the authentication program according to the present invention is composed of a visible region on which visible information or a visible image is printed, and an invisible region including a hidden image or a hidden image portion and a background portion on which the hidden image or hidden information is printed. This is an authentication program for causing a computer to authenticate the hidden image or the hidden information in the printed matter in which the printed matter is arranged, and is a step of photographing the printed matter and acquiring the original image of the printed area. A step of providing a predetermined pixel in the captured image as a reference point, reducing the original image at a predetermined reduction rate with the reference point as a reference, and generating a reduced image, and using the reference point as a reference. A step of enlarging the reduced image at an enlargement ratio that is the inverse of the reduction ratio and performing an interpolation process that is the same as the number of pixels of the original image to generate an enlarged image, and a step of each pixel of the enlarged image. A step of generating a difference image data by performing an operation of subtracting the brightness value of each pixel of the original image from the brightness value, a step of separating a character area and a background area other than the character area from the difference image data, and the above-mentioned step. The step of shifting the reference point in a predetermined direction on a pixel-by-pixel basis, the step of collating the character area extracted from the difference image data with the character pattern and performing OCR, and the concealment based on the result of the OCR. It is accomplished by consisting of a step of authenticating the image or the concealed information.

Further, the above object of the authentication program according to the present invention is composed of a visible region on which visible information or a visible image is printed, and an invisible region including a hidden image or a hidden image portion and a background portion on which the hidden image or hidden information is printed. This is an authentication program for causing a computer to authenticate the hidden image or the hidden information in the printed matter in which the printed matter is arranged, and is a step of photographing the printed matter and acquiring the original image of the printed area. A step of providing a predetermined pixel in the captured image as a reference point, reducing the original image at a predetermined reduction rate with the reference point as a reference, and generating a reduced image, and using the reference point as a reference. A step of enlarging the reduced image at an enlargement ratio that is the inverse of the reduction ratio and performing an interpolation process that is the same as the number of pixels of the original image to generate an enlarged image, and a step of each pixel of the enlarged image. A step of generating a difference image data by performing an operation of subtracting the brightness value of each pixel of the original image from the brightness value, a step of generating a label number by labeling the difference image data, and the difference image data. The step of storing the label number in the label area and the background area other than the character area are separated from the difference image data based on the label number so that a one-to-one correspondence with the image can be obtained. Based on the step, the step of shifting the reference point in pixel units in a predetermined direction, the step of collating the character area extracted from the difference image data with the character pattern, and performing OCR, and the result of the OCR. It is achieved by comprising the step of authenticating the concealed image or the concealed information.

According to the present invention, an invisible image is decoded by performing a reduction process (thinning process) while moving a reference point for the reduction process on an original image taken by using a commercially available image pickup device (for example, a digital camera). Then, it is possible to obtain a difference image by performing image processing such as taking a difference from the original image. By such image processing, even when a striped pattern (striped pattern) is generated when decoding an invisible image, it is easy to extract a character area, and optical character recognition (Optical Character Recognition) can be easily performed. Hereinafter, an authentication method capable of performing OCR processing), an authentication system thereof, and an authentication program will be provided.

It is a schematic diagram which shows an example of the conventional authentication system. It is a figure which shows the arrangement of the horizontal lenticular lens so that an invisible image area (latent image part A and a background part A'), a visible image area C, and a latent image part A can be observed in a print area. It is a figure which shows the arrangement of the vertical lenticular lens which can observe an invisible image area (latent image part B and a background part B'), a visible image area C, and a latent image part B in a print area. Arrangement of a horizontally placed lenticular lens so that the invisible image area (latent image portion A, background portion A', latent image portion B, and background portion B'), visible image region C, and latent image portion A can be observed in the print area. It is a figure which shows the arrangement of the lenticular lens placed vertically so that the latent image part B can observe. It is a figure which shows the method of converting the white pixel of a secret image into a 2 × 2 checker pattern of a checker pattern carrier screen image, and decoding it. It is a figure which shows the method of converting a black pixel of a secret image into a 2 × 2 checker pattern of a checker pattern carrier screen image, and decoding it. It is a figure which shows the example which converted the character character ('A') into a checker pattern as an original image, decoded a secret image (positive image), and displayed it. It is a figure which shows the example which converted the character character ('B') into a checker pattern as an original image, decoded a secret image (positive image), and displayed it. It is a schematic diagram which shows an example of the authentication system in embodiment of this invention. It is a block diagram of the authentication system in embodiment of this invention. It is a figure which shows the pixel arrangement of a digital camera. It is a figure which shows an example of reducing and displaying the image data taken with a digital camera. It is a figure which shows an example of the correspondence relation with the pixel arrangement of a digital camera, and the print area (latent image part A and background part A'). It is a figure which shows the area which is displayed when the image of a digital camera is reduced and displayed (the state that the latent image part A selectively remains as a display). It is a figure which shows the state that the angle θ is generated between the direction of the latent image part A, and the direction of a pixel arrangement when the image of a digital camera is reduced and displayed. It is a figure which shows an example of the correspondence relation with the pixel arrangement of a digital camera, and the print area (latent image part B, background part B'). It is a figure which shows the area which is displayed when the image of a digital camera is reduced and displayed (the state that the latent image part B selectively remains as a display is shown). It is a figure which shows the state that the angle θ is generated between the direction of the latent image part B, and the direction of a pixel arrangement when the image of a digital camera is reduced and displayed. It is a figure which shows the original image which photographed the print area using a digital camera. It is a reduced image acquired by performing a reduction process using a reduction ratio initially set for the original image obtained by capturing the print area using a digital camera. It is a figure which shows the character area of the connection area obtained by adjusting (stretching) the cycle of a striped pattern (striped pattern) by adjusting the reduction ratio. It is a difference image obtained by subtracting the components of the original image from the enlarged enlarged image after the reduction processing of the original image. It is a figure which shows the state that the connection area "1" was extracted by performing the labeling process on the difference image. It is a difference image decoded by using the enlarged enlarged image after the reduction process in which the reference point is reset. It is a figure which shows the state that the connection area "2" and "3" were extracted by performing the labeling process on the difference image. It is a difference image decoded by setting the reference point again. It is a figure which shows the state that the connection area "4" was extracted by performing the labeling process on the difference image. It is a figure which shows the composite character area by connecting the character area which became the connection area of a positive area by using four difference images. It is a figure which shows the example of the positional relationship of a missing pixel and 4 pixels around it in the bilinear interpolation method. It is a sample image of the difference image binarized before the labeling process in the embodiment of the present invention. It is a figure which shows the matching pattern used for the labeling process in embodiment of this invention. It is a figure which shows the initialized label area in embodiment of this invention. It is a figure which shows the state which the attention pixel of the first black pixel was detected in the binarized difference image in embodiment of this invention. In the embodiment of the present invention, it is a figure which shows the labeling process at the time of detecting the attention pixel of the first black pixel. It is a figure which shows the appearance which the attention pixel of the 2nd black pixel was detected in the binarized difference image in embodiment of this invention. It is a figure which shows the labeling process at the time of detecting the attention pixel of the 2nd black pixel in embodiment of this invention. It is a figure which shows the state which the attention pixel of the 7th black pixel was detected in the binarized difference image in embodiment of this invention. In the embodiment of the present invention, it is a figure which shows the labeling process at the time of detecting the attention pixel of the 7th black pixel. It is a figure which shows the state which the attention pixel of the 14th black pixel was detected in the binarized difference image in embodiment of this invention. It is a figure which shows the labeling process at the time of detecting the attention pixel of the 14th black pixel in embodiment of this invention. It is a figure which shows the appearance that the matching pattern reached the lower left, and the scanning was completed in the binarized difference image in embodiment of this invention. In the embodiment of the present invention, it is a figure which shows the appearance that the label number was assigned to the label area by the labeling process. It is a figure which shows the appearance that the label number was corrected in the embodiment of this invention. It is a figure which shows the appearance that the label number stored in the look-up table was corrected in the embodiment of this invention. It is a flowchart which shows the authentication flow in the authentication system of embodiment of this invention.

According to the authentication system, the authentication method, and the authentication program of the present invention, the original image taken by using a commercially available image pickup device (for example, a digital camera) is reduced (thinned out) while moving the reference point of the reduction processing. ) Is performed to decode the invisible image, and then the difference image obtained by performing image processing such as taking the difference between the decoded image and the original image is used to obtain a striped pattern (stripes) when the invisible image is decoded. Even when a pattern) is generated, the character area can be easily extracted and the OCR process can be easily performed.

An embodiment of the integrated authentication system in the present invention will be described with reference to the drawings. The configuration of the authentication system in the present invention is shown in FIG.

The authentication system 10 of the present invention is composed of an image acquisition device 1 and an authentication terminal 2. The image capture device 1 includes an image pickup unit 3, an illumination unit 4, an interface unit 5, and a housing unit 6, and a concealed image (secret image) or concealed information is printed on the housing unit 6. Specimens (for example, printed matter, IC cards, etc.) 7 are placed on the table.

Further, the authentication terminal 2 (for example, a personal computer or a laptop computer) is composed of a control unit 2a, a storage unit 2b, a display unit 2c, and the like.

A block diagram of the authentication system according to the embodiment of the present invention is shown in FIG.

The illumination unit 4 in the authentication system 10 is a means for irradiating the subject 7 with light, and is provided with either IR illumination, visible light illumination including transmitted light, or UV illumination. Normally, when a concealed image is taken, it is possible to take a picture in a natural state such as sunlight. However, when the light is weak at night or indoors and the desired image cannot be obtained, appropriate lighting can be selected from IR lighting, visible light lighting, or UV lighting so that irradiation corresponding to the concealed image is possible. ing.

Further, the imaging unit 3 is a means for acquiring a predetermined number of original images obtained by imaging a subject 7 containing a concealed image or concealed information a predetermined number of times in a predetermined wavelength region (usually, a visible light region). .. When taking pictures twice or more, the relative positional relationship between the image pickup unit 3 and the subject 7 can be fixed so that the imaged portion of the printed matter does not change in each image. For example, as the fixing means of the image pickup unit 3, an instrument such as a tripod or a stand may be used for fixing.

The control unit 2a in the authentication terminal 2 acquires the original image taken by the image pickup unit 3 via the interface unit 5 and stores it in the storage unit 2b. The control unit 2a performs an operation such as image processing on the image information, displays the operation result on the display unit 2c, and stores it in the storage unit 2b. Then, the hidden image or the hidden information is authenticated based on the calculation result stored in the storage unit 2b. Further, when the IC chip is embedded in the subject 7, the information of the IC chip is read and the invisible information or the hidden information printed on the printed matter is collated with the information.

Next, an image process for making an invisible image manifest (visualize) from the image information obtained by photographing the print area of the subject 7 will be described.

First, FIG. 11 shows an enlarged example of a part of the pixel arrangement of the image pickup unit 3, for example, the liquid crystal monitor of a commercially available digital camera. As shown in FIG. 11, pixels in the range of -3 to +7 rows centered on the mth row in the vertical direction and in the range of -2 rows to +5 rows centered on the n columns in the horizontal direction are arranged.

When a subject is photographed using a commercially available digital camera, a brightness value (for example, 0 to 255 (8-bit) gradation data) is stored in a storage device (memory element) inside the digital camera for each pixel as shown in FIG. It is systematically stored as image information (original image). That is, the brightness distribution (spatial arrangement) of the print area of the subject 7 is subdivided according to the resolution (resolution) of the digital camera, converted into the brightness value of each pixel, and the image information (eg,) in each area in the memory. It is saved as array data).

Next, the acquired image information is reduced (thinned out). A simple example thereof is shown in FIG. FIG. 12 is an image process in which the pixels of two rows out of three rows are thinned out from the original image before processing so that the pixels are not displayed, and the pixels of the remaining one row without thinning out are displayed. This is just one example.

Next, FIG. 13 shows a state in which the print area in which the invisible area (image line A, image line A') and the visible area (area C) are printed and the pixel arrangement of the digital camera are superimposed. As shown in FIG. 13, the pixel arrangement of the digital camera shows the range of the -3rd to +7th rows and the 2nd to +5th columns centering on the intersecting pixels of the Mth row and the Nth column, and M. The gradation data of the image line A and the visible region (area C) are written in the line A, the M + 3 line, and the M + 6 line, and the M-2 line, the M-1 line, the M + 1 line, and the M + 2 line are written. The gradation data of the image line A'and the visible region (region C) are written in the eyes, the M + 4th line, and the M + 5th line.

Then, as shown in FIG. 13, the gradations of both the image line A and the image line A'are arranged in the pixel information captured by the digital camera. Then, the areas of the image line A and the image line A'are the same or substantially the same, and the brightness of the image line A and the brightness of the image line A'are a light-dark relationship (complementary) that one is bright and the other is dark. Because of the relationship), a uniform image component of almost gray is formed. As a result, neither the image embedded by the image line A in the print area nor the image embedded by the image line A'in the print area can be visually recognized by the observer. On the other hand, the visible image (region C) printed in the visible region indicates that the observer can visually recognize it.

Next, in FIG. 14, the image information (original image) of the digital camera before processing is processed by thinning out the pixels of two lines in the three lines so as not to be displayed, and the thinning process is performed. An example is shown in which image processing is performed to display the pixels for the remaining one line.

In FIG. 14, the pixels arranged in the Mth line, the M + 3rd line, and the M + 6th line in which the gradation data of the image line A and the area C are written are displayed, and the floors of the image line A'and the area C are displayed. The pixels arranged in the M-2nd line, M-1st line, M + 1st line, M + 2nd line, M + 4th line, and M + 5th line in which the adjustment data is written are reduced (thinned out) so as not to be displayed. The state of performing the processing) is shown. Then, only the pixel information in which the gradation data of the image line A is written is displayed (extracted), and the observer can authenticate the decoded latent image portion (positive image).

On the other hand, the pixels arranged in the M-1st line, the M + 2nd line, and the M + 5th line in which the gradation data of the image line A'is written are displayed, and the gradation data of the image line A is written. Considering the case where image processing is performed so that the pixels arranged in the Mth line, M + 3rd line, and M + 6th line are not displayed, the pixel in which the gradation data of the image line A'is written is written. Since only is displayed (extracted), the observer can authenticate the decoded background portion (negative image for the latent image portion).

However, it is practically difficult to match the direction of the pixel arrangement of the digital camera with the direction of the image line A and the image line A'. Therefore, in the pixel array A (M, N + 3), as shown in FIG. 15, the direction of the pixel array of the digital camera and the direction of the image line A and the image line A'are deviated so as to form an angle θ. It is easy to occur. The pixel array A (M, N + 3) existing at a distance L sufficiently distant from the position where the pixel array A (M, N-3) of the digital camera overlaps with the image line A almost overlaps with the image line A. It does not overlap with the area C. Therefore, it is considered that the observer recognizes that the latent image portion, that is, the positive image disappears and the visible image is displayed. Therefore, it is considered that the positive image can be displayed again by adopting B (M + 1, N + 3) shifted upward by one pixel of the image array A (M, N + 3) as the display pixel.

Next, FIG. 16 shows an enlarged view in which the print area in which the invisible area (image line B, image line B') and the visible area (area C) are printed and the pixel arrangement of the digital camera are superimposed.

As shown in FIG. 16, the pixel arrangement of the digital camera shows the range of the -2 to +7th row and the -3 to +3th column centering on the intersecting pixel of the mth row and the nth column, and N The gradation data of the image line B is written in the third column, the Nth column, and the N + 3rd column, and the gradation data of the image line B'is written in the N-2nd column and the N + 1th column.

Further, as shown in FIG. 16, the gradations of both the image line B and the image line B'are arranged in the pixel information of the digital camera. Then, the areas of the image line B and the image line B'are the same or substantially the same, and the brightness of the image line B and the brightness of the image line B'are in a complementary relationship. Neither the invisible image (latent image portion) embedded in the image nor the invisible image (background portion) embedded by the image line B'in the print area can be visually recognized by the observer. On the other hand, the visible image (region C) printed in the visible region indicates that the observer can visually recognize it.

Next, as shown in FIG. 17, the pixels of two rows in the three rows are thinned out from the image (original image) of the digital camera before the image processing so as not to be displayed, and the pixels are not thinned out. Image processing is performed to display the pixels for the remaining one column.

As shown in FIG. 17, the pixels arranged in the N-3rd column and the Nth column in which the gradation data of the image line B and the area C are written are displayed, and the gradation of the image line B'and the area C is displayed. When the pixels arranged in the N-2nd column and the N + 1th column to which the data is written are thinned out so as not to be displayed, only the pixels in which the gradation data of the image line B and the area C are written are written. It is displayed (extracted). Therefore, the observer can visually recognize the decoded latent image portion (positive image). Further, if only the pixels arranged in the N-2nd column and the N + 2nd column in which the gradation data of the image line B'is written are displayed (extracted), the observer is decoded. The background part (negative image with respect to the latent image part) can be visually recognized.

By the way, as shown in FIG. 18, it is practically difficult to match the direction of the pixel arrangement of the digital camera with the direction of the image line B and the image line B'. Therefore, as shown in FIG. 18, the direction of the pixel arrangement of the digital camera and the direction of the image line B and the image line B'are likely to deviate so as to form an angle θ. The pixel array B (M, N) existing at a distance L'sufficiently distant from the position where the pixel array B (M + 7, N) of the digital camera overlaps with the image line B does not overlap with the image line B. It overlaps with the area C. Therefore, it is considered that the pixel array B (M, N) is separated from the image line B (latent image portion) and overlaps with the region C, and the observer recognizes that the visible image is displayed. Therefore, it is considered that the positive image can be displayed again by adopting B (M, N + 1), which is shifted to the left by one pixel of the image array B (M, N), as the display pixel.

Next, when a photograph is taken using a digital camera and a reduction process (substantially, a thinning process as described above) is performed, the appearance of the printed area in which the invisible image is embedded will be examined.

First, FIG. 19 shows an image diagram (schematic diagram) of image information obtained by photographing a print area in which an invisible image is embedded using a digital camera. Here, the image information shown in FIG. 19 is used as the original image. Ideally, the reduced image obtained by reducing the original image has a substantially constant difference between the gradation data in the background region and the gradation data in the character region. For example, if the reduced image is a positive image, the gradation data in the character area is lower than the gradation data in the background area. On the contrary, in the case of a negative image, if the image information is a positive image, the gradation data in the character region is higher than the gradation data in the background region. In other words, the character area is a connected area (connected component) so that the magnitude relationship between the gradation data of one character area and the gradation data of the background area surrounding the character area is not inverted. If. In such a case, the character area and the background area can be easily separated.

However, when the image information obtained by actually capturing the print area is reduced by using a digital camera, the period of the striped pattern may frequently become narrower than the scale of each character area, as shown in FIG. 20. As a result, a part of each character area belongs to the positive image area, and a part adjacent to the character area belongs to the negative image area. That is, one character area becomes a region divided into a positive region and a negative region (hereinafter referred to as a split region). Therefore, it becomes difficult to extract the character area as the concatenated area, and each character area cannot be subjected to OCR processing.

Therefore, by adjusting the reduction ratio, the cycle of the striped pattern (striped pattern) can be extended. As a result of the adjustment, as shown in FIG. 21, the character region can be obtained as a connected region in which the positive image region and the negative image region are not separated. As shown in FIG. 21, the area of the character "4" is a connecting area of the positive image area, and the area of the character "1" is the connecting area of the negative area, but the characters "2" and "3" are described above. It is a divisional area as explained.

Next, an enlarged image is generated by enlarging the reduced image at the enlargement ratio, which is the reciprocal of the reduction ratio. Then, the difference image generation process is performed so as to generate a difference image obtained by subtracting the visible image component from the enlarged image. FIG. 22 shows a difference image obtained by the difference image generation process. As a result, it becomes possible to perform a process of separating the background area and the character area in the difference image.

As described above, it has already been explained that the reduction process (thinning process) is performed when the invisible image hidden in the original image is revealed (visualized), but when the reduction process and the enlargement process are performed, the original image is used. It is necessary to provide a reference point (Px, Py) at a predetermined position in the image. The reference point is to be the origin of the spatial coordinates of the reduction process and the enlargement process. Then, by changing the position of the reference point, the connecting area associated with the striped pattern (striped pattern) can be changed, and the difference image that becomes the connecting area of the positive region for characters other than the character "4". It is thought that it will be possible to obtain.

Therefore, FIG. 23 shows a difference image decoded by changing the reference point and performing reduction processing. As shown in FIG. 23, the region "1" can be a connecting region of the positive region, and the region of the character "4" can be the connecting region of the negative region. The characters "2" and "3" are still divided regions.

Further, FIG. 24 shows a difference image decoded by resetting the reference point and performing reduction processing. As shown in FIG. 25, the regions of the letters "1" and "4" can be changed to the connecting regions of the positive regions, instead of the regions of the letters "1" and "4" being the split regions.

Further, FIG. 26 shows a difference image decoded by resetting the reference point and performing reduction processing. As shown in FIG. 27, the region "4" can be a connecting region of the positive region.

By extracting the concatenated area of the positive region from the above-decrypted multiple (4 images) difference images, all of the characters "1", "2", "3" and "4" are concatenated in the positive region. Character areas that have become areas can be combined (joined). The character area thus synthesized is shown in FIG. 28. Optical character recognition (OCR) can be easily performed for each character region shown in FIG. 28.

Here, the reference point, the reduction process, and the enlargement process will be supplemented with a description in principle. Generally, for reduction processing and enlargement processing, coordinates that allow only integers are set for the original image. Then, when performing the reduction process and the enlargement process, the central coordinates are defined as the reference points (Px, Py). The original image is set to a rectangular size having a horizontal width of Lx and a vertical width of Ly. The processing procedure includes (1) shifting the original image so that the origin of the spatial coordinates and the reference point coincide, and moving the original image (x, y) by (-Px, -Py), (2). ) Shrinking process (thinning process), (3) Enlarging process, (4) Interpolating process (processing to estimate and replenish the missing pixels by the thinning process from the adjacent pixel information), (5) Original position (5) An example of performing the process in steps (1) to (5), which is the process of returning to the original image (coordinate system), is shown.

First, the first reference point set as the initial value is set to (Px0, Py0).

In the embodiment of the present invention, the first reference point (Px0, Py0) is set to, for example, the position coordinates (Lx / 2, Ly / 2) at the center of the original image.

It is necessary to move the original image (x, y) by (-Px, -Py) before performing the reduction processing or the enlargement processing. Equation 1 shows an equation for converting such translation.

数１に示す座標変換を行うことによって、原画像（ｘ，ｙ）を（-Ｐｘ，-Ｐｙ）だけ移動することができる。

By performing the coordinate transformation shown in Equation 1, the original image (x, y) can be moved by (-Px, -Py).

Next, it is necessary to perform the reduction process. Here, the coordinates of the pixels before conversion are (x ₀ , y ₀ ), the coordinates after conversion are (x ₁ , y ₁ ), the magnification in the X-axis direction is Sx1, and the magnification in the Y-axis direction is Sy1. Then, the formula of the coordinate transformation by the reduction process can be shown as Equation 2. Since it is a reduction process, 0 <Sx1 <1 and 0 <Sy1 <1. The reduction processing direction (for example, the horizontal direction or the vertical direction) in the actual reduction processing is determined based on the direction of the image lines constituting the invisible image, as in the case of moving the reference point. Therefore, in order to decode the original image, it is not always necessary to reduce the original image in both the horizontal direction and the vertical direction. The same applies to the enlargement processing described later. If the invisible image (confidential information) is hidden in both the vertical direction and the horizontal direction, the invisible image (confidential information) in the vertical direction and the horizontal direction (both directions) may be decoded at the same time. Therefore, in order to selectively decode invisible images (confidential information) in the vertical direction and the horizontal direction (both directions), the reduction processing is performed so that the reduction processing direction is either the vertical direction or the horizontal direction. It is appropriate to do.

数２に示す座標変換を行うことによって、原点（０，０）を中心に、原画像（ｘ，ｙ）を縮小処理することができる。

By performing the coordinate transformation shown in Equation 2, the original image (x, y) can be reduced with the origin (0,0) at the center.

Here, as an example of the decoding method by the reduction process, a decoding method in which some pixels are thinned out from the original image will be described. The image reduced by the decoding method without interpolation processing is inevitably coarse. In order to alleviate such roughness, it is generally possible to adopt a reduction process accompanied by an interpolation process such as bilinear as described in the above-mentioned enlargement process. Therefore, in order to show the faithful reduced image to the observer, a reduction process (algorithm) accompanied by an interpolation process is often used. However, as in the embodiment of the present invention, when the reduction process for decoding the original image is performed and the interpolation process similar to the enlargement process of the image is performed, the invisible image (data) in the original image is displayed. It may be difficult to decrypt. Therefore, in order to decode an invisible image, a reduction process that does not involve interpolation processing is preferable. That is, the reduction process (simply, the thinning method) or the nearest neighbor method (a method of calculating the corresponding coordinates and adopting the nearest pixel) described in the embodiment of the present invention.

_{First, the coordinates x 1} and y ₁ of the pixel after the reduction conversion by the number 2 are not always integers, and those having a fraction after the decimal point are generated. The coordinates of such pixels are assumed to be undisplayable and are subject to thinning. The ratio of the pixels thinned out by the thinning process to the remaining pixels and the spacing between the pixels depend on the magnification Sx1 in the X-axis direction or the magnification Sy1 in the Y-axis direction and the reference point (Px, Py). Therefore, it should be noted that the size (number of pixels) of the reduced image after the reduction processing (thinning process) is smaller than the size (number of pixels) of the original image.

Next, the reduced image needs to be enlarged in order to appropriately generate the difference image. Here, the coordinates of the pixels before conversion are (x ₁ , y ₁ ), the coordinates after conversion are (x ₂ , y ₂ ), the magnification in the X-axis direction is Sx2, and the magnification in the Y-axis direction is Sy2. Then, the formula of the coordinate transformation by the enlargement processing can be shown as the equation 3. Since in order to return the difference image after reduction processing to the size of the original image (number of pixels), Sx2 = 1 / Sx1 ( Sx1 -1), and ^{Sy2 = 1 / Sy1 (Sy1 -1} ).

なお、図２１に示す縮小画像には、復号化された不可視画像と共に、デザイン化された原画像（「★」印のイメージ）が現れている。このような可視画像（領域Ｃ）は、ＯＣＲ処理を行う際、障害となる。

In the reduced image shown in FIG. 21, the designed original image (image marked with “★”) appears together with the decoded invisible image. Such a visible image (region C) becomes an obstacle when performing OCR processing.

Therefore, a process of subtracting the components of the original image from the enlarged image will be described. For that purpose, it is necessary to perform enlargement processing and interpolation processing so that the size (number of pixels) of the reduced image subjected to the reduction processing (thinning process) becomes the same as the size (number of pixels) of the original image.

The number of pixels of the reduced image is smaller than that of the original original image. Therefore, when trying to enlarge the reduced image, the enlarged image inevitably has a shortage of pixels as compared with the original image. Therefore, when enlarging a reduced image, a process of interpolating the missing pixels (hereinafter referred to as an interpolation process) is performed in order to estimate pixels that do not exist on the reduced image (hereinafter referred to as missing pixels) from peripheral pixels. ) Is required.

Here, as an example of the interpolation processing, a procedure for calculating the gradation data (luminance value) of the missing pixels by using the bilinear interpolation method is shown. The well-known bi-liner interpolation method is an interpolation method using four pixels around the missing pixel. FIG. 29 shows an example of the positional relationship between the missing pixel and the four pixels around it. The procedure for calculating the pixel value (luminance value) at the coordinates (Sx, Sy) of the missing pixel will be described below. First, the coordinates (Sx / a, Sy / a) are calculated by dividing the coordinates (Sx, Sy) of the missing pixels by the enlargement ratio a used in the enlargement processing. Next, the pixel values (luminance values) of the four pixels around (Sx / a, Sy / a) in the reduced image are acquired. That is, I (x, y), I (x + 1, y), I (x, y + 1), I (x + 1, y + 1) are acquired. Then, the distance between each of the surrounding four pixels and the coordinates (Sx / a, Sy / a) is calculated, and the weighting (numerical value of 0 to 1) corresponding to each distance is calculated. As for the weighting, it is preferable that the smaller the distance, the larger the weighting. Finally, the product of the pixel values (luminance values) of the surrounding four pixels and the weighting is added to estimate the pixel values (luminance values) of the insufficient pixels. The difference between the x-coordinate of the coordinates (Sx / a, Sy / a) and the x-coordinate of the coordinates (x, y) is Δx, and the y-coordinates and coordinates (x) of the coordinates (Sx / a, Sy / a). , Y) The difference from the y coordinate is defined as Δy. Then, the pixel value (luminance value) Is (Sx, Sy) of the insufficient pixel can be calculated as in Equation 4.

数４に示すような補間演算を行い、拡大処理後の画素数を、原画像の画素数と同じとなるように補間処理を行う。

The interpolation calculation as shown in Equation 4 is performed, and the interpolation processing is performed so that the number of pixels after the enlargement processing is the same as the number of pixels of the original image.

Then, after performing the reduction processing, the enlargement processing, and the interpolation processing, the reference point (Px, Py) of the original image (x, y) is reduced and enlarged from the origin (0, 0) to the original coordinates. In order to return to the system, the conversion to translate again is performed. The equation for performing such translation conversion is shown in Equation 5.

以上の一連の変換処理をまとめた式を数６に示す。

Equation 6 shows an equation summarizing the above series of conversion processes.

以上のように説明したように拡大処理及び補間処理を行った結果、元の画素数（サイズ）に戻された画像を取得する。そして、その拡大画像から原画像の成分を差し引く処理を行って、差分画像を生成する。

As a result of performing the enlargement processing and the interpolation processing as described above, the image restored to the original number of pixels (size) is acquired. Then, a process of subtracting the components of the original image from the enlarged image is performed to generate a difference image.

To supplement the reference points (Px, Py), if the values of x = Px and y = Py are substituted into the number 6, the converted coordinates (x ₄ , y ₄ ) = regardless of Sx1, Sy1, Sx2, Sy2. It is converted to (Px, Py). Since the reference point (Px, Py) is a fixed point, it is obvious that the gradation data (luminance value) of the original image existing at the reference point (Px, Py) is invariant.

Next, the labeling process after the difference image is generated will be described.

As a premise of the labeling process, it is necessary that the difference image is binarized. This is because in the binarized difference image, a pixel region (connected region) in which a black pixel region (or a white pixel region) is continuous is easily detected. In the embodiment of the present invention, for convenience of explanation, white pixels will be described as pixels in the background region, and black pixels will be described as pixels in the character region.

Here, a sample image of the binarized difference image is shown in FIG. In the binarized difference image, the process of allocating the same number to the connected area is called labeling. The numerical value assigned by the labeling process so as to correspond to the concatenated area is referred to as a label number. Then, a label area for storing the label number is prepared. Since each label number in the label area has a one-to-one correspondence with each pixel of the difference image to be labeled, the label number can be referred from the position of the pixel of the difference image.

First, before the labeling process, all the values (label numbers) in the label area are initialized to be 0 (zero).

Next, a method of assigning a label number in the labeling process will be described.

Here, the matching pattern used in the labeling process is shown in FIG. The matching pattern used for the labeling process in the embodiment of the present invention is a 3 × 3 matrix as shown in FIG. First, the center of the matching pattern corresponds to the pixel of interest to which the label number is assigned in the label area. Then, the pattern of the white and black pixels around the pixel of interest is determined, and the label number is determined.

Specifically, when the label numbers of the peripheral pixels on the upper left, directly above, upper right, and left are all 0 (zero) when viewed from the pixel of interest, the label number obtained by adding 1 to the last assigned number is assigned. .. Further, when the label number is assigned for the first time because there is no assigned number after the initialization, 1 is assigned to the label number of the label area corresponding to the pixel of interest (hereinafter referred to as the label number of the pixel of interest). It should be noted that the peripheral pixels on the upper right, directly below, upper left, and right when viewed from the pixel of interest are not involved in the labeling process (they are irrelevant). Further, when there are a plurality of label numbers already assigned to the peripheral pixels on the upper left, directly above, upper right, and left, the smallest label number among them is assigned as the label number of the pixel of interest.

In this way, while scanning the matching pattern over the entire image, labeling processing is performed on the pixels of interest in the matching pattern.

Here, an example of the labeling process according to the embodiment of the present invention will be shown, and the labeling process will be described.

First, FIG. 32 shows the initialized label area. As shown in FIG. 32, at the beginning of the labeling process, the matching pattern is located at the upper left of the label area. When the pixel of interest is in the first row of the difference image, the label number of the pixel of interest is not assigned because there are no peripheral pixels on the pixel of interest. During the labeling process, the matching pattern moves from left to right. Then, after reaching the right end, it moves down one line and moves toward the left end. The label numbers of the pixels of interest are assigned to the second and subsequent rows.

FIG. 33 shows how the first black pixel of interest was detected in the binarized difference image. As described above, since the label numbers of the peripheral pixels on the upper left, directly above, upper right, and left are all 0 (zero) when viewed from the pixel of interest, 1 can be assigned to the label number of the pixel of interest. FIG. 34 shows the state of the labeling process when the first black pixel of interest is detected. Further, as the matching pattern is scanned, as shown in FIG. 35, the second black pixel of interest is detected.

In this case, since the label number 1 already assigned to the peripheral pixel on the upper right is included, 1 is assigned to the label number of the pixel of interest as shown in FIG. 36. Then, in the same manner, the label number 1 is assigned to the five places in the label area.

Further, as the matching pattern is scanned, as shown in FIG. 37, the seventh black pixel of interest is found. The label numbers of the peripheral pixels on the upper left, directly above, upper right, and left are all 0 (zero) when viewed from the pixel of interest. However, since the label number already assigned is 1, the label number of 2 (= 1 + 1) is assigned to the label number of the pixel of interest. Then, in the same manner, 2 is assigned as a label number to two places in the label area. FIG. 38 shows the labeling process when the 7th black pixel of interest is detected.

Further, as the matching pattern is scanned, as shown in FIG. 39, the 14th black pixel in which the label numbers of the peripheral pixels on the upper left, directly above, upper right, and left are all 0 (zero) when viewed from the pixel of interest. Is detected. Here, since the label number assigned last is 2, as shown in FIG. 40, the label number of 3 (= 2 + 1) is assigned to the label number of the pixel of interest. By performing such scanning, labeling processing is performed on all the difference screens.

In the binarized difference image according to the embodiment of the present invention, FIG. 41 shows how the matching pattern reaches the lower left and the scanning is completed. After the scanning is completed, a label number is temporarily assigned to the label area as shown in FIG. 42. Then, it is determined whether or not an appropriate label number is assigned in the label area. If it is determined to be inappropriate, correct the label number. For example, the label number 3 in the 6th row and the 2nd column in the label area is adjacent to the concatenated area of the label number 1. Therefore, as shown in FIG. 43, the label number in the 6th row and 2nd column in the label area should be corrected from 3 to 1.

In order to correct the label number by the labeling process as described above, it is preferable to prepare a look-up table (hereinafter referred to as LUT) as shown in FIG. 44. When a new label number is generated during the labeling process, the new label number is registered in the LUT. Then, when the label number needs to be corrected, the corrected label number may be re-registered.

Next, the process of separating the background image and the character area in the difference image will be described.

In the embodiment of the present invention, if a certain character area can be separated from the difference image, it is necessary to move the reference point (Px, Py) in order to generate a difference image capable of extracting another character area.

Therefore, how to move the reference point will be described. The moving direction of the reference point will be described.

First, whether to move the reference point (Px, Py) in the X-axis direction (horizontal direction) or in the Y-axis direction (vertical direction) is determined based on the direction of the image lines constituting the invisible image. do. When the invisible image is decoded in the X-axis direction, the reference point is shifted in the X-axis direction (horizontal direction) and the thinning process is performed. Further, when the invisible image is decoded in the Y-axis direction, the reference point is shifted in the Y-axis direction (vertical direction) and the thinning process is performed. Further, the reference points (Px, Py) may be shifted along the positive (plus) direction of the coordinate axes or may be shifted along the negative (minus) direction, and can be set arbitrarily. The reference point (Px, Py) is determined to be shifted in a certain direction. In the embodiment of the present invention, it is set to shift in the positive (plus) direction of the X-axis or the Y-axis.

In the embodiment of the present invention, the first reference point (Px0, Py0) is set to, for example, the position coordinates (Lx / 2, Ly / 2) at the center of the original image. The minimum amount of movement of the reference point (Px, Py) is set to one pixel. Then, the reference points (Px, Py) are usually shifted in units of one pixel. The reason for such a setting is that the striped pattern (striped pattern) of the reduced image changes significantly even when the reference point is deviated by one pixel.

Specifically, an example of shifting the reference point in the X-axis direction is shown. First, the first reference point (Px, Py) = (Px0, Py0). The next reference point (Px, Py) = (Px0 + 1, Py0) and the next reference point (Px, Py) = (Px + 2, Py0) are moved. Further, an example in which the reference point is shifted in the Y-axis direction is shown. Assuming that the first reference point (Px, Py) = (Px0, Py0), the next reference point (Px, Py) = (Px0, Py0 + 1), the next reference point (Px, Py) = (Px0, Py0 + 2) I will move it. The character area is extracted from the difference image generated by the series of processes as described above.

In this way, while shifting the reference points (Px, Py), the characters are extracted for the specified number of digits, or the process is repeated until a predetermined number of difference images are generated. Then, the character areas extracted from the generated difference image are combined (joined) to generate image information. By performing OCR processing on the combined image information, it is possible to authenticate the information of the invisible image in the print area.

Next, the authentication system of the present invention uses a digital camera to photograph a printed area on which a hidden image or hidden information is printed, decodes a character area of an invisible image, and performs OCR processing. (Flow) will be described with reference to FIG. 45.

The authentication system of the present invention can perform processing for separating the background area and the character area for each character of the invisible image in the print area. Therefore, the authentication system of the present invention can generate at least a number of difference images corresponding to a predetermined number of characters, and sets a predetermined number of characters as the maximum number of difference images. The difference image is an image obtained by subtracting the original image components as described above.

In particular, when one character area is divided into a positive image and a negative image by the reduction process based on the initially set reference point, the reference point is set until one character area becomes a connecting area. It can be changed (reset). An upper limit may be set for the number of times the reference point is reset, and for example, it may be set based on a predetermined number of characters.

First, regarding the character information in the print area, for example, the character size, the character spacing, the number of specified columns to be read, the number of lines, the number of characters per line, etc., the horizontal reduction ratio, the vertical reduction ratio, and the maximum number of sheets for creating a difference image. (Hereinafter, the maximum number of differential images to be created is used.) And the like are read and initialized (step S1).

Next, using a digital camera, the invisible image and the print area on which the visible image is printed are photographed (step S2). For shooting, adjust the positional relationship between the print area and the digital camera so that the direction of the pixel arrangement of the digital camera and the direction of each image line forming the latent image portion and the background portion match. Is desirable. However, it is difficult to make it a perfect match. For example, the observer can approach the desired positional relationship by adjusting the direction so that the distance between the positive image of the invisible image to be visually recognized and the striped pattern caused by the negative image is widened.

Next, the original image is reduced (thinned out) at the current reference point, and the reduced image is acquired at a predetermined reduction rate (step S3). Further, the reduced image is enlarged at the enlargement ratio, which is the reciprocal of the reduction ratio, and the enlarged image subjected to the interpolation processing is acquired (step S4). Then, a difference image obtained by subtracting the original image from the enlarged image is generated (step S5).

Next, labeling processing is performed so that the connected areas can be identified by assigning a number to each of the extracted connected areas (step S6). Further, by the labeling process, in addition to the identification of the connected area, the character size (width, height, area (number of pixels) of the character) of the connected area can be acquired.

Then, a process of separating the background area and the character area in the difference image is performed based on the character size (step S7).

Subsequently, a process of moving the current reference point is performed, and preparations for the next process are performed (step S8).

Next, it is determined whether or not the specified number of digits (for example, the number of character strings for which reading is set in advance) has been reached (step S9). If the determination in step S9 is No, the process proceeds to step S10, which will be described later. If the determination in step S9 is Yes, the process proceeds to step S11 described later.

Next, it is determined whether or not the number of generated difference images has reached the set maximum number of difference image creations (step S10). If the determination in step S10 is No, the process returns to step S3 and the process of step S3 is performed again.

Then, if the determination in step S10 is Yes, a process of synthesizing (connecting) character areas capable of OCR processing is performed (step S11).

Then, the character area synthesized (joined) from all the difference images and the character pattern corresponding to each character are sequentially collated (matched). Based on the collation result, OCR processing is performed by selecting the optimum character pattern for each character area (step S12).

It should be noted that the above-mentioned embodiments of the present invention merely show examples of embodiment in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner by these. be. That is, the present invention can be implemented in various forms without departing from the technical idea or its main features.

Further, the image line used in the embodiment of the present invention has a minimum unit area (unit). The width of the minimum unit region is determined by the vertical dimension Sv or the horizontal dimension Sh, and a size of 1 mm or less is preferable, for example, 340 μm.

Further, in the embodiment of the present invention, a CCD line sensor camera, a CCD area sensor camera, a frame transfer type CCD image sensor, a full frame transfer type CCD image sensor, or the like may be used as means for photographing the printed area.

Further, in the above-described embodiment of the present invention, it is described that bilinear interpolation (bilinear interpolation) is adopted when interpolation processing is required due to the enlargement processing, but another interpolation processing method is adopted. be able to. For example, nearest neighbor interpolation (nearest neighbor), bicubic interpolation (bicubic interpolation), or the like may be adopted. It should be noted that the interpolation processing method in which the invisible image cannot be restored or decoded and the encrypted hidden image or hidden information is lost cannot be adopted in the present invention.

Information including parameters such as processing procedures, control procedures, specific names, registered data of each processing or search conditions, screen examples, or database configurations shown in the specifications and drawings are not specified unless otherwise specified. It can be changed arbitrarily.

Further, with respect to the authentication system 10 of the present invention, each component shown in the figure is a functional concept and does not necessarily have to be physically configured as shown in the figure. For example, with respect to the processing functions provided in each device of the authentication system 10, particularly each processing function performed in the authentication terminal 2, all or any part thereof is interpreted and executed by the CPU and the program. , May be realized.

The program is recorded on a non-temporary computer-readable recording medium including a programmed instruction for causing the computer to execute the method according to the present invention, which will be described later, and the authentication terminal 2 is required. Is read mechanically. That is, a computer program for giving instructions to the CPU in cooperation with the OS (Operating System) and performing various processes is recorded in a storage unit 2b or the like such as a ROM or an HDD. This computer program is executed by being loaded into RAM, and cooperates with the CPU to form a control unit.

Further, this computer program may be stored in the application program server connected to the authentication terminal 2 via an arbitrary network, and all or a part thereof can be downloaded as needed. Is.

Further, the program according to the present invention may be stored in a computer-readable recording medium, or may be configured as a program product. Here, the "recording medium" includes a memory card, a USB memory, an SD card, a flexible disk, a magneto-optical disk, a ROM, an EPROM, an EEPROM, a CD-ROM, a MO, a DVD, and a Blu-ray (registered trademark). It shall include any "portable physical medium" such as a disk.

Further, the "program" is a data processing method described in any language or description method, regardless of the format such as source code or binary code. The "program" is not necessarily limited to a single program, but is distributed as multiple modules or libraries, or cooperates with a separate program represented by the OS to achieve its function. Including things. A well-known configuration or procedure can be used for a specific configuration, a reading procedure, an installation procedure after reading, and the like for reading a recording medium in each device shown in the embodiment of the present invention.

Further, the authentication terminal 2 may be configured as an information processing device such as a known personal computer, or may be configured by connecting an arbitrary peripheral device to the information processing device. Further, the authentication terminal 2 may be realized by mounting software (including a program, data, etc.) that realizes the method of the present invention on the information processing apparatus.

Further, the specific form of distribution / integration of the device is not limited to the one shown in the figure, and all or part of the device may be functionally or physically in an arbitrary unit according to various additions or functional loads. It can be configured in a distributed and integrated manner. That is, the above-described embodiments may be arbitrarily combined and implemented, or the embodiments may be selectively implemented.

As described above, the hidden image or the authentication system for certifying the hidden information, the authentication method and the authentication program of the present invention are included in the images such as photographs, videos, digital clocks, electric bulletin boards, signboards, calculators or handwritten mark sheets. When recognizing numbers and characters, noise can be removed, and by specifying the display area of numbers and characters, the amount of calculation can be reduced and the processing speed can be increased. Image processing devices using the authentication system of the present invention, date identification devices, image processing methods using the authentication method of the present invention, and authentication programs of the present invention are used in many industrial fields, especially scanners or cameras. It can be carried out in the field of image processing that handles read images, and is extremely useful.

1 Image capture device 2 Authentication terminal 2a Control unit 2b Storage unit 2c Display unit 3 Image pickup unit 4 Lighting unit 5 Interface unit 6 Housing unit 7 Subject 8 Lenticular lens 10 Authentication system 101 Image reader 102 Authentication terminal 103 Image pickup unit 104 Illumination section 105 Halftone dot printed matter A, A'Image B, B'Image C Image D Image line L1, L2, L3, L4 Line Sv Vertical dimension Sh Horizontal dimension

Claims (23)

Image capture for capturing a printed matter in which a print area composed of a visible area on which visible information or a visible image is printed and an invisible area consisting of a latent image portion and a background portion on which a hidden image or hidden information is printed is arranged. An authentication system including a unit and an authentication terminal for authenticating the hidden image or the hidden information.
The image capturing unit includes a lighting unit that irradiates a printed matter with light, and an imaging unit that photographs the printed matter and acquires an original image of the printed area.
The authentication terminal is provided with a predetermined pixel in the captured image as a reference point, and the original image is reduced at a predetermined reduction rate with the reference point as a reference to generate a reduced image.
With the reference point as a reference, the reduced image is enlarged at an enlargement ratio that is the reciprocal of the reduction ratio, and interpolation processing that is the same as the number of pixels of the original image is performed to generate an enlarged image.
The calculation of subtracting the luminance value of each pixel of the original image from the luminance value of each pixel of the enlarged image is performed to generate the difference image data.
The background area and the character area are separated from the difference image data, and the background area and the character area are separated.
A process of shifting the reference point in a predetermined direction on a pixel-by-pixel basis is performed.
An authentication system characterized by collating the character area extracted from the difference image data with a character pattern, performing OCR, and authenticating the concealed image or the concealed information. Image capture for capturing a printed matter in which a print area composed of a visible area on which visible information or a visible image is printed and an invisible area consisting of a latent image portion and a background portion on which a hidden image or hidden information is printed is arranged. An authentication system including a unit and an authentication terminal for authenticating the hidden image or the hidden information.
The image capturing unit includes a lighting unit that irradiates a printed matter with light, and an imaging unit that photographs the printed matter and acquires an original image of the printed area.
The authentication terminal is provided with a predetermined pixel in the captured image as a reference point, and the original image is reduced at a predetermined reduction rate with the reference point as a reference to generate a reduced image.
With the reference point as a reference, the reduced image is enlarged at an enlargement ratio that is the reciprocal of the reduction ratio, and interpolation processing that is the same as the number of pixels of the original image is performed to generate an enlarged image.
The calculation of subtracting the luminance value of each pixel of the original image from the luminance value of each pixel of the enlarged image is performed to generate the difference image data.
By labeling the difference image data, a label number is generated.
The label number is stored in the label area so that a one-to-one correspondence with the difference image data can be attached.
Based on the label number, the background area and the character area are separated from the difference image data.
A process of shifting the reference point in a predetermined direction on a pixel-by-pixel basis is performed.
An authentication system characterized by collating the character area extracted from the difference image data with a character pattern, performing OCR, and authenticating the concealed image or the concealed information. A plurality of minimum unit areas having a predetermined area are arranged at a predetermined pitch in the print area.
In the minimum unit region, a first image line, a second image line, and a third image line are arranged at the predetermined pitch.
The third image line is arranged in a region where the first image line and the second image line do not exist.
The latent image portion is composed of the first image line, the background portion is composed of the second image line, and the visible region is composed of the third image line.
The first stroke, the second stroke, and the third stroke are arranged so as to be parallel to each other in a linear region.
When one of the first image and the second image is optically on, the other is off, or the brightness value of the first image and the brightness of the second image. There is a complementary relationship so that the sum of the values is the predetermined brightness value.
The authentication system according to claim 1 or 2, wherein a positive image is formed by the latent image portion, and a negative image of the latent image portion is formed by the background portion. The authentication system according to claim 3, wherein the width of the minimum unit area is 1 mm or less. The authentication system according to any one of claims 1 to 4, wherein the area of the first image line and the area of the second image line are the same or substantially the same. The authentication system according to any one of claims 1 to 5, wherein the reference point is a pixel whose luminance value or gradation data does not change before and after the reduction process. The authentication system according to any one of claims 1 to 6, wherein the printed matter is provided with the concealed image or the concealed information by a halftone dot configuration having a pattern composed of periodically arranged dots. The authentication system according to any one of claims 1 to 7, wherein the hidden information is a QR code (registered trademark) that cannot be recognized by the naked eye. The secret image is embedded in the invisible area,
When the pixel of the secret image is black, it is converted into the first checker pattern of 2 rows and 2 columns.
When the pixel of the secret image is white, it is converted into a second checkered pattern having two rows and two columns in which the first checker pattern and black and white are inverted, and the hidden image is converted into any one of claims 1 to 8. The authentication system described in. Claims 1 to 2 for collating the information read by the IC reader / writer from the IC chip embedded in the printed matter with the hidden information acquired based on the character area by the OCR to determine the authenticity of the printed matter. The authentication system according to any one of 9. The authentication system according to any one of claims 1 to 10, wherein the imaging unit is a CCD line sensor camera or a CCD area sensor camera. An image capture unit in a printed matter in which a print area composed of a visible area on which visible information or a visible image is printed and an invisible area consisting of a latent image portion and a background portion on which a hidden image or hidden information is printed is arranged. And an authentication method for authenticating the hidden image or the hidden information by using an authentication system provided with an authentication terminal.
A step of photographing the printed matter using the image capturing unit and acquiring an original image of the printed area, and a step of acquiring the original image.
Using the authentication terminal, a predetermined pixel in the captured image is provided as a reference point, and the original image is reduced at a predetermined reduction rate with the reference point as a reference to generate a reduced image.
Using the authentication terminal, the reduced image is enlarged with the enlargement ratio, which is the reciprocal of the reduction ratio, with the reference point as a reference, and interpolation processing is performed so as to be the same as the number of pixels of the original image. And the steps to generate
Using the authentication terminal, a step of subtracting the luminance value of each pixel of the original image from the luminance value of each pixel of the enlarged image to generate differential image data.
A step of separating a character area and a background area other than the character area from the difference image data by using the authentication terminal.
Using the authentication terminal, the step of shifting the reference point in a predetermined direction on a pixel-by-pixel basis,
Using the authentication terminal, the step of collating the character area extracted from the difference image data with the character pattern and performing OCR, and
A step of authenticating the hidden image or the hidden information based on the result of the OCR using the authentication terminal.
An authentication method characterized by consisting of. An image capture unit in a printed matter in which a print area composed of a visible area on which visible information or a visible image is printed and an invisible area consisting of a latent image portion and a background portion on which a hidden image or hidden information is printed is arranged. And an authentication method for authenticating the hidden image or the hidden information by using an authentication system provided with an authentication terminal.
A step of photographing the printed matter using the image capturing unit and acquiring an original image of the printed area, and a step of acquiring the original image.
Using the authentication terminal, a predetermined pixel in the captured image is provided as a reference point, and the original image is reduced at a predetermined reduction rate with the reference point as a reference to generate a reduced image.
Using the authentication terminal, the reduced image is enlarged with the enlargement ratio, which is the reciprocal of the reduction ratio, with the reference point as a reference, and interpolation processing is performed so as to be the same as the number of pixels of the original image. And the steps to generate
Using the authentication terminal, a step of subtracting the luminance value of each pixel of the original image from the luminance value of each pixel of the enlarged image to generate differential image data.
A step of generating a label number by labeling the difference image data using the authentication terminal, and
Using the authentication terminal, a step of storing the label number in the label area so that a one-to-one correspondence with the difference image data can be attached.
A step of separating a character area and a background area other than the character area from the difference image data based on the label number using the authentication terminal.
Using the authentication terminal, the step of shifting the reference point in a predetermined direction on a pixel-by-pixel basis,
Using the authentication terminal, the step of collating the character area extracted from the difference image data with the character pattern and performing OCR, and
A step of authenticating the hidden image or the hidden information based on the result of the OCR using the authentication terminal.
An authentication method characterized by consisting of. A plurality of minimum unit areas having a predetermined area are arranged at a predetermined pitch in the print area.
In the minimum unit region, a first image line, a second image line, and a third image line are arranged at the predetermined pitch.
The third image line is arranged in a region where the first image line and the second image line do not exist.
The latent image portion is composed of the first image line, the background portion is composed of the second image line, and the visible region is composed of the third image line.
The first stroke, the second stroke, and the third stroke are arranged so as to be parallel to each other in a linear region.
When one of the first image and the second image is optically on, the other is off, or the brightness value of the first image and the brightness of the second image. There is a complementary relationship so that the sum of the values is the predetermined brightness value.
The authentication method according to claim 12 or 13, wherein a positive image is formed by the latent image portion, and a negative image of the latent image portion is formed by the background portion. The authentication method according to claim 14, wherein the width of the minimum unit area is 1 mm or less. The authentication method according to claim 14 or 15, wherein the area of the first image line and the area of the second image line are the same or substantially the same. The authentication method according to any one of claims 12 to 16, wherein the reference point is a pixel whose luminance value or gradation data does not change before and after the reduction process. The authentication method according to any one of claims 12 to 17, wherein the printed matter is provided with the concealed image or the concealed information by a halftone dot configuration having a pattern composed of periodically arranged dots. The authentication method according to any one of claims 12 to 18, wherein the hidden information is a QR code (registered trademark) that cannot be recognized by the naked eye. The secret image is embedded in the invisible area,
When the pixel of the secret image is black, it is converted into the first checker pattern of 2 rows and 2 columns.
When the pixel of the secret image is white, it is converted into a second checkered pattern having two rows and two columns in which the first checker pattern and black and white are inverted, and the hidden image is converted into any of claims 12 to 19. The authentication method described in. Claims 12 to 12 to collate the information read by the IC reader / writer from the IC chip embedded in the printed matter with the hidden information acquired based on the character area by the OCR to determine the authenticity of the printed matter. The authentication method according to any one of 20. In a printed matter in which a printed matter composed of a visible area on which visible information or a visible image is printed and an invisible area consisting of a latent image portion and a background portion on which a hidden image or hidden information is printed is arranged, the hidden image or the hidden image or An authentication program for causing a computer to authenticate the hidden information.
The step of photographing the printed matter and acquiring the original image of the printed area, and
A step of providing a predetermined pixel in the captured image as a reference point, reducing the original image at a predetermined reduction rate with the reference point as a reference, and generating a reduced image.
With the reference point as a reference, the reduced image is enlarged at an enlargement ratio that is the reciprocal of the reduction ratio, and interpolation processing is performed to be the same as the number of pixels of the original image to generate an enlarged image.
A step of generating differential image data by performing an operation of subtracting the luminance value of each pixel of the original image from the luminance value of each pixel of the enlarged image.
A step of separating a character area and a background area other than the character area from the difference image data,
A step of shifting the reference point in a predetermined direction on a pixel-by-pixel basis,
The step of collating the character area extracted from the difference image data with the character pattern and performing OCR, and
A step of authenticating the hidden image or the hidden information based on the result of the OCR, and
An authentication program characterized by consisting of. In a printed matter in which a printed matter composed of a visible area on which visible information or a visible image is printed and an invisible area consisting of a latent image portion and a background portion on which a hidden image or hidden information is printed is arranged, the hidden image or the hidden image or An authentication program for causing a computer to authenticate the hidden information.
The step of photographing the printed matter and acquiring the original image of the printed area, and
A step of providing a predetermined pixel in the captured image as a reference point, reducing the original image at a predetermined reduction rate with the reference point as a reference, and generating a reduced image.
A step of enlarging the reduced image at an enlargement ratio that is the reciprocal of the reduction ratio with the reference point as a reference, and performing interpolation processing that is the same as the number of pixels of the original image to generate an enlarged image.
A step of generating differential image data by performing an operation of subtracting the luminance value of each pixel of the original image from the luminance value of each pixel of the enlarged image.
A step of generating a label number by labeling the difference image data, and
A step of storing the label number in the label area so that a one-to-one correspondence with the difference image data can be attached.
A step of separating a character area and a background area other than the character area from the difference image data based on the label number, and
A step of shifting the reference point in a predetermined direction on a pixel-by-pixel basis,
The step of collating the character area extracted from the difference image data with the character pattern and performing OCR, and
A step of authenticating the hidden image or the hidden information based on the result of the OCR, and
An authentication program characterized by consisting of.

Images