Latent image generation device, latent image decorder, latent image generation program and latent image decoding program

Abstract

To provide a more sophisticated latent image that cannot be easily discerned by forgers in order to overcome the problem that the latent images related to conventional technology are based on the premise that they can be recognized by observers, and they can also be easily recognized by forgers attempting to counterfeit, however, in the case of printed materials such as banknotes and passports, the anti-counterfeiting technology of embedding latent images in reflective surfaces is insufficient, and there is a need to generate more sophisticated latent images that cannot be easily discerned by the forgers.SOLUTION: The image generation device related to the present disclosure includes: a primary coding unit (110) that performs coding on latent image characters that a user wants to make latent; an imaging unit (120) that performs imaging on a result coded by the primary coding unit (110); a dispersion unit (130) that disperses and arranges imaged information obtained by the imaging unit (120) into multiple pieces; and a latent image forming unit (140) that converts, into a latent image, an image dispersedly arranged with pieces obtained by the dispersing unit (130).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The disclosed technology relates to a latent image generation device, a latent image decoding device, a latent image generation program, and a latent image decoding program.

Background Art

[0002] Techniques for embedding latent images in product vouchers, tickets, stock certificates, etc. are known for the purpose of anti-counterfeiting, anti-unauthorized copying, decoration, etc.

[0003] Various forms of latent images are conceivable. For example, techniques are known in which a reflective surface is provided on a printed matter such as a product voucher, a ticket, or a stock certificate, and a latent image is embedded in this reflective surface. These latent images are made visible and recognized by the observer by changing the angle of the reflective surface of the reflector.

[0004] For example, Patent Document 1 discloses a technique in which a plurality of types of latent images each composed of fine ten-thousand lines with an uneven cross-section are formed on a reflective surface with different angles for each latent image, so that a plurality of types of latent images having an overlap in at least a part can be embedded. By changing the angle of the ten-thousand lines, a difference occurs between the amount of decrease in the luminance of incident light caused by the ten-thousand lines formed at one angle and the amount of decrease in the luminance of incident light caused by the ten-thousand lines formed at another angle. As a result, when observing the reflective surface at a certain angle, only a predetermined ten-thousand lines can be made visible and recognized, so that a reflector capable of making each of a plurality of types of latent images visible and recognized by changing the observation angle is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] The latent image exemplified in Patent Document 1 is premised on being recognized by an observer and can also be easily recognized by a forger who is attempting forgery. However, in the case of printed matter such as banknotes, passports, and securities, due to their nature, they are required to be difficult to forge or alter. Therefore, the anti-forgery technology of embedding a latent image on a reflective surface alone is not sufficient, and it is required to generate a more sophisticated latent image that cannot be easily perceived by a forger.

[0007] In view of the above problems, the disclosed technology aims to realize printing and reading of banknotes, passports, securities, certificates, and other important documents that are difficult for a forger to easily perceive the existence of a latent image, and even if the existence of the latent image is perceived, it is difficult to reproduce and has a high forgery deterrence effect.

MEANS FOR SOLVING THE PROBLEMS

[0008] A latent image generation device according to the disclosed technology includes a primary encryption unit that encrypts a latent image character that a user wants to make latent, an imaging unit that forms an image of the result encrypted by the primary encryption unit, a dispersion unit that disperses and arranges the imaged information obtained by the imaging unit into a plurality of pieces, and a latent image conversion unit that converts the image in which the pieces obtained by the dispersion unit are dispersed and arranged into a latent image.

EFFECTS OF THE INVENTION

[0009] Since the latent image generation device according to the disclosed technology has the above configuration, it is possible to realize printing of banknotes, passports, securities, certificates, and other important documents with a high forgery deterrence effect.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0011] (Embodiment 1) FIG. 1 is a block diagram showing the functional configurations of the latent image generation device 100 and the latent image decoding device 400 according to Embodiment 1. As shown in FIG. 1, the latent image generation device 100 according to Embodiment 1 includes a primary encryption unit 110, an imaging unit 120, a decentralization unit 130, and a latent image formation unit 140. As shown in FIG. 1, the latent image decoding device 400 according to Embodiment 1 includes a primary decryption unit 410, a character conversion unit 420, a combination unit 430, and an exposure unit 440. As shown in FIG. 1, a printing machine 200 may be connected to the latent image generation device 100 at the subsequent stage. Also, a reader 300 may be connected to the latent image decoding device 400 at the preceding stage.

[0012] 《Primary Encryption Unit 110 Constituting the Latent Image Generation Device 100》 The primary encryption unit 110 that constitutes the latent image generation device 100 encrypts the character information that the user wants to make latent (hereinafter referred to as "latent image character string" or "latent image character"). Specifically, the encryption performed by the primary encryption unit 110 may use classical encryption such as shift cipher, substitution cipher, and encryption using a hash function.

[0013] The shift cipher is a method of creating a ciphertext by determining a number in advance and shifting characters by that number.

[0014] The substitution cipher is a method of creating a ciphertext according to a table (referred to as a "substitution table" in this specification) that shows the correspondence between characters before encryption and characters after encryption in advance.

[0015] Specifically, the shift encryption is as follows. Suppose the latent image character string to be encrypted is, for example, the fictional name "Tokkyo Taro". If a shift number of 3 is determined for this latent image character string and a shift cipher is performed, the result of encryption is "Wrnnbr Wdur". For example, the first character "T" of the latent image character string is shifted 3 times, so T → U → V → W, and thus it becomes "W". Here, considering that the alphabet circulates in the "y" in the latent image character string, y → z → a → b, so it becomes "b".

[0016] The shift cipher can also be applied to a character string represented by Chinese characters, hiragana, katakana, or a combination thereof. Suppose the character string to be encrypted is, for example, "Patent Taro". In this case where the character string to be encrypted is in full-width, each character in the character string may be converted into a character code such as JIS code. When the character string to be encrypted is "Patent Taro", the conversion result to JIS code is "17987,13686,9279,9325,9254". Therefore, in the case of such a full-width character string, the primary encryption unit 110 may perform shift encryption on the result of conversion to JIS code.

[0017] Suppose the string to be encrypted is, for example, the half-width katakana "TOKYO HANAKO". When the string to be encrypted is in half-width, each character in the string may be converted into a character code such as ASCII code. When the string to be encrypted is the half-width katakana "TOKYO HANAKO", the conversion result to ASCII code is "196,175,183,174,202,197,186". Therefore, in the case of such a half-width string, the primary encryption unit 110 may perform shift encryption on the result of conversion to ASCII code. Note that the conversion method of the string to be encrypted is not limited to the character code described above, and other standardized character codes such as Unicode and UTF-8, or a character code arbitrarily created by the user may be used.

[0018] FIG. 2 is a diagram showing an example of a transposition table for alphabets. The transposition table is composed of an upper row and a lower row, and represents that by encrypting the characters in the upper row, they are transposed to the lower row. For example, in FIG. 2, when encrypting the upper "a", it is transposed to the lower "y". When the string to be encrypted is the aforementioned "Tokkyo Taro", the result of transposition encryption using the transposition table in FIG. 2 is "Hlmmbl Hyil".

[0019] A hash function is a function that calculates a value within a predetermined range for data such as a string or an image. A hash function is classified as a deterministic algorithm and always outputs the same value when the same data is input. The output value when data is input to a hash function is referred to as the hash value of that data. In the technical field of cryptography as well, a hash function is an effective means. To distinguish it from a general hash function, the hash function used in the technical field of cryptography is referred to as a "cryptographic hash function". Generally, a cryptographic hash function is required to have features such as a fixed output size, one-wayness, and collision resistance. One-wayness is sometimes referred to as preimage resistance. Collision resistance is a property that the problem of "find any two different data with the same hash value" cannot be easily solved.

[0020] The primary encryption unit 110 that constitutes the latent image generation device 100 may use a cryptographic hash function. The cryptographic hash function used by the primary encryption unit 110 may be a standardized one such as SHA-2 or SHA-3 (SHA is the initial letter of Secure Hash Algorithm), or it may be one created independently. Hereinafter, in the present invention, a general hash function and a "cryptographic hash function" will be collectively referred to as a "hash function" for explanation.

[0021] 《Image forming unit 120 that constitutes the latent image generation device 100》

[0020] The image forming unit 120 that constitutes the latent image generation device 100 performs image formation on the result encrypted by the primary encryption unit 110. Specifically, the image formation performed by the image forming unit 120 may be based on existing standards such as barcodes, two-dimensional codes, or Braille, or may be based on rules created as appropriate according to the scene where the user applies the latent image generation device 100.

[0022] FIG. 3 is an explanatory diagram showing a processing example of the primary encryption unit 110 and the image forming unit 120 of the latent image generation device 100 according to Embodiment 1. More specifically, FIG. 3 shows a processing example when the latent character string is "Tokkyo Taro", the primary encryption unit 110 performs transposition encryption based on the transposition table shown in FIG. 2, and the image forming unit 120 performs two-dimensional code formation.

[0023] 《Decentralization unit 130 that constitutes the latent image generation device 100》 The decentralization unit 130 that constitutes the latent image generation device 100 is, simply speaking, a component that disperses and arranges the imaged information obtained by the image forming unit 120 in a picture field (hereinafter referred to as "picture field (PF)") based on rules.

[0024] FIG. 4 is an explanatory diagram showing a processing example of the decentralization unit 130 of the latent image generation apparatus 100 according to Embodiment 1. FIG. 4 exemplifies a two-dimensional code as the input to the decentralization unit 130. The two-dimensional code shown in FIG. 4 is the same as the two-dimensional code output from the imaging unit 120 shown in FIG. 3. As shown in FIG. 4, image information (e.g., a two-dimensional code or the like) imaged by the imaging unit 120 is input to the decentralization unit 130.

[0025] The decentralization unit 130 first divides the input image information into a plurality of regions. This process performed by the decentralization unit 130 is to divide the input image as if it were the pieces of a jigsaw puzzle. In FIG. 4, a state is shown in which the decentralization unit 130 divides the two-dimensional code image into four pieces A, B, C, and D. Note that in FIG. 4, the image is divided into four rectangular pieces, but the disclosed technology is not limited to this. The division into a plurality of pieces performed by the decentralization unit 130 may be a division into a number of pieces other than four, or may be a division into pieces having a shape other than a rectangle.

[0026] Next, the decentralization unit 130 disperses and arranges each of the divided pieces into an image field (PF) based on a rule. In FIG. 4, the image field (PF) is the portion indicated by the symbol “PF”. Information on where to place each piece in the image field (PF) (hereinafter referred to as “piece placement information”) is a parameter that can be freely determined by the user. The piece placement information has the meaning of an encryption key. Here, the encryption key refers to information that the user determines how to place the pieces, and the user cannot restore it without knowing this information. The piece placement information is shared with the integration unit 430 of the latent image decoding apparatus 400 described later.

[0027] The rule for splitting performed by the dispersion unit 130 may be to simply translate each piece as it is and disperse and arrange it in the image field (PF), but it is preferable to perform more complex processing. Specifically, the dispersion unit 130 may perform a primary transformation such as rotation, enlargement or reduction, symmetry, etc. on each piece and then disperse and arrange it in the image field (PF). For example, the piece B in FIG. 4 has been transformed by being enlarged and rotated 90 degrees clockwise. The piece C in FIG. 4 has been transformed by line symmetry.

[0028] In the image field (PF) of FIG. 4, letters A to D are shown in each piece. However, in order to explain the primary transformation such as rotation, enlargement or reduction, symmetry, etc. performed on each piece, the letters attached in the image field (PF) are also schematically shown as being rotated, enlarged or reduced, or symmetric. For example, the letter "P" attached to the piece B is shown as being rotated 90 degrees clockwise. In this specification, it is assumed that the piece arrangement information also includes the information of this primary transformation. Note that the primary transformation can be realized by multiplying a transformation matrix.

[0029] 《Latent Image Generation Unit 140 Constituting the Latent Image Generation Apparatus 100》 Briefly speaking, the latent image generation unit 140 constituting the latent image generation apparatus 100 is a component that changes the image in which the pieces obtained by the dispersion unit 130 are dispersed and arranged into a latent image. As shown in FIG. 1, in addition to the image generated by the dispersion unit 130, a "positive moving image" is input to the latent image generation unit 140. In this specification, the positive moving image means an image that exhibits a camouflage effect for diverting attention in order to make the latent image less noticeable.

[0030] The algorithm used by the latent image forming unit 140 utilizes, as a first characteristic, the property that, for example, as in the printed matter disclosed in Patent Document 2 (hereinafter referred to as the "first latent image printed matter"), the superposition of cyan (C), magenta (M), and yellow (Y) among the four basic colors of cyan (C), magenta (M), yellow (Y), and black (Bk) does not absorb infrared rays, and utilizes, as a second characteristic, the property that carbon black-containing black (Bk) absorbs infrared rays. In the first latent image printed matter, in the visible image, the mixed-color black formed by superposing cyan (C), magenta (M), and yellow (Y) and black (Bk) are visually recognized as having the same color. However, when observed using a special identification device such as an infrared camera, cyan (C), magenta (M), and yellow (Y) are not visually recognized, and a latent image printed with carbon black-containing black (Bk) ink can be visually recognized. When the algorithm used by the latent image forming unit 140 is the first latent image printed matter, the reader 300 described later may be an identification device such as an infrared camera.

[0031] Incidentally, as shown in FIG. 1, a latent image generation device 100 according to the disclosed technology has a printing machine 200 connected to its subsequent stage. That is, the disclosed technology is premised on printing. In printing, gradation expression is realized by intentionally changing the area ratio between the portion where ink adheres to the paper and the portion where it does not adhere (the white background portion). It can be said that printing technology implements a pseudo gradation expression that utilizes the illusion of the human eye. Specifically, what creates this pseudo gradation is the large and small ink dots arranged at equal intervals vertically and horizontally. These large and small ink dots are called "halftone dots". The first latent image printed matter is a preferable technology with high affinity to the latent image generation device 100 according to the disclosed technology which is premised on printing.

[0032] A printed matter using the algorithm used by the latent image forming unit 140 has, on a substrate, a plurality of first units in a positive-negative relationship arranged to face each other with a center as a boundary, regularly arranged along a certain direction to form a first latent image, and a plurality of second units in a similar relationship, arranged in a similar configuration to form a second latent image. The first unit and the second unit are arranged at different angles on the same area, and a third unit that forms a visible image at a position overlapping a part of each unit is arranged.

[0033] In the technology of Patent Document 3, only a visible image is visually recognized. By overlaying a discriminator that is a lenticular lens or a lenticular filter, a positive image or a negative image of the first latent image appears from the first unit, and a positive image or a negative image of the second latent image appears from the second unit. The effect that the visible image seems to be replaced by the latent image by the lenticular lens is called the "image switching effect". When the algorithm used by the latent image forming unit 140 is the technology of Patent Document 3, the exposure unit 440 of the latent image decoding device 400 described later may perform image processing simulating a lenticular lens.

[0034] Similar to the first latent image printed matter, the printed matter disclosed in Patent Document 3 (hereinafter referred to as the "second latent image printed matter") is also a technology highly compatible with the latent image generation device 100 according to the present disclosure technology premised on printing.

[0035] The algorithm used by the latent image forming unit 140 is a latent image technology that is visualized by a differential filter held by the applicant, and the technology of Patent Document 3 may be further applied.

[0036] For example, in the visualization of a latent image disclosed in Patent Document 4, a method of extracting singular points of the latent image is used. In the technology related to the latent image disclosed in Patent Document 4, for the extraction of singular points, a differential filter that emphasizes local features of an image called an edge is used. In the latent image disclosed in Patent Document 4, a shape in which edges are hardly emphasized by the differential filter is applied to the first ruled line, and a shape in which edges are easily emphasized by the differential filter is applied to the second ruled line. The image output by the differential filter is averaged per unit area and converted into a density value. The latent image disclosed in Patent Document 4 is such that the difference between two density values becomes the contrast of an image for visualizing the latent image by a latent image reading device.

[0037] When the algorithm used in the latent image forming unit 140 applies the technology related to the latent image disclosed in Patent Document 4, the exposure unit 440 of the latent image image decoding device 400 described later may perform image processing applying a differential filter or a difference filter. Note that the latent image forming unit 140 may perform a latent image forming process only using the latent image disclosed in Patent Document 4, or may perform the latent image forming of Patent Document 2 or Patent Document 3 after forming a latent image with a differential filter.

[0038] Similar to Patent Documents 2 and 3, since the latent image of Patent Document 4 is also a technology applicable to printed matter, it is a technology with high affinity to the latent image generation device 100 according to the present disclosure technology premised on printing.

[0039] 《Printing Machine 200》 The printing machine 200 is a so-called security printing machine or a printer capable of printing important documents on demand, for the purpose of printing banknotes, passports, securities, certificates, and other important documents. Note that the printing method in the printing machine 200 is not particularly limited, and a normal printing method is used. For example, those with a printing method having a printing plate surface such as letterpress, dry offset, offset, flexo, gravure, or orloff, and those without a printing plate surface such as inkjet printing and toner printing (laser printing) can be mentioned. For the printing of the above-mentioned important documents, a function of preventing forgery is required in addition to beauty.

[0040] 《Reader 300》 The reader 300 is a device for reading printed materials that are important documents such as banknotes, passports, securities, and certificates. Specifically, the reader 300 is composed of digital devices such as a scanner and a camera. As described above, when the latent image forming unit 140 applies the technology of Patent Document 2, the reader 300 has the function of an infrared camera.

[0041] The reader 300 may be realized by the camera and application provided in a mobile terminal equipped with a mobile operating system such as a so-called smartphone.

[0042] 《Exposing Unit 440 Constituting the Latent Image Decoding Device 400》 It can be said that the exposing unit 440 constituting the latent image decoding device 400 is a component in a dual relationship with the latent image forming unit 140 constituting the latent image generating device 100. The exposing unit 440 performs the reverse process of the process performed by the latent image forming unit 140 in the latent image generating device 100. Briefly speaking, the exposing unit 440 performs a process of visualizing a latent image.

[0043] When the latent image forming unit 140 in the latent image generating device 100 applies the printed material of the above-mentioned Patent Document 2, the exposing unit 440 visualizes the latent image formed on the printed material by the infrared camera function. When the latent image forming unit 140 in the latent image generation apparatus 100 applies the printed matter of Patent Document 3 described above, the exposure unit 440 converts the latent image formed on the printed matter into a visible image by image processing simulating a lenticular lens. When the latent image forming unit 140 in the latent image generation apparatus 100 applies the printed matter of Patent Document 4 described above, the exposure unit 440 converts the latent image formed on the printed matter into a visible image by image processing applying a differential filter or a difference filter.

[0044] 《Combining Unit 430 Constituting the Latent Image Decoding Apparatus 400》 The combining unit 430 constituting the latent image decoding apparatus 400 can be said to be a component in a dual relationship with the dispersing unit 130 constituting the latent image generation apparatus 100. The combining unit 430 performs the reverse process of the process performed by the dispersing unit 130 in the latent image generation apparatus 100. Briefly speaking, the combining unit 430 performs a process of combining pieces arranged dispersed in an image field (PF) into one image. The combining unit 430 performs a process of combining into one image based on the piece arrangement information shared with the dispersing unit 130.

[0045] 《Character Conversion Unit 420 Constituting the Latent Image Decoding Apparatus 400》 The character conversion unit 420 constituting the latent image decoding apparatus 400 can be said to be a component in a dual relationship with the imaging unit 120 constituting the latent image generation apparatus 100. The character conversion unit 420 performs the reverse process of the process performed by the imaging unit 120 in the latent image generation apparatus 100. Briefly speaking, the character conversion unit 420 converts information of an image related to a latent image (hereinafter referred to as “latent image image”) into character information.

[0046] For example, assume that the imaging unit 120 in the latent image generation apparatus 100 converts character information into a two-dimensional code based on a certain standard. In this case, the character conversion unit 420 converts the two-dimensional code into character information based on the standard of the two-dimensional code.

[0047] 《Primary Decoding Unit 410 Constituting the Latent Image Decoding Apparatus 400》 It can be said that the primary decoding unit 410 that constitutes the latent image decoding device 400 is a component in a dual relationship with the primary encryption unit 110 that constitutes the latent image generation device 100. The primary decoding unit 410 performs the reverse process of the process performed by the primary encryption unit 110 in the latent image generation device 100. Simply put, the primary decoding unit 410 decodes the character information obtained from the character conversion unit 420. Viewed from another perspective, it can be said that the primary decoding unit 410 decodes the ciphertext encrypted by the primary encryption unit 110.

[0048] For example, when the primary encryption unit 110 encrypts "Tokkyo Taro" to "Hlmmbl Hyil" using the substitution table shown in FIG. 2, the primary decoding unit 410 uses the substitution table shown in FIG. 2 to decrypt "Hlmmbl Hyil" to "Tokkyo Taro". Also, for example, when the primary encryption unit 110 uses a hash function, the primary decoding unit 410 decrypts using the inverse function of the hash function used.

[0049] FIG. 5 is a hardware configuration diagram showing an example of the hardware configuration of the latent image generation device 100 and the latent image decoding device 400 according to the disclosed technology. Specifically, FIG. 5 shows a general-purpose computer 500 including an input interface 510, a processor 520, and an output interface 530. Note that the general-purpose computer 500 may be realized in the form of a mobile terminal equipped with a mobile-oriented operating system such as a so-called smartphone. In this case, the programs (latent image generation program, latent image decoding program) described later may be realized by, for example, an application that runs on a mobile-oriented operating system.

[0050] When the latent image generation device 100 is implemented by a general-purpose computer 500, the functions of the primary encryption unit 110, the imaging unit 120, the dispersion unit 130, and the latent imaging unit 140 are realized by software. The software is described as a latent image generation program and stored in a memory. The general-purpose computer 500 realizes the functions of the primary encryption unit 110, the imaging unit 120, the dispersion unit 130, and the latent imaging unit 140 by reading and executing the latent image generation program stored in the memory. That is, when the latent image generation device 100 is implemented by the general-purpose computer 500, it includes a memory for storing a latent image generation program in which the functions of the primary encryption unit 110, the imaging unit 120, the dispersion unit 130, and the latent imaging unit 140 are consequently executed. Also, it can be said that the latent image generation program causes the general-purpose computer 500 to execute the procedures and methods of the primary encryption unit 110, the imaging unit 120, the dispersion unit 130, and the latent imaging unit 140.

[0051] When the latent image generation device 100 is implemented by a general-purpose computer 500, the input interface 510 is an interface for inputting the "latent image characters" shown in FIG. 1. Specifically, the input interface 510 is a keyboard or the like for inputting characters. Also, when the latent image generation device 100 is implemented by a general-purpose computer 500, the output interface 530 is an interface such as a terminal for connecting to the printing machine 200.

[0052] When the latent image decoding device 400 is implemented by a general-purpose computer 500, the functions of the primary decoding unit 410, the character conversion unit 420, the combination unit 430, and the revelation unit 440 are realized by software. The software is described as a latent image decoding program and stored in a memory. The general-purpose computer 500 realizes the functions of the primary decoding unit 410, the character conversion unit 420, the combination unit 430, and the revelation unit 440 by reading and executing the latent image decoding program stored in the memory. That is, when the latent image decoding device 400 is realized by the general-purpose computer 500, it includes a memory for storing a latent image decoding program in which the functions of the primary decoding unit 410, the character conversion unit 420, the combination unit 430, and the exposure unit 440 are ultimately executed. Also, it can be said that the latent image decoding program causes the general-purpose computer 500 to execute the procedures and methods of the primary decoding unit 410, the character conversion unit 420, the combination unit 430, and the exposure unit 440.

[0053] When the latent image decoding device 400 is realized by the general-purpose computer 500, the input interface 510 is an interface such as a terminal for connecting the reader 300. Also, when the latent image decoding device 400 is realized by the general-purpose computer 500, the output interface 530 is an interface for outputting the "latent image characters" shown in FIG. 1. Specifically, the output interface 530 is a display or the like for displaying characters.

[0054] The technical features of the latent image generation device, the latent image decoding device, the latent image generation program, and the latent image decoding program according to Embodiment 1 lie in the fact that classical encryption technology and latent image technology are skillfully combined. By having this technical feature, the disclosed technology can realize the printing and reading of banknotes, passports, securities, certificates, and other important documents with a high forgery prevention effect.

[0055] (Embodiment 2) The latent image generation device, the latent image decoding device, the latent image generation program, and the latent image decoding program according to Embodiment 2 are modified examples of the latent image generation device, the latent image decoding device, the latent image generation program, and the latent image decoding program according to the disclosed technology. Unless otherwise specified, the same reference numerals as those used in Embodiment 1 are used in Embodiment 2. Also, in Embodiment 2, descriptions overlapping with Embodiment 1 are omitted as appropriate.

[0056] FIG. 6 is an explanatory diagram showing a processing example of the primary encryption unit 110 and the imaging unit 120 of the latent image generation device 100 according to Embodiment 2. As shown in FIG. 6, the information input to the primary encryption unit 110 may include not only the name of the individual in question but also the individual's date of birth and issue date.

[0057] For example, when the printed matter created by the printing machine 200 is a passport, in addition to the name, the date of birth and issue date are essential items. In the example shown in FIG. 6, “D.o.B.: 2000.01.01” is shown as the individual's date of birth. Here, D.o.B. is the initial of Date of Birth representing the date of birth. Also, in the example shown in FIG. 6, “Issue: 2023.07.05” is shown as the issue date.

[0058] Instead of encrypting each of the date of birth and issue date, the primary encryption unit 110 may output the difference between the two dates and times. FIG. 6 shows 8586 [days], which is the number of days between January 1, 2000 and July 5, 2023. In this way, the primary encryption unit 110 may be provided with a difference filter that outputs the difference.

[0059] Although not shown in the figure, the disclosed technology may further adopt a PIN. For example, the primary encryption unit 110 may take the difference from the PIN for the date of birth or issue date and output it.

[0060] In the example illustration of FIG. 6, character information such as “Hlmmbl Hyil” and “8586” is input to the imaging unit 120. As described above, the imaging unit 120 may perform imaging based on the braille standard. FIG. 6 shows that the imaging unit 120 is imaging the character information such as “Hlmmbl Hyil” and “8586” based on the braille standard.

[0061] FIG. 7 is an explanatory diagram showing a processing example of the imaging unit 120 according to Embodiment 2. As shown in FIG. 7, the imaging unit 120 may decompose and rearrange the image of "Hlmmbl Hyil" and the image of "8586" based on a predetermined rule. In the example shown in FIG. 7, the imaging unit 120 divides the image information corresponding to the first character "H" into two on the left and right, and inserts the image information corresponding to the first digit "8" therein. By thus decomposing and rearranging two or more pieces of image information by the imaging unit 120, the forgery prevention effect can also be improved.

[0062] The technical features of the latent image generation device, latent image decoding device, latent image generation program, and latent image decoding program according to Embodiment 2 also lie in that classical encryption technology and latent image technology are skillfully combined. By having this technical feature, the disclosed technology can realize printing and reading of banknotes, passports, securities, certificates, and other important documents with a high forgery prevention effect.

[0063] (Embodiment 3) The latent image generation device, latent image decoding device, latent image generation program, and latent image decoding program according to Embodiment 3 are modified examples of the latent image generation device, latent image decoding device, latent image generation program, and latent image decoding program according to the disclosed technology. Unless otherwise specified, the same reference numerals as those used in the previously described embodiments are used in Embodiment 3. Also, in Embodiment 3, descriptions overlapping with the previously described embodiments are omitted as appropriate.

[0064] In Embodiment 1, Patent Documents 2, 3, and 4 are shown as algorithms used by the latent image forming unit 140, but the disclosed technology is not limited thereto. The latent image forming unit 140 according to the disclosed technology may use an algorithm related to a stereogram or autostereoscopy.

[0065] In particular, single-image random dot stereograms (SIRDS) and single-image stereograms (SIS), which can achieve stereoscopic vision with only a single image, are promising methods used by the latent image forming unit 140. The fact that there is only one image has the effect of making it impossible to realize that a stereogram is being used.

[0066] When the latent image forming unit 140 adopts an algorithm based on SIS, the image information obtained from the imaging unit 120, for example, the image of a two-dimensional code, is converted so that the contrast between "white" and "black" becomes a difference in depth such as "front" and "back". Also, when the latent image forming unit 140 adopts an algorithm based on SIS, the active image is preferably a periodic pattern although it is not essential.

[0067] Some commonly known stereograms are sold in the form of publications for the purpose of vision restoration, for example. Since these stereograms in publications are assumed to be viewed by humans with the naked eye, they are designed by calculating the binocular parallax of humans. Although the technology of the present disclosure may assume that humans view with the naked eye, it is not necessary to be restricted by this constraint. Finally, the reverse process of the latent image forming process in the latent image forming unit 140 may be realized by the exposure process in the exposure unit 440 of the latent image decoding device 400.

[0068] The technical features of the latent image generating device, latent image decoding device, latent image generating program, and latent image decoding program according to Embodiment 3 also lie in the fact that classical encryption technology and latent image technology are skillfully combined. By having this technical feature, the technology of the present disclosure can realize the printing and reading of banknotes, passports, securities, certificates, and other important documents with a high forgery prevention effect.

Industrial Applicability

[0069] The disclosed technology can be applied to industrial products related to the printing and reading of banknotes, passports, securities, certificates, and other important documents, and has industrial applicability.

Explanation of Signs

[0070] 100 Latent image generation device 110 Primary encryption unit 120 Imaging unit 130 Dispersion unit 140 Latent imaging unit 200 Printing machine 300 Reader 400 Latent image decoding device 410 Primary decryption unit 420 Character conversion unit 430 Combination unit 440 Revelation unit 500 General-purpose computer 510 Input interface 520 Processor 530 Output interface

Claims

1. An encryption unit that encrypts latent image characters that a user wants to make into a latent image; An imaging unit that creates an image from the result encrypted by the encryption unit; A decentralization unit that disperses and arranges the imaged information obtained by the imaging unit into a plurality of pieces based on a rule; A latent imaging unit that converts the image in which the pieces obtained by the decentralization unit are dispersed and arranged into a latent image, comprising a latent image generation device. Latent image generation device.

2. An exposure unit that visualizes a latent image; An integration unit that combines the pieces dispersed and arranged in a visible image field based on a rule into one latent image; A character conversion unit that converts the latent image into character information; A primary decryption unit that decrypts the character information obtained from the character conversion unit, comprising a latent image decoding device. Latent image decoding device.

3. A process of encrypting latent image characters that a user wants to make into a latent image; A process of imaging the result encrypted by the process of encrypting; A process of dispersing and arranging the imaged information obtained by the process of imaging into a plurality of pieces; A process of converting the image in which the pieces obtained by the arranging process are dispersed and arranged into a latent image, including a latent image generation program. Latent image generation program.

4. A process of visualizing a latent image; A process of combining the pieces dispersed and arranged in a visible image field into one latent image; A process of converting the latent image into character information; A process of decrypting the character information obtained by the process of converting into the character information, including a latent image decoding program. Latent image decoding program.

Images