Method and program for identifying image-forming entities

Abstract

To provide a method and a program for discriminating an image forming body whose image changes depending on an observation distance, utilizing a portable terminal.SOLUTION: A method for discriminating an image forming body allows an information processor storing a first comparison image for discriminating a first image and a second comparison image for discriminating a second image, both of which are formed in an imaging area, to capture an image capturing region in which an image region is captured, acquire a first observation image obtained by imaging the first image and a second observation image obtained by imaging the second image from the imaging area, perform a first matching between the first observation image and the first comparison image, perform a second matching between the second observation image and the second comparison image, and discriminate the image in the imaging area to be the image forming body if the first observation image is within a first threshold relative to the first comparison image by the first matching, and if the second observation image is within a second threshold relative to the second comparison image by the second matching.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for discriminating an image forming body such as a banknote, a share certificate, a security, a ticket, a passport, a card, etc., a method for discriminating the authenticity of an image forming body, and an image forming body discrimination program.

Background Art

[0002] As a technique for changing an image observable with the naked eye, there is a technique that utilizes spatial frequency. Spatial frequency is what is obtained by considering the repetition of light and darkness as a wave (frequency). Human vision (the image projected onto the retina) has the property that it is difficult to see stripes that are too fine or too coarse with respect to the level of spatial frequency.

[0003] As an example of a technique that utilizes the characteristics of spatial frequency, there is a hybrid image (see Non-Patent Document 1) obtained by synthesizing two grayscale images having different spatial frequencies. A hybrid image is formed, for example, by synthesizing a first image obtained by extracting only low-frequency components from a first portrait photo and a second image obtained by extracting only high-frequency components from a second portrait photo through image processing. In a hybrid image, the size of the image projected onto the retina changes due to a change in the observation distance, and the spatial frequency changes accordingly. Therefore, when observing a hybrid image from a long distance, the sensitivity of vision matches the low-frequency components and the first image can be visually recognized. On the other hand, when observing from a short distance, the sensitivity of vision matches the high-frequency components, so that the second image can be visually recognized.

[0004] As another technique for changing an image observable with the naked eye, there is also a technique that utilizes the contrast of brightness. The contrast of brightness is a phenomenon in which when a certain area is surrounded by an area darker than it, that area appears brighter, and conversely, when surrounded by an area brighter than it, that area appears darker. In addition, it is also a phenomenon in which when an area formed with a certain color is surrounded by an area of a different color, the color of the surrounded area appears prominent.

[0005] An example of a technology that utilizes the characteristics of spatial frequency and brightness contrast is an image forming body (10) (see Patent Document 1). Figure 12(a) shows an example of an image forming body (10A), in which, for pixels arranged on a matrix, a near-field image (see Figure 12(b)) is formed based on the presence or absence of elements of a different color from the pixels inside the pixels, and a far-field image (see Figure 12(c)) is formed based on the size of the pixels. The image-forming element (10A) changes the size of the image projected onto the retina with changes in observation distance, and consequently, the effect of brightness contrast in each element becomes stronger or weaker. Therefore, when observed from a distance, the brightness contrast is emphasized relative to the size of the pixels themselves, and the long-distance image (22A) shown in Figure 12(c) can be seen. On the other hand, when observed from a close distance, the effect of brightness contrast is emphasized relative to elements of a different color from the pixels within the pixels, and the close-up image (21A) shown in Figure 12(b) can be seen.

[0006] On the other hand, in recent years, mobile devices such as smartphones have become widely popular and used by the general public. In addition to making calls, sending emails, and exchanging information via social media, various technologies are now being widely used, such as browsing websites using addresses read from QR codes with the built-in camera function, and displaying predetermined 3D models on the smartphone screen based on the reading results. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2015-39831 [Non-patent literature]

[0008] [Non-Patent Document 1] “The Art of Hybrid Images: Two for The View of One”, Aude Oliva, Art & Perception 1(2013)65-74 [Overview of the project] [Problems that the invention aims to solve]

[0009] The technologies described in Non-Patent Document 1 and Patent Document 1 are based on the premise of using the naked eye and changing the observation distance. However, since there are individual differences in the observer's visual acuity, including myopia, hyperopia, and astigmatism, problems arise in terms of visibility, such as the image itself not being visible unless it is enlarged, or only one of the two types of images being visible, or viewing distance problems, such as needing to move more than the bending and straightening of the arm before the image switches and can be observed. In particular, when dealing with banknotes, stock certificates, securities, passes, passports, cards, etc., the images must be reduced in size and placed within a limited area, which significantly increases the problem of individual differences in image visibility and viewing distance. Furthermore, because this technology relies on visual confirmation, simply placing it on the ticket surface is unlikely to attract the observer's attention. Additionally, if observers do not remember to change their observation distance, the technology may not be fully utilized.

[0010] Furthermore, while it is possible to observe the image formation body (10) using the camera function of a mobile device and adjust the shooting distance to observe changes in the image through the digital screen of the mobile device, it is still observed with the naked eye, and the problem of individual differences remains.

[0011] The present invention provides a method for reliably identifying an image-forming body (10) by means other than observation with the naked eye, which involves capturing an image of the image-forming body (10) with an information processing device (30) and automatically identifying a first image (21) and a second image (22) present within an image region (12). Furthermore, the present invention provides a method for determining the authenticity of a ticket based on whether or not an image-forming element (10) on the ticket surface is discernible. Furthermore, the present invention provides a program that performs the identification of the image forming body (10) and the determination of the authenticity of the ticket surface using the image forming body (10). [Means for solving the problem]

[0012] The present invention relates to a method for discriminating an image-forming body in which a first image and a second image are formed within at least a portion of the image area on a substrate, the first image being visible at a first distance, and the second image being visible at a second distance. An information processing device that stores a first comparison image for determining the first image and a second comparison image for determining the second image, Capture at least one imaging region from which the aforementioned image region has been photographed. From the imaging area, the first observation image obtained by capturing the first image, The second observation image obtained by capturing the aforementioned second image, A first comparison is performed using the first observation image and the first comparison image. A second comparison is performed using the second observation image and the second comparison image. The method for identifying an image forming body is characterized in that, if the first matching shows that the first observed image is within a first threshold relative to the first comparison image, and the second matching shows that the second observed image is within a second threshold relative to the second comparison image, then the image in the imaging area is determined to be the image forming body.

[0013] Furthermore, the present invention is a method for discriminating an image-forming object, characterized in that the first observation image is obtained by imaging the image region from a first distance, and the second observation image is obtained by imaging the image region from a second distance.

[0014] Furthermore, the present invention is a method for discriminating an image-forming object, characterized in that the first observation image and the second observation image are acquired by imaging the image region from the same distance, and the first observation image and the second observation image are acquired by imaging the image region at different magnifications or at different depths of field.

[0015] Furthermore, the present invention relates to a method for discriminating an image-forming object, characterized in that the information processing device is a portable terminal having an imaging means.

[0016] The present invention also relates to a program for determining an image forming body in which a first image and a second image are formed in at least a part of an image area on a base material, the first image being visible at a first distance, and the second image being visible at a second distance, wherein an information processing device storing a first comparison image for determining the first image and a second comparison image for determining the second image, performs a step of capturing at least one captured area obtained by capturing the image area, a step of obtaining, from the captured area, a first observed image obtained by capturing the first image and a second observed image obtained by capturing the second image, a step of performing a first collation between the first observed image and the first comparison image, a step of performing a second collation between the second observed image and the second comparison image, a step of determining that the image in the captured area is the image forming body if the first observed image is within a first threshold with respect to the first comparison image by the first collation and the second observed image is within a second threshold with respect to the second comparison image by the second collation, and causes the information processing device to execute the above steps, which is a program for determining an image forming body.

Advantages of the Invention

[0017] By using the information processing device (30), the present invention can surely determine the image forming body (10) by a method other than visual observation with the naked eye. Therefore, it becomes easy to utilize the image forming body (10) for banknotes, stock certificates, securities, tickets, passports, cards, etc. In addition, since the present invention can be implemented by imaging the surface of a ticket using the information processing device (30), an observer does not need to remember how to use the image forming body (10), and it becomes possible to reduce the difficulty of observing the image forming body (10).

Brief Description of the Drawings

[0018] [Figure 1] A diagram showing an example of an image forming body (10) to be determined by the present invention [Figure 2] This figure shows an example of the effects of the first image (21) and the second image (22) in the image forming body (10) that is the subject of discrimination in the present invention. [Figure 3] This figure shows an example in which an information processing device (30) captures an imaging region (50) including an image region (12) from an image forming body (10) in a first embodiment of the present invention. [Figure 4] A diagram showing an example of the internal configuration of the information processing device (30). [Figure 5] This figure shows the case where the imaging distance (L) of the image region (12) is different. [Figure 6] This figure shows the case where the imaging distance (L) of the image region (12) is equal. [Figure 7] This figure shows an example of obtaining a first observation image (51) and a second observation image (52) through image processing. [Figure 8] This figure shows an example of acquiring a first observation image (51) and a second observation image (52) at different magnifications. [Figure 9] This figure shows an example of acquiring a first observation image (51) and a second observation image (52) with different depths of field. [Figure 10] Flowchart of the image-forming agent (10) discrimination program, which is performed by capturing an image region (12) at a first distance (L1) and a second distance (L2), respectively. [Figure 11] Flowchart of the image-forming agent (10) discrimination program, which is performed by imaging an image region (12) at a single imaging distance (L). [Figure 12] A diagram showing an example of a conventional image-forming device (10A). [Modes for carrying out the invention]

[0019] Embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments for carrying out the invention described below, and includes various other embodiments as long as they are within the scope of the technology described in the claims.

[0020] Figure 1 shows an example of an image forming body (10) that is the subject of discrimination in the present invention. As shown in Figure 1, the image forming body (10) in the present invention has an image area (12) in at least a part of the substrate (11). In this case, the material of the substrate (11) is a material having a flat surface, including paper materials such as high-quality paper or coated paper, thin films such as films, or plate materials such as plastics, and a first image (21) and a second image (22) are formed individually or overlapping in the image area (12). For the purpose of facilitating imaging of the image area (12), which will be described later, a trigger mark (13) that serves as a trigger for imaging may be placed adjacent to the image area (12). In addition, if there are multiple types of image forming bodies (10), a face value (14) or a serial number (15) may be placed to distinguish them from one another.

[0021] Figure 2 shows an example of the effects of the first image (21) and the second image (22) in the image forming body (10). As shown in Figure 2, when a visual observer (99) observes the image area (12) with the naked eye, the first image (21) is visible at a first distance (L1), while the second image (22) is visible at a second distance (L2). Thus, the image forming body (10) that is the object of discrimination in this invention exhibits an effect in which the visible pattern changes with the observation distance.

[0022] A method for discriminating an image forming body (10) in an embodiment of the present invention will be explained with reference to Figures 3 to 9.

[0023] Figure 3 shows an example of how an information processing device (30) captures an imaging area (50) from an image forming body (10). As shown in Figure 3, the information processing device (30) uses an imaging means (30A) to capture an imaging area (50) including an image area (12) from the image forming body (10) using the imaging means (30A). In this invention, the information processing device (30) is intended for mobile terminals having an imaging means (30A), including smartphones and tablet terminals, and the imaging means (30A) captures at least one of a still image or a video as an captured image (50A) of the imaging area (50) including the image area (12). In Figure 3, the imaging means (30A) is shown as being built into the information processing device (30), but the imaging means (30A) and the information processing device (30) may be physically separated and arranged, and the captured image (50A) captured by the imaging means (30A) may be received by wired or wireless means.

[0024] Figure 4 shows an example of the internal configuration of the information processing device (30). As shown in Figure 4, the information processing device (30) has at least a reading unit (30B), a storage unit (30C), and a processing unit (30D).

[0025] The reading unit (30B) reads and saves the first image (21) and the second image (22) from the captured image (50A) captured by the imaging means (30A). At this time, as an example of how to acquire the first image (21) and the second image (22), from the captured image (50A) obtained under various imaging conditions described later, the first image (21) that was captured may be acquired as the first observation image (51), and the second image (22) that was captured may be acquired as the second observation image (52). Another example of how to acquire the first image (21) and the second image (22) is that the captured image (50A) may be edited using known image processing methods including filtering such as a Gaussian filter or median filter, binarization or color inversion, to create and save the first observation image (51) from which the first image (21) was extracted and the second observation image (52) from which the second image (22) was extracted.

[0026] The memory unit (30C) has in advance stored at least a first comparison image (31), a second comparison image (32), a first threshold (41), and a second threshold (42).

[0027] The first comparison image (31) is an image used as a criterion for distinguishing the first image (21), and the second comparison image (32) is an image used as a criterion for distinguishing the second image (22). In this invention, the first comparison image (31) and the second comparison image (32) may be the image or video data itself in which the first image (21) and the second image (22) to be compared are captured. Alternatively, known image processing such as scaling the image size, filtering with a Gaussian filter or median filter, binarization, or color inversion may be applied to the captured image (50A), and the image or video data from which the first image (21) and the second image (22) are extracted may be used as the first observation image (51) and the second observation image (52).

[0028] The first threshold (41) is used for comparing the first image (21) with the first comparison image (31) (first comparison), and the second threshold (42) is used for comparing the second image (22) with the second comparison image (32) (second comparison). In this invention, the first and second comparisons are performed using known comparison methods, including pattern matching to determine the degree of agreement (similarity) between each image and the comparison image, and comparison of local reference feature data (see Japanese Patent Application Publication No. 2014-174727). The first threshold (41) and the second threshold (42) use predetermined images or numerical values ​​based on the aforementioned known comparison methods.

[0029] The processing unit (30D) stores the image discrimination program described later and performs image discrimination using the image or video data from the reading unit (30B) and the storage unit (30C). The image processing for creating various observation images in the reading unit (30B) and the reading of various images and thresholds in the storage unit (30C) may also be performed by the processing unit (30D).

[0030] The method for acquiring the first observation image (51) and the second observation image (52) by the information processing device (30) will be explained with reference to Figures 5 to 9.

[0031] Figure 5 shows an example of an imaging method when the imaging distance (L) is changed. As shown in Figure 5, the information processing device (30) captures the image region (12) from a first distance (L1) to acquire a first observation image (51), and captures the image region (12) from a second distance (L2) to acquire a second observation image (52).

[0032] Figure 6 shows an example of an imaging method when the imaging distance (L) is constant. As shown in Figure 6, the information processing device (30) images the imaging area (50) including the image area (12) at the imaging distance (L), and acquires a first observation image (51) and a second observation image (52) by various image processing methods shown in Figure 7, which will be described later.

[0033] Figure 7 shows an example of obtaining a first observation image (51) and a second observation image (52) from the imaging area (50) captured in Figure 6 by image processing. In Figure 7, the captured image (50A) is processed using known methods including image resizing, filtering with Gaussian filters and median filters, binarization, and color inversion, to create a first observation image (51) used for comparison with a first comparison image (31) (first comparison) and a second observation image (52) used for comparison with a second comparison image (32) (second comparison).

[0034] Figure 8 shows an example in which the imaging distance (L) is constant and the imaging area (50) is imaged at different magnifications. As shown in Figure 8, the information processing device (30) acquires a first observation image (51) and a second observation image (52) by imaging the image area (12) at different magnifications (telephoto and wide-angle).

[0035] Figure 9 shows an example in which the imaging distance (L) is constant and the imaging area (50) is imaged with different depths of field. As shown in Figure 9, the information processing device (30) acquires a first observation image (51) and a second observation image (52) by imaging the image area (12) with different depths of field (degree of blurring).

[0036] The discrimination program for the image forming body (10) in an embodiment of the present invention will be explained with reference to Figures 10 and 11.

[0037] Figure 10 is a flowchart of the image-forming body (10) discrimination program, which is performed by capturing an image region (12) at a first distance (L1) and a second distance (L2) respectively (see Figure 5).

[0038] In Figure 10, the information processing device (30) activates the imaging means (30A) (S1), acquires a first observation image (51) for the reading unit (30B) by imaging the image region (12) from a first distance (L1) (S2), and acquires a second observation image (52) for the reading unit (30B) by imaging the image region (12) from a second distance (L2) (S3). There may be a reading start step (S1-2), not shown, between S1 and S2, in which the acquisition of the first observation image (51) and the second observation image (52) is started by reading a trigger mark (13) from within the image region (12). Furthermore, the acquisition of the first observation image (51) and the second observation image (52) can be performed even if the order is reversed.

[0039] The information processing device (30) that performed S2 and S3 performs a first comparison (S4) between the first observation image (51) acquired in S2 and the first comparison image (31) stored in the storage unit (30C).

[0040] If the first comparison shows that the first observed image (51) is within the first threshold (41) relative to the first comparison image (31) (Yes in S5), the information processing device (30) performs a second comparison between the second observed image (52) acquired in S3 and the second comparison image (32) stored in the storage unit (30C) (S6).

[0041] If, by the second comparison, the second observation image (52) is within the second threshold (42) relative to the second comparison image (32) (Yes in S7), the information processing device (30) determines that the captured image-forming body (10) is an image-forming body (10) having a specific first image (21) and second image (22) (S8), and outputs the determination result (S10).

[0042] At this time, if the result of the first comparison is that the first observation image (51) is not within the first threshold (41) relative to the first comparison image (31) (No in S5), the information processing device (30) determines that the captured image-forming body (10) does not have a specific first image (21) (S9) and outputs the determination result (S10). Also, if the result of the second comparison is that the second observation image (52) is not within the second threshold (42) relative to the second comparison image (32) (No in S7), the information processing device (30) determines that the captured image-forming body 10 does not have a specific second image (22) (S9) and outputs the determination result (S10). Note that the first and second comparisons can be performed in any order.

[0043] Figure 11 is a flowchart of an image-forming agent (10) discrimination program performed by capturing an image region (12) at a single imaging distance (L) (see Figures 6 to 9).

[0044] In Figure 11, the information processing device (30) activates the imaging means (30A) (S1) and acquires an image (50A) by imaging the image region (12) from an arbitrary imaging distance (L) (S21). Furthermore, between S1 and S21, there may be a reading start step (S1-2) (not shown) in which the acquisition of the first observation image (51) and the second observation image (52) is started by reading a trigger mark (13) from the image area (12). Also, in S21, multiple images may be acquired by changing the magnification of the imaging means (30A) (see Figure 8), or multiple images may be acquired by changing the depth of field of the imaging means (30A) (see Figure 9).

[0045] The information processing device (30) applies known image processing (see Figure 7) to the captured image (50A) acquired in S21, such as scaling the image size, filtering with Gaussian filters or median filters, binarization, or color inversion (S22), and then performs pattern matching with the first comparison image (31) and the second comparison image (32) on the image obtained in S22 (S23).

[0046] If, as a result of S23, the image that best matches the first comparison image (31) is obtained (Yes in S24a), that image is acquired by the reading unit (30B) as the first observation image (51). If, as a result of S23, the image that best matches the second comparison image (32) is obtained (Yes in S25a), that image is acquired by the reading unit (30B) as the second observation image (52). At this time, if the number of No judgments in S24a is x (Yes in S24b), and the number of No judgments in S25a is y (Yes in S25b), a reading error (S26) is determined, and the judgment result is output (S10). Note that the numbers x and y may be the same or different. Also, the order of pattern matching may be reversed.

[0047] If S24a and S25a are answered Yes, the information processing device (30) performs a first comparison between the first observation image (51) acquired in S24a and the first comparison image (31) stored in the storage unit (30C) (S4).

[0048] If the first comparison shows that the first observed image (51) is within the first threshold (41) relative to the first comparison image (31) (Yes in S5), the information processing device (30) performs a second comparison between the second observed image (52) acquired in S25a and the second comparison image (32) stored in the storage unit (30C) (S6).

[0049] If, by the second comparison, the second observed image (52) is within the second threshold (42) relative to the second comparison image (32) (Yes in S7), the information processing device (30) determines that the captured image-forming body (10) is an image-forming body (10) having a specific first image (21) and second image (22) (S8), and outputs the determination result (S10). At this time, S4 and S6 may be performed simultaneously in S23. The method of outputting the determination means is a known method including image display, sound, or vibration.

[0050] In the embodiment of the present invention, an image forming body (10) having a first image (21) and a second image (22) can be mechanically distinguished using an information processing device (30). Therefore, it is possible to stably distinguish the image forming body (10) without the individual differences that occur with conventional observation with the naked eye. Furthermore, in the present invention, since the image forming body (10) can be distinguished even when the imaging distance (L) is the same, it is possible to use the image forming body (10) as an element for machine reading and authenticity determination, such as by placing the image forming body (10) on various valuable printed materials and card products and automatically performing two-factor authentication with a mobile terminal equipped with an information processing device (30). [Explanation of Symbols]

[0051] 10 Image Maker 11 Base material 12 Image area 21 Image 1 22 Image 2 30 Information Processing Devices 30A Imaging means 30B Reading Unit 30C storage section 30D Processing Unit 31. First comparison image 32. Second comparison image 41. First threshold 42. Second threshold 50 imaging area 50A Acquired Image 51 First observation image 52 Second observation image L imaging distance L1 1st distance L2 2nd distance 99 Visual observers

Claims

1. A method for discriminating an image forming body in which a first image and a second image are formed within at least a portion of the image area on a substrate, the first image being visible at a first distance, and the second image being visible at a second distance, An information processing device that stores a first comparison image for determining the first image and a second comparison image for determining the second image, Capture at least one imaging region from which the aforementioned image region has been photographed. From the imaging area, the first observation image obtained by capturing the first image, The second observation image obtained by taking the aforementioned second image is acquired, A first comparison is performed using the first observation image and the first comparison image. A second comparison is performed using the second observation image and the second comparison image. A method for determining an image forming body, characterized in that, if the first observation image is within a first threshold relative to the first comparison image as determined by the first matching, and the second observation image is within a second threshold relative to the second comparison image as determined by the second matching, then the image in the imaging area is determined to be the image forming body.

2. The first observation image is acquired by imaging the image region from a first distance. The method for determining an image forming body according to claim 1, characterized in that the second observation image is obtained by imaging the image region from the second distance.

3. The first observation image and the second observation image are acquired by capturing the image region from the same distance. The method for determining an image forming body according to claim 1, characterized in that the first observation image and the second observation image are obtained by imaging the image region at different magnifications or by imaging the image region at different depths of field.

4. The method for determining an image-forming object according to claim 1, characterized in that the information processing device is a portable terminal having an imaging means.

5. A program for determining whether an image-forming body has a first image and a second image formed within at least a portion of the image area on a substrate, the first image being visible at a first distance, and the second image being visible at a second distance. An information processing device that stores a first comparison image for determining the first image and a second comparison image for determining the second image, The steps include capturing at least one imaging region from which the aforementioned image region has been photographed, The steps include acquiring a first observation image obtained by capturing the first image and a second observation image obtained by capturing the second image from the imaging area, The steps include performing a first comparison using the first observation image and the first comparison image, The steps include performing a second comparison using the second observation image and the second comparison image, The first step is to determine that the image in the imaging region is the image forming body if, by the first matching, the first observed image is within a first threshold relative to the first comparison image, and by the second matching, the second observed image is within a second threshold relative to the second comparison image. A discrimination program for an image-forming object, characterized by causing the information processing device to execute the following.

Images