阅读说明：本技术 一种光学水印成像装置及防伪设备 (Optical watermark imaging device and anti-counterfeiting equipment ) 是由 李桂林 汪昱坤 张静 刘畅 葛宏伟 于 2021-02-22 设计创作，主要内容包括：本申请提供一种光学水印成像装置及防伪设备,属于光学加密技术领域。该光学水印成像装置包括：微透镜层,由多个微透镜排列而成；成像载体,设置在所述微透镜层下方；图文层,设置在所述成像载体下方,所述图文层嵌入有多个微图文结构；每个所述微图文结构中均设置有n个编码区域,且每个所述微图文结构中所设置的n个编码区域的设置位置相同,每个所述微图文结构中的n个编码区域对应一个像素点的成像；每个所述微图文结构中的n个编码区域对应的像素点组合形成水印编码图案。通过上述方式,提高了微透镜成像薄膜的防伪能力以及安全性,解决了微透镜成像薄膜易被仿制的问题。(The application provides an optical watermark imaging device and anti-counterfeiting equipment, and belongs to the technical field of optical encryption. The optical watermark imaging apparatus includes: a microlens layer formed by arranging a plurality of microlenses; an imaging carrier disposed below the microlens layer; the image-text layer is arranged below the imaging carrier, and a plurality of micro image-text structures are embedded in the image-text layer; each micro-image-text structure is provided with n coding regions, the setting positions of the n coding regions arranged in each micro-image-text structure are the same, and the n coding regions in each micro-image-text structure correspond to the imaging of one pixel point; and combining pixel points corresponding to the n encoding regions in each micro-image-text structure to form a watermark encoding pattern. By the mode, the anti-counterfeiting capacity and the safety of the micro-lens imaging film are improved, and the problem that the micro-lens imaging film is easy to imitate is solved.)

1. An optical watermark imaging apparatus, comprising:

a microlens layer formed by arranging a plurality of microlenses;

an imaging carrier disposed below the microlens layer;

the image-text layer is arranged below the imaging carrier, and a plurality of micro image-text structures are embedded in the image-text layer; each micro-image-text structure is provided with n coding regions, the setting positions of the n coding regions arranged in each micro-image-text structure are the same, and the n coding regions in each micro-image-text structure correspond to the imaging of one pixel point; and combining pixel points corresponding to the n encoding regions in each micro-image-text structure to form a watermark encoding pattern.

2. The optical watermark imaging apparatus of claim 1, wherein the plurality of microlenses are arranged in a regular hexagonal staggered arrangement.

3. The optical watermark imaging apparatus of claim 1, wherein the distance from the top of the microlens layer to the image-text layer is equal to the focal length of the microlenses;

the focal length of the micro lens is as follows:

wherein f represents a focal length of the microlens, N represents a refractive index, and R represents a radius of curvature of the microlens; the curvature radius of the micro lens is as follows:

wherein h represents the thickness of the microlens, and l is the diameter of the microlens.

4. The optical watermark imaging apparatus according to any one of claims 1-3, wherein the microlenses are 29 microns in diameter; the distance between adjacent microlenses was 1 μm.

5. The optical watermark imaging apparatus of claim 1, wherein the micro-image structures in the image-text layer are positioned in one-to-one correspondence with the micro-lenses in the micro-lens layer.

6. The optical watermark imaging device according to claim 1, wherein n encoding regions provided in each of the micro-image-text structures are obtained by converting the watermark encoding pattern by an n x m boolean matrix;

wherein n represents the number of parts for dividing each pixel point in the watermark encoding pattern into the encoding region; one pixel point in the watermark coding pattern corresponds to one or more micro-image-text structures; m represents a pixel point of each of the encoding regions.

7. An optical watermark imaging apparatus according to claim 6, wherein n has a value of 2 and m has a value of 4.

8. The optical watermark imaging apparatus of claim 7, wherein the 2 encoding regions provided in each of the microimage-text structures are provided at positions of: l ═ f × tan (θ);

wherein, L is the distance from the coding region in each micro-image-text structure to the focal point, f is the focal length of the micro-lens, and theta represents the visual angle of human eyes.

9. The optical watermark imaging apparatus of claim 8, wherein the setting position of the first encoding region in each of the micro-image-text structures corresponds to a human eye view angle of 30 degrees, and the setting position of the second encoding region in each of the micro-image-text structures corresponds to a human eye view angle of 35 degrees.

10. A security device comprising a body and an optical watermark imaging apparatus according to any one of claims 1 to 9 disposed on the body.

Technical Field

The application relates to the technical field of optical encryption, in particular to an optical watermark imaging device and anti-counterfeiting equipment.

Background

Microlenses are a common optical element, belonging to the group of passive optical elements, used in optical systems to converge and diverge optical radiation. At present, imaging films made of microlenses can be widely applied to cards, currency, and packaging. However, the existing microlens imaging films have low safety and are easily imitated.

Disclosure of Invention

An object of the embodiments of the present application is to provide an optical watermark imaging apparatus and an anti-counterfeit device, so as to improve the problems of low security and easy imitation of the existing microlens imaging film.

The invention is realized by the following steps:

in a first aspect, an embodiment of the present application provides an optical watermark imaging apparatus, including: a microlens layer formed by arranging a plurality of microlenses; an imaging carrier disposed below the microlens layer; the image-text layer is arranged below the imaging carrier, and a plurality of micro image-text structures are embedded in the image-text layer; each micro-image-text structure is provided with n coding regions, the setting positions of the n coding regions arranged in each micro-image-text structure are the same, and the n coding regions in each micro-image-text structure correspond to the imaging of one pixel point; and combining pixel points corresponding to the n encoding regions in each micro-image-text structure to form a watermark encoding pattern.

In the embodiment of the application, n coding regions are arranged in each micro image-text structure in the image-text layer, the setting positions of the n coding regions arranged in each micro image-text structure are the same, and the n coding regions in each micro image-text structure correspond to the imaging of the pixel points of one watermark coding pattern, so that the watermark coding pattern can be hidden in the image-text layer, and the acquisition of the pattern is completed by utilizing the visual angle persistence effect of human eyes.

With reference to the technical solution provided by the first aspect, in some possible implementation manners, the plurality of microlenses are arranged in a regular hexagonal staggered arrangement manner.

In the embodiment of the present application, the regular hexagonal staggered arrangement manner can maximize the ratio of the microlenses in the whole microlens layer, and under the condition that the area of the microlens layer and the size and structure of the microlenses are determined, the arrangement of the microlenses is denser, and the number of the microlenses per unit area is larger. Further, the more the focus points per unit area, the better the imaging quality of the microlens imaging device.

With reference to the technical solution provided by the first aspect, in some possible implementations, a distance from the top of the microlens layer to the image-text layer is equal to a focal length of the microlens; the focal length of the micro lens is as follows:wherein f represents a focal length of the microlens, N represents a refractive index, and R represents a radius of curvature of the microlens; the curvature radius of the micro lens is as follows:wherein h represents the thickness of the microlens, and l is the diameter of the microlens.

In the embodiment of the application, the distance from the top of the microlens layer to the image-text layer is equal to the focal length of the microlens so as to facilitate better imaging.

With reference to the technical solution provided by the first aspect, in some possible implementations, the diameter of the microlens is 29 micrometers; the distance between adjacent microlenses was 1 μm.

In the embodiment of the application, the microlenses with the diameter of 29 micrometers are adopted, and the arrangement period of the microlenses in the microlens layer is set to be 30 micrometers, so that the processing and the production are easy, and the imaging quality of the microlenses is ensured.

In combination with the technical solution provided by the first aspect, in some possible implementation manners, the micro image-text structures in the image-text layer and the micro lenses in the micro lens layer are arranged in a one-to-one correspondence in position.

In the embodiment of the application, the micro image-text structures in the image-text layer and the micro lenses in the micro lens layer are arranged in a one-to-one correspondence manner in position so as to facilitate better imaging.

With reference to the technical solution provided by the first aspect, in some possible implementation manners, the watermark coding pattern is obtained by converting the watermark coding pattern through an n × m boolean matrix in n coding regions arranged in each of the micro image-text structures; wherein n represents the number of parts for dividing each pixel point in the watermark encoding pattern into the encoding region; one pixel point in the watermark coding pattern corresponds to one or more micro-image-text structures; m represents a pixel point of each of the encoding regions.

In the embodiment of the application, the absolute safety of the encoding mode in mathematics can be realized by converting the watermark encoding pattern through the Boolean matrix.

With reference to the technical solution provided by the first aspect, in some possible implementations, the value of n is 2, and the value of m is 4.

In the embodiment of the present application, the value of n is 2, that is, the persistence of vision effect achieved by using two angles is better, so that the human brain can restore the watermark coding pattern.

With reference to the technical solution provided by the first aspect, in some possible implementation manners, the setting positions of the 2 encoding regions set in each of the microimage-text structures are: l ═ f × tan (θ); wherein, L is the distance from the coding region in each micro-image-text structure to the focal point, f is the focal length of the micro-lens, and theta represents the visual angle of human eyes.

With reference to the technical solution provided by the first aspect, in some possible implementation manners, a human eye view angle corresponding to the setting position of the first coding region in each micro image-text structure is 30 degrees, and a human eye view angle corresponding to the setting position of the second coding region in each micro image-text structure is 35 degrees.

In the embodiment of the application, the watermark coding pattern is obtained by superposing the imaging results of the micro-lens on the coded micro-image-text under the visual angles of 30 degrees and 35 degrees, and the mode has an obvious persistence effect so as to facilitate the human brain to restore the watermark coding pattern.

In a second aspect, an embodiment of the present application provides an anti-counterfeiting device, which includes a main body and an optical watermark imaging apparatus provided as the embodiment of the first aspect, which is disposed on the main body.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments of the present application will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and that those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.

Fig. 1 is a schematic structural diagram of an optical watermark imaging apparatus according to an embodiment of the present disclosure.

Fig. 2 is a schematic diagram of a watermark encoding pattern according to an embodiment of the present application.

Fig. 3 is a schematic view of a lens layer according to an embodiment of the present disclosure.

Fig. 4 is a schematic diagram of a plurality of micro-image structures in an image-text layer according to an embodiment of the present application.

Fig. 5 is a partial effect diagram of the focusing position of the first encoding region of each micro-graphic structure in the graphic layer according to the embodiment of the present application.

Fig. 6 is a partial effect diagram of the focusing position of the second encoding region of each micro-graphic structure in the graphic layer according to the embodiment of the present application.

Fig. 7 is a schematic structural diagram of an anti-counterfeiting device according to an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.

In view of the problems of low safety and easy imitation of the existing microlens imaging films, the inventors of the present application have conducted research and research to provide the following embodiments to solve the above problems.

Referring to fig. 1, an optical watermark imaging apparatus 100 is provided in an embodiment of the present application. The method comprises the following steps: microlens layer 10, imaging support 20, and graphics layer 30.

The microlens layer 10 is formed by arranging a plurality of microlenses. An imaging carrier 20 is disposed below the microlens layer 10. The image-text layer 30 is arranged below the imaging carrier 20.

In the embodiment of the present application, the image-text layer 30 is embedded with a plurality of micro image-text structures; each micro-image-text structure is provided with n coding regions (n is an integer greater than or equal to 2), the setting positions of the n coding regions arranged in each micro-image-text structure are the same, and the n coding regions in each micro-image-text structure correspond to the imaging of one pixel point; and combining pixel points corresponding to the n coding regions in each micro-image-text structure to form a watermark coding pattern.

It should be noted that the watermark encoding pattern is a self-defined information verification pattern, for example, an image of a rose (as shown in fig. 2), an icon of an enterprise, a LOGO (LOGO or trademark), and the like, which is not limited in the present application. After the optical watermark imaging device 100 is constructed and completed in the above manner, when the eyes of the user face the setting direction of the n coding regions arranged in each micro image-text structure, the decoding of the visual password can be completed through the view angle persistence effect, and the hidden watermark coding pattern can be directly obtained through the association function of the human brain. For example, each micro-image structure in the optical watermark imaging apparatus 100 shown in fig. 1 is provided with 2 encoding regions (encoding region 31 and encoding region 32, respectively), so that decoding of the visual code can be completed by the effect of persistence of visual angles formed by human eyes facing the two angles, and then the hidden watermark encoding pattern can be directly obtained by the association function of human brain.

In summary, the optical watermark imaging apparatus 100 provided in the embodiment of the present application sets n encoding regions in each micro image-text structure in the image-text layer, where the setting positions of the n encoding regions set in each micro image-text structure are the same, and the n encoding regions in each micro image-text structure correspond to the imaging of the pixel points of one watermark encoding pattern, so that the watermark encoding pattern can be hidden in the image-text layer, and the acquisition of the pattern needs to be completed by using the visual angle persistence effect of human eyes.

The structure of the optical watermark imaging apparatus 100 described above will be described in detail below.

Referring to fig. 3, in the embodiment of the present disclosure, the microlenses in the microlens layer are arranged in a regular hexagonal staggered arrangement. It should be noted that, the above regular hexagonal staggered arrangement mode can be understood that the microlenses in odd rows are arranged in sequence, and the microlenses in even rows are arranged in the gaps of the microlenses in the previous row, so that any adjacent upper, middle and lower three layers of microlenses (two first layers, three second layers and two third layers of microlenses) form a regular hexagonal pattern.

By adopting the arrangement mode, the occupation ratio of the micro lenses in the whole micro lens layer can be maximized, under the condition that the area of the micro lens layer, the size and the structure of the micro lenses are determined, the arrangement of the micro lenses is more dense, and the number of the micro lenses in unit area is more. Further, the more the focus points per unit area, the better the imaging quality of the microlens imaging device.

Of course, in other embodiments, the plurality of microlenses in the microlens layer may also adopt other arrangements, such as an orthogonal arrangement, a prismatic arrangement, or even an irregular arrangement, which is not limited in this application.

In the present embodiment, the diameter of the microlens is 29 μm; the distance between adjacent microlenses was 1 μm. Accordingly, the arrangement period of the microlenses in the microlens layer is 30 micrometers, that is, the distance between the centers of two adjacent microlenses is 30 micrometers. It should be noted that, the closer the microlens diameter is to the period, the more the microlens array is fully utilized, and the better the imaging quality is, but at a certain period, when the diameter is too large, because the slope of the lens edge is the largest, the area of the junction between the two lenses is too narrow, which is not favorable for production and processing, therefore, in the embodiment of the present application, the microlens with the diameter of 29 micrometers is adopted and the array period of the microlenses in the microlens layer is set to be 30 micrometers, which is easy for production and ensures the imaging quality of the microlenses.

Of course, in other embodiments, the diameter of the microlens may be any value from 20 to 100 micrometers, and the distance between adjacent microlenses may also be adaptively adjusted according to the diameter of the microlens, for example, when the diameter of the microlens is 50 micrometers, the distance between adjacent microlenses may be 2 micrometers, which is not limited in this application.

In addition, in the embodiment of the present application, in order to achieve better imaging, the imaging focal length of the microlens further satisfies the condition that the distance from the top of the microlens layer to the image-text layer is equal to the focal length of the microlens.

Wherein, the imaging focal length of the micro lens is as follows:

in formula (1), f represents the focal length of the microlens, N represents the refractive index, and R represents the radius of curvature of the microlens; the expression of the curvature radius R of the microlens is:

in the formula (2), h represents the thickness of the microlens, i.e., the lithography depth, and l is the diameter of the microlens.

The refractive index N is determined by the imaging carrier, and in the embodiment of the present application, the imaging carrier is made of a PET (Polyethylene terephthalate) material, wherein silica, calcium carbonate, barium sulfate, and kaolin are added to make the refractive index 1.4. In the present embodiment, the thickness h of the microlens is 7 μm, so that the curvature radius R of the microlens is 18.512 μm, and the focal length f of the microlens is 37.545 μm. And because the thickness h of the micro lens is 7 microns, and the distance from the top of the micro lens layer to the image-text layer is equal to 37.545 microns, the thickness of the imaging carrier is 30.545 microns, and for convenience of production, a 30 micron imaging carrier can be adopted.

It should be noted that, due to different materials of the imaging carriers, the refractive indexes are different, so that the curvature radius R of the microlens and the focal length f of the microlens are different, and then the microlenses with different parameters need to be selected according to different situations. Accordingly, the above numerical values are merely one embodiment, and the above numerical values are not intended to limit the present application.

Referring to fig. 4, the plurality of micro-image-text structures embedded in the image-text layer are represented by characters "H", and as an embodiment, the micro-image-text structures in the image-text layer and the micro-lenses in the micro-lens layer are arranged in a one-to-one correspondence in position. That is, the micro-image-text structures are also arranged in a regular hexagonal staggered arrangement mode and are arranged in one-to-one correspondence with the micro lenses in position. Of course, the micro-graphic structure may be any other characters or micro-patterns, and the application is not limited.

It should be noted that the final imaging effect of the optical watermark imaging device depends on the difference of the arrangement period of the microlens layer and the image-text layer. Specifically, the magnification of the image-text layer is

In the formula (3), w represents the magnification of the graphic layer, a represents the arrangement period of the micro graphic structure, and b represents the arrangement period of the micro lenses.

Illustratively, when the period of the arrangement of the microlens layer is 30 micrometers, the period of the microimage-text structure may be 29.85 micrometers, and the corresponding magnification is approximately 200 times.

The microlens layer and the image-text layer are both subjected to direct-writing photoetching. The photoetching machine used in the embodiment of the application can manufacture a micro-nano structure with the precision of 100 nanometers by adopting the 'concentrated high energy beam' addressable to 40 nanometers, and the photoetching depth is 7 micrometers at most. Wherein the photoetching depth of the micro graph-text structure is 1.5 microns.

The optical watermark imaging device 100 can realize imaging of points at different positions on a focal plane, when observing at a normal viewing angle, the image formed by the microlens is at the focal point of the microlens, and when the viewing deflection angle is θ, the distance from the imaging position to the focal point is:

L₁＝f×tan(θ) (4)

in the formula (4), L₁F is the focal length of the micro lens, and theta represents the viewing angle of the human eye.

When the observation sight of human eyes is different, the micro-lens layer can present different images, and because the size of the micro-lens is a micron-level structure, each imaging point corresponding to the micro-lens can present a complete image, and the problem of insufficient pixels can not occur. Therefore, in the embodiment of the present application, the watermark encoding pattern is hidden in the image-text layer by using the imaging characteristic of the microlens layer, thereby improving the security of the whole optical watermark imaging device.

The encoding method of the watermark encoding pattern will be described in detail below.

The image-text layer provided by the embodiment of the application is embedded with a plurality of micro image-text structures, each micro image-text structure is provided with n coding regions, the setting positions of the n coding regions arranged in each micro image-text structure are the same, and the n coding regions in each micro image-text structure correspond to the imaging of one pixel point; and combining pixel points corresponding to the n coding regions in each micro-image-text structure to form a watermark coding pattern. And one pixel point in the watermark coding pattern corresponds to one or more micro-image-text structures.

For example, assuming that the watermark encoding pattern shown in fig. 2 has a size of 640 × 640, at least 640 × 640 microlenses are required to decrypt the rose pattern. Whereas the area of the optical watermark imaging device is typically 9 x 9 cm, assuming that the period of the microlens layer is 30 μm, the number of microlenses will be greater than 3000 x 3000, which obviously allows hiding of the watermark encoding pattern shown in fig. 2, and this solution also has the advantage of encrypting high resolution patterns. When the number of the pixel points of the watermark coding pattern is basically consistent with that of the micro lenses of the micro lens layer, one pixel point in the watermark coding pattern corresponds to one micro image-text structure, and when the number of the pixel points of the watermark coding pattern is far smaller than that of the micro lenses of the micro lens layer, one pixel point in the watermark coding pattern corresponds to a plurality of micro image-text structures. For example, if the size of the watermark encoding pattern is 640 x 640 and the number of microlenses is greater than 3000 x 3000, then a pixel in the watermark encoding pattern may correspond to 4 microlenses. That is, four microlens images decrypt one identical pixel.

In the embodiment of the application, the n encoding regions arranged in each micro-image-text structure are obtained by converting the watermark encoding pattern through an n × m boolean matrix.

Wherein n represents the number of parts for dividing each pixel point in the watermark coding pattern into coding regions; m represents a pixel point of each coding region. For example, n may be 2 or 3, and m may be 4 or 6, which is not limited in this application.

In particular, the simplest model of the visual coding problem is to assume that the secret information is a combination of a series of black and white pixels, each of which is processed separately. Each original pixel is divided into n encoded regions (one encoded region corresponding to a transparent film) each containing m pixels, and the black and white pixels printed on the transparent film are very similar to each other, so that the human visual system averages their own black or white contributions. The structure obtained by processing an original pixel as described above can be described as an n × m boolean matrix S ═ S_ij]When the jth pixel on the ith transparent film is black, s_ij1. When i is₁,i₂,...i_rWhen the pixels are aligned and overlapped, a combined coding region can be obtained, and the black and white of the combined coding region pass through i₁,i₂,...i_rThe m column vectors are obtained by Boolean OR operation and are set as H (V), d is more than or equal to 1 and less than or equal to m which meet a fixed threshold, when H (V) and more than or equal to d, the color is judged to be black through human vision, when H (V) and more than or equal to d-am is judged to be white (a is more than or equal to 0), and further, the color difference can be judged by setting the relative difference between d and a. It should be explained that the above formula is a formula for determining black and white by human vision through boolean matrix, for example, 7 of 10 pixels are black, the whole human vision feels black, but 6 pixels are black, human vision cannot be determined to be white, and the above formula well solves the problemThe formula can be used for specifically combining experiments to realize the judgment of black and white by human vision, for example, 10 pixel points, the vision perception experiment judges that 7 pixel points are black when being black, 3 pixel points are white when being black, then d is 7, and a is 0.4, and the formula can be well combined with the experiments to realize the judgment of Boolean or result black and white by a human matrix.

In the following, n is 2 and m is 4. That is, at this time, each of the micro-image-text structures is provided with 2 encoding regions, and each encoding region is composed of 4 pixels (as shown in fig. 1). That is, the structure can be described as a 2 × 4 boolean matrix S ═ S_ij]When holding a handle i₁,i₂When the coding areas of the two views are aligned and overlapped, a combined coding area can be obtained. The combined black and white (black is 1, white is 0) pass i of the encoded region₁,i₂The Boolean OR operation of the column vector results in H (V). For H (V) ≧ 4 which satisfies the fixed threshold, the judgment by human vision is black, and when H (V) ≦ 4 is black and white, the specific implementation procedure adopts a black-and-white pattern. Here black represents the dyed area of the image-text layer (which needs to be dyed black) and white represents the transparent area.

Specific Boolean matrix D_tOne implementation algorithm of (1) is:

wherein, 1 represents black, 0 represents white, that is, 1 represents the upper color part in the graphics context layer, and 0 is the transparent part without coloring. D₁And D₀Representing two different encoding schemes corresponding to the result of decryption, by Boolean OR operation for D₁H (v) ═ 4, for D by boolean or operation₀H (v) ═ 2. D is selected when the pixel point of the watermark coding pattern is 1₁D is selected when the pixel point of the watermark coding pattern is 0₀And further accords with the judgment of human vision.

At this time, the visual cryptography scheme defining (k, n) includes two sets, i.e., includes a Boolean matrix set C₀And C₁C above₀And C₁Is a Boolean matrix D₁And D₀A set of column-switched and row-switched matrices. Selecting C when the pixel value is 1₁One Boolean matrix in the set, otherwise C is selected₀. It should be explained that (k, n) belongs to the standard definition of key sharing in cryptography, that is, secret information is divided into n shares, and decryption can be completed only when k shares or more are included.

C above₀And C₁The boolean matrix set needs to satisfy three conditions:

1. for C₀Any k rows in any matrix S, S are OR-ed to satisfy H (V)<d-a。

2. For C₁And any k rows in the arbitrary matrix S, S satisfy H (V) ≧ d.

3. Satisfy q for {1,2<Any subset of k i₁,i₂,...,i_qQ m matrix D_tThe two sets (where t e (0,1)) are indistinguishable in the sense that their probabilities of containing the same matrix are equal.

That is, in order to further improve security, in the encoding scheme for implementing the visual cipher, the present invention implements the encoding process using Matlab (a commercial mathematical software) program, and for each pixel in fig. 2, C is selected when the pixel value is 1₁One Boolean matrix in the set, otherwise C is selected₀The selection process of one boolean matrix in the set is realized by the Matlab program and can be completely random. Shown in FIG. 1 as C₀In the case of a boolean matrix in the set of boolean matrices, the first row of data of the boolean matrix corresponds to the left coding region in fig. 1, and the second row of data of the boolean matrix corresponds to the right coding region in fig. 1. When the two coding regions are combined, the pixels which are seen by human eyes are white. Referring to fig. 5 and 6, fig. 5 is a partial effect diagram of a focusing position of a first encoding region disposed in each micrograph structure, and fig. 6 is a partial effect diagram of a focusing position of a second encoding region disposed in each micrograph structure. ByThe figure shows that the encoding at a single view is completely random, and the encoding scheme under this principle has mathematical absolute security.

Furthermore, it should be noted that the embedding of the watermark encoding pattern is to embed the encoded information into the micro-teletext structure. In the microlens imaging structure, the image-text layer is an 'H' character pattern with the period of 29.85, two conditions of photoetching coloring and non-coloring exist at the corresponding coding position, the structure of the microimage-text is not changed when the coding information and the coding information are colored, the information of the microimage-text at the position is changed when the coding information and the microimage-text at the position are opposite, the precision of the structure of the microimage-text is a square with the size of 1 x 1 micron, the embedding of the watermark coding pattern has little damage to the original pattern, the imaging effect of the original pattern is not influenced at other visual angles through microlens imaging, and the microlens imaging structure has the advantages of high safety and good compatibility.

In the embodiment of the present application, the setting positions of the coding regions set in each micro graphic and text structure are:

L＝f×tan(θ) (5)

in the formula (5), L is the distance from the focal point of the imaging position, f is the focal length of the microlens, and θ represents the viewing angle of the human eye.

When 2 coding regions are arranged in the micro-image-text structure, in the embodiment of the application, the human eye view angle corresponding to the arrangement position of the first coding region in each micro-image-text structure is 30 degrees, and the human eye view angle corresponding to the arrangement position of the second coding region in each micro-image-text structure is 35 degrees.

The watermark coding pattern is obtained by superposing the imaging results of the micro-lens on the coded micro-image and text under the visual angles of 30 degrees and 35 degrees, and the visual angle difference should satisfy the formula

σl＝f×tan(θ₁)-f×tan(θ₂) (7)

Wherein σ l is the distance between the image points at two viewing angles, when the viewing angle is 30 degrees and 35 degrees, and F is 37.5, σ l is 4.6, the encoding precision of the image-text layer is 1 × 1 micrometer, each encoding content is 2 × 2, and the two encoding contents are adjacent. Through inspection, when the visual angle is deviated to 5 degrees, the visual persistence effect is obvious, the superposition of the key can be completed through the visual persistence effect, and the key can be completed when the visual angle moves under the angles of 30 degrees and 35 degrees. Finally, the rose shown in fig. 2 can be clearly seen from the associative function of the brain, and the acquisition of the watermark coding pattern is completed.

Of course, in other embodiments, the human eye view angle corresponding to the setting position of the coding region of each micro-image-text structure may be set according to different situations, for example, may also be 40 degrees, and the application is not limited in this application.

Referring to fig. 7, based on the same inventive concept, an anti-counterfeit device 200 according to an embodiment of the present application includes a main body 300 and the optical watermark imaging apparatus 100 provided in the above embodiment and disposed on the main body 300.

The main body can be, but is not limited to, a stamping film, paper currency, a certificate card, and the like.

In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.

The above description is only an example of the present application and is not intended to limit the scope of the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.