Optical imaging film with anti-copying characteristic, preparation method of optical imaging film and anti-counterfeiting product

Abstract

The invention relates to an optical imaging film with an anti-copying characteristic, a preparation method of the optical imaging film and an anti-counterfeiting product. The optical imaging film comprises: a transparent spacer layer having two opposite surfaces; the micro-focusing unit array layer is positioned on one surface of the transparent spacing layer and comprises a plurality of micro-focusing units which are arranged in an array; the micro image-text layer is located on the other surface of the transparent spacing layer and comprises a plurality of micro image-text units arranged in an array mode, and the micro image-text units and the micro focusing units are correspondingly arranged; the front view graph of the micro image-text unit is obtained based on the three-dimensional real object image and the virtual image, so that only part of the three-dimensional real object image is presented in a specific view angle range, and the part, shielded by the virtual image, of the three-dimensional real object image is not displayed. According to the anti-copying optical imaging thin film, only part of the three-dimensional real object image is presented in a specific visual angle range, and the part, shielded by the virtual image, of the three-dimensional real object image is not displayed, so that a copied image cannot carry all information of the optical imaging thin film, and the anti-copying function is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of security and anti-counterfeiting, and in particular to an optical imaging film with anti-copying properties, a preparation method thereof and an anti-counterfeiting product. Background Art

[0002] Counterfeit and imitation products have seriously damaged the legitimate rights and interests of product producers and users. With the rapid development of the economy, products on the market have become more abundant and diverse, and the demand for authenticity identification and production link traceability has become stronger.

[0003] Optical imaging films based on the principle of integrated imaging are widely used in the field of security and anti-counterfeiting. Among them, the integrated imaging stereoscopic display technology based on microlens or cylindrical lens arrays can be traced back to the integrated photography technology proposed by G. Lippman in 1908. He proposed that a series of lens groups could be used to record the same scene, so that each lens could record the corresponding sub-image, and the angle of each sub-image recorded would vary slightly. When displaying, you only need to place the recorded light field image array behind a lens group with the same parameters to observe the three-dimensional image. This process does not require coherent light or polarized light illumination and can be directly observed. The three-dimensional scene recording and reproduction process Figure 1 In addition to microlens arrays, microhole arrays can also be used as light control elements for integrated imaging.

[0004] Traditional optical imaging films based on the principle of integrated imaging all reconstruct the target object within a certain viewing angle range by setting up transmissive or reflective microlens elements to match the image and text. However, the structure of traditional optical imaging films based on the principle of integrated imaging has two defects: First, it can be copied. This solution forms a real image in the observation area, and the printed pattern of the integrated imaging film at a specific angle can be copied with high fidelity through a high-precision scanner; second, it can be copied. Practitioners with certain integrated imaging expertise can digitally reconstruct the three-dimensional object model based on the multi-angle information presented by the printed image, and render the light field image based on the traditional light field acquisition process to imitate the integrated imaging three-dimensional printed film. Therefore, in anti-counterfeiting applications, images that can be observed by the naked eye must be shocking, the complete three-dimensional information cannot be obtained by the naked eye, and cannot be optically scanned and copied.

[0005] The scanning and copying optical system of a scanner or printer mainly exposes the original through various optical elements to form a light image, and transmits the light image to the surface of the photosensitive drum with a uniform charge, so that it forms an electrostatic latent image corresponding to the light and dark of the original image. Existing scanners or printers have high optical resolution and can easily copy and print flat anti-counterfeiting images printed by traditional ink to a certain extent.

[0006] In order to further improve the anti-counterfeiting ability, researchers have proposed an optical anti-counterfeiting method based on micro-nano structures. Optical anti-counterfeiting features refer to the different image features of the observed object when light is irradiated from different angles, or when the observed object is observed from different angles. The images seen on printed products made using optical anti-counterfeiting feature technology have a dynamic changing effect. The current mainstream optical anti-counterfeiting is based on the three-dimensional surface texture of micro-nano structures to achieve optical modulation of light waves, which can produce optical effects that ordinary objects cannot show. For example, micro-optical components can display images that appear to move, or display images that open and close (optionally, become more visible and less visible), or display images that change color.

[0007] For example, the patterned nanostructure on the microstructure proposed by Nano Technology Security Co., Ltd.'s patent US20200341174A1, the optical anti-counterfeiting elements and anti-counterfeiting products proposed by China Banknote Special Anti-Counterfeiting Technology Co., Ltd.'s patent CN112572015B, and the anti-counterfeiting card and its production method proposed by Soochow Weige Technology Group's patent CN107481612A, etc., are almost mainly based on the design of micro-nano structures to achieve the refraction and manipulation of light to form different colors or display effects.

[0008] The optical anti-counterfeiting effect of this anti-counterfeiting technology can be copied to a certain extent. For example, if the optical color or pattern is viewed from a top view, it can still achieve a light and dark gradient approximation effect through scanning and printing; if it is a dynamic three-dimensional pattern type optical anti-counterfeiting effect, it can still be reversed and modeled based on the full picture of the pattern obtained by scanning and printing from a top view, so as to imitate it. Therefore, the existing means cannot accurately prevent anti-copying scanning and imaging at a top view angle, and cannot guarantee the highest degree of anti-counterfeiting security. And if it is a solution with three-dimensional surface textures, it still has the possibility of being copied and scanned by means of high-precision scanners or copying technologies. For example, advanced optical scanning systems can realize micron-level pattern scanning functions, which are based on the use of triangulation methods: that is, the data projected on the surface of the object and reflected and received is measured (not the object itself). The laser beam / or LED beam is projected onto the surface of the workpiece and received by the receiving camera next to the projection lens, that is, the position-resolving photodiode or CCD line. When the distance between the workpiece and the projection lens changes, the light reflection angle also changes, resulting in a change in the position of the received image. Based on the principle of trigonometric function, the distance between the workpiece and the projection lens is accurately calculated. The image receiver is composed of optical sensitive elements that can determine the position of the reflected light spot on the image. Based on the image position, the distance between the projection lens and the workpiece is calculated. Summary of the invention

[0009] Based on this, it is necessary to provide an optical imaging film with anti-copying properties, a preparation method thereof, and an anti-counterfeiting product in order to achieve the anti-copying function.

[0010] An optical imaging film with anti-copying characteristics, the optical imaging film comprising:

[0011] A transparent spacer layer having two opposite surfaces;

[0012] A micro-focusing unit array layer located on one surface of the transparent spacer layer, the micro-focusing unit array layer comprising a plurality of micro-focusing units arranged in an array; and

[0013] A micro-graphic layer located on the other surface of the transparent spacer layer, the micro-graphic layer comprising a plurality of micro-graphic units arranged in an array, and a plurality of the micro-graphic units are correspondingly arranged with a plurality of the micro-focusing units;

[0014] Wherein, the front view pattern of the micro-graphic unit is obtained based on a three-dimensional real object image and a virtual image, so that only a part of the three-dimensional real object image is presented within a specific viewing angle range, and the part of the three-dimensional real object image blocked by the virtual image is not displayed.

[0015] For the anti-copying optical imaging film applying the technical solution of the present invention, since only a part of the three-dimensional real object image is presented within a specific viewing angle range and the part of the three-dimensional real object image blocked by the virtual image is not displayed, the copied image cannot carry all the information of the optical imaging film, thereby realizing the functions of anti-copying and non-invertible reverse modeling.

[0016] In a feasible implementation manner, the front view pattern of the micro-graphic unit is a pattern obtained after the light field image unit of the three-dimensional real object image corresponding to the micro-focusing unit is tangent to the light field image unit of the virtual image.

[0017] In a feasible implementation manner, the obtaining of the light field image unit of the three-dimensional real object image includes: generating M*N viewpoints according to the number of pixels M*N of the micro-graphic unit; collecting the three-dimensional real object image at each viewpoint to obtain M*N parallax images P ij , 0≤i<M, 0≤j<N; sampling and extracting pixels from a preset same position of the M*N parallax images P ij and sequentially putting them into the light field image unit of the three-dimensional real object image;

[0018] The obtaining of the light field image unit of the virtual image includes: generating M*N viewpoints according to the number of pixels M*N of the micro-graphic unit; collecting the virtual image at each viewpoint to obtain M*N parallax images Q ij , 0≤i<M, 0≤j<N; sampling and extracting pixels from a preset same position of the M*N parallax images Q ij and sequentially putting them into the light field image unit of the virtual image.

[0019] In a feasible implementation, the acquisition of the front view image of the micro-graphic unit includes: the pixel point of the micro-graphic unit and the center of the micro-focusing unit form a light ray, and the light ray is refracted after passing through the micro-focusing unit. If the light ray passes through the virtual image and intersects with the three-dimensional real image, the color value of the farthest point intersecting with the three-dimensional real image is returned; if the light ray does not intersect with the three-dimensional real image after passing through the virtual image, a null value is returned; if the light ray does not pass through the virtual image, the color value of the farthest point intersecting with the three-dimensional real image is returned.

[0020] In a feasible implementation, the virtual image has a hollow portion, and the hollow portion does not block the three-dimensional real image.

[0021] In a feasible implementation, the micro-image unit has a concave-convex structure along a cross section perpendicular to the surface of the transparent spacer layer;

[0022] The micro-focusing unit is a micro-lens, a micro-mirror or a hole array structure.

[0023] In a feasible implementation, a reflective layer is provided on a side of the micro-focusing unit array layer away from the micro-image layer.

[0024] A method for preparing any of the above-mentioned optical imaging films with anti-copying properties comprises the following steps:

[0025] A micro-focusing unit array layer and a micro-image layer are formed on two surfaces of the transparent spacer layer, respectively, wherein the micro-focusing unit array layer includes a plurality of micro-focusing units arranged in an array, and the micro-image layer includes a plurality of micro-image units arranged in an array, and a plurality of the micro-image units are arranged correspondingly to a plurality of the micro-focusing units, to obtain an optical imaging film;

[0026] The front view image of the micro-graphic unit is obtained based on the three-dimensional real image and the virtual image, so that only part of the three-dimensional real image is presented within a specific viewing angle range, and the part of the three-dimensional real image blocked by the virtual image is not displayed.

[0027] The preparation methods of the optical imaging film with anti-copying properties of the above-mentioned technical solutions of the present invention are simple and feasible. In the prepared optical imaging film, only part of the three-dimensional real image is presented within a specific viewing angle range, and the part of the three-dimensional real image blocked by the virtual image is not displayed. Therefore, the copied image cannot carry all the information of the optical imaging film, thereby realizing the functions of anti-copying and inability to reverse model.

[0028] In a feasible implementation, the front view image of the micro-image unit is a image obtained by tangently connecting the light field image unit of the three-dimensional real image and the light field image unit of the virtual image corresponding to the micro-focusing unit.

[0029] In a feasible implementation, a mold for preparing a micro-graphic layer is used to form the micro-graphic layer. The preparation method of the mold for preparing the micro-graphic layer includes the following steps:

[0030] S1: Design a three-dimensional physical image and a virtual image, and the virtual image occludes part of the three-dimensional physical image within a specific viewing angle range;

[0031] S2: Set the parameters of the micro-focusing unit array layer. The parameters include the number L of micro-focusing units ij , 0 ≤ i < X, 0 ≤ j < Y, period, refractive index, and focal length; set the viewing distance and image resolution; thereby calculate the number of pixels M*N of the micro-graphic unit, generate M*N viewpoints, and determine the position of the virtual camera;

[0032] S3: Acquire the three-dimensional physical image at each viewpoint to obtain M*N three-dimensional physical image parallax images P ij , 0 ≤ i < M, 0 ≤ j < N; acquire the virtual image at each viewpoint to obtain M*N virtual image parallax images Q ij , 0 ≤ i < M, 0 ≤ j < N;

[0033] S4: Obtaining the front view pattern of the micro-graphic unit corresponding to the micro-focusing unit L 00 includes: Sampling and extracting pixels from a preset same position of the three-dimensional physical image parallax images {P 00 , P 01 , … P MN} and sequentially placing them into the light field image unit of the three-dimensional physical image; Sampling and extracting pixels from a preset same position of the virtual image parallax images {Q 00 , Q 01 , … Q MN} and sequentially placing them into the light field image unit of the virtual image; The light field image unit of the three-dimensional physical image is tangent to the light field image unit of the virtual image;

[0034] S5: Repeat step S4 to complete the acquisition of the front view patterns of all micro-graphic units;

[0035] S6: After performing photolithography, development, and metal growth on the substrate in sequence, a mold for preparing a micro-graphic layer is obtained.

[0036] In a feasible implementation, obtaining the front view pattern of the micro-graphic unit includes: A light ray is formed between the pixel point of the micro-graphic unit and the center of the micro-focusing unit. After passing through the micro-focusing unit, the light ray refracts. If the light ray passes through the virtual image and intersects with the three-dimensional physical image, return the color value of the farthest intersection point with the three-dimensional physical image; If the light ray does not intersect with the three-dimensional physical image after passing through the virtual image, return a null value; If the light ray does not pass through the virtual image, return the color value of the farthest intersection point with the three-dimensional physical image.

[0037] In a feasible implementation manner, a mold for preparing a micro-graphic layer is used to form the micro-graphic layer. The preparation method of the mold for preparing the micro-graphic layer includes the following steps:

[0038] S1: Design a three-dimensional physical image and a virtual image, and the virtual image遮挡部分所述立体实物像 within a specific viewing angle range;

[0039] S2: Set the parameters of the micro-focusing unit array layer, and the parameters include the number L of micro-focusing units ij , 0 ≤ i < X, 0 ≤ j < Y, period, refractive index, and focal length; Set the viewing distance and image resolution; Thus, calculate the number of pixels M*N of the micro-graphic unit;

[0040] S3: The pixel points of the micro-graphic unit and the centers of the corresponding micro-focusing units form light rays. After passing through the micro-focusing units, the light rays are refracted. If the light rays pass through the virtual image and intersect with the three-dimensional physical image, return the color value of the farthest intersection point with the three-dimensional physical image; If the light rays do not intersect with the three-dimensional physical image after passing through the virtual image, return a null value; If the light rays do not pass through the virtual image, return the color value of the farthest intersection point with the three-dimensional physical image; Traverse all pixel points in the micro-graphic unit to obtain the front view pattern of the micro-graphic unit;

[0041] S4: Repeat step S3 to complete the acquisition of the front view patterns of all micro-graphic units;

[0042] S5: After performing photolithography, development, and metal growth on the substrate in sequence, obtain a mold for preparing the micro-graphic layer.

[0043] In a feasible implementation manner, the following step is further included: Form a reflective layer on the side of the micro-focusing unit array layer away from the micro-graphic layer.

[0044] An anti-counterfeiting product includes the optical imaging film with anti-copying characteristics as described above.

[0045] For the anti-counterfeiting product applying the technical solution of the present invention, since the anti-copying optical imaging film only presents a part of the three-dimensional physical image within a specific viewing angle range, and the part of the three-dimensional physical image blocked by the virtual image is not displayed, the copied image cannot carry all the information of the optical imaging film, thus realizing the functions of anti-copying and irreversible reverse modeling.

[0046] In view of the problem of anti-copying, the present invention proposes a method for encoding space objects using computational graphics reverse ray tracing technology based on the stereoscopic image display principle of a four-dimensional light field model. By setting multiple digital three-dimensional objects with different reflective and transmissive properties in digital space, the first type is a three-dimensional object distribution (three-dimensional text, image and complex morphology distribution) with natural reflective properties, that is, a three-dimensional real image, and the second type is a virtual object that is completely non-reflective and non-transmissive, which can be a graphic with a plane distribution or a three-dimensional distribution, that is, a virtual image. When performing light field computational imaging based on a micro-focusing array, the information of the virtual object and the three-dimensional real image are imaged on a plane near the focal plane (outside and inside) of the micro-focusing unit array layer, forming a complex micro-structure computational distribution, and the relative position relationship between the two is matched according to the ray tracing design. Therefore, the three-dimensional real image of the blocked part is selectively blocked by the virtual image at the front view and / or the top view. Therefore, the optical imaging film prepared by this method has the function of anti-copying and inability to reversely model. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic diagram of the traditional integrated imaging stereo display;

[0048] Figure 2 is a schematic diagram of an optical imaging film according to one embodiment of the present invention;

[0049] Figure 3 A front view of a three-dimensional image presented by an optical imaging film according to an embodiment of the present invention;

[0050] Figure 4 This is a tilted viewing angle diagram of a three-dimensional image presented by an optical imaging film according to one embodiment of the present invention;

[0051] Figure 5 Observation diagrams of a three-dimensional image presented by an optical imaging film according to an embodiment of the present invention from different viewing angles;

[0052] Figure 6 Observation diagrams of a stereoscopic image presented by an optical imaging film according to another embodiment of the present invention from different viewing angles;

[0053] Figure 7 A schematic diagram of a three-dimensional image presented by an optical imaging film according to another embodiment of the present invention;

[0054] Figure 8 A schematic diagram of a three-dimensional image presented by an optical imaging film according to another embodiment of the present invention;

[0055] Figure 9(a) to Figure 9(d) Observation diagrams of a three-dimensional image presented by an optical imaging film according to an embodiment of the present invention from different viewing angles;

[0056] Figure 10(a) to Figure 10(c)Observation diagrams of a three-dimensional image presented by an optical imaging film according to an embodiment of the present invention from different viewing angles;

[0057] Figure 11(a) to Figure 11(c) Observation diagrams of a three-dimensional image presented by an optical imaging film according to an embodiment of the present invention from different viewing angles;

[0058] Fig.12 This is a schematic diagram of the intersection of light and a three-dimensional real image and a virtual image in the process of obtaining a front view image of a micro-image unit in an optical imaging film with anti-copying properties according to an embodiment of the present invention;

[0059] Fig.13 This is a schematic diagram of the intersection of light and a three-dimensional real image and a virtual image in the process of obtaining a front view image of a micro-graphic unit in an optical imaging film with anti-copying properties according to another embodiment of the present invention;

[0060] Fig.14 This is a flow chart of a method for preparing a mold for preparing a micro-graphic layer according to an embodiment of the present invention;

[0061] Fig.15 A flow chart of a method for preparing a mold for preparing a micro-image layer according to another embodiment of the present invention;

[0062] Fig.16 A front view of a micro-graphic unit in an embodiment of the present invention during a process of obtaining a front view image;

[0063] Fig.17 A schematic diagram of a specific angle during the acquisition process of a front view image of a micro-graphic unit according to an embodiment of the present invention;

[0064] Fig.18 It is a schematic diagram taking the front view angle as an example of the process of acquiring the front view image of the micro-graphic unit according to one embodiment of the present invention. DETAILED DESCRIPTION

[0065] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0066] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0067] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0068] The structure of the optical imaging film with anti-copying properties of the present invention can be refractive or reflective. The refractive type refers to that the micro-focusing unit array layer is on the top and the micro-graphic layer is on the bottom, and when observing the graphics, one looks down from the top in the direction of the micro-focusing unit array layer. The reflective type is based on the refractive structure, in which the micro-focusing unit array layer and the micro-graphic layer are arranged in reverse, and a reflective film is added to the surface of the micro-focusing unit array layer.

[0069] See also Figure 2 , an optical imaging film 100 with anti-copying properties in one embodiment includes a transparent spacer layer 110, a micro-focusing unit array layer 120 and a micro-image layer 130. The transparent spacer layer 110 has two opposite surfaces, and the material of the transparent spacer layer 110 can be PET or UV glue. The micro-focusing unit array layer 120 is located on one surface of the transparent spacer layer 110. Specifically in this embodiment, the micro-focusing unit array layer 120 is located on the upper surface of the transparent spacer layer 110. Further, the micro-focusing unit array layer 120 includes a plurality of micro-focusing units 121 arranged in an array. The micro-image layer 130 is located on the other surface of the transparent spacer layer 110. Specifically in this embodiment, the micro-image layer 130 is located on the lower surface of the transparent spacer layer 110. Further, the micro-image layer 130 includes a plurality of micro-image units 131 arranged in an array. The plurality of micro-image units 131 are arranged correspondingly to the plurality of micro-focusing units 121.

[0070] In the optical imaging film 100 with anti-copying properties of the above embodiment, the front view image of the micro-graphic unit 131 is obtained based on the three-dimensional real image 132 and the virtual image 133, so that only part of the three-dimensional real image 132 is presented within a specific viewing angle range, and the part of the three-dimensional real image 132 blocked by the virtual image 133 is not displayed. Figure 3 and Figure 4As shown. Among them, the specific viewing angle range refers to the viewing angle range of the observer. The present invention does not limit the specific angles of the specific viewing angle range, which can be set according to actual needs. When applying the anti-copy optical imaging film of this embodiment, since only part of the three-dimensional physical image is presented within the specific viewing angle range, and the part of the three-dimensional physical image blocked by the virtual image is not displayed, the copied image cannot carry all the information of the optical imaging film, thus realizing the functions of anti-copying and non-invertible reverse modeling.

[0071] Please refer to Figure 3 and Figure 4 , in the optical imaging film with anti-copying characteristics according to an embodiment of the present invention, the front view pattern of the micro-graphic unit is a pattern obtained by tangency of the light field image unit corresponding to the three-dimensional physical image 132 under the corresponding micro-focusing unit and the light field image unit of the virtual image 133. Only part of the three-dimensional physical image 132 is displayed within the specific viewing angle range, and the part of the three-dimensional physical image 132 blocked by the virtual image 133 is not displayed. Among them, the virtual image 133 is located above the three-dimensional physical image 132. Specifically, the three-dimensional physical image 132 is 100 RMB, and the virtual image 133 is a frustum structure, and the surface of this frustum structure absorbs all light and does not reflect any light. Since only part of the three-dimensional physical image 132 is presented within the specific viewing angle range, and the part of the three-dimensional physical image 132 blocked by the virtual image 133 is not displayed, the copied image cannot carry all the information of the optical imaging film, thus realizing the functions of anti-copying and non-invertible reverse modeling. It should be noted that in the illustration of the present invention, the virtual image is shown for easy understanding, but in actual observation, the virtual image is invisible.

[0072] Please refer to Figure 5 , by observing the optical imaging film with anti-copying characteristics of the above embodiment from different viewing angles, different angle information of the three-dimensional image can be seen, achieving the purpose of being observable by the naked eye, having a shocking effect, being unable to obtain complete three-dimensional information by the naked eye, and being unable to be optically scanned and copied.

[0073] On the basis of the foregoing embodiment, the acquisition of the light field image unit of the three-dimensional physical image 132 includes: generating M*N viewpoints according to the number of pixels M*N of the micro-graphic unit 131; collecting the three-dimensional physical image 132 at each viewpoint to obtain M*N disparity images P ij , 0≤i<M, 0≤j<N; sampling and extracting pixels at a preset same position from the M*N disparity images P ij and sequentially placing them into the light field image unit of the three-dimensional physical image.

[0074] At the same time, the acquisition of the light field image unit of the virtual image 133 includes: generating M*N viewpoints according to the number of pixels M*N of the micro-graphic unit 131; collecting the virtual image 133 at each viewpoint to obtain M*N disparity images Q ij, where \(0\leq i < M\) and \(0\leq j < N\); sampling and extracting pixels from the same preset position of \(M\times N\) parallax images \(Q\) ij and sequentially placing them into the light field image units of the virtual image in order.

[0075] On the basis of the foregoing embodiment, a physical image for interference can also be superimposed on the virtual image, such as Figure 6 shown. In one embodiment, the physical image for interference is a five-pointed star logo, which can prevent the three-dimensional physical image of "100RMB" from being observed and scanned from directly above, and can achieve a more obvious anti-copying effect. Of course, the physical image for interference can also be an image of other shapes.

[0076] It should be noted that in the optical imaging film with anti-copying characteristics of the present invention, the three-dimensional physical image and the virtual image can be any pattern, and the positional relationship between the three-dimensional physical image and the virtual image is not limited to this embodiment. The virtual image can also be located on one side of the three-dimensional physical image or within the three-dimensional physical image.

[0077] Please refer to Figure 7 . In another embodiment of the optical imaging film with anti-copying characteristics of the present invention, the three-dimensional physical image 132 "RMB100" is distributed around the mushroom-shaped virtual image 133. Since the surface of the virtual image 133 does not reflect light, when copying, all information of the anti-copying image "RMB100" cannot be obtained.

[0078] In the optical imaging film of the above embodiment, the surface of the three-dimensional physical image is fully diffuse reflection, and the surface of the virtual image does not reflect light but has a shielding property.

[0079] Please refer to Figure 8 . In another embodiment of the optical imaging film with anti-copying characteristics of the present invention, there are two three-dimensional physical images 132, which are the letter "R" and the letter "Y" respectively. The virtual image 133 is located between the two three-dimensional physical images 132, and the virtual image 133 blocks the letter "R" and the letter "Y". When the viewing angle changes, sometimes the letter "R" can be seen, and sometimes the letter "Y" can be seen. Among them, the surface of the three-dimensional physical image 132 is diffuse reflection, all sides of the virtual image 133 are non-transmissive, the upper surface of the virtual image 133 is transmissive, but the letter "R" and the letter "Y" have a shielding property.

[0080] In the optical imaging film with anti-copying characteristics of this embodiment, the virtual image 133 is specifically a virtual wall covering. It should be noted that for the purpose of blocking the anti-copying image, the shape of the virtual image 133 is not limited to wall-like or column-like, etc., and its shape can be arbitrarily designed.

[0081] Figure 9(a) to Figure 9(d) , Figure 10(a) to Figure 10(c) and Figure 11(a) to Figure 11(c)These are observation diagrams from different viewing angles of three-dimensional images presented in optical imaging films with anti-copying properties according to several other embodiments of the present invention.

[0082] As shown in Figure 9(a), the inner sphere and the outer frame of the cube are virtual images, and the characters "S", "V" and "G" are three-dimensional real images; Figure 9(b) is a top view, and only the character "S" can be seen when looking down; Figure 9(c) is a left view, and only the character "G" can be seen; Figure 9(d) is a right view, which is empty. The virtual image is shown in the figure for ease of understanding, but in actual observation, the virtual image is invisible.

[0083] As shown in Figure 10(a), the five-pointed star and the circle of numbers on the edge are three-dimensional real images, and the cylinder and hollow truncated cone are virtual images; Figure 10(b) is a top view, and only the five-pointed star can be seen when looking down; Figure 10(c) is a side view, and part of the numbers can be seen from a certain angle when looking from the side. In order to facilitate understanding, the virtual image is shown in the figure, but in actual observation, the virtual image is invisible.

[0084] As shown in Figure 11(a), the outer circle of characters and the five-pointed star are three-dimensional physical images, and the hollow cylinder that is narrow at the top and wide at the bottom is a virtual image; Figure 11(b) is a top view, and the deformed characters can be seen when viewed from above; Figure 11(c) is a side view, and the deformed characters can be seen from a certain angle when viewed from the side. The virtual image is shown in the figure for ease of understanding, but in actual observation, the virtual image is invisible.

[0085] In addition, it needs to be further explained that in the optical imaging film of the technical solution of the present invention, the front view image of the micro-image unit can also be obtained in other ways.

[0086] Please also see Figure 1 , Fig.12 and Fig.13 In another embodiment of the optical imaging film with anti-copying properties of the present invention, the acquisition of the front view image of the micro-image unit includes: the pixel point of the micro-image unit 131 and the center of the micro-focusing unit 121 form a light ray, and the light ray is refracted after passing through the micro-focusing unit 121. If the light ray passes through the virtual image 133 and intersects with the three-dimensional real image 132, the color value of the farthest point intersecting with the three-dimensional real image 132 is returned; if the light ray does not intersect with the three-dimensional real image after passing through the virtual image 133, a null value is returned; if the light ray does not pass through the virtual image, the color value of the farthest point intersecting with the three-dimensional real image is returned.

[0087] Specifically in this embodiment, Fig.12 and Fig.13 The arrows in the figure represent light rays. Fig.12The 3D real image 132 is located between the micro-focusing unit array layer 120 and the virtual image 133, and the micro-image layer 130 is located on the side of the micro-focusing unit array layer 120 away from the 3D real image 132. If the light does not pass through the virtual image 133, the color value of the farthest point A intersecting the 3D real image 132 is obtained. Fig.13 In the figure, the virtual image 133 is located between the micro-focusing unit array layer 120 and the three-dimensional physical image 132, and the micro-image layer 130 is located on the side of the micro-focusing unit array layer 120 away from the three-dimensional physical image 132, and the color value of the intersection B is obtained.

[0088] On the basis of the aforementioned several embodiments, the virtual image 133 has a hollow part, and the hollow part does not block the three-dimensional real image 132. When the observer observes within a specific viewing angle range, the three-dimensional real image located below the virtual image can be observed through the hollow part, which increases the difficulty of copying the image and further enhances the anti-copying function. It should be noted that the virtual image may not have a hollow part.

[0089] On the basis of the above-mentioned several embodiments, the micro-graphic unit 131 has a concave-convex structure along the cross section perpendicular to the surface of the transparent spacer layer 110; the micro-focusing unit 121 is a micro-lens, a micro-mirror or a hole array structure. Among them, the micro-lens can be a common curved lens, a cylindrical lens, a Fresnel lens, a super lens, a polarization-sensitive lens, a liquid crystal lens or a grating lens.

[0090] On the basis of the aforementioned several embodiments, a reflective layer (not shown) is disposed on the side of the micro-focusing unit array layer 120 away from the micro-image layer 130. At this time, the structure of the optical imaging film is reflective.

[0091] The optical imaging film of the present invention has the following advantages: 1. Anti-copying. Through the fusion of multiple virtual images and real images, complete information cannot be obtained at any specific angle. 2. Anti-copying. The required light field image cannot be rendered through digital modeling, so the printed image cannot be imitated. 3. Simple structure and batch production. 4. Multiple three-dimensional models are fused and designed in conjunction with the observation angle. The image changes dynamically with the observation angle, and the effect is fantastic and shocking.

[0092] A method for preparing the optical imaging film with anti-copying properties according to one embodiment of the present invention comprises the following steps:

[0093] A micro-focusing unit array layer and a micro-image layer are respectively formed on the two surfaces of the transparent spacer layer, the micro-focusing unit array layer includes a plurality of micro-focusing units arranged in an array, the micro-image layer includes a plurality of micro-image units arranged in an array, and the plurality of micro-image units are arranged correspondingly to the plurality of micro-focusing units to obtain an optical imaging film; wherein, the front view image of the micro-image unit is obtained based on a three-dimensional real image and a virtual image, so that only part of the three-dimensional real image is presented within a specific viewing angle range, and the part of the three-dimensional real image blocked by the virtual image is not displayed.

[0094] Among them, the operation of forming the micro-focusing unit array layer and the micro-image layer on the two surfaces of the transparent spacer layer respectively in one embodiment is:

[0095] S1: providing substrate;

[0096] S2: UV glue is coated on one side of the substrate, and a micro-focusing unit array layer is obtained by embossing with a micro-focusing unit array layer mold;

[0097] S3: UV glue is coated on the other side of the substrate, and a micro-nano pit structure is embossed with a micro-image layer mold. Then, ink is filled in the pit structure and scraped to obtain a micro-image layer; thereby obtaining an optical imaging film, in which the substrate serves as a transparent spacer layer.

[0098] Among them, the operation of forming the micro-focusing unit array layer and the micro-image layer on the two surfaces of the transparent spacer layer respectively in another embodiment is:

[0099] S1: providing substrate;

[0100] S2: UV glue is applied on one side of the substrate, and the micro-image layer mold is used to emboss a micro-nano pit structure, and then ink is filled in the pit structure and scraped flat to obtain the micro-image layer;

[0101] S3: coating PET or UV glue on the micro-image layer, and obtaining a micro-focusing unit array layer by embossing with a micro-focusing unit array layer mold; thereby obtaining an optical imaging film, wherein the portion between the micro-image layer and the micro-focusing unit array layer serves as a transparent spacer layer.

[0102] In the method for preparing the optical imaging film with anti-copying properties of the first embodiment of the present invention, the front view image of the micro-graphic unit is a image obtained by tangently connecting the light field image unit of the three-dimensional real image under the corresponding micro-focusing unit with the light field image unit of the virtual image.

[0103] Based on the above-mentioned embodiment, the micro-image layer is formed by using a mold for preparing the micro-image layer. Fig.14 The method for preparing a mold for preparing a micro-graphic layer comprises the following steps:

[0104] S1: Design a three-dimensional physical image and a virtual image, where the virtual image occludes part of the three-dimensional physical image within a specific viewing angle range.

[0105] S2: Set the parameters of the micro-focusing unit array layer. The parameters include the number L of micro-focusing units ij , 0 ≤ i < X, 0 ≤ j < Y, period, refractive index, and focal length; set the viewing distance and image resolution; thereby calculate the number of pixels M*N of the micro-graphic unit, generate M*N viewpoints, and determine the position of the virtual camera.

[0106] S3: Collect the three-dimensional physical image at each viewpoint to obtain M*N three-dimensional physical image parallax images P ij , 0 ≤ i < M, 0 ≤ j < N; collect the virtual image at each viewpoint to obtain M*N virtual image parallax images Q ij , 0 ≤ i < M, 0 ≤ j < N.

[0107] S4: Obtaining the front view pattern of the micro-graphic unit corresponding to the micro-focusing unit L includes: Sampling and extracting pixels from the preset same position of the three-dimensional physical image parallax images {P 00 , P 00 , … P 01} in sequence and placing them into the light field image unit of the three-dimensional physical image; Sampling and extracting pixels from the preset same position of the virtual image parallax images {Q MN , Q 00 , … Q 01} in sequence and placing them into the light field image unit of the virtual image; The light field image unit of the three-dimensional physical image is tangent to the light field image unit of the virtual image. MN} in sequence and placing them into the light field image unit of the virtual image; The light field image unit of the three-dimensional physical image is tangent to the light field image unit of the virtual image.

[0108] S5: Repeat step S4 to complete the acquisition of the front view patterns of all micro-graphic units.

[0109] S6: After lithography, development, and metal growth on the substrate in sequence, obtain a mold for preparing the micro-graphic layer.

[0110] In the preparation method of the above optical imaging film with anti-copying characteristics in the second embodiment of the present invention, obtaining the front view pattern of the micro-graphic unit includes: The pixel points of the micro-graphic unit and the center of the micro-focusing unit form a light ray. After passing through the micro-focusing unit, the light ray refracts. If the light ray passes through the virtual image and intersects with the three-dimensional physical image, return the color value of the farthest intersection point with the three-dimensional physical image; If the light ray does not intersect with the three-dimensional physical image after passing through the virtual image, return a null value; If the light ray does not pass through the virtual image, return the color value of the farthest intersection point with the three-dimensional physical image.

[0111] On the basis of the foregoing embodiment, use the mold for preparing the micro-graphic layer to form the micro-graphic layer. Please refer to Fig.15, A method for preparing a mold for preparing a micro-graphic layer includes the following steps:

[0112] S1: Design a three-dimensional physical image and a virtual image, and the virtual image occludes part of the three-dimensional physical image within a specific viewing angle range.

[0113] S2: Set the parameters of the micro-focusing unit array layer, where the parameters include the number L of micro-focusing units ij , 0 ≤ i < X, 0 ≤ j < Y, period, refractive index, and focal length; set the viewing distance and image resolution; thereby calculate the number of pixels M*N of the micro-graphic unit.

[0114] S3: The pixel points of the micro-graphic unit form light rays with the centers of the corresponding micro-focusing units. After the light rays pass through the micro-focusing units, refraction occurs. If the light rays pass through the virtual image and intersect with the three-dimensional physical image, return the color value of the farthest intersection point with the three-dimensional physical image; if the light rays do not intersect with the three-dimensional physical image after passing through the virtual image, return a null value; if the light rays do not pass through the virtual image, return the color value of the farthest intersection point with the three-dimensional physical image; traverse all pixel points in the micro-graphic unit to obtain the front view pattern of the micro-graphic unit.

[0115] S4: Repeat step S3 to complete the acquisition of the front view patterns of all micro-graphic units.

[0116] S5: After performing photolithography, development, and metal growth on the substrate in sequence, obtain a mold for preparing the micro-graphic layer.

[0117] On the basis of the above two embodiments, the method for preparing the optical imaging film further includes the following steps: form a reflective layer on the side of the micro-focusing unit array layer away from the micro-graphic layer. At this time, a reflective optical imaging film is obtained.

[0118] Please refer to Figure 16 to Figure 18 , A method for obtaining the front view pattern of a micro-graphic unit according to an embodiment of the present invention includes the following steps:

[0119] Record an image for any one viewing angle. As Fig.16 shown, it is a positive viewing angle from right to left. Along this viewing angle direction is the path. As Fig.16 shown, the first three-dimensional physical image is 1, the virtual image is 2, and the second three-dimensional physical image is 3.

[0120] Take the information of the graphic "Y" in 1 as 1-1, and the remaining information 1-2. As Fig.18 shown;

[0121] Perform an AND operation on the information of 1-2 and 2 to obtain 2-1 and the remaining information 2-2. As Fig.18 shown;

[0122] The information of 2-2 and 3 is ANDed together to obtain 3-1 and the remaining information 3-3, as Fig.18 As shown;

[0123] Obtain the recording surface 140 information 1-1 and 3-1 corresponding to the three-dimensional real image, and the recording surface 140 information 2-1 corresponding to the virtual image, and assign a null value to the virtual image recording surface 140 information to merge the images 1-1, 2-1 and 3-1;

[0124] By analogy, if there are multiple-faceted physical images and multiple-faceted virtual images, information extraction is performed starting from the face with the largest depth of field to the face with the smallest depth of field.

[0125] In the above steps, an image is recorded for any viewing angle, such as Fig.17 The shown figure is a side view from the upper right to the lower left, and the information can be recorded according to the above method.

[0126] In the above steps, according to the field of view of the micro-focusing units in the micro-focusing unit array layer 120, the information of all viewing angles of the image is recorded and combined into complete recorded information.

[0127] The method for preparing the optical imaging film with anti-copying properties of the technical solution of the present invention is simple and feasible. In the prepared optical imaging film, since only part of the three-dimensional real image is presented within a specific viewing angle range, the part of the three-dimensional real image blocked by the virtual image is not displayed, so that the copied image cannot carry all the information of the optical imaging film, thereby realizing the functions of anti-copying and inability to reverse model.

[0128] In view of the problem of anti-copying, the present invention proposes a method for encoding space objects using computational graphics reverse ray tracing technology based on the stereoscopic image display principle of a four-dimensional light field model. By setting multiple digital three-dimensional objects with different reflective and transmissive properties in digital space, the first type is a three-dimensional object distribution (three-dimensional text, image and complex morphology distribution) with natural reflective properties, that is, a three-dimensional real image, and the second type is a virtual object that is completely non-reflective and non-transmissive, which can be a graphic with a plane distribution or a three-dimensional distribution, that is, a virtual image. When performing light field computational imaging based on a micro-focusing array, the information of the virtual object and the three-dimensional real image are imaged on a plane near the focal plane (outside and inside) of the micro-focusing unit array layer, forming a complex micro-structure computational distribution, and the relative position relationship between the two is matched according to the ray tracing design. Therefore, the three-dimensional real image of the blocked part is selectively blocked by the virtual image at the front view and / or the top view. Therefore, the optical imaging film prepared by this method has the function of anti-copying and inability to reversely model.

[0129] An anti-counterfeiting product according to one embodiment includes any one of the above-mentioned optical imaging films with anti-copying properties.

[0130] The anti-counterfeiting products may be, for example, certificates, tickets, tobacco and alcohol packaging, or daily chemical packaging.

[0131] The anti-counterfeiting product using the technical solution of the present invention can prevent the copied image from carrying all the information of the optical imaging film, thereby achieving the functions of anti-copying and inability to reverse model, because the anti-copying optical imaging film only presents part of the three-dimensional real image within a specific viewing angle range, and the part of the three-dimensional real image blocked by the virtual image is not displayed.

[0132] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0133] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An optical imaging film with anti-copying properties, It is characterized in that The optical imaging film comprises: a transparent spacer layer having two opposite surfaces; a micro-focusing unit array layer, located on one surface of the transparent spacer layer, the micro-focusing unit array layer comprising a plurality of micro-focusing units arranged in an array; and A micro-image layer is located on the other surface of the transparent spacing layer, and the micro-image layer includes a plurality of micro-image units arranged in an array, and a plurality of the micro-image units are arranged correspondingly to a plurality of the micro-focusing units; The front view image of the micro-graphic unit is obtained based on the three-dimensional real image and the virtual image, so that only part of the three-dimensional real image is presented within a specific viewing angle range, and the part of the three-dimensional real image blocked by the virtual image is not displayed.

2. The optical imaging film according to claim 1, It is characterized in that The front view image of the micro-image unit is a image obtained by tangently connecting the light field image unit of the three-dimensional real image and the light field image unit of the virtual image under the micro-focusing unit.

3. The optical imaging film according to claim 2, It is characterized in that The acquisition of the light field image unit of the three-dimensional physical image includes: generating M*N viewpoints according to the number of pixels M*N of the micro-graphic unit; collecting the three-dimensional physical image at each viewpoint to obtain M*N parallax images P ij , 0 ≤ i < M, 0 ≤ j < N; sampling and extracting pixels from a preset same position of the M*N parallax images P ij and sequentially putting them into the light field image unit of the three-dimensional physical image; The acquisition of the light field image unit of the virtual image includes: generating M*N viewpoints according to the number of pixels M*N of the micro-graphic unit; collecting the virtual image at each viewpoint to obtain M*N parallax images Q ij , 0 ≤ i < M, 0 ≤ j < N; sampling and extracting pixels from a preset same position of the M*N parallax images Q ij and sequentially placing them into the light field image unit of the virtual image according to the order.

4. The optical imaging film according to claim 1, It is characterized in that The acquisition of the front view image of the micro-graphic unit includes: the pixel point of the micro-graphic unit and the center of the micro-focusing unit form a light ray, the light ray is refracted after passing through the micro-focusing unit, if the light ray passes through the virtual image and intersects with the three-dimensional real image, the color value of the farthest point intersecting with the three-dimensional real image is returned; if the light ray does not intersect with the three-dimensional real image after passing through the virtual image, a null value is returned; if the light ray does not pass through the virtual image, the color value of the farthest point intersecting with the three-dimensional real image is returned.

5. The optical imaging film according to claim 1, It is characterized in that The virtual image has a hollow portion, and the hollow portion does not block the three-dimensional real image.

6. The optical imaging film according to claim 1, It is characterized in that The micro-image unit has a concave-convex structure along a cross section perpendicular to the surface of the transparent spacer layer; The micro-focusing unit is a micro-lens, a micro-mirror or a hole array structure.

7. The optical imaging film according to claim 1, It is characterized in that A reflective layer is disposed on a side of the micro-focusing unit array layer away from the micro-image layer.

8. A method for preparing an optical imaging film having anti-copying properties according to any one of claims 1 to 7, It is characterized in that The steps include: A micro-focusing unit array layer and a micro-image layer are formed on two surfaces of the transparent spacer layer, respectively, wherein the micro-focusing unit array layer includes a plurality of micro-focusing units arranged in an array, and the micro-image layer includes a plurality of micro-image units arranged in an array, and a plurality of the micro-image units are arranged correspondingly to a plurality of the micro-focusing units, to obtain an optical imaging film; The front view image of the micro-graphic unit is obtained based on the three-dimensional real image and the virtual image, so that only part of the three-dimensional real image is presented within a specific viewing angle range, and the part of the three-dimensional real image blocked by the virtual image is not displayed.

9. The method for preparing an optical imaging film according to claim 8, It is characterized in that The front view image of the micro-image unit is a image obtained by tangently connecting the light field image unit of the three-dimensional real image and the light field image unit of the virtual image under the micro-focusing unit.

10. The method for preparing an optical imaging film according to claim 9, It is characterized in that The micro-image layer is formed by using a mold for preparing a micro-image layer. The method for preparing the mold for preparing a micro-image layer comprises the following steps: S1: Designing a three-dimensional real image and a virtual image, wherein the virtual image partially blocks the three-dimensional real image within a specific viewing angle range; S2: Set the parameters of the micro-focus unit array layer, where the parameters include the number L of micro-focus units ij , 0 ≤ i < X, 0 ≤ j < Y, period, refractive index, and focal length; set the viewing distance and image resolution; thereby calculate the number of pixels M*N of the micro-graphic unit, generate M*N viewpoints, and determine the position of the virtual camera; S3: Collect the three-dimensional physical images at each viewing point to obtain M*N three-dimensional physical image parallax images P ij , where 0 ≤ i < M and 0 ≤ j < N; collect the virtual images at each viewing point to obtain M*N virtual image parallax images Q ij , where 0 ≤ i < M and 0 ≤ j < N; S4: Microfocus Unit L 00 The acquisition of the front view image of the corresponding micro-image unit includes: obtaining the parallax image {P 00 , P 01 ,…P MN }, and sequentially put the pixels into the light field image unit of the three-dimensional real image; from the virtual image parallax image {Q 00 , Q 01 ,…Q MN }, sampling and extracting pixels at the same preset position, and sequentially placing them into the light field image unit of the virtual image; the light field image unit of the three-dimensional real image is tangent to the light field image unit of the virtual image; S5: repeat step S4 to complete the acquisition of front view graphics of all micro-graphic units; S6: After performing photolithography, development and metal growth on the substrate in sequence, a mold for preparing a micro-image layer is obtained.

11. The method for preparing an optical imaging film according to claim 8, It is characterized in that The acquisition of the front view image of the micro-graphic unit includes: the pixel point of the micro-graphic unit and the center of the micro-focusing unit form a light ray, the light ray is refracted after passing through the micro-focusing unit, if the light ray passes through the virtual image and intersects with the three-dimensional real image, the color value of the farthest point intersecting with the three-dimensional real image is returned; if the light ray does not intersect with the three-dimensional real image after passing through the virtual image, a null value is returned; if the light ray does not pass through the virtual image, the color value of the farthest point intersecting with the three-dimensional real image is returned.

12. The method for preparing an optical imaging film according to claim 11, It is characterized in that The micro-image layer is formed by using a mold for preparing a micro-image layer. The method for preparing the mold for preparing the micro-image layer comprises the following steps: S1: Designing a three-dimensional real image and a virtual image, wherein the virtual image partially blocks the three-dimensional real image within a specific viewing angle range; S2: Set the parameters of the micro-focus unit array layer, where the parameters include the number L of micro-focus units ij , 0 ≤ i < X, 0 ≤ j < Y, period, refractive index, and focal length; set the observation distance and image resolution; thereby calculating the number of pixels M*N of the micro-graphic unit; S3: The pixel point of the micro-graphic unit and the center of the corresponding micro-focusing unit form a light ray, and the light ray is refracted after passing through the micro-focusing unit. If the light ray passes through the virtual image and intersects with the three-dimensional real image, the color value of the farthest point intersecting with the three-dimensional real image is returned; If the ray does not intersect with the three-dimensional physical image after passing through the virtual image, a null value is returned; If the light does not pass through the virtual image, the color value of the farthest point intersecting with the three-dimensional real image is returned; all the pixels in the micro-image unit are traversed to obtain the front view graphics of the micro-image unit; S4: repeat step S3 to complete the acquisition of front view graphics of all micro-graphic units; S5: After performing photolithography, development and metal growth on the substrate in sequence, a mold for preparing a micro-image layer is obtained.

13. The method for preparing an optical imaging film according to claim 8, It is characterized in that The method also includes the following steps: forming a reflective layer on a side of the micro-focusing unit array layer away from the micro-image layer. 14.An anti-counterfeiting product, It is characterized in that An optical imaging film with anti-copying properties comprising any one of claims 1 to 7.

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