Optical imaging thin film having Anti-copying characteristics and preparation method therefor, and Anti-counterfeiting product

Abstract

The present invention relates to an optical imaging thin film having anti-copying characteristics and a preparation method therefor, and an anti-counterfeiting product. The optical imaging thin 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 and comprising a plurality of micro-focusing units arranged in an array; and a micro image-text layer located on the other surface of the transparent spacer layer and comprising a plurality of micro image-text units arranged in an array, wherein the plurality of micro image-text units are arranged corresponding to the plurality of micro-focusing units; and the front view of each micro image-text unit is obtained on the basis of a three-dimensional real object image and a virtual image, such that only part of the three-dimensional real object image is presented within a specific visual angle range, and the part of the three-dimensional real object image shielded by the virtual image is not displayed. According to the anti-copying optical imaging thin film of the present invention, only part of the three-dimensional real object image is presented within a specific visual angle range, and the part of the three-dimensional real object image occluded by the virtual image is not displayed, such that a copied image cannot carry all information of the optical imaging thin film, thereby achieving an anti-copying function.

Description

Optical imaging film with anti-copying properties, preparation method thereof, and anti-counterfeiting product Technical Field

[0001] The present 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 manufacturers 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 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, it is only necessary 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 is shown in 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 employ transmissive or reflective microlenses that match the image and text, reconstructing the target object within a certain viewing angle range. However, these films suffer from two structural flaws: first, they are photocopyable. This solution forms a real image in the observation area, allowing high-precision scanners to accurately copy the printed pattern of the integrated imaging film at a specific angle. Second, they are reproducible. Practitioners with specialized knowledge of integrated imaging can digitally reconstruct a 3D object model based on the multi-angle information presented by the printed image and render the light field image using traditional light field acquisition processes, replicating the 3D printed film. Therefore, in anti-counterfeiting applications, the image observable to the naked eye must be striking, the complete 3D information cannot be obtained by the naked eye, and optical scanning and copying are not possible.

[0005] The scanning and copying optical system of a scanner or printer primarily exposes the original through various optical elements, forming a light image. This light image is then transferred to the surface of a uniformly charged photosensitive drum, where it forms an electrostatic latent image corresponding to the lightness and darkness of the original image. Existing scanners and printers have high optical resolution, making it somewhat easy to reproduce and print flat anti-counterfeiting images printed with traditional inks.

[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 produced using optical anti-counterfeiting feature technology have a dynamic changing effect. The current mainstream optical anti-counterfeiting is based on the surface three-dimensional 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 be moving, 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 Suzhou Weige Technology Group's patent CN107481612A, etc., are almost mainly based on the design of micro-nano structures to achieve light refraction and manipulation to form different colors or display effects.

[0008] The optical security effect of this anti-counterfeiting technology is somewhat photocopiable. For example, when viewed from above, the displayed optical color or pattern can still be scanned and printed to create a similar gradient effect. For dynamic 3D patterns, the full pattern can still be reverse-engineered and replicated based on the scanned and printed image from above. Therefore, existing methods cannot reliably prevent photocopying and scanning from above, failing to guarantee the highest level of security. Furthermore, 3D surface textures can still be photocopied and scanned using high-precision scanners or copying technologies. For example, advanced optical scanning systems can achieve micron-level pattern scanning. These systems utilize triangulation, which measures the data projected onto and reflected from the surface (not the object itself). A laser beam or LED beam is projected onto the workpiece surface, where it is received by a receiving camera (a position-resolving photodiode or CCD line) located next to the projection lens. When the distance between the workpiece and the projection lens changes, the angle of light reflection also changes, causing the position of the received image to change. Using trigonometric principles, the distance between the workpiece and the projection lens can be accurately calculated. The image receiver, composed of optical sensors, determines the position of the reflected light spot on the image. Based on this image position, the distance between the projection lens and the workpiece is calculated.

[0009] Summary of the Invention

[0010] Based on this, it is necessary to provide an optical imaging film with anti-copying characteristics, a preparation method thereof, and an anti-counterfeiting product for the problem of how to achieve the anti-copying function.

[0011] An optical imaging film with anti-copying characteristics, the optical imaging film comprising:

[0012] A transparent spacer layer having two opposite surfaces;

[0013] 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

[0014] 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;

[0015] Wherein, the front view pattern of the micro-graphic unit is obtained based on a stereoscopic real image and a virtual image, so that only a part of the stereoscopic real image is presented within a specific viewing angle range, and the part of the stereoscopic real image blocked by the virtual image is not displayed.

[0016] For the anti-copying optical imaging film applying the technical solution of the present invention, since only a part of the stereoscopic real image is presented within a specific viewing angle range and the part of the stereoscopic real image blocked by the virtual image is not displayed, the copied image cannot carry all the information of the optical imaging film, thereby achieving the functions of anti-copying and preventing reverse modeling.

[0017] 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 stereoscopic real image corresponding to the micro-focusing unit is tangent to the light field image unit of the virtual image.

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

[0019] 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 at a preset same position from M*N parallax images Q ijPixels are sampled and extracted from the preset same position and are sequentially placed into the light field image unit of the virtual image.

[0020] In a feasible implementation, obtaining 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.

[0021] In a feasible implementation, the virtual image has a hollow portion, and the hollow portion does not block the three-dimensional real image.

[0022] In a feasible implementation, the micro-graphic unit has a concave-convex structure along a cross section perpendicular to the surface of the transparent spacer layer;

[0023] The micro-focusing unit is a micro-lens, a micro-mirror or a hole array structure.

[0024] 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.

[0025] A method for preparing any of the above-mentioned optical imaging films having anti-copying properties comprises the following steps:

[0026] A micro-focusing unit array layer and a micro-image layer are formed on two surfaces of the transparent spacer layer, respectively. 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. The plurality of micro-image units are arranged correspondingly to the plurality of micro-focusing units, thereby obtaining an optical imaging film.

[0027] 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.

[0028] The preparation methods of the optical imaging films with anti-copying properties of the above-mentioned technical solutions of the present invention are simple and feasible. In the prepared optical imaging films, 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 reversely model.

[0029] In a feasible implementation, the front view pattern of the micro-graphic unit is a pattern obtained by tangency of the light field image unit of the three-dimensional physical image corresponding to the micro-focusing unit and the light field image unit of the virtual image.

[0030] In a feasible implementation, a mold for preparing the micro-graphic layer is used to form the micro-graphic layer, and the preparation method of the mold for preparing the micro-graphic layer includes the following steps:

[0031] 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.

[0032] 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; 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;

[0033] 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;

[0034] 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 ,…P MN} in sequence and putting 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 00 ,Q 01 ,…Q MN} in sequence and putting them into the light field image unit of the virtual image; making the light field image unit of the three-dimensional physical image tangent to the light field image unit of the virtual image;

[0035] S5: Repeat step S4 to complete the acquisition of the front view patterns of all micro-graphic units;

[0036] S6: After performing photolithography, development, and metal growth on the substrate in sequence, a mold for preparing the micro-graphic layer is obtained.

[0037] In a feasible implementation, the acquisition of the front view graph 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, and the light ray refracts after passing through the micro-focusing unit. If the light ray passes through the virtual image and intersects with the three-dimensional physical image, the color value of the farthest point where it intersects with the three-dimensional physical image is returned; if the light ray does not intersect with the three-dimensional physical 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 where it intersects with the three-dimensional physical image is returned.

[0038] In a feasible implementation, a mold for preparing the 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:

[0039] S1: Design a three-dimensional physical image and a virtual image, and the virtual image blocks part of the three-dimensional physical image within a specific viewing angle range;

[0040] 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; thereby calculate the number of pixels M * N of the micro-graphic unit;

[0041] S3: The pixel points of the micro-graphic unit and the center of the corresponding micro-focusing unit form a light ray, and the light ray refracts after passing through the micro-focusing unit. If the light ray passes through the virtual image and intersects with the three-dimensional physical image, the color value of the farthest point where it intersects with the three-dimensional physical image is returned; if the light ray does not intersect with the three-dimensional physical 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 where it intersects with the three-dimensional physical image is returned; traverse all pixel points in the micro-graphic unit to obtain the front view graph of the micro-graphic unit;

[0042] S4: Repeat step S3 to complete the acquisition of the front view graphs of all micro-graphic units;

[0043] S5: After performing photolithography, development and metal growth on the substrate in sequence, a mold for preparing the micro-graphic layer is obtained.

[0044] In a feasible implementation, the following steps are further included: a reflective layer is formed on the side of the micro-focusing unit array layer away from the micro-graphic layer.

[0045] An anti-counterfeiting product includes the optical imaging film with anti-copying characteristics as described in any one of the above.

[0046] 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.

[0047] To address the issue of photocopy resistance, the present invention, based on the principle of stereoscopic image display using a four-dimensional light field model, proposes a method for encoding spatial objects using computational graphics reverse ray tracing technology. This method involves setting multiple digital three-dimensional objects with different reflective and transmissive properties in a digital space. The first type is a three-dimensional object distribution with natural reflective properties (three-dimensional text, images, and complex morphological distributions), namely, a three-dimensional real image. The second type is a completely non-reflective and non-transmissive virtual object, which can be a planar or three-dimensional distribution, namely, a virtual image. When performing light field computational imaging based on a microfocus array, the information of both the virtual object and the three-dimensional real image is imaged on a plane near the focal plane (outside and inside) of the microfocus unit array layer, forming a complex microstructure computational distribution. The relative positional relationship between the two is matched based on the ray tracing design. Therefore, the blocked portion of the three-dimensional real image is selectively blocked by the virtual image from the front view and / or the top view. As a result, the optical imaging film prepared by this method has the functions of photocopy resistance and inability to reverse modeling. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] FIG1 is a schematic diagram of a conventional integrated imaging stereoscopic display;

[0049] FIG2 is a schematic diagram of an optical imaging film according to one embodiment of the present invention;

[0050] FIG3 is a front view of a three-dimensional image presented by an optical imaging film according to one embodiment of the present invention;

[0051] FIG4 is a tilted perspective view of a three-dimensional image presented by an optical imaging film according to one embodiment of the present invention;

[0052] FIG5 is a diagram showing a three-dimensional image presented by an optical imaging film according to an embodiment of the present invention when viewed from different viewing angles;

[0053] FIG6 is a diagram showing a three-dimensional image presented by an optical imaging film according to another embodiment of the present invention when viewed from different viewing angles;

[0054] FIG7 is a schematic diagram of a three-dimensional image presented by an optical imaging film according to another embodiment of the present invention;

[0055] FIG8 is a schematic diagram of a three-dimensional image presented by an optical imaging film according to another embodiment of the present invention;

[0056] 9( a ) to 9 ( d ) are views of a three-dimensional image presented by an optical imaging film according to an embodiment of the present invention observed from different viewing angles;

[0057] 10( a ) to 10 ( c ) are views of a three-dimensional image presented by an optical imaging film according to an embodiment of the present invention observed from different viewing angles;

[0058] 11( a ) to 11 ( c ) are views of a three-dimensional image presented by an optical imaging film according to an embodiment of the present invention observed from different viewing angles;

[0059] FIG12 is a schematic diagram illustrating the intersection of light rays with a three-dimensional physical image and a virtual image during acquisition of a front view image of a micro-graphic unit in an optical imaging film with anti-copying properties according to an embodiment of the present invention;

[0060] FIG13 is a schematic diagram illustrating the intersection of light rays with a three-dimensional physical image and a virtual image during acquisition of 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;

[0061] FIG14 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;

[0062] FIG15 is a flow chart of a method for preparing a mold for preparing a micro-graphic layer according to another embodiment of the present invention;

[0063] FIG16 is a front view of a micro-graphic unit during acquisition of a front view image according to an embodiment of the present invention;

[0064] FIG17 is a schematic diagram of a specific angle during acquisition of a front view image of a micro-graphic unit according to one embodiment of the present invention;

[0065] FIG18 is a schematic diagram showing a process of obtaining a front view of a micro-graphic unit according to an embodiment of the present invention, taking a front view angle as an example. DETAILED DESCRIPTION

[0066] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0067] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly attached to the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0069] The optical imaging film with anti-copying properties of the present invention can have a refractive or reflective structure. The refractive structure has the microfocusing element array layer facing upward, and the micrographic layer below, with the image viewed from above, in the direction of the microfocusing element array layer. The reflective structure, based on the refractive structure, has the microfocusing element array layer and micrographic layer arranged in opposite directions, and a reflective film added to the surface of the microfocusing element array layer.

[0070] Referring to FIG. 2 , an optical imaging film 100 with anti-copying properties according to one embodiment includes a transparent spacer layer 110, a microfocusing unit array layer 120, and a micrographic layer 130. The transparent spacer layer 110 has two opposing surfaces and can be made of PET or UV adhesive. The microfocusing unit array layer 120 is located on one surface of the transparent spacer layer 110. Specifically, in this embodiment, the microfocusing unit array layer 120 is located on the upper surface of the transparent spacer layer 110. Furthermore, the microfocusing unit array layer 120 includes a plurality of microfocusing units 121 arranged in an array. The micrographic layer 130 is located on the other surface of the transparent spacer layer 110. Specifically, in this embodiment, the microfocusing unit array layer 130 is located on the lower surface of the transparent spacer layer 110. Furthermore, the micrographic layer 130 includes a plurality of micrographic units 131 arranged in an array. The plurality of micrographic units 131 are arranged correspondingly to the plurality of microfocusing units 121.

[0071] In the aforementioned embodiment of the optical imaging film 100 with anti-copying properties, the front view of the micro-graphic unit 131 is derived from a 3D physical image 132 and a virtual image 133. As shown in Figures 3 and 4, only a portion of the 3D physical image 132 is displayed within a specific viewing angle range, while the portion of the 3D physical image 132 obscured by the virtual image 133 is not displayed. The specific viewing angle range refers to the range of viewing angles of the observer. The present invention does not impose any restrictions on the specific angle within the specific viewing angle range and can be set according to actual needs. The anti-copying optical imaging film of this embodiment, because only a portion of the 3D physical image is displayed within the specific viewing angle range, while the portion of the 3D physical image obscured by the virtual image is not displayed, prevents the copied image from carrying all the information of the optical imaging film, thereby achieving anti-copying and anti-reverse modeling capabilities.

[0072] Please refer to FIGS. 3 and 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-focus unit and the light field image unit of the virtual image 133. Only a part of the three-dimensional physical image 132 is displayed within a 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 the frustum structure absorbs all light and does not reflect any light. Since only a part of the three-dimensional physical image 132 is presented within a 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, thereby realizing the functions of anti-copying and unable to reverse-engineer and model. It should be noted that the virtual image is shown in the illustration of the present invention for the convenience of understanding, but in actual observation, the virtual image is invisible.

[0073] Please refer to FIG. 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 visible to the naked eye, having a shocking effect, being unable to obtain complete three-dimensional information with the naked eye, and being unable to be optically scanned and copied.

[0074] On the basis of the foregoing embodiment, the obtaining 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 putting them into the light field image unit of the three-dimensional physical image.

[0075] At the same time, the obtaining 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 , 0≤i<M, 0≤j<N; sampling and extracting pixels at a preset same position from the M*N disparity images Q ij and sequentially putting them into the light field image unit of the virtual image.

[0076] Based on the aforementioned embodiments, a real-object image for interference can be superimposed on the virtual image. As shown in FIG6 , in one embodiment, the real-object image for interference is a five-pointed star symbol. This prevents the three-dimensional real-object image "100 RMB" from being viewed and scanned from directly above, thereby achieving a more obvious anti-copying effect. Of course, the real-object image for interference can also be an image of other shapes.

[0077] It should be noted that in the optical imaging film with anti-copying properties of the present invention, the three-dimensional real image and the virtual image can be any pattern, and the positional relationship between the three-dimensional real 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 real image or within the three-dimensional real image.

[0078] Referring to FIG. 7 , in an optical imaging film with anti-copying properties according to another embodiment of the present invention, a three-dimensional physical image 132 “RMB100” is distributed around a mushroom-shaped virtual image 133. Since the surface of the virtual image 133 does not reflect light, the full information of the anti-copying image “RMB100” cannot be obtained during copying.

[0079] In the optical imaging film of the above embodiment, the surface of the three-dimensional real image is fully diffusely reflective, and the surface of the virtual image is non-reflective but has a shielding property.

[0080] Referring to Figure 8 , another embodiment of the present invention shows an optical imaging film with anti-copying properties. Two 3D physical images 132 are depicted, one representing the letter "R" and the other representing the letter "Y." A virtual image 133 is positioned between the two 3D physical images 132, obscuring both letters "R" and "Y." As the viewing angle changes, the letter "R" is sometimes visible and the letter "Y" is sometimes visible. The surface of the 3D physical images 132 is diffusely reflective, while all sides of the virtual image 133 are opaque. The top surface of the virtual image 133 is transmissive, but the letters "R" and "Y" are obscured.

[0081] In the optical imaging film with anti-copying properties of this embodiment, the virtual image 133 is specifically a virtual wall cloth. It should be noted that in order to achieve the purpose of blocking the anti-copying image, the shape of the virtual image 133 is not limited to a wall or column, and its shape can be designed arbitrarily.

[0082] Figures 9(a) to 9(d), Figures 10(a) to 10(c), and Figures 11(a) to 11(c) are observation views 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.

[0083] As shown in Figure 9(a), the inner sphere and the outer cube frame are virtual images, while the characters "S," "V," and "G" are three-dimensional physical images. Figure 9(b) shows a top view, where only the character "S" is visible. Figure 9(c) shows a left-side view, where only the character "G" is visible. Figure 9(d) shows a right-side view, where the image is empty. Virtual images are shown in the diagrams for ease of understanding; in actual observation, they are invisible.

[0084] As shown in Figure 10(a), the five-pointed star and the circle of numbers around its edge are physical three-dimensional images, while the cylinder and hollow frustum are virtual images. Figure 10(b) shows a top view, where only the five-pointed star is visible. Figure 10(c) shows a side view, where a portion of the numbers are visible from a certain viewing angle. Virtual images are shown in the diagrams for ease of understanding; in actual observation, they are invisible.

[0085] As shown in Figure 11(a), the outer circle of characters and the five-pointed star are the three-dimensional physical images, while the hollow cylinder, narrow at the top and wide at the bottom, is the virtual image. Figure 11(b) shows a top view, where the deformed characters are visible. Figure 11(c) shows a side view, where a portion of the deformed characters is visible from a certain angle. The virtual images are shown in the diagrams for ease of understanding; in actual observation, they are invisible.

[0086] In addition, it should 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.

[0087] Please refer to Figures 1, 12 and 13. In another embodiment of the optical imaging film with anti-copying properties of the present invention, obtaining the front view image of the micro-graphic unit includes: the pixel point of the micro-graphic 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 physical image 132, the color value of the farthest point intersecting with the three-dimensional physical image 132 is returned; if the light ray does not intersect with the three-dimensional physical 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 physical image is returned.

[0088] Specifically in this embodiment, the arrows in Figures 12 and 13 represent light rays. In Figure 12 , the 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 ray does not pass through the virtual image 133, the color value of the farthest point A where it intersects with the 3D real image 132 is obtained. In Figure 13 , the virtual image 133 is located between the micro-focusing unit array layer 120 and the 3D real image 132, 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, and the color value of the intersection point B is obtained.

[0089] Based on several of the aforementioned embodiments, virtual image 133 includes a hollow portion that does not obstruct 3D physical image 132. When viewed within a specific viewing angle, an observer can see the 3D physical image beneath the virtual image through the hollow portion, making it more difficult to copy the image and further enhancing the anti-copying function. It should be noted that the virtual image does not need to have a hollow portion.

[0090] Based on the aforementioned embodiments, the micro-graphic unit 131 has a concave-convex structure along a 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. The micro-lens can be a conventional curved lens, a cylindrical lens, a Fresnel lens, a super lens, a polarization-sensitive lens, a liquid crystal lens, or a grating lens, among other forms of micro-lenses.

[0091] Based on the aforementioned embodiments, a reflective layer (not shown) is provided on the side of the micro-focusing unit array layer 120 away from the micro-image layer 130. In this case, the structure of the optical imaging film is reflective.

[0092] The optical imaging film of the present invention has the following advantages: 1. Anti-copying. By fusing multiple virtual and real images, complete information cannot be obtained at any specific angle. 2. Anti-copying. Digital modeling cannot render the required light field image, making it impossible to replicate printed images. 3. Simple structure, allowing for mass production. 4. The fusion of multiple 3D models, linked to the viewing angle, allows the image to dynamically change with the viewing angle, creating a fantastical and striking effect.

[0093] A method for preparing the optical imaging film having anti-copying properties according to one embodiment of the present invention comprises the following steps:

[0094] 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, and the micro-image layer includes a plurality of micro-image units arranged in an array. The plurality of micro-image units and the plurality of micro-focusing units are arranged correspondingly to obtain an optical imaging film. 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 a portion of the three-dimensional real image is presented within a specific viewing angle range, and the portion of the three-dimensional real image blocked by the virtual image is not displayed.

[0095] In one embodiment, the operation of forming the micro-focusing unit array layer and the micro-image layer on the two surfaces of the transparent spacer layer is as follows:

[0096] S1: Provide substrate;

[0097] S2: UV glue is applied 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;

[0098] S3: Coat UV glue on the other side of the substrate, use the micro-graphic layer mold to imprint a micro-nano pit structure, then fill the pit structure with ink, and scrape it flat to obtain the micro-graphic layer; thus obtaining the optical imaging film, where the substrate serves as the transparent spacer layer.

[0099] Among them, the operations of forming the micro-focusing unit array layer and the micro-graphic layer on the two surfaces of the transparent spacer layer in another embodiment are as follows:

[0100] S1: Provide a substrate;

[0101] S2: Coat UV glue on one side of the substrate, use the micro-graphic layer mold to imprint a micro-nano pit structure, then fill the pit structure with ink, and scrape it flat to obtain the micro-graphic layer;

[0102] S3: Coat PET or UV glue on the micro-graphic layer, and obtain the micro-focusing unit array layer after imprinting with the micro-focusing unit array layer mold; thus obtaining the optical imaging film, where the part between the micro-graphic layer and the micro-focusing unit array layer serves as the transparent spacer layer.

[0103] In the preparation method of the above optical imaging film with anti-copying characteristics in the first 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 of the three-dimensional real object image corresponding to the micro-focusing unit and the light field image unit of the virtual image.

[0104] 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. 14. The preparation method of the mold for preparing the micro-graphic layer includes the following steps:

[0105] S1: Design a three-dimensional real object image and a virtual image, and the virtual image blocks part of the three-dimensional real object image within a specific viewing angle range.

[0106] 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, generate M*N viewpoints, and determine the position of the virtual camera.

[0107] S3: Collect the three-dimensional real object image at each viewpoint to obtain M*N three-dimensional real object 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.

[0108] S4: Micro-focusing unit L 00Obtaining the front view graph of the corresponding micro-graphic unit includes: extracting pixels sampled at a preset same position from the stereo physical image parallax images {P 00 , P 01 , … P MN}, and sequentially placing them into the light field image units of the stereo physical image in order; extracting pixels sampled at a preset same position from the virtual image parallax images {Q 00 , Q 01 , … Q MN}, and sequentially placing them into the light field image units of the virtual image in order; the light field image units of the stereo physical image are tangent to the light field image units of the virtual image.

[0109] S5: Repeat step S4 to complete the acquisition of the front view graphs of all micro-graphic units.

[0110] S6: After performing photolithography, development, and metal growth on the substrate in sequence, a mold for preparing the micro-graphic layer is obtained.

[0111] In the preparation method of the above optical imaging film with anti-copying characteristics in the second embodiment of the present invention, the acquisition of the front view graph of the micro-graphic unit includes: a light ray is formed between the pixel points 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 stereo physical image, the color value of the farthest intersection point with the stereo physical image is returned; if the light ray does not intersect with the stereo physical 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 intersection point with the stereo physical image is returned.

[0112] On the basis of the foregoing embodiment, a micro-graphic layer is formed using the mold for preparing the micro-graphic layer. Referring to FIG. 15, the preparation method of the mold for preparing the micro-graphic layer includes the following steps:

[0113] S1: Design a stereo physical image and a virtual image, and the virtual image blocks part of the stereo physical image within a specific viewing angle range.

[0114] S2: Set the parameters of the micro-focusing unit array layer. The parameters include the number L ij of micro-focusing units, where 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.

[0115] S3: The pixel points of the micro-graphic unit and the center of the corresponding 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 physical image, the color value of the farthest point intersecting with the three-dimensional physical image is returned; if the light ray does not intersect with the three-dimensional physical 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 physical image is returned; all pixel points in the micro-graphic unit are traversed to obtain the front view graphics of the micro-graphic unit.

[0116] S4: Repeat step S3 to complete the acquisition of front view graphics of all micro-graphic units.

[0117] S5: After performing photolithography, development and metal growth on the substrate in sequence, a mold for preparing the micro-image layer is obtained.

[0118] Based on the above two embodiments, the method for preparing the optical imaging film further includes the following step: forming a reflective layer on the side of the micro-focusing unit array layer away from the micro-image layer, thereby obtaining a reflective optical imaging film.

[0119] 16 to 18 , a method for obtaining a front view of a micro-graphic unit according to an embodiment of the present invention includes the following steps:

[0120] For any viewing angle, image recording is performed. As shown in FIG16 , this is a right-to-left viewing angle. The path along this viewing angle is as shown in FIG16 . As shown in FIG16 , the first stereoscopic real image is 1 , the virtual image is 2 , and the second stereoscopic real image is 3 .

[0121] Take the information of the figure "Y" in 1 as 1-1, and the remaining information is 1-2, as shown in Figure 18;

[0122] The information of 1-2 and 2 is ANDed to obtain 2-1 and the remaining information 2-2, as shown in FIG18 ;

[0123] The information of 2-2 and 3 is ANDed together to obtain 3-1 and the remaining information 3-3, as shown in FIG18 ;

[0124] Obtain the recording surface 140 information 1-1 and 3-1 corresponding to the 3D physical image, and the recording surface 140 information 2-1 corresponding to the virtual image, assign a null value to the virtual image recording surface 140 information, and merge the images 1-1, 2-1, and 3-1;

[0125] Similarly, if there are multiple-faced physical images and multiple-faced virtual images, information extraction starts from the face with the largest depth of field to the face with the smallest depth of field.

[0126] In the above steps, an image is recorded for any viewing angle. For example, FIG17 shows a side viewing angle from the upper right to the lower left. Information can be recorded using the above method.

[0127] In the above steps, information of all viewing angles of the image is recorded according to the field of view of the micro-focusing units in the micro-focusing unit array layer 120 and combined into complete recorded information.

[0128] 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.

[0129] To address the issue of photocopy resistance, the present invention, based on the principle of stereoscopic image display using a four-dimensional light field model, proposes a method for encoding spatial objects using computational graphics reverse ray tracing technology. This method involves setting multiple digital three-dimensional objects with different reflective and transmissive properties in a digital space. The first type is a three-dimensional object distribution with natural reflective properties (three-dimensional text, images, and complex morphological distributions), namely, a three-dimensional real image. The second type is a completely non-reflective and non-transmissive virtual object, which can be a planar or three-dimensional distribution, namely, a virtual image. When performing light field computational imaging based on a microfocus array, the information of both the virtual object and the three-dimensional real image is imaged on a plane near the focal plane (outside and inside) of the microfocus unit array layer, forming a complex microstructure computational distribution. The relative positional relationship between the two is matched based on the ray tracing design. Therefore, the blocked portion of the three-dimensional real image is selectively blocked by the virtual image from the front view and / or the top view. As a result, the optical imaging film prepared by this method has the functions of photocopy resistance and inability to reverse modeling.

[0130] An anti-counterfeiting product according to one embodiment includes any one of the above-mentioned optical imaging films with anti-copying properties.

[0131] Among them, anti-counterfeiting products can be, for example, certificates, tickets, tobacco and alcohol packaging, or daily chemical packaging.

[0132] 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.

[0133] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0134] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. An optical imaging film with anti-copying properties, 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, 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, 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 at a preset same position from the M*N parallax images Q ij and sequentially putting them into the light field image unit of the virtual image according to the order.

4. The optical imaging film according to claim 1, 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, 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, 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, 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 with anti-copying properties according to any one of claims 1 to 7, 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, 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, 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 viewpoint 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 viewpoint 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, 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, 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, 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, characterized in that: An optical imaging film with anti-copying properties comprising any one of claims 1 to 7.

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