Transmission-type multi-wavelength image reproduction optical element, printing stock and preparation method

Abstract

The invention provides a transmission-type multi-wavelength image reproduction optical element, a printing stock and a preparation method, and the preparation method of the transmission-type multi-wavelength image reproduction optical element utilizes a wavelength multiplexing technology to hide a plurality of patterns in the same hologram, and realizes selective reproduction of the patterns by changing the wavelength of illumination light. For each pattern to be hidden, a hologram for a specific wavelength is calculated, respectively. And then the holograms for different wavelengths are superposed and coded on the same physical diffraction structure. When a wide-spectrum light source (such as white light) is used for irradiation, all coding information is diffracted at the same time, and reproductive images are overlapped, blurred and unclear and cannot be recognized due to dispersion and crosstalk. When a monochromatic point light source (specific wavelength) is used for irradiating from the back surface of the element, only a target image corresponding to the wavelength can be clearly reproduced with high contrast, and images corresponding to other wavelengths cannot be focused due to serious phase mismatch, so that the anti-counterfeiting effect is good.

Description

Technical Field

[0001] This invention relates to the field of anti-counterfeiting technology, and in particular to a transmissive multi-wavelength image reproduction optical element, a substrate, and a preparation method. Background Technology

[0002] Traditional anti-counterfeiting technologies mainly include: laser anti-counterfeiting, fluorescent anti-counterfeiting, magnetic anti-counterfeiting, temperature-sensitive anti-counterfeiting, digital anti-counterfeiting, and texture anti-counterfeiting. Laser anti-counterfeiting is the most widely used first-generation anti-counterfeiting technology. It utilizes laser color holographic plate-making technology and embossing replication technology to achieve anti-counterfeiting. It protects the authenticity of the product through laser holographic iridescent display, and is generally observed primarily by the naked eye, often showing effects such as horizontal stripes, light pillars, and plain surfaces. Current mainstream anti-counterfeiting technologies such as holographic hot stamping, microtext, and OVI optically variable ink have gradually become widespread and are being counterfeited. Computational holography technology is used for high-end anti-counterfeiting due to its complex production and large information capacity, but traditional computational holographic (CGH) labels usually only have a static pattern, making them easy to photograph and counterfeit. The information capacity and interactivity of a single CGH pattern are no longer sufficient.

[0003] Traditional anti-counterfeiting technologies initially played a role, but their effectiveness was limited due to their susceptibility to counterfeiting. The reasons for this are that these anti-counterfeiting technologies generally suffer from the following shortcomings: The technology is low-tech and the structural combination is easily deciphered. Conventional anti-counterfeiting materials rely on certain special technical formulas or equipment advantages, but with the development of science and technology, these advantages will no longer exist.

[0004] Anti-counterfeiting verification methods are cumbersome, difficult to verify quickly and intuitively, and result in a poor user experience. For example, texture-based anti-counterfeiting requires consumers to compare the position and color of randomly scattered fibers on each label, giving counterfeiters an opportunity to exploit the system.

[0005] The anti-counterfeiting measures are too simplistic, making it easy to create a single point of vulnerability, and lacking multi-level anti-counterfeiting verification.

[0006] Therefore, existing technologies need to be improved and enhanced. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention provides a transmissive multi-wavelength image reproduction optical element, a substrate, and a preparation method, which can overcome the limitations of static and visual reproduction of traditional anti-counterfeiting technology. When irradiated with a monochromatic point light source (specific wavelength), only the anti-counterfeiting pattern designed for that wavelength will be clearly reproduced, while other patterns cannot form a clear image due to severe aberrations, thereby achieving selective reproduction and good anti-counterfeiting effect.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The fabrication method of a transmission-type multi-wavelength image reconstruction optical element includes: Obtain binary images containing the text and images to be hidden, drawn by multiple drawing software programs; The binary image and the corresponding reconstruction wavelength of the binary image are input into the computational diffraction optical imaging software. The computational diffraction optical imaging software uses the point source method to calculate the target complex amplitude field generated by the binary image on the hologram plane at the reconstruction wavelength, and obtains the complex amplitude distribution of the binary image. Multiple single complex amplitude distributions are superimposed, and multiple iterations are performed at multiple set wavelengths. When the iteration is completed, the diffraction field is output, and a multi-wavelength selected reconstruction holographic file is generated based on the diffraction field. The multi-wavelength selective reproduction computational holographic file is imported into a photolithography machine, which then engraves the glass according to the multi-wavelength selective reproduction computational holographic file to obtain a photolithographic glass plate. Multiple photolithographic glass plates are spliced ​​together on a panelizing machine to obtain the transmissive multi-wavelength image reproduction optical element.

[0009] Furthermore, the process of superimposing multiple single complex amplitude distributions and performing multiple iterations at multiple set wavelengths, outputting a diffraction field upon completion of the iterations, and generating a multi-wavelength selected reconstruction holographic file based on the diffraction field includes: The image to be hidden is considered to be composed of multiple discrete points, and the complex amplitude distribution of the target on the holographic plane is calculated point by point for each of the discrete points. Based on the principle of light wave superposition, the complex amplitude distributions of each discrete point on the recording surface are superimposed to obtain the multi-wavelength selected reconstruction computational holographic file.

[0010] Furthermore, the target complex amplitude field is:

[0011] Where exp represents the exponential function, i.e., exp()=e(), where e is the natural constant (approximately equal to 2.7); A is the amplitude of the reference light, and j is the imaginary unit; X and Y are spatial coordinate variables, representing the positions on the holographic two-dimensional plane, with X representing the horizontal coordinate and Y representing the vertical coordinate.

[0012] Furthermore, the diffraction field is:

[0013] Among them, U totalThe total complex amplitude of light waves at a point on the two-dimensional plane (X,Y) is the sum of the complex amplitudes generated by three different light wave components at that point; ∑ is the summation operator, indicating that the expression immediately following it is summed from i=1 to i=3; i is the index variable used to distinguish different light wave components, where i=1,2,3 represent the 1st, 2nd, and 3rd light waves, respectively; exp represents the exponential function, i.e., exp()=e(), where e is the natural constant, and e equals 2.7; A is the magnitude of the reference light amplitude, and j is the imaginary unit; X and Y are spatial coordinate variables, representing the positions on the holographic two-dimensional plane, where X represents the horizontal coordinate and Y represents the vertical coordinate; ϕi(X,Y) is the wavefront phase distribution of the i-th light wave component at different positions on the two-dimensional plane (X,Y).

[0014] Further, the step of importing the multi-wavelength selective reconstruction computational holographic file into a photolithography machine, and the photolithography machine engraving on the glass according to the multi-wavelength selective reconstruction computational holographic file to obtain a photolithographic glass plate, includes: The multi-wavelength selective reconstruction computational holographic file is imported into a lithography machine. The laser emitted by the lithography machine's laser beam is controlled by the lithography machine's optical system to form an exposure spot of 200-500nm. The objective lens of the lithography machine focuses the spot onto the photoresist surface for point-by-point exposure. The energy of the spot is absorbed by the photoresist at the exposed areas, triggering a decomposition reaction in the photoresist. The unexposed areas are preserved. After development, the decomposed photoresist is removed, and the lithographic glass plate with a three-dimensional microstructure of a preset morphology is obtained.

[0015] Furthermore, the step of using multiple photolithographic glass plates to stitch together on a panelizing machine to obtain the transmissive multi-wavelength image reconstruction optical element includes: Multiple small-area photolithography glass plates are spliced ​​together into a large-area resin plate on a panelizing machine; A polymer resin film is used to cover the photolithography glass plate. An ultraviolet curing material is extruded between the polymer resin film and the photolithography glass plate using a plate-laying machine with a rotary pressing method. The material is cured under pressure and ultraviolet light exposure, and the microstructure on the photolithography glass plate is transferred to the large-area resin film to obtain the transmissive multi-wavelength image reproduction optical element.

[0016] A transmissive multi-wavelength image reproduction optical element is manufactured using the method described above.

[0017] A method for fabricating a substrate for a transmissive multi-wavelength image reproduction optical element includes: Using metallic nickel as the anode and the aforementioned transmissive multi-wavelength image reproduction optical element as the cathode, the resin master plate is placed in an electrolytic cell, and a metallic nickel layer is formed on the resin master plate under electrolysis. The metallic nickel layer is then peeled off to obtain a metallic nickel plate. A UV-curable resin is coated onto a polymer film, and a microstructure is transferred onto the polymer film using a nickel plate. The film is then cured under UV light and wound up to obtain an anti-counterfeiting film.

[0018] A substrate for a transmissive multi-wavelength image reproduction optical element is manufactured using the above method.

[0019] Furthermore, the substrate includes a base film, and a holographic information layer is disposed on the front side of the base film.

[0020] Compared with the prior art, the method for preparing the substrate of the transmissive multi-wavelength image reproduction optical element provided by the present invention can achieve selective reproduction and good anti-counterfeiting effect when irradiated with a monochromatic point light source (specific wavelength). Only the anti-counterfeiting pattern designed for that wavelength will be clearly reproduced, while other patterns cannot form a clear image due to severe aberrations. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 A flowchart illustrating the fabrication process of the substrate for the transmissive multi-wavelength image reproduction optical element provided by this invention.

[0023] Figure 2 This is a schematic diagram of rotary nanoimprinting in the method for preparing the substrate of the transmissive multi-wavelength image reproduction optical element provided by the present invention.

[0024] Figure 3 This is a structural diagram of the substrate for the transmissive multi-wavelength image reproduction optical element provided by the present invention.

[0025] Figure 4 This is a schematic diagram showing the illumination of the substrate of the transmissive multi-wavelength image reproduction optical element provided by the present invention.

[0026] Figure descriptions: Photolithography glass plate-a, resin plate-b, nickel plate-c, anti-counterfeiting film-d, glass-1, photoresist-2, resin film-3, computational holographic information layer-4, nickel plate-5, base film-6. Detailed Implementation

[0027] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0029] In this invention, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this invention and its embodiments, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to require them to be constructed and operated in a specific orientation. Furthermore, some of the aforementioned terms may have other meanings besides indicating orientation or positional relationship; for example, the term "upper" may in some cases indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this invention according to the specific circumstances.

[0030] Furthermore, the terms “first” and “second” as used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are used only to distinguish one element from another. When used herein, the singular forms “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having” specify the presence of the stated features, integrals, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, integrals, steps, operations, components, parts, or combinations thereof.

[0031] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0032] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0033] like Figures 1-4 As shown, the method for fabricating a transmissive multi-wavelength image reconstruction optical element provided by the present invention includes: Obtain binary images containing text and images to be hidden, drawn by multiple drawing software programs, including the characters "JINJIA", "HOLOTEK" and the icon "❖"; The binary image and its corresponding reconstructed wavelength are input into the calculation diffraction optical imaging software. The character "JINJIA" sets the diffraction wavelength to λ1, the character "HOLOTEK" sets the diffraction wavelength to λ2, and the icon "❖" sets the diffraction wavelength to λ3. The calculation diffraction optical imaging software uses the point source method to calculate the target complex amplitude field generated by the binary image on the hologram plane at the reconstructed wavelength, and obtains the complex amplitude distribution of the binary image. Multiple single complex amplitude distributions are superimposed, and multiple iterations are performed at multiple set wavelengths. When the iterations are complete, the superimposed complex amplitude diffraction field U is output. total And generate a multi-wavelength selective reconstruction calculation holographic file based on the diffraction field; The multi-wavelength selective reproduction computational holographic file is imported into a photolithography machine, which performs laser direct writing engraving on the glass according to the multi-wavelength selective reproduction computational holographic file. After development and fixing, a photolithographic glass plate is obtained. Multiple photolithography glass plates are assembled on a panelizing machine to obtain the transmissive multi-wavelength image reproduction optical element.

[0034] Using metallic nickel as the anode, the above-described transmissive multi-wavelength image reproduction optical element... As the cathode, the resin master plate is placed in an electrolytic cell, and a metallic nickel layer is formed on the resin master plate under the action of electrolysis. The metallic nickel layer is then peeled off to obtain a metallic nickel plate. A UV-curable resin is coated onto a polymer film, and a nanostructure is embossed on the polymer film using a nickel plate. The embossed structure is then cured under UV light and wound up to obtain an anti-counterfeiting film.

[0035] In this embodiment, the fabrication process of the transmissive multi-wavelength image reconstruction optical element is a complex process that integrates computational optics and precision micromachining technology. First, a binary image containing the text and image information to be hidden needs to be designed and drawn in professional drawing software. The binary image, as an information carrier, has a clear black-and-white characteristic that facilitates subsequent diffraction calculations.

[0036] Next, the binary image and the preset corresponding reconstruction wavelength are input into the computational diffraction optical imaging software. The software uses the point source method to calculate and simulate the target complex amplitude field generated by the binary image on the preset hologram plane under coherent light illumination at a specific reconstruction wavelength, thereby accurately obtaining the complex amplitude distribution of the binary image under this condition. The complex amplitude distribution contains key information about the amplitude and phase of the light wave.

[0037] It should be noted that one wavelength corresponds to one binary image. Initially, two or more binary images are drawn in Photoshop, imported into diffraction optical imaging software, and different diffraction wavelengths are set for each. Then, the complex amplitude distribution of each binary image is calculated separately, and the single complex amplitude distributions obtained from multiple binary images are superimposed to generate the final computational hologram. That is, multiple single complex amplitude distributions are the different imported binary images.

[0038] Then, the core computational hologram generation stage begins. The complex amplitude distributions obtained at a single wavelength are superimposed, and multiple optimization calculations are performed at several different wavelengths using an iterative algorithm (such as the Gerchberg-Saxton algorithm or its variants). This process aims to balance diffraction efficiency and crosstalk at different wavelengths, ensuring that the final multi-wavelength selective reconstruction computational hologram file can clearly reproduce different target images under illumination at the corresponding wavelengths, while exhibiting no significant interference or other predetermined states at other wavelengths. Subsequently, the generated multi-wavelength selective reconstruction computational hologram file is imported into a high-precision lithography machine. Based on the data in the file, the lithography machine uses laser beams or other precision methods to perform micro-nano-scale engraving on a specially made glass substrate, permanently recording the microstructure of the computational hologram on the glass, creating a single lithographic glass plate.

[0039] Finally, based on the size and functional requirements of the final optical element, a panelizing machine is used to precisely splice and align multiple photolithographic glass plates engraved with different or complementary information, integrating them into a complete, large-area transmissive multi-wavelength image reproduction optical element. Under illumination with white light or a specific multi-wavelength light source, the transmissive multi-wavelength image reproduction optical element can exhibit a pre-designed, wavelength-dependent selective image reproduction effect, showing broad application prospects in fields such as anti-counterfeiting, information storage, and novel displays.

[0040] The microstructure of the transmissive multi-wavelength image reconstruction optical element does not correspond to a single image. Instead, it assigns multiple different target images (such as logos and text) to different specific wavelengths. After encoding by a computational holographic algorithm (point source algorithm combined with iterative optimization algorithm), the images are fused and superimposed into the same phase distribution function, and then photolithography is used to obtain a multi-wavelength selective reconstruction computational holographic microstructure.

[0041] Compared with existing technologies, the technical solution of this invention utilizes wavelength multiplexing technology to hide multiple patterns within the same hologram, and achieves selective pattern reproduction by changing the wavelength of the illumination light. For each pattern to be hidden, a hologram for a specific wavelength (e.g., λ1-670mm, λ2-532mm, λ3-473mm) is calculated. These holograms for different wavelengths are then superimposed and encoded onto the same physical diffraction structure. When illuminated by a broadband light source (e.g., white light), all encoded information diffracts simultaneously, resulting in overlapping, blurred, and unrecognizable reconstructed images due to dispersion and crosstalk. When illuminated from the back of the element by a monochromatic point light source (specific wavelength), only the target image corresponding to that wavelength can be clearly and with high contrast reproduced, while images corresponding to other wavelengths cannot be focused due to severe phase mismatch. This achieves "one-click switching" information selection and reading, resulting in excellent anti-counterfeiting performance.

[0042] Furthermore, the step of using drawing software to draw a binary image containing the text to be hidden includes: In the binary image, the grayscale value of the pixels containing the text to be hidden is 0. The grayscale value of all pixels in the binary image except for the text is 255. A grayscale value of 0 represents black, and a grayscale value of 255 represents white. Changing the grayscale value of the binary image is to display the text information in the text to be hidden, so as to facilitate subsequent text recognition.

[0043] Furthermore, the process of superimposing multiple single complex amplitude distributions and performing multiple iterations at multiple set wavelengths, outputting a diffraction field upon completion of the iterations, and generating a multi-wavelength selected reconstruction holographic file based on the diffraction field includes: The image to be hidden is considered to be composed of multiple discrete points, and the complex amplitude distribution of the target on the holographic plane is calculated point by point for each of the discrete points. Based on the principle of light wave superposition, the complex amplitude distributions of each discrete point on the recording surface are superimposed to obtain the multi-wavelength selected reconstruction computational holographic file.

[0044] The target complex amplitude field is:

[0045] Where exp represents the exponential function, i.e., exp()=e(), where e is the natural constant (approximately equal to 2.7); A is the amplitude of the reference light, and j is the imaginary unit; X and Y are spatial coordinate variables, representing the positions on the holographic two-dimensional plane, with X representing the horizontal coordinate and Y representing the vertical coordinate.

[0046] The diffraction field is:

[0047] Among them, U total The total complex amplitude of light waves at a point on the two-dimensional plane (X,Y) is the sum of the complex amplitudes generated by three different light wave components at that point; ∑ is the summation operator, indicating that the expression immediately following it is summed from i=1 to i=3; i is the index variable used to distinguish different light wave components, where i=1,2,3 represent the 1st, 2nd, and 3rd light waves, respectively; exp represents the exponential function, i.e., exp()=e(), where e is the natural constant, and e equals 2.7; A is the magnitude of the reference light amplitude, and j is the imaginary unit; X and Y are spatial coordinate variables, representing the positions on the holographic two-dimensional plane, where X represents the horizontal coordinate and Y represents the vertical coordinate; ϕi(X,Y) is the wavefront phase distribution of the i-th light wave component at different positions on the two-dimensional plane (X,Y).

[0048] In this embodiment, the core computational step in generating the multi-wavelength selected reconstruction computational holographic file essentially decomposes the complex wavefront reconstruction problem into a linear superposition of contributions from a large number of simple point sources. Specifically, this process first discretizes the graphic information to be hidden at the algorithm level, treating it as a set composed of countless independent, discrete point sources. For each preset reconstruction wavelength, the following fine calculation needs to be performed individually: based on scalar diffraction theory, the complex amplitude distribution generated when the spherical wave emitted by each discrete point source propagates to the holographic plane at the far field or a preset distance is calculated point by point. This calculation accurately considers the propagation phase differences caused by different wavelengths, thereby generating a target complex amplitude field describing its specific wavefront for each wavelength.

[0049] It should be noted that, for each point, the contribution of the complex amplitude generated by the emitted spherical wave propagating to the hologram plane at a specific reconstruction wavelength is precisely calculated based on scalar diffraction theory (such as Fresnel or Fraunhofer diffraction formulas). The key to this calculation is to accurately include the phase delay determined by the propagation distance and different wavelengths, thereby generating the corresponding target complex amplitude distribution for each point source.

[0050] Based on the principle of linear superposition of light waves, the complex amplitude distributions generated by all discrete point light sources at the same wavelength on the holographic recording surface are coherently superimposed. This superposition is an addition in a complex sense, that is, it integrates both amplitude and phase information, and finally synthesizes a complete complex amplitude distribution corresponding to the entire target image at that single wavelength.

[0051] The most crucial step lies in multi-wavelength collaborative design. After calculating the initial complex amplitude distribution for each of the set wavelengths, the complex amplitude fields corresponding to these different wavelengths are comprehensively superimposed and optimized in the function space of the computational hologram. This process typically requires multiple iterations using iterative algorithms. By repeatedly adjusting the phase or amplitude distribution of the hologram plane, the final generated single computational hologram file can simultaneously encode information from multiple wavelengths. The optimization goal is to efficiently and clearly reproduce the predetermined image when illuminated by light of the corresponding wavelengths, while minimizing crosstalk between wavelengths, thereby achieving wavelength-selective image reproduction and ultimately generating the multi-wavelength selective reproduction computational hologram file suitable for photolithography.

[0052] Further, the step of importing the multi-wavelength selective reconstruction computational holographic file into a photolithography machine, and the photolithography machine engraving on the glass according to the multi-wavelength selective reconstruction computational holographic file to obtain a photolithographic glass plate, includes: The multi-wavelength selective reproduction computational holographic file is imported into a lithography machine. The laser emitted by the lithography machine's laser beam is controlled by the lithography machine's optical system to form an exposure spot of 200-500nm. The objective lens of the lithography machine focuses the light spot onto the photoresist on the glass surface for point-by-point exposure. The energy of the light spot is absorbed by the photoresist in the exposed areas, triggering a decomposition reaction in the photoresist. The unexposed areas are preserved. After development, the decomposed photoresist is removed, and the lithographic glass plate with the preset three-dimensional microstructure is obtained.

[0053] In this embodiment, the design pattern is imported into a photolithography machine. A laser emits a laser beam, which is controlled by an optical system to form a 400nm exposure spot. The objective lens focuses the spot onto the photoresist surface for point-by-point exposure. The energy of the spot is absorbed by the photoresist at the exposed areas, triggering a decomposition reaction. The unexposed areas are preserved. The decomposed photoresist is then removed by development, resulting in a photolithographic glass plate with a predetermined three-dimensional microstructure. Transmission imaging achieves phase modulation through a single optical path difference, and the depth of the microstructure must reach the phase modulation depth (…). >2π), otherwise it will reduce diffraction efficiency and affect the clarity of image and text reproduction. The following condition must be met:

[0054] but Where λ is the incident light wavelength and n is the refractive index of the medium, such as the photoresist-air interface, the groove depth of the microstructure is about 2λ, which can cover the 2π phase.

[0055] Furthermore, the step of using multiple photolithographic glass plates to stitch together on a panelizing machine to obtain the transmissive multi-wavelength image reconstruction optical element includes: Multiple small-area photolithography glass plates are spliced ​​together into a large-area resin plate on a panelizing machine; A polymer resin film is used to cover the photolithography glass plate. An ultraviolet curing material is extruded between the polymer resin film and the photolithography glass plate using a plate-laying machine with a rotary pressing method. The material is cured under pressure and ultraviolet light exposure, and the microstructure on the photolithography glass plate is transferred to the large-area resin film to obtain the transmissive multi-wavelength image reproduction optical element.

[0056] In this embodiment, several photolithographic glass plates, fabricated using photolithography, are joined together on a panelizing machine to form a large-area resin plate. The panelizing machine uses a rotary die-flattening method to extrude a UV-curable material between the polymer resin film and the photolithographic glass plates. Under pressure and UV light exposure, cross-linking and curing are initiated, transferring the micro-nano structures on the photolithographic glass plates onto the large-area resin film, thereby fabricating the transmissive multi-wavelength image reproduction optical element.

[0057] The transmissive multi-wavelength image reproduction optical element provided by this invention is manufactured using the method described above.

[0058] The present invention provides a method for fabricating a substrate for a transmissive multi-wavelength image reconstruction optical element based on computational diffraction light, comprising: Using metallic nickel as the anode and the aforementioned transmissive multi-wavelength image reproduction optical element as the cathode, the resin master plate is placed in an electrolytic cell, and a metallic nickel layer is formed on the resin master plate under electrolysis. The metallic nickel layer is then peeled off to obtain a metallic nickel plate. UV-cured resin is coated onto a polymer film (pre-coated PET base film, the pre-coating layer is a functional thin layer applied to the surface of the PET base film by a coating process before the PET film leaves the factory, the pre-coating layer is an acrylic composite material that provides excellent adhesion for the subsequent nanoimprinting process) and the microstructure is copied and transferred onto the polymer film using the metal nickel plate. After UV curing, the anti-counterfeiting film is obtained by winding.

[0059] In this embodiment, the transmissive multi-wavelength image reconstruction optical element is used as the cathode, and metallic nickel is used as the anode. Under electrolysis, a layer of metallic nickel is gradually deposited on the transmissive multi-wavelength image reconstruction optical element, which is then peeled off to obtain a metallic nickel plate. The transmissive multi-wavelength image reconstruction optical element needs to be conductive to facilitate electrolytic deposition, and a silver mirror reaction is used to achieve chemical silver plating. After chemical silver plating, the non-metallic transmissive multi-wavelength image reconstruction optical element is immersed in an electrolyte. By controlling the current density (3-6 A / dm²), electrolyte temperature (55-60°C), and pH value (3-4), nickel ions are directionally deposited on the surface of the resin master, forming a nickel layer with a thickness of 0.05-0.3 mm. The nickel layer is then mechanically separated from the resin master to obtain a high-precision metallic nickel plate with an integrated three-dimensional microstructure.

[0060] The polymer film is pre-coated to give it good adhesion properties, and then enters the rotary printing line. A UV-curable resin is coated on the surface of the polymer film, and the micro-nano structure of the nickel plate is transferred under a pressure of 5-15 MPa. After being instantly cured by UV light, the film is rolled up to obtain the substrate.

[0061] like Figure 4 As shown, the substrate for the transmission-type multi-wavelength image reconstruction optical element based on computational diffraction light provided by the present invention is manufactured using the above method. For the present invention, the substrate can achieve selective reproduction identification.

[0062] Furthermore, the substrate includes a base film, and a holographic information layer is disposed on the front side of the base film.

[0063] It is understood that the base film layer is usually a transparent polymer film containing a pre-coated layer, which is used to support the holographic structure layer. The holographic structure layer needs to be coated on the surface of the base film to provide a stable carrier medium. The pre-coated layer is used to provide the adhesion strength between the base film and the information layer. The glass, typically a high-borosilicate silicon substrate, has extremely high flatness and surface precision, and serves as a carrier for photosensitive adhesive adhesion in the photolithography process. The computational holographic information layer is a transmissive multi-wavelength selective reproduction computational holographic structure layer, coated on the surface of the base film for transferring micro-nano structures, and is usually an acrylate-based ultraviolet curable material.

[0064] In summary, the transmission-type multi-wavelength image reconstruction optical element and substrate fabrication method provided by this invention utilize wavelength multiplexing technology to hide multiple patterns within the same hologram, and achieve selective pattern reconstruction by changing the wavelength of the illumination light. For each pattern to be hidden, a hologram for a specific wavelength is calculated. These holograms for different wavelengths are then superimposed and encoded onto the same physical diffraction structure. When illuminated with white light (containing all wavelengths), all patterns are simultaneously reconstructed and superimposed, making them unrecognizable. However, when illuminated with a monochromatic point light source (a specific wavelength), only the pattern designed for that wavelength is clearly reconstructed, while other patterns fail to form a clear image due to severe aberrations, thus achieving selective reconstruction and providing good anti-counterfeiting effects.

[0065] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the scope of protection of the present invention.

Claims

1. A method for producing a transmissive multi-wavelength image reconstruction optical element, characterized by, The method comprises the following steps: acquiring a plurality of binary images containing hidden graphics and texts drawn by drawing software; inputting the binary images and corresponding reconstruction wavelengths into a computer diffraction optical imaging software, and using a point source method to calculate a target complex amplitude field of the binary images on a hologram plane at the reconstruction wavelengths to obtain a complex amplitude distribution of the binary images; superimposing a plurality of single complex amplitude distributions, completing multiple iterations at a plurality of set wavelengths, outputting a diffraction field when the iterations are completed, and generating a multi-wavelength selective reconstruction calculated holographic file according to the diffraction field; introducing the multi-wavelength selective reconstruction calculated holographic file into a photoetching machine, and engraving the glass according to the multi-wavelength selective reconstruction calculated holographic file to obtain a photoengraved glass plate; splicing a plurality of the photoengraved glass plates on a splicing machine to obtain the transmission type multi-wavelength image reconstruction optical element.

2. The method of producing a transmissive multi-wavelength image reproduction optical element according to claim 1, characterized by, The step of superimposing a plurality of single complex amplitude distributions, completing multiple iterations at a plurality of set wavelengths, outputting a diffraction field when the iterations are completed, and generating a multi-wavelength selective reconstruction calculated holographic file according to the diffraction field comprises the following steps: regarding the hidden graphics and texts as being composed of a plurality of discrete points, and calculating the target complex amplitude distribution of each discrete point on the hologram plane point by point; superimposing the complex amplitude distributions of the discrete points on the recording plane according to the superposition principle of light waves to obtain the multi-wavelength selective reconstruction calculated holographic file.

3. The method of producing a transmissive multi-wavelength image reproduction optical element according to claim 1, characterized by, The target complex amplitude field is as follows: wherein exp represents an exponential function, i.e. exp() = e(), e is a natural constant (approximately equal to 2.7); A is a reference light amplitude, j is an imaginary unit; X and Y are spatial coordinate variables, representing positions on a holographic two-dimensional plane, X represents a horizontal coordinate, and Y represents a vertical coordinate.

4. The method of producing a transmissive multi-wavelength image reproduction optical element according to claim 1, characterized by, The diffraction field is as follows: where U total represents the total light wave complex amplitude of a certain point on the two-dimensional plane (X, Y), which is the superposition of the complex amplitudes of three different light wave components at the point; ∑ is the summation operator, which means to sum the expression following it from i = 1 to i = 3; i is an index variable, which is used to distinguish different light wave components, and in the formula, i = 1, 2, 3 respectively represent the first, second and third light waves; exp represents the exponential function, i.e. exp() = e(), e is the natural constant, and e is equal to 2.7; A is the reference light amplitude; j is the imaginary unit; X and Y are spatial coordinate variables, which represent the position on the holographic two-dimensional plane, X represents the horizontal coordinate, and Y represents the vertical coordinate; and ϕi(X, Y) is the wavefront phase distribution of the i-th light wave component at different positions on the two-dimensional plane (X, Y).

5. The method of producing a transmissive multi-wavelength image reproduction optical element according to claim 1, characterized by, The step of introducing the multi-wavelength selective reconstruction calculated holographic file into a photoetching machine, and engraving the glass according to the multi-wavelength selective reconstruction calculated holographic file to obtain a photoengraved glass plate comprises the following steps: introducing the multi-wavelength selective reconstruction calculated holographic file into the photoetching machine, emitting laser beams from a laser of the photoetching machine, regulating and controlling the laser beams through an optical system of the photoetching machine to form exposure light spots with a wavelength of 200-500 nm, converging the light spots to the surface of a photoresist through an objective lens of the photoetching machine to perform point-by-point exposure, absorbing the energy of the light spots by the photoresist at the exposed positions to cause a decomposition reaction of the photoresist, leaving the non-exposed positions, and then removing the decomposed photoresist through development to obtain the photoengraved glass plate with a three-dimensional microstructure having a preset topography.

6. The method of producing a transmissive multi-wavelength image reproduction optical element according to claim 1, characterized by, The step of splicing a plurality of the photoengraved glass plates on a splicing machine to obtain the transmission type multi-wavelength image reconstruction optical element comprises the following steps: splicing a plurality of small-area photoengraved glass plates into a large-area resin plate on the splicing machine; The microstructure on the photoetching glass plate is transferred to the resin film by using a high polymer resin film to cover the photoetching glass plate, extruding ultraviolet curing material between the high polymer resin film and the photoetching glass plate by a plate register, curing under pressure and ultraviolet light source exposure, and transferring the microstructure on the photoetching glass plate to the resin film to obtain the transmission type multi-wavelength image reproduction optical element.

7. A transmissive multi-wavelength image reconstruction optical element, characterized in that, The transmission type multi-wavelength image reproduction optical element is prepared by using the preparation method of the transmission type multi-wavelength image reproduction optical element according to any one of claims 1-6.

8. A method of producing a receiver of a transmissive multi-wavelength image reproduction optical element, characterized by, The preparation method comprises the following steps: The transmission type multi-wavelength image reproduction optical element is used as a cathode, and a resin master plate is placed in an electrolytic cell to form a metal nickel layer on the resin master plate under electrolysis, and the metal nickel layer is peeled off to obtain a metal nickel plate. The microstructure is transferred to the polymer film by using the metal nickel plate on the polymer film, and the ultraviolet curing forming is performed to obtain the anti-fake film.

9. A receiver for a transmissive multi-wavelength image reproduction optical element, characterized in that The preparation method of the printing substrate based on the transmission type multi-wavelength image reproduction optical element of the diffracted light is used.

10. The receiver for a transmissive multi-wavelength image reproduction optical element according to claim 9, characterized in that, The printing substrate comprises a base film, and a holographic information layer is arranged on the front surface of the base film.

Images