CN115230363B - Optical anti-counterfeiting element, design method thereof and anti-counterfeiting product - Google Patents
Optical anti-counterfeiting element, design method thereof and anti-counterfeiting product Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
- B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
- B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
- B42D25/30—Identification or security features, e.g. for preventing forgery
Abstract
The embodiment of the invention provides an optical anti-counterfeiting element, a design method thereof and an anti-counterfeiting product, and belongs to the technical field of anti-counterfeiting. The optical anti-counterfeiting element is provided with a diffuse reflection curved surface which is approximately smooth, and the incident light can form approximately uniform brightness distribution within the range of not less than a preset observation angle set omega v after being reflected by the diffuse reflection curved surface; the diffuse reflection curved surface comprises a decorated curved surface area and an unmodified curved surface area, wherein the decorated curved surface area and the unmodified curved surface area have different reflection characteristics, and the decorated curved surface area corresponds to a pattern area of an animation frame; when the diffuse reflection curved surface is irradiated by the incident light, the modified curved surface areas jointly represent a pattern of dynamic characteristics, and the unmodified curved surface areas jointly represent a background of dynamic characteristics. The manufacturing process is simple, and dynamic characteristics such as color and/or brightness contrast can be flexibly realized.
Description
Technical Field
The invention relates to the technical field of anti-counterfeiting, in particular to an optical anti-counterfeiting element, a design method thereof and an anti-counterfeiting product.
Background
In order to prevent counterfeiting by means of scanning, copying and the like, optical anti-counterfeiting technology is widely adopted in various high-security or high-added-value products such as banknotes, financial notes and the like, and a very good effect is achieved.
At present, attractive technology is to combine a microstructure determined by plate making with a light-variable layer, as disclosed in chinese patents CN 102712207A and CN 107995894A, and modulate the brightness distribution of reflected light by a micro-reflecting surface designed in advance, so as to achieve a dynamic effect, and can superimpose an interference coating to achieve a combination of color change and dynamic effect. This generally produces a variety of motion effects of patterns, such as lines, circles, curves, or words, and may produce a three-dimensional perspective. However, in most cases, the color tone of the pattern and the background can be the same, the contrast relationship is also basically single, and it is difficult to realize dynamic characteristics of various colors or arbitrary contrast relationship.
An exhibition with three-dimensional depth effect can also be produced by a moire magnification construction based on micro lenses and micro patterns, as described for example in patent WO 2005/052650 A2. Here, a periodic display diagram made up of many small micropatterns is magnified with a grid made up of microlenses having similar but not identical periods. In this way, a stereoscopic sensation can be generated that is significantly in front of or behind the actual surface, or so-called orthogonal parallax motion can be generated. However, such a moire magnification configuration is disadvantageous in that it is relatively complicated to manufacture, requires two imprinting steps for the microlens and micropattern, and requires precise alignment between the two steps.
Finally, as described for example in patent WO2014/108303A1, magnetically aligned reflective pigments are aligned with magnets having a corresponding shape, thereby creating a bright (especially annular) dynamic effect that may include a depth effect. This effect is very bright and easily visible, but the required magnetic ink is expensive and the kind and resolution of the effect is limited by the available magnets and is difficult to adjust at will.
In addition to the disadvantages listed above, the above invention adopts a structure in the form of "cells", such as micro-reflective surfaces, pigment flakes, and micro-lens cells, and the abrupt change in slope and voids between the cells inevitably results in insufficient display area of the element and reduced resolution of the image. Therefore, there is a need to develop an optical security element that has sufficiently fine expressive force, simple manufacturing process, and flexible realization of dynamic characteristics such as color and/or contrast.
Disclosure of Invention
The embodiment of the invention aims to provide an optical anti-counterfeiting element, a design method thereof and an anti-counterfeiting product, and the optical anti-counterfeiting element is simple in manufacturing process and can flexibly realize dynamic characteristics such as color and/or brightness contrast.
To achieve the above object, an embodiment of the present invention provides an optical security element capable of exhibiting a dynamic characteristic, which is pre-designed as reproduction of a set of animated frames visible at a set of pre-set viewing angles Ω, the animated frames comprising a pattern area and a background area forming an optical contrast with the pattern area; the optical anti-counterfeiting element is provided with a diffuse reflection curved surface which is approximately smooth, and the incident light can form approximately uniform brightness distribution within the range which is not smaller than the preset observation angle set omega v after being reflected by the diffuse reflection curved surface; the diffuse reflection curved surface comprises a modified curved surface area and an unmodified curved surface area, wherein the modified curved surface area and the unmodified curved surface area have different reflection characteristics, and the modified curved surface area corresponds to the pattern area; when the diffuse reflection curved surface is irradiated by the incident light, the modified curved surface areas are jointly presented as the pattern of the dynamic characteristics, and the unmodified curved surface areas are jointly presented as the background of the dynamic characteristics.
Optionally, the diffusely reflective curved surface is periodic in at least one direction.
Optionally, the diffusely reflective curved surface is non-periodic in at least one direction.
Alternatively, the average distance between adjacent peaks and valleys of the diffusely reflective curved surface is from 5 μm to 100 μm, preferably from 10 μm to 30 μm.
Alternatively, the average height difference between adjacent peaks and valleys of the diffusely reflective curved surface is 1 μm to 10 μm.
Optionally, at least a portion of the unmodified region is smooth or has a secondary structure.
Optionally, the modified region is modified by one or more of the following: adding a secondary structure to the modified region; smoothing the modified region; flattening the modified region; providing the modified region with a protrusion or depression compared to the unmodified region; adjusting the angle of the modified region so that the incident light is reflected to a range beyond the preset observation angle set Ω; or the thickness of the plating or coating of the modified region is adjusted to be different from that of the unmodified region.
Alternatively, in the case where the modified region is modified by two or more of the plurality of means, the two or more means exist in parallel combination and/or serial combination.
Optionally, the secondary structure has a lateral feature size of 0.2 μm to 5 μm.
Alternatively, the width of the modified region is from 0.5 μm to 20 μm, preferably from 2 μm to 10 μm.
Optionally, the different reflection characteristics refer to one or a combination of the modified region and the unmodified region having different reflection colors, different reflection brightness, or different reflection textures when the incident light is irradiated.
Correspondingly, the embodiment of the invention also provides a design method for the optical anti-counterfeiting element, which comprises the following steps: designing an dynamic characteristic, wherein the dynamic characteristic is the reproduction of a group of animation frames visible at a preset observation angle set omega v, and the animation frames comprise pattern areas and background areas forming optical contrast with the pattern areas; designing a generally smooth diffusely reflective surface for the optical security element such that incident light, when reflected by the diffusely reflective surface, forms a generally uniform brightness distribution within a range not less than the predetermined set of viewing angles Ω; modifying an area corresponding to the pattern area of each animation frame based on the observation angle of each animation frame of the group of animation frames to form a modified curved surface area, so that the modified area and an unmodified curved surface area have different reflection characteristics, the modified curved surface area jointly presents the pattern of the dynamic characteristic when the diffuse reflection curved surface is irradiated by the incident light, and the unmodified curved surface area jointly presents the background of the dynamic characteristic.
Optionally, the diffusely reflective curved surface is periodic in at least one direction.
Optionally, the diffusely reflective curved surface is non-periodic in at least one direction.
Alternatively, the average distance between adjacent peaks and valleys of the diffusely reflective curved surface is from 5 μm to 100 μm, preferably from 10 μm to 30 μm.
Alternatively, the average height difference between adjacent peaks and valleys of the diffusely reflective curved surface is 1 μm to 10 μm.
Optionally, modifying, based on an observation angle of each animation frame of the set of animation frames, an area corresponding to the pattern area of each animation frame to form a modified curved surface area, including: pixelating each animation frame of the set of animation frames and the diffusely reflective surface; determining a first azimuth angle and a first pitch angle of each animation frame, wherein the first azimuth angle and the first pitch angle are determined according to the observation angle of the animation frame; determining a second azimuth angle and a second pitch angle of each pixel of the diffuse reflection curved surface, wherein the second azimuth angle and the second pitch angle are determined according to normal vectors at the pixels of the diffuse reflection curved surface; the following steps are performed for each animation frame of the set of animation frames: searching pixels corresponding to a second azimuth angle and a second pitch angle matched with a first azimuth angle and a first pitch angle of an animation frame at positions of the diffuse reflection curved surface corresponding to pixels of a pattern region in the animation frame, so that a region corresponding to the pattern region of the animation frame is formed in the diffuse reflection curved surface; and modifying an area corresponding to a pattern area of the animation frame formed in the diffuse reflection curved surface.
Optionally, searching for pixels corresponding to a second azimuth angle and a second pitch angle matched with the first azimuth angle and the first pitch angle of the pixels of the pattern area at the positions of the diffuse reflection curved surface corresponding to the pixels of the pattern area in the animation frame comprises: and searching pixels corresponding to a second azimuth angle of which the angle difference between the first azimuth angle and the second azimuth angle is in a first preset angle difference range and a second pitch angle of which the angle difference between the first pitch angle and the second azimuth angle is in a second preset angle difference range in a preset distance range of the diffuse reflection curved surface and the pixels of the pattern area in the animation frame.
Optionally, the preset distance range indicates a distance from a position of a pixel of a pattern area in the animation frame of less than 100 μm, preferably less than 50 μm; and/or said first predetermined range of angular differences means that the angular difference from said first azimuth angle is less than 3 °, preferably less than 0.5 °; and/or said second predetermined range of angular differences means an angular difference with said first pitch angle of less than 3 °, preferably less than 0.5 °.
Optionally, retouching an area corresponding to the pattern area of each animation frame to form a retouched surface area, including performing one or more of: adding a secondary structure to the modified region; smoothing the modified region; flattening the modified region; providing the modified region with a protrusion or depression compared to the unmodified region; adjusting the angle of the modified region so that the incident light is reflected to a range beyond the preset observation angle set Ω; or the thickness of the plating or coating of the modified region is adjusted to be different from that of the unmodified region.
Optionally, the dynamic characteristic is one or a combination of translation, rotation, scaling, deformation, invisibility and yin-yang conversion; and/or the optical contrast is one or a combination of different colors, different brightness and different textures which are visible to human eyes.
Alternatively, the width of the modified region is from 0.5 μm to 20 μm, preferably from 2 μm to 10 μm.
Correspondingly, the embodiment of the invention also provides an anti-counterfeiting product using the optical anti-counterfeiting element.
Correspondingly, the embodiment of the invention also provides a data carrier, which is provided with the optical anti-counterfeiting element or the anti-counterfeiting product.
The optical anti-counterfeiting element provided by the embodiment of the invention has simple manufacturing process, can flexibly realize dynamic characteristics such as color and/or brightness contrast, and can display various multicolor dynamic characteristics macroscopically, and simultaneously has no directly identifiable arrangement rule microscopically, so that the difficulty of multi-dimensional enhancement counterfeiting such as microstructure design and manufacturing process is improved.
Additional features and advantages of embodiments of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain, without limitation, the embodiments of the invention. In the drawings, the illustrations are not drawn to scale for clarity. In the drawings:
FIG. 1 is a schematic illustration of the diffuse reflection of an area of a diffusely reflective curved surface of an optical security element to incident light;
FIG. 2 is an example of a design of a periodic diffuse reflective curved surface area;
FIG. 3 is an example of a design of a non-periodic diffusely reflective curved surface region;
FIG. 4 is an embodiment of determining a surface area to be modified based on an animation frame;
FIG. 5 is another embodiment of determining a surface area to be modified from an animation frame;
FIG. 6 is a schematic illustration of a partial or complete modification of a modified curved surface region;
fig. 7 is a schematic view of the use of an optical security element on a banknote.
Detailed Description
The following describes the detailed implementation of the embodiments of the present invention with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
In one aspect, embodiments of the present invention provide an optical anti-counterfeiting element capable of exhibiting a dynamic characteristic that is pre-designed as a reproduction of a set of animated frames visible at a preset set of viewing angles Ω, the animated frames comprising a pattern area and a background area that forms an optical contrast with the pattern area; the optical anti-counterfeiting element is provided with a diffuse reflection curved surface which is approximately smooth, and the incident light can form approximately uniform brightness distribution within the range which is not smaller than the preset observation angle set omega v after being reflected by the diffuse reflection curved surface; the diffuse reflection curved surface comprises a modified curved surface area and an unmodified curved surface area, wherein the modified curved surface area and the unmodified curved surface area have different reflection characteristics, and the modified curved surface area corresponds to the pattern area; when the diffuse reflection curved surface is irradiated by the incident light, the modified curved surface areas are jointly presented as the pattern of the dynamic characteristics, the unmodified curved surface areas are jointly presented as the background of the dynamic characteristics, namely, the modified reflecting surface elements jointly reproduce the pattern of the dynamic characteristics, and the unmodified reflecting surface elements jointly reproduce the background of the dynamic characteristics.
The different reflection characteristics refer to one or a combination of different reflection colors, different reflection brightnesses, or different reflection textures of the modified region and the unmodified region when the incident light is irradiated.
When the diffuse reflection curved surface is irradiated by incident light, the animation frame can be observed under the corresponding observation angle of each animation frame, wherein the pattern of the observed animation frame is represented by a decorated curved surface area, and the background of the observed animation frame is represented by an untouched curved surface area.
The "a group of animation frames visible in the preset observation angle set Ω v" in the embodiment of the present invention means that the observation angles correspond to the animation frames one by one, and one observation angle corresponds to one animation frame.
The dynamic characteristics in the embodiment of the invention essentially refer to dynamic characteristics which appear when the observation angle is changed. In principle, the viewing angle may be the angle of one or more of the three elements of the light source (i.e. the incident light), the element and the observer. For example, the optical security element or the article with the optical security element is held in the hand with the illumination source and eye position unchanged, and the designed dynamic characteristics can be seen by shaking the element back and forth or left and right, i.e. changing the angle of the optical security element. The present invention is to simplify the description by defining the viewing direction and thus the viewing angle by the line connecting the eyes of the observer with the point of view. It should be noted that this definition does not materially affect or limit any of the relevant aspects of the embodiments of the invention. The observation angle is a three-dimensional space parameter, so that the observation angle needs to be accurately described by being decomposed into at least two angles. For example, the pitch angle and the azimuth angle can be described together, and the included angles between the observation direction and three coordinate axes of x, y and z can be also used for describing together.
The pattern of the animated frames may be designed as letters, numbers, characters, symbols or geometric shapes (especially circles, ovals, triangles, rectangles, hexagons or stars, etc.). The dynamic characteristics described above generally refer to any translational motion, rotation, scaling, deformation, invisibility, yin-yang conversion, etc. of the design pattern that is presented by the element and is directly visible to the human eye, and may also be any combination of these dynamic characteristics. The translation may be designed to translate the design pattern in a specific direction, or may be designed to translate in multiple directions, with the translation direction being associated with the viewing direction. One common combination feature is that the shape changes, such as a circle illusion, to a square as the position of the design animation frame pattern changes. The dynamic feature can have the orthographic parallax motion behavior of the pattern, namely the motion direction of the pattern is always perpendicular to the change of the observation direction, and the dynamic feature further attracts the attention of an observer through the anti-intuitiveness phenomenon. The motion of the animated frame pattern may create a stereoscopic impression floating above or below the plane of the element by the principle of binocular horizontal parallax. The pattern may also include a plurality of sub-patterns exhibiting the same or different athletic performance and/or the same or different float heights or float depths. In particular, the pattern may comprise at least a first curve and a second curve, which curves appear as a first or second target curve located at a central position of the first or second region, respectively, when viewed from the first or second viewing direction, respectively. When the security element is tilted, the two curves preferably move in different (preferably opposite) directions, thereby creating a particularly dynamic appearance. It will be appreciated that in the same way, the pattern of the security element may also include more than two curves which may move in the same or different directions when the security element is tilted. For example, the curves in the form of alphanumeric strings may alternately exhibit different movement behaviors, such as alternately floating above or below the plane of the planar pattern area, and moving according to their floating height when tilted. For specific principles of various dynamic characteristics reference may be made to the prior patent texts CN 102712207A, CN 107995894A, WO 2005/052650 A2 etc. The terms "pattern" and "pattern area" may be used interchangeably in embodiments of the present invention.
The dynamic characteristics can be represented by a group of pictures generated by computer software such as digital calculation software, pattern processing software and the like in specific design. For example, using a bitmap in the format of bmp, design patterns of different colors and a common background of the patterns are represented by gray values of 0-255. Each picture corresponds to visual information presented to the human eye at a particular viewing angle, known as a frame of animation of the designed motion-sensing feature.
The observation angle set Ω v refers to that all preset dynamic characteristics can be seen when the observation angle of the human eye changes in the set. The optical security element may reflect illumination beyond the collection, but these reflected light rays may not be correlated with the designed animation feature, and may also provide darker or darker visual information to the animation feature. The set of viewing angles qv may be described in terms of azimuth and pitch angles, for example, azimuth angles may be designed to be 0-360 ° and pitch angles may be 0-35 ° or 10-50 ° etc., i.e. the dynamic characteristics may be seen in the region where the human eye is in the conical shape. The setting of the angle parameter depends on the purpose of the designer, the lighting environment owned by the observer, the viewing habit, etc.
The diffusely reflective curved surface S region may be oriented using pitch and azimuth angles. Of course, other parameters may be used to orient the curved surface regions, particularly parameters that are orthogonal to each other, such as two orthogonal components of the direction of the curved surface regions. To produce sufficiently fine patterns and continuously varying dynamic characteristics, the wave characteristic length of the diffusely reflective curved surface S, i.e., the average distance between adjacent peaks and valleys, is preferably less than the human eye' S recognition capability, which is typically about 100 μm at apparent distances, and closer distances will increase the resolution. Thus, the average distance between adjacent peaks and valleys is not preferably greater than 100 μm. On the other hand, too small a distance can produce significant diffraction of light, affecting the dynamic characteristic color stability. The lateral dimension is preferably from about 10 μm to about 30 μm, which is a distance of from about 5 μm to about 100 μm, which results in sufficiently fine features without producing significant diffractive iridescence. The average distance between the peaks and the valleys in the diffuse reflective curved surface S can be calculated by the following method. Selecting square region with area A from diffuse reflection curved surface S, finding out the number N of wave crests contained in the area A, and considering that the number of wave crests and wave troughs is basically the same, then obtaining the average distance
In the embodiment of the invention, the diffuse reflection curved surface S is continuous and smooth, namely the curved surface has no break points and cracks, and the curved surface has no edges and corners. Satisfy the first derivativeAre all substantially continuous. For example, the equation S (x, y) =sin (2πx/p x )sin(2πy/p y ) The defined curved surface is continuous and smooth in x and y directions, P x And P y Is the period in the x and y directions. The accuracy of actual fabrication is of course limited, and the object of the present invention can be achieved by approximately smoothing the diffusely reflecting curved surface S. In addition, the practical use does not require the diffuse reflection curved surface S to be smooth everywhere, and most areas, such as curved surfaces with more than 80 percent of areas, have smooth characteristics, so that the purpose of the invention can be achieved. The diffusely reflective curved surface S may be periodic in at least one direction, e.g. the diffusely reflective curved surface S may have periodicity in both x, y directions, e.g. a curved surface determined by the following expression:
S(x,y)＝sin(2πx/p x )sin(2πy/p y )。
wherein p is x Representing period in x-direction, p y Representing the period in the y-direction, x and y represent the argument.
Of course, it is also possible to have periodicity in only one direction (e.g., the x-direction), such as a curved surface determined by the following expression, which also satisfies the smoothness requirement.
S(x,y)＝sin(2πx/p x )。
In general, it is contemplated that a function with a period of P may be decomposed using a Fourier series, taking the one-dimensional periodic function S (x) as an example,
Wherein->
Conversely, the coefficient C may be set n N, a periodic function can be constructed using the following formula, where N is a positive integer.
For non-periodic diffuse reflective surfaces S, a random height matrix of the matrix may be generated using a computer program, the values of the height matrix representing a plurality of scattering points on the diffuse reflective surface S. The aperiodic diffuse reflection curved surface SS can be obtained by processing or blurring the matrix by a certain difference value.
The main function of the diffuse reflective curved surface S is to generate a uniform reflected light at a set viewing angle set qv, similar to the visual impression of diffuse reflection generated by general office paper. To achieve this, the orientation of the individual curved surface areas is selected within a continuous set of angles Ω, which orientation may be defined, for example, by azimuth and pitch angles. The angle continuum s is selected to reflect incident light uniformly at least into the observation angle set Ω, so that Ω covers a minimum set defined by the directions of incident light ωi and Ω together. Equivalently, the reflective curved surface S reflects incident light to a set of angles Ω r, Ω r covering a set of viewing angles Ω v, i.e. Ω v is a subset or proper subset of Ω r. In particular, Ω is designed as a minimum set determined jointly by the incident light directions ωi and Ω v, i.e. Ω v is identical to Ω r. For example, when incident light is normally incident on the element surface, i.e., the element is in the xy plane, the incident light is along the z direction, the azimuth angle of the element of Ω is the same as the azimuth angle of the element of Ω v, and the pitch angle of the element is half the pitch angle of the element of Ω v, according to the law of geometrical reflection.
In order to realize the dynamic characteristic, the diffuse reflection curved surface needs to be modified according to each pixel point of each animation frame, so that the reflection light distribution uniformly in the observation angle set omega v is changed. The size of the diffuse reflection curved surface should be larger than the size of the area occupied when all the animation frames are commonly presented, so that each animation frame can correspond to the diffuse reflection curved surface without scaling, and each pixel of the pattern area of the animation frame can find a corresponding position point on the diffuse reflection curved surface, and the position point is to be decorated.
According to the position Pv of the pattern area contained in a certain animation frame and the observed angle ωv thereof, the position Ps and the angle ωs of the curved surface area to be modified are found, for example, the position and the angle of the curved surface area to be modified can be found per pixel. In principle, pv and Ps should be the same position, and the reflection law of geometric optics needs to be satisfied between ωv, ωs and the angle ωi of the incident light, that is, the incident light, the reflected light, and the normal line of the curved surface area are in the same plane, and the incident angle is equal to the reflection angle. Here, ωs=f (ωv, ωi) indicates that there is a quantitative relationship among the three, and specific calculation formulas can be found in general optical textbooks, for example, born's optical principle: electromagnetic theory of light propagation, interference and diffraction. In a practical design, when pv=ps, the angle ωs of the curved surface region at this position may not exactly satisfy the geometric reflection law with ωv and ωi. Therefore, the curved surface area can be modified within a certain position range and a certain angle range, namely:
Ps∈(Pv-ΔP,Pv+ΔP)
ωs∈(f(ωv,ωi)-Δω,f(ωv,ωi)+Δω)
The position deviation deltap and the angle deviation deltaω are specifically determined according to the size of the curved surface area, the resolution of the human eyes on the angle and the size, and the designed dynamic characteristics, and the principle is that at least one curved surface area to be modified can be found, and meanwhile, no difference between the curved surface area and the design pattern is generated. The position deviation Δp is generally less than 100 μm, preferably less than 50 μm, and the angle deviation Δω is defined as the angle between the normal direction of the modified curved surface region and the normal direction of the curved surface region corresponding to the predetermined viewing angle of the pattern, and the angle deviation Δω should be less than 3 °, preferably less than 0.5 °.
In general, the pitch angles of the two curved surface regions are respectively defined as θ 1 ，θ 2 Azimuth angles are respectivelyThe angle between the normals of the two surface areas can be calculated by the following formula:
in particular implementations, each animation frame may be pixelated, and the diffusely reflective curved surface may be pixelated. In the alternative, only the pattern area of each animation frame may be pixelated. The essence of pixelation is that an animation frame is divided into, for example, nxM small areas, each of which may, for example, be very small in area. The small area into which a similar diffusely reflective surface is pixelized may also be very small. For example, the width of each small region according to the embodiment of the present invention may be 0.5 μm to 10 μm, preferably 2 μm to 4 μm, and the length of each small region may be 0.5 μm to 10 μm, preferably 2 μm to 4 μm.
Further, a first azimuth angle and a first pitch angle may be determined for each animation frame, each animation frame corresponding to a particular viewing angle one-to-one, such that the first azimuth angle and the first pitch angle may be determined based on the viewing angle of the animation frame. In the embodiment of the invention, the observation angle is a direction vector in a rectangular coordinate system. The angle between the direction vector and the xy-plane is defined as the pitch angle (also called the residual angle from the z-axis). The direction vector is projected onto the xy plane to form a projection vector, and the angle between the projection vector and the x axis is defined as the azimuth angle.
Further, a second azimuth angle and a second pitch angle of each pixel of the diffuse reflective surface may be determined, the second azimuth angle and the second pitch angle being determined from a normal vector at the pixel of the diffuse reflective surface. In the diffuse reflection curved surface, the azimuth angle of a pixel can be defined as the included angle between the normal vector at the pixel and the x-axis, and the pitch angle can be used for positioning the included angle between the normal vector at the pixel and the z-axis. In the xyz coordinate defined in the embodiment of the present invention, the xy plane is the plane where the optical anti-counterfeiting element is located, the x axis may be the longitudinal direction of the optical anti-counterfeiting element, the y axis may be the transverse direction of the optical anti-counterfeiting element, and the z axis may be the axis perpendicular to the optical anti-counterfeiting element.
The following steps may be performed for each animation frame of the set of animation frames: and searching pixels corresponding to a second azimuth angle and a second pitch angle matched with the first azimuth angle and the first pitch angle of the animation frame at positions of the diffuse reflection curved surface corresponding to the pixels of the pattern region in the animation frame, so that a region corresponding to the pattern region of the animation frame is formed in the diffuse reflection curved surface. For example, the set of animation frames may be projected vertically onto the diffusely reflective surface in equal proportions such that a location on the diffusely reflective surface corresponding to each pixel in each animation frame may be determined. Finding pixels corresponding to a second azimuth and a second pitch that match a first azimuth and a first pitch of an animation frame may include: and searching pixels corresponding to a second azimuth angle, in which the angle difference between the pixels and the first azimuth angle is within a first preset angle difference range, and a second pitch angle, in which the angle difference between the pixels and the first pitch angle is half of the first pitch angle, within a second preset angle difference range, in a preset distance range of the diffuse reflection curved surface and the pixels of the pattern area in the animation frame. Alternatively, in the case of a small pitch angle, the difference in azimuth angle becomes less important. Therefore, in the case where the pitch angle is relatively small, the pixel corresponding to the second pitch angle in which the angle difference between the first pitch angles is one half of the second preset angle difference range can be found only in the preset distance range without considering the azimuth angle. The preset distance range indicates a distance from a position where a pixel of a pattern area in the animation frame is located of less than 100 μm, preferably less than 50 μm. The first predetermined angular difference range means that the angular difference from the first azimuth angle is less than 3 °, preferably less than 0.5 °. The second predetermined angular difference range means an angular difference from one half of the first pitch angle of less than 3 °, preferably less than 0.5 °. For a pixel of the pattern area, one or more eligible pixels may be found in the diffuse reflective curved surface, each of which may be decorated. After finding the pixels in the diffusely reflective surface that match each pixel of the pattern area of the animated frame, these matching pixels form an area corresponding to the pattern area of the animated frame. And modifying the area corresponding to the pattern area of each animation frame formed in the diffuse reflection curved surface, so that a modified curved surface area can be formed.
The modification of the curved surface area can add a secondary structure in the modified curved surface area, and the characteristic dimension of the secondary structure is obviously smaller than that of the curved surface area, so that the secondary structure can be spread on the surface of the curved surface area along the trend of the curved surface area. The characteristic dimensions of the curved surface region of the diffusely reflective curved surface may be characterized by the average distance between adjacent peaks and valleys. The secondary structure has a lateral characteristic dimension of 0.2 μm to 5 μm and can diffract or absorb visible light. The absorption effect can absorb incident light of a specific frequency set through a grating structure with a sub-wavelength scale by the principle of surface plasmon resonance absorption, so that the color of reflected light is changed, and the original reflection direction is maintained. Typically, when the depth of the sub-wavelength structure is relatively deep, such as 300nm to 700nm, efficient absorption can occur over a broader set of frequencies, thereby significantly reducing the brightness of the reflected light in that direction, i.e., the sub-wavelength structure becomes an optically absorptive or optically black structure.
The modified curved surface region may be integrally provided with the secondary structure prior to modification, while producing a uniform reflected light distribution within the collection of viewing angles qv, and providing specific color or brightness characteristics. Thus, the modification of the curved surface region may smooth a part or the whole of the modified curved surface region. For example, the secondary structure of the modified curved surface area is removed, so that the secondary structure generates specular reflection with higher reflectivity for the whole visible light wave band. Alternatively, at least a portion of the unmodified curved surface region may be provided to be smooth or with secondary structures.
The modification to the curved surface region may be to flatten the modified curved surface region so that the modified curved surface region can reflect incident light only to a specific one of the inversions. At other viewing angles, none or only little reflected light is provided by the modified region, resulting in a darker or darker visual perception than the other regions.
The modifying of the curved surface area may be to adjust an angle of the modified curved surface area, so that the modified curved surface area reflects all light rays incident to the modified curved surface area to a direction exceeding a preset observation angle set Ω. The pitch angle of the curved surface area is generally increased beyond a minimum set determined by the directions ωi and ωv of the incident light, i.e. the incident light is reflected beyond the set determined by ωv. The modified curved surface region provides no or little reflected light, thereby producing a darker or darker visual perception than other regions.
To create a pattern of sufficient contrast, the surface on which the modified curved surface region is located or the surface opposite the surface on which the modified curved surface region is located (e.g., the unmodified curved surface region) may be provided with a plating or coating. This includes reflection enhancing coatings (especially metallization layers), reflection enhancing coatings, reflective ink layers, absorbing ink layers, high refractive index material coatings, and high refractive index material coatings. The reflection enhancing coating, coating or reflective ink layer preferably has a color shifting effect, i.e. a change in hue of the color at different viewing angles, for example using a fabry perot interference structure. Alternatively, the reflective and curved areas may also be imprinted in the reflective ink layer or the ink absorbing layer.
The modification of the curved surface area can be to form a bulge or a recess on the modified curved surface area than the area with the periphery not modified; or the modification to the curved surface area can be that the plating or coating thickness of the modified curved surface area is different from that of the unmodified area. For example, there is a reflective coating, coating or ink on the modified curved surface area, while there is no reflective coating, coating or ink on the unmodified curved surface area; or no reflective coating, coating or ink in the modified curved surface area, and reflective coating, coating or ink in the unmodified curved surface area.
The modification to the curved surface region may be a combination of the above-described modification modes in a serial manner. For example, forming a depression lower in the modified curved surface area than in the unmodified curved surface area, then adding a secondary structure in the depression, and finally removing the reflective coating of the secondary structure area (namely, having a different thickness from the reflective coating of the unmodified curved surface area); alternatively, a depression is formed in the modified curved surface region lower than the unmodified curved surface region, and color ink is filled in the depression, wherein the thickness of the depression is obviously larger than that of the ink in the unmodified curved surface region. The modification to the curved surface area can be combined with a plurality of modification modes in parallel. For example, a flat depression is formed in a portion of the modified curved surface region, and a secondary structure is added to another portion of the modified curved surface region along the direction of the curved surface region. The modification to the curved surface area can be the re-combination of the serial combination mode and the parallel combination mode of the modification mode.
In the embodiment of the present invention, the width of the modified region is 0.5 μm to 20 μm, preferably 2 μm to 10 μm, depending on the visibility of the generated pattern. The modified curved surface area has one or a combination of different reflection colors, different reflection brightness and different reflection texture compared with the unmodified curved surface area.
The modified curved surface areas are jointly presented as patterns of the animation frames in the observation angle set omega v, and the unmodified curved surface areas are jointly presented as the backgrounds of the animation frames. The pattern area has different optical contrast than the background area, and can be one or a combination of different colors, different brightness and different textures which are visible to human eyes.
Accordingly, embodiments of the present invention also provide a design method for an optical security element, which may include: designing an dynamic characteristic, wherein the dynamic characteristic is a group of animation frames visible at a preset observation angle set omega v, and the animation frames comprise pattern areas and background areas forming optical contrast with the pattern areas; designing a generally smooth diffusely reflective surface for the optical security element such that incident light, when reflected by the diffusely reflective surface, forms a generally uniform brightness distribution within a range not less than the predetermined set of viewing angles Ω; modifying an area corresponding to the pattern area of each animation frame based on the observation angle of each animation frame of the group of animation frames to form a modified curved surface area, so that the modified area and an unmodified curved surface area have different reflection characteristics, the modified curved surface area jointly presents the pattern of the dynamic characteristic when the diffuse reflection curved surface is irradiated by the incident light, and the unmodified curved surface area jointly presents the background of the dynamic characteristic.
The dynamic characteristics can be represented by a group of pictures generated by computer software such as digital calculation software, pattern processing software and the like in specific design. For example, using a bitmap in the format of bmp, design patterns of different colors and a common background of the patterns are represented by gray values of 0-255. Each picture corresponds to visual information presented to the human eye at a particular viewing angle, known as a frame of animation of the designed motion-sensing feature. The specific working principle and benefits of the design method for an optical security element according to the embodiments of the present invention may refer to the description of the optical security element according to the embodiments of the present invention, and will not be repeated here.
Correspondingly, the embodiment of the invention also provides an anti-counterfeiting product using the optical anti-counterfeiting element according to any embodiment of the invention. The anti-counterfeiting product can be in the forms of anti-counterfeiting lines, anti-counterfeiting strips, anti-counterfeiting marks and the like. Embodiments of the invention also provide a data carrier having a security element according to any of the embodiments of the invention or a security product according to any of the embodiments of the invention, which security element or security product may be arranged in an opaque region of the data carrier and in or over a transparent window region or through opening in the data carrier. The data carrier may in particular be a value document, such as a banknote (in particular a paper banknote, a polymer material banknote or a film composite banknote), a stock certificate, a ticket, a check, a high-value ticket, but also an identification card, such as a credit card, a bank card, a cash card, an authorization card, a personal identification card, or a personal information page of a passport, etc.
The optical anti-counterfeiting element and the manufacturing method thereof provided by the invention in real time are further described below with reference to the accompanying drawings.
FIG. 1 is a schematic representation of the diffuse reflection of an incident light ray by a diffusely reflective curved surface region of an optical security element. The plane of the optical security element 1 is defined as xy-plane, and the diffuse reflection curved surface S is formed by a plurality of smoothly connected curved surface areas 3. The first derivative of the two faces that are joined in the smooth joining finger of the present embodiment is continuous, that is, there is no joint but there is no break and no ridge. The curved surface area 3 can have protrusions and depressions. In fig. 1, the optical security element is provided with a substrate 6, on one side of which the diffusely reflective curved surface S is located. However, the presence of the substrate 6 is a requirement of the processing process, which may not be part of the optical security element itself. Substrate 6 may be part of the security product formed by optical security element 1. Of course, the substrate may also be removed from the security product, for example, in a thermoprinted product, the structural layer being transferred to another carrier, without the substrate 6 being part of the security product. The substrate 6 does not form an essential part of the optical security element 1. The incident light 4 is incident on one side of the substrate with the diffuse reflection curved surface, and the incident light 4 forms a plurality of reflected light rays 5 in different directions through the reflection effect of the diffuse reflection curved surface S. By controlling the angular distribution of the plurality of curved surface areas 3 (the angles being defined, for example, by azimuth and pitch angles), the substantially uniform diffuse reflection visual effect covers a predetermined set of viewing angles qv of the dynamic feature. For simplicity of description, the direction of the incident light 4 is set to the z direction, which is a direction perpendicular to the xy plane, without losing generality. Whereas the azimuth angle of the elements of the set qv is predetermined to be 0-360 deg., and the pitch angle is predetermined to be 0-35 deg.. Accordingly, the average distance between the peaks and the valleys of the diffusely reflective curved surface can be controlled to be in the range of 20 μm to 50 μm, and the longitudinal height is set to be 0 μm to 10 μm, so that the incident light 4 is reflected by the diffusely reflective curved surface S to the angle set Ω, which can cover the observation angle set Ω. Because a finite number is usually adopted to represent the continuous curved surface in practical design, the coverage of the present invention specifically means that any element in the set Ω can find a corresponding element close enough to it in Ω, for example, the included angle between the two elements is not more than 1 °. In practical design, the reflective smooth curved surface should at least contain 3000 peaks and valleys, preferably more than 50000 peaks and valleys, so as to generate a sufficiently fine and uniform reflected light distribution. Fig. 1 is only a view showing that the diffuse reflection curved surface of the optical anti-counterfeiting element can generate diffuse reflection effect on incident light, and the specific dynamic characteristics and the modification manner of the curved surface area are not involved.
To further illustrate the specific form that the diffusely reflective surface S may take, FIG. 2 illustrates a periodic diffusely reflective surface design. The analytical equation is adopted:
S(x,y)＝sin(2πx/p x )+sin(2πy/p x )+3 sin(2πx/p x )sin(2πy/p y )
where Px and Py are periods in the x and y directions, px=20 μm and py=30 μm may be set. This formula can produce a smooth diffuse reflective surface with periodicity in both the x and y directions. The pitch angle of each region of the diffuse reflection curved surface can be integrally adjusted by adjusting the overall undulating height of the diffuse reflection curved surface S as needed. The sine and cosine functions are both infinitely derivable, so that equation S (x, y) fully satisfies the continuous and smooth requirements. Let F (x, y, z) =z-S (x, y) =0, any pixel point (x 0 ,y 0 ,z 0 ) Normal equation and normal vector of (2)Can be calculated by the following formulas:
(x-x 0 )/F x (x 0 ,y 0 ,z 0 )＝(y-y 0 )/F y (x 0 ,y 0 ,z 0 )＝(z-z 0 )/F z (x 0 ,y 0 ,z 0 )
here, fx denotes the first derivative of the function F (x, y, z) with respect to x, fy denotes the first derivative of the function F (x, y, z) with respect to y, and Fz denotes the first derivative of the function F (x, y, z) with respect to z.
Can be directly derived from the normal vector (x 0 ,y 0 ,z 0 ) Azimuth angle phi (defined as the angle between the normal vector and the x-axis) and pitch angle theta (defined as the angle between the normal vector and the z-axis) of the curved surface region:
tan(φ)＝F y /F x |(x 0 ,y 0 ,z 0 )。
fig. 3 illustrates an aperiodic diffusely reflective surface design. For non-periodic diffuse reflective surfaces S, one method is to generate a matrix random height matrix using a computer program, the values of the height matrix representing a number of scattered points on the surface S. By processing or blurring the matrix by a certain difference, an aperiodic diffuse reflective curved surface S can be obtained. The difference processing may be bilinear interpolation, resampling using pixel region relation, bicubic interpolation of 4x4 pixel neighborhood, or Lanczos interpolation of 8x8 pixel neighborhood, and the blurring processing may be average blurring, defocus blurring, motion blurring, or gaussian blurring. The use of a difference or blurring process ensures that no abrupt changes or breaks exist between the heights, thus ensuring the smooth nature of the diffusely reflective surface, i.e., the first derivative is substantially continuous. Random heights may be generated using pseudo-random numbers, which are strings of numbers that appear random but are calculated by deterministic algorithms, so they are not truly random numbers in a strict sense. However, pseudo-random numbers are widely used because the statistical properties of pseudo-random selection (e.g., equal probability of individual numbers or statistical independence of successive numbers) are generally sufficient to meet the requirements of practical use, and unlike true random numbers, pseudo-random numbers are easily computer-generated.
And modifying a specific curved surface area of the diffusely reflecting area according to the animation frame forming the dynamic characteristic, thereby generating the reflecting characteristic of local difference. Setting the incident ray angle ωi to be along the z-axis direction, fig. 4 and 5 provide two examples illustrating how the curved surface area to be modified is determined.
FIG. 4 is an embodiment of determining a surface area to be modified based on an animation frame. The two tables of fig. 4 represent the pitch angle and azimuth angle, respectively, of the local curved surface region. Because of the limited sampling density of the discrete data, the data of the pitch angle and the azimuth angle in fig. 4 do not obviously show the smoothness of the diffuse reflection curved surface S, which does not affect the principle description of how to determine the area of the curved surface to be modified by using the animation frame in this embodiment.
7 is an animated frame of the described dynamic characteristics, which frame is defined as being observed in the pitch = 0 °, azimuth = 0 °.71 is the pattern area of the animated frame and 72 is the background area of the animated frame. 71 and 72 have optical contrast that is visible to the human eye. The size of the reflection area 21 corresponding to the animation frame 7 on the diffuse reflection curved surface S is at least not smaller than the size of the area where the animation frame 7 is located, so that the visual information of the animation frame 7 can be completely presented. Taking an arbitrary point Pv (also referred to as an arbitrary pixel point) on the pattern area 71 as an example, a corresponding point of Pv is determined in the reflection area 2. In the reflection region 21, a curved surface region having a pitch angle=0° or a deviation thereof smaller than Δω is found within the range of Δp with Pv as a center point. In the case of small pitch angles, the difference in azimuth angle becomes less important, and therefore consideration of azimuth angle is not given here. By properly controlling the magnitudes of Δp and Δω, it is always possible to find the corresponding point of any point Pv in the reflection area 21, i.e., to find the curved surface area to be modified. For example, the average distance between the adjacent peaks and valleys of the curved surface area is 30 μm, Δp=60 μm, Δω=1°, a point (0.4 °,75.2 °) can be found at the lower right side of the Pv point in the reflection area 2, and the modification of the curved surface area corresponding to this point can produce the expected visual contrast at the Pv point of the animation frame 7.
FIG. 5 is another embodiment of determining a surface area to be modified from an animation frame. The two tables of fig. 5 represent the pitch angle and azimuth angle, respectively, of the local curved surface region. Because of the limited discrete data sampling density, the pitch angle and azimuth angle data of fig. 5 do not obviously reflect the smoothness of the curved surface S, which does not affect the principle description of how the curved surface area to be modified is determined by using the animation frame in this embodiment.
In the animation frame 8, 81 is a pattern region of the animation frame 8, and 82 is a background region of the animation frame 8. The pattern region 81 and the background region 82 have an optical contrast that is visible to the human eye. The pattern region 81 has a change in position with respect to the above-described pattern region 71, and the animation frame 8 is defined as being observed in the direction of pitch angle=20°, azimuth angle=90°. The size of the reflection area 22 corresponding to the animation frame 8 on the diffuse reflection curved surface S is at least not smaller than the area size of the animation frame 8, so that the visual information of the animation frame 8 can be completely presented. Taking an arbitrary point Pw (also referred to as an arbitrary pixel point) on the pattern area 81 as an example, a corresponding point Pw is determined in the reflection area 22. In the reflection region 22, a curved surface region having the same angle as the curved surface region determined by the angle (pitch angle=10°, azimuth angle=90°) or having an angular deviation smaller than Δω is searched for in the range of Δp with Pw as the center point. By properly controlling the magnitudes of Δp and Δω, the curved surface region to be modified can always be found in the reflective region 22. For example, the average distance between the adjacent peaks and valleys of the curved surface area is 30 μm, Δp=60 μm, Δω=1°, points (10.1 °,92.2 °), (9.8 °,89.7 °) can be found near the Pw point in the reflection area 22, and the modification of the curved surface area corresponding to each of the two points can produce the expected visual contrast at the Pw point of the animation frame 8.
The modification of the curved surface region can take a variety of forms. The modified curved surface region 31 in fig. 6 is modified in a specific manner, either partially or wholly, to produce a different reflection characteristic than the unmodified curved surface region 32. 9 is an example of modification. Wherein:
91 is to form a recess in the periphery of the modified curved surface region (e.g., the unmodified curved surface region), the depth of the recess being selected from 0.5 μm to 3 μm and being related to the width of the modified region. Meanwhile, the modification to the curved surface area can be that the modified curved surface area is flattened, so that the modified curved surface area can reflect incident light to a specific reverse direction only, and under other observation angles, the modified curved surface area provides no or little reflected light, so that darker or darker visual perception is generated than other areas.
92 indicates that modification of the curved surface region may add a secondary structure at the modified region that has a feature size that is significantly smaller than the size of the curved surface region and thus may be spread across the surface of the curved surface region in the direction of the curved surface region. The secondary structure has a lateral characteristic dimension of 0.2 μm to 5 μm and can diffract or absorb visible light. The absorption effect can absorb incident light of a specific frequency set through a grating structure with a sub-wavelength scale by the principle of surface plasmon resonance absorption, so that the color of reflected light is changed, and the original reflection direction is maintained. Typically, when the depth of the sub-wavelength structure is relatively deep, such as 300nm to 700nm, efficient absorption can occur over a broader set of frequencies, thereby significantly reducing the brightness of the reflected light in that direction, i.e., the sub-wavelength structure becomes an optically absorptive or optically black structure.
93 indicates that the modified curved surface region may be integrally provided with said secondary structure prior to modification, while producing a uniform reflected light distribution within the set of viewing angles qv and providing specific color or brightness characteristics. Therefore, the modification of the curved surface area can smooth the modified curved surface area, namely, the secondary structure of the curved surface area to be modified is removed, so that the modified curved surface area generates specular reflection with higher reflectivity on the whole visible light band.
94 as a pattern that produces sufficient contrast, the surface on which the modified curved surface region resides or the surface opposite the surface on which the modified curved surface region resides (e.g., the unmodified curved surface region) may have a plating or coating. This includes reflection enhancing coatings (especially metallization layers), reflection enhancing coatings, reflective ink layers, absorbing ink layers, high refractive index material coatings, and high refractive index material coatings. The reflection-enhancing coating, coating or reflective ink layer preferably has a color shift effect, i.e. a change in hue of the color at different viewing angles, e.g. using a Fabry-Perot interference structure, e.g. Cr (5 nm)/MgF 2 (500 nm)/Al (50 nm) structure. Alternatively, the reflective and curved areas may also be imprinted in the reflective ink layer or the ink absorbing layer.
The modification to the curved surface area can be that the plating or coating thickness of the modified curved surface area is different from that of the unmodified curved surface area. For example, there is a reflective coating, coating or ink on the modified curved surface area, while there is no reflective coating, coating or ink on the unmodified curved surface area; or no reflective coating, coating or ink in the modified curved surface area, and reflective coating, coating or ink in the unmodified curved surface area.
95 indicates that the modifying the curved surface area may be to adjust the angle of the modified curved surface area, so as to reflect the incident light to a direction beyond the preset set of observation angles Ω. The pitch angle of the curved surface area is generally increased beyond a minimum set determined by the directions ωi and ωv of the incident light, i.e. the incident light is reflected beyond the set determined by ωv. The modified curved surface region provides no or little reflected light, thereby producing a darker or darker visual perception than other regions.
96 indicates that the modification of the curved surface region may be a combination of a plurality of modification modes in a serial manner. For example, forming a depression lower in the modified curved surface region than in the peripheral region, then adding a secondary structure in the depression, and finally removing the reflective coating of the secondary structure region (i.e. having a different thickness than the unmodified curved surface region); or forming a concave lower than the peripheral area in the modified curved surface area, and filling color ink in the concave, wherein the thickness of the concave is obviously larger than that of the ink in the unmodified curved surface area.
97 indicates that the modification to the curved surface region may be a combination of a plurality of modification modes in parallel. For example, a flat depression is formed in a portion of the modified curved surface region, and a secondary structure is added to another portion of the modified curved surface region along the direction of the curved surface region. The modification to the curved surface area can be the re-combination of the serial combination mode and the parallel combination mode of the modification mode.
The modified portion may be present in part or in whole of the modified curved surface region. For an ideal planar curved surface area, the modified portion will be equal to the modified curved surface area. Whereas for curved surface areas, the modified portion will be present locally to the modified surface area. The width of the modified region is 0.5 μm to 10. Mu.m, preferably 2 μm to 4. Mu.m. The modified curved surface area has one or a combination of different reflection colors, different reflection brightness and different reflection texture compared with the unmodified curved surface area.
A portion of the curved surface areas 31 and 32 of the diffusely reflective curved surface S in fig. 6 reflect the incident light 4 in directions 51 and 52, respectively. Wherein, the reflected light of the decorated surface area 31 generates the pattern of the animation frame, that is, the decorated surface area is jointly presented as the pattern of the animation frame; the reflected light of the unmodified surface area 32 creates the background of the animation frame, i.e., the unmodified surface area collectively appears as the background of the animation frame. The pattern area has different optical contrast than the background area, and can be one or a combination of different colors, different brightness and different textures which are visible to human eyes.
Fig. 7 shows a schematic representation of a banknote 10, the banknote 10 having an optical security element according to the invention, which is embedded within the banknote 10 in the form of a window security thread 101. In addition, the optical security element can be used in the manner of a label 102, and an open area 103 can be formed on the banknote substrate 10, so that light transmission observation is facilitated. It will be appreciated that the invention is not limited to security threads and banknotes but may be used in a variety of security products, for example in labels on goods and packaging, or in security documents, identity cards, passports, credit cards, health cards and the like. In banknotes and similar documents, in addition to security threads and labels, for example, wider security strips or transfer elements can be used.
An embodiment of the present invention provides a storage medium having a program stored thereon, which when executed by a processor, implements the design method for an optical security element according to any of the embodiments of the present invention.
The embodiment of the invention provides a processor, which is used for running a program, wherein the program runs to execute the design method for the optical anti-counterfeiting element according to any embodiment of the invention.
The embodiment of the invention provides an electronic device, which comprises a processor, a memory and a program stored on the memory and capable of running on the processor, wherein the design method for the optical anti-counterfeiting element according to any embodiment of the invention is realized when the processor executes the program.
The present application also provides a computer program product adapted to perform a program initialized with the steps of the design method for an optical security element according to any of the embodiments of the present invention when executed on a data processing device.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
In one typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.
The memory may include volatile memory in a computer-readable medium, random Access Memory (RAM) and/or nonvolatile memory, etc., such as Read Only Memory (ROM) or flash RAM. Memory is an example of a computer-readable medium.
Computer readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of storage media for a computer include, but are not limited to, phase change memory (PRAM), static Random Access Memory (SRAM), dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), read Only Memory (ROM), electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium, which can be used to store information that can be accessed by a computing device. Computer-readable media, as defined herein, does not include transitory computer-readable media (transmission media), such as modulated data signals and carrier waves.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article or apparatus that comprises an element.
The foregoing is merely exemplary of the present application and is not intended to limit the present application. Various modifications and changes may be made to the present application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. which are within the spirit and principles of the present application are intended to be included within the scope of the claims of the present application.
Claims (31)
1. An optical security element, characterized in that it is capable of presenting a dynamic characteristic pre-designed to be a reproduction of a set of animated frames visible at a set of preset viewing angles Ω, said animated frames comprising a pattern area and a background area forming an optical contrast with said pattern area;
the optical anti-counterfeiting element is provided with a diffuse reflection curved surface which is approximately smooth, and after the incident light is reflected by the diffuse reflection curved surface, approximately uniform brightness distribution is formed in a range which is not smaller than the preset observation angle set omega v;
the diffuse reflection curved surface comprises a modified curved surface area and an unmodified curved surface area, wherein the modified curved surface area and the unmodified curved surface area have different reflection characteristics, and the modified curved surface area corresponds to the pattern area;
When the diffuse reflection curved surface is irradiated by the incident light, the modified curved surface areas are jointly presented as the pattern of the dynamic feature, the unmodified curved surface areas are jointly presented as the background of the dynamic feature, wherein,
the decorated curved surface region is formed by decorating a region corresponding to the pattern region of each animation frame based on an observation angle of each animation frame of the group of animation frames visible at a preset observation angle set Ω, comprising:
pixelating each animation frame of the set of animation frames and the diffusely reflective surface;
determining a first azimuth angle and a first pitch angle of each animation frame, wherein the first azimuth angle and the first pitch angle are determined according to the observation angle of the animation frame;
determining a second azimuth angle and a second pitch angle of each pixel of the diffuse reflection curved surface, wherein the second azimuth angle and the second pitch angle are determined according to normal vectors at the pixels of the diffuse reflection curved surface; and
The following steps are performed for each animation frame of the set of animation frames:
searching pixels corresponding to a second azimuth angle and a second pitch angle matched with the first azimuth angle and the first pitch angle of the animation frame at positions of the diffuse reflection curved surface corresponding to pixels of a pattern region in the animation frame, so that a region corresponding to the pattern region of the animation frame is formed in the diffuse reflection curved surface; and
And modifying an area corresponding to the pattern area of the animation frame, which is formed in the diffuse reflection curved surface.
2. An optical security element as claimed in claim 1 wherein the diffusely reflective curved surface is periodic in at least one direction.
3. An optical security element as claimed in claim 1 wherein the diffusely reflective curved surface is non-periodic in at least one direction.
4. An optical security element as claimed in claim 1 wherein the average distance between adjacent peaks and troughs of the diffusely reflective curved surface is from 5 μm to 100 μm.
5. An optical security element as claimed in claim 4 wherein the average distance between adjacent peaks and troughs of the diffusely reflective curved surface is preferably from 10 μm to 30 μm.
6. An optical security element as claimed in claim 1 wherein the average height difference between adjacent peaks and troughs of the diffusely reflective curved surface is from 1 μm to 10 μm.
7. The optical security element of claim 1, wherein the locating pixels of the diffusely reflective curved surface corresponding to the second azimuth and the second pitch matched to the first azimuth and the first pitch of pixels of the pattern region at positions of the diffusely reflective curved surface corresponding to pixels of the pattern region in the animation frame comprises:
And searching pixels corresponding to a second azimuth angle, in which the angle difference between the pixels and the first azimuth angle is within a first preset angle difference range, and a second pitch angle, in which the angle difference between the pixels and the first pitch angle is half of the first pitch angle, within a second preset angle difference range, in a preset distance range of the diffuse reflection curved surface and the pixels of the pattern area in the animation frame.
8. The optical security element of claim 7 wherein,
the preset distance range indicates that the distance between the preset distance range and the position of the pixel of the pattern area in the animation frame is less than 100 mu m; and/or
The first preset angle difference range means that the angle difference between the first preset angle difference range and the first azimuth angle is smaller than 3 degrees; and/or
The second preset angle difference range means that the angle difference between the second preset angle difference range and the first pitch angle is smaller than 3 degrees.
9. The optical security element of claim 8 wherein,
the distance between the preset distance range indication and the position of the pixel of the pattern area in the animation frame is preferably less than 50 mu m; and/or
The first preset angle difference range means that the angle difference between the first angle of orientation and the first angle of orientation is preferably less than 0.5 °; and/or
The second predetermined angle difference range means that the angle difference from the first pitch angle is preferably less than 0.5 °.
10. An optical security element as claimed in claim 1 wherein at least a portion of the unmodified region is smooth or has a secondary structure.
11. The optical security element of claim 1 wherein the modified region is modified by one or more of the following:
adding a secondary structure to the modified region;
smoothing the modified region;
flattening the modified region;
providing the modified region with a protrusion or depression compared to the unmodified region;
adjusting the angle of the modified region so that the incident light is reflected to a range beyond the preset observation angle set Ω; or alternatively
The thickness of the plating or coating of the modified region is adjusted to be different from the unmodified region.
12. The optical security element of claim 11 wherein, in the event that the modified region is modified by two or more of the plurality of means, the two or more means are present in parallel and/or in series combination.
13. An optical security element as claimed in any one of claims 10 to 12 wherein the secondary structure has a lateral feature size of 0.2 μm to 5 μm.
14. An optical security element as claimed in claim 1 wherein the width of the modified region is from 0.5 μm to 20 μm.
15. An optical security element as claimed in claim 14 wherein the width of the modified region is preferably from 2 μm to 10 μm.
16. The optical security element of claim 1 wherein the different reflective characteristics refer to one or a combination of the modified and unmodified regions having different reflective colors, different reflective brightnesses, or different reflective textures upon the incident light.
17. A method of designing an optical security element, the method comprising:
designing an dynamic characteristic, wherein the dynamic characteristic is the reproduction of a group of animation frames visible at a preset observation angle set omega v, and the animation frames comprise pattern areas and background areas forming optical contrast with the pattern areas;
designing a generally smooth diffusely reflective surface for the optical security element such that incident light, when reflected by the diffusely reflective surface, forms a generally uniform brightness distribution within a range not less than the predetermined set of viewing angles Ω;
Modifying an area corresponding to the pattern area of each animation frame based on an observation angle of each animation frame of the set of animation frames to form a modified curved surface area such that the modified area has different reflection characteristics from an unmodified curved surface area,
when the diffuse reflection curved surface is irradiated by the incident light, the modified curved surface areas are jointly presented as the pattern of the dynamic feature, the unmodified curved surface areas are jointly presented as the background of the dynamic feature, wherein,
the modifying, based on the viewing angle of each animation frame of the set of animation frames, an area corresponding to the pattern area of each animation frame to form a modified curved area, comprising:
pixelating each animation frame of the set of animation frames and the diffusely reflective surface;
determining a first azimuth angle and a first pitch angle of each animation frame, wherein the first azimuth angle and the first pitch angle are determined according to the observation angle of the animation frame;
determining a second azimuth angle and a second pitch angle of each pixel of the diffuse reflection curved surface, wherein the second azimuth angle and the second pitch angle are determined according to normal vectors at the pixels of the diffuse reflection curved surface; and
The following steps are performed for each animation frame of the set of animation frames:
searching pixels corresponding to a second azimuth angle and a second pitch angle matched with the first azimuth angle and the first pitch angle of the animation frame at positions of the diffuse reflection curved surface corresponding to pixels of a pattern region in the animation frame, so that a region corresponding to the pattern region of the animation frame is formed in the diffuse reflection curved surface; and
and modifying an area corresponding to the pattern area of the animation frame, which is formed in the diffuse reflection curved surface.
18. The method of claim 17, wherein the diffusely reflective curved surface is periodic in at least one direction.
19. The method of claim 17, wherein the diffusely reflective curved surface is non-periodic in at least one direction.
20. The method of claim 17, wherein the average distance between adjacent peaks and valleys of the diffusely reflective curved surface is from 5 μιη to 100 μιη.
21. The method according to claim 20, wherein the average distance between adjacent peaks and valleys of the diffusely reflective curved surface is preferably 10 μm to 30 μm.
22. The method of claim 17, wherein the average height difference between adjacent peaks and valleys of the diffusely reflective curved surface is 1 μιη to 10 μιη.
23. The method of claim 17, wherein finding pixels corresponding to a second azimuth and a second pitch that match a first azimuth and a first pitch of pixels of a pattern region at locations of the diffuse reflective curved surface corresponding to pixels of the pattern region in the animation frame comprises:
and searching pixels corresponding to a second azimuth angle, in which the angle difference between the pixels and the first azimuth angle is within a first preset angle difference range, and a second pitch angle, in which the angle difference between the pixels and the first pitch angle is half of the first pitch angle, within a second preset angle difference range, in a preset distance range of the diffuse reflection curved surface and the pixels of the pattern area in the animation frame.
24. The method of claim 23, wherein the step of determining the position of the probe is performed,
the preset distance range indicates that the distance between the preset distance range and the position of the pixel of the pattern area in the animation frame is less than 100 mu m; and/or
The first preset angle difference range means that the angle difference between the first preset angle difference range and the first azimuth angle is smaller than 3 degrees; and/or
The second preset angle difference range means that the angle difference between the second preset angle difference range and the first pitch angle is smaller than 3 degrees.
25. The method of claim 24, wherein the step of determining the position of the probe is performed,
the distance between the preset distance range indication and the position of the pixel of the pattern area in the animation frame is preferably less than 50 mu m; and/or
The first preset angle difference range means that the angle difference between the first angle of orientation and the first angle of orientation is preferably less than 0.5 °; and/or
The second predetermined angle difference range means that the angle difference from the first pitch angle is preferably less than 0.5 °.
26. The method of claim 17, wherein modifying the region corresponding to the pattern region of each animation frame to form a modified surface region comprises performing one or more of:
adding a secondary structure to the modified region;
smoothing the modified region;
flattening the modified region;
providing the modified region with a protrusion or depression compared to the unmodified region;
adjusting the angle of the modified region so that the incident light is reflected to a range beyond the preset observation angle set Ω; or alternatively
The thickness of the plating or coating of the modified region is adjusted to be different from the unmodified region.
27. The method of claim 17, wherein the step of determining the position of the probe is performed,
the dynamic characteristics are one or the combination of translation, rotation, scaling, deformation, invisibility and yin-yang conversion; and/or
The optical contrast is one or a combination of different colors, different brightness and different textures which are visible to human eyes.
28. The method of claim 17, wherein the modified region has a width of 0.5 μm to 20 μm.
29. The method according to claim 28, characterized in that the width of the modified region is preferably 2 μm to 10 μm.
30. A security product using the optical security element of any one of claims 1 to 16.
31. A data carrier, characterized in that it has an optical security element according to any one of claims 1 to 16 or has a security product according to claim 30.
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| CN202110449712.1A CN115230363B (en) | 2021-04-25 | 2021-04-25 | Optical anti-counterfeiting element, design method thereof and anti-counterfeiting product |
| PCT/CN2022/073790 WO2022227741A1 (en) | 2021-04-25 | 2022-01-25 | Optical anti-counterfeiting element, design method therefor, and anti-counterfeiting product |
| EP22794222.4A EP4331857A1 (en) | 2021-04-25 | 2022-01-25 | Optical anti-counterfeiting element, design method therefor, and anti-counterfeiting product |
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| CN115230363A (en) | 2022-10-25 |
| WO2022227741A1 (en) | 2022-11-03 |
| EP4331857A1 (en) | 2024-03-06 |
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