AT521455A2 - Optical security device and manufacturing method - Google Patents

Abstract

A security device is disclosed including a substrate and one or more focusing elements or lens structures located on one side of the substrate. The security device includes a plurality of picture elements connected to each focusing element, the picture elements including at least a first and second group of picture elements. Each picture element can consist of pixels that are located in an object plane that can be viewed through the connected focusing element. Each picture element comprises a diffractive grating element or sub-wavelength grating element which, when illuminated by a light source, generates a diffraction image which can be viewed in a range of viewing angles around the device. Image elements of the first group are visible in a first range of viewing angles and image elements of the second group are visible in a second range of viewing angles. The security device is particularly suitable for use on security documents such as banknotes. A method of forming a security device is also disclosed.

Description

OBJECT OF THE INVENTION

The present disclosure relates to optically variable devices and methods for their manufacture and / or testing. In particular, the present disclosure relates to optical devices that include diffractive elements or structures in their structure. More specifically, the present disclosure relates to optical devices that produce an optically variable effect, including one or more color images and / or monochromatic or grayscale images.

GENERAL PRIOR ART

Optical security devices are often used in conjunction with valuable documents as a means of preventing unauthorized copying or counterfeiting. These security devices typically produce optical effects and / or features that can be difficult for a potential counterfeiter to reproduce. The optical effects and / or features can also be used to check the valuable documents.

Counterfeiting of banknotes and other important documents has recently become one due to the easy availability of color photocopiers and computer scanning equipment. become bigger problem. This technology provides counterfeiters with an easier way to copy valuable documents that are printed using traditional security printing technologies. In response, central banks and banknote printers have turned to technologies and devices that produce images that are associated with them / 72

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·· ·· · ·· ····· vary the changing angle of view and which therefore cannot simply be photographed.

Such devices, collectively known as optically variable devices (OVDs), have successfully reduced the occurrence of counterfeiting using computer scanning equipment. OVD technologies can create a variety of visual effects, including moving guilloche and graphic effects. OVD technologies include dot matrix hologram technology (EP 0 467 601 A2), KINEGRAM ™ technology (EP 105099, EP 330 738, EP 375 833), which was first used in Saudi Arabian passports in 1987 and later in 1990 in Austrian 5000 Schilling banknotes CATPIX ™ grid technology (PCT / AU89 / 00542) applied to plastic Australian ten-dollar banknotes issued in 1988 and Singaporean $ 50 plastic banknotes in 1990, PIXELGRAM ™ technology (US Patent 5,428,479) and EXELGRAM ™ - Technology (PCT AU / 94/00441) used for the first time on Australian opal stamps and Vietnamese bank checks issued in 1995.

The technologies PIXELGRAM ™ and EXELGRZXM ™ show portrait effects with a relatively high resolution, which change from pictures with positive tone to negative tone when the viewing angle is changed. High-resolution printed portraits have long been used as a security feature on banknotes due to the ability of the human eye to perceive defects or imperfections in an image of a human face. The technologies PIXELGRAM ™ and EXELGRAM ™ were developed accordingly, so that they include portrait OVD effects. However, these portrait effects were limited to near monochromatic images from a fixed / 72

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·· ·· · ·· ··· ··

Number of brightness levels or "grayscale values exist. PCT application PCT / AU97 / 00800, published under WO98 / 23979 with the title “Color Image Diffractive Device, the disclosure of which is incorporated here by cross-reference, expanded diffractive OVD imaging to produce full-color images.

However, there are limitations and difficulties in displaying diffractive OVD imaging on physical substrates. In particular, surface relief holograms and holographic stereograms that can be viewed under white light suffer from distortion and a loss of clarity when viewed with extended light sources (not point light sources). Regions of the image that are furthest from the plane of the hologram suffer the most. This occurs because, although vertical parallax has been eliminated to avoid spectral smearing, horizontal perspectives that determine dimensionality are sent in wrong directions by a light source that is even partially diffuse in the horizontal direction. This problem is exacerbated under expanded or diffuse light sources and at a distance above or below the image plane.

Various technologies have been used to create three-dimensional images, some of which are based on printing combined with lenticular optics. So far, print versions have been limited to a relatively low resolution. Holographic stereograms based on diffractive OVD imaging are capable of much higher resolution, although without the use of special lighting they generally have limitations as described above.

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·· ··

In the past, holographic stereograms were made by Pacific Holographies Inc. and others, and a workaround was to compromise by reducing the size and depth of the image. Despite these limitations, the results in typical lighting environments were difficult to view.

Therefore, there is a need to increase the security of valuable documents such as polymer banknotes using OVD technology that includes 3D imaging. These OVDs can use focusing elements such as microlens arrays and can include diffractive devices. There is also a need to address the limitations of displaying 3D images on physical substrates based on such diffractive devices.

SUMMARY OF THE INVENTION

Broadly, a first aspect provides a security device comprising:

a variety of focusing elements;

a plurality of picture elements connected to each focusing element, the picture elements including at least a first and second group of picture elements, each picture element being in an object plane that is viewable by the connected focusing element, each picture element being a diffractive grating element or sub-wavelength grating element which, when illuminated by a light source, is a / 72

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·· ·· · ·· ··· ··

Generates a diffraction image that can be viewed in a range of viewing angles around the device, and image elements of the first group are visible in a first range of viewing angles and image elements of the second group are visible in a second range of viewing angles.

In one form, the picture elements include three or more groups of picture elements to represent an image that can be viewed from different angles.

In one form, the diffraction image is a grayscale or monochromatic image that includes a variety of brightness levels across the entire image and / or a color image that includes a variety of colors.

In one form, each picture element comprises a red, green and blue sub-element.

In one form, the red, green and blue sub-elements each contain their own diffractive grating element or sub-wavelength grating element, the frequency and / or the division of the diffractive grating elements or

Sub-wavelength grating elements are different in the red, green and blue sub-elements, so that each sub-element produces a predetermined primary color when illuminated.

In one form, the red, green and blue sub-elements are arranged vertically as a stripe.

In one form, the red sub-element is on the top of a vertical strip of grid elements, the green sub-element is in the middle of the strip / 72

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and the blue sub-element is at the bottom of the strip.

In one form, the red, green and blue sub-elements are of the same physical size.

In one form, the lattice elements of the red, green and blue sub-elements have a size distribution and / or a spatial distribution corresponding to gray levels or brightness levels in connection with the sub-element.

In one form, each of the sub-elements includes an effective grating area that includes the diffraction grating element or the sub-wavelength grating element and a non-diffractive area that does not include any grating elements, and a brightness value of each sub-element is varied by the effective grating area within each sub-element and / or the non-diffractive area of the sub-element is changed.

In one form, the non-diffractive area within each of the red, green, and blue sub-elements is of equal size for a given pixel, thereby forming a grayscale image, or the non-diffractive area within each of the red, green, and blue sub-elements for one given picture element has a different size, thereby producing a color image.

In one form, each pixel includes a randomized diffraction grating with a randomized grating pitch and / or width to deflect incident light at different angles so that incident light deflected by the diffraction grating is scattered and / 72

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«· • ·· • ···· • · • · • · ·· « • · • · • · ··· • · • · • · ···· · · A * ·· 9 9 • ·· 999 99

viewable diffraction image is a grayscale image.

In one form, each pixel includes an effective grating area that includes the diffraction grating element or the sub-wavelength grating element and a non-diffractive area that does not include a grating element, and a brightness value of each picture element is varied by changing the effective grating area and / or the non-diffractive area of the picture element ,

In one form, the non-diffractive area includes a microstructured surface with light traps to create internal reflections of most of the incident light that cannot then be reflected out and away from the light traps.

In one form, the non-diffractive area has a reflective coating for specular reflection of incident light.

In one form, the non-diffractive area has a light-absorbing coating.

In one form, the picture elements are anamorphic and the picture elements are more preferably configured to have a rectangular shape, which means that the lengths of the picture elements are greater than the widths.

In one form, the resolution of the picture elements is 12 times or 10 times or 8 times or 4 times higher vertically than horizontally.

In one form, the diffractive grating element or sub-wavelength grating element is of a / 72

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Surface relief structure formed

In one form, the picture elements are formed from a radiation-curable ink.

In one form, the focusing elements are formed from a radiation-curable ink by printing and / or embossing.

In one form, the focusing elements contain refractive or diffractive partially cylindrical lenses or zone plates.

In one form, the viewable diffraction image is a three-dimensional image of a scene, an object and / or a person.

Broadly, a second aspect provides a security device comprising:

a variety of focusing elements;

a plurality of picture elements located in an object plane to be viewed through the focusing elements, the picture elements including at least a first and second group of picture elements, each picture element including a surface that is structured to diffuse scattering of incident light to effect, wherein the plurality of picture elements are arranged to produce an image that is viewable when illuminated by the incident light, and picture elements of the first group are viewable in a first range of viewing angles and picture elements of the second group in one second range of viewpoints are viewable.

In one form, the surface includes structured / 72

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is, to cause diffuse scattering of incident light, a randomized diffraction grating with an arbitrary grating division to deflect light of a given wavelength at different angles so that incident white light deflected by the arbitrary diffractive grating is dispersed and the viewable image is a grayscale image is.

In one form, the surface that is structured to cause diffuse scattering of incident light can include an array of arbitrarily arranged micromirrors that cause incident light to be diffusely scattered in different directions.

In one form, each pixel includes an effective grating area that includes the randomized diffraction grating element and a non-diffractive area that does not include a grating element, and a brightness value of each pixel is varied by changing the effective grating area and / or the non-diffractive area of the pixel.

In one form, the non-diffractive area includes any one or more of the following:

a microstructured surface with light traps to create internal reflections of most of the incident light that cannot then be reflected out and away from the light traps, a reflective coating for specular reflection of incident light, and a light absorbing coating.

In one form the picture elements are anamorphic and are / 72

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Pixels are more preferably configured to have a rectangular shape, which means that the lengths of the pixels are greater than the widths.

In one form, the resolution of the picture elements is 12 times or 10 times or 8 times or 4 times higher vertically than horizontally.

The viewable image is preferably a three-dimensional image of a scene, an object and / or a person.

In a third aspect, a method for forming a safety device is provided, comprising the following steps:

Providing a substrate;

Applying a plurality of focusing elements to a first surface of the substrate; and

Applying a plurality of image elements to an image surface of the substrate, which includes at least a first group of image elements and a second group of image elements, each image element being in an object plane that can be viewed through a connected focusing element, each image element being a diffractive grating element or A sub-wavelength grating element that, when illuminated by a light source, produces a diffraction image that is viewable in a range of viewing angles around the device, and wherein picture elements of the first group are visible in a first range of viewing angles and picture elements of the second group in a second range of viewing angles are visible.

In one form, the method further includes the step of / 72

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Applying a layer of embossable radiation curable ink to the substrate before it is embossed while it is soft and curing the ink by radiation to form the one or more focusing elements on one side of the substrate.

In one form, the diffraction image includes a grayscale image and / or a multicolor image.

In a fourth aspect, a security document is provided, including a security device according to the first or second aspect, or a security device manufactured according to the third aspect.

In one form, the security element or device is provided within a window or half window region of the security document.

In one form, the security document includes a banknote, passport, credit card, or check.

In one example, the image may include a portrait of an object, such as a human face, and groups of image elements or channels may represent the object from many different points of view. Projection views of the object can be captured so that the final stereogram creates an accurate three-dimensional image of this object. A technique for acquiring stereograms is described in an MIT thesis entitled “The Generalized Holography Stereogram by Michael W. Halle:

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http://www.media.mit.edu/spi/SPIPapers/halazar/halle91.pdf, the content of which is included here by reference.

In accordance with the present disclosure, diffractive devices (classic or directly writable) and multiple channels are used instead of ink to produce images with a much higher resolution. This enables the use of microscopic lenticular structures, which are required for high-resolution currency imaging, and “real color images”. Hybrid 2D / 3D computer graphics can also be integrated into photographic stereograms.

The one or more aspects of the present disclosure were previously unavailable because the manufacture of an inexpensive clean microlens substrate was relatively unknown. In any event, the prior use of multi-plexed lenticular lens images to produce three-dimensional as well as animated "flip images" has historically been limited to printed image elements that generally only contain printed lines or dots.

However, printing forms of this technology suffer from resolution limitations due to the nature of the ink and the narrow channels required to multiplex the images under lenticular lenses. This requires either thicker, lower resolution lenticular lenses or very rough black and white imaging. 3D lenticular images formed in ink are rough due to resolution limitations of commercial printing, as this can limit the number of channels or angle views.

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The applicant is not aware of any previous attempt to combine focusing elements, for example cylindrical microlenses, with diffractive stereograms. diffractive

Stereograms without the benefit of additional optical elements suffer from limitations as described above.

Any reference here to a patent document or other subject matter that is considered to be prior art is not to be conceded as a concession that that document or subject matter contains information that was part of common knowledge as of the priority date of any of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic diagram of a pixel of an optically variable diffractive device that includes three primary color subpixels.

Figure 2 is a schematic diagram of the manner in which a diffractive surface relief structure deflects incident light.

Figure 3 is a schematic diagram of a mechanism of a full color diffractive device.

Figure 4 shows a method for controlling the brightness of primary color sub-pixels.

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Figures 5A and 5B show another method for controlling the brightness of primary color sub-pixels.

Figure 6 shows an example of an OVD pixel structure with eight channels.

Figures 7A and 7B are schematic diagrams of two different shapes of pixels to produce a grayscale image.

Figures 8A and 8B are schematic diagrams of the operation of the grayscale pixel shown in Figure 7B.

FIG. 9 shows a cross-sectional view of an optical security device that includes an eight-channel OVD structure in accordance with an embodiment of the present disclosure.

FIG. 10 shows a cross-sectional view of an optical security device according to another embodiment of the present disclosure.

FIG. 11 shows a flowchart of a manufacturing process for an optical security device according to an embodiment of the present invention.

FIG. 12 shows a flow chart of a diffractive structure production process in connection with an optical security device according to an embodiment of the present invention.

FIG. 13 shows three different methods which are suitable for generating images in accordance with the present invention.

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Figure 14 shows how a device of the present disclosure is viewed through a viewer's left and right eyes.

DESCRIPTION OF PREFERRED EMBODIMENTS

DEFINITIONS

The security document

The term closes in the sense used here

Security document includes all types of documents and tokens of value and identification documents, including but not limited to the following: Currency elements such as banknotes and coins, credit cards, checks, passports, ID cards, securities and share certificates, driver's licenses, title deeds, travel documents such as flight and train tickets , Tickets and tickets, birth, death and marriage certificates and academic transcripts.

The invention is particularly, but not exclusively, applicable to security documents or tokens, such as banknotes, or identification documents, such as ID cards or passports, which are formed from a substrate to which one or more printing layers are applied.

The diffraction gratings and optically variable devices described here can also be used in other products, such as packaging.

Security device or feature

As used herein, the term security device or feature includes any of a large / 72

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Number of security devices, elements or features which are intended to protect the security document or security token from forgery, copying, modification or falsification. Security devices or features can be provided in or on the substrate of the security document or in or on one or more layers applied to the base substrate and can take a wide variety of forms, such as security threads embedded in layers of the security document ; Security inks such as fluorescent, luminescent and phosphorescent inks, metallic inks, iridescent inks, photochromic, thermochromic, hydrochromic or piezochrome inks; printed and embossed features, including relief structures; Interference layers; Liquid crystal devices; Lenses and lenticular structures; optically variable devices (OVD) that include reflective optical structures, including reflective surface relief structures and diffractive devices, including diffraction gratings, holograms, and diffractive optical elements (DOE).

Transparent windows and half windows

In the sense used here, the term window refers to a transparent or translucent area in the security document in comparison to the essentially cloudy region to which a print is applied. The window may be completely transparent so that it allows the transmission of light to be substantially unaffected, or it may be partially transparent or translucent, allowing the transmission of light in part without, however, allowing / 72

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Objects are clearly visible through the window area.

A window area can be in a polymer

Security document formed that has at least one layer of transparent polymeric material and one or more opacifying layers that are applied to at least one side of a transparent polymeric substrate by omitting at least one opacifying layer in the region that forms the window area. If opacifying layers are applied to both sides of a transparent substrate, then a completely transparent window can be formed by omitting the opacifying layers on both sides of the transparent substrate in the window area.

A partially transparent or translucent area, hereinafter referred to as a "half window," can be formed in a polymeric security document that has opacifying layers on both sides by omitting the opacifying layers on only one side of the security document in the window area so that the "half window is not completely transparent, but does allow some of the light to pass through without allowing objects to be clearly seen through the half window.

Alternatively, it is possible for the substrates to be formed from a substantially opaque material, such as paper or fiber material, an insert made of transparent plastic material being inserted into a cutout or a recess in the paper or fiber substrate in order to form a transparent window or to form a translucent half-window area.

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Cloudy layers

One or more opacifying layers can be applied to a transparent substrate to increase the opacity of the security document. An opacifying layer is such that L _T <L _o , where L _{o is} the amount of light that is incident on the document and L _{T is} the amount of light that is transmitted through the document. An opacifying layer can comprise any one or more of a variety of opacifying coatings. For example, the opacifying coatings can comprise a pigment, such as titanium dioxide, dispersed in a binder or carrier of a heat activated crosslinkable polymer material. Alternatively, a substrate made of transparent plastic material could be embedded between opacifying layers of paper or another partially or essentially opaque material, to which information can subsequently be printed or otherwise applied.

Embossable radiation curable ink

The term embossable radiation curable ink used here refers to any ink, varnish or other coating which can be applied to the substrate in a printing process and which can be embossed while it is being used it is soft to form a relief structure and can be hardened to fix the embossed relief structure. The curing process does not take place before the radiation curable ink is embossed, but it is possible that the curing process either after the embossing or at substantially the same time as / 72

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the embossing step takes place. The radiation-curable ink is preferably curable by ultraviolet (UV) radiation. Alternatively, the radiation-curable ink can be cured by other forms of radiation, such as electron beams or X-rays.

The radiation curable ink is preferably a transparent or translucent ink formed from a clear resin material. Such a transparent or translucent printing ink is particularly suitable for printing translucent security elements, such as sub-wavelength gratings, translucent diffractive gratings and lens structures.

In a particularly preferred embodiment, the transparent or translucent ink preferably comprises a UV-curable, clear, embossable, acrylic-based lacquer or such a coating.

Such UV curable varnishes can be obtained from various manufacturers, including Kingfisher Ink Limited,

Ultraviolet type product UVF-203 or the like. Alternatively, the radiation-curable embossable coatings can be applied to other compounds, e.g. B. nitrocellulose based.

It has been found that the radiation-curable inks and lacquers used here are particularly suitable for embossing microstructures, including diffractive structures such as diffraction gratings and holograms and microlenses and lens arrays. However, they can also be embossed with larger relief structures, such as non-diffractive optically variable devices.

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The ink is preferably imaged by ultraviolet (UV) radiation. Minted and hardened at the same time. In a particularly preferred embodiment, the radiation-curable ink is applied and embossed at substantially the same time in a gravure printing process.

Focus size H

As used here, the term focus size refers to the dimensions, typically an effective diameter or width, of the geometric distribution of points where rays broken by a lens intersect an object plane at a certain angle. The focus size can be inferred from theoretical calculations, ray tracing simulations or from actual measurements.

Focal length f

In the present description, focal length, when used with respect to a microlens in a lens array, means the distance from the vertex of the microlens to the position of the focus given by locating the maximum of the power density distribution when collimated radiation is incident from the lens side of the array (see Miyashita , "Standardization for micro lenses and micro lens arrays (2007) Japanese Journal of Applied Physics 46, p. 5391).

Measuring thickness t

The measurement thickness is the distance from the tip of a lens on one side of the transparent or translucent material to / 72

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Lens frequency and division

The lens frequency of a lens array is the number of lenses in a given distance through the surface of the lens array. The division is the distance from the tip of one lens to the tip of the neighboring lens. In a uniform lens arrangement, the division has an inverse relationship to the lens frequency.

Lens width W

The width of a lens in a microlens array is the distance from one edge of the lens to the opposite edge of the lens. In a lens arrangement with hemispherical or semi-cylindrical lenses, the width is equal to the diameter of the lenses.

Radius of curvature R

The radius of curvature of a lens is the distance from a point on the surface of the lens to a point where the normal to the lens surface intersects a line that extends perpendicularly through the tip of the lens (the lens axis).

Deflection height s

The deflection height or surface deflection s a / 72

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Lens is the distance from the top to a point at the

Axis cut through the shortest line from the edge of a lens that extends perpendicularly through the axis.

Refractive index n

The refractive index of a medium n is the ratio of the speed of light in a vacuum to the speed of light in the medium. The refractive index n of a lens determines the amount in which light rays reaching the lens surface are refracted, according to Snellius' law of refraction:

η ★ Sin (a) = n * Sin (Θ), where a is the angle between an incident beam and the normal beam at the point of incidence on the lens surface, Θ the angle between the refracted beam and the normal beam at the point of incidence , and η is the refractive index of air (a value of 1 can be taken as an approximation for η).

overlap angle

The lobe angle of a lens is the entire viewing angle formed by the lens.

Abbe number

The Abbe number of a transparent or translucent material is a measure of the dispersion (variation of the refractive index with wavelength) of the material. Adequate choice of an Abbe number for a lens can help minimize chromatic aberration.

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Subwellenlängengitterelement

A sub-wavelength grating element is a grating element that has a period or spacing between grating lines that is less than the wavelength so that the dominant deflected mode is the zero order. Effective properties can be independent of the period as long as the sub-wavelength is sufficient. Properties can also be tolerant of structural deformations.

Image pixels and sub-image pixels

Terms such as image element (s) and image pixels are used interchangeably throughout the description and are intended to have the same meaning. Terms such as sub-pixels, sub-image pixels and sub-elements should have the same meaning among themselves and be used interchangeably.

RGB color space (red, green, blue)

A wide range of colors can be created with the three primary colors red, green and blue. Each color image can be broken down into three images that include these primary colors. Each color image can have many levels of intensity brightness. For example, if 16 brightness levels are selected for each primary color, 4,096 different colors can be created.

An OVD device can create a portrait in the same way that a video monitor can display a portrait or image on a screen that breaks the image down into many elements or pixels. Referring to Figure 1 of the drawings, a single picture element or image pixel 10 is shown, the / 72

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includes a red (R), green (G) and blue (B) sub-element or sub-pixel 11, 12, 13 to provide the three primary colors with different brightness values. This mechanism can enable the reproduction of a wide range of colors with different hue or color values and a different intensity or brightness. If picture elements with primary colors of different brightness are generated, full-color pictures can easily be generated. RGB is a specific example of a particular color space used in embodiments described below, but other color spaces, including grayscale and / or single color systems, are also applicable to all embodiments of the invention.

Referring to Figure 2, when a grating period (or spatial frequency) d diffractive pixel 20 is illuminated by a collimated white light beam in normal incidence, light of different wavelengths, λ (or color) is deflected to different angles α which are subject to the equation :

(1) . λ sma = a

Only the first order of diffraction is considered here, since most of the light energy is deflected into the first order. If grids are generated with a single spatial frequency within a pixel of an OVD, the OVD produces monochromatic images. When a person observes an image on an OVD, there is usually a fixed angle of incidence (direction of the light source) and a fixed viewing angle, assuming that the viewer does not move much. Hence the viewing angle is α / 72

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From equation (1), outgoing deflected light in different wavelengths or colors can be achieved by varying d, the period of the gratings. We are mainly interested in the three primary colors red, green and blue, which have corresponding wavelengths λΐ, λ2 and λ3. You can go through tri-color grids

Subelements d2 and there as

Grids are deflected by or sub-pixels with a respective period di shown in Figure 3. When the white light is illuminated, such as a neon tube, α colored light is deflected from these subpixels at the same viewing angle according to the following equation:

, Αχ A-2 A3 ^{Sma =} £ ⁼ £ = £

For example, three primary colors with wavelengths λι = 600 nm, Ä2 = 500 nm and Ä3 = 450 nm and a viewing angle a = 30 degrees correspond to grating periods di = 1200 nm, d2 = 1000 nm and 03 = 900 nm for each subpixel 11-13, that each pixel forms 10.

It is understood that other combinations

Angle of incidence, angle of view and grating periods can be selected as disclosed above, as long as they have the diffraction equation 4 (sin0 _m + sinÖf) = τηλ. _{satisfy where} at θ _{± is} the angle at which the light is incident, 0 _{m is} the viewing angle, d is the separation of grating elements and m is the diffraction order.

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To achieve a full color, the brightness value of each primary color must also be controlled by the sub-pixels. There are many methods for controlling the brightness of deflected light from regions on the surface of an OVD, such as varying the grating depth, grating profile, and / or grating curvatures. Figures 4 and 5 illustrate two methods for controlling the brightness of the RGB subpixels 11-13.

In Figure 4, the brightness value of each sub-pixel 11-13 is varied by changing the effective area of grids within each sub-pixel. FIG. 4 shows a single image pixel comprising the RGB subpixels 11, 12, 13, the effective area of grids of each subpixel 11-13 being adjusted in height or in the area in order to represent a certain brightness value.

In each sub-pixel 11, 12, 13, the brightness of deflected light is proportional to the area of each diffracting structure 41-43 in connection with the respective sub-pixel 11-13. In other words, the brightness is proportional to the heights or areas of the diffracting structures 41-43, as distinguished from the flat areas 44-49 in connection with the sub-pixels 11-13, which have an absence of diffracting structures. An advantage of this arrangement is that the brightness of the subpixels 11-13 can be essentially linear with respect to the heights or ranges of the contracting structures 41-43.

Figures 5 (a) and 5 (b) illustrate another method of controlling the brightness of each primary color sub-pixel. This is done using a set of pallets, with the / 72

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contracting structures are aligned in variable directions to determine different levels of brightness. Figure 5 (a) shows 8 sub-pixels 51-58 aligned at 90 degrees according to the highest brightness value within the specified range. Figure 5 (b) shows 8 sub-pixels 51-58 aligned at different angles with a corresponding variation in brightness value within the palette, which is set between a highest (90 degrees) and a lowest (45 degrees) brightness value. It is also possible to combine brightness control techniques. For example, a change in the orientation of the diffraction grating is used to compensate for a decrease in the brightness of outer channels due to lens aberrations.

The structures described above can produce a full color image with a single channel, an image with a "single channel being the only diffractive image that is created by the surface relief structure. OVDs with multiple channels (ie diffractive devices that generate more than one diffraction image) are desired for stereoscopic applications, wherein different images can be viewed from different angles. For example, a number of “X channels may be required to observe a stereoscopic portrait, each channel representing a different viewpoint in connection with the portrait.

Spatially divided space can be one way to reach OVD devices with multiple channels. A fictional element or pixel region on the device can be divided into a plurality of channels, each channel having three color sub-elements or sub-pixels for red, green and / 72

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contains blue.

FIG. 6 shows an example of an RGB element or a pixel structure 60 for a full-color OVD with eight channels. The RGB pixel structure 60 includes the anamorphic image pixels 6168, with each entire image pixel 61-68 being represented by a trio of RGB sub-pixels 61R-68R, 61G-68G, 61B-68B arranged vertically in stripes. In the given example, each image pixel 61-68 has a vertical dimension of 96 μm and a horizontal dimension of approximately 8 μm, so that the resolution of each image pixel 61-68 is 12 times higher horizontally than vertically.

It is understood that the physical dimensions of the image pixels are generally determined by the number of image channels under each lens and the division of the focusing elements, such as lenticular lenses. The horizontal dimension of the image pixels can be any one between 4 and 10 micrometers and the vertical dimension of the image pixels can be in the range of 45 to 100 micrometers. The number of image channels can be any between 2 image channels and 16 image channels.

It is also understood that the projected diffractive imaging that can be viewed by an observer is determined by the image content that is stored in each image channel. For example, if the image content stored in each image channel is closely related to the image content stored in other image channels, each image channel representing a view of an object from a particular angle, the device may be configured to be a three-dimensional view project this object for the viewer. It is also / 72

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possible to achieve other types of diffractive optical effects, such as animation, morphing, zooming in / out, changing pictures and so on, when the viewing angle changes.

In a most preferred embodiment, the plurality of image channels are arranged to produce a true color of an image at a predetermined viewing angle. The present disclosure provides an OVD that has many advantages over conventional diffractive or lens structures, which include:

• The OVD feature works in a wide range of lighting conditions, including diffuse lighting and low lighting environments.

• The feature produces a sharp, well-defined image compared to stereogram images created by other methods.

• The OVD produces radiant diffractive effects and can be configured to create true color mixing effects.

• The OVD overcomes the limitations associated with traditional printing technologies and lenticular features.

An extremely high resolution of far more than the ability of most printers is required to form the multiple channels such as 4 channels, 8 channels, 10 channels or 12 channels under lenticular lenses used on documents such as banknotes. As mentioned above, the horizontal resolution of the image pixels can be as small as 4 microns, whereas with conventional printing methods such as engraving and offset printing due to the limited printing resolution that is inherent in any printing method, it is either impossible or / 72

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It is extremely difficult to print picture elements that have a resolution of less than 30 to 40 micrometers.

A means for displaying RGB images can result in essentially square subpixels that are divided into vertical RGB columns, the entire subpixel having the same resolution in both directions, although RGB subpixel divisions require a higher resolution.

In the example shown in Figure 6, the width of each channel is 8 microns, which would result in subpixels that are 8 microns high if square subpixels were used. Since the subpixels consist of diffractive gratings with a repetition in the order of 1 micrometer, only 8 grid lines can be recorded in such a subpixel. Adjusting the height of each diffractive area as described above to represent the brightness value of each image sub-pixel would limit the range of brightness values that could be displayed. If a wide range of brightness values is to be displayed, more diffractive grid lines must be used. Therefore, the image sub-pixels are selected to be anamorphic so that each is up to 4 times larger than wide.

Grayscale color space

In some circumstances, it may be desirable to produce 3D imaging that is a grayscale image. One way to generate a grayscale image is to balance the brightness levels between the red, green and blue subpixels so that the viewer's net impression of the portion of the subpixels, the diffractive / 72

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Structures, a mixture of the incoming colors (which would be nominally white for daylight) and from the entire RGB image is a desired grayscale level, which together with the other pixels creates a grayscale image. This situation is shown in Figure 7A, which shows the diffractive imaging layer under a portion of a single lenticular lens. The imaging layer has a four channel structure with two adjacent image pixels shown for each of the four channels.

Referring to channel 1, the neighboring pixels 100 and 102 each have red, green and blue sub-pixels (111, 112, 113 and 114, 115, 116, respectively). Each of these sub-pixels has a non-diffractive area that is used to vary the brightness level (108, 110, 118 and 119, 120, 121, respectively). In this example, the non-diffractive areas 108, 110 and 118 are of the same size to compensate for the level of brightness between each of the RGB subpixels. Likewise, the non-diffractive area 119, 120 and 121 in pixels 102 is also equally sized. Since the non-diffractive areas in pixel 100 are smaller than those in pixel 102, pixel 100 has a greater brightness level than that of 102. This variation in brightness level is used to create the desired grayscale image. For example, it is clear from FIG. 7A that the upper pixel in channel 2 and the lower pixel in channel 4 all have the smallest non-diffractive areas and thus the highest brightness levels. In this case, the grayscale image is visible from a specified angle of view that corresponds to the 1st order of diffraction of the RGB subpixels, which are naturally designed so that they are essentially the same as discussed above.

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Diffuse white

Alternatively, the 3D grayscale imaging can be generated by pixels with a portion having a surface structure for diffuse scattering of incident light and the remaining portion being sized to correspond to a predetermined brightness level. The diffuse scattering can be provided by a surface structure with a suitable roughness or is preferably provided by an arbitrary diffractive lattice structure, which is illustrated schematically in FIG. 7B. As with Figure 7A, Figure 7B shows the imaging layer under part of a single lenticular lens. Two adjacent image pixels are shown for each of the 4 channels. Referring to channel 4, the adjacent pixels 104 and 106 each have a randomized diffractive grating 123 and 125 and the non-diffractive areas 122 and 124, respectively. The randomized (or pseudorandomized) diffractive grids 123, 125 each have a grating pitch and / or width that varies in an arbitrary manner. As the incident light is deflected from each of the adjacent edges within the grating, the angle of the respective diffractive edges of zero order, first order, etc. (lines with positive interference) are generated for each different wavelength at different angles to the grating. Since the grating is randomized, this is also the diffraction angle (importantly the first order diffraction) for each wavelength of visible light, which effectively creates a diffuse reflection of the incident light. Therefore, the viewer sees an arbitrary or pseudo-arbitrary combination of numerous / 72

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different wavelengths that the eye combines as white light. As discussed above, the variance in non-diffractive areas of the diffuse light pixels 104, 106 enables a variance in brightness so that a grayscale image can be generated.

Figures 8A and 8B provide a schematic representation of an example of this effect. FIG. 8A is a schematic sectional view of the safety device 70.

The white light 130, 131 falls on the focusing elements in the form of the lenticular lenses 72, 73, 74. The lenticular lenses 72, 73, 74 are carried on a surface 75 of the transparent substrate 71, while the picture elements 77 and 78 are formed on the opposite surface 76 to provide a 4-channel OVD.

The lens geometry is such that parallel incident rays 130 are refracted into a focal strip 132, which includes the strip of pixels 132 within the channel 2. Similarly, the parallel rays of incident light 131 are focused by lens 173 onto the stripe of pixels 133 in channel 2 of adjacent pixels 78. Ideally, the width of the focal strips 132 and 133 should correspond to the width of the pixels, which is achieved by selecting the appropriate lens geometries and / or substrate thickness.

The light focused on the focal strips 132 and 133, which cover the pixels of the channel 2, is deflected out of the respective lenses 72 and 73. At viewing angle α, the deflected light 134, 135 is that of the grayscale pixels for channel 2, each with a brightness level determined by the size of their respective non-diffractive surfaces. On / 72

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in this way the combination of light from pixels 134, 135, etc. of channel 2 is combined to produce a grayscale image as viewed by the viewer.

Referring to Figure 8B, a single picture element or pixel 136 is shown schematically. Each pixel 136 has a surface area 140 with a surface 142 that is structured for diffuse diffraction of the incident light. In the embodiment from FIG. 8B, the structured surface is a randomized (or pseudorandomized) diffractive grating in which the grating division and / or width is arbitrary. In a particular form, the UV curable polymer that forms the image layer is patterned using known techniques such as UV embossing or casting to form a grid of parallel lines with an arbitrary width and an arbitrary spacing within a fixed range of Generate widths and spacings.

The incident white light 138 is deflected by the arbitrary grating 142 and forms diffraction patterns from each grating line. Since the grating division is arbitrary, this is also the zero order, first order, second order diffraction angle and so on for each wavelength in the white light 138. This arbitrary dispersion of the zero order, first order, second order diffraction angle 141 means, that by viewing pixel 136 from the viewing angle, an arbitrary collection of wavelengths 143 (λ _χ to λ _η ) is seen. While these wavelengths are taken from the full spectrum of visible light, assuming that the incident light contains the full spectrum of visible light, the viewer's eye combines the / 72

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......

different wavelengths to see white light or a close approximation to white light.

The level of brightness of the white light 143 seen by the viewer is determined by the extent of the non-diffractive area 137. The surface of the non-diffractive region 137 can be flat and unstructured, so that the incident light 138 predominantly passes through. However, the non-diffractive surface area can also have a coating such as a reflective metallic coating. In this case, the incident light 138 would be specularly reflected at an angle of reflection equal to the angle of incidence. When the device is viewed from this angle, the specular reflection of incident light overwhelms the light deflected by the randomized diffraction grating 142 and the device would appear bright white with no recognizable grayscale image. From other angles, however, the required contrast would be between the diffusely deflected light from the randomized grating 142 and the non-diffractive surface area 137 to produce the grayscale image.

The non-diffractive surface area 137 can also be structured and / or coated, for example, using UV casting or embossing techniques to increase light absorption. Light traps or so-called "moth eye structures, which are described in detail in W02005106601, are suitable surface microstructures for this purpose. In this case, the non-diffractive surface area 137 reflects very little of the incident light 138 regardless of the angle of incidence and provides a strong contrast with the diffusely deflected light 141 from the randomized grating 142. Furthermore / 72

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’· *’ ..........

microscopic light trap structures can be embossed into the non-diffractive surface 137 using the same molding or embossing tool that embosses the randomized diffraction grating 142, so that both sets of surface structures are precisely aligned.

As discussed above, with respect to the

Embodiment of the RGB color space, the brightness value of each pixel 136 varies by changing the size of the non-diffractive surface area 137. Increasing the size of the non-diffractive surface area 137 reduces the size of the randomized diffractive grating 142 (assuming that the pixel size 15 is constant). Therefore, the brightness level of light 143 of pixel 136 is also reduced.

Pixels with a surface area that is structured for diffuse scattering of the incident light to produce 3D grayscale images offer a wider range of viewing angles at which the grayscale image is seen in the desired diffuse color (i.e. white with normal diffuse incident white light). As discussed above, the images generated by the red, green, and blue sub-pixel embodiments show a true color version of the image only in a narrow range of viewing angles. The image is still visible from other angles, but not in real color, but instead the image varies according to the diffractive spectrum of the RGB pixels.

Another advantage of the embodiments of the diffuse grayscale pixels is the improved image resolution relative to embodiments with RGB subpixels. The combined area, / 72

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A difference in image resolution is not an obstacle to an OVD in which one group of pixels are diffuse pixels to produce a grayscale image and another group of pixels are RGB pixels for a color image, possibly the same image as the grayscale.

manufacturing techniques

FIG. 9 shows a cross-sectional view of an optical security device 70 that includes an OVD structure with eight channels. The optical security device 70 includes a layer of embossable radiation curable ink that is applied to a transparent or window area of the substrate 71 before being embossed while still soft to close the refractive lenticular focusing structures 72-74 on a side 75 of the substrate 71 form. Each focusing structure 72-74 can include a refractive cylindrical lens.

The ink can be cured by radiation to / 72

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38 ............

to fix embossed lenticular focusing structures 72-74. Each focusing structure 72-74 is formed such that its focal length is approximately equal to the distance to the opposite side 76 of the substrate 71. In some cases it may be desirable to have lenses that do not focus precisely on the image plane (see W02010099571, which is hereby incorporated by reference). Each focusing structure 72-74 simplifies the detection of the picture elements 77-79, which are located on the opposite side 76 of the substrate 71.

The picture elements 77-79 can be formed by radiation-curable ink, by embossing in a layer of such ink or by printing the radiation-curable ink in the desired pattern.

It is noted that the above method is the preferred method for producing suitable lenses and picture elements, but other methods may also be suitable.

The foregoing arrangement may produce an optical effect that is similar to lenticular-based optical variable devices and that may be visible to the eye through lenticular structures 72-74 that are positioned to sense diffractive pixels 77-79 on the opposite side 76 of substrate 71 , Each pixel 77-79 includes an eight channel OVD structure 60 that includes image pixels 61-68 (stripes) as above with reference to FIG. Each set of image pixels 6168 belongs to its own image or channel, so as a viewer who sees that the device changes the viewing angle, a different image or channel is visible / 72

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39 .......... ”will. Each image or channel can represent a full color portrait from one of eight different viewpoints. The net impression on a viewer who emerges from viewing eight different viewpoints is the creation of a stereogram of the image with an additional separation advantage via the lenticular focusing structures 72-74.

Figure 10 shows a cross-sectional view of an optical security device 80 that includes an eight channel OVD structure. The optical security device 80 includes a layer of embossable radiation curable ink that is applied to a transparent or window area of the substrate 81 before being embossed while being soft to form the diffractive lenticular focus structures 82-84 on one side 85 of the substrate 81 , Each focusing structure 82-84 can include a diffractive cylindrical lens or zone plate.

The ink can be cured by radiation to fix the embossed lenticular focus structures 82-84. Each focusing structure 82-84 can be formed such that its focal length equals the distance to the opposite side 86 of the substrate 81. Each focusing structure 82-84 can facilitate the detection of the picture elements 87-89, which are located on the opposite side 86 of the substrate 81. The picture elements 87-99 can be formed in the same manner as described with reference to FIG. 9. Each pixel 87-89 may include an eight channel OVD structure 60 as described above. The latter arrangement can produce a stereogram effect similar to that with reference to Figures 9/72

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is described.

FIG. 11 shows a flow diagram of a method for generating the structures according to at least one aspect of the invention. In particular, the structures that are required for both the lenses and the picture elements are formed by electroforming or by nanoprint microlithography in step 92. The structures created by the process in step 92 are then used to form suitable plates or disks to preferably emboss the structures in step 94 into a suitable medium, such as a radiation curable ink. This can be done in the same in-line system in a process known as "Double Soft Emboss Technology or DSET, or other similar technologies such as that disclosed in W02014070079 by Rolling Optics AB, which is hereby incorporated by reference is involved. Alternatively, the structures for the lenses and picture elements can be created separately and laminated together to form the final OVD.

As discussed above in the Summary of the Invention section, the image may include a portrait of an object, such as a human face, and groups of pixels or channels may represent the object from many different points of view.

Projection views of the object can be captured so that the final stereogram creates an accurate three-dimensional image of this object. A technique for acquiring stereograms is described in the aforementioned MIT work entitled “The Generalized Holography Stereogram by Michael W. Halle:

http://www.media.mit.edu/spi/SPIPapers/halazar/halle91.pdf.

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A simple stereogram model can consist of a single holographic plate containing a series of thin vertical slit holograms that are exposed side by side across the plate. Each slot can be individually exposed to an image projected onto a rear projection screen some distance from the panel. Once the hologram is developed, each slot can form an opening through which the image of the projection screen can be seen at the time that slot is exposed. The images projected onto the screen can include views of a scene or an object that are captured from many different points of view.

Alternatively, a type of stereogram described in the prior art is similarly generated from multiple two-dimensional images of an object or scene, but recorded along a horizontal path to capture multiple horizontal viewpoints of the object or scene. In this type of stereogram, the images captured in this way are projected onto a holographic plate from the direction in which they were originally taken. In one method, a plate is sequentially exposed several times with a constant reference to the images captured above. Another way to achieve an identical result is to generate an intermediate hologram that contains the individual perspective images from left to right. This intermediate hologram is then used as a master to project all images back to a plate on which the final hologram is generated.

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......

Of the above types of holograms, the most suitable for this invention is a variation in the method of capturing images individually. In order to generate the picture elements in groups that are viewed by the focusing elements, images taken from different perspectives can be focused and projected onto a holographic plate through a series of slits. These slots must be in the same centers as the focusing elements and with a width equal to the individual focusing element width divided by the number of images captured or projected at any rate.

A simpler method of generating the frames suitable for the groups of picture elements described here is the digital interlacing of the pictures taken above, resulting in a picture element arrangement which is identical to that described directly above. The above arrangement can address the shortcomings of prior art OVDs by relying on focusing elements to separate horizontal image channels. In particular, the imaging properties of the focusing elements may not depend on the angle of incidence of illuminating light; instead, the clarity of the image can be determined by the spatial relationship of the image elements to the focusing elements, which relationship can be fixed after embossing and can be independent of the lighting.

FIG. 12 shows a flowchart of a method for generating the picture elements according to at least one aspect of the invention. First, in step 102, suitable images are discussed as a series of / 72, as discussed in more detail below

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Frame added. Second, the images are processed in step 104 so that they are suitable for the image elements of the invention. In software this includes:

1. Place the frames at a specified depth

2. Cut into channels according to lens width and number of frames

3. Reassemble the image into a single intertwined image

4. Compress in the y-axis

5. Split the channels in RGB

6. Divide the channels into horizontal rows in order

Generate grayscale values that are reassembled as colors in the OVD

Then, in step 106, the digital output from step 104, which is a matrix of picture elements, is generated to form a structure, such as a plate or disk, that can be used to create the picture elements for the Replicate OVD.

FIG. 13 shows three methods for capturing the collection of two-dimensional images or frames, taken from different perspectives, which are required for holographic stereograms. A method 112 involves placing an object or person 112B on a turntable 112A and filming with a video or film camera 112C as it rotates. Images of the object or person 112B are captured from multiple perspectives 112D. Another method 114 involves placing a rail 114A in front of the scene / object / person 111B and moving a camera 1140 along the rail 114A while capturing video, film, or a series of images from different perspectives 114D. Another / 72

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'

Method 116 includes attaching a number of cameras 116C to rail 116A in the configuration of method 114 and simultaneously triggering all cameras 116C to capture images of object 116B from different perspectives 116D.

As shown in Figure 14, each of these techniques can take a series of images taken from different perspectives (1, 2 ... n) and when recombined holographically or multiplexed 118 for a lenticular stereogram, render the perspective images from their original angles , allowing viewer 120 to perceive the scene / object / person as three-dimensional. The viewer's eyes 122, 124 can see two images from two different perspectives 126, 128 since the images are displayed in the direction of the original angles from which they were taken.

In holographic stereograms, the various perspective images are separated by deflecting them to the original angle from which they were taken with the camera. One- and two-step methods that have been used to achieve this goal are well described in the literature.

One of the weaknesses of this type of holographic stereogram is that when an extended light source, e.g. B.

Neon lighting, office lighting, cloudy sky is used to illuminate the hologram, the different perspectives are mixed together and the image becomes blurry and indistinct, at least the parts of the (3D) image that are not in the plane of the hologram.

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In a 3D lenticular display, the various perspective views recorded above are multiplexed together to form an image matrix of intertwined vertical channels, which are then printed using typical printing inks. Then an array of vertical cylindrical lenses is roughly placed at the focal length of the lenses from this image matrix and all image channels associated with a particular angle are refracted in the same direction by the device, a direction unique to each perspective image. The multiplexed arrangement can be arranged so that the images are in the correct order. For example, if only 4 perspective images were used, the arrangement could be vertical slices of each image in order

1,2,3,4,1,2,3,4,1,2,3,4,1,2,3,4 ... etc. and each set can lie on four channels under one lens.

There are a number of methods for generating the OVD of the present invention described above. In all embodiments, a series of perspective images are obtained as described above. In the preferred embodiment, these perspective images are aligned from left to right such that the 3D image is generated at a predetermined depth relative to the device during the reconstruction. As an example, a point on an object is selected to be on the surface. All perspective images are shifted and / or cropped so that this point is in the same horizontal position in each image frame. Then the images are divided into columns and merged into a final image file consisting of all the arranged images, for example above

1,2,3,4,1,2,3,4,1,2,3,4,1,2,3,4 ... numbered with / 72

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Number. However, it should be made clear that each column remains in the original position of the original perspective image (after the horizontal shift to determine the image plane). For example, if the columns in the horizontal position in any file of which they were originally part were numbered, the numbering would be as follows:

1,2, 3,4,5, 6,7,8,9,19,10,11,12,13,14,15 ...

Another less desirable interlacing technique with lower resolution that gives a dimensionally equivalent result to the above example (with 4 image perspectives) would be the use of the columns

1,1,1,1,4,4,4,4,8,8,8,8,12,12,12,12 ...

One of the weaknesses of 3D lenticular displays is that the minimum width of the multiplexed slots is related to the resolution achievable by the printer, which inevitably means fewer images and / or larger lenses than ideal. However, these displays are not affected by advanced source lighting and are equally sharp with diffuse and point lighting.

The OVD device of the present invention addresses the disadvantages of these two 3D display technologies.

Holography can accommodate picture elements that are in the order of a few wavelengths of light, which allows extremely narrow channels to be used in the device. This can enable the use of much more perspective images or frames than in a similar printed display: it can also allow the use of smaller lenses, which increases the overall resolution of the image and makes the image thinner, easier to manufacture and less expensive.

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........

Since the 2D perspective images are multiplexed in the same way as in a printed 3D lenticular image, and because the lenses redirect these images to the correct angles, the horizontal separation of the different perspectives is not affected by the lighting and the image remains under less than ideal lighting sharp.

The embodiments of Figures 9 and 10 can produce an optical primary effect through the focusing structures 72-74, 82-84 that focus on the back 76, 86 of the substrates 71, 81 as described above, but can also produce an optical secondary effect if the picture elements 77-79, 87-89 are viewed from the rear of the substrates 71, 81. Applicant believes that the secondary effect is caused by the focusing structures 72-74, 8284, which provide surfaces that produce poor sampling by redirecting light back through imaging with a slightly greater preference. Moving the OVD device can change this reference point in imaging and cause the eye to see the OVD effect. Part of the light may be due to total internal reflection and part may be due to weak reflection that occurs from outer surfaces of the focusing structures 72-74, 82-84. A protective coating such as a transparent lacquer can be applied over the lenticular focusing structures 72-74, 82-84. The protective coating can be applied over the lenticular focusing structures 72-74, 82-84 as well as over other areas of the substrate 71, 81 in which the focusing structures 72-74, 82-84 are not present. The latter areas (not shown) may contain a 2D image, which may at least be visible when the / 72

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Device is rotated about an axis perpendicular to the plane of the device or rocked back and forth about an axis within the plane of the device. The 2D image can include a diffractive or non-diffractive structure, such as a color changing ink.

Preferably, the protective coating includes a high refractive index (HRI) coating, as this can help ensure that the optical effect created by the lenticular focusing structures 72-74, 82-84 remains visible even when the coating is thick Layer is applied that does not follow the contours of the lenses. In other embodiments, however, possible coatings can include a transparent, not strongly refractive lacquer.

In a manner similar to the focusing structures, coatings can also be applied over the picture elements 77-79, 87-89.

It can be noted that a suitable coating should have one or all of the following attributes, including: good adhesion to the substrate, highly transparent, generally colorless and robust. Possible coatings can include a transparent, not strongly refractive lacquer. Lacquer can refer to a material that leads to a relatively hard-wearing and protective finish. Exemplary transparent lacquers can include nitrocellulose and cellulose acetyl butyrate. Alternatively, the coating may include a high refractive index coating, which is a coating that is a small particle size, high / 72 metal oxide component

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Refractive index dispersed in a carrier, binder or resin. Such a high refractive index coating may contain solvents because it is a dispersion. If a coating with high

If this type of refractive index is used, it can be air-hardened or UV-hardened.

Alternatively, a coating with a high refractive index can be used using a non-metallic polymer, such as sulfur-containing or brominated organic polymers.

Advantages of the optical security device of the present invention may include:

1. Real 3D imaging can be mass-produced with increased depth and clarity in a relatively inexpensive form that can be integrated directly into existing banknote technology.

2. Details provided by high resolution diffractive imaging can be much larger than is currently possible with high throughput printing technologies.

3. 3D imaging can be easily distinguished from 2D imaging by a layperson. This and difficulties in counterfeiting or simulating such 3D imaging should lead to improved security.

4. 3D grayscale imaging generated from OVDs, which was produced using cost-effective, high-volume manufacturing techniques, can be viewed from a wide range of viewing angles and with higher image resolution than color images in the RGB color space / 72

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to be viewed as.

5. Additional security hurdles for a counterfeiter can

Include the following:

a) obtaining first stage photographic images of a person or place;

b) Developing OVD microtechnology to replicate or simulate stereographic diffractive channels;

c) developing specific cylindrical microlenses required for the above;

d) accurate registration of microlenses for stereographic imaging on a polymer substrate;

e) Since portraits are often used in the design of banknotes, the image used can capture a specific person at a specific time. This can significantly increase the difficulty of imitating a portrait.

6. The combination of two previously separate 3D technologies, namely microscopic lenses and diffractive image elements, can simplify the creation of a product that was previously not possible, namely a clear 3D portrait (or other image) on a banknote.

Finally, it is to be understood that various changes, modifications, and / or additions may be made to the above-described constructions and arrangements of parts without departing from the spirit or scope of the invention.

Claims (37)

claims: 1. Safety device, including: a variety of focusing elements; a plurality of picture elements connected to each focusing element, the picture elements including at least a first and second group of picture elements, each picture element being in an object plane that is viewable by the connected focusing element, each picture element being a diffractive grating element or sub-wavelength grating element which, when illuminated by a light source, produces a diffraction image that is viewable in a range of viewing angles around the device, and image elements of the first group are visible in a first range of viewing angles and image elements of the second group in a second Range of viewing angles are visible. 2. The security device of claim 1, wherein the picture elements include three or more groups of picture elements to represent an image that can be viewed from different angles. 3. The security device of claim 1 or 2, wherein the diffraction image is a grayscale or monochromatic image that includes a plurality of brightness levels across the entire image and / or a color image that includes a plurality of colors. 52/72 Scanned on Ζ1 / 10 / ΖΘ19-000009877.000000001 ·· · · · ·· ··· ·· 4. Security device according to one of the preceding claims, wherein each picture element comprises a red, green and blue sub-element. 5. The security device of claim 4, wherein the red, green and blue sub-elements each include their own diffractive grating element or sub-wavelength grating element, the frequency and / or division of the diffractive grating elements or sub-wavelength grating elements in the red, green and blue sub-elements being different, so that each Sub-element generates a predetermined primary color when illuminated. 6. Security device according to claim 4 or 5, wherein the red, green and blue sub-element are arranged vertically as a strip. , 7. The security device of claim 6, wherein the red sub-element is at the top of the vertical strip, the green sub-element is in the middle and the blue sub-element is at the bottom of the strip. 8. Security device according to one of claims 4 to 7, wherein the red, green and blue sub-element have the same physical size. 9. Safety device according to one of the preceding claims, wherein the grid elements of the red, green and blue sub-elements have a size distribution and / or a spatial distribution corresponding to gray levels or brightness levels in connection with the sub-element. 53/72 Scanned on Ζ1 / 10 / ΖΘ19-000009878.000000001 ·· · · · · · ··· ·· A security device according to any one of claims 4 to 9, wherein each of the sub-elements includes an effective grating area including the diffraction grating element or the sub-wavelength grating element and a non-diffractive area including no grating elements, and a brightness value of each sub-element is varied by changing the effective grating area within each sub-element and / or the non-diffractive area of the sub-element is changed. 11. The security device of claim 10, wherein the non-diffractive area within each of the red, green, and blue sub-elements is equal in size for a given pixel to thereby produce a grayscale image, or wherein the non-diffractive area within each of the red, green, and blue sub-element has a different size for a given picture element, thereby producing a color image. 12. The security device of claim 1, wherein each pixel includes a randomized diffraction grating with a randomized grating pitch and / or width to deflect incident light at different angles so that incident light deflected by the diffraction grating is diffused and the viewable diffraction image is a grayscale image is. 13. The security device of claim 12, wherein each pixel includes an effective grating area that includes the diffraction grating element or the sub-wavelength grating element and a non-diffractive area that does not include a grating element, and a brightness value of each picture element 54/72 Scanned on Ζ1 / 10 / ΖΘ19-000009879.000000001 ".......... 54 is varied by changing the effective grid area and / or the non-diffractive area of the picture element. 14. Safety device according to one of claims 10, 11 or 13, wherein the non-diffractive region includes a microstructured surface with light traps in order to generate internal reflections of the majority of the incident light, which cannot then be reflected out and away from the light traps. 15. Safety device according to one of claims 10, 11 or 13, wherein the non-diffractive region has a reflective coating for specular reflection of incident light. 16. Safety device according to one of claims 10, 11 or 13, wherein the non-diffractive region has a light-absorbing coating. 17. Security device according to one of the preceding claims, wherein the picture elements are anamorphic and the picture elements are more preferably configured so that they have a rectangular shape, which means that the lengths of the picture elements are greater than the widths. 18. Security device according to one of the preceding claims, wherein the resolution of the picture elements is vertically 12 times or 10 times or 8 times or 4 times higher than horizontal. 19. Safety device according to one of the preceding claims, wherein the diffractive grating element or sub-wavelength grating element from one 55/72 Scanned on Ζ1 / 10 / ΖΘ19-000009880.000000001 ·· ·· · ·· ··· ·· Surface relief structure is formed. 20. Security device according to one of the preceding claims, wherein the picture elements are formed from a radiation-curable ink. 21. Security device according to one of the preceding claims, wherein the focusing elements are formed by printing and / or embossing from a radiation-curable ink. 22. Safety device according to one of the preceding claims, wherein the focusing elements include refractive or diffractive partially cylindrical lenses or zone plates. 23. Security device according to one of the preceding claims, wherein the generated diffraction image is a three-dimensional image of a scene, an object and / or a person. 24. Safety device, including: a variety of focusing elements; a plurality of picture elements located in an object plane to be viewed through the focusing elements, the picture elements including at least a first and second group of picture elements, each picture element including a surface that is structured to diffuse scattering of incident light to effect, wherein the plurality of picture elements are arranged to produce an image that is viewable when illuminated by the incident light, and picture elements of the first group are viewable in a first range of viewing angles and picture elements of the second group in one 56/72 Scanned on Ζ1 / 10 / ΖΘ19-000009881.000000001 • · ·· · · · · · · ·· second range of viewing angles are viewable. 25. The security device of claim 24, wherein the surface structured to cause diffuse scattering of incident light includes a randomized diffraction grating with an arbitrary grating to deflect light of a given wavelength at different angles such that incident white light is from the random diffractive grating is deflected, scattered, and the viewable image is a grayscale image. 26. The security device of claim 24, wherein the surface structured to cause diffuse scattering of incident light may include an array of arbitrarily arranged micromirrors that cause incident light to be diffusely scattered in different directions. 27. Safety device according to one of claims 24 or 25, wherein each pixel includes an effective grating area that includes the randomized diffraction grating element and a non-diffractive area that does not include a grating element, and a brightness value of each pixel is varied by changing the effective grating area and / or the non-diffractive area of the pixel. 28. The security device of claim 27, wherein the non-diffractive area includes one or more of the following: a microstructured surface with light traps to block internal reflections of most of the incident light 57/72 Scanned on Ξ1 / 1Θ / ΞΘ18-ΘΘΘΘΘ888Ξ.88888888ί · .. ·· .. ·: · .. · which cannot then be reflected out and away from the light traps, a reflective coating for specular reflection of incident light, and a light-absorbing coating. 29. Safety device according to one of claims 24 to 28, wherein the picture elements are anamorphic and the picture elements are more preferably configured to have a rectangular shape, which means that the lengths of the picture elements are greater than the widths. 30. Safety device according to one of claims 24 to 29, wherein the resolution of the picture elements is 12 times or 10 times or 8 times or 4 times higher vertically than horizontally. 31. Safety device according to one of claims 24 to 30, wherein the viewable image is a three-dimensional image of a scene, an object and / or a person. 32. A method of forming a security device comprising the following steps: Providing a substrate; Applying a plurality of focusing elements to a first surface of the substrate; and Applying a plurality of image elements to an image surface of the substrate, which includes at least a first group of image elements and a second group of image elements, each image element being located in an object plane which can be viewed through a connected focusing element, each image element being a diffractive grating element 58/72 Scanned on Ζ1 / 10 / ΖΘ19-000009883.00000000: • · · · ··· ··· 58 ** or sub-wavelength grating element that, when illuminated by a light source, produces a diffraction image that is viewable in a range of viewing angles around the device, and wherein picture elements of the first group are visible in a first range of viewing angles and picture elements the second group are visible in a second range of viewing angles. 33. A method of forming a security device according to claim 32, further comprising the step of applying a layer of embossable radiation curable ink to the substrate before it is embossed while it is soft and curing the ink by radiation to one or the other to form multiple focusing elements on one side of the substrate. 34. The method of claim 32 or 33, wherein the diffraction image includes a grayscale image and / or a multicolor image. 35. Security document including a security device according to any one of claims 1-31, or security device made according to the method according to any one of claims 32-34. 36. The security document of claim 35, wherein the security element or device is provided within a window or half window region of the security document. 59/72 Scanned on Zl / 10 / Z019-00000988d.000000001 37. The security document of claim 36, wherein the security document includes a banknote, passport, credit card, or check.