Abstract: An article comprises a volume of material having at least one faceted or curved surface, and at least one diffraction grating on at least one surface of the article. The diffraction grating comprises a set of diffractive elements formed in a deformable layer attached to the surface of the article. A method comprises forming the set of diffractive elements by deformation of the deformable layer, and attaching the deformable layer to a surface of the article. The layer can be deformed to form the diffractive elements before or after it is attached to the surface of the article.

Abstract: Methods create images viewable under different selected angles on optical storage devices and other photosensitive surfaces and optical storage devices with super-imposed images. Generally, a photosensitive surface is exposed with multiple diffraction patterns creating super-imposed images. These diffraction patterns create super-imposed images on the photosensitive surfaces, which can be read by either a human or a computer.

Abstract: A security device, which is suitable in particular for improving the anti-forgery security of payment means, wherein the security device comprises a flat light reflection element. Several three-dimensional diffractive surface elements are arranged on a surface of the light reflection element. The surface elements comprise a diffraction grating on a light outlet surface. The diffraction gratings of a group of light surface elements are designed and/or arranged in such a way that an asterism is produced for an observer and/or an examination device.

Abstract: A technique for shaping droplets is disclosed. Multiple optical traps, or at least one variable geometry trap, are used to deform a droplet. The surface tension of the droplet is lowered to be comparable with the force which can be applied using the optical traps, for example by using a surfactant such as Aerosol OT, with heptane droplets in a solution of sodium chloride. Solidification of deformed droplets can be achieved using polymerization.

Abstract: An image display device includes a light source, a diffractive optical element adapted to diffract a light beam emitted from the light source, and a light modulation element adapted to modulate a diffracted light beam obtained by the diffractive optical element, and a diffraction characteristic of the diffractive optical element is controlled based on a diffractive optical element control signal provided to the image display device.

Abstract: A virtual image display device with an optical waveguide to guide, by internal total reflection, parallel pencil groups meeting a condition of internal total reflection, a first reflection volume hologram grating to diffract and reflect the parallel pencil groups incident upon the optical waveguide from outside and traveling in different directions as they are so as to meet the condition of internal total reflection inside the optical waveguide and a second reflection volume hologram grating to project the parallel pencil groups guided by internal total reflection inside the optical waveguide as they are from the optical waveguide by diffraction and reflection thereof so as to depart from the condition of internal total reflection inside the optical waveguide.

Abstract: An optical device is formed by hot stamping a demetallized hologram to an optically variable foil or to a coating of optically variable ink. In another embodiment a hologram is hot stamped to a banknote or document printed with a color-shifting ink.

Abstract: A virtual-image projector comprises a laser configured to form a narrow beam, first and second dilation optics, first and second redirection optics each having a diffraction grating, and a controller. The first dilation optic is arranged to receive the narrow beam and to project a one-dimensionally dilated beam into the second dilation optic. The second dilation optic is arranged to receive the one-dimensionally dilated beam and project a two-dimensionally dilated beam. The first and second redirection optics are each operatively coupled to a transducer. The first redirection optic is arranged to direct the narrow beam into the first dilation optic at a first entry angle. The second redirection optic is configured to direct the one-dimensionally dilated beam into the second dilation optic at a second entry angle. The controller is configured to bias the transducers to vary the first and second entry angles.

Abstract: Various embodiments of the present invention relate to enhancing the brightness of displays that employ illumination systems. In some embodiments, the illumination systems include light guides, diffractive microstructure, and light-turning features. The diffractive microstructure may be configured to receive ambient light at a first angle and produce diffracted light at a second angle greater than the first angle and greater than the critical angle for of light guide. The light is thereby guided within the light guide. The light-turning features may be configured to turn the light guided within the light guide out of a light guide and onto, for example, a spatial light modulator at near normal incidence.

Abstract: A projection display which includes first and second waveguide elements, wherein the first waveguide element has a two input regions for injecting image bearing light into the first waveguide element. In this manner, the total field of view of the image to be displayed at the second waveguide element is divided into two sub-images prior to injection of one sub-image into one input region and the other sub-image into the other input region of the first waveguide element. This results in a smaller first waveguide element, thereby reducing obscuration of an observers view of a forward scene over which to the image to be displayed is overlaid.

Abstract: The present invention is directed to a display which presents an image along a line of sight of an observer, such that the image is overlaid on a real world scene has a first waveguide and an image source device to inject the image into the first waveguide. The first waveguide has a first grating to direct the image internally and to output the image from the first waveguide. A second waveguide has a coupling grating to receive the image from the first waveguide and to direct the image along the second waveguide. The second waveguide has an exit grating to diffract the received image out of the second waveguide towards the observer. The exit grating diffracts the image out of the second waveguide off axis to a normal axis of the second waveguide.

Abstract: The present invention provides for a diffractive structure comprising a plurality of grooves each formed by a plurality of two-dimensional scattering and/or diffractive groove elements, aligned in a manner serving to provide for at least one diffractive optical effect and further a surface display device comprising a plurality of regions wherein each region has a diffractive surface relief structure as defined above and wherein the gratings of one of said regions at an angle relative to the gratings of another of said regions.

Abstract: A projection display 210 arranged to display an image to an observer 212 use waveguide techniques to generate a display defining a large exit pupil at the point of the observer 212 and a large field of view, whilst using a small image-providing light source device. The projection display 210 uses two parallel waveguides 214, 216 made from a light transmissive material. One waveguide 214 stretches the horizontal pupil of the final display and the other waveguide 216 stretches the vertical pupil of the final display and acts as a combiner through which the observer 212 views an outside world scene 220 and the image overlaid on the scene 220. In a colour display, each primary colour is transmitted within a separate channel R, G, B.

Abstract: An image-providing light source device 58 is arranged to inject a non-coherent and collimated image into waveguide element 60. Light forming the image is dispersed by an optical element 76 so as to occupy a continuum of angles within the waveguide 60. The optical element 76 and a grating 70 are arranged such that the light exiting the waveguide occupies a single angle. Thereby, pupil banding of light exiting the waveguide 60 is mitigated.

Abstract: A virtual image display device is provided which displays a two-dimensional image for viewing a virtual image in a magnified form by a virtual optical system. The virtual image display device includes an optical waveguide (13) to guide, by internal total reflection, parallel pencil groups meeting a condition of internal total reflection, a first reflection volume hologram grating (14) to diffract and reflect the parallel pencil groups incident upon the optical waveguide from outside and traveling in different directions as they are so as to meet the condition of internal total reflection inside the optical waveguide and a second reflection volume hologram grating (15) to project the parallel pencil groups guided by internal total reflection inside the optical waveguide as they are from the optical waveguide by diffraction and reflection thereof so as to depart from the condition of internal total reflection inside the optical waveguide.

Abstract: There is provided a light source unit which includes a luminescent light source which receives excitation light so as to emit light of a predetermined wavelength band, excitation light sources which shine excitation light on to the luminescent light source, a reflection space having the luminescent light source in an interior thereof and an emission space which emits luminescent light source light emitted from the reflection space from an emission port whose area is made smaller than the area of the luminescent light source and a projector which employs the light source unit.

Abstract: In various embodiments of the invention, an interferometric display device is provided having an external film with a plurality of structures that redirect light from an inactive area of the display to an active area of the display. Light incident on the external film that would normally continue towards an inactive area of the display is either reflected, refracted, or scattered towards an active area of the display comprising moveable and static reflective surfaces that form an optical cavity.

Abstract: The present invention relates to a grating image (12) for depicting at least one unscreened halftone image having multiple brightness levels, the grating image exhibiting multiple grating fields (22-1, 22-2, 22-3) that include in each case an electromagnetic-radiation-influencing grating pattern composed of a plurality of grating lines and that, when illuminated, produce in each case an areal region of the halftone image having the same brightness level.

Abstract: A system and method for uniform light generation in projection display systems. An illumination source comprises a light source to produce colored light, and a scrolling optics unit optically coupled to the light source, the scrolling optics unit configured to create lines of colored light from the colored light, and to scroll the lines of colored light along a direction orthogonal to a light path of the illumination source. The scrolling optics unit comprises a single light shaping diffuser to transform the colored light into the lines of colored light, an optical filter positioned in the light path after the light shaping diffuser, and a scrolling optics element positioned in the light path after the optical filter. The single light shaping diffuser is capable of simultaneously transforming colored light into lines of colored light having substantially uniform intensity to provide uniform illumination.

Abstract: A security element for securing valuable articles comprises an optically variable layer (18) that conveys different color impressions at different viewing angles, and a color-constant layer (17, 24). The optically variable layer (18) and the color-constant layer (17, 24) are stacked in a covering region (20), while at most one of the optically variable layer (18) and the color-constant layer (17, 24) is present outside (22) the covering region. The color impression of the stacked layers (18, 17, 24) in the covering region (20) and the color impression of the one layer (18) outside (22) the covering region are matched with each other when viewed at a predetermined viewing angle. Further, the color-constant layer comprises an ink layer (17) and a metal layer arranged below the ink layer (24).

Abstract: An exterior part (100) has a first structural color region (111) formed by a first linear peak-valley pattern including multiple linear grooves arranged in X direction, and a second structural color region (112) formed by a second linear peak-valley pattern including multiple linear grooves arranged in Y direction. The widths, depths, and pitches of the linear grooves are dimensions enabling the generation of diffracted light including structural colors. In the first structural color region (111), surfaces inclined in X direction (3 o'clock or 9 o'clock direction) are formed. In the second structural color region (112), surfaces inclined in Y direction (0 o'clock or 6 o'clock direction) are formed.

Abstract: A diffraction toy system comprises an optical viewing device that provides a diffraction optical viewing effect. The viewing devices can be a pair of eyeglasses having diffraction lenses. The system includes a child's play object that includes a light source. The play object can be nonwearable or wearable objects that can accommodate a light source, such as toy cars, trucks, swords, hats, belts, tiaras, and the like. The light source can be a light emitting diode, and the light source can emit colored light. The play object can be a light device that produces a light show. The system can include a number of viewing devices worn by multiple users, and the viewing devices can provide the same or a different diffusion optical effect. Backdrops, with or without light sources, can be includes to provide a further enhanced visual effect.

Abstract: The present invention relates to a grating image (30) for depicting a motif (24) that moves upon tilting the grating image (30) about a tilt axis (20), having two or more grating fields (32, 34, 36) having a viewing-angle-dependent visual appearance, that each include an electromagnetic-radiation-influencing grating pattern composed of a plurality of grating lines, and exhibit a preferred direction that establishes a viewing angle from which the appropriate grating field (32, 34, 36) is visually distinguishable, wherein, according to the present invention, the grating fields (32, 34, 36) are formed from a plurality of sub-regions nested within each other (32-i, 34-i, 36-i), and each grating field (32, 34, 36) displays a motif (24) view (24-A, 24-B, 24-C) that is shifted substantially along the tilt axis (20), wherein the viewing angles for the visual distinguishability and the shifts of the motif views (24-A, 24-B, 24-C) of the grating fields (32, 34, 36) are coordinated with each other such that, upon til

Abstract: A component for authenticating a document or a product including a plastic film having at least one embossed surface, a metallization layer at least partially covering the embossed surface, the film and the metallized layer forming an embossed film having a first zone producing a rainbow effect according to a first orientation of the component in relation to a lighting direction, the rainbow effect disappearing when the component is oriented substantially perpendicularly to the first orientation, and a second zone which has been partially demetallized and remetallized with a dielectric material producing an effect of being colored by a first color for the first orientation of the component and by a second different color for the orientation substantially perpendicular to the first orientation.

Abstract: The specification and drawings present a new apparatus and method for providing a wide field-of-view as well as illumination uniformity in exit pupil expanders (EPE) using stacked EPE substrates (or plates) with non-symmetric exit pupil expansion that use a plurality of diffractive elements for expanding the exit pupil of a display for viewing.

Abstract: A display device (500) comprises a micro-display (22) and imaging optics (24) to transmit a light beam (BO), and a diffractive beam expander (10) having an output grating (16). The combination of said micro-display (22) and said imaging optics (24) is together adapted to form a virtual image (710) which is observable through the perimeter (15) of said output grating (16) when said diffractive beam expander (10) is positioned to at least partially intercept said light beam (BO). The combination of said micro-display (22) and said imaging optics (24) may also be adapted to project said light beam (BO) onto an external screen (600) in order to display a real image (610). The display device (500) may comprise a movable optical component (10, 380) to switch the device (500) from a virtual display mode to a projecting mode.

Abstract: An optical combiner in which the number of parts used is lessened is made of a resin. The optical component comprises a first surface, a diffraction grating, and a second surface. The first surface is a surface providing first, second, and third lenses. The diffraction grating diffracts to a common optical path leading to the second surface light of the first wavelength incident on the first lens, light of the second wavelength incident on the second lens, and light of the third wavelength incident on the third lens. The second surface emits light incident thereon through the common optical path. The optical path from the first surface to the diffraction grating and the common optical path are constituted of the resin.

Abstract: A display includes light-scattering regions. Each of the light-scattering regions is provided with linear protrusions and/or recesses having the same longitudinal direction. The light-scattering regions are different from each other in the longitudinal direction.

Abstract: In a transmission grating as a dispersive element, diffraction efficiency is enhanced and manufacturing costs are considerably reduced. A dispersive element includes resin members for forming a diffraction grating, being composed of a plurality of diffraction grating members having a cross-sectional shape respectively surrounded by two straight lines such as a triangular shape, and metal members as light-shielding members each being formed on corresponding one of the diffraction grating members at one side of the diffraction grating member along any of the straight line and the curved line of the cross-sectional shape of the diffraction grating member formed by the resin member. The metal members are configured to reduce zero-order transmitted light with respect to incident light, and to enhance diffraction efficiency of first-order transmitted light.

Abstract: A projection display which includes first and second waveguide elements, wherein the first waveguide element has a two input regions for injecting image bearing light into the first waveguide element. In this manner, the total field of view of the image to be displayed at the second waveguide element is divided into two sub-images prior to injection of one sub-image into one input region and the other sub-image into the other input region of the first waveguide element. This results in a smaller first waveguide element, thereby reducing obscuration of an observers view of a forward scene over which to the image to be displayed is overlaid.

Abstract: The present invention is directed to a display which presents an image along a line of sight of an observer, such that the image is overlaid on a real world scene has a first waveguide and an image source device to inject the image into the first waveguide. The first waveguide has a first grating to direct the image internally and to output the image from the first waveguide. A second waveguide has a coupling grating to receive the image from the first waveguide and to direct the image along the second waveguide. The second waveguide has an exit grating to diffract the received image out of the second waveguide towards the observer. The exit grating diffracts the image out of the second waveguide off axis to a normal axis of the second waveguide.

Abstract: A zero order diffractive filter for polarised or unpolarised polychromatic light, comprises a grating line (10) microstructure (1) formed by a surrounding medium (12) with low index of refraction nlow and a waveguiding layer (11) with high index of refraction nhigh, the grating lines (10) having a period length ? that is smaller than the wavelength of light for which the filter is designed. A plurality of single nanostructures (2) with dimensions in the nanometre range is superposed on a first interface (13) between the surrounding medium (12) and the waveguiding layer (11).

Abstract: A near-eye display related apparatus and device is disclosed. The apparatus includes a housing configured to receive an optical engine, and a light guiding plate attached to the housing and configured to receive light representing an image from the optical engine, the light guiding plate includes a first diffractive grating adapted to incouple the light into the light guiding plate, and a second diffractive grating adapted to outcouple the light from the light guiding plate such that the light is received by an eye of a user wearing the apparatus. The light guiding plate has a contact surface portion configured to optically couple the light guiding plate to a transparent plate, The contact surface portion being adapted to be in physical contact with the transparent plate.

Abstract: The invention concerns an optical security element and a system for visualising items of concealed information comprising such an optical security element. The optical security element has a substrate layer in which a relief structure defined by relief parameters, in particular relief shape, relief depth, spatial frequency and azimuth angle, is shaped in the surface region defined by an X-axis and a Y-axis, for producing an optically perceptible effect. One or more of the relief parameters defining the relief structure are varied in the surface region in accordance with a parameter variation function. The surface region is divided into one or more pattern regions and a background region. One or more of the relief parameters defining the relief structure are varied in the one or more pattern regions in accordance with a parameter variation function which is phase-displaced in relation to the parameter variation function of the background region.

Abstract: A metameric optical structure is disclosed having first optical structures comprising diffractive flakes having diffractive structures thereon, and a second optical structures having non-diffractive flakes which may have other special effect properties, such as color shifting. At one angle of incidence or one viewing angle, near normal. The hues match and at other angles they do not match. The diffractive flakes are preferably magnetically aligned so that the grating structures are parallel. Disclosed is also an image formed of at least a first region of diffractive flakes and a second region of non-diffractive flakes wherein the regions are adjacent one another and wherein one of the regions forms a logo, symbol or indicia that appears or disappears in dependence upon the angle of viewing.

Abstract: A layered light guide structure has a number of planar light guides arranged in a stack to receive a number of different color light beams from the edge of the light guides. Each of the planar light guides has one or more diffractive structures imparted or provided on its upper surface. The diffractive structures on each light guide are configured to diffract light of a particular wavelength range so that they efficiently diffract the guided light within that light guide. The diffractive structure can be one or more keypad symbols such that the layered light guide structure can be used as a keypad. The symbols can be pixelized such that the pixels can have different color patterns. The diffractive structure can also be a simple patch so that the layered light guide structure can be used as a back-light source.

Abstract: There is provided a light source device which can miniaturize a two-dimensional image display device as small as possible. The light source device is provided with three coherent light sources (11a), (11b), and (11c) corresponding to red, blue, and green; prisms (12a) and (12c) for reflecting lights emitted from the coherent light sources (11a) and (11c); and a diffraction part (20) comprising a single volume hologram on which plural gratings are multiply-formed, which gratings diffract the light emitted from the coherent light source (11b), and the lights that are emitted from the coherent light sources (11a) and (11c) and reflected by the prisms (12a) and (12b) so that these lights propagate in the same optical path.

Abstract: The invention provides in particular for an achromatic diffractive diffuser comprising a surface relief diffractive device arranged such that, under illumination by ambient light, the diffractive effect serves to provide a uniform achromatic diffuser reflection into a defined viewing zone for observation by an observer, and also such that the achromatic diffractive replay of the device has a non-symmetric distribution of diffractive light intensity between positive and negative diffractive order such that the diffractive efficiency in the desired diffractive order is enhanced over that of the undesired order to provide an enhanced brightness achromatic device.

Abstract: [Problems] A higher forgery prevention effect is realized. [Means for Solving Problems] A display according to the present invention is characterized by includes a relief-structured region as an image-constituting element including recessed portions, protruding portions or both of them arranged two-dimensionally on one of main surfaces of a light-transmitting layer, and a reflection layer supported by the one of the main surfaces and covering at least a part of the relief-structured region, wherein a center-to-center distance of the recessed portions, protruding portions or both of them falls within a range of 200 nm to 500 nm. Further, it is characterized in that it comprises multiple relief-structured regions, and a shape, depth or height, the center-to-center distance and an arrangement pattern of the recessed portions, protruding portions or both of them in at least one of the relief-structured regions are different from those in other relief-structured region(s).

Abstract: This invention describes a general diffractive optics method that uses a plurality of diffractive elements on an optical substrate for expanding the exit pupil of a display of an electronic device for viewing. The method can be used for optical coupling in an optical device and it is characterized by extending of an exit pupil of an input optical beam in an output optical beam wherein the optical device comprises: an optical substrate and in-coupling, intermediate and out-coupling diffractive element disposed on the optical substrates, wherein periodic lines of the intermediate diffractive element comprise an angle ? with periodic lines of the in-coupling and of the out-coupling diffractive elements, respectively. The system can support a broad range of rotation angles (e.g., 0<?<70°) and corresponding conical angles and remains geometrically accurate.

Abstract: A multilayer thin film filter is disclosed an organic dielectric layer serving as a spacer layer in a Fabry-Perot structure. The dielectric has embossed regions of varying thicknesses wherein the thickness within a region is substantially uniform. Each different region of a different thickness produces a different color (shift). The size of one of the embossed adjacent regions is such that the color of said one region is uniform and cannot be seen by a human eye as different in color from the uniform color of an adjacent region thereto, and wherein the color within a region can be seen with magnification of at least 10:1. This serves as a covert color coding system useful as a security device.

Abstract: Various embodiments of the present invention relate to enhancing the brightness of displays that employ illumination systems. In some embodiments, the illumination systems include light guides, diffractive microstructure, and light-turning features. The diffractive microstructure may be configured to receive ambient light at a first angle and produce diffracted light at a second angle greater than the first angle and greater than the critical angle for of light guide. The light is thereby guided within the light guide. The light-turning features may be configured to turn the light guided within the light guide out of a light guide and onto, for example, a spatial light modulator at near normal incidence.

Abstract: A projection display is provided including a first plate-like waveguide (7), an image providing light source device (10 and 11) located to inject image bearing light into the first plate-like waveguide 7. An input means (12) is provided on the waveguide (7) to reflect the image bearing light internally along the waveguide (7). A transmission grating (13) within the first plate-like waveguide (7) is provided to output image bearing light from the waveguide (7). A second plate-like waveguide (8) is located co-planar with the first plate-like waveguide (7) and has a coupling grating (17) therein to receive the image bearing light from the first plate-like waveguide (7). The second plate-like waveguide (8) also includes an exit grating (18) therein for diffracting the received image bearing light, diffracted by the coupling grating (17) out of the second plate-like waveguide (8) towards a viewer (6).

Abstract: The invention relates to a light panel, comprising a light source (1) and a panel element (2). The panel element is manufactured from a substantially transparent material for transmitting light thereby. The panel element (2) is further configured as a waveguide panel, inside which the light beams propagate with total reflection and get outcoupled therefrom with a diffractive outcoupling system. An outcoupling system (2u), such as a grating structure or the like, is adapted to cover the entire panel element (2) as far as its light surface (2a) is concerned, such that divergent recesses and/or grooves of various sizes and/or shapes are used to produce divergent local gratings of various sizes and/or shapes, such as multi-shaped and/or binary pixels and/or units, having the filing factor, shape, profile and/or size thereof optimized in such a way that the diffraction efficiency is a function of place.

Abstract: The invention relates to an optically variable element which at least in surface portions has an interface embedded between two layers and which forms an optically effective structure, that interface having a free-form surface which appears three-dimensionally for a viewer. To emphasise that free-form surface the invention provides that the free-form surface is formed by a partial region of the interface, which is of a lens-like configuration and which produces a magnification, reduction or distortion effect. The invention also provides the use of such optically variable elements as a security element to prevent forgery of value-bearing documents or for articles to be safeguarded, in particular as part of the decorative layer arrangement of a transfer or laminating film.

Abstract: Disclosed herein is a raster scanning-type display device using a diffractive optical modulator. The raster scanning-type display device includes an optical illumination unit, a diffractive optical modulator, and a projection unit. The optical illumination unit radiates light, which is emitted from a light source, in a spot beam form. The diffractive optical modulator causes an element to modulate the spot beam incident from the optical illumination unit, and generate diffracted light whose intensity is adjusted and which has a plurality of diffraction orders. The projection unit generates an image by projecting the diffracted light incident from the diffractive optical modulator onto a screen in a scanning spot beam form and performing raster scanning in which horizontal scanning and vertical scanning are alternated.

Abstract: Provided are a reflective plate and a display, and a method of controlling a distribution of reflected light. The reflective plate includes a plurality of diffracting grating cells including gratings reflecting incident light, wherein the gratings are arranged at predetermined intervals, and at least one of an arrangement period and an arrangement direction of each of the gratings of the plurality of diffracting grating cells is adjusted to limit a distribution of reflected light.

Abstract: A product with a surface relief grating (SRG) image effect has a surface with rotational cuts effected therein to create the SRG image effect. The SRG image has an effect based on a rotational speed of a cutting tool effecting the cuts, a travel speed of a cutting tool effecting the cuts, and a depth of the cuts. A light source can be used to emit light on the surface of the product. In an SRG image machining process, a material and a cutting tool are provided. The material is contacted by the cutting tool to a predetermined depth. The cutting tool is rotated to cut the material at a predetermined rotational speed. The cutting tool is moved to cut the material at a predetermined travel speed. A SRG image effect is produced in the material through the contacting, rotating, and moving steps.

Abstract: A diffractive grating element is divided into at least two different grating regions each having different diffractive properties and arranged on opposite sides with respect to a transition point to form a splitted grating structure. The diffractions generated by the at least two different grating regions are arranged to mutually compensate for the variation in the input angle of the incident light wave to the total diffraction efficiency of the at least one diffracted light wave that is arranged to propagate within the substrate.

Abstract: Disclosed is a surface relief structure. The structure includes a recording medium configured to be structurally modified when exposed to interfering and non-interfering portions of radiation beams, the structurally modified recording medium including, when viewed in a two-dimensional cross-section along one of the axes of the recording medium a plurality of equally spaced steps of fine-sized periodicity superimposed upon a plurality of deep depressions of substantially coarse-sized periodicity. The structurally modified recording medium is configured to produce in reflection single and multiple colors in a broad spectral range when illuminated by a source of light.