Optical security device

1 . An optical security device comprising a recorded or encoded representation of an optically variable image, the image being reconstructable and viewable for security, authentication or identification purposes, the device comprising:

an optical structure in which there is recorded or encoded a representation of the optically variable image in a form of a plurality of portions of a complete said image to be reconstructed,

wherein respective ones of said plurality of portions of the optically variable image can, when reconstructed, only be viewed in their totality by viewing said complete image (i) at or over a plurality of different viewing angles or angle ranges relative to the optical structure, or (ii) at or over a plurality of different angles or ranges of angles of illumination of the optical structure, or both (i) and (ii), and

wherein a size, in at least one dimension, direction, axis or plane, of a complete reconstructed image is greater than the corresponding size, in same, or respective same, dimension, direction, axis or plane, of a part of the optical structure having said plurality of portions of the image collectively recorded or encoded therein.

2 . The optical security device according to claim 1 , wherein the optical structure has recorded or encoded therein a representation of the optically variable image in the form of a plurality of portions of the complete image to be reconstructed,

wherein each respective one of some or all of said plurality of portions of the optically variable image can, when reconstructed, only be viewed in full by viewing a respective image portion (iii) at or over a respective range of viewing angles relative to the optical structure, or (iv) at or over a range of angles of illumination of the optical structure, or both (iii) and (iv).

3 . The optical security device according to claim 2 , wherein either:

(a) each respective one of some or all of said plurality of portions of the optically variable image can, when reconstructed, only be viewed in full by viewing said respective image portion (iii) at or over the respective range of viewing angles relative to the optical structure and at a respective given angle of illumination of the optical structure; or

(b) each respective one of some or all of said plurality of portions of the optically variable image can, when reconstructed, only be viewed in full by viewing said respective image portion at a respective given viewing angle and (iv) at or over the respective range of angles of illumination of the optical structure.

4 . The optical security device according to claim 2 , wherein either:

(i) the respective viewing angle/angle range or angle/angle range of illumination or both thereof at or over which a or any given one of the image portions can be viewed, when reconstructed, is/are substantially the same viewing angle/angle range or angle/angle range of illumination or both thereof at or over which at least one other of said image portions, but not all of those other said image portions, or at least some of but not all of the remaining reconstructed image portions, is/are viewable when reconstructed; or

(ii) the respective viewing angle/angle range or angle/angle range of illumination or both thereof at or over which a or any given one of the image portions can be viewed, when reconstructed, is/are substantially different from the respective viewing angle(s)/angle range(s) or angle(s)/angle range(s) of illumination or both thereof at or over which at least one other of the reconstructed image portions, or at least some of the remaining reconstructed image portions, is/are viewable;

whereby, in each case (i) or (ii), in order for the complete reconstructed image to be viewable in its totality, such that all the portions of the complete reconstructed image are each respectively reconstructable and viewable, it is necessary for at least two different viewing angles/angle ranges or angles/angle ranges of illumination or both thereof to be employed to view all the reconstructed image portions.

5 . The optical security device according to claim 2 , wherein the respective viewing angle/angle range or angle/angle range of illumination or both thereof at or over which a or any given one of the image portions can be viewed, when reconstructed, is/are substantially different from the respective viewing angles/angle ranges or angles/angle ranges of illumination or both thereof at or over which substantially all the other reconstructed image portions are viewable;

whereby in order for the complete reconstructed image to be viewable in its totality, such that all the portions of the complete reconstructed image are each respectively reconstructable and viewable, it is necessary for a plurality of different viewing angles/angle ranges or angles/angle ranges of illumination or both thereof to be employed to view respective ones of the plurality of reconstructed image portions;

wherein each respective viewing angle/angle range or angle/angle range of illumination or both thereof at or over which a respective reconstructed image portion is viewable is unique to that respective reconstructed image portion.

6 . The optical security device according to claim 1 , wherein the optical structure has recorded or encoded therein a representation of the optically variable image in the form of a plurality of discrete portions of the complete image to be reconstructed,

wherein each respective one of said plurality of discrete portions of the optically variable image can, when reconstructed, only be viewed by viewing the respective said discrete image portion (v) at or over a respective viewing angle or angle range relative to the optical structure, or (vi) at or over a respective angle or angle range of illumination of the optical structure, or both (v) and (vi), which is/are different from the viewing angle/angle range or angle/angle range of illumination or both thereof at or over which at least one other of said discrete image portions is viewable when reconstructed.

7 . The optical security device according to claim 1 , wherein either:

(i) the size, in at least one dimension, direction, axis or plane, of one or more given ones of the viewable portions of the reconstructed image is greater than the corresponding size, in the same, or the respective same, dimension, direction, axis or plane, of a part of the optical structure having said one or more given optically variable image portion(s) recorded or encoded therein; or

(ii) the size, in at least one dimension, direction, axis or plane, of a given part of the optical structure having one or more given ones of the optically variable image portion(s) recorded or encoded therein is smaller than the corresponding size, in the same, or the respective same, dimension, direction, axis or plane, of said one or more respective viewable portion(s) of the reconstructed image;

wherein the size differential of the respective reconstructed image portion relative to the respective recorded or encoded image portion of the structure is such that the respective reconstructed image portion is any of: >1 times, or ≥2 times, or ≥3 times, or ≥4 times, or ≥5 times, or ≥6 times, or ≥7 times, or ≥8 times, or ≥9 times, or ≥10 times, or ≥12 times or ≥13 times or ≥15 times or ≥18 times or ≥20 times, the size of the respective recorded image portion of the structure, wherein any of said ranges include fractions as well as whole number multiples.

8 . The optical security device according to claim 1 , wherein an angular size of the reconstructed image is >1 times, or ≥2 or ≥3 times, or ≥10 times, or ≥20 times the angular size of the optical structure when viewed from a given viewing distance or location therefrom, wherein any of said ranges include fractional multiples as well as whole number multiples.

9 . The optical security device according to claim 1 , wherein the recorded or encoded representation of the optically variable image is a hologram.

10 . The optical security device according to claim 1 , wherein either:

(i) the recorded or encoded representation of the optically variable image is a two-dimensional (2-D) or a three-dimensional (3-D) hologram, and the optically variable image is an image of one or more 2-D or 3-D objects, pictures, patterns, one or more alphanumeric or other typographical characters, or any combination of any two or more of any of the foregoing things; or

(ii) the optical structure having the portion(s) of the optically variable image recorded or encoded therein is or comprises a DOVID (diffractive optically variable image device).

11 . The optical security device according to claim 1 , wherein the optical structure defines a structure plane or a plane which is contained within a thickness of the optical structure or a plane which is non-parallel to light incident on the optical structure during the reconstruction of the recorded or encoded image, and the reconstructed image lies either (a) wholly or at least partially to one side of, or to each of both sides of, said structure plane, or (b) out of the structure plane on a side thereof opposite to that from which illuminating light is incident thereon.

12 . The optical security device according to claim 1 , wherein either:

(i) the device takes the form of a security feature which has already been applied to or incorporated into a structure of an item or object whose security, authentication or identification is required; or

(ii) the device is provided in the form of a discrete security device or security element for application, affixation or incorporation into the structure of the item or object whose security, authentication or identification is required.

13 . The optical security device according to claim 1 , wherein the optical structure in which is recorded or encoded the representation of the optically variable image is, or is contained within or on, a body of optically active material,

wherein the body of optically active material comprises a sheet or plate or film or layer of the optically active material with a thickness range of from 0.1 or 0.5 or 1 or 5 or 10 up to 100 or 200 or 300 or 400 or 500 or 800 or 1000 μm.

14 . The optical security device according to claim 13 , wherein a portion of the body of optically active material in which is recorded or encoded the representation of the optically variable image further comprises one or more additional or auxiliary overt or covert security features formed by modulations of the surface, volume or internal optical properties of said body portion and comprising one or more graphics, holograms, micro- or nano-graphics, diffractive or non-diffractive images and structures, or hidden images.

15 . A method for the production of an optical security device according to claim 1 , the method comprising:

recording or encoding in an optical structure a recorded or encoded representation of the optically variable image in the form of a plurality of portions of the complete image to be reconstructed,

wherein the respective said plurality of portions of the optically variable image can, when reconstructed, only be viewed in their totality by viewing said image (i) at or over a plurality of different viewing angles or angle ranges relative to the optical structure, or (ii) at or over a plurality of different angles or ranges of angles of illumination of the optical structure, or both (i) and (ii), and

wherein the size, in at least one dimension, direction, axis or plane, of the complete image, when reconstructed, is greater than the corresponding size, in the same, or the respective same, dimension, direction, axis or plane, of a part of the optical structure having said plurality of portions of the image collectively recorded or encoded therein;

wherein either:

(i) wherein the method comprises forming the optical structure, having said plurality of portions of the record or encoded representation of the complete optically variable image recorded or encoded therein, as an optical security feature, and either simultaneously or subsequently to that recording or encoding incorporating said optical security feature into an item or object whose security, authentication or identification is required; or

(ii) wherein the method comprises forming the optical structure, having said plurality of portions of the record or encoded representation of the complete optically variable image recorded or encoded therein, as a discrete optical security device or security element, and the method further comprises a step of applying, affixing or incorporating the optical security device or element onto or into the optical structure of the item or object whose security, authentication or identification is required.

16 . A method of authenticating or identifying an item or object having applied or affixed thereto or incorporated into the structure thereof an optical security device according to claim 1 , the method comprising:

(a) reconstructing said plurality of portions of the complete optically variable image recorded or encoded in the optical structure of the device; and

(b) viewing one or more of said plurality of reconstructed portions of the complete image.

17 . The method according to claim 16 , wherein the optical security device is an optical security device in which:

the optical structure has recorded or encoded therein a representation of the optically variable image in the form of a plurality of discrete portions of the complete image to be reconstructed, and:

(i) each respective one of said plurality of discrete portions of the optically variable image can, when reconstructed, only be viewed by viewing the respective said discrete image portion (v) at or over a respective viewing angle or angle range relative to the optical structure, or (vi) at or over a respective angle or angle range of illumination of the optical structure, or both (v) and (vi), which is/are different from the viewing angle/angle range or angle/angle range of illumination or both thereof at or over which at least one other of said discrete image portions is viewable when reconstructed; or

(ii) a respective viewing angle/angle range or angle/angle range of illumination, or both thereof, at or over which a or any given one of the discrete image portions can be viewed, when reconstructed, is/are substantially the same viewing angle/angle range or angle/angle range of illumination or both thereof at or over which at least one other of said discrete image portions, but not all of those other said discrete image portions, or at least some of but not all of the remaining reconstructed discrete image portions, is/are viewable when reconstructed; or

(iii) a respective viewing angle/angle range or angle/angle range of illumination, or both thereof, at or over which a or any given one of the discrete image portions can be viewed, when reconstructed, is/are substantially different from the respective viewing angle(s)/angle range(s) or angle(s)/angle range(s) of illumination or both thereof at or over which at least one other of the of the reconstructed discrete image portions, or at least some of the remaining reconstructed discrete image portions, is/are viewable;

wherein the viewing step (b) comprises:

(bi) viewing the or each respective one of the plurality of reconstructed discrete portions of the complete optically variable image at or over, or only at or over, the respective viewing angle or angle range relative to the optical structure, or by illuminating the optical structure at or over the respective angle or angle range of illumination, or both thereof that is associated with that respective reconstructed discrete image portion of the complete image; or

(bii) viewing respective ones of the plurality of reconstructed discrete portions of the complete optically variable image at or over, or only at or over, respective ones of the plurality of different viewing angles/angle ranges or angles/angle ranges of illumination of the optical structure or both thereof; or

(biii) both (bi) and (bii);

whereby the complete reconstructed optically variable image is viewable in its totality, such that all the discrete portions of the complete reconstructed image are each respectively reconstructable and viewable, by, or only by:

(ci) viewing the or each respective discrete portion thereof at or over, or only at or over, the respective viewing angle/angle range or angle/angle range of illumination of the optical structure or both thereof that is/are associated with that respective discrete image portion, or

(cii) viewing respective ones of the plurality of reconstructed discrete portions thereof at or over, or only at or over, the respective ones of the plurality of different viewing angles/angle ranges or angles/angle ranges of illumination of the optical structure or both thereof, or

(ciii) both (ci) and (cii) where each of (bi), (bii) and (biii) corresponds respectively to each of (ci), (cii) and (ciii).

18 . The method according to claim 16 , wherein the recorded or encoded optically variable image, or the respective portions thereof, is/are reconstructed by illumination of the optical structure, or a respective part or portion or region thereof, by electromagnetic radiation, the electromagnetic radiation being of a wavelength/frequency appropriate to the means used to record/encode or intended for reconstructing the image,

wherein the electromagnetic radiation comprises visible light.

19 . The method according to claim 16 , wherein one of the following (i), (ii) or (iii) is present or satisfied:

(i) the viewing step (b) is carried out by:

(ia) visual viewing of at least a or a respective portion of the image by one or more eyes of a human observer, or

(ib) detecting at least a or a respective portion of the image using an optically sensitive device, in combination with image processing hardware or software; or

(ii) the viewing step (b) comprises:

viewing a first one of the plurality of portions of the reconstructed image by means of a first viewing step or operation in which just the first portion only of the reconstructed image is viewed; and

one or more additional or further viewing steps or operations in each of which a respective additional or further one of the plurality of portions of the reconstructed image is viewed;

wherein in each of said viewing steps or operations the viewing of each respective portion of the reconstructed image is carried out by (ci) viewing each respective portion of the image at or over a given, or at or over a unique, viewing angle or angle range relative to the optical structure, or (cii) illuminating the optical structure at or over a given, or at or over a unique, angle or angle range of illumination, or both (ci) and (cii), that is/are associated with that respective image portion; or

(iii) both of the above (i) and (ii) are present or satisfied.

20 . The method according to claim 16 , wherein the overall complete reconstructed image is of a size, greater than that of the parts of the optical structure in which are recorded or encoded the various portions of the image, such that it is only viewable in its entirety upon a plurality of individual or discrete viewing steps or operations being carried out, each such viewing step or operation being so as to view a respective portion only, or a respective discrete portion only, of the complete reconstructed image, or a respective discrete portion only of the complete reconstructed image independently of the viewing of any of the other portion(s) of the complete reconstructed image.

21 . The method according to claim 16 , wherein:

plural portions of the complete reconstructed image are viewable independently of each other, and

wherein the viewing of the complete reconstructed image is accomplished by illuminating corresponding respective portions of the recorded or encoded image in a plurality of discrete illumination steps or operations, wherein the viewing of the complete reconstructed image is accomplished by illuminating the recorded or encoded image sequentially in a series of discrete viewing steps or operations, each at or over a respective selected one of a plurality of different angles of incidence or ranges of angles of incidence of the incoming light, such that each respective incident angle or angle range corresponds to and enables the viewing of a respective portion of the reconstructed image at or over a respective different viewing angle or a respective different angle range relative to the optical structure.