Multiple image encoding using surface relief structures as authenticating device for sheet-material authenticated item

• US 4,417,784 A
• Filed: 02/19/1981
• Issued: 11/29/1983
• Est. Priority Date: 02/19/1981
• Status: Expired due to Fees

• Current Assignee: RCA Corporation
• Original Assignee: RCA Corporation
• Inventors: Gale, Michael T., Knop, Karl H.
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): Propp, William
• Application Number:
  US06/236,111
• Time in Patent Office: 1,013 Days
• Field of Search: 283/91, 283/902, 350/162.11, 350/162.17, 350/162.19, 350/162.23, 427/7, 428/915, 428/916
• US Class Current: 359/568
• CPC Class Codes: G02B 3/0031 Replication or moulding, e.g. hot embossing, UV-casting, injection moulding
• CPC Class Codes: G02B 3/005 arranged along a single direction only, e.g. lenticular sheets G02B3/0043 takes precedence
• CPC Class Codes: G06K 19/16 the marking being a hologram or diffraction grating
• CPC Class Codes: G07F 7/086 by passive credit-cards adapted therefor, e.g. constructive particularities to avoid counterfeiting, e.g. by inclusion of a physical or chemical security-layer for security documents G07D7/00; for the reading of record-carriers in general G06K7/00; for the design of coded credit-cards G06K19/10
• CPC Class Codes: G09F 3/00 Labels, tag tickets, or similar identification or indication means medals or badges A44C3/00; making labels B31D1/02; sheets temporarily attached together B42F; labelling B65C; labels on record carriers G11B23/38, G11B23/40; Seals; Postage or like stamps
• CPC Class Codes: Y10S 428/916 Fraud or tamper detecting

Abstract

An authenticating device comprises a transparent material, such as a plastic, having a thickness no greater than 100 micrometers embossed on one side with a lenticular array of lenslets having focal lengths substantially equal to this thickness, and embossed on the other side with a reflective relief pattern forming a periodic structure periods smaller than 100 micrometers, which periods are of a width that at least approximates that of the lenslets. The reflective relief structure of the authenticating device is secured to a viewable surface of the authenticated item sheet material and each period of the relief structure is comprised of a set of juxtaposed elements having significantly different reflective characteristics from one another.

Claims

1. In an article comprised of an authenticated item of sheet material which is subject to counterfeiting and an authenticating device bonded to said item, wherein said device includes a transparent material bonded to said sheet material, said material having a reflective periodic structure formed as a relief pattern on a viewable surface of said material which is proximate to said sheet material, said transparent material exhibiting a given index-of-refraction and being attached to said sheet material in a manner sufficiently secure to prevent said transparent material from being removed from said sheet material without effectively destroying said structure;

the improvement in said device;

wherein the period of said periodic structure is smaller in size than 100 micrometers and each period is comprised of substantially the same given set of a plural number of juxtaposed elements, respective elements of said given set having significantly different reflective characteristics from one another, and

wherein said transparent material has a given thickness no greater than 100 micrometers and has a periodic lenticular array embossed on a surface thereof which is distal to and is oriented substantially parallel to said periodic structure, each period of said array being comprised of a lens having an aperture width that at least approximates that of a period of said structure and having a focal length substantially equal to said given thickness.

2. The article defined in claim 1,

wherein said juxtaposed elements of said given set are comprised of substantially parallel stripes, and wherein said lenticular array is comprised of cylindrical lenses having axes oriented substantially parallel to said parallel stripes.

3. The article defined in claim 1,

wherein each period of said structure is between 10 and 50 micrometers, and

wherein said given thickness is between 10 and 50 micrometers.

4. The article defined in claim 1,

wherein said aperture width of each lens of said array is substantially equal to the width of a period of said structure.

5. The article defined in claim 1, wherein said aperture width of each lens of said array differs from but still approximate the width of a period of said structure.

6. The article defined in claim 5, wherein at least one given element of said set for each of said periods is comprised of a rectangular profile diffraction grating of a given optical amplitude which operates as a diffractive-subtractive filter for reflecting a zero diffraction order of a given color hue in response to illumination thereof with polychromatic light.

7. The article defined in claim 1, wherein said elements of said given set are comprised of separate diffractive-subtractive filters that exhibit zero diffraction order transfer functions in which adajacent filters are different from one another.

8. The article defined in claim 7, wherein at least one given element of said set for any one said periods is comprised of a sinusoidal profile of a given optical amplitude which operates as a diffractive-subtractive filter for reflecting a zero diffraction order of a given relative luminance in response to illumination thereof with polychromatic light.

9. The article defined in claim 8, wherein the value of said given optical amplitude is such as to substantially minimize the relative luminance of said reflected zero diffraction order.

10. The article defined in claim 8, wherein said given optical amplitude of said sinusoidal grating of said one given element is spatially modulated between successive periods of said structure in accordance with picture information.

11. The article defined in claim 1, wherein said elements of said given set are comprised of separate plane reflectors that have significantly different slopes from one another with respect to the plane of said viewable surface of said substrate.

12. The article defined in claim 11, wherein said elements of said given set exhibit respective reflectivities that are significantly different from one another.

13. The article defined in claim 1, wherein said elements of said given set are comprised have significantly different textures from one another.

14. The article defined in claim 1, wherein the reflective characteristics of the same respective elements of each of said given sets of successive periods of said structure, taken as a group, are spatially modulated in accordance with picture information.