Integrated retroreflective electronic display

• US 5,621,571 A
• Filed: 02/14/1994
• Issued: 04/15/1997
• Est. Priority Date: 02/14/1994
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Bradshaw, Thomas I., Mohn, Stephen W., Ring, Edmund J., Bantli, Heinrich
• Primary Examiner(s): Phan, James
• Application Number:
  US08/196,294
• Time in Patent Office: 1,156 Days
• Field of Search: 340/907, 340/928, 343/700 MS, 343/711, 343/713, 343/767, 343/755, 359/515, 359/529-533, 359/534-536
• US Class Current: 359/529
• CPC Class Codes: B60R 13/10 Registration, licensing, or like devices
• CPC Class Codes: G02B 5/128 transparent spheres being embedded in matrix
• CPC Class Codes: G06K 19/07703 the interface being visual
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/08 using markings of different kinds or more than one marking of the same kind in the same record carrier, e.g. one marking being sensed by optical and the other by magnetic means
• CPC Class Codes: G06K 2019/0629 Holographic, diffractive or retroreflective recording
• CPC Class Codes: G08G 1/017 identifying vehicles G08G1/015, G08G1/054 take precedence

Abstract

An integrated retroreflective data communication display for visual and electromagnetic communication is described. The display may be configured as an integrated retroreflective electronic license plate, with printed visual information, similar to the information printed on traditional license plates, on retroreflective sheeting. An antenna network is integrated within the license plate for electromagnetic communication and may be connected to external electronic modules. The display may also be configured as an integrated retroreflective electronic road sign, also providing visual and electromagnetic information in a unitary structure.

Claims

1. A retroreflective apparatus for both visual and electromagnetic data communication, said apparatus comprising:

retroreflective means for retroreflecting incident light, said retroreflecting means having visual information thereon;

antenna means for electromagnetic communication; and

coupling means for allowing coupling to said antenna means;

wherein said retroreflective apparatus is substantially rigid.

2. The retroreflective apparatus for both visual and electromagnetic data communication according to claim 1, wherein said retroreflective means comprises retroreflective sheeting having first and second faces and wherein said antenna means comprises:

a generally planar dielectric substrate having first and second faces, said first face of said dielectric substrate being disposed in parallel and adjacent said second face of said retroreflective sheeting;

radiating means disposed between said second face of said retroreflective sheeting and said first face of said dielectric substrate for radiating electromagnetic energy; and

a generally planar electrically conductive member having a first face and a second face for acting as a ground plane for said radiating means, said first face of said electrically conductive member being disposed in parallel and adjacent said second face of said dielectric substrate.

3. The retroreflective apparatus for both visual and electromagnetic data communication according to claim 2, wherein said retroreflective sheeting comprises:

a base sheet having a monolayer of microspheres which are partially embedded in one of its surfaces, said base sheet having specular light reflecting means underlying and in optical connection with the embedded surface of said microspheres;

a cover sheet disposed in spaced relation from said layer of retroreflective elements; and

a network of narrow intersecting bonds extending between said cover sheet and said base sheet.

4. The retroreflective apparatus for both visual and electromagnetic data communication according to claim 3, wherein said specular light reflecting means comprises a substantially hemispherical reflective coating on each microsphere.

5. The retroreflective apparatus for both visual and electromagnetic data communication according to claim 4, wherein said coating is a metal.

6. The retroreflective apparatus for both visual and electromagnetic data communication according to claim 5, wherein said metal is aluminum.

7. The retroreflective apparatus for both visual and electromagnetic data communication according to claim 2, wherein said retroreflective sheeting comprises a sheet having first and second sides, said first side being substantially flat and said second side having an array of cube-corner retroreflective elements thereon.

8. The retroreflective apparatus for both visual and electromagnetic data communication according to claim 2, wherein said radiating means comprises a first microstrip patch.

9. The retroreflective apparatus for both visual and electromagnetic data communication according to claim 8, wherein said coupling means comprises:

a microstrip transmission line connected to said microstrip patch; and

a coaxial line connected to said microstrip transmission line.

10. The retroreflective apparatus for both visual and electromagnetic data communication according to claim 8, wherein said coupling means comprises:

a second generally planar dielectric substrate having first and second faces, said first face of said second generally planar dielectric substrate being disposed in parallel and adjacent said second face of said electrically conductive member;

a microstrip transmission line having first and second faces, said first face of said transmission line being disposed in parallel and adjacent said second face of said second generally planar dielectric substrate and aligned with said microstrip patch; and

a coaxial line connected to said microstrip transmission line and said electrically conductive member; and

said electrically conductive member having an aperture from said first face to said second face, said aperture aligned with said microstrip patch.

11. The retroreflective apparatus for both visual and electromagnetic data communication according to claim 10, wherein an array of microstrip patches includes said first microstrip patch and wherein said electrically conductive member has a plurality of apertures from said first face to said second face, each of said apertures aligned with a corresponding microstrip patch from said array of microstrip patches.