System and method using a gated retro-reflector for visible light uplink communication

Patent metadata

Field	Value
Publication number	US-10027410-B2
Application number	US-201615190644-A
Country	US
Kind code	B2
Filing date	Jun 23, 2016
Priority date	Jun 23, 2016
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

Abstract

A device uses gated retro-reflectors to transmit uplink data in a visible light communication (VLC) system. The gated retro-reflector includes a retro-reflector and a gating shutter between the retro-reflector and a VLC light source. A light sensor receives VLC data at regular intervals in which a light pulse received during one of the intervals represents a first downloaded symbol and absence of a light pulse during another one of the intervals represents a second downloaded symbol. A controller controls the gating shutter to send uplink data from the device responsive to each received VLC light pulse. The controller opens the gating shutter during the reception of a VLC light pulse to upload a first uploaded symbol and closes the gating shutter during the reception of a VLC light pulse to upload a second uploaded symbol.

First claim

What is claimed is:

1. A device, comprising:
a retro-reflector having a front face configured to retro-reflect incident light back toward a modulated light source;
a gating shutter coupled between the retro-reflector and the modulated light source the gating shutter being configured to be in open and closed states in response to a control signal, wherein the gating shutter permits passage of light to and from the retro-reflector in the open state and reduces the passage alight in the closed state;
a light sensor configured to receive and detect light including visible light communication (VLC) data from the modulated light source, the VLC data being received during VLC intervals in which a first VLC light pulse received during a first one of the VLC intervals represents at least a portion of a first VLC data symbol and presence of a second VLC light pulse during a second one of the VLC intervals represents at least a portion of a second VLC data symbol; and
a controller coupled to the light sensor and to the gating shutter, the controller controlling the gating shutter to be in the open state during the reception of the first light pulse to upload a first symbol and to be in the closed state during the reception of the second light pulse to upload a second symbol.

2. The device of claim 1 , wherein:
the controller synchronizes the opening and closing of the gated shutter to the VLC intervals and the controller controls the gating shutter to be in the open or closed states at times substantially coincident with respective ones of the VLC intervals in which the VLC light pulses are received.

3. The device of claim 1 , wherein the retro-reflector is selected from a group consisting of a spherical-lens retro-reflector and a cube-corner retro-reflector.

4. The device of claim 1 , wherein the retro-reflector includes a material having a first index of refraction embedded in the gating shutter, the gating shutter including a material having a variable index of refraction that changes from the first index of refraction to a second index of refraction in response to the control signal.

5. The device of claim 4 , wherein:
the retro-reflector material having the first index of refraction is a polymer material;
the material having the variable index of refraction is a liquid crystal material; and
the gating shutter comprises first and second transparent electrodes responsive to the control signal to selectively subject the liquid crystal material to an electric field to cause the liquid crystal material to switch between the first and second indexes of refraction.

6. The device of claim 1 , wherein the gating shutter is a liquid crystal device configured between the front face of the retro-reflector and the modulated light source and the control signal causes the liquid crystal device to selectively allow and block the retro-reflector from receiving and retro-reflecting light from the modulated light source.

7. The device of claim 1 , wherein:
the gating shutter includes a material selected from a group consisting of a saturable absorber and a reverse saturable absorber;
the gating shutter is configured between the front face of the retro-reflector and the modulated light source; and
the control signal selectively applies light energy to the gating shutter material to cause the gating shutter material to selectively allow or block transmission of light from the modulated light source to and from the retro-reflector.

8. The device of claim 1 , wherein:
the gating shutter includes a photonic crystal configured between the front face of the retro-reflector and the modulated light source and the control signal causes the photonic crystal to selectively expand or contract to cause the photonic crystal to switch between transmitting and blocking light in a predetermined wavelength band.

9. The device of claim 8 , wherein:
the photonic crystal includes a piezoelectric material and first and second electrodes on respective first and second sides of the piezoelectric material, both the piezoelectric material and the first and second electrodes being transparent to light in the predetermined wavelength band; and
the control signal selectively applies first and second electric charges across the first and second electrodes to cause the piezoelectric material to respectively expand and contract.

10. The device of claim 8 , wherein:
the photonic crystal includes a temperature-sensitive material and a heating element, both the temperature-sensitive material and the heating element being transparent to light in the predetermined wavelength band; and
the control signal causes the heating element to selectively apply and not apply heat to the heat sensitive material to cause the heat sensitive material to respectively expand and contract.

11. The device of claim 1 , wherein the light sensor includes a camera.

12. The device of claim 1 , wherein the light sensor includes at least one sensor selected from a group consisting of a photodiode, a phototransistor, a photoresistor and a photomultiplier.

13. A portable device comprising:
a housing having a first surface and a second surface;
a first retro-reflector mounted on the first surface of the housing such that a retro-reflecting front face of the first retro-reflector points away from the first surface;
a second retro-reflector mounted on the second surface of the such that a retro-reflecting front face of the second retro-reflector points away from the second surface;
a first gating shutter mounted on top of the front face of the first retro-reflector and a second gating shutter mounted on top of the front face of the second retro-reflector, wherein the first and second gating shutters are controlled by respective first and second control signals, to be in open and closed states, wherein each of the first and second the gating shutters permits passage of light to and from the retro-reflector in the open state and reduces the passage of light in the closed state;
a light sensor configured to receive and detect light including visible light communication (VLC) data from a modulated light source, the VLC data being received at regular intervals in which a first VLC light pulse received during a first one of the intervals represents at least a portion of a first VLC data symbol and presence of a second VLC light pulse during a second one of the intervals represents at least a portion of a second VLC data symbol; and
a controller coupled to the light sensor and to the first and second gating shutters, the controller controlling at least one of the first and second gating shutters to be in the open state during the reception of the first light pulse to upload a first symbol and for controlling at least one of the first and second gating shutters to be in the closed state during the reception of the second light pulse to upload a second symbol.

14. The portable device of claim 13 , wherein the first and second gating shutters are connected in parallel and the controller configures both of the first and second gating shutters to be in the open state bring the reception of the first VLC light pulse and controls both of the first and second gating shutters to be in the closed state during the reception of the second VLC light pulse.

15. The portable device of claim 13 , wherein:
the light sensor is mounted on the first surface of the housing;
the portable device further comprises a further light sensor mounted on the second surface of the housing, the further light sensor being configured to receive the VLC data symbols; and
the controller is coupled to the light sensors mounted

Assignees

• ABL IP Holdiing LLC
• Abl Ip Holding Llc

Inventors

• Rains Jack C
• Ramer David P

Classifications

• H04N23/65

  Control of camera operation in relation to power supply · CPC title

• H04N23/54

  Mounting of pick-up tubes, electronic image sensors, deviation or focusing coils · CPC title

• H04N23/55

  Optical parts specially adapted for electronic image sensors; Mounting thereof · CPC title

• H04W52/0229

  where the received signal is a wanted signal · CPC title

• H04B10/116 Primary

  Visible light communication · CPC title