APPARATUS FOR TRANSMITTING AND RECEIVING A SIGNAL IN A VISIBLE LIGHT COMMUNICATION SYSTEM

• US 20100209118A1
• Filed: 02/19/2009
• Published: 08/19/2010
• Est. Priority Date: 02/19/2009
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Takanaka, Tooru, TAKENE, Kouichi
• Granted Patent: US 8,165,472 B2
• Time in Patent Office: Days
• US Class Current: 398/182
• CPC Class Codes: H04B 10/1141 One-way transmission
• CPC Class Codes: H04B 10/116 Visible light communication

Abstract

Disclosed herein is a visible light communication system, in which the visible light emitted from the light-emitting element is superposed with a signal in order to accomplish communication. The system has a transmitter and a receiver. The transmitter has a modulation circuit whose the demodulating mode can be changed during the communication in accordance with the state of the visible light. The receiver receives the visible light emitted from the transmitter and has a demodulation circuit that demodulates the modulated signal received from the transmitter.

Claims

1. An apparatus for transmitting a signal in visible light communication, comprising:

a light-emitting element configured to emit visible light;

a drive signal module configured to generate modulated signals of different types from a signal to transmit, thereby to generate a drive signal from one of the modulated signals; and

a drive module configured to drive the light-emitting element in accordance with the drive signal.

2. The apparatus according to claim 1, wherein the drive signal module comprises:

a modulation module configured to modulate the signal to transmit;

an inverting/non-inverting module configured to invert or not to invert a level of a modulated signal output from the modulation module, thereby to generate a drive signal from the modulated signal; and

a switching control module configured to switch an operating mode of the inverting/non-inverting module to an inverting mode or a non-inverting mode.

3. The apparatus according to claim 2, wherein the switching control module includes a switch circuit configured to turn on and off the light-emitting element when the light-emitting element is used as an illumination device.

4. The apparatus according to claim 1, wherein the drive signal module comprises:

a modulation module configured to modulate a signal to transmit, to modulated signals of several types;

a designation module configured to designate one of the modulated signals of several types;

a selection module configured to select the designated one of the modulated signals of several types, and the drive module drives the light-emitting element in accordance with the modulated signal selected by the selection module.

5. The apparatus according to claim 4, wherein the designation module includes a switch circuit configured to switch an operating mode of the light-emitting element, causing the element to emit not light, emit light at low luminance or emit light at high luminance, while the light-emitting element is being as an illumination device.

6. The apparatus according to claim 1, wherein the drive signal module comprises:

a modulation module configured to modulate the signal to transmit; and

a timing-changing module configured to change an operation timing of the modulation module, and the drive module configured to drive the light-emitting element in accordance with a modulated signal output from the modulation module.

7. The apparatus according to claim 6, wherein the timing-changing module fixes a leading edge of the modulated signal and shifts the trailing edge of the modulated signal.

8. An apparatus for receiving a signal in visible light communication, comprises:

a light-receiving element configured to receive visible light;

a received optical-signal processing module configured to extract, as a received signal, a signal superposed on the visible light received by the light-receiving element;

a converting module configured to convert the received signal to a modulated signal of the signal to transmit; and

a demodulation module configured to demodulate the modulated signal to the signal to transmit.

9. The apparatus according to claim 8, wherein the converting module comprises:

a determination module configured to determine whether the received signal has been inverted in terms of level; and

an output module configured to convert the received signal to a modulated signal having a level inverted if the received signal has been inverted or having a level not inverted if the received signal has not been inverted.

10. The apparatus according to claim 8, wherein the demodulation module demodulates the received optical signal in a plurality of demodulating modes associated with a plurality of modulating modes, thereby generating and outputting a plurality of signals as signals that should be received;

and further comprises a selection module configured to select and output any one of the signals generated by the demodulation module.

11. The apparatus according to claim 10, wherein the selection module selects and outputs one of the received signals demodulated by the demodulation module, which includes more reception errors than permitted.

12. An apparatus for receiving a signal in visible light communication, comprising:

a light-receiving element configured to receive visible light;

a received optical-signal processing module configured to extract, as a received optical signal, a signal to transmit superposed on the visible light received by the light-receiving element; and

a demodulation module configured to demodulate the signal to transmit, in accordance with a trailing edge of the received optical signal.