Method and apparatus for illumination and communication
View Patent ↗The present invention provides a method and apparatus of using light-emitting elements for illumination as well as communication of data, wherein potential flicker due to sub-fusion frequency data correlations can be reduced compared to prior art techniques, while reducing redundancy in the data transmission. The intensity of the illumination from the light-emitting elements is controlled by a dimming signal such as a pulse width modulation (PWM) signal or a pulse code modulation (PCM) signal, for example. An amplitude-modulated data signal is then superimposed on the dimming signal for communication of data. The dimming signal thus acts as a carrier signal for the data signal. A sensing means is then used to receive the data signal by detecting all or part of the illumination from the light-emitting elements. The data signal can subsequently be extracted from the detected illumination.
1. An apparatus comprising:
a) a plurality of light-emitting elements configured to emit a variable intensity visible light for both general illumination and a communication of data;
b) a control means for generating a continuous carrier signal for controlling a luminous flux output of the plurality of light-emitting elements, the carrier signal comprising a plurality of phase-shifted dimming signals for the plurality of light-emitting elements, respectively, each of the plurality of dimming signals having a duty cycle for operation of an associated light-emitting element included in the plurality of light emitting elements;
c) a modulation means for generating a data signal including encoded data for superposition on the carrier signal thereby forming a control signal for further controlling the luminous flux output of the plurality of light emitting elements in a manner that does not result in a visible flicker, the control signal formed by employing a peak amplitude modulation of substantially less than 100%, wherein the control signal is formed with the encoded data unconstrained by a minimum duty cycle of at least one of the plurality of dimming signals;
d) a sensing means for detecting at least a portion of the luminous flux output; and
e) means for extracting the data signal from the detected luminous flux output.
2. The apparatus according to claim 1 wherein the carrier signal is a pulse width modulated or a pulse code modulated signal.
3. The apparatus according to claim 1 , wherein the data signal is a peak amplitude modulated signal.
4. The apparatus according to claim 3 wherein the encoded data is encoded in a manner that is less than fully redundant.
5. The apparatus according to claim 1 wherein the continuous carrier signal is amplitude modulated by the data signal.
6. The apparatus according to claim 1 wherein the sensing means comprises an optical filter.
7. The apparatus according to claim 1 wherein the control signal is formed by employing a peak amplitude modulation of less than about one percent.
8. A method for providing visible light for both general illumination and a communication of data, the method comprising the steps of:
a) generating a continuous carrier signal for controlling a luminous flux output of a plurality of light-emitting elements, the carrier signal comprising a plurality of phase-shifted dimming signals for the plurality of light emitting elements, respectively, each of the plurality of dimming signals having a duty cycle for operation of an associated light-emitting element included in the plurality of light emitting elements;
b) generating a data signal including encoded data;
c) combining the carrier signal and the data signal thereby forming a control signal by employing a peak amplitude modulation of substantially less than 100%, the control signal for further controlling the luminous flux output of the plurality of light emitting elements in a manner that does not result in a visible flicker and forming the control signal with the encoded data unconstrained by a minimum duty cycle of at least one of the plurality of dimming signals;
d) sensing at least a portion of the luminous flux output; and
e) extracting the data signal from the sensed luminous flux output.
9. The method according to claim 8 wherein the carrier signal is a pulse width modulated or a pulse code modulated signal.
10. The method according to claim 9 , wherein the data signal is a peak amplitude modulated signal.
11. The method according to claim 10 wherein the continuous carrier signal is amplitude modulated by the data signal.
12. The method according to claim 10 wherein the control signal is encoded.
13. The method according to claim 9 further including a step of filtering at least a portion of the luminous flux output with an optical filter, prior to the step of sensing at least a portion of the luminous flux output.
14. The method according to claim 8 wherein the step of combining includes a step of employing a peak amplitude modulation of less than about one percent.