Content delivery based on a light positioning system
Systems an methods are provided that disclose providing a positioning service for devices based on light received from one or more light sources. This light based positioning service uses light information transmitted by each light source to determine the position of the device. The positioning information can include three dimension position information in a building that can then be used to deliver services and information to a mobile device. The content delivered to a mobile device can include multimedia, text, audio, and/or pictorial information. The positioning information along with other location or positioning information can be used in providing augmented reality or location aware services. The light sources can be independent beacons that broadcast information in visible light at a rate that is undetectable by the human eye. Content can be retrieved from a server over a communications connection.
1. A method of recovering information encoded in modulated light emitted by a light source, the method comprising:
acquiring an image at least partially illuminated by light emitted by the light source, the light source emitting a light output modulated in accordance with a time-varying signal so as to vary over time, different portions of the image being acquired at different times over a time interval, whereby the acquired image comprises a pattern of distortions resulting from interaction between the time-varying light output and the time interval of acquisition; and
decoding the pattern of distortions to recover the information encoded in the modulated light.
2. The method of claim 1 , wherein the light source is driven by a pulse-width modulated signal.
3. The method of claim 1 , wherein the light source is one of a plurality of asynchronous light sources each emitting modulated light.
4. The method of claim 1 , wherein the image is acquired with an image sensor.
5. The method of claim 4 , wherein the image sensor comprises a CCD image sensor.
6. The method of claim 4 , wherein the image sensor comprises a CMOS image sensor.
7. The method of claim 4 , wherein the image sensor comprises a rolling shutter for exposing different portions of the image sensor at different times.
8. The method of claim 1 , wherein the pattern of distortions comprises alternating dark and light stripes.
9. The method of claim 8 , wherein decoding the pattern of distortions comprises measuring stripe width within the acquired image.
10. The method of claim 8 , wherein widths of stripes in the image are inversely related to a frequency of the modulated light output.
11. The method of claim 1 , wherein the light source comprises a light-emitting diode (LED).
12. The method of claim 11 , wherein the LED emits substantially white light.
13. The method of claim 1 , wherein the light output is modulated at a frequency between approximately 60 Hz and approximately 5000 Hz.
14. The method of claim 1 , wherein the information recovered from the modulated light output comprises identification information for the light source.
15. The method of claim 14 , further comprising acquiring location information based on the identification information for the light source.
16. The method of claim 15 , wherein (i) the image is acquired by a mobile device, and (ii) the location information is acquired by querying a database (a) stored on the mobile device and (b) relating location information to light source identification information.
17. The method of claim 15 , wherein (i) the image is acquired by a mobile device, and (ii) the location information is acquired by querying a database (a) stored on a server remote from the mobile device and (b) relating location information to light source identification information.
18. A device for recovering information encoded in modulated light emitted by a light source, the light source emitting a light output modulated in accordance with a time-varying signal so as to vary over time, the device comprising:
an image sensor configured to acquire an image at least partially illuminated by light emitted by the light source, different portions of the image being acquired at different times over a time interval, whereby the acquired image comprises a pattern of distortions resulting from interaction between the time-varying light output and the time interval of acquisition; and
a processor for decoding the pattern of distortions to recover the information encoded in the modulated light.
19. The device of claim 18 , wherein the image sensor comprises a CCD image sensor.
20. The device of claim 18 , wherein the image sensor comprises a CMOS image sensor.
21. The device of claim 18 , wherein the image sensor comprises a rolling shutter for exposing different portions of the image sensor at different times.
22. The device of claim 18 , wherein the pattern of distortions comprises alternating dark and light stripes.
23. The device of claim 22 , wherein the processor is configured to decode the pattern of distortions by measuring stripe width within the acquired image.
24. The device of claim 22 , wherein widths of stripes in the image are inversely related to a frequency of the modulated light output.
25. The device of claim 18 , further comprising a database relating decoded information to location information for the light source.
26. The device of claim 18 , wherein the image sensor and processor are disposed within a mobile device, wherein the mobile device comprises a communications module for communicating decoded information to a remote server.