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Method and system for demodulating a digital pulse recognition signal in a light based positioning system using a Fourier transform

  • US 8,436,896 B2
  • Filed: 06/19/2012
  • Issued: 05/07/2013
  • Est. Priority Date: 07/26/2011
  • Status: Active Grant
First Claim
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1. A method for demodulating a modulated light signal in a light based positioning system, the method comprising:

  • receiving a modulated light signal at a device, wherein the modulated light signal transmits an arbitrary identifier of a light source;

    recording the modulated light signal using a rolling shutter image sensor to create a raw image having alternating spaced apart stripes;

    subtracting background information from the raw image to create an isolated image;

    taking a Fourier transform of an image representative of the isolated image to calculate a Fourier transformed signal; and

    determining the arbitrary identifier of the light source based on the Fourier transformed signal, wherein determining the arbitrary identifier of the light source comprises;

    applying a filter to the Fourier transformed signal to create a filtered Fourier transformed signal;

    removing a DC component of filtered Fourier Transformed signal to create a processed signal; and

    selecting a peak frequency in the processed signal as the arbitrary identifier.

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