Patent ID: 8436896

Claim:
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.