A Study of Optical Tag Detection Using Rolling Shutter Based Visible Light Communications

In this paper, we present an in-depth study of light emitting diode (LED) based indoor visible light communication positioning system using a smart phone camera with rolling shutter effect, aiming for smart and connected hospital applications. The LED transmits periodical signals with different frequencies as its optical tags. The camera exploits the rolling shutter effect to detect the fundamental frequency of optical signals. The roles of camera parameters determining the rolling effect are studied and a technique to measure the camera readout time per column is presented. Factors limiting the detectable optical frequency range is explained based on the discussion of rolling shutter mechanism. The Fourier spectrum based frequency resolution, which determines the tracking capacity, is analyzed.