Wireless Indoor Optical Positioning With a Differential Photosensor

An indoor optical positioning technique using a differential photosensor device is presented. The method is based on angle of arrival information estimated by the differential photosensor in an indoor environment with fixed optical beacons. A photocurrent is generated by each of the three photodiodes in the photosensor by incident light from the optical beacons. The amplitudes of these photocurrents are a function of the incident angle of the light. Previously derived equations that express photocurrent amplitudes as a function of the azimuthal arrival angle, φ, and the polar arrival angle, θ, are modeled with second- and third-order polynomials, respectively, to determine the φ and θ angles from measured photocurrents. Testing with optical beacons in various positions with respect to a fixed photosensor resulted in a root mean squared error for all estimated angles φ and θ of 2.8°. A positioning accuracy of better than 4 cm is achieved.