Optical Camera Communication for Active Marker Identification in Camera-based Positioning Systems

Outside-in camera-based localization systems determine the position of mobile objects (with markers attached to them) by observing a tracking area with multiple camera anchors. Up to now the identification of the objects in the camera images only works for close objects (with passive 3-dimensional marker constellations) or when tracking gaps or a slow identification are acceptable (with an active LED that blinks a unique identification code). We present a novel Optical Camera Communication method whose LEDs are never switched off completely to allow continuous tracking. We encode bits with variations of light intensity and show how an outside-in optical localization system can reliably identify the markers within a few frames. The identification works with a bit error ratio of 7.5 10(-5). It works for moving markers (with speeds of at least up to 4 m/s), for distant markers (with distances of at least up to 44 m), for multiple markers, and under moderate ambient infrared light.