The sensor, its orientation and position is fully tracked in 3D.The opticaltracking system is based on monitoring a defined measurement space using astereo camera. Each camera is equipped with an infrared (IR) pass filter in frontof the lens, and a ring of IR LEDs around the lens to periodically illuminate themeasurement space with IR light. This light is not visible to the human eye andits intensity is completely safe for human beings to work with. The sensor isequipped spherical marker, with embedded retro-reflective markers, whichreflect the incoming IR light. The IR light reflections are detected by the stereocamera, and the tracking system translates them to exact 3D coordinates alongwith the sensor orientation.