Encoded LED system for optical trackers

Since introducing a hybrid vision-inertial tracker using passive fiducial markers, we have encountered several applications in which the use of encoded LEDs would be preferable to paper fiducials. This includes small-scale applications requiring higher precision, and applications where the size of the target, or the range of viewing angles, or operation in the dark is important. We present a novel technique to encode LEDs without any need for synchronization between the LEDs and cameras. By using amplitude modulation codes instead of blinking binary codes, the LED is always on, and can therefore be tracked after it has been decoded at an arbitrary or even non-periodic frame rate with no missed data.