US Patent 9223451 Active capacitive sensing on an HMD

Embodiments described herein may allow for the use of active capacitive sensing on a head-mountable device. An example method may involve: sending a first signal that has a first frequency from a signal transmitter positioned on a wearable computing device so that when the wearable computing device is worn, the signal transmitter couples to a part of a wearer of the wearable computing device, receiving a second signal at a capacitive sensor located on the wearable computing device, determining whether the second signal has the first frequency, if the second signal has the first frequency, outputting a third signal that is indicative of manual input on the capacitive sensor, and if the second signal does not have the first frequency, refraining from outputting the third signal.