Patent attributes
A sensor on a wearable device may be further configured as a sensor for detecting and recognizing a gesture to control the wearable device. For example, light detected by a photoplethysmography (PPG) sensor of a smart watch may include (i) light back reflected from underneath the smart watch and (ii) light back reflected from a touch to a wrist adjacent to the smart watch. The detected light may be filtered to isolate the light back reflected from the touch. A waterfall image that includes information about how the isolated light changes with time and amplitude may be generated and used to detect and recognize gestures performed on the wrist, such as a touch. This additional touch area may help to supplement a touch area provided by a display to control the smart watch.
