The prototype ring extends about an inch above the finger and is relatively bulky. The researchers plan to make a second version this year that will be the size of a class ring. In all other respects, the prototype meets the design criteria. First, a light-emitting diode continuously emits light into the finger. Some of that light is reflected off the blood in the finger, and is in turn captured by another element called a photo diode.
Pulse rate is one of the vital signs the ring can currently measure.
As a result, less light is reflected to the photo diode, so a weaker signal from the photo diode corresponds to a heartbeat. The data from the photo diode are processed by a circuit in the ring that amplifies the signal. The final signal is transmitted via an antenna embedded in the ring to the receiver in the room. A home computer processes the signals to show not only the rhythm of the pulse rate, but also its shape. The researchers expect that the ring could also be adapted to read other vital signs.