Optical stylus synchronization

摘要

Active stylus operation when there is no physical connection between the stylus and the touch array requires communication and synchronization. It is possible to use the touchscreen stack-up itself to communicate synchronization signals or other information optically by outfitting the active stylus with an optical receiver and transmitting signals either with additional diodes or by modulating the display clock itself.

主权项

1. A user input device comprising:
a display; a capacitance sensor array disposed in a stackup with the display; a capacitance sensor circuit coupled to the capacitance sensor array; and an optical transmit (TX) circuit coupled to the capacitance sensor circuit, wherein the optical TX circuit is configured to receive a first signal from the capacitance sensor circuit and to transmit the first signal via light passing through the capacitance sensor array to an optical receiver included in a stylus, wherein the capacitance sensor circuit is configured to measure a capacitance using a second signal generated responsive to the first signal, and wherein the second signal is received by the capacitance sensor array.