Patent ID: 8400409

Claim:
An interface device for sensing movement of an actuator across a surface of a window in an enclosure thereof, the interface device comprising: an optical navigation sensor including: an illuminator enclosed within the enclosure to illuminate at least a portion of the actuator through the window when the portion of the actuator is positioned in contact with the surface of the window; and a detector to receive light reflected through the window from the portion of the actuator; a proximity sensor comprising a number of guard-sensors in the enclosure adjacent to the optical navigation sensor and circumscribing the window programmed to distinguish between a threshold change in capacitance induced by a finger acting as the actuator and a threshold change in capacitance induced by a hand acting as the actuator, the proximity sensor configured to disable the optical navigation sensor when the threshold change in capacitance detected by the number of guard-sensors indicates the hand acting as the actuator; and a number of additional capacitive sensors circumscribing the window and positioned between the window and the number of guard-sensors, the additional capacitive sensors configured to detect threshold changes in capacitance that are lower than threshold changes in capacitance detectable by the guard-sensors and to affirmatively enable or disable the optical navigation sensor.