Proximity Sensors with Smudge Detection Capabilities

Abstract

An electronic device may be provided with a touch screen display that is controlled based on information from a proximity sensor attached underneath a display layer. The proximity sensor may have a light source that emits infrared light and a light detector that detects reflected infrared light. When the electronic device is in the vicinity of a user's head, the proximity sensor may produce data indicative of the presence of the user's head. Variations in proximity sensor output due to smudges on the proximity sensor can be detected by providing the proximity sensor with an additional light source. The additional light source may be used to inject light into the display layer. The injected light may be guided within the display layer by total internal reflection. In the presence of smudge, the internally reflecting light may deviate from its normal propagation path.

Dependencies are inferred from the claim text.