[tsac]

More info on the sensors

Mobile phones use IR-based proximity sensors to detect the presence of a human ear. This sensing is done for two purposes: Reduce display power consumption by turning off the LCD backlight and to disable the touch screen to avoid inadvertent touches by the cheek. IR sensors have a number of disadvantages, including high power consumption, high cost, blind zones, and accumulation of dirt, as well as unreliable performance over temperature, hair, and skin color variations. Recent advances in capacitive proximity sensing technology address these designs disadvantages and could potentially replace every IR sensor in the mobile phone market.