Patent ID: 8749474

Claim:
A mobile computing device comprising: a display device including a plurality of pixels, the plurality of pixels including a first pixel that comprises (i) first and second electrodes, and (ii) a layer of liquid crystals positioned between the first and second electrodes; a voltage source; and a processor to: detect an object approaching the first pixel in each of a transparent mode and a non-transparent mode of the first pixel; when operating the first pixel in the transparent mode, detect the object approaching the first pixel by measuring an amount of time needed for a voltage provided across the first and second electrodes to increase to a sensor threshold voltage level associated with the transparent mode; and when operating the first pixel in the non-transparent mode: detect the object approaching the first pixel by causing a variable voltage provided across the first and second electrodes of the first pixel using the voltage source, the variable voltage having a voltage amount composed of (i) a first voltage amount corresponding to a non-transparency threshold voltage level in which the first pixel is non-transparent, wherein the non-transparency threshold voltage level is greater than the sensor threshold voltage level associated with the transparent mode, and (ii) a second voltage amount that periodically increases at a predetermined rate starting at a first time until the variable voltage reaches a sensor threshold voltage level associated with the non-transparent mode at a second time; and measure an elapsed duration of time between the first time and the second time; and determine that the elapsed duration of time is greater than a predetermined period of time.