Patent ID: 8144115

Claim:
A method of determining the approximate location of contact on a display, the display having a display surface and a plurality of pixels at defined pixel locations, each pixel location including a pixel plate capacitor, each pixel plate capacitor requiring a periodic refresh of the charge stored on the capacitor and each pixel plate capacitor configured to be selectively coupled to a stabilizing capacitor, comprising: (i) prior to refreshing the charge on a monitored pixel plate capacitor, decoupling a stabilizing capacitor from a monitored pixel plate capacitor and discharging at least the monitored pixel plate capacitor; (ii) applying a driving AC signal to the monitored pixel plate capacitor of the display, and the monitored pixel plate capacitor exhibiting a detectable capacitance; (iii) electrically monitoring an aspect of the applied AC component; (iv) performing AC analysis using the monitored AC component of the applied driving signal to determine a signal proportional to the pixel plate capacitance; (v) comparing the signal proportional to the determined pixel plate capacitance to a predetermined value; (vi) identifying the approximate location in the display of the monitored pixel having a pixel plate capacitance above the predetermined value; and (vii) subsequent to monitoring an aspect of the applied AC component, coupling the stabilizing capacitor to the monitored pixel plate capacitor and refreshing the charge on the monitored pixel plate capacitor to that necessary to display the desired intensity by applying a DC voltage to the monitored pixel.