System and method of sensing actuation and release voltages of an interferometric modulator

Abstract

A method for sensing the actuation and/or release voltages of a electromechanical system or a microelectromechanical device include applying a test pulse to the device and sensing its state. In one embodiment, the device is part of a system comprising an array of interferometric modulators suitable for a display. The method can be used to compensate for temperature dependent changes in display pixel characteristics.

1 . A display device comprising:
 one or more electromechanical devices;   a filter resistor connected in series with each row of electromechanical devices; and   a sensing circuit for measuring the collective capacitance of each row of electromechanical devices.   
     
     
         2 . The display device of  claim 1 , further comprising a driver circuit configured to sense an output of the sensor to determine a threshold voltage for use in testing the state of one or more of the devices. 
     
     
         3 . The system of  claim 1 , wherein the one or more electromechanical devices includes one or more display elements. 
     
     
         4 . The system of  claim 2 , wherein the one or more electromechanical devices are arranged in an array to display images in response to signals from the driver circuit. 
     
     
         5 . The system of  claim 1 , wherein the sensing circuit comprises resistive and capacitive elements in parallel. 
     
     
         6 . The system of  claim 1 , wherein the sensing circuit comprises an integrator with one or more passive feedback components. 
     
     
         7 . The system of  claim 1 , further comprising a timing control circuit. 
     
     
         8 . The system of  claim 7 , wherein the timing control circuit and the sensing circuit are embodied in an integrated circuit. 
     
     
         9 . The system of  claim 7 , wherein the timing control circuit controls an activation of the one or more electromechanical devices. 
     
     
         10 . The system of  claim 1 , wherein the one or more electromechanical devices include one or more interferometric modulators. 
     
     
         11 . The system of  claim 1 , wherein the one or more electromechanical devices include a reflective surface. 
     
     
         12 . The system of  claim 1 , wherein the one or more electromechanical devices can be positioned in a reflective position and a non-reflective position. 
     
     
         13 . The system of  claim 1 , wherein the one or more electromechanical devices are movable. 
     
     
         14 . A method for sensing a state of each of a plurality of electromechanical devices arranged in a row, the method comprising;
 measuring a collective capacitance of a circuit comprising a plurality of electromechanical devices;   determining a threshold voltage for the plurality of electromechanical devices based at least in part on the measured collective capacitance;   applying a test pulse to at least one of the plurality of electromechanical devices;   measuring a capacitance dependent response of the at least one electromechanical device; and   determining a state of the at least one electromechanical device by comparing the measured capacitance dependent response of the at least one electromechanical device with the threshold voltage.   
     
     
         15 . The method of  claim 14 , further comprising determining a duration of the test pulse based on a τ value for the circuit. 
     
     
         16 . The method of  claim 14 , further comprising connecting a filter resistor in series with the plurality of electromechanical devices. 
     
     
         17 . A display device comprising:
 means for measuring a collective capacitance of a plurality of electromechanical devices;   means for determining a threshold voltage for the plurality of electromechanical devices based upon the measured collective capacitance;   means for applying a test pulse to at least one of the plurality of electromechanical devices;   means for measuring a capacitance dependent response for at least one of the plurality of electromechanical devices; and   means for determining a state of the at least one electromechanical device by comparing the measured capacitance dependent response for the at least one device with the threshold voltage.   
     
     
         18 . The display device of  claim 17 , further comprising means for connecting a filter resistor in series with one or more electromechanical devices. 
     
     
         19 . The device of  claim 17 , wherein the means for determining a threshold voltage is a driver circuit configured to sense an output of the means for measuring to determine a threshold voltage for use in testing the state of one or more of the electromechanical devices.