SYSTEM AND METHOD OF SENSING ACTUATION AND RELEASE VOLTAGES OF AN INTERFEROMETRIC MODULATOR
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.