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

• US 8,207,920 B2
• Filed: 05/18/2009
• Issued: 06/26/2012
• Est. Priority Date: 08/27/2004
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Mignard, Marc, Chui, Clarence, Mathew, Mithran C., Sampsell, Jeffrey B.
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): Sharifi-Tafreshi, Koosha
• Application Number:
  US12/468,004
• Publication Number:
  US 20090224748A1
• Time in Patent Office: 1,135 Days
• Field of Search: 345/55, 345/84, 345/85, 359/290, 359/291, 359/902, 359/904, 359/196.1
• US Class Current: 345/84
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81C 99/003 Characterising MEMS devices, e.g. measuring and identifying electrical or mechanical constants
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G02B 26/00 Optical devices or arrangements for the control of light using movable or deformable optical elements control of light by modification of the optical properties of the media of the elements involved therein G02F1/00
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G09G 2300/0473 Use of light emitting or modulating elements having two or more stable states when no power is applied
• CPC Class Codes: G09G 2310/0278 Details of driving circuits arranged to drive both scan and data electrodes
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/12 Test circuits or failure detection circuits included in a display system, as permanent part thereof
• CPC Class Codes: G09G 3/3466 based on interferometric effect

Abstract

A method for sensing the actuation and/or release voltages of a electromechanical system or a microelectromechanical device include applying a varying voltage to the device and sensing its state and different voltage levels. 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.

Claims

1. A mirror system comprising:

an interferometric modulator array of mirrors;

a timing control circuit for activating each of the mirrors;

a drive circuit configured to apply one or more test voltages or currents; and

a sensing circuit configured to sense a state of at least one of the mirrors and determine one or both of an actuation voltage and a release voltage based at least in part on the sensed state of the mirrors, wherein the sensing circuit comprises test circuitry configured to compare a sensed voltage of said at least one of the mirrors to a threshold voltage.

2. The mirror system of claim 1, wherein the sensing circuit include resistive and capacitive elements in parallel.

3. The mirror system of claim 1, wherein the sensing circuit comprises an integrator with one or more passive feedback components.

4. The mirror system of claim 1, wherein the timing control circuit and the sensing circuit are embodied in an integrated circuit.

5. The mirror system of claim 1, wherein the mirror system comprises an electromechanical system (EMS) or a microelectromechanical system (MEMS).

6. The mirror system of claim 1, wherein the mirrors comprise any reflective surface.

7. The mirror system of claim 1, wherein the mirrors can be positioned in a reflective position and a non-reflective position.

8. The mirror system of claim 1, wherein the timing control circuit controls an activation of the mirror.

9. The mirror system of claim 1, wherein the mirrors are movable.

10. A method of pixel state sensing for modifying a drive voltage of an array of mirrors and a timing control circuit for controlling each of the mirrors, the method comprising:

applying a first test voltage or current to charge a mirror for a predetermined amount of time;

sensing a first state of the mirror to determine a first actuation or release voltage;

applying a second test voltage or current to charge the mirror for the predetermined amount of time;

sensing a second state of the mirror to determine a second actuation or release voltage; and

modifying the drive voltage based on the determined first and second actuation or release voltages to control a voltage at which the mirror is actuated or released.

11. A system for calibrating a drive voltage for an array of mirrors and a timing control circuit for controlling each of the mirrors, the system comprising:

means for applying a first test voltage or current to charge a mirror for a predetermined amount of time;

means for sensing a first state of the mirror to determine a first actuation or release voltage;

means for applying a second test voltage or current to charge the mirror for the predetermined amount of time;

means for sensing a second state of the mirror to determine a second actuation or release voltage; and

means for modifying the drive voltage based on the determined first and second actuation or release voltages to control a voltage at which the mirror is actuated or released.