Fabry-perot interferometric MEMS electromagnetic wave modulator with zero-electric field

• US 20070097694A1
• Filed: 10/31/2005
• Published: 05/03/2007
• Est. Priority Date: 10/31/2005
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Piehl, Arthur, Jilani, Adel, Chaparala, Murali, Yeh, Bao, Przybyla, James, Nikkel, Eric, McKinnell, James, Faase, Kenneth
• Granted Patent: US 7,760,197 B2
• Time in Patent Office: Days
• US Class Current: 362/319
• CPC Class Codes: G01J 3/26 using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters
• 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

Abstract

Systems, methodologies, and other embodiments associated with a micro-electrical-mechanical system (MEMS) Fabry-Perot interferometric device (FPID) are described. Fabricating a MEMS FPID may include fabricating a pixel plate and a reflector plate so a Fabry-Perot cavity is defined therebetween. Fabrication may include producing a capacitor plate that facilitates electrostatically moving the pixel plate. Fabrication may include producing electrical connections between plates and producing circuitry to control plate voltages to facilitate creating an electrostatic force between plates. The MEMS FPID may include stops fabricated from a conductive material and circuitry for maintaining the stops and plates at an electrical potential that will yield a zero electric field contact event.

Claims

1. A micro-electro-mechanical systems (MEMS) electromagnetic wave modulator, comprising:

a first reflector;

a second reflector positioned and oriented with respect to the first reflector to define a Fabry-Perot (FP) cavity between the first reflector and the second reflector, the second reflector being moveable by an electrostatic force;

a capacitor plate electrically connected to at least one of the first reflector and the second reflector, the capacitor plate being configured to facilitate creating the electrostatic force;

at least one of the first reflector, the second reflector, and the capacitor plate including one or more stops fabricated from a conductive material; and

a circuit configured to maintain one or more of, the first reflector, the second reflector, the capacitor plate, and the one or more stops at an electrical potential that will yield a zero electric field contact event.

2. The MEMS electromagnetic wave modulator of claim 1, the first reflector, the second reflector, and the capacitor plate being arranged in a dual capacitor configuration, the first reflector including a trench through the metal when the first reflector includes a stop, the trench electrically isolating the stop on the first reflector from at least one other portion of the first reflector.

3. The MEMS electromagnetic wave modulator of claim 1, the first reflector, the second reflector, and the capacitor plate being arranged in a dual gap configuration.

4. The MEMS electromagnetic wave modulator of claim 1 being incorporated into a spatial light modulator (SLM) configured to at least partially display a pixel of a displayable image.

5. The MEMS electromagnetic wave modulator of claim 1, the FP cavity being controllably selective of a selected wavelength of an electromagnetic wave and a selected intensity of the electromagnetic wave.

6. The MEMS electromagnetic wave modulator of claim 1, the first reflector being a top, semi-reflective mirror fabricated from a conductor.

7. The MEMS electromagnetic wave modulator of claim 6, the second reflector being a bottom, highly reflective mirror fabricated from a conductor.

8. The MEMS electromagnetic wave modulator of claim 7, the one or more stops being zero electric field, reduced stiction stops configured to facilitate controlling, at least in part, a gap size produced by the MEMS actuator.

9. The MEMS electromagnetic wave modulator of claim 8, the one or more stops being fabricated from a conductor.

10. A micro-electro-mechanical systems (MEMS) electromagnetic wave modulator configured to at least partially display a pixel of a displayable image, comprising:

a first reflector being fabricated from a conductor;

a second reflector positioned and oriented with respect to the first reflector to define a Fabry-Perot (FP) cavity between the first reflector and the second reflector, the second reflector being fabricated from a conductor, the second reflector being moveable by an electrostatic force, the FP cavity being controllably selective of a wavelength of the electromagnetic wave and an intensity of the electromagnetic wave;

a capacitor plate electrically connected to at least one of the first reflector and the second reflector;

at least one of the first reflector, the second reflector, and the capacitor plate including one or more stops fabricated from a conductive material;

a circuit configured to maintain one or more of, the first reflector, the second reflector, the capacitor plate, and the one or more stops at an electrical potential that will yield a zero electric field contact event; and

the first reflector, the second reflector, and the capacitor plate being arranged in one or more of, a dual capacitor configuration, and a dual gap configuration.

11. A Fabry-Perot (FP) interferometer, comprising:

a first mirror;

a second mirror oriented and positioned with respect to the first mirror to define an FP cavity therebetween; and

a micro-electro-mechanical systems (MEMS) actuator configured to vary the FP cavity width by moving the second mirror to contact one or more stops made of a conductive material, the one or more stops being maintained at an electrical potential that results in a zero electric field contact event when the second mirror contacts the one or more stops.

12. The FPID of claim 11, the first mirror, the second mirror, and the MEMS actuator being arranged in a dual capacitor configuration.

13. The FPID of claim 11, the first mirror, the second mirror, and the MEMS actuator being arranged in a dual gap configuration.

14. The FPID of claim 11, the one or more stops being fabricated from a conductor.

15. The FPID of claim 11, where the first mirror includes a stop and a trench where the trench is configured to electrically isolate the stop on the first mirror from at least one other portion of the first mirror.

16. A display apparatus, comprising:

a plurality of micro-electro-mechanical system (ME MS) Fabry-Perot interferometric devices (FPID)s formed in an array on a substrate, at least one of the MEMS FPIDs comprising;

a first reflector including a reflective surface;

a second reflector positioned and oriented with respect to the first reflector to define a Fabry-Perot (FP) cavity between the first reflector and the second reflector, the second reflector including a reflective surface, the second reflector being moveable by an electrostatic force;

a capacitor plate electrically connected to at least one of the first reflector and the second reflector, the capacitor plate being configured to facilitate creating the electrostatic force;

at least one of the first reflector, the second reflector, and the capacitor plate including one or more stops fabricated from a conductive material; and

a circuit configured to maintain one or more of, the first reflector, the second reflector, the capacitor plate, and the one or more stops at an electrical potential that will yield a zero electric field contact event;

the plurality of MEMS FPIDs being individually addressable.

17. The display apparatus of claim 16, the MEMS FPIDs being arranged in a dual capacitor configuration, and where when the first reflector includes a stop, the first reflector also includes a trench through the metal that electrically isolates the stop on the first reflector from at least one other portion of the first reflector.

18. The display apparatus of claim 16, the MEMS FPIDs being arranged in a dual gap configuration.

19. A projector, comprising:

a light source configured to provide a white light;

a set of micro-electrical mechanical system (MEMS) Fabry-Perot interferometric devices (FPID)s configured to transmit a set of selected electro-magnetic waves by optical interference; and

a projection lens unit for magnifying and transmitting the set of selected electro-magnetic waves output from the MEMS FPIDs so that the set of selected electromagnetic waves travel toward a selected target, a MEMS FPID comprising;

a first reflector including a reflective surface;

a second reflector positioned and oriented with respect to the first reflector to define a Fabry-Perot (FP) cavity between the first reflector and the second reflector, the second reflector including a reflective surface, the second reflector being moveable by an electrostatic force;

a capacitor plate electrically connected to at least one of the first reflector and the second reflector, the capacitor plate being configured to facilitate creating the electrostatic force;

at least one of the first reflector, the second reflector, and the capacitor plate including one or more stops fabricated from a conductive material; and

a circuit configured to maintain one or more of, the first reflector, the second reflector, the capacitor plate, and the one or more stops at an electrical potential that will yield a zero electric field contact event.

20. A method for fabricating a micro-electro-mechanical (MEMS) Fabry-Perot interferometric device (FPID), comprising:

fabricating circuitry to control a voltage in one or more of a top reflector plate, a pixel plate, and a bottom capacitor plate, where selectively applying different voltages to two or more of the top reflector plate, the pixel plate, and the bottom capacitor plate can create an electrostatic force between the two plates to which the different voltages are applied;

fabricating the bottom capacitor plate;

selectively fabricating one or more stops from a conductive material;

fabricating an electrical connection between the pixel plate and the bottom capacitor plate;

fabricating the pixel plate on a flexure supported platform in a position and orientation with respect to the bottom capacitor plate that facilitates electrostatically moving the pixel plate;

selectively fabricating one or more stops from a conductive material;

fabricating an electrical connection between the top reflector plate and the pixel plate;

fabricating circuitry to facilitate maintaining the one or more stops and one or more of the top reflector plate, the pixel plate, and the bottom capacitor plate at an electrical potential such that contact between the one or more stops and one or more of, the top reflector plate, the pixel plate, and the bottom capacitor plate will result in a zero field contact event;

fabricating the top reflector plate in a position and orientation with respect to the pixel plate so that a Fabry-Perot cavity is defined therebetween;

fabricating a gap between the bottom capacitor plate and the pixel plate; and

fabricating a gap between the pixel plate and the top reflector plate.

21. The method of claim 20, including fabricating the electrical connection between the top reflector plate and the pixel plate and fabricating the electrical connection between the pixel plate and the bottom capacitor plate to define a dual capacitor configuration.

22. The method of claim 20, including fabricating the electrical connection between the top reflector plate and the pixel plate and fabricating the electrical connection between the pixel plate and the bottom capacitor plate to define a dual gap configuration.

23. The method of claim 20, including fabricating a plurality of MEMS FPIDs into an array of individually addressable MEMS FPIDs.

24. A method, comprising:

for a pixel of a pixilated displayable image, controlling one or more of, a predetermined amount of charge over one or more Fabry-Perot (FP) cavities, and a predetermined voltage in one or more plates of an FPID to select a visible wavelength at an intensity by optical interference to display the pixel,

the FP cavity being defined between a top reflector and a pixel plate, one or more of the top reflector and the pixel plate including a stop fabricated from a conductive material;

the method including maintaining the top reflector, the pixel plate, and the one or more stops at an electrical potential so that contact between one or more of the top reflector, the pixel plate, and the one or more stops will be a zero electric field contact event.

25. The method of claim 24, including providing light for illuminating the visible wavelength.

26. The method of claim 25, including dividing a displayable image into the pixilated displayable image.

27. The method of claim 26, where controlling the predetermined amount of charge over one or more FP cavities comprises:

for a red color wavelength, controlling the predetermined amount of charge over a first FP cavity to select a red intensity corresponding to a red color component for the pixel;

for a green color wavelength, controlling the predetermined amount of charge over a second FP cavity to select a green intensity corresponding to a green color component for the pixel;

for a blue color wavelength, controlling the predetermined amount of charge over a third FP cavity to select a blue intensity corresponding to a blue color component for the pixel; and

for a black state, controlling the predetermined amount of charge over a fourth FP cavity to select a black color component for the pixel.

28. The method of claim 27, including selectively controlling the size of at least one FP cavity by controlling a voltage applied to the pixel plate.

29. The method of claim 28, including maintaining a pixel plate stop and an outer bottom capacitor plate ring at an electrical potential so that contact between the pixel plate stop and the outer bottom capacitor plate ring will be a zero electric field event.

30. A system, comprising:

a tunable micro-electro-mechanical system (M EMS) Fabry-Perot interferometric device (FPID) configured to transmit an electromagnetic wave having a desired wavelength and a desired intensity;

means for supplying a selected voltage to one or more plates in the tunable MEMS FPID to facilitate tuning the MEMS FPID; and

means for maintaining the one or more plates and one or more stops in the MEMS FPID at electrical potentials such that contact between the one or more stops and the one or more plates will be zero electric field events.

31. The system of claim 30, the MEMS FPID being arranged in a dual capacitor configuration, and including a first reflector and a second reflector positioned and oriented with respect to the first reflector to define a Fabry-Perot (FP) cavity between the first reflector and the second reflector;

and

the first reflector including a stop formed of a conductive material, the first reflector also including a trench that electrically isolates the stop on the first reflector from at least one other portion of the first reflector.

32. The system of claim 30, where the one or more plates in the tunable MEMS FPID include the one or more stops fabricated from a conductive material.

33. The system of claim 30, where the one or more plates in the tunable MEMS FPID include one or more trenches configured to electrically isolate the one or more stops from at least one other portion of the one or more plates.