DEVICES AND METHODS FOR ACHIEVING NON-CONTACTING WHITE STATE IN INTERFEROMETRIC MODULATORS

• US 20140218786A1
• Filed: 01/31/2014
• Published: 08/07/2014
• Est. Priority Date: 05/04/2011
• Status: Abandoned Application

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Hong, John H., Mignard, Marc Maurice
• Application Number:
  US14/170,413
• Publication Number:
  US 20140218786A1
• Time in Patent Office: Days
• US Class Current: 359/292
• 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: G02B 26/007 the movable or deformable optical element controlling the colour, i.e. a spectral characteristic, of the light
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G02B 26/08 for controlling the direction of light in light guides G02B6/35
• CPC Class Codes: G02B 26/0825 the reflecting element being a flexible sheet or membrane, e.g. for varying the focus flexible mirrors for cosmetic use A45D42/24
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 26/0875 by means of one or more refracting elements
• CPC Class Codes: G02B 5/1814 structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings G02B5/189 takes precedence
• CPC Class Codes: G02B 5/26 Reflecting filters G02B5/28 takes precedence
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G02F 1/0128 based on electro-mechanical, magneto-mechanical, elasto-optic effects
• CPC Class Codes: G09G 3/3433 using light modulating elements actuated by an electric field and being other than liquid crystal devices and electrochromic devices using liquid crystal devices G09G3/36; using electrochromic devices G09G3/38
• CPC Class Codes: G09G 3/3466 based on interferometric effect
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607

Abstract

This disclosure provides systems, methods and apparatus for providing white light color output from an electromechanical systems (EMS) device with reduced likelihood of stiction. In one aspect, interferometric modulators are configured to provide a white color output while having a non-zero modulator gap dimension. Such a feature can reduce problems associated with zero modulator gap dimensions such as stiction. Various methodologies can be used to yield such a non-zero modulator gap and a white color output. In some implementations, for example, an optical element that introduced wavelength dependent phase shift is used. In some implementations this wavelength dependent phase shifting optical element includes a stack of color filters, a hologram, a diffraction grating, or layers of material having specific thicknesses and wavelength dependent indices of refraction.

Claims

1. An optical device, comprising:

a reflector configured to reflect light;

an absorber positioned relative to the reflector so as to provide a first gap between the reflector and the absorber while in a first state and to provide a second gap between the reflector and the absorber while in a second state, the first gap being smaller than the second gap; and

an optical element disposed with respect to the reflector and the absorber such that when the absorber and the reflector are separated by a non-zero distance of z₀ that provides said first gap between said absorber and said reflector, incident light transmitted through the absorber and reflected from the reflector returns to the absorber and passes therethrough as a substantially white color output from the optical device.

2. The optical device of claim 1, wherein the reflector is configured to move with application of an electrical signal to the optical device.

3. The optical device of claim 1, wherein the reflector and the absorber include metal.

4. The optical device of claim 1, wherein the optical element includes a diffraction grating, at least one wavelength selective reflective filter, or a hologram.

7. The optical device of claim 1, wherein the optical element includes a plurality of layers of material having indices of refraction that vary with wavelength.

8. The optical device of claim 1, wherein the optical element includes at least one layer of material comprising a complex refractive index.

9. The optical device of claim 1, wherein the optical element is disposed between the absorber and the reflector.

10. The optical device of claim 1, wherein the first gap includes an air gap that is at least about 50 nm such that the absorber and the reflector are separated by at least about 50 nm.

12. The optical device of claim 10, wherein the air gap is at least about 100 nm such that the absorber and the reflector are separated by at least about 100 nm.

13. The optical device of claim 1, wherein a substantially black color output for the optical device is obtained when the absorber and the reflector are separated by a distance of z_Black+z₀.

14. The optical device of claim 13, wherein different color outputs for the optical device are obtained when the absorber and the reflector are separated by a distance greater than z_Black+z₀.

16. A display having an array of optical devices of claim 1.

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18. An interferometric modulator, comprising:

an absorber configured to receive light and pass at least a portion of the light; and

one or more optical elements including a reflective surface configured to receive light from the absorber and reflect the light back to the absorber,

wherein the one or more optical elements are configured to provide different phase shifts for different wavelength components of the light reflected back to the absorber such that a plurality of wavelength components substantially pass through the absorber to yield a substantially white color output from the interferometric modulator when the absorber is spaced apart from said reflective surface by a first gap while in a first state, and wherein the interferometric modulator yields a non-white color output when the absorber is spaced apart form said reflective surface by a second gap while in a second state, the first gap being smaller than the second gap.

19. The interferometric modulator of claim 18, wherein the wavelength components passed through the absorber and included in the white output correspond to red, green and blue color light.

20. The interferometric modulator of claim 18, wherein the one or more optical elements include at least one thin film reflecting filter configured to selectively reflect at least one of the wavelength components such that different wavelength components propagate different distances from the reflective surface to the absorber thereby introducing different phase shifts therebetween.

21. The interferometric modulator of claim 18, wherein the one or more optical elements include at least one hologram having a plurality of phase-shifting features configured to phase shift different wavelength components different amounts.

22. The interferometric modulator of claim 21, wherein the hologram includes said reflective surface so as to reflect the waves components back to the absorber.

23. The interferometric modulator of claim 21, wherein the hologram is a transmissive hologram and said reflective surface is not part of the hologram.

24. The interferometric modulator of claim 18, wherein the one or more optical elements include a plurality of optical layers, each layer having a thickness and a refractive index, such that the different wavelength components passing through the plurality of optical layers and returning to the absorber are provided with the different phase shifts.

25. The interferometric modulator of claim 18, wherein the one or more optical elements include at least one of a dielectric layer and a reflector layer having a complex refractive index so as to provide different phase shifts to different wavelength components reflected back to the absorber.

26. The interferometric modulator of claim 18, wherein the one or more optical elements include a dielectric layer and a reflector layer, each of the absorber, dielectric layer and reflector layer having a complex refractive index such that the absorber, dielectric layer and the reflector layer provide different phase shifts to different wavelength components.

27. The interferometric modulator of claim 26, wherein at least one of the absorber and the dielectric layer has a real portion of the complex refractive index that increases as a function of wavelength.

28. The interferometric modulator of claim 18, wherein the one or more optical elements include a diffraction grating configured to provide different path lengths for different wave components, the difference in path lengths providing different phase shifts for the different wavelength components.

29. The interferometric modulator of claim 18, wherein the first gap is at least about 50 nm such that the absorber and the reflective surface are separated at least about 50 nm.

30. The interferometric modulator of claim 18, wherein the first gap is at least about 100 nm such that the absorber and the reflective surface are separated at least about 100 nm.

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39. An interferometric modulator, comprising:

means for absorbing light that is configured to receive light and pass at least a portion of the received light; and

one or more optical elements including a reflective surface configured to receive light from the absorbing means and reflect the light back to the absorbing means,

wherein the one or more optical elements are configured to provide different phase shifts for different wavelength components of the light reflected back to the absorbing means such that a plurality of wavelength components substantially pass through the absorbing means to yield a substantially white color output from the interferometric modulator when the absorbing means is spaced apart from said reflective surface by a first gap while in a first state, and wherein the interferometric modulator yields a non-white color output when the absorbing means is spaced apart from said reflective surface by a second gap while in a second state, the first gap being smaller than the second gap.

40. The interferometric modulator of claim 39, wherein the absorbing means includes an absorber.

41. The interferometric modulator of claim 39, wherein the wavelength components passed through the absorbing means and included in the white output correspond to red, green and blue color light.

42. The interferometric modulator of claim 39, wherein the one or more optical elements include at least one of:

a thin film reflecting filter;

at least one hologram;

a plurality of optical layers; and

a diffraction grating.

43. The interferometric modulator of claim 39, wherein the first gap is at least about 50 nm such that the absorbing means and the reflective surface are separated at least about 50 nm.