Interferometric modulator in transmission mode

• US 7,944,604 B2
• Filed: 02/10/2009
• Issued: 05/17/2011
• Est. Priority Date: 03/07/2008
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Sampsell, Jeff, Ganti, Surya, Khazeni, Kasra
• Primary Examiner(s): HASAN, MOHAMMED A
• Application Number:
  US12/368,915
• Publication Number:
  US 20090225395A1
• Time in Patent Office: 826 Days
• Field of Search: 359290-298, 359/318
• US Class Current: 359/291
• 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

A transmissive micromechanical device includes a substrate, an optical stack over the substrate and a moveable membrane over the optical stack. The moveable membrane may include a partially reflective mirror and be configured to move from a first position to a second position. When the movable membrane is in the first position the transmissive micromechanical device is configured to pass light of a predetermined color and when the movable membrane is in the second position, the micromechanical device is configured to block substantially all of light incident on the substrate.

Claims

1. A transmissive micromechanical device, comprising:

a substrate;

a moveable membrane positioned on a first side of the substrate, the moveable membrane comprising a partially reflective mirror; and

a light source positioned on a second side of the substrate and configured to emit light incident on the second side of the substrate,

wherein the movable membrane is configured to move from a first position to a second position,

wherein with the movable membrane in the first position visible light of a desired wavelength range passes through the substrate and through the moveable membrane, and

wherein with the movable membrane in the second position substantially all of the visible light of the desired wavelenght range is blocked.

2. The transmissive micromechanical device of claim 1, wherein with the movable membrane in the second position at least 90% of visible light incident on the second side of the substrate is blocked.

3. The transmissive micromechanical device of claim 1, wherein with the movable membrane in the second position at least 95% of visible light incident on the second side of the substrate is blocked.

4. The transmissive micromechanical device of claim 1, wherein with the movable membrane in the second position at least 98% of visible light incident on the second side of the substrate is blocked.

5. The transmissive micromechanical device of claim 1, wherein with the movable membrane in the second position at least 99% of visible light incident on the second side of the substrate is blocked.

6. The transmissive micromechanical device of claim 1, wherein with the moveable membrane in the second position the moveable membrane defines at least in part an optical interference cavity configured to pass light of desired wavelengths;

and wherein the movable membrane comprises an absorber layer configured to absorb light of other wavelengths.

7. The transmissive micromechanical device of claim 6, wherein the absorber layer comprises a semiconductor.

8. The transmissive micromechanical device of claim 1 further comprising a mechanical layer comprising a dielectric material.

9. The transmissive micromechanical device of claim 8, wherein the dielectric material comprises SiN or SiO₂.

10. The transmissive micromechanical device of claim 8 further comprising a thin layer of a metal disposed on top of the dielectric material.

11. The transmissive micromechanical device of claim 10, wherein the thin layer of metal comprises Au or Ag.

12. The transmissive micromechanical device of claim 1, wherein the substrate comprises a transparent substrate.

13. The transmissive micromechanical device of claim 1, wherein the partially reflective mirror comprises a flexible, silver-coated membrane.

14. The transmissive micromechanical device of claim 1 further comprising a lens configured to focus light passing through the substrate and the movable membrane.

15. A transmissive mechanical device, comprising a first optical stack and a second optical stack selectably separated by a gap, wherein the first optical stack comprises a substantially transparent substrate, a first low refractive index layer, and a first high refractive index layer, wherein the second optical stack comprises a substantially transparent substrate, a second low refractive index layer, and a second high refractive index layer, wherein the first optical stack comprises two layers of MgF₂ and two layers of SiC, wherein a first of the MgF₂ layers is disposed on the substrate, a first of the SiC layers is disposed on the first MgF₂ layer, a second of the MgF₂ layers is disposed on the first SiC layer, and a second of the SiC layers is disposed on the second MgF₂ layer.

16. The transmissive mechanical device of claim 15, wherein the second optical stack comprises two layers of MgF₂ and two layers of SiC, wherein a first of the MgF₂ layers is disposed on the substrate, a first of the SiC layers is disposed on the first MgF₂ layer, a second of the MgF₂ layers is disposed on the first SiC layer, and a second of the SiC layers is disposed on the second MgF₂ layer.

17. The transmissive mechanical device of claim 15 further comprising a light source and a lens configured to focus light exiting the transmissive mechanical device.

18. A transmissive mechanical device, comprising:

a first optical stack separated by a gap from a second optical stack;

a light source positioned on a first side of the first optical stack and configured to emit light through the first optical stack to the second optical stack; and

a lens configured to focus light exiting the second optical stack,

wherein the first optical stack comprises a glass substrate, at least one material with an index of refraction greater than 2 and at least one material with an index of refraction less than 1.3, and

wherein the second optical stack comprises at least one material with an index of refraction greater than 2 and at least one material with an index of refraction less than 1.3.

19. The transmissive mechanical device of claim 18, wherein a first material with a higher relative index of refraction is positioned so as to sandwich a second material comprising a lower relative index of refraction.

20. The transmissive mechanical device of claim 19, wherein a difference between the index of refraction of the sandwiching layers and the middle layer is maximized.

21. The transmissive mechanical device of claim 18, wherein at least one layer comprises a dielectric.

22. The transmissive mechanical device of claim 18, wherein at least one layer comprises a semiconductor.

23. The transmissive mechanical device of claim 18, wherein the thickness of each layer is greater than 25% of the wavelength of light incident on the substrate.

24. A transmissive interferometric modulator (“

IMOD”

), comprising;

a transparent substrate;

a first reflecting layer disposed on a first surface of the transparent substrate;

a movable membrane comprising a second reflecting layer, wherein the second reflecting layer and the first reflecting layer form a variable optical cavity; and

a light source, wherein the transparent substrate is positioned between the light source and the movable membrane, wherein the light source is configured to emit light incident of the transparent substrate,

wherein the variable optical cavity is adjusted as the movable membrane moves from a first position to a second position, and

wherein when the movable membrane is in the first position, the movable membrane allows transmission of wavelengths in the range of ultraviolet or infrared light, and absorbs substantially the entire wavelength range of incident visible light.

25. The transmissive IMOD of claim 24, wherein the first reflecting layer comprises a material with an index of refraction greater than 2.0.

26. The transmissive IMOD of claim 24, wherein the first reflecting layer comprises Au, Ag or SiC.

27. The transmissive IMOD of claim 24, wherein the entire wavelength of incident light is a particular wavelength.

28. The transmissive IMOD of claim 24, wherein when the movable membrane is in the first position at approximately 300 nm a peak transmission is approximately 650 nm.

29. The transmissive IMOD of claim 24, wherein when the movable membrane is in the second position a peak transmission is approximately 450 nm.

30. The transmissive IMOD of claim 24 further comprising a linear polarizer.

31. The transmissive IMOD of claim 24 further comprising an optical isolator.

32. The transmissive IMOD of claim 24 further comprising a lens configured to focus light exiting the movable membrane.

33. The transmissive IMOD of claim 25, wherein the lens is configured to focus light onto a pixel.

34. The transmissive IMOD of claim 25, wherein the lens comprises an array of lenses.