Color performance of IMODs

• US 9,024,925 B2
• Filed: 03/13/2013
• Issued: 05/05/2015
• Est. Priority Date: 03/13/2013
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Ma, Jian J., Hong, John Hyunchul, Chang, Tallis Young, Zeng, Huanzhao
• Primary Examiner(s): Edun, Muhammad N
• Application Number:
  US13/801,134
• Publication Number:
  US 20140267197A1
• Time in Patent Office: 783 Days
• Field of Search: None
• US Class Current: 345/204
• 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 2310/0278 Details of driving circuits arranged to drive both scan and data electrodes
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/3466 based on interferometric effect

Abstract

This disclosure provides systems, methods and apparatus, including computer programs encoded on computer storage media, for making and controlling single-mirror interferometric modulators (IMODs), which may be multi-state IMODs or analog IMODs. In one aspect, a movable reflector stack or an absorber stack of an IMOD may include at least one protrusion that is configured to cause the movable reflector stack to be tilted relative to the absorber layer when the movable reflector stack is moved close to the absorber stack. The protrusion may be configured to cause color averaging when the IMOD is in a white state. The absorber stack may include an absorber layer having a lower extinction coefficient value at a red wavelength and a higher extinction coefficient value at a blue wavelength.

Claims

1. An interferometric modulator (IMOD), comprising:

a substrate;

an absorber stack disposed on the substrate;

a movable reflector stack including a metal mirror and a dielectric stack, the dielectric stack being disposed between the absorber stack and the metal mirror, the dielectric stack being configured to reduce a standing wave node separation for light reflecting from the movable reflector stack, as compared to light reflecting from the movable reflector stack in the absence of the dielectric stack, such that the IMOD is configured for reflecting a white color when the reflector stack is in close proximity to the absorber stack, the movable reflector stack being further configured to be moved between a plurality of positions relative to the absorber stack, each of the positions corresponding with an IMOD color state including a white state for reflecting the white color, a black state, and one or more other colored states; and

a first protrusion connected to the movable reflector stack or to the absorber stack,

wherein the first protrusion has a first height and is configured to cause the movable reflector stack to be tilted relative to the absorber stack when the movable reflector stack is moved close to the absorber stack.

2. The IMOD of claim 1, wherein the first protrusion is configured to cause color averaging when the moveable reflector stack is tilted.

3. The IMOD of claim 2, wherein the first protrusion is configured to cause color averaging when the IMOD is in a white state.

4. The IMOD of claim 1, wherein the first protrusion is connected to a surface of the movable reflector stack facing the absorber layer.

5. The IMOD of claim 1, further including a second protrusion having a second height that is different from the first height.

6. The IMOD of claim 1, further including a plurality of additional protrusions having varying heights that are different from the first height.

7. The IMOD of claim 1, wherein the first protrusion is configured to cause the movable reflector stack to be tilted by less than one degree relative to the absorber stack when the movable reflector stack is moved close to the absorber stack.

8. The IMOD of claim 1, wherein the dielectric stack includes a high-index layer and a low-index layer.

9. The IMOD of claim 8, wherein the low-index layer has a lower chromatic dispersion than that of the high-index layer.

10. The IMOD of claim 8, wherein the low-index layer is formed of SiON or SiO₂.

11. The IMOD of claim 8, wherein the high-index layer is formed of TiO₂, ZrO₂ or Nb₂O₅.

12. A display device that includes the IMOD of claim 1.

13. The display device of claim 12, further including a control system configured to control the display device.

14. The display device of claim 13, wherein the control system is configured to process image data.

15. The display device of claim 14, wherein the control system further comprises:

a driver circuit configured to send at least one signal to a display of the display device; and

a controller configured to send at least a portion of the image data to the driver circuit.

16. The display device of claim 14, wherein the control system further comprises:

an image source module configured to send the image data to the processor, wherein the image source module includes at least one of a receiver, transceiver, and transmitter.

17. The display device of claim 14, further comprising:

an input device configured to receive input data and to communicate the input data to the control system.

18. An interferometric modulator (IMOD), comprising:

a substrate;

an absorber stack disposed on the substrate;

a movable reflector stack configured to be moved between a plurality of positions relative to the absorber stack, each of the positions corresponding with an IMOD color state including a white state for reflecting the white color, a black state, and one or more other colored states, the IMOD being configured for reflecting a white color when the reflector stack is in close proximity to the absorber stack, the movable reflector stack including;

a metal mirror; and

node separation reduction means for reducing a standing wave node separation for light reflecting from the movable reflector stack, as compared to light reflecting from the movable reflector stack in the absence of the node separation reduction means; and

tilting means for causing the movable reflector stack to be tilted relative to the absorber layer when the movable reflector is moved close to the absorber layer.

19. The IMOD of claim 18, wherein the tilting means is configured to cause color averaging when the IMOD is in a white state.

20. The IMOD of claim 18, wherein the tilting means includes a first protrusion connected to the movable reflector stack or to the absorber stack, the first protrusion having a first height.

21. The IMOD of claim 20, wherein the tilting means includes a second protrusion having a second height that is different from the first height.

22. The IMOD of claim 18, wherein the node separation reduction means includes a high-index layer and a low-index layer and wherein the node separation reduction means has a lower chromatic dispersion than that of the high-index layer.

23. A method of controlling an interferometric modulator (IMOD), the method comprising:

receiving an applied voltage differential between a moveable reflector stack and an absorber stack;

moving the movable reflector stack to a position proximate the absorber stack in response to the applied voltage differential;

tilting the movable reflector stack by less than one degree relative to the absorber stack by causing a first protrusion disposed on the movable reflector stack or the absorber stack to come in contact with the other stack.

24. The method of claim 23, wherein the first protrusion has a first height and wherein the tilting process involves causing a second protrusion to make contact with the movable reflector stack or the absorber stack, the second protrusion having a second height.

25. The method of claim 23, wherein the first protrusion has a first height and wherein the tilting process involves causing a plurality of additional protrusions to make contact with the movable reflector stack or the absorber stack, the plurality of additional protrusions having varying heights that are different from the first height.

26. The method of claim 23, wherein the tilting process causes color averaging when the IMOD is in a white state.

27. An interferometric modulator (IMOD), comprising:

a substrate;

an absorber stack disposed on the substrate, the absorber stack including an absorber layer that includes a material having a red extinction coefficient value at a red wavelength and a blue extinction coefficient value at a blue wavelength, the blue extinction coefficient value being a higher value than the red extinction coefficient value;

a movable reflector stack configured to be moved between a plurality of positions relative to the absorber stack, each of the positions corresponding with an IMOD color state including a white state for reflecting the white color, a black state, and one or more colored states, the IMOD being configured to reflect a white color when the moveable reflector stack is in close proximity to the absorber stack, the movable reflector stack including;

a metal mirror; and

a dielectric stack disposed between the absorber stack and the metal mirror.

28. The IMOD of claim 27, wherein the absorber stack includes an impedance-matching layer.

29. The IMOD of claim 28, wherein the impedance-matching layer includes a pair of high dispersion and low dispersion layers, the low dispersion layer including SiO₂ or SiON and the high dispersion layer including TiO2 or Si₃N₄.

30. The IMOD of claim 27, wherein the absorber layer is formed of vanadium, germanium or osmium.

31. The IMOD of claim 27, further comprising:

a first protrusion connected to the movable reflector stack or to the absorber stack, wherein the first protrusion has a first height and is configured to cause the movable reflector stack to be tilted relative to the absorber layer when the movable reflector stack is moved close to the absorber stack.

32. The IMOD of claim 31, wherein the first protrusion is configured to cause color averaging when the moveable reflector stack is tilted.

33. The IMOD of claim 31, wherein the first protrusion is configured to cause color averaging when the IMOD is in a white state.

34. The IMOD of claim 31, wherein the first protrusion is connected to a surface of the movable reflector stack facing the absorber layer.

35. The IMOD of claim 31, wherein the first protrusion is configured to cause the movable reflector stack to be tilted by less than one degree relative to the absorber stack when the movable reflector stack is moved close to the absorber stack.