Display system having electrode modulation to alter a state of an electro-optic layer

• US 6,144,353 A
• Filed: 08/27/1997
• Issued: 11/07/2000
• Est. Priority Date: 12/19/1996
• Status: Expired due to Term

• Current Assignee: Emerson Radio Corporation (Nimble Holdings Co. Ltd.)
• Original Assignee: Colorado Microdisplay Inc.
• Inventors: McKnight, Douglas
• Primary Examiner(s): Hjerpe, Richard A.
• Assistant Examiner(s): NGUYEN, FRANCIS N
• Application Number:
  US08/920,603
• Time in Patent Office: 1,168 Days
• Field of Search: 345/94-95, 345/97, 345/96, 345/208, 345/88, 349/96, 349/86-87, 349/33
• US Class Current: 345/94
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0823 used to establish symmetry in driving, e.g. with polarity inversion
• CPC Class Codes: G09G 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2310/063 Waveforms for resetting the whole screen at once
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

Methods and apparatuses for display systems which modulate a control electrode to cause an electro-optic layer to be reset to a state in which display data is not viewable. In one embodiment of the invention, a display system includes a first substrate having a first plurality of pixel electrodes for receiving a first plurality of pixel data values representing a first image to be displayed. The display system further includes an electro-optic layer which is operatively coupled to the pixel electrodes and an electrode operatively coupled to the electro-optic layer. The electro-optic layer comprises a polymer dispersed liquid crystal material. The display system displays the first image and then applies a first control voltage to the electrode to alter a state of the electro-optic layer such that the first image substantially not displayed and then the display system displays a second image represented by a second plurality of pixel data values after the electrode receives a second control voltage. Various other apparatuses and methods are described.

Claims

1. A method for operating a display system, said display system comprising a first substrate having a plurality of pixel electrodes, an electro-optic layer operatively coupled to said pixel electrodes and an electrode operatively coupled to said electro-optic layer, said electro-optic layer comprising a polymer dispersed liquid crystal material, said method comprising:

applying a first plurality of pixel data values to said plurality of pixel electrodes such that a first pixel data represented by said first plurality of pixel data values is displayed;

applying a first control voltage to said electrode to alter a state of said electro-optic layer such that said first pixel data is substantially not displayed;

applying a second plurality of pixel data values to said plurality of pixel electrodes, said second plurality of pixel data values representing a second pixel data, said second plurality of pixel data values being applied while a voltage applied to said electrode causes no pixel data values to be displayed;

displaying said second pixel data.

2. A method as in claim 1 wherein said displaying said second pixel data comprises:

applying a second control voltage to said electrode to alter said state of said electro-optic layer such that said second pixel data is displayed, and

wherein a first image is represented by said first pixel data and a second image is represented by said second pixel data.

3. A method as in claim 2 wherein said first image comprises a first color subframe and said second image comprises a second color subframe.

4. A method as in claim 2 wherein said polymer dispersed liquid crystal material has at least a first light altering state and a second light altering state and wherein said first control voltage sets said liquid crystal in said first light altering state such that light is not substantially scattered when passing through said electro-optic layer.

5. A method as in claim 4 wherein said second control voltage sets said polymer dispersed liquid crystal material in said second light altering state such that light is capable of being scattered when passing through said electro-optic layer.

6. A method as in claim 5 wherein said light passing through said electro-optic layer is not polarized.

7. A method as in claim 6 wherein said applying a first control voltage and said applying a second plurality of pixel data values overlap at least partially in time.

8. A method as in claim 7 wherein said applying a first control voltage and said applying a second plurality of pixel data values occur substantially contemporaneously in time.

9. A method as in claim 7 wherein said electrode is a common cover glass electrode which receives a DC balanced signal over time.

10. A method as in claim 5 wherein when said first control voltage is applied light from an illumination source is reflected, for all pixels in said display system, out of a collection angle of an imaging optical system, said display system comprising said imaging optical system.

11. A method as in claim 10 wherein when said second control voltage is applied light from at least some of said pixels is reflected within said collection angle.

12. A method as in claim 5 wherein said first control voltage is an AC (alternating current) voltage.

13. A method as in claim 5 wherein said first control voltage is approximately equal to one of a maximum voltage and a minimum voltage which can be applied to said plurality of pixel electrodes.

14. A method as in claim 5 wherein said first control voltage is approximately equal to one of a maximum voltage plus a first offset voltage and a minimum voltage minus a second offset voltage, wherein said maximum voltage and said minimum voltage are the maximum and minimum voltages which can be applied to said plurality of pixel electrodes.

15. A method as in claim 5 wherein said electrode is an electrode disposed in said first substrate with said plurality of pixel electrodes.

16. A method as in claim 7 wherein said applying a first control voltage further comprises applying a third control voltage after said first control voltage and before said applying said second control voltage, wherein said third control voltage holds said liquid crystal in said first light altering state and said first control voltage rapidly places said liquid crystal in said first light altering state.

17. A method as in claim 10 wherein said second plurality of pixel data values is stored in a plurality of buffers on said first substrate while said first pixel data is displayed.

18. A method as in claim 5 further comprising:

applying a first compensating voltage to a plurality of compensating electrodes disposed on said first substrate.

19. A method as in claim 18 wherein said applying a first compensating voltage and said step of applying a first control voltage overlap at least partially in time.

20. A method as in claim 19 wherein said applying a first compensating voltage and said step of applying a first control voltage occur substantially contemporaneously in time.

21. A method for operating a display system, said display system comprising a first substrate having a first plurality of pixel electrodes and a second plurality of pixel electrodes, an electro-optic layer operatively coupled to said first and said second plurality of pixel electrodes, said electro-optic layer comprising a polymer dispersed liquid crystal material, and a first electrode and a second electrode, said method comprising:

(a) applying a first plurality of pixel data values to said first plurality of pixel electrodes, said first plurality of pixel data values representing a first portion of an image;

(b) applying a first control voltage to said first electrode to alter a state of a first portion of said electro-optic layer such that said first portion of said image is not displayed, said first control voltage being applied to said first electrode while applying said first plurality of pixel data values to said first plurality of pixel electrodes such that said first portion of said image is not displayed;

(c) displaying said first portion of said image;

(d) applying a second plurality of pixel data values to said second plurality of pixel electrodes, said second plurality of pixel data values representing a second portion of said image;

(e) applying a second control voltage to said second electrode to alter a state of a second portion of said electro-optic layer such that said second portion of said image is not displayed, said second control voltage being applied to said second electrode while applying said second plurality of pixel data values to said second plurality of pixel electrodes such that said second portion of said image is not displayed;

(f) displaying said second portion of said image.

22. A method as in claim 21 wherein said applying said first plurality of pixel data values and said applying said first control voltage overlap at least partially in time and wherein said applying said second plurality of pixel data values and said applying said second control voltage overlap at least partially in time.

23. A method as in claim 22 wherein said first control voltage and said second control voltage are approximately equal.

24. A method as in claim 22 wherein said image is at least a portion of a color subframe and wherein said display system is a time sequential color system.

25. A method as in claim 24 wherein said first portion is one-half of said image and said second portion is the other half of said image.

26. A method as in claim 25 wherein said color subframe is one of a red subframe, a green subframe or a blue subframe.

27. A method as in claim 22 wherein said image is at least a portion of a color frame and wherein said display system is a spatial color system having for each pixel of said display system a first color component subpixel, a second color component subpixel and a third color component subpixel.

28. A method as in claim 22 wherein said displaying said first portion comprises:

applying a third control voltage to said first electrode, after said applying said first plurality of pixel data values and after said applying said first control voltage, to alter said state of said first portion of said electro-optic layer such that said first portion is displayed.

29. A method as in claim 28 wherein said displaying said second portion comprises:

applying a fourth control voltage to said second electrode, after said applying said second plurality of pixel data values and after said applying said second control voltage, to alter said state of said second portion of said electro-optic layer such that said second portion is displayed.

30. A method as in claim 29 wherein said applying said first plurality of pixel data values and said applying said first control voltage overlap at least partially in time and wherein said displaying said first portion and said applying said second plurality of pixel data values and said applying said second control voltage overlap at least partially in time.

31. A method as in claim 30 wherein said polymer dispersed liquid crystal material has at least a first light altering state and a second light altering state and wherein said first and said second control voltages set said liquid crystal in said first light altering state such that light is not substantially scattered when passing through said electro-optic layer.

32. A method as in claim 31 wherein said third and said fourth control voltages set said polymer dispersed liquid crystal material in said second light altering state such that light is capable of being scattered when passing through said electro-optic layer.

33. A method as in claim 31 wherein said first electrode is a first portion of a cover glass electrode disposed on a second substrate and said second electrode is a second portion of said cover glass electrode, said first portion and said second portion of said cover glass electrode not being electrically coupled.

34. A method as in claim 31 wherein said first electrode comprises at least an electrode disposed in said first substrate with said first plurality of pixel electrodes and said second electrode comprises at least another electrode disposed in said first substrate with said second plurality of pixel electrodes.

35. A method as in claim 22 wherein said displaying said first portion comprises illuminating said display system with at least one first pulse of illumination.

36. A method as in claim 35 wherein said displaying said second portion comprises illuminating said display system with at least one second pulse of illumination.

37. A method as in claim 36 wherein said first pulse and said second pulse do not provide continuous illumination.

38. A display system comprising:

a first substrate having a first plurality of pixel electrodes for receiving a first plurality of pixel data values representing a first image to be displayed;

an electro-optic layer operatively coupled to said pixel electrodes, said electro-optic layer comprising a polymer dispersed liquid crystal material;

an electrode operatively coupled to said electro-optic layer, said display system displaying said first image and then applying a first control voltage to said electrode to alter a state of said electro-optic layer such that said first image is substantially not displayed while loading a second plurality of pixel data values onto said first plurality of pixel electrodes and then said display system displaying a second image represented by said second plurality of pixel data values after said electrode receives a second control voltage.

39. A display system as in claim 38 further comprising an electrode control driver coupled to said electrode to provide said first control voltage to said electrode.

40. A display system as in claim 39 wherein said electrode control driver provides said first control voltage in a phase controlled relationship relative to ending the display of said first image and provides said second control voltage in a phase controlled relationship relative to beginning the display of said second image.

41. A display system as in claim 40 wherein when said first control voltage is applied to said electrode, said first image cannot be substantially displayed even if said first plurality of pixel electrodes retain said first plurality of pixel data values.

42. A display system as in claim 41 wherein upon said second control voltage being applied to said electrode, said second image is displayed such that substantially all of said first plurality of pixel electrodes cause a corresponding plurality of pixels in said second image to be simultaneously updated.

43. A display system as in claim 42 wherein said corresponding plurality of pixels include pixels on a plurality of rows of pixels of said display system.

44. A display system as in claim 43 wherein said first image comprises a first color subframe and said second image comprises a second color subframe.

45. A display system as in claim 43 wherein said polymer dispersed liquid crystal material has at least a first light altering state and a second light altering state and wherein said first control voltage sets said liquid crystal in said first light altering state such that light is not substantially scattered when passing through said electro-optic layer and wherein said second control voltage sets said liquid crystal in said second light altering state such that light is capable of being scattered when passing through said electro-optic layer.

46. A display system as in claim 45 wherein said electrode is a common cover glass electrode which receives a DC balanced signal over time.

47. A display system as in claim 45 further comprising:

an illumination source which provides a source of light which is directed toward said first substrate;

an imaging optical system having a collection angle for receiving light from said first substrate, wherein when said first control voltage is applied, light from said illumination source is reflected, for all pixels in said display system, out of said collection angle, and wherein when said second control voltage is applied light from at least some of said pixels is reflected within said collection angle.