Color filters and sequencers using color selective light modulators

• US 6,882,384 B1
• Filed: 07/31/1998
• Issued: 04/19/2005
• Est. Priority Date: 05/23/1995
• Status: Expired due to Fees

• Current Assignee: RealD Incorporated
• Original Assignee: ColorLink, Incorporated (RealD Incorporated)
• Inventors: Sharp, Gary D.
• Primary Examiner(s): Parker, Kenneth
• Application Number:
  US09/126,330
• Time in Patent Office: 2,454 Days
• Field of Search: 349/74, 349/78, 349/79, 349/80
• US Class Current: 349/78
• CPC Class Codes: G02B 27/288 Filters employing polarising elements, e.g. Lyot or Solc filters G02B5/3016 takes precedence
• CPC Class Codes: G02F 1/0136 for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation G02F1/0353 takes precedence
• CPC Class Codes: G02F 1/0322 Arrangements comprising two or more independently controlled crystals
• CPC Class Codes: G02F 1/09 based on magneto-optical elements, e.g. exhibiting Faraday effect
• CPC Class Codes: G02F 1/133533 Colour selective polarisers G02F1/1347 takes precedence
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133543 Cholesteric polarisers
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 1/13473 for wavelength filtering or for colour display without the use of colour mosaic filters
• CPC Class Codes: G02F 1/23 for the control of the colour G02F1/03 - G02F1/21 take precedence
• CPC Class Codes: G02F 2413/04 Number of plates greater than or equal to 4
• CPC Class Codes: G02F 2413/08 with a particular optical axis orientation
• CPC Class Codes: H04N 5/66 Transforming electric information into light information scanning details H04N3/00
• CPC Class Codes: H04N 5/7441 the modulator being an array of liquid crystal cells
• CPC Class Codes: H04N 9/3111 for displaying the colours sequentially, e.g. by using sequentially activated light sources sequential projection in colour photography G03B33/08
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

The present invention provides a high brightness color selective light modulator (CSLM) formed by a polarization modulator positioned between two retarder stacks. The modulator changes the apparent orientation of one retarder stack relative to the other so that, in a first switching state of the modulator the two retarder stacks cooperate in filtering the spectrum of input light, and in a second switching state the two retarder stacks complement each other, yielding a neutral transmission spectrum. Two or more CSLM stages can be used in series, each stage providing independent control of a primary color. One preferred embodiment eliminates internal polarizers between CSLM stages, thereby providing an additive common-path full-color display with only two neutral polarizers. Hybrid filters can be made using the CSLMs of this invention, in combination with other active or passive filters. The CSLMs of this invention can be used in many applications, particularly in the areas of recording and displaying color images. They can be arranged in a multi pixel array by pixelating the active elements, and can be implemented as color filter arrays, using patterned passive retarders rather than active polarization modulators.

Claims

1. A light modulator, comprising:

an input polarizer for receiving input light and outputting polarized light;

a first color selective polarization modulator for receiving said polarized light and for selectively modulating the polarization state of at least a first spectrum of said polarized light;

a second color selective polarization modulator for receiving light from said first color selective polarization modulator, and for selectively modulating the polarization state of at least a second spectrum of said polarized light; and

an output polarizer for receiving and analyzing the polarization states of said first and second spectrums, wherein the input polarizer, the color selective polarization modulators and the output polarizer are optically coupled.

2. A light modulator, comprising:

a retarder stack for receiving at least partially polarized light and outputting a first spectrum having a first polarization and a second spectrum having a second polarization; and

an electro-optic modulator and retarder combination optically coupled to the retarder stack and having an isotropic state and a modulation state, wherein the electro-optic modulator and retarder combination is adapted to selectively modulate input light that has a polarization state that corresponds to the modulation state of the electro-optic modulator and retarder combination, wherein one of the first and second polarizations correspond to the modulation state of the electro-optic modulator and retarder combination.

3. The light modulator of claim 2, wherein the first and second polarizations output by the retarder stack are linear polarizations.

4. The light modulator of claim 2, wherein the electro-optic modulator and retarder combination comprises a variable retarder in combination with a passive quarter-wave retarder.

5. The light modulator of claim 4, wherein the modulation state is a linear polarization state and the isotropic state is a circular polarization state.

48. The light modulator of claim 2, wherein the retarder stack comprises retarders welded together by chemical bonding.

49. The light modulator of claim 48, wherein the welded retarders are polycarbonate sheets.

50. The light modulator of claim 49, wherein the welded retarders are welded together using methylene chloride.

51. The light modulator of claim 50, wherein a dope is formed of polycarbonate dissolved in methylene chloride.

6. A sequencer, comprising:

a first modulator stage, comprising;

a first input retarder stack for receiving and transforming the polarization of light,

a first electro-optic modulator for receiving and selectively modulating the polarization of a portion of light output by the first retarder stack, and

a first output retarder stack for receiving and transforming the polarization of light output by the first electro-optic modulator;

a second modulator stage, comprising;

a second input retarder stack for receiving and transforming the polarization of light,

a second electro-optic modulator for receiving and selectively modulating the polarization of a portion of light output by the second retarder stack, and

a second output retarder stack for receiving and transforming the polarization of light output by the second electro-optic modulator; and

a third modulator stage, comprising;

a third input retarder stack for receiving and transforming the polarization of light,

a third electro-optic modulator for receiving and selectively modulating the polarization of a portion of light output by the third retarder stack, and

a third output retarder stack for receiving and transforming the polarization of light output by the third electro-optic modulator.

7. The sequencer of claim 6, wherein the first, second and third modulator stages function substantially independent of each other.

8. The sequencer of claim 6, wherein the first, second and third electro-optic modulators exhibit higher chromaticity in a stack-altered mode than in a stack-only mode.

9. The sequencer of claim 8, wherein the first, second and third modulator stages each exhibit a filtered state and a neutral state when their respective electro-optic modulators are in the stack-altered mode and the stack-only mode, respectively.

10. The sequencer of claim 9, wherein the neutral state is a black state.

11. The sequencer of claim 9, wherein the neutral spectrum is a white state.

12. The sequencer of claim 8, wherein the first, second and third modulator stages each exhibit a filtered state and a neutral state when their respective electro-optic modulators are in the stack-only mode and the stack-altered mode, respectively.

13. The sequencer of claim 12, wherein the neutral state is a black state.

14. The sequencer of claim 12, wherein the neutral state is a white state.

15. The sequencer of claim 6, wherein a state of each of the first, second and third modulator stages is switchable between one additive primary filtered state and a neutral state.

16. The sequencer of claim 15, wherein the state of the first, second and third modulator stages is switchable between red and black states, green and black states, and blue and black states, respectively.

17. The sequencer of claim 6, wherein a state of each of the first, second and third modulator stages is switchable between one subtractive primary filtered state and a neutral state.

18. The sequencer of claim 17, wherein the state of the first, second and third modulator stages is switchable between cyan and white states, magenta and white states, and yellow and white states, respectively.

19. The sequencer of claim 6, wherein a peak transmission of one of said first, second and third modulator stages is tunable so that its peak transmission coincides with a peak transmission of a respective filtered state.

20. The sequencer of claim 6, wherein the first, second and third electro-optic modulators exhibit higher chromaticity in a stack-only mode than in a stack-altered mode.

21. The sequencer of claim 20, wherein the first, second and third modulator stages each exhibit a filtered state and a neutral state when their respective electro-optic modulators are in the stack-altered mode and the stack-only mode, respectively.

22. The sequencer of claim 21, wherein the neutral state is a black state.

23. The sequencer of claim 21, wherein the neutral state is a white state.

24. The sequencer of claim 20, wherein the first, second and third modulator stages each exhibit a filtered state and a neutral state when their respective electro-optic modulators are in the stack-only mode and the stack-altered mode, respectively.

25. The sequencer of claim 24, wherein the neutral state is a black state.

26. The sequencer of claim 24, wherein the neutral state is a white state.

27. The sequencer of claim 6, wherein the first input retarder stack is an inverse of the first output retarder stack.

28. The sequencer of claim 6, wherein the second input retarder stack is an inverse of the second output retarder stack.

29. The sequencer of claim 6, wherein the third input retarder stack is an inverse of the third output retarder stack.

30. The sequencer of claim 6, wherein the first, second and third input retarder stacks are inverses of the first, second and third output retarder stacks, respectively.

31. The sequencer of claim 6, wherein the first, second and third modulator stages together exhibit a neutral state in the stack-altered mode.

32. The sequencer of claim 31, wherein the neutral state is a white state.

33. The sequencer of claim 31, wherein the neutral state is a black state.

34. The sequencer of claim 31, wherein the polarization of input light received by the first modulator stage and the polarization of light output by the first modulator stage are matched.

35. The sequencer of claim 34, wherein the polarization of the input light is an eigenpolarization of the first modulator stage in the stack-altered mode.

36. The sequencer of claim 6, further comprising an analyzing polarizer positioned and oriented to receive and analyze light from the first, second and third modulator stages.

37. The sequencer of claim 36, wherein the first, second and third modulator stages each modulate the transmission of a respective spectrum between substantially full transmission and substantially zero transmission.

52. The sequencer of claim 6, wherein at least one of the first input retarder stack, the second input retarder stack, the third input retarder stack, the first output retarder stack, the second output retarder stack, and the third output retarder stack comprises retarders welded together by chemical bonding.

53. The sequencer of claim 52, wherein the welded retarders are polycarbonate sheets.

54. The sequencer of claim 53, wherein the welded retarders are welded together using methylene chloride.

55. The sequencer of claim 54, wherein a dope is formed of polycarbonate dissolved in methylene chloride.

38. A multi-stage in-line color filter, comprising:

a first stage for modulating a first spectrum in accordance with a first signal;

a second stage for modulating a second spectrum in accordance with a second signal;

a third stage for modulating a third spectrum in accordance with a third signal, wherein at least one of the first, second and third stages comprises a first retarder stack, a second retarder stack and a modulator positioned between the first and second retarder stacks, and wherein the modulator has an isotropic state and a modulation state, and wherein the first retarder stack modulates a polarization state of its respective spectra so as to correspond to the modulation state of the modulator; and

an output polarizer.

39. The multi-stage in-line color filter of claim 38, wherein the first, second and third stages do not include any interposing polarizers.

40. The multi-stage in-line color filter of claim 39, wherein the first, second and third stages modulate the polarization of the first, second and third spectrums, respectively, in accordance with the first, second and third signals, respectively.

41. The multi-stage in-line color filter of claim 38, wherein the first, second and third stages modulate the transmittance of the first, second and third spectrums, respectively.

42. The multi-stage in-line color filter of claim 41, wherein the transmittance of the first, second and third spectrums is continuously variable in accordance with the first, second and third signals, respectively.

43. The multi-stage in-line color filter of claim 38, wherein the first, second and third stages are each variable saturation filters.

44. The multi-stage in-line color filter of claim 38, wherein the first, second and third stages are each variable luminance filters.

56. The multi-stage in-line color filter of claim 38, wherein at least one of the first stage, the second stage, and the third stage comprises a retarder stack, the retarder stack comprises retarders welded together by chemical bonding.

57. The multi-stage in-line color filter of claim 56, wherein the welded retarders are polycarbonate sheets.

58. The multi-stage in-line color filter of claim 57, wherein the welded retarders are welded together using methylene chloride.

59. The multi-stage in-line filter of claim 58, wherein a dope is formed of polycarbonate dissolved in methylene chloride.

45. A method of modulating light with a variable retarder using retarder stacks for transforming light into two linear polarization states with two spectra, comprising the steps of:

arranging a first retarder stack which yields a first and second linear polarization with first and second spectra;

arranging a retarder which transforms the second linear polarization into elliptical polarization; and

arranging a variable retarder to receive the elliptical polarization and the first polarization.

46. The method of claim 45, wherein the elliptical polarization is circular polarization, and the second polarization is linear polarization.

47. The method of claim 45, wherein the elliptical polarization is a modulation state for the variable retarder.

60. The method of claim 45, wherein the first retarder stack comprises retarders welded together by chemical bonding.

61. The method of claim 60, wherein the welded retarders are polycarbonate sheets.

62. The method of claim 61, wherein the welded retarders are welded together using methylene chloride.

63. The method of claim 62, wherein a dope is formed of polycarbonate dissolved in methylene chloride.

64. A multi-stage in-line color filter, comprising:

a first stage for modulating a first spectrum in accordance with a first signal;

a second stage for modulating a second spectrum in accordance with a second signal;

a third stage for modulating a third spectrum in accordance with a third signal wherein at least one of the first, second and third stages comprises a first retarder stack, a second retarder stack and a modulator positioned between the first and second retarder stacks, and wherein the first, second and third stages do not include any interposing polarizers; and

an output polarizer.