Light demodulator and method of communication employing the same
First Claim
1. A light modulator comprising at least one liquid crystal cell comprising two parallel transparent plates;
- a transparent electrical conductive layer applied to the confronting surfaces of the said two plates;
each said conductive layer having parallel surface alignment, the said alignment of the two adjoining surfaces being parallel;
a continuous layer of nematic liquid crystal having positive dielectric anisotropy between the two electrical conducting coatings;
means for applying a fixed electrical bias to the two said electrical conducting coatings;
means for applying an amplitude modulated oscillatory electrical signal having a frequency greater than 10 hertz across the said continuous layer;
a source of polarized light directed through the said two transparent plates;
whereby the light which passes through the said two transparent plates is a phase-shifted beam which is distinguishable from the light from the said source in a manner which corresponds to the said oscillatory electrical signal.
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Abstract
A light modulator for generating a beam of phase modulated light including a source of polarized light, at least one and preferably two liquid crystal cells having a thin layer of nematic liquid crystals of positive dielectric anistropy through which the polarized light is directed to produce a beam of light having a phase shift corresponding to a modulating electrical signal which is applied to each of the liquid crystal cells. The liquid crystal cells in addition have a continuing electrical bias applied across the layers in order to achieve the rapid response times necessary to achieve modulation of the polarized light. Demodulation of the polarized light occurs by splitting the modulated light beam into its quadrature components and developing an electrical signal corresponding to the phase difference between the two quadrature components. A communication system involving its modulators and demodulators delivers communication through light as a transmission medium.
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Citations
35 Claims
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1. A light modulator comprising at least one liquid crystal cell comprising two parallel transparent plates;
- a transparent electrical conductive layer applied to the confronting surfaces of the said two plates;
each said conductive layer having parallel surface alignment, the said alignment of the two adjoining surfaces being parallel;
a continuous layer of nematic liquid crystal having positive dielectric anisotropy between the two electrical conducting coatings;means for applying a fixed electrical bias to the two said electrical conducting coatings; means for applying an amplitude modulated oscillatory electrical signal having a frequency greater than 10 hertz across the said continuous layer; a source of polarized light directed through the said two transparent plates; whereby the light which passes through the said two transparent plates is a phase-shifted beam which is distinguishable from the light from the said source in a manner which corresponds to the said oscillatory electrical signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 28)
- a transparent electrical conductive layer applied to the confronting surfaces of the said two plates;
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26. A light modulator comprising three juxtaposed parallel spaced-apart transparent plates having a transparent electrically conductive coating over all confronting surfaces;
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a layer of nematic liquid crystal composition having positive dielectric anisotropy in the space between confronting surfaces of said plates;
parallel a polarizing plate juxtaposed and parallel to said plates;said three plates and said polarizing plate being secured in fixed relation;
means for applying a fixed electrical bias to the confronting coatings;means for applying an amplitude modulated oscillatory electrical signal across each said layer of the nematic liquid crystal composition; said modulator being adapted to develop a phase shift in a beam of light passing through the said modulator from the said polarizing plate and thence through the said layer of nematic liquid crystal composition. - View Dependent Claims (27)
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31. Iadd.44. A method for controlling polarized light comprising:
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(a) establishing a film of nematic liquid crystal having positive dielectric anisotropy between two parallel surfaces and imparting a first generally parallel surface orientation to the said liquid crystal film at the said surfaces; (b) establishing a second generally parallel bulk orientation of the bulk of the liquid crystal in a direction which is different from the said first generally parallel surface orientation of the liquid crystal at the said surfaces; (c) applying a varying electrical signal to said surfaces to change the alignment of the liquid crystal between the said surface orientation and the said bulk orientation; (d) passing polarized light through said film to generate light which is phase shifted in a manner corresponding to the said varying electrical signal. .Iaddend. .Iadd.45. In the method for controlling polarized light according to claim 44, maintaining the direction of orientation of the bulk of the liquid crystal generally perpendicular to the said surfaces of
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- 32. the film. .Iaddend. .Iadd.46. The method of claim 44 wherein the phase-shifted light corresponds to a separation of separate color components of a light source. .Iaddend. .Iadd.47. The method of claim 46 wherein the said phase-shifted light corresponds to green light components from a light source. .Iaddend. .Iadd.48. The method of claim 46 wherein the said phase-shifted light corresponds to red light components from a light source. .Iaddend. .Iadd.49. The method of claim 46 wherein the said phase-shifted light corresponds to yellow light components from a light
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33. source. .Iaddend. .Iadd.50. The method of claim 44 wherein each of the said spaced-apart films is established between transparent conducting electrodes. .Iaddend. .Iadd.51. The method of claim 50 wherein the said transparent conducting electrodes are formed predominantly from oxides of metals selected from the class consisting of tin and indium. .Iaddend. .Iadd.52. A method for controlling polarized light comprising:
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(a) establishing two spaced apart films of nematic liquid crystal having positive dielectric anisotropy, each said film contained between two parallel surfaces;
imparting a generally parallel alignment of each liquid crystal film at its surfaces;(b) applying a varying electrical signal to the said surface of each said film to align the direction of each liquid crystal film at its surfaces in directions which are different from the orientation of the bulk of each liquid crystal film; (c) passing polarized light through each said film in sequence to generate light which is phase shifted in a manner corresponding to the said varying electrical signals, wherein the resultant phase shift of the two said films corresponds to the vector summation of the phase shift resulting
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34. from each of the said two spaced apart film. .Iaddend. .Iadd.53. In the method of claim 52 applying a said electrical signal applied to one of said films which is opposite in phase to the electrical signal applied to the other of said films. .Iaddend. .Iadd.54. In the method of claim 52 including the step of converting the phase-shifted light to a corresponding amplitude-modulated signal. .Iaddend. .Iadd.55. The method of claim 54 wherein the said phase-shifted light is converted in a polarizing filter. .Iaddend. .Iadd.56. The method of claim 54 wherein the said step of converting the phase shifted light develops a fully amplitude-modulated signal. .Iaddend. .Iadd.57. The method of claim 52 wherein the said amplitude-modulated light corresponds to a separation of separate color components of a light source. .Iaddend. .Iadd.58. The method of claim 52 including the step of separately modulating the red components and the green components of the said light source. .Iaddend.
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35. Iadd.59. A method for controlling polarized light comprising:
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(a) establishing a film of nematic liquid crystal having positve dielectric anisotropy between two parallel surfaces and imparting a first generally parallel surface orientation to the said liquid crystal film at the said surfaces; (b) establishing a second bulk orientation of the bulk of the liquid crystal in a direction which is different from the said first generally parallel orientation of the liquid crystal at the said surfaces; (c) altering the relative direction of the alignment of the liquid crystal between the said surface orientation and the said bulk orientation; (d) whereby the phase shifting property of the film corresponds to the said relative direction. .Iaddend.
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Specification