Method and apparatus for converting phase-modulated light to amplitude-modulated light and communication method and apparatus employing the same

Claim 1

A light transmitter 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 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; and a linear polarizer for converting said phase-shifted beam to a light beam whose amplitude corresponds to said oscillatory electrical signal.

Claim 12

A method for generating amplitude-modulated light corresponding to a first oscillatory electrical signal comprising: polarizing light from a light source in a first linear polarizer to generate a first polarized light beam; passing said polarized light beam through an electrically biased, liquid crystal cell to develop a phase-modulated light beam; applying an electrical bias to the said electrically biased, liquid crystal cell; applying said first oscillatory electrical signal modulated with a carrier wave to said first electrically biased, liquid crystal cell whereby the said phase-modulated light corresponds to the said first oscillatory electrical signal; passing the said phase-modulated light through a second linear polarizer to convert the said phase-modulated light to amplitude-modulated light.

Claim 13

A method for generating amplitude-modulated light corresponding to a first oscillatory electrical signal comprising: polarizing light from a light source in a first linear polarizer to generate a first polarized light beam; passing said polarized light beam through an electrically biased, liquid crystal cell to develop a phase-modulated light beam; applying an electrical bias to the said electrically biased, liquid crystal cell; applying said first oscillatory electrical signal modulated with a carrier wave to said first electrically biased, liquid crystal cell whereby the said phase-modulated light corresponds to the said first oscillatory electrical signal; passing the said phase-modulated light through a second linear polarizer to convert the said phase-modulated light to amplitude-modulated light.

Claim 14

The method of delivering a first electrical signal of varying amplitude from a transmitter station to a receiving station which comprises generating in said transmitter station a phase-modulated light beam corresponding to said first electrical signal of varying amplitude by the following means; directing a beam of linearly polarized light through a liquid crystal cell formed from two parallel transparent plates and having a transparent electric conductive layer applied to the confronting surfaces of the said two plates wherein each said conductive layer has parallel surface alignment and wherein the alignment of the two adjoining surfaces is parallel and having a continuous layer of nematic liquid crystal with positive dielectric anisotropy between the two said electrical conductor coatings; applying an electrical bias to the two said electrical conducting coatings; applying said electrical signal of varying amplitude having a frequency greater than 10 hertz to the said electrical conducting coatings; whereby the said phase modulated light beam is distinguishable from the said polarized light source in manner which corresponds to the said electrical signal of varying amplitude; delivering said phase-modulated light to said receiving station including a light detector for generating an electrical signal corresponding to an amplitude-modulated light; a demodulator for demodulating the said electrical signal from the said light detector to generate a second electrical signal of varying amplitude corresponding to said first electrical signal of varying amplitude; interposing a linear polarizer in the optical path of said phase-modulated light beam between said transmitter station and said receiving station.

Claim 15

The method of delivering a first electrical signal of varying amplitude from a transmitter station to a receiving station which comprises generating in said transmitter station a phase-modulated light beam corresponding to said first electrical signal of varying amplitude by the following means; directing a beam of linearly polarized light through a liquid crystal cell formed from two parallel transparent plates and having a transparent electric conductive layer applied to the confronting surfaces of the said two plates wherein each said conductive layer has parallel surface alignment and wherein the alignment of the two adjoining surfaces is parallel and having a continuous layer of nematic liquid crystal with positive dielectric anisotropy between the two said electrical conductor coatings; applying an electrical bias to the two said electrical conducting coatings; applying said electrical signal of varying amplitude having a frequency greater than 10 hertz to the said electrical conducting coatings; whereby the said phase modulated light beam is distinguishable from the said polarized light source in manner which corresponds to the said electrical signal of varying amplitude; delivering said phase-modulated light to said receiving station including a light detector for generating an electrical signal corresponding to an amplitude-modulated light; a demodulator for demodulating the said electrical signal from the said light detector to generate a second electrical signal of varying amplitude corresponding to said first electrical signal of varying amplitude; interposing a linear polarizer in the optical path of said phase-modulated light beam between said transmitter station and said receiving station.

Claim 23

The method of modulating light at high speeds comprising: passing said light through a film of nematic liquid crystals having positive anisotropy, applying an electrical signal of varying amplitude to the surfaces of said film to alter the alignment of the said liquid crystals of at least one said surface, thereby altering the polarization property of said film; and delivering from said film the said light which is modulated in accordance with the said electrical signal.

Claim 24

The method of modulating light at high speeds comprising: passing said light through a film of nematic liquid crystals having positive anisotropy, applying an electrical signal of varying amplitude to the surfaces of said film to alter the alignment of the said liquid crystals of at least one said surface, thereby altering the polarization property of said film; and delivering from said film the said light which is modulated in accordance with the said electrical signal.

Claim 25

An apparatus for modulating light comprising means for polarizing incident light; 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 conductive coatings; means for applying an electrical bias to the two said electrical conductive coatings; means for applying an electrical signal of varying amplitude to the said electrical conductive coatings; whereby the said nematic liquid crystal is affected by said electrical signal solely at the interfacing surface with at least one of said electrical conducting coatings, thereby permitting rapid response of the said nematic liquid crystal layer to the applied electrical signal having frequencies of 10 hertz to 500 kilohertz; 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 said source in a manner which corresponds to the said electrical signal.

Claim 26

An apparatus for modulating light comprising means for polarizing incident light; 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 conductive coatings; means for applying an electrical bias to the two said electrical conductive coatings; means for applying an electrical signal of varying amplitude to the said electrical conductive coatings; whereby the said nematic liquid crystal is affected by said electrical signal solely at the interfacing surface with at least one of said electrical conducting coatings, thereby permitting rapid response of the said nematic liquid crystal layer to the applied electrical signal having frequencies of 10 hertz to 500 kilohertz; 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 said source in a manner which corresponds to the said electrical signal.

Claim 27

A method for generating intensity modulated light corresponding to a first electrical signal of varying amplitude comprising: passing polarized light through a liquid crystal film containing nematic liquid crystals having positive anisotropy; orienting the liquid crystal structure perpendicular to said film; applying said first electrical signal of varying amplitude to a surface of said liquid crystal film in its oriented condition, whereby light leaving said liquid crystal film corresponds in phase to the said first electrical signal; polarizing the leaving light to convert the output light to intensity modulated light.

Claim 28

A method for generating intensity modulated light corresponding to a first electrical signal of varying amplitude comprising: passing polarized light through a liquid crystal film containing nematic liquid crystals having positive anisotropy; orienting the liquid crystal structure perpendicular to said film; applying said first electrical signal of varying amplitude to a surface of said liquid crystal film in its oriented condition, whereby light leaving said liquid crystal film corresponds in phase to the said first electrical signal; polarizing the leaving light to convert the output light to intensity modulated light.