Electron addressed liquid crystal light valve

• US 4,387,964 A
• Filed: 10/21/1980
• Issued: 06/14/1983
• Est. Priority Date: 10/21/1980
• Status: Expired due to Term

• Current Assignee: Mcdonnell Douglas Corporation (The Boeing Co.)
• Original Assignee: Mcdonnell Douglas Corporation (The Boeing Co.)
• Inventors: Dillard, Homer E., Brown, Raymond E., Arrazola, Ignacio M.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Gallivan, Richard F.
• Application Number:
  US06/199,292
• Time in Patent Office: 966 Days
• Field of Search: 350/331 R, 350/334, 350/337, 350/338, 350/345, 350/351
• US Class Current: 349/31
• CPC Class Codes: G02F 1/133348 Charged particles addressed liquid crystal cells, e.g. controlled by an electron beam

Abstract

This light modulating device comprises three subsystems: an electron gun which produces a scanning constant intensity electron beam, a liquid crystal cell, and an appropriate optical system to deliver light to and from the modulating effects of the liquid crystal cell. The modulation is accomplished by utilizing a scanning constant intensity electron beam to deposit electrical charge through a secondary emission process on the dark side of a dielectric mirror within the liquid crystal cell, the amount of charge deposited being dependent upon the video voltage at the transparent electrode of the cell which is applied in synchronism with the scanning electron beam. In this manner a charge distribution is written on the back of the dielectric mirror which now contains all of the information within the video signal. The electrical field arising from this charge distribution in turn modulates the birefringence across the nematic phase liquid crystal. Under appropriate electrical field conditions, the "twisted" nematic phase liquid crystal cell will reflect incident plane polarized light as eliptically polarized light constituting an "ON" state. This elliptically polarized light is then projected through an appropriate analyzer and on through further relay optics. In the "OFF" state incident plane polarized light is reflected from the cell as linearly polarized light and is blocked by the analyzer.

Claims

1. A light valve comprising:

means for producing a focused scanning electron beam;

a liquid crystal cell comprising;

a liquid crystal disposed between two parallel alignment surfaces, the alignment of one such surface being rotated relative to the other such surface,

a thin optical flat having one surface as one of said alignment sufaces and the other surface as a dielectric mirror such that the dielectric mirror faces the electron beam producing means;

a thin film of insulating material serving as the second alignment surface

a transparent electrode disposed adjacent to the thin film of insulating material, and

a faceplate disposed adjacent the transparent electrode;

an effectively electron-transparent electrode comprising a fine conducting mesh disposed parallel to and spaced from about one to about 50 microns from the dielectric mirror; and

circuit means to apply a video signal between the transparent electrode and the electron transparent electrode in synchronization with the electron beam producing means.

2. The light valve of claim 1 further comprising a housing means suitable for maintaining the elements of the light valve in an evacuated environment.

3. The light valve of claim 1 wherein the one alignment surface is rotated approximately 45°

relative to the other alignment surface.

4. The light valve of claim 1 wherein the liquid crystal comprises a nematic phase liquid crystal.

5. A light modulation system comprising:

a light source optically linked to a first polarizing filter which transmits plane polarized light from the light source onto an electron-addressed liquid crystal light valve, said plane polarized light entering into the light valve, being reflected therefrom, and finally transmitted through a second polarizing filter the plane of polarization of which is rotated about 90°

relative to the plane of polarization of the first polarizing filter wherein the light valve comprises;

a liquid crystal disposed between two parallel alignment surfaces, the alignment of one such surface being rotated relative to the other such surface;

a thin optical flat having one surface as one of said alignment surfaces and the other surface as a dielectric mirror such that the dielectric mirror faces the electron beam producing means;

a thin film of insulating material serving as the second alignment surface;

a transparent electrode disposed adjacent to the thin film of insulating material; and

a faceplate disposed adjacent the transparent electrode;

an effectively electron-transparent electrode comprising a fine conducting mesh disposed parallel to and spaced from about one to about 50 microns from the dielectric mirror; and

a circuit means to apply a video signal between the transparent electrode and the electron transparent electrode in synchronization with the electron beam producing means.

7. The system of claim 5 or claim 6 wherein the finally transmitted light is optically connected to projection optics means.

8. The system of claim 5 or claim 6 wherein the light valve further comprises a housing means suitable for maintaining the elements of the light valve in an evacuated environment.

9. The system of claim 5 or claim 6 wherein the light valve is constructed such that one alignment surface is rotated approximately 45°

relative to the other alignment surface.

10. The system of claim 5 or claim 6 wherein the light valve is constructed such that the liquid crystal comprises a nematic phase liquid crystal.

6. A light modulation system comprising:

a light source optically linked to a polarizing beam splitter means which transmits plain polarized light on to an electron addressed liquid crystal light valve;

said plain polarized light entering into the light valve, being reflected therefrom, and finally transmitted from the polarizing beam splitter wherein the light valve comprises;

a liquid crystal disposed between two parallel alignment surfaces, the alignment of one such surface being rotated relative to the other such surface;

a thin optical flat having one surface as one of said alignment surfaces and the other surface as a dielectric mirror such that the dielectric mirror faces the electron beam producing means;

a thin film of insulating material serving as the second alignment surface;

a transparent electrode disposed adjacent to the thin film of insulating material; and

a faceplate disposed adjacent to the transparent electrode;

an effective electron-transparent electrode comprising a fine conducting mesh disposed parallel to and spaced from about one to about 50 microns from the dielectric mirror; and

a circuit means to apply a video signal between the transparent electrode and the electron transparent electrode in synchronization with the electron beam producing means.