System and method for varying the transmittance of light through a media

• US 20020008708A1
• Filed: 05/18/2001
• Published: 01/24/2002
• Est. Priority Date: 05/21/2000
• Status: Active Grant

• Current Assignee: ELOP Electro-Optics Industries Limited
• Original Assignee: ELOP Electro-Optics Industries Limited
• Inventors: Weiss, Victor, Orion, Uzi
• Granted Patent: US 6,762,801 B2
• Time in Patent Office: Days
• US Class Current: 345/597
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 26/004 based on a displacement or a deformation of a fluid
• CPC Class Codes: G02B 27/01 Head-up displays
• CPC Class Codes: G02B 27/017 Head mounted
• CPC Class Codes: G02B 5/223 containing organic substances, e.g. dyes, inks or pigments
• CPC Class Codes: G02F 1/13318 Circuits comprising a photodetector

Abstract

The invention provides a system for varying the transmittance of light through selected portions of a media on which images are displayed, the system including an image display panel, an image display source for projecting images on the media, LC-based, variable transmittance optical (VTO) media, a light sensor for measuring ambient light, and a signal generator connected to the VTO media for applying voltage to portions of the media at levels determined and controlled by the sensor, whereby the transmittance of light through the portions of the media is varied in accordance with the prevailing ambient light. A method is also provided.

Claims

1. A system for varying the transmittance of light through selected portions of a media on which images are displayed, said system comprising:

an image display panel;

an image display source for projecting images on said media;

LC-based, variable transmittance optical (VTO) media;

a light sensor for measuring ambient light, and

a signal generator connected to said VTO media for applying voltage to portions of said media at levels determined and controlled by said sensor,

whereby the transmittance of light through said portions of said media is varied in accordance with the prevailing ambient light.

2. The system as claimed in claim 1, wherein said image display panel is an optical combiner.

3. The system as claimed in claim 1, wherein said panel is a window or a visor.

4. The system as claimed in claim 1, wherein said media is positioned at least in close proximity to said panel.

5. The system as claimed in claim 1, wherein said LC-based VTO media is a polarizer-free media.

6. The system as claimed in claim 1, wherein said LC-based VTO media is a guest-host LC (GHLC).

7. The system as claimed in claim 6, wherein said GHLC incorporates dichroic or pleochroic dyes mixed into said LC.

8. The system as claimed in claim 6, wherein said GHLC is selected from the group of GHLC droplet or GHLC microdomain phases embedded in polymer matrices.

9. The system as claimed in claim 6, wherein said GHLC comprises LC substances in the form of a phase selected from the group consisting of nematic, twisted nematic, supertwisted nematic, cholesteric, smectic phases, and combinations thereof.

10. The system as claimed in claim 1, wherein said LC media are contained within one electrical cell.

11. The system as claimed in claim 1, wherein said LC media are contained within at least two mutually orthogonally oriented, stacked electrical cells.

12. A guest-host liquid crystal (GHLC) media, whenever utilizable in a system for varying the transmittance of light in accordance with the prevailing ambient light.

13. The GHLC media as claimed in claim 12, wherein said GHLC incorporates dichroic or pleochroic dyes mixed into said LC.

14. The GHLC media as claimed in claim 12, wherein said GHLC is selected from the group of GHLC droplet or GHLC microdomain phases embedded in polymer matrices.

15. The GHLC media as claimed in claim 12, wherein said GHLC comprises LC substances in the form of a phase selected from the group consisting of nematic, twisted nematic, supertwisted nematic, cholesteric, smectic phases, and combinations thereof.

16. A method for varying the transmittance of light through selected portions of a media on which images are displayed, said method comprising:

providing an image display panel;

providing a guest-host liquid crystal (GHLC) media, and

applying voltages of selected levels to said portions of said GHLC media, depending on the prevailing ambient light, to effect changes in the transmittance of light through said portions of the media.

17. The method as claimed in claim 16, wherein the levels of voltage applied to said GHLC media are determined and controlled by a light sensor.

18. The method as claimed in claim 16, wherein said GHLC media comprises material of small birefringence with an average LC index close to the surrounding polymer phase.

19. The method as claimed in claim 16, wherein the LC phase of said GHLC media consists of randomly dispersed and oriented microphases embedded in polymer matrices.

20. The method as claimed in claim 16, wherein the GHLC phase consists of a homogeneous GHLC phase derived from the LC materials and phases, and other phases.

21. The method as claimed in claim 19, wherein said microphases are constituted by droplets or microdomains having a size significantly smaller than the wavelength of the interacting light so as to achieve negligible light scattering.