Contrast polymer dispersed liquid crystal projection display system

• US 6,243,152 B1
• Filed: 12/17/1996
• Issued: 06/05/2001
• Est. Priority Date: 12/17/1996
• Status: Expired due to Fees

• Current Assignee: Duke University
• Original Assignee: Duke University
• Inventors: Zeinali, Mehdi, Knox, Richard M.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): TON, MINH TOAN T
• Application Number:
  US08/773,794
• Time in Patent Office: 1,631 Days
• Field of Search: 349/8, 349/10, 349/86, 349/96, 349/9
• US Class Current: 349/86
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: H04N 5/7441 the modulator being an array of liquid crystal cells
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

A polymer dispersed liquid crystal projection display is provided that has enhanced contrast. In the projection system using a polymer dispersed liquid crystal display (PDLC), polarized light is used as the light source onto the PDLC. The reflected light maintains its polarization, while the scattered light from the off pixels of the PDLC randomize the polarization. The polarized image is then passed through a polarizing filter which eliminates half of the scattered light, whereas practically all of the polarized image is passed onto the display source. In this way, the contrast between the on and off pixels is effectively doubled.

Claims

1. A projection display engine comprising:

a light source;

a filter adapted to selectively direct light derived from the light source as polarized light, the polarized light comprising one of certain polarization and certain other polarization;

a polymer dispersed liquid crystal display adapted to receive one of the certain polarization and the certain other polarization and to return a polarized image in one of the certain polarization and the certain other polarization, the polarized image being directed as an image to be displayed, some light scattered by the polymer dispersed liquid crystal being blocked from being in the image to be displayed; and

a polarization specific reflector disposed in a path of the polarized image and adapted to direct the certain polarization along a first direction and the certain other polarization along a second direction.

2. The projection display engine of claim 1, wherein the polarization specific reflector is adapted to provide the polarized light for imaging.

3. The projection display engine of claim 1, wherein the light source comprises a lamp, and wherein the polarization specific reflector is disposed between the lamp and the polymer dispersed liquid crystal display, the polarization specific reflector adapted to direct the polarized light for imaging.

4. The projection display engine of claim 1, wherein the filter comprises a polarization specific reflecting polarizer.

5. The projection display engine of claim 1, wherein the light source further comprises a lamp adapted to provide the light derived from the light source, wherein the light derived from the light source is divided into the polarized light and other light.

6. The projection display engine of claim 1, further comprising a retarder disposed between the light source and the polymer dispersed liquid crystal display, the retarder adapted to rotate polarization of the polarized image.

7. The projection display engine of claim 1, wherein the polarization specific reflector transmits the polarized light to the polymer dispersed liquid crystal display, and wherein the polarization specific reflector reflects the polarized image.

8. The projection display engine of claim 1, wherein the polarization specific reflector enhances contrast of the image.

9. The projection display engine of claim 1, wherein the filter comprises a polarizer.

10. A projection system comprising:

a light source;

a filter adapted to selectively direct light derived from the light source as polarized light, the polarized light comprising one of certain polarization and certain other polarization;

a polymer dispersed liquid crystal display adapted to receive one of the certain polarization and the certain other polarization and to return a polarized image in one of the certain polarization and the certain other polarization, the polarized image being directed as an image to be displayed, some light scattered by the polymer dispersed liquid crystal being blocked from being in the image to be displayed;

a polarization specific reflector disposed in a path of the polarized image and adapted to direct the certain polarization along a first direction and the certain other polarization along a second direction;

a controller adapted to receive video data, the controller coupled to the polymer dispersed liquid crystal display to provide the image; and

a display screen for receiving the image.

11. The projection system of claim 10, wherein the light source comprises a lamp.

12. The projection system of claim 11, wherein the polarization specific reflector is disposed between the lamp and the polymer dispersed liquid crystal display.

13. A method of enhancing the contrast in a display system, the method comprising:

selectively directing light derived from a light source as polarized light in one of certain polarization and certain other polarization;

directing the polarized light to a polymer dispersed liquid crystal display, the polymer dispersed liquid crystal display receiving one of the certain polarization and the certain other polarization;

returning a polarized image in one of the certain polarization and the certain other polarization from the polymer dispersed liquid crystal display, some light scattered by the polymer dispersed liquid crystal blocked from being in the polarized image; and

passing the polarized image to a polarization specific reflector for directing the certain polarization along a first direction and the certain other polarization along a second direction.

14. The method of claim 13, further comprising directing the polarized image to a projection surface.

15. The method of claim 13, further comprising providing a lamp for providing the light derived from the light source and disposing the polarization specific reflector between the lamp and the polymer dispersed liquid crystal display.

16. A projection display engine comprising:

a light source;

a polarization specific reflector adapted to reflect certain polarization of light derived from the light source;

a polymer dispersed liquid crystal display adapted to receive a portion of the light derived from the light source and to return a polarized image, all the light for imaging by the polymer dispersed liquid crystal display having the same relative polarization from the polarization specific reflector to the polymer dispersed liquid crystal display; and

a filter adapted to selectively direct polarized light from the light derived from the light source,

wherein some light scattered by the polymer dispersed liquid crystal display is blocked.

17. The projection display engine of claim 16, wherein the polarization specific reflector comprises a reflecting polarizer.

18. The projection display engine of claim 16, wherein the light source comprises a lamp adapted to provide the light derived from the light source, wherein the light derived from the light source is divided into the polarized light and other light.

19. The projection display engine of claim 16, wherein the polarization specific reflector directs the polarized light to the polymer dispersed liquid crystal display.

20. The projection display engine of claim 16, wherein the polarization specific reflector transmits the polarized light to the polymer dispersed liquid crystal display.

21. The projection display engine of claim 16, further comprising a retarder disposed between the light source and the polymer dispersed liquid crystal display, the retarder adapted to rotate polarization of the polarized image.

22. The projection display engine of claim 16, wherein the polarization specific reflector transmits the polarized light to the polymer dispersed liquid crystal display, and wherein the polarization specific reflector reflects the polarized image.

23. The projection display engine of claim 16, wherein the filter comprises a reflecting polarizer.

24. The projection display engine of claim 16, wherein the filter comprises a polarizer.

25. A method of enhancing contrast in a display system, the method comprising:

providing polarized light from a light source having a polarization specific reflector that reflects certain polarization;

directing the polarized light to a polymer dispersed liquid crystal display;

reflecting, in a single pass by the polarization specific reflector, all the polarized light for imaging by the polymer dispersed liquid crystal display;

returning a polarized image from the polymer dispersed liquid crystal display; and

passing the polarized light through a polarization selective filter to filter out light polarizations other than the polarization meant for the polarized image.

26. The method of claim 25, further comprising directing the polarized image to a projection surface.

27. The method of claim 25, wherein the reflecting comprises reflecting before the polymer dispersed liquid crystal display.

28. The method of claim 25, wherein the reflecting comprises reflecting after the polymer dispersed liquid crystal display.

29. The method of claim 25, wherein the passing comprises passing before the polymer dispersed liquid crystal display.

30. The method of claim 25, wherein the passing comprises passing after the polymer dispersed liquid crystal display.