Enhanced ZScreen modulator techniques

• US 20070258138A1
• Filed: 05/08/2006
• Published: 11/08/2007
• Est. Priority Date: 12/06/2005
• Status: Active Grant

• Current Assignee: RealD Incorporated
• Original Assignee: Real D
• Inventors: Greer, Josh, Lipton, Lenny, Cowan, Matt, Chiu, Joseph
• Granted Patent: US 7,477,206 B2
• Time in Patent Office: Days
• US Class Current: 359/443
• CPC Class Codes: G02F 1/0136 for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation G02F1/0353 takes precedence
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/13471 in which all the liquid crystal cells or layers remain transparent, e.g. FLC, ECB, DAP, HAN, TN, STN, SBE-LC cells G02F1/13475 takes precedence
• CPC Class Codes: G03B 21/56 Projection screens
• CPC Class Codes: H04N 13/341 using temporal multiplexing
• CPC Class Codes: H04N 13/363 using image projection screens volumetric display H04N13/388

Abstract

A method and system for use in conjunction with a push-pull liquid crystal modulator system for creating circularly polarized light of alternating handedness is provided. The method and system comprise a pair of surface mode liquid crystal cells and a driver electrically coupled to the cells. The driver is configured to move an electrical charge using a quenching pulse comprising a relatively brief voltage spike at a beginning of a waveform period. Multiple additional improvements are provided, including reducing the thickness of the LC gap (the distance between cell electrode plates), creating a charge connection or wiring connection to the cell electrodes, employing anti-reflection coating technology, thinner ITO and ITO index matched to the LC material, bonding all possible air to material surfaces, using superior glass, employing more efficient polarizers, and reducing projector blanking time.

Claims

1. In a push-pull liquid crystal modulator system for creating circularly polarized light of alternating handedness comprising (a) a pair of surface mode liquid crystal cells having orthogonal rub axes;

(b) a linear polarizer having an absorption axis bisecting the orthogonal rub axes; and

(c) a driver electrically coupled to the cells, and capable of driving the cells so that when one cell in the pair is in a higher voltage state, the other cell in the pair is in a lower voltage state, an improvement comprising;

drive circuitry within the driver causing the driver to move an electrical charge using a quenching pulse comprising a relatively brief voltage spike at a beginning of a waveform period.

2. The system of claim 1, wherein the push-pull liquid crystal modulator comprises a layer of ITO (Indium Tin Oxide), further comprising:

an antireflective coating provided to at least one optical interface in the push-pull liquid crystal modulator;

an index matching layer applied to the layer of ITO; and

an electronic projector employed with the push-pull liquid crystal modulator.

3. The system of claim 2, wherein the push-pull liquid modulator comprises a dyestuff polarizer.

4. The system of claim 1, wherein the push-pull liquid crystal modulator comprises an ITO (Indium Tin Oxide) film having resistivity of approximately 300 ohms per square.

5. The system of claim 1, further comprising a fan used to cool said push-pull liquid crystal modulator.

6. The system of claim 2, wherein the push-pull liquid crystal modulator has air to material surfaces bonded.

7. The system of claim 1, wherein liquid crystal used in the push-pull liquid crystal modulator comprises water clear Borofloat.

8. In a stereoscopic video display apparatus, comprising a push-pull liquid crystal modulator including a pair of surface mode liquid crystal cells having orthogonal rub axes and a linear polarizer having an absorption axis bisecting the orthogonal rub axes, and configured to sequentially transmit left-hand circularly polarized light comprising the image and right-hand circularly polarized light comprising a field sequential stereo image, the push-pull liquid crystal modulator comprising a layer of ITO (Indium Tin Oxide), an improvement comprising:

an antireflective coating provided to at least one optical interface in the push-pull liquid crystal modulator;

an index matching layer applied to the layer of ITO; and

an electronic projector employed with the push-pull liquid crystal modulator.

9. The apparatus of claim 8, wherein the system further comprises a driver electrically coupled to the cells, capable of driving the cells so that when one cell in the pair is in a higher voltage state, the other cell in the pair is in a lower voltage state, the system further comprising:

drive circuitry within the driver causing the driver to move an electrical charge using a quenching pulse comprising a relatively brief voltage spike at a beginning of a waveform period.

10. The apparatus of claim 9, wherein the push-pull liquid modulator comprises a dyestuff polarizer.

11. The apparatus of claim 9, wherein the ITO layer comprises a film having resistivity of approximately 300 ohms per square.

12. The apparatus of claim 9, further comprising a fan used to cool said push-pull liquid crystal modulator.

13. The apparatus of claim 9, wherein the push-pull liquid crystal modulator has air to material surfaces bonded.

14. The apparatus of claim 9, wherein liquid crystal used in the push-pull liquid crystal modulator comprises water clear Borofloat.

15. A method of displaying a stereoscopic video image, comprising:

positioning a push-pull liquid crystal modulator that includes a pair of surface mode liquid crystal cells with orthogonal rub axes and a linear polarizer having an absorption axis bisecting the orthogonal rub axes, so that light comprising the image propagates therethrough; and

driving the modulator in synchronization with fields of a field sequential image so that the transmitted image emerging from the modulator consists of right-handed circularly polarized fields alternating at the field rate with left-handed circularly polarized fields;

wherein said driving comprises moving an electrical charge using a waveform comprising at least one quenching pulse comprising a relatively brief voltage spike at a beginning of a waveform period.

16. The method of claim 15, further comprising positioning a left-handed circular polarizer analyzer and a right-handed circular polarizer analyzer so that circularly polarized light emerging from the modulator propagates through space and is reflected by a polarizing conserving screen through space and then through one circular polarizer analyzer while being blocked by a complementary circular polarizer analyzer.

17. The method of claim 15, wherein the modulator comprises a first surface mode liquid crystal cell and a second surface mode liquid crystal cell, and wherein the first cell is driven by a first voltage signal that alternates at field rate between a low voltage square wave and a high voltage square wave, and the second cell is driven by a second voltage signal having substantially the same amplitude as the first voltage signal but having phase opposite to the first signal'"'"'s phase.

18. The method of claim 15, wherein each field includes at least two subfields, each subfield having a duration, the modulator includes a first surface mode liquid crystal cell and a second surface mode liquid crystal cell, and including the steps of:

driving the first cell with a first voltage signal; and

driving the second cell with a second voltage signal, in such a manner that the absolute magnitude of the envelope of the first voltage signal and the absolute magnitude of the envelope of the second voltage signal decrease substantially simultaneously during each subfield.

19. The system of claim 15, wherein each field includes at least two subfields, and each subfield having a duration, the modulator includes a first surface mode liquid crystal cell and a second surface mode liquid crystal cell, and comprising:

driving the first cell with a first carrier-less voltage signal; and

driving the second cell with a second carrier-less voltage signal, in such a manner that the absolute magnitude of the first voltage signal and the absolute magnitude of the second voltage signal decrease substantially simultaneously during each subfield.

20. The method of claim 15, wherein the modulator includes a first surface mode liquid crystal cell and a second surface mode liquid crystal cell, and wherein the first cell is driven by a first voltage signal that alternates at field rate between a low AC voltage portion and a high AC voltage portion, and the second cell is driven by a second voltage signal having substantially the same amplitude as the first voltage signal but having phase opposite to the first signal'"'"'s phase.

21. The method of claim 20, wherein each of the AC voltage portions is a 2 KHz sinusoidal wave, the low AC voltage portion has peak to peak amplitude in the range from zero volts to ten volts, and the high AC voltage portion has peak to peak amplitude in the range from 40 volts to 80 volts.

22. The method of claim 15, wherein the push-pull liquid modulator comprises a dyestuff polarizer.

23. The method of claim 15, wherein the push-pull liquid crystal modulator has air to material surfaces bonded.

24. The method of claim 15, wherein liquid crystal used in the push-pull liquid crystal modulator comprises water clear Borofloat.

25. The method of claim 15, wherein the push-pull liquid crystal modulator is employed in connection with a screen, and persons viewing the screen employ eyewear comprising polarizing elements matched to the push-pull liquid crystal modulator.