Liquid crystal variable drive voltage

• US 8,786,529 B1
• Filed: 05/18/2011
• Issued: 07/22/2014
• Est. Priority Date: 05/18/2011
• Status: Active Grant

• Current Assignee: zSpace Inc.
• Original Assignee: zSpace Inc.
• Inventors: Chavez, David A., Flynn, Mark F., Cheponis, Michael A.
• Primary Examiner(s): Sitta, Grant
• Application Number:
  US13/110,562
• Time in Patent Office: 1,161 Days
• Field of Search: 345/87, 345/204, 345/102
• US Class Current: 345/87
• 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: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 3/003 to produce spatial visual effects
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: H04N 13/315 the parallax barriers being time-variant
• CPC Class Codes: H04N 13/337 using polarisation multiplexing
• CPC Class Codes: H04N 13/341 using temporal multiplexing

Abstract

A voltage may be provided to a liquid crystal addressable element as part of a liquid crystal device. The provided voltage may be reduced from a driven state to a relaxed state in a time period greater than 1 μs. The reduction may further be performed in less than 20 ms. The liquid crystal device may be a polarization switch, which in some embodiments may be a multi-segment polarization switch. In one embodiment, pulses of limited duration of a light source may be provided to the polarization switch. The manner of voltage reduction may reduce optical bounce of the liquid crystal device and may allow one or more of the pulses of the light source to be shifted later in time.

Claims

1. A method for operating a liquid crystal device, comprising:

providing a voltage at a driven level to a liquid crystal addressable element of the liquid crystal device, wherein the liquid crystal addressable element is in a driven state at the driven level;

reducing the provided voltage to a relaxed level;

wherein said reducing is performed over a time period greater than 1 μ

s, wherein the liquid crystal addressable element is in a relaxed state at the relaxed level, wherein said reducing the provided voltage to the relaxed level results in a reduced optical bounce of the liquid crystal device;

providing after the voltage reduction begins, a pulse of limited duration from a light source to the liquid crystal device, wherein the light source is enabled according to a pulse function;

providing another pulse of limited duration of the light source; and

driving, after the another pulse of limited duration of the light source is complete, the voltage to return from the relaxed level to the driven level;

wherein a time difference between a start of the pulse of limited duration and a start of the another pulse of limited duration is less than the time difference from a start of the voltage reduction to a start of the voltage returning to the driven level.

2. The method of claim 1, wherein said reducing is performed over a time period less than 20 ms.

3. The method of claim 1, wherein the liquid crystal device is a polarization switch.

4. The method of claim 3, wherein the polarization switch is a multi-segment polarization switch.

5. The method of claim 4, wherein the provided voltage is independently driven to provide each segment of the polarization switch a voltage that is independent and time-shifted from the independently driven voltages being driven to each other segment.

6. The method of claim 1, further comprising increasing the voltage from the relaxed state to the driven state according to a step function.

7. The method of claim 1, wherein said reducing is performed according to a decreasing portion of a cosine function.

8. The method of claim 1, wherein the liquid crystal device uses a twisted-nematic (TN) liquid crystal mode.

9. The method of claim 1, wherein the liquid crystal device uses a liquid crystal mode that normally exhibits an optical bounce when switching from the driven to the relaxed state.

10. The method of claim 1, wherein the liquid crystal device is a multi-segment polarization switch, and wherein the light source is a segmented backlight, wherein the pulse of limited duration of the light source results in a plurality of subsidiary pulses that are provided to corresponding segments of the polarization switch.

11. The method of claim 1, wherein the provided voltage is a pulse-width modulated waveform.

12. A system, comprising:

a liquid crystal (LC) display, wherein the LC display comprises a liquid crystal device;

a voltage source configured to;

provide a drive voltage to the liquid crystal device; and

reduce the drive voltage to a relaxed level in a time period greater than 1 μ

s, wherein the liquid crystal device is in a relaxed state at the relaxed level, wherein reducing the provided voltage to the relaxed level results in a reduced optical bounce of the liquid crystal device; and

a light source configured to provide light to the liquid crystal device, wherein the light source is a backlight that is configured to produce a first light pulse during a transition from a driven state to the relaxed state and a second light pulse before a transition from the relaxed state to the driven state;

wherein, the voltage source is further configured to drive, after the second light pulse is complete, the voltage to return from the relaxed level to the driven level; and

wherein a time difference between a start of the first light pulse and a start of the second light pulse is less than the time difference from a start of the voltage reduction to a start of the voltage returning to the driven level.

13. The system of claim 12, wherein said reducing is performed in less than 20 ms.

25. The system of claim 12, wherein the liquid crystal device is a polarization switch.

26. The system of claim 25, wherein the polarization switch is a multi-segment polarization switch.

27. The system of claim 26, wherein the voltage source is configured to provide each segment of the multi-segment polarization switch a voltage independently and time-shifted from a voltage being provided to each other segment.

28. The system of claim 27, wherein voltages provided to each segment are derived from the voltage provided to the liquid crystal device.

29. The system of claim 12, wherein the voltage source is further configured to drive the voltage from the relaxed state to the driven state according to a step function.

30. The system of claim 12, wherein the voltage source is further configured to reduce the drive voltage according to a decreasing portion of a cosine function.

31. The system of claim 12, wherein the liquid crystal device uses a twisted-nematic (TN) liquid crystal mode.

32. The system of claim 12, wherein the liquid crystal device uses a liquid crystal mode that normally exhibits an optical bounce when switching from the driven to the relaxed state.

33. The system of claim 12, wherein the liquid crystal device is a multi-segment polarization switch, and wherein the light source is a segmented backlight, wherein a light pulse of the light source results in a plurality of subsidiary pulses that are provided to corresponding segments of the polarization switch.

34. The system of claim 12, wherein the provided voltage is a pulse-width modulated waveform.

14. A non-transitory computer readable storage medium containing program instructions executable to perform:

providing a voltage at a driven level to a liquid crystal addressable element as part of the liquid crystal device, wherein the liquid crystal addressable element is in a driven state at the driven level; and

reducing the provided voltage to a relaxed level;

wherein said reducing is performed in a time period greater than 1 μ

s, wherein the liquid crystal addressable element is in a relaxed state at the relaxed level, wherein said reducing the provided voltage to the relaxed level results in a reduced optical bounce of the liquid crystal device;

providing, after the voltage reduction begins, a pulse of limited duration from a light source to the liquid crystal device, wherein the light source is enabled according to a pulse function;

providing another pulse of limited duration of the light source; and

driving, after the another pulse of limited duration of the light source is complete, the voltage to return from the relaxed level to the driven level;

wherein a time difference between a start of the pulse of limited duration and a start of the another pulse of limited duration is less than the time difference from a start of the voltage reduction to a start of the voltage returning to the driven level.

15. The non-transitory computer readable storage medium of claim 14, wherein said reducing is performed in less than 20 ms.

16. The non-transitory computer readable storage medium of claim 14, wherein the liquid crystal device is a polarization switch.

17. The non-transitory computer readable storage medium of claim 16, wherein the polarization switch is a multi-segment polarization switch.

18. The non-transitory computer readable storage medium of claim 17, wherein the provided voltage is independently driven to provide each segment of the polarization switch a voltage that is independent and time-shifted from the independently driven voltages being driven to each other segment.

19. The non-transitory computer readable storage medium of claim 14, further comprising increasing the voltage from the relaxed state to the driven state according to a step function.

20. The non-transitory computer readable storage medium of claim 14, wherein said reducing is performed according to a decreasing portion of a cosine function.

21. The non-transitory computer readable storage medium of claim 14, wherein the liquid crystal device uses a twisted-nematic (TN) liquid crystal mode.

22. The non-transitory computer readable storage medium of claim 14, wherein the liquid crystal device uses a liquid crystal mode that normally exhibits an optical bounce when switching from the driven to the relaxed state.

23. The non-transitory computer readable storage medium of claim 14, wherein the liquid crystal device is a multi-segment polarization switch, and wherein the light source is a segmented backlight, wherein the pulse of limited duration of the light source results in a plurality of subsidiary pulses that are provided to corresponding segments of the polarization switch.

24. The non-transitory computer readable storage medium of claim 14, wherein the provided voltage is a pulse-width modulated waveform.