Liquid crystal variable drive voltage

• US 9,134,556 B2
• Filed: 07/18/2014
• Issued: 09/15/2015
• Est. Priority Date: 05/18/2011
• Status: Active Grant

• Current Assignee: zSpace Inc.
• Original Assignee: zSpace Inc.
• Inventors: Chavez, David A., Cheponis, Michael A., Flynn, Mark F.
• Primary Examiner(s): Sitta, Grant
• Application Number:
  US14/335,708
• Publication Number:
  US 20140327850A1
• Time in Patent Office: 424 Days
• Field of Search: 345/87, 345/204, 345/88, 345/89, 345/690
• US Class Current: 1/1
• 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 multi-segment polarization switch, comprising:

when the multi-segment polarization switch is at a relaxed voltage,

providing to each segment of the multi-segment polarization switch a drive voltage function independent and time-shifted from a drive voltage function being provided to each other segment, wherein for each segment, the drive voltage function is a discontinuous function that drives the segment from the relaxed voltage to a driven voltage; and

when the multi-segment polarization switch is at the driven voltage,

providing to each segment of the multi-segment polarization switch a relax voltage function independent and time-shifted from a relax voltage function being provided to each other segment, wherein for each segment, the relax voltage function is a continuous function that drives the segment from the driven voltage to the relaxed voltage by reducing provided voltage in a continuous manner that results in a reduced optical bounce of the segment.

2. The method of claim 1, wherein the discontinuous function is a step function.

3. The method of claim 1, wherein the continuous function is a decreasing portion of a Gaussian or cosine function.

4. The method of claim 1, wherein the drive voltage function and the relax voltage function are varied from frame to frame.

5. The method of claim 1, further comprising:

when the multi-segment polarization switch is at a relaxed voltage,

providing light to the multi-segment polarization switch via a first light pulse during a transition from the relaxed voltage to the driven voltage; and

when the multi-segment polarization switch is at a drive voltage,

providing light to the multi-segment polarization switch via a second light pulse during a transition from the driven voltage to the relaxed voltage.

6. The method of claim 5, wherein each pulse results in a plurality of subsidiary pulses that are provided to corresponding segments of the multi-segment polarization switch.

7. The method of claim 1, wherein the multi-segment polarization switch uses a twisted-nematic (TN) liquid crystal mode.

8. A system comprising:

a liquid crystal (LC) display, wherein the LC display comprises a multi-segmented polarization switch; and

a voltage source configured to;

when the multi-segment polarization switch is at a relaxed voltage,

apply to each segment of the multi-segment polarization switch a drive voltage function independent and time-shifted from a drive voltage function being applied to each other segment, wherein for each segment, the drive voltage function is a discontinuous function that drives the segment from the relaxed voltage to a driven voltage; and

when the multi-segment polarization switch is at the driven voltage,

apply to each segment of the multi-segment polarization switch a relax voltage function independent and time-shifted from a relax voltage function being applied to each other segment, wherein for each segment, the relax voltage function is a continuous function that drives the segment from the driven voltage to the relaxed voltage by reducing provided voltage in a continuous manner that results in a reduced optical bounce of the segment.

9. The system of claim 8, wherein the discontinuous function is a step function.

10. The system of claim 8, wherein the continuous function is a decreasing portion of a Gaussian or cosine function.

11. The system of claim 8, wherein the voltage source is further configured to vary the drive voltage function and the relax voltage function from frame to frame.

12. The system of claim 8, further comprising a light source configured to provide light to the multi-segment polarization switch, wherein the light source is a backlight that is configured to:

when the multi-segment polarization switch is at a relaxed voltage,

provide light to the multi-segment polarization switch via a first light pulse during a transition from the relaxed voltage to the driven voltage; and

when the multi-segment polarization switch is at a drive voltage,

provide light to the multi-segment polarization switch via a second light pulse during a transition from the driven voltage to the relaxed voltage.

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

14. The system of claim 8, wherein the multi-segment polarization switch uses a twisted-nematic (TN) liquid crystal mode.

15. A non-transitory computer readable memory medium storing program instructions executable by a processor to:

when a multi-segment polarization switch is at a relaxed voltage,

apply to each segment of the multi-segment polarization switch a drive voltage function independent and time-shifted from a drive voltage function being applied to each other segment, wherein for each segment, the drive voltage function is a discontinuous function that drives the segment from the relaxed voltage to a driven voltage; and

when the multi-segment polarization switch is at the driven voltage,

apply to each segment of the multi-segment polarization switch a relax voltage function independent and time-shifted from a relax voltage function being applied to each other segment, wherein for each segment, the relax voltage function is a continuous function that drives the segment from the driven voltage to the relaxed voltage by reducing provided voltage in a continuous manner that results in a reduced optical bounce of the segment.

16. The non-transitory computer readable memory medium of claim 15, wherein the discontinuous function is a step function.

17. The non-transitory computer readable memory medium of claim 15, wherein the continuous function is a decreasing portion of a Gaussian or cosine function.

18. The non-transitory computer readable memory medium of claim 15, wherein the voltage source is further configured to vary the drive voltage function and the relax voltage function from frame to frame.

19. The non-transitory computer readable memory medium of claim 15, wherein the program instructions are further executable by a processor to:

when the multi-segment polarization switch is at a relaxed voltage,

provide light to the multi-segment polarization switch via a first light pulse from a light source during a transition from the relaxed voltage to the driven voltage; and

when the multi-segment polarization switch is at a drive voltage,

provide light to the multi-segment polarization switch via a second light pulse from the light source during a transition from the driven voltage to the relaxed voltage.

20. The non-transitory computer readable memory medium of claim 19, wherein each pulse results in a plurality of subsidiary pulses that are provided to corresponding segments of the multi-segment polarization switch.