Method for eliminating pi-cell artifacts

• US 20020003509A1
• Filed: 01/19/2001
• Published: 01/10/2002
• Est. Priority Date: 01/20/2000
• Status: Active Grant

• Current Assignee: RealD Incorporated
• Original Assignee: Real D
• Inventors: Lipton, Lenny, Dorworth, Bruce, Halnon, Jeffrey J., Wuopio, Jeff
• Granted Patent: US 7,502,003 B2
• Time in Patent Office: Days
• US Class Current: 345/7
• CPC Class Codes: G02F 1/1395 Optically compensated birefringence [OCB]- cells or PI- cells

Abstract

An alternating unipolar carrier waveform is used to drive a pi-cell modulator. The pi-cell is driven by the carrier, but the carrier never changes polarity within the time period that the cell is energized. However, each time the cell is energized, i.e., once per field, the polarity alternates. Further, a burst of pulses each separated by a short rest period is used on initial application of power to more quickly drive the pi-cell to its activated state,

Claims

1. A method for driving a pi-cell modulator in a stereoscopic image viewing system, comprising applying an alternating, unipolar-carrier waveform to the pi-cell, wherein the carrier waveform does not change polarity within a time period that the pi-cell is energized.

2. A method as in claim 1, wherein the waveform is in the range of 1-2 kHz.

3. A method as in claim 1, wherein a stutter start waveform is applied to the pi-cell for a brief period of time when power is first applied.

4. A method as in claim 3, wherein the stutter start waveform is a series of pulses separated by a small rest period.

5. A method as in claim 4, wherein the small rest period is approximately a few hundred milliseconds.

6. A method for driving a pi-cell modulator in a stereoscopic image viewing system, comprising:

applying a modulating waveform having a carrier signal of a first polarity to the pi-cell during a first time period, wherein the carrier signal does not change polarity during the first time period;

removing the waveform

applying the waveform having a carrier signal of a second polarity opposite the first polarity to the pi-cell during a second time period, wherein the carrier signal does not change polarity during the second time period.

7. A method as in claim 6, wherein the waveform is in the range of 1-2 kHz.

8. A method as in claim 6, wherein a burst of pulses is applied to the pi-cell for a brief period of time when power is first applied.

9. A method as in claim 8, wherein each of the burst of pulses is separated by a small rest period.

10. A method as in claim 9, wherein the small rest period is approximately a few hundred milliseconds.

11. A stereoscopic image viewing system, comprising:

a pi-cell modulator; and

a drive circuit for applying an alternating, unipolar carrier waveform to the pi-cell, wherein the carrier waveform does not change polarity within a time period that the pi-cell is energized.

12. A system as in claim 11, wherein the carrier waveform is in the range of 1-2 kHz.

13. A system as in claim 11, wherein a burst of pulses is applied to the pi-cell for a brief period of time when power is first applied.

14. A system as in claim 13, wherein each of the burst of pulses is separated by a small rest period.

15. A system as in claim 14, wherein the small rest period is approximately a few hundred milliseconds.