Spatial light modulator and method

• US 5,096,279 A
• Filed: 11/26/1990
• Issued: 03/17/1992
• Est. Priority Date: 08/31/1984
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Nelson, William E., Hornbeck, Larry J.
• Primary Examiner(s): Moskowitz, Nelson
• Application Number:
  US07/618,013
• Time in Patent Office: 477 Days
• Field of Search: 350/269, 358/233
• US Class Current: 359/230
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 3/0008 Structures for avoiding electrostatic attraction, e.g. avoiding charge accumulation
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G02B 26/08 for controlling the direction of light in light guides G02B6/35
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G02B 7/1827 Motorised alignment
• CPC Class Codes: G03F 7/70291 Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices
• CPC Class Codes: G06K 15/1252 using an array of light modulators, e.g. a linear array
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]

Abstract

A method of resetting deflectable pixels of a spatial light modulator is disclosed. A pulse train of voltage is applied to the device to cause it to mobe from its deflected position.

Claims

1. A method of resetting pixels of a deflectable beam spatial light modulator, comprising the steps of:

(a) applying a sequence of voltage pulses to store energy in the hinges of deflectable beams;

wherein the frequency of said sequence of voltage pulses is greater than the operating frequency of said deflectable beams; and

then

(b) removing said voltage to release said stored energy.

2. The method of claim 1, wherein:

(a) said sequence of voltage pulses has a frequency about a resonant frequency of said hinges.

3. The method of claim 2, wherein:

(a) said sequence has five pulses.

4. The method of claim 2, wherein:

(a) each of said voltage pulses is a square wave with 50% duty cycle.

5. The method of claim 1, wherein:

(a) each of said deflectable beams is supported by two torsion hinges, and said energy is stored by bending of said torsion hinges out of their axis of rotation.

6. A method of resetting pixels of a deflectable beam spatial light modulator with opposed addressing electrodes for each pixel, comprising the stops of:

(a) applying a voltage pulse to one of said addressing electrodes, where said one electrode is the electrode opposed to the activation electrode, wherein said pixel is deflected towards said activation electrode, said pulse of duration less than the time constant of the deflectible beam.

7. A method of resetting pixels of a deflectable beam spatial light modulator, comprising the steps of:

(a) applying a magnitude of voltage to the deflected pixels, to store energy in the mechanical structures of the deflected pixels by bending the metal; and

then

(b) removing said voltage to release said stored energy.

8. The method of claim 7, wherein:

said applying a magnitude of voltage to said deflected pixels is a sequence of voltage pulses of said magnitude.

9. The method of claim 8, wherein:

(a) said sequence of voltage pulses has a frequency about a resonant frequency of said hinges.

10. The method of claim 9, wherein:

(a) said sequence has five pulses.

11. The method of claim 9, wherein:

(a) each of said voltage pulses is a square wave with 50% duty cycle.

12. The method of claim 7, wherein:

(a) each of said deflectable beams is supported by two torsion hinges, as said energy is stored by bending of said torsion hinges and said beam caused by the application of said voltage.

13. A method of resetting a deflected pixel of a deflectable beam spatial light modulator, wherein said pixel is held in the deflected position comprising the steps of:

(a) applying a voltage to a deflected deflectable beam spatial light modulator to restore said spatial light modulator to its undeflected position.

14. The method of claim 13, wherein:

(a) said applying of voltage comprises applying said voltage to the beam of said spatial light modulator.

15. The method of claim 13, wherein:

(a) said applying voltage comprises applying the voltage to the electrode on the opposite side of the beam as the activation electrode, wherein said pixel is deflected towards said activation electrode.

16. A method of resetting pixels of a deflectable beam spatial light modulator, comprising the steps of:

(a) applying a sequence of voltage pulses to store energy in the mechanical structure, wherein the frequency of said sequence of voltage pulses is greater than the operating frequency of said deflectable beams; and

then

(b) removing said voltage to release said stored energy.

17. The method of claim 16, wherein:

(a) said sequence of voltage pulses has a frequency about a resonant frequency of said mechanical structure.

18. The method of claim 17, wherein:

(a) said sequence has five pulses.

19. The method of claim 17, wherein:

(a) each of said voltage pulses is a square wave with a 50% duty cycle.

20. The method of claim 16, wherein:

(a) said energy is stored by bending the metal of said mechanical structure.