Spatial light modulator having an analog beam for steering light

• US 5,629,794 A
• Filed: 05/31/1995
• Issued: 05/13/1997
• Est. Priority Date: 05/31/1995
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Magel, Gregory A., Boysel, Robert M., Florence, James M.
• Primary Examiner(s): Epps, Georgia Y.
• Assistant Examiner(s): BEY, DAWN MARIE
• Application Number:
  US08/455,475
• Time in Patent Office: 713 Days
• Field of Search: 359/290, 359/291, 359/212, 359/213, 359/214, 359/846, 359/847, 359/848, 359/849, 359/850, 359/851
• US Class Current: 359/290
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

A spatial light modulator (40, 70, 80) operable in the analog mode for light beam steering or scanning applications. A deflectable mirror (42, 72) is supported by a torsion hinge (44) along a torsion axis. A plurality of flexure hinges (48) are provided to support the corners of the mirror (42, 72) and provide a restoration force. The combination of the torsion hinges and the flexure hinges realizes a deflectable pixel that is operable in the linear range for a large range of address voltages. The flexure hinges also maintain a flat undeflected state when no address voltage is applied, and prevent the pixel from collapsing. The pixel may be reinforced, such as about its perimeter (74) to ensure mirror flatness and prevent warping, even during extreme deflections of the mirror. The pixel is electrostatically deflected by applying an address voltage to an underlying address electrode (60).

Claims

1. An improved spatial light modulator of the type which includes a generally planar light-reflective pixel which is deflectable out of a first, normal position into a plurality of second positions, light incident on the pixel being selectively modulated by being reflected from the pixel in selected directions depending on the position of the pixel, the position of the pixel being dependent on a selected characteristic of an electrical signal provided to an underlying address circuit, the deflection of the pixel storing potential mechanical energy in a pixel-supporting facility, which stored energy tends to return the pixel to the first position, wherein the improvement comprises:

the pixel-supporting facility including

a first torsion member connected between the pixel and a first stationary post and defining a torsion axis, deflection of the pixel effecting its rotation about the torsional axis of the first member; and

a second flexure member connected between the pixel and a second stationary post, deflection of the pixel effecting flexure of the second member.

2. An improved modulator as set forth in claim 1, wherein:

the points of connection of the members to the pixel are separated about the periphery of the pixel.

3. An improved modulator as in claim 2, wherein:

the pixel has a generally orthogonal profile,

the first member is connected to the pixel at a mid-point of a first side thereof, and

the second member is connected to the first side of the pixel.

4. An improved modulator as in claim 3, wherein:

the second member is connected to the pixel proximate the juncture of the first side of the pixel and a second side of the pixel.

5. An improved modulator as in claim 2, wherein:

the torsional axis of the first member is generally co-planar with the pixel, and

the second member in its unflexed state is oriented so as to be generally co-planar with the pixel and perpendicular to the torsional axis of the first member.

6. An improved modulator as in claim 5, wherein:

the second member in its flexed state defines a curved surface, the surface of which is generally perpendicular to the torsional axis of the first member.

7. An improved modulator as in claim 1, wherein:

the characteristics of the first member are such that the deflection of the pixel out of the first position is predominantly rotational about the torsion axis, and the characteristics of the second member are such that the first position of the pixel is predominantly determined by the second member.

8. An improved modulator as in claim 7, wherein:

the characteristics of the members are such that the pixel is selectively deflectable out of the first position into a plurality of the second positions determined by the selected characteristic of the electrical signal.

9. An improved modulator as in claim 1, wherein:

the first and second members are respectively connected to separated said first and second posts.

10. An improved modulator as in claim 1, wherein:

the first and second members are connected to the same said posts.

11. An improved modulator as in claim 1, wherein:

the pixel is reinforced to maintain flatness.

12. The improved modulator as in claim 11, wherein:

the pixel is reinforced about a perimeter thereof.

13. The improved modulator as in claim 12, wherein:

the pixel is corrugated about the perimeter.

14. The improved modulator as in claim 11, wherein the pixel is radially reinforced from proximate a midsection thereof.