High frequency deformable mirror device

• US 20020135857A1
• Filed: 03/26/2001
• Published: 09/26/2002
• Est. Priority Date: 03/26/2001
• Status: Active Grant

• Current Assignee: Creo Products Incorporated
• Original Assignee: Creo Products Incorporated
• Inventors: Gelbart, Daniel, Fitzpatrick, Glen Arthur
• Granted Patent: US 6,661,561 B2
• Time in Patent Office: Days
• US Class Current: 359/291
• CPC Class Codes: B41J 2/465 using masks, e.g. light-switching masks
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

In accordance with the present invention, an array of individually addressable micromachined light reflecting ribbons provide a high speed light valve action by employing a method in accordance with which the ribbons flex about their longer axis under the action of an applied electrostatic field. The ribbons are mounted on pedestals such that the resulting micromechanical structures are substantially symmetrical with respect to a plane along their long axis through the centers of the pedestals and normal to the substrate. This micromechanical arrangement ensures a structure with a high natural frequency, thereby allowing high light valve switching speeds. The particular mode of deformation also ensures a robust structure. The method may be applied in either “bright field” or “dark field” (Schlieren) mode. The particular combination of materials employed allows the method to be used in higher incident power applications such as those encountered in the printing industry. The invention uses the fabrication methods developed for grating light valves to build a deformable mirror light valve combining the fabrication and speed advantages of the former with the simplicity of the latter. Since the ribbons flex about their long axes, the amplitude of tip deflection required to produce a given angular light deflection is much smaller than that required by prior art cantilever devices, which flex about their short axes.

Claims

1. A method for modulating light using a microelectromechanical structure, said microelectromechanical structure comprising a plurality of thin flexible reflective members, said reflective members having elongated shapes, said elongated shapes having a long dimension and a short dimension, said reflective members having at least one reflector surface, said reflector surface having reflective segments that are reflective to said light and said reflective members being capable of being flexed independently of one another, said method comprising directing a beam of light to reflect from said reflective members and flexing a part of said reflective members about an axis parallel to said long dimension.

2. A method as in claim 1 wherein said flexing is induced by application of one of the following forces to said reflective members:

electrostatic, magnetic.

3. A method as in claim 2 wherein said reflective members are affixed to the rest of said microelectromechanical structure along lines parallel to said long dimension.

4. A method as in claim 3 wherein said reflective members are affixed to the rest of said microelectromechanical structure along said long dimension.

5. A method as in claim 2 wherein a lesser-deflecting fraction of said reflector surface is absorbing to said light.

6. A method as in any of the above claims wherein said flexing is localized to regions of said reflective members thereby allowing said regions of said reflective members to operate as hinges.

7. A method as in claim 4 wherein the wings of said microelectromechanical structure are capable of being flexed independently from each other and wherein said reflective segments are separated by a part of said reflector surface that is absorbing to said light.

8. A method as in claim 3 wherein at least one of the axial ends of said reflective members is attached to the rest of said microelectromechanical structure.

9. A method as in claim 2, wherein said electrostatic force acts between a first electrode, located on said reflective members, and a second electrode, located on the substrate of said microelectromechanical device and spaced from said first electrode to form a capacitor between said first electrode and said second electrode, said electrostatic force being generated through the application of a voltage between said first electrode and said second electrode.

10. A deformable mirror device for modulating light, comprising a microelectromechanical structure having a plurality of thin flexible reflective members,

a. said reflective members having elongated shapes with a long dimension and a short dimension and

b. said reflective members having at least one reflector surface and

c. said reflector surface having reflective segments that are reflective to said light and

d. said reflective members being disposed to flex over part of their surface about an axis parallel to said long dimension and

e. said reflective members being capable of being flexed independently from one another and

f. said deformable mirror device being capable of allowing an incident beam of light to be reflected from said at least one reflector surface

11. An apparatus as in claim 10 wherein said reflective members are so positioned relative to an aperture that there exists a particular degree of flexure of any one of said reflective members for which the major fraction of said beam of light reflecting from said one reflective member passes through said aperture.

12. An apparatus as in claim 10 wherein said flexing is induced in said reflective members by application of one of the following forces:

electrostatic, magnetic.

13. An apparatus as in claim 12 wherein said reflective members are affixed to the rest of said microelectromechanical structure along a line parallel to said long dimension.

14. An apparatus as in claim 13 wherein said reflective members are affixed to the rest of said microelectromechanical structure along said long dimension.

15. An apparatus as in claim 12 wherein a lesser-deflecting fraction of said reflector surface is absorbing to said light.

16. A method as in claim 10, 11, 12, 13, 14 or 15 wherein said flexing is localized to regions of said reflective members thereby allowing said regions of said reflective members to operate as hinges.

17. An apparatus as in claim 14 wherein the wings of said microelectromechanical structure are capable of being flexed independently from each other and wherein said reflective segments are separated by a part of said reflector surface that is absorbing to said light.

18. An apparatus as in claim 13 wherein at least one of the axial ends of said reflective members is attached to the rest of said microelectromechanical structure.

19. An apparatus as in claim 12, wherein said electrostatic force acts between a first electrode, located on said reflective members, and a second electrode, located on the substrate of said microelectromechanical device and spaced from said first electrode to form a capacitor between said first electrode and said second electrode, said electrostatic force being generated through the application of a voltage between said first electrode and said second electrode.

20. An apparatus as in claim 19 wherein said reflective members are fabricated from silicon nitride and said at least one reflector surface comprises at least one reflective layer composed of at least one of the following:

gold, palladium, platinum, chromium, aluminum, tantalum, titanium.