Dual membrane single cavity Fabry Perot MEMS filter

• US 20050134962A1
• Filed: 12/22/2003
• Published: 06/23/2005
• Est. Priority Date: 12/22/2003
• Status: Active Grant

• Current Assignee: Axsun Technologies Incorporated
• Original Assignee: Axsun Technologies Incorporated
• Inventors: Verghese, Paul Mattackal
• Granted Patent: US 7,420,738 B2
• Time in Patent Office: Days
• US Class Current: 359/579
• CPC Class Codes: G01J 3/26 using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters

Abstract

A dual membrane, single cavity MEMS Fabry-Perot filter has a cavity that is defined between two mirror structures that are located on separate MEMS membranes. This configuration can yield a number of advantages. First, the membranes will be typically subject to the same mechanical vibrations, thus, will vibrate together. This vibration, however, will be rejected as common mode, however. Moreover, since the membranes will move in opposed directions in the gravitational field, the dual membrane device is insulated against passband shifts resulting from changes in orientation in the gravitational field. Finally, since each membrane can now be deflected separately, the scanning range is effectively doubled without increases in the size of the electrostatic cavities.

Claims

1. A single cavity dual membrane Fabry-Perot tunable filter comprising:

a first membrane device comprising a first membrane holding a first mirror structure; and

a second membrane device with a second membrane holding a second mirror structure, which is opposed the first mirror structure, to thereby define a Fabry-Perot cavity between the first mirror structure and the second mirror structure.

2. A Fabry-Perot tunable filter as claimed in claim 1, further comprising a spacer between the first membrane device and the second membrane device for controlling a size of the Fabry-Perot cavity.

3. A Fabry-Perot tunable filter as claimed in claim 1, wherein the first membrane device and the second membrane device include electrostatic cavities for deflecting the first membrane and the second membrane.

4. A Fabry-Perot tunable filter as claimed in claim 1, wherein the first membrane device and the second membrane device are flat mirrors.

5. A Fabry-Perot tunable filter as claimed in claim 1, wherein at least one of the first mirror structure and the second mirror structure is curved mirror structure.

6. A Fabry-Perot tunable filter as claimed in claim 1, wherein, the both the first mirror structure and the second mirror structure are curved mirrors.

7. A Fabry-Perot tunable filter as claimed in claim 1, wherein each of the membrane devices comprises a substrate, the membranes being deflected by the establishment of an electrostatic drive voltage between the substrates and the membranes.

8. A Fabry-Perot tunable filter as claimed in claim 7, further comprising an optical port through the substrate of at least one of the first membrane devices and the second membrane device.

9. A Fabry-Perot tunable filter as claimed in claim 1, wherein the mirror structures comprise highly reflecting dielectric mirrors.

10. A Fabry-Perot tunable filter as claimed in claim 1, wherein a drive voltage generator establishes a voltage between the substrates of the membranes and the membranes.

11. A Fabry-Perot tunable filter as claimed in claim 1, wherein a drive voltage generator establishes a drive voltage between the membrane of the first membrane device and the membrane of the second membrane device.