Optical: systems and elements – Mirror – With support
Reexamination Certificate
1999-05-03
2002-08-06
Shafer, Ricky D. (Department: 2872)
Optical: systems and elements
Mirror
With support
C359S881000, C359S223100, C359S224200, C359S230000
Reexamination Certificate
active
06428173
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to microelectromechanical structures, and more particularly to thermally actuated microelectromechanical mirror structures and associated methods.
BACKGROUND OF THE INVENTION
Microelectromechanical structures (MEMS) and other microengineered devices are presently being developed for a wide variety of applications in view of the size, cost and reliability advantages provided by these devices. Many different varieties of MEMS devices have been created, including microgears, micromotors, and other micromachined devices that are capable of motion or applying force. These MEMS devices can be employed in a variety of applications including hydraulic applications in which MEMS pumps or valves are utilized and optical applications which include MEMS light valves and shutters.
MEMS devices have relied upon various techniques to provide the force necessary to cause the desired motion within these microstructures. Some MEMS devices are driven by electromagnetic fields, while other micromachined structures are activated by piezoelectric or electrostatic forces. Recently, MEMS devices that are actuated by the controlled thermal expansion of an actuator or other MEMS component have been developed. For example, U.S. patent application Ser. Nos. 08/767,192; 08/936,598, and 08/965,277 which are assigned to MCNC, the assignee of the present invention, describe various types of thermally actuated MEMS devices. The contents of each of these applications are hereby incorporated by reference herein. Thermal actuators as described in these applications comprise arched beams formed from silicon or metallic materials that further arch or otherwise deflect when heated, thereby creating motive force. These applications also describe various types of direct and indirect heating mechanisms for heating the beams to cause further arching. While the thermally-actuated MEMS devices of these applications are described in conjunction with a variety of MEMS structures, such as MEMS relays, valves and the like, these applications do not describe thermally-actuated mirror assemblies.
However, MEMS devices including moveable mirror structures have been developed. Commonly, MEMS moveable mirror devices have been used to redirect electromagnetic energy traveling along a path, typically a light or laser beam. For instance, U.S. patent application Ser. No. 08/719,711, also assigned to MCNC and incorporated by reference herein, describes various types of MEMS devices which can rotate a reflective plate about several axes within a framed structure. While these devices can be used for communications, laser printing, or various other applications, these do not provide laterally moveable mirrors.
Lucas NovaSensor of Fremont, Calif. has also developed a variety of MEMS devices including thermally actuated mirror structures. For example, these mirror structures include a matrix addressable thermally actuated mirror suitable for use in an optical switching array. These mirror structures generally include silicon beams connected to the mirror that conduct electrical current and are deflected by the resulting heat in order to position the mirror. In some of the mirror structures, the mirror is conductive and forms part of the electrical heating circuit. Regardless of the manner in which the structures are actuated, the reflective surfaces of the mirrors are disposed in a plane parallel to the underlying substrate when the device is not actuated and can be moved either in plane or out of plane upon thermal actuation.
While some thermally activated MEMS mirror structures have been developed, it would still be advantageous to develop other types of moveable mirror structures that would be suitable for a wider variety of applications. For instance, moveable mirror structures that have mirrors disposed out of plane relative to both the underlying substrate and the direction of movement provided by the actuator are needed. Further, it would be advantageous to provide a MEMS moveable mirror device that could precisely position a mirror and reliably hold the mirror in position, even after the thermal energy used to position the mirror is removed. The efficiency and performance of MEMS mirror devices in applications involving the precise deflection of multiple narrow beams of electromagnetic radiation could thus be improved. For example, high resolution optical switching arrays could be developed from MEMS mirror devices providing these advantageous attributes.
SUMMARY OF THE INVENTION
The present invention provides several embodiments of a moveable microelectromechanical mirror structure that collectively satisfy the above needs and provide several advantageous features. According to the present invention, the moveable MEMS mirror structure includes a thermal actuator and a mirror having a mirrored surface that is disposed out of plane relative to the thermal actuator and to the underlying microelectronic substrate. The MEMS mirror structure provides precise movement of the mirror using the thermal actuator and permits the mirror to be held in a fixed position, even after the thermal actuator is deactivated. Further, MEMS moveable mirror structures may be disposed in an array and individually controlled to serve a variety of switching applications or the like.
In one embodiment, the MEMS moveable mirror structure includes a microelectronic substrate having a first major surface, a microactuator, and a mirror. The microactuator is preferably formed from a single crystal material and is disposed upon the first major surface of the microelectronic substrate. The microactuator is thermally actuated so as to controllably move along a predetermined path that extends substantially parallel to the first major surface of the microelectronic substrate. The mirror is also preferably formed from the single crystal material and is adapted for movement with said microactuator. In particular, the mirror is arranged to move with the microactuator in response to thermal actuation, thus having a non-actuated position and an actuated position. The actuated position can vary accordingly as the microactuator moves along the predetermined path in response to thermal actuation. According to the present invention, the mirror has a mirrored surface disposed out of plane relative to the first major surface of the microelectronic substrate whether in the non-actuated or actuated position.
In one embodiment, the microactuator of the MEMS moveable mirror structure comprises a thermal arched beam actuator. This actuator includes at least two anchors affixed to the microelectronic substrate and at least one thermal arched beam disposed between the anchors. Each thermal arched beam is adapted to arch further and controllably move along the predetermined path in response to the selective application of thermal actuation. The microactuator can optionally include a spring adapted to flex during selective thermal actuation. While the thermal arched beam actuator need only have a single arched beam, the microactuator of the MEMS moveable mirror structure can comprise a plurality of thermal arched beams. In one embodiment, for example, the plurality of thermal arched beams are arrayed to expand in response to thermal actuation and collectively move along the predetermined path. In another embodiment, the plurality of thermal arched beams are arrayed to compress in response to thermal actuation and collectively move along the predetermined path. In any embodiment, the thermal arched beam actuator can include an electrically conductive path disposed through or upon at least part of the thermal arched beams in order to direct the current flow and correspondingly control the heating of the thermal arched beams.
In another embodiment, the microactuator of the MEMS moveable mirror structure comprises at least one thermally actuated composite beam actuator. This actuator includes at least one anchor affixed to the microelectronic substrate and a composite beam extending from the anchor and overlying the first major surface ther
Cowen Allen Bruce
Dhuler Vijayakumar R.
Hill Edward A.
Walters Mark David
JDS Uniphase Inc.
Myers Bigel & Sibley & Sajovec
Shafer Ricky D.
LandOfFree
Moveable microelectromechanical mirror structures and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Moveable microelectromechanical mirror structures and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Moveable microelectromechanical mirror structures and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2910356