Capacitive sensing scheme for digital control state detection in optical switches
First Claim
1. A microelectromechanical device, comprisinga. a rotating element including a first electrode;
- b. a vertical stop disposed proximate the rotating element;
c. a second electrode;
d. means, coupled to the first and second electrodes for measuring a capacitance between them; and
e. means coupled to the capacitance sensing means for determining from the capacitance a digital control state of device.
2 Assignments
0 Petitions
Accused Products
Abstract
Disclosed is an apparatus and method for detecting whether rotatable MEMS elements are in the “on” or “off” position. Embodiments of the invention have application in devices switches that employ mirrors that move between an “on” or “off” position, wherein they reflect light from an input fiber into an output fiber in the “on” position, and allow the light to pass in the “off” position. Electrodes are positioned in the device such that the mirrors are close to, and therefor capacitively coupled to, a different electrode depending on whether they are in the “on” or “off” position. This invention is especially useful for switches that already employ electrodes for electrostatic clamping of mirrors in one or more positions, since those same electrodes can be used both to electrostatically clamp the mirrors and to sense their position. The method described in this invention comprises sensing of the capacitance between the mirrors and the one or more electrodes used to clamp the mirrors in its one or more position in order to detect which of the positions the mirrors are clamped in. Furthermore, the magnitude of the capacitances can be monitored to detect improper clamping.
82 Citations
22 Claims
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1. A microelectromechanical device, comprising
a. a rotating element including a first electrode; -
b. a vertical stop disposed proximate the rotating element;
c. a second electrode;
d. means, coupled to the first and second electrodes for measuring a capacitance between them; and
e. means coupled to the capacitance sensing means for determining from the capacitance a digital control state of device. - View Dependent Claims (2, 3, 4, 5)
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6. A microelectromechanical system (MEMS) apparatus, comprising
a. an element configured to rotate between a first control state and a second control state; -
b. a vertical stop disposed proximate the element;
c. one or more electrodes disposed proximate the element, wherein a capacitance between the element and the one or more electrodes has a first value when the element is in the first control state and the capacitance has a second value when the element is in the second control state;
d. means, for measuring a value of the capacitance between the element and the at least one of the one or more electrodes; and
e. means coupled to the capacitance sensing means for determining a control state of the element from the value of the capacitance. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for sensing the control state of a microelectromechanical device, comprising:
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measuring a value of a capacitance between a rotatable element and one or more of a first and second electrode disposed proximate the rotatable element to determine whether the rotatable element is in a first control state, a second control state, or neither the first nor second control state, wherein the rotatable element is in a vertical position proximate a vertical stop when the rotatable element is in the first or second control state. - View Dependent Claims (17, 18, 19, 20, 21)
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22. An optical communications system, comprising:
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a) one or more input optical fibers;
b) one or more output optical fibers;
c) a microelectromechanical system (MEMS) optical switch including;
ii) one or more MEMS mirrors configured to rotate between a first angular position and a second angular position;
ii) b. a vertical stop disposed proximate one or more of the MEMS mirrors;
iii) one or more electrodes disposed proximate each of the one or more mirrors, wherein a capacitance between the mirrors and the electrodes has a first value when the mirrors are in a first control state and the capacitance has a second value when the element is in a second control state;
iv) means, for measuring a value the capacitance between at least one of the one or more mirrors and the at least one of the one or more electrodes; and
v) means coupled to the capacitance sensing means for determining a control state of the element from the value of the capacitance.
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Specification