Patent Application
20110198711
The field of the invention includes sensors for detecting mechanical movements, such as caused by pressure, sound, magnetic fields, chemical reaction or biological activities.
Methods for detecting the mechanical movements that are relevant to this invention are based on Fabry-Perot interferometry and the piezoresistive effect.
In the application of Fabry-Perot interferometry, the sensing element utilizes an optical cavity where interference of multiple reflections changes with movement of cavity surfaces caused by pressure, sound, chemical reaction or biological activities.
In the application of the piezoresistive effect, a change in electrical resistivity of a sensor material is caused by the application of mechanical stress, which is detected, for example, by a Wheatstone bridge circuit.
In the application of the integrated optical and electronic sensor, a same embossed diaphragm is used as the sensing elements for both parts of the sensor.
The present invention discloses a method of combining two principles of measurements into one integrated unit with optical and electronic parts, namely Fabry-Perot interferometry and piezoresistivity, to detect movement of the sensing element, which is the moving component of the sensor, and to fabricate Fabry-Perot cavities with the assistance of the piezoresitive part of the sensor.
So that those having ordinary skill in the art will have a better understanding of how to make and use the disclosed systems and methods, reference is made to the accompanying figures wherein:
The following is a detailed description of the invention provided to aid those skilled in the art in practicing the present invention. Those of ordinary skill in the art may make modifications and variations in the embodiments described herein without departing from the spirit or scope of the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for describing particular embodiments only and is not intended to be limiting the invention. All publications, patent applications, patents, figures and other references mentioned herein are expressly incorporated by reference in their entirety.
The integrated sensor can be fabricated with MEMS technology. In one embodiment, the sensor contains a diaphragm with a center rigid body, denoted as an embossed diaphragm, which is used as the sensing element for both the optical and electronic parts of the sensor.
The electronic part of the sensor, which is a piezoresistive based sensor, is fabricated with piezoresistors in a Wheatstone bridge configuration. The optical part of the sensor, which is a Fabry-Perot based sensor, contains an optical cavity formed by the center rigid body and a single mode fiber.
The embossed diaphragm together with MEMS technology allows minimizing the Fabry-Perot gap between the diaphragm and the fiber, and thus avoiding misalignment between the fiber and the diaphragm as well as minimizing the back pressure within the cavity.
The output signals from both parts of the sensor can be used independently of each other, as verification of the measured magnitude, and as a mechanism of back-up in continuous monitoring systems.
The signal output obtained from the electronic part of the sensor will be used to assist the fabrication of the Fabry-Perot cavities and as a reference to establish the quiescence point (Q-point) of the signal output from the optical part of the sensor.
Although the systems and methods of the present disclosure have been described with reference to exemplary embodiments thereof, the present disclosure is not limited thereby. Indeed, the exemplary embodiments are implementations of the disclosed systems and methods are provided for illustrative and non-limitative purposes. Changes, modifications, enhancements and/or refinements to the disclosed systems and methods may be made without departing from the spirit or scope of the present disclosure. Accordingly, such changes, modifications, enhancements and/or refinements are encompassed within the scope of the present invention.
