Micro-electro-mechanical systems ultra-sensitive accelerometer
First Claim
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1. A high sensitivity micro-electro-mechanical optical accelerometer comprising:
- an interferometer, including a pair of partially transmissive, partially reflective, surfaces wherein a first of said surfaces is flexibly suspended adjacent and parallel to a second of said surfaces so that a gap exists therebetween;
a proof mass attached to said flexibly suspended first surface;
a photosensor attached to one of said surfaces outside of said gap; and
a source of monochromatic light, said light for irradiating said photosensor through said first and second surfaces wherein said light is also partially reflected between said surfaces;
whereby a change in said gap due to an acceleration force is sensed by a change in said light as detected by said photosensor.
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Abstract
An accelerometer is based upon the monolithic integration of a Fabry-Perot interferometer and a p+n silicon photosensor. Transmission of light through a Fabry-Perot etalon is exponentially sensitive to small displacements in a movable mirror due to an applied accelerating force. The photosensor converts this displacement into an electrical signal as well as provides for additional amplification. Because the interferometer and photosensor are monolithically integrated on a silicon substrate, the combination is compact and has minimal parasitic elements, thereby reducing the accelerometer'"'"'s noise level and increasing its signal-to-noise ratio (SNR).
The accelerometer'"'"'s sensitivity can be user-controlled by any one or a combination of factors: providing an electrostatic potential across the mirrors of the Fabry-Perot etalon hence selecting a desired gap therebetween; adjusting the power of the light projected to the photosensor; and pulsing the light at a selected frequency to minimize 1/f inherent system noise in the response of the accelerometer.
61 Citations
43 Claims
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1. A high sensitivity micro-electro-mechanical optical accelerometer comprising:
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an interferometer, including a pair of partially transmissive, partially reflective, surfaces wherein a first of said surfaces is flexibly suspended adjacent and parallel to a second of said surfaces so that a gap exists therebetween;
a proof mass attached to said flexibly suspended first surface;
a photosensor attached to one of said surfaces outside of said gap; and
a source of monochromatic light, said light for irradiating said photosensor through said first and second surfaces wherein said light is also partially reflected between said surfaces;
whereby a change in said gap due to an acceleration force is sensed by a change in said light as detected by said photosensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
a source of variable electrostatic potential for providing a selected electrostatic potential between said first and second surfaces so that said gap is adjustable, wherein said sensitivity of said accelerometer is variable by adjusting said gap. -
22. The apparatus of claim 1 wherein said sensitivity of said accelerometer is variable by activating and de-activating said light at a selected frequency.
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23. A high sensitivity micro-electro-mechanical optical accelerometer comprising:
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an interferometer, including a pair of partially transmissive, partially reflective, surfaces wherein a first of said surfaces is flexibly suspended adjacent and parallel to a second of said surfaces so that a gap exists therebetween;
a source of variable electrostatic potential for providing a selected electrostatic potential between said first and second surfaces so that the said gap is adjustable;
a proof mass attached to said flexibly suspended first surface;
a photosensor attached to said second surface outside of said gap; and
a source of monochromatic light, said light for irradiating said photosensor through said first and second surfaces wherein said light is also partially reflected between said surfaces;
wherein said sensitivity of said accelerometer is variable by adjusting said gap, and is variable by activating and de-activating said light at a selected frequency, whereby a change in said gap due to an acceleration force is sensed by a change in said light as detected by said photosensor. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. A high sensitivity micro-electromechanical optical accelerometer comprising:
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a Fabry-Perot interferometer, including a pair of partially transmissive, partially reflective, surfaces wherein a first of said surfaces is flexibly suspended adjacent and parallel to a second of said surfaces so that a gap exists therebetween;
a source of variable electrostatic potential for providing a selected electrostatic potential between said first and second surfaces so that said gap is adjustable;
a proof mass attached to said flexibly suspended first surface;
a photodiode is attached to said second surface outside of said gap; and
a source of variable power, fixed wavelength, laser light, said light for irradiating said photodiode through said first and second surfaces wherein said light is also partially reflected between said surfaces;
wherein said sensitivity of said accelerometer is variable by adjusting said gap, said power of said light and by activating and de-activating said light at a selected frequency, whereby a change in said gap due to an acceleration force is sensed by a change in said light as detected by said photodiode. - View Dependent Claims (40, 41, 42, 43)
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Specification
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Current AssigneeUnited States Department Of Health And Human Services
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Original Assigneethe united states of america as represented by the secretary of the navy
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InventorsWaters, Richard L., Aklufi, Monti E.
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Primary Examiner(s)KWOK, HELEN C
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Application NumberUS09/808,570Time in Patent Office832 DaysField of Search735/142.6, 735/141.9, 735/142.7, 735/141.6, 735/140.1, 735/142.9, 356/33, 356/450, 356/505, 356/506US Class Current73/514.26CPC Class CodesG01C 19/56 Turn-sensitive devices usin...
