EP0196784A2
Expired / Lapsed
EP
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Fabry Perot pressure sensor with diaphragm
Assignee: Imperial Chemical Industries Ltd
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Filing: 1986-02-28
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Granted: —
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Expires: 2006-02-28
Abstract
Abstract An optical pressure sensor comprises a resiliently flexible diaphragm and a rigid transparent cover plate mounted substantially parallel to the diaphragm and spaced therefrom by a collar so as to form a cavity between them. The opposing surfaces of the plate and diaphragm within the cavity are reflective, and form between them a Fabry Perot cavity, with the transparent cover plate enabling light to enter and escape from the cavity. The pressure to be sensed is applied to the diaphragm to cause it to flex and consequently to vary the Fabry Perot interference pattern according to changes in the pressure. The cavity is very thin, e.g. less than 1 micron between diaphragm and cover plate, and this can be formed cheaply by manufacturing the diaphragm from semi-conductor material such as silicon, and etching it to form the cavity.
Inventors
- 👤 Eric Reginald Cox
- 👤 Desmond Ernest Smith
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 17:00
CPC Classifications
G; G01; G01L; G01L9/00; G01L9/0041; G01L9/0076; G01L9/0077; G01L9/0079
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
149 words
An optical pressure sensor comprising a resiliently flexible diaphragm and a rigid transparent cover plate mounted substantially parallel to the diaphragm and spaced therefrom by a collar which is integral with one of them and secured against the other, thereby to define between the plate and the diaphragm a cavity bounded by the collar with the diaphragm and the cover plate each having an inner surface within the cavity and an outer surface outside the cavity, the two opposed inner surfaces being reflective thereby to form a reflective Fabry Perot cavity with the transparent cover plate enabling light to enter and escape from the cavity and the sensor being adapted to receive on the outer surface of the diaphragm the fluid whose pressure is to be sensed thereby to cause flexing of the diaphragm and consequential variation in the Fabry Perot interference pattern according to changes in the pressure.
Claim 2
Dependent Claim
149 words
An optical pressure sensor comprising a resiliently flexible diaphragm and a rigid transparent cover plate mounted substantially parallel to the diaphragm and spaced therefrom by a collar which is integral with one of them and secured against the other, thereby to define between the plate and the diaphragm a cavity bounded by the collar with the diaphragm and the cover plate each having an inner surface within the cavity and an outer surface outside the cavity, the two opposed inner surfaces being reflective thereby to form a reflective Fabry Perot cavity with the transparent cover plate enabling light to enter and escape from the cavity and the sensor being adapted to receive on the outer surface of the diaphragm the fluid whose pressure is to be sensed thereby to cause flexing of the diaphragm and consequential variation in the Fabry Perot interference pattern according to changes in the pressure.
Claim 3
Dependent Claim
20 words
A pressure sensor as claimed in claim 1 wherein the diaphragm is integral with the collar formed around its periphery.
Claim 4
Dependent Claim
20 words
A pressure sensor as claimed in claim 2 wherein the diaphragm and collar are manufactured from a semi- conductor material.
Claim 5
Dependent Claim
16 words
A pressure sensor as claimed in claim 3 wherein the semiconductor material consists essentially of silicon.
Claim 6
Dependent Claim
24 words
A pressure sensor as claimed in claim 3 or claim 4 wherein the inner surface of the diaphragm is a smooth etched semi-conductor surface.
Claim 7
Dependent Claim
26 words
A pressure sensor as claimed in any one of claims 1-4 wherein the inner surface of the cover plate has a reflectivity within the range 30-50%.
Claim 8
Dependent Claim
22 words
A pressure sensor as claimed in claim 6, wherein the inner surface of the diaphragm has a reflectivity within the range 80-95%.
Claim 9
Dependent Claim
49 words
A pressure sensor as claimed in any one of the preceding claims in which the width of the cavity between the inner surfaces of the diaphragm and the cover plate in the absence of any elevated or reduced pressure applied to the diaphragm, lies within the range 0.3-1 micron.
Claim 10
Dependent Claim
35 words
A pressure sensor as claimed in any one of the preceding claims, having a collimating lens adapted to receive light from an optical fibre and to supply it to the cavity through the cover plate.
Claim 11
Dependent Claim
35 words
A pressure sensor as claimed in any one of the preceding claims having a reference chamber of larger volume than the cavity, the reference chamber and the cavity being in fluid communication with each other.
Claim 12
Dependent Claim
23 words
A pressure sensor as claimed in claim 10 wherein the interconnected reference chamber and cavity are sealed against fluid exchange with their environment.
Claim 13
Dependent Claim
54 words
An optical pressure sensing system comprising a light source, a pressure sensor as claimed in any one of the preceding claims, an optical fibre linking the source to the sensor, a detector for one or more selected wavelengths within the light source waveband(s), and an output optical fibre linking the sensor to the detector.
Claim 14
Independent Claim
196 words
A method of manufacturing a pressure sensor, comprising the steps of providing a diaphragm preform of resilient material, having a first planar surface on one side and a second planar surface on the other, defining a diaphragm portion of the first surface with a collar portion extending around its periphery, etching the first surface to a substantially constant depth throughout its diaphragm portion and providing the etched diaphragm portion with a reflective inner surface, causing the etched diaphragm portion to be of a thickness which is flexible under application of the pressure thereto, providing a transparent cover plate with at least a portion having a reflective surface, securing the collar portion to the cover plate with the two reflective surfaces opposed thereby to form a reflective Fabry Perot cavity with the transparent cover plate enabling light to enter and escape from the cavity, and adapting the sensor to receive the pressure to be sensed on the outer surface of the diaphragm being the diaphragm surface remote from the cavity whereby pressure applied to said outer surface shall cause flexing of the diaphragm and consequential variation in the Fabry Perot interference according to changes in that pressure.
Claim 15
Independent Claim
196 words
A method of manufacturing a pressure sensor, comprising the steps of providing a diaphragm preform of resilient material, having a first planar surface on one side and a second planar surface on the other, defining a diaphragm portion of the first surface with a collar portion extending around its periphery, etching the first surface to a substantially constant depth throughout its diaphragm portion and providing the etched diaphragm portion with a reflective inner surface, causing the etched diaphragm portion to be of a thickness which is flexible under application of the pressure thereto, providing a transparent cover plate with at least a portion having a reflective surface, securing the collar portion to the cover plate with the two reflective surfaces opposed thereby to form a reflective Fabry Perot cavity with the transparent cover plate enabling light to enter and escape from the cavity, and adapting the sensor to receive the pressure to be sensed on the outer surface of the diaphragm being the diaphragm surface remote from the cavity whereby pressure applied to said outer surface shall cause flexing of the diaphragm and consequential variation in the Fabry Perot interference according to changes in that pressure.
References Cited (Backward Citations)
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