Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1991-05-15
1992-07-07
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356352, 73705, G01D 534
Patent
active
051285371
ABSTRACT:
A device for optically measuring a pressure difference in a medium by means of a Fabry-Perot interferometer, comprises a transparent plate and a diaphragm block connected to the transparent plate, the diaphragm block comprising a substrate, a measuring diaphragm formed along the inner surface of the substrate, and a spacer separating the inner surface of the transparent plate and the inner surface of the substrate. A first planar mirror is disposed on the inner surface of the plate and a second planar mirror is disposed on the inner surface of the measuring diaphragm so that they constitute the Fabry-Perot interferometer. The measuring diaphragm is shiftable by a distance (H) in response to a pressure difference (.delta.p) exerted on inner and outer surfaces of the measuring diaphragm whereby the optical length (L) of the Fabry-Perot interferometer changes as a function of the pressure difference (.delta.p). The substrate includes a depression on one side only so that the material remaining under the depression is of a predetermined thickness and comprises the measuring diaphragm. Since the measuring diaphragm constitutes a portion of the substrate and is a continuation of the crystalline structure of the substrate, there are no mechanical stresses at the joining points of the substrate and the measuring diaphragm. Preferably, the measuring diaphragm constitutes a doped layer of the substrate and serves as an etching barrier for the substrate.
REFERENCES:
patent: 4682500 (1987-07-01), Uda
patent: 4772786 (1988-09-01), Langdon
patent: 4926696 (1990-05-01), Haritonidis et al.
patent: 4933545 (1990-06-01), Saaski et al.
patent: 4983824 (1991-01-01), Saaski et al.
Landis & Gyr Betriebs AG
Nelms David C.
Shami Khaled
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