US3915573A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Variable-frequency interferometer resonance filter
Assignee: Hewlett Packard GmbH Germany
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Filing: 1974-02-04
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Granted: 1975-10-28
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Expires: 1994-02-04
Abstract
Abstract An apparatus for measuring the absorption index of a flowing liquid includes a measuring cell and a reference cell. Each cell is formed in the space between and confined by the reflectors of an interferometer of the spherical Perot-Fabry type. The cells are located in parallel in a common body and by means of a common piezo-electric tuning element the distance and thus the resonance frequency of each pair of reflectors can be uniformly varied in order to establish the resonance condition for each liquid in the cells. The voltage supplied to the piezo-electric tuning element for establishing the resonance condition is indicative of the relative absorption index of the liquid under test. The reference cell serves to compensate for unwanted disturbances by changes in temperature, in the flow rate and the like.
Inventors
- 👤 Dieter B Knoll
- 👤 Alfons Schmid
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 11:07
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/41; G01N21/45
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
295 words
A variable frequency interferometric resonance filter comprising: a reference cell having a resonant chamber with a pair of reflectors forming a first Perot-Fabry type interferometer and adapted to receive a flowing medium therebetween; a measurement cell having a resonant chamber with a pair of reflectors forming a second Perot-Fabry type interferometer and adapted to receive a flowing medium therebetween; a source of monochromatic light optically connected to the reference and measurement cells for supplying light to each cell; inlet and outlet means connected to the reference and measurement cells for conducting the flowing media into and out of the reference and measurement cells respectively; a common piezoelectric element connected to the pairs of reflectors for establishing and uniformly varying the distance between the reflectors of each pair of reflectors; generator means connected to the piezoelectric element for applying a signal thereto for varying the distance between the reflectors of each pair of reflectors in a predetermined manner; first detector means connected to the reference cell and second detector means connected to the measurement cell for responding to and giving output signals indicative of the occurrence of interference fringes from each of the reference and measurement cells caused by the variation of the distance between the reflectors of each pair of reflectors effected by the piezoelectric element; and signal processing means connected to the first and second detector means and to the generator means for directly measuring the difference in time between the occurrence of the interference fringes from the reference and measurement cells for giving an indication of the distances between the pairs of reflectors in the reference and measurement cells corresponding to the occurrence of said interference fringes to give a measure of the optical characteristics of a medium flowing through the measurement cell.
Claim 2
Dependent Claim
295 words
A variable frequency interferometric resonance filter comprising: a reference cell having a resonant chamber with a pair of reflectors forming a first Perot-Fabry type interferometer and adapted to receive a flowing medium therebetween; a measurement cell having a resonant chamber with a pair of reflectors forming a second Perot-Fabry type interferometer and adapted to receive a flowing medium therebetween; a source of monochromatic light optically connected to the reference and measurement cells for supplying light to each cell; inlet and outlet means connected to the reference and measurement cells for conducting the flowing media into and out of the reference and measurement cells respectively; a common piezoelectric element connected to the pairs of reflectors for establishing and uniformly varying the distance between the reflectors of each pair of reflectors; generator means connected to the piezoelectric element for applying a signal thereto for varying the distance between the reflectors of each pair of reflectors in a predetermined manner; first detector means connected to the reference cell and second detector means connected to the measurement cell for responding to and giving output signals indicative of the occurrence of interference fringes from each of the reference and measurement cells caused by the variation of the distance between the reflectors of each pair of reflectors effected by the piezoelectric element; and signal processing means connected to the first and second detector means and to the generator means for directly measuring the difference in time between the occurrence of the interference fringes from the reference and measurement cells for giving an indication of the distances between the pairs of reflectors in the reference and measurement cells corresponding to the occurrence of said interference fringes to give a measure of the optical characteristics of a medium flowing through the measurement cell.
Claim 3
Dependent Claim
22 words
A resonance filter as in claim 1 wherein each Perot-Fabry type interferometer has concave, cup-shaped reflectors with the same radius of curvature.
Claim 4
Dependent Claim
20 words
A resonance filter as in claim 2 wherein the reference and measurement cells are enclosed by a thermally insulating material.
Claim 5
Dependent Claim
20 words
A resonance filter as in claim 2 wherein the reference and measurement cells are enclosed by an inert, synthetic material.
Claim 6
Dependent Claim
20 words
A resonance filter as in claim 4 wherein the material is selected from the group consisting of polytetrafluoroethylene and polytrifluoroethylene.
Claim 7
Dependent Claim
86 words
A resonance filter as in claim 2 including a body wherein each of the reference and measurement cells and the associated inlet and outlet means comprise a Z-shaped bore in the body, with the middle legs of the Z-shaped bores being parallel and each such middle leg defining one of the reference and measurement cells, with the outer legs of the Z-shaped bores defining the inlet and outlet means, and with the Z-shaped bores oriented 180* apart with respect to each other about their middle legs.
Claim 8
Dependent Claim
91 words
A resonance filter as in claim 6 including a first and a second end plate and wherein: the body is cylindrical in shape; the first end plate holds one of the reflectors from each pair of reflectors and is rigidly fastened to the body; the second end plate holds the other of the reflectors from each pair of reflectors and is resiliently fastened to the body; and the piezoelectric element is in the form of a hollow cylinder surrounding the body and is connected to the first and second end plates.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-10-27 | 1979-04-28 | 1979-10-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-27 | 1983-04-28 | 1983-10-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-27 | 1987-04-28 | 1987-10-28 | $7700.00 | Window Closed / Lapsed |