EP0455461A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Light measuring apparatus and method
Assignee: Prysmian Cables and Systems Ltd
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Filing: 1991-04-30
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Granted: —
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Expires: 2011-04-30
Abstract
Abstract A single light source (10) provides broadband light for an intensity-based sensing element (12). Broadband light reflected from the sensing element is split and passes through two narrowband filters (16, 17) having passbands which cover different wavelength ranges. The two narrowband optical signals are detected by two detectors (20, 21) which generate two signals (A, B). A processing unit (22) divides the two signals to give a ratiometric determination of the measurand, thereby largely compensating for extraneous variations in the signals.
Inventors
- 👤 Paul Laurence Scrivener
- 👤 Andrew Paul Appleyard
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 08:24
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/26; G01D5/268
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
101 words
A method of measurement in an intensity based optical sensing system, comprising the steps of connecting an input of a sensing element to a single source of broadband light, connecting an output of the sensing element to two narrowband optical filters having passbands covering different wavelength ranges, and processing the two signals received from the sensing element via the two filters to produce a ratioed determination of the measurand, and further comprising the step of selecting the filters to have their respective passbands on the same side of the peak of the emission intensity spectrum of the source as each other.
Claim 2
Dependent Claim
25 words
A method as claimed in claim 1 and further including selecting the filters to have no overlap in the wavelength ranges of their respective passbands.
Claim 3
Dependent Claim
45 words
A method as claimed in claim 1 or claim 2 and further including selecting the filters to have the wavelength ranges of their respective passbands closely adjacent each other and in a middle region of either the upwardly or downwardly sloping sections of the spectrum.
Claim 4
Independent Claim
26 words
A method as claimed in any preceding claim wherein the connection of the input and output of the sensing element is by a single optical fibre.
Claim 5
Independent Claim
29 words
A method as claimed in any one of claims 1 to 3 wherein the connection of the input and output of the sensing element is by separate optical fibres.
Claim 6
Dependent Claim
65 words
A method as claimed in claim 4 and comprising the step of connecting the single optical fibre leading from the sensing element to a two way splitter with one way leading to the source and the other way leading to the two filters, and avoiding a connection or other refractive index mismatch in the said single optical fibre between the splitter and the sensing element.
Claim 7
Dependent Claim
102 words
Measuring apparatus comprising an intensity-based optical sensing element, first optical transmission means for connecting an input of the sensing element to a single source of broadband light, second optical transmission means for connecting an output of the sensing element to two narrowband optical filters having passbands covering different wavelength ranges, and processing means for producing a ratioed determination of the measurand from the two signals received from the sensing element via the two filters, wherein the filters are selected to have their respective passbands on the same side of the peak of the emission intensity spectrum of the source as each other.
Claim 8
Dependent Claim
33 words
Apparatus as claimed in claim 7 wherein the connection of the input and output of the sensing element comprises a single optical fibre which is common to both first and second transmission means.
Claim 9
Dependent Claim
43 words
Apparatus as claimed in claim 8 wherein said common single optical fibre leads from the sensing element to a two way splitter and there is no connection or other refractive index mismatch in the optical fibre between the splitter and the sensing element.
Claim 10
Dependent Claim
17 words
Apparatus as claimed in claim 7 wherein the first and second transmission means comprise separate optical fibres.
References Cited (Backward Citations)
GB1461387A
Cited
GB2105460A
Cited
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