Correlating fiber optical measuring device

Claim 2

A fiber optical measuring device for measuring, at a measurement point, at least one parameter of an object comprising: a transducer unit at the measuring point having at least one optical transducer filter with a response spectrum subjected to wavelength displacement by said at least one parameter to be measured, an evaluating unit separated from the transducer unit, said evaluating unit including at least one source of incident light and an optical detector arrangement for analyzing light emanating from the transducer unit, and at least one light conductor for feeding incident light to the transducer unit and for feeding light emanating from said at least one optical transducer filter to the evaluating unit, wherein the detector arrangement includes at least one optical detector filter, means to subject the response spectrum thereof to wavelength displacement by the light emanating from said at least one optical transducer filter and means to measure the correlation between the spectra of a transducer filter and a corresponding detector filter to determine the spectral condition of the said transducer filter and thus determine the magnitude of the at least one parameter being measured.

Claim 3

A measuring device as claimed in claim 1, in which said transducer filter and said detector filter are both transmission filters.

Claim 4

A measuring device as claimed in claim 1, in which said transducer filter and said detector filter are both reflection filters.

Claim 5

A measuring device according to claim 1, in which the transducer unit and the detector arrangement include optical filters which are matched pairwise, so that a transducer filter corresponds to a detector filter with a corresponding spectrum structure within at least part of the spectrum thereof.

Claim 6

A measuring device according to claim 1, comprising two or more transducer filters having non-identical optical characteristics.

Claim 7

A device according to claim 4, in which each parameter to be measured produces a wavelength displacement of the spectrum of a corresponding optical transducer filter, and the evaluating electronic unit comprises means for wavelength displacement of the detector filter, and the detector signal from a photo-detector of the detector arrangement, as a function of the wavelength displacement of the detector filter, is arranged to be supplied to computing electronic equipment for analysis of the correlation between the spectra of the transducer and detector filters.

Claim 8

A measuring device according to claim 5, in which said transducer filters have differently varying spectral curves with respect to wavelength, and said transducer filters are arranged to be influenced by said parameters to be measured by at least one parameter per filter, and that demultiplexing of said parameters to be measured is arranged to be carried out by a correlation process with one detector filter for each transducer filter.

Claim 9

A measuring device according to claim 1, wherein said transducer unit further includes means for varying the temperature of an interference-based filter to vary the optical wavelength thereof to obtain said wavelength displacement of the filter spectrum.

Claim 10

A measuring device according to claim 1, wherein said evaluating unit further includes means for turning an interference-based filter to obtain said wavelength displacement.

Claim 11

A measuring device according to claim 1, wherein said transducer unit further includes means for causing an electric field to influence the optical wavelength of an electro-optical layer in a filter of the interference type to obtain said wavelength displacement.

Claim 12

A measuring device according to claim 1, wherein said transducer unit further includes means for causing a magnetic field to influence the optical wavelength of a magneto-optical layer in a filter of the interference type.

Claim 13

A measuring device according to claim 1, wherein said transducer unit further includes means for causing a mechanical modulation of the optical wavelength in a filter of the interference type to obtain said wavelength displacement.

Claim 14

A measuring device according to claim 12, in which the mechanical modulation is obtained by means of at least one piezo-electric modulator.

Claim 15

A measuring device according to claim 1, wherein said transducer unit further includes means for causing temperature to influence the position, with respect to wavelength, of the absorption spectrum in an absorption filter to obtain said wavelength displacement.

Claim 16

A measuring device according to claim 1, wherein said transducer unit further includes means for causing pressure to influence the position, with respect to wavelength, of the absorption spectrum in an absorption filter to obtain said wavelength displacement.

Claim 17

A fiber optical measuring device comprising: a transducer unit at the measuring point having at least one optical transducer filter with a response spectum subjected to wavelength displacement by a parameter to be measured, an evaluating unit separated from the transducer unit, said evaluating unit including at least one source of incident light and an optical detector arrangement for analyzing light emanating from said at least one optical transducer filter, and at least one light conductor for feeding incident light to the transducer unit and for feeding light emanating from said at least one optical transducer filter to the evaluating unit, said detector arrangement including at least one photo-detector arranged to sense the light emanating from said at least one optical transducer filter after this light has impinged upon at least one optical spectral filter within the detector arrangement, and further including means for wavelength displacement of the spectrum of said at least one optical spectral filter, which is a measure of the parameter being measured, said photo-detector measuring the correlation between the spectrum of the transducer filter and of the detector filter as the spectrum of the detector filter is adjusted, that is, d(F.sub.D)=∫F.sub.G (λ)·F.sub.D (λ)·dλ, where F G (λ) and F D (λ) are the spectra of the transducer filter and the detector filter, respectively, and that the correlation values (d(F D ) in the case of one or more spectral distributions of the detector filter are used as a measure of the condition of the transducer filter and thus of the parameter being measured.

Claim 18

A fiber optical measuring device comprising: a transducer unit at the measuring point having at least one optical transducer filter with a response spectum subjected to wavelength displacement by a parameter to be measured, an evaluating unit separated from the transducer unit, said evaluating unit including at least one source of incident light and an optical detector arrangement for analyzing light emanating from said at least one optical transducer filter, and at least one light conductor for feeding incident light to the transducer unit and for feeding light emanating from said at least one optical transducer filter to the evaluating unit, said detector arrangement including at least one photo-detector arranged to sense the light emanating from said at least one optical transducer filter after this light has impinged upon at least one optical spectral filter within the detector arrangement, and further including means for wavelength displacement of the spectrum of said at least one optical spectral filter, which is a measure of the parameter being measured, said photo-detector measuring the correlation between the spectrum of the transducer filter and of the detector filter as the spectrum of the detector filter is adjusted, that is, d(F.sub.D)=∫F.sub.G (λ)·F.sub.D (λ)·dλ, where F G (λ) and F D (λ) are the spectra of the transducer filter and the detector filter, respectively, and that the correlation values (d(F D ) in the case of one or more spectral distributions of the detector filter are used as a measure of the condition of the transducer filter and thus of the parameter being measured.

Claim 19

A measuring device according to claim 16, wherein the output signal of said photo-detector is arranged to be measured as a function of at least one parameter, of the spectrum (F D ) of the detector filter, and that said evaluating electronic unit further includes means for calculating different parameters and the relative distances between, firstly, different correlation peaks, secondly, different correlation minima, and thirdly, correlation peaks and correlation minima, and that the thus obtained parameter values of the correlation signals with respect to different parameter values of the spectrum (F D ) of the detector filter are used to calculate the spectrum (F G ) of the transducer filter.