Method and arrangement for measuring the optical absorptions of gaseous mixtures
DC CAFCFirst Claim
1. An arrangement for measuring a gas of interest by its optical absorption characteristics, comprising:
- a source of electromagnetic radiation;
means for conditioning such electromagnetic radiation such that it passes through such gas of interest;
means for electrically modulating such electromagnetic radiation that has passed through such gas of interest, said modulating means including a birefringent etalon having associated therewith, .Iadd.a transmission spectrum having .Iaddend.a periodic spacing equal to the periodicity of the absorption lines associated with such gas of interest;
said modulating means being further effective for varying an electrical field applied to said birefringent etalon between first and second predetermined strengths such that the periodic transmission spectrum is shifted between .[.spectra.]. .Iadd.a spectrum .Iaddend.which .[.coincide.]. .Iadd.coincides .Iaddend.substantially with such absorption lines and .[.spectra.]. .Iadd.a spectrum .Iaddend.which .[.fall.]. .Iadd.falls .Iaddend.between such absorption lines; and
means for detecting at least the intensity of such periodic transmission spectra following passage through such gas of interest and determining therefrom at least an amount of such gas of interest present.
0 Assignments
Litigations
0 Petitions
Accused Products
Abstract
A gas analyzer arrangement for detecting the presence or quantity of a gas of interest includes a source of electromagnetic radiation for directing a light beam through a light conditioning device such that the light beam is collimated into a parallel beam of light. The conditioned light beam is then directed through a gas sample cell which contains a sample of the gas of interest. The gas of interest has associated therewith, vibrational rotational absorption lines specific to that gas and which are effective for altering the light beam according to the absorption characteristics thereof. The altered light beam is then directed to a birefringent etalon device which has been sized specifically to match those absorption lines of the gas of interest. An electro-optical modulator device associated with the birefringent etalon modulates the absorption lines between the transmission spectra maxima and a point between the transmission spectra maxima so that an absorption ratio can be utilized to determine the presence or quantity of the gas of interest.
26 Citations
23 Claims
-
1. An arrangement for measuring a gas of interest by its optical absorption characteristics, comprising:
-
a source of electromagnetic radiation; means for conditioning such electromagnetic radiation such that it passes through such gas of interest; means for electrically modulating such electromagnetic radiation that has passed through such gas of interest, said modulating means including a birefringent etalon having associated therewith, .Iadd.a transmission spectrum having .Iaddend.a periodic spacing equal to the periodicity of the absorption lines associated with such gas of interest; said modulating means being further effective for varying an electrical field applied to said birefringent etalon between first and second predetermined strengths such that the periodic transmission spectrum is shifted between .[.spectra.]. .Iadd.a spectrum .Iaddend.which .[.coincide.]. .Iadd.coincides .Iaddend.substantially with such absorption lines and .[.spectra.]. .Iadd.a spectrum .Iaddend.which .[.fall.]. .Iadd.falls .Iaddend.between such absorption lines; and means for detecting at least the intensity of such periodic transmission spectra following passage through such gas of interest and determining therefrom at least an amount of such gas of interest present. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
-
9. and a collimating mirror. 12. An arrangement for measuring a gas of interest by its optical absorption characteristics, said measuring arrangement comprising:
-
a source of electromagnetic radiation; means for directing such electromagnetic radiation through such gas of interest; a first light signal, emerging from passage through such gas of interest, has associated therewith, periodic transmission spectra representative of the absorption lines of such gas of interest; an interferometric device receptive of said first light signal and having associated therewith, .Iadd.a transmission spectrum having .Iaddend.a periodic spacing equal to the periodicity of the absorption lines of such gas of interest; means for varying an applied electric field of first and second predetermined strengths to said interferometric device so as to modulate such periodic spacing of said interferometric device between .Iadd.a .Iaddend.transmission .[.spectra.]. .Iadd.spectrum .Iaddend.which substantially .[.coincide.]. .Iadd.coincides .Iaddend.with such absorption lines and .Iadd.a .Iaddend.transmission .[.spectra.]. .Iadd.spectrum .Iaddend.which .[.fall.]. .Iadd.falls .Iaddend.between such absorption lines; and
,means for detecting at least an amount of such gas of interest as a function of the intensity of such periodic transmission spectra following
-
- 12. first light signal being acted upon by said detecting means. 15. A gas measurement arrangement as set forth in claim 12 wherein said interferometric device .[.is.]. .Iadd.includes .Iaddend.a first birefringent etalon having a first path length determinative of such
-
15. than such respective periodic spacings taken individually. 18. A method for measuring a gas of interest by its optical absorption characteristics, said measuring method comprising the steps of:
-
directing a light beam through a quantity of such gas of interest such that a light signal representative of the absorption lines of the gas of interest is generated thereby; passing said light signal through a birefringent etalon device which has associated therewith, .Iadd.a transmission spectrum having .Iaddend.a periodic spacing substantially equivalent to such absorption lines associated with such gas of interest; applying an electrical field at two distinct field strengths to the birefringent etalon to modulate its transmission spectra from wavelengths which substantially coincide with the absorption lines of the gas of interest and wavelengths which fall between such absorption .[.liens.]. .Iadd.lines.Iaddend.; and determining at least an amount of such gas of interest as a function of the relationship .Iadd.between .Iaddend.such spectra which coincide with such absorption lines and such spectra which fall between such absorption - View Dependent Claims (13)
-
-
17. etalon..]..Iadd.25. An arrangement for measuring a property of a gas by its optical absorption characteristics, comprising:
-
source of electromagnetic radiation; means for directing the electromagnetic radiation through the gas; an interferometric device filtering the electromagnetic radiation with a transmission spectrum having one or more spectral maxima, the interferometric device including an electro-optical element; means for applying an electric field to the electro-optical element; means for varying the electric field between two predetermined field strengths such that the spectral maxima shift to exhibit differing degrees of coincidence with absorption lines associated with the gas; and means for detecting an intensity of the electromagnetic radiation following passage through the gas and through the interferometric device, and
-
-
18. determining therefrom a property of the gas..Iaddend..Iadd.26. The arrangement as recited in claim 25, wherein the electro-optical element is a birefringent etalon which has associated therewith the transmission spectrum, and wherein the spectral maxima shift between spectral maxima which substantially coincide with the absorption lines and spectral maxima which substantially fall between the absorption lines..Iaddend..Iadd.27. The arrangement as recited in claim 26, the inteferometric device further including an input polarizer and an output polarizer, and wherein the birefringent etalon is disposed between the input and output polarizer..Iaddend..Iadd.28. The arrangement as recited in claim 27, further comprising:
a bandpass filter removing certain known portions of he electromagnetic radiation prior to detection of the electromagnetic radiation by the detecting means..Iaddend..Iadd.29. The arrangement as recited in claim 25, wherein the electro-optical element comprises an electro-optical modulator element constructed of a material having a high electro-optical coefficient, the interferometric device further including a birefringent etalon which is sized so as to substantially achieve the filtering - View Dependent Claims (14, 16)
-
19. capability of the interferometric device..Iaddend..Iadd.30. The arrangement as recited in claim 29, wherein the birefringent etalon is constructed separately and distinctly from the electro-optical modulator element such that the filtering capability can be selectively altered to provide detection of an alternate gas by substitution of an alternate sized birefringent etalon for the first-named birefringent etalon, such substitution being done independent of the electro-optical modulator element..Iaddend..Iadd.31. The arrangement as recited in claim 25, wherein the electro-optical element includes a first and second electro-optical modulator element, the electro-optical modulator elements being oriented relative to each other such that birefringence of the combination is less than birefringence of the first electro-optical modulator element and less than birefringence of the second electro-optical modulator element, the electric field being applied to at least one of the electro-optical modulator elements..Iaddend..Iadd.32. The arrangement as recited in claim 25, wherein the electro-optical element comprises an electro-optical modulator element, the interferometric device further including:
-
a first birefringent etalon having a first path length determinative of a second transmission spectrum having spectral maxima with a first periodic spacing; a second birefringent etalon having a second patch length determinative of a third transmission spectrum having spectral maxima with a second periodic spacing; and a first, second, and third polarizer, the first birefringent etalon positioned between the first and second polarizers and the second birefringent etalon positioned between the second and third polarizers; wherein the second birefringent etalon is disposed relative to the first birefringent etalon such that their respective transmission spectra are combined to yield the first-mentioned transmission spectrum of the
-
-
20. interferometric device..Iaddend..Iadd.33. A method for measuring a property of a gas by its optical absorption characteristics, comprising the steps of:
-
directing light from a source of light through a quantity of the gas such that absorption lines of the gas modify the light; passing light from the source of light through an interferometric device which has associated therewith a transmission spectrum with one or more spectral maxima, the interferometric device including an electro-optical element; an electric field to the electro-optical element; varying the electric field between two predetermined field strengths to shift the transmission spectrum between spectral maxima which have differing degrees of coincidence with absorption lines associated with the gas; detecting the light after passage through the gas and through the interferometric device; and calculating at least an amount of the gas as a function of the detected
-
-
21. light..Iaddend..Iadd.34. The method as recited in claim 33, wherein the passing through step includes polarizing the light prior to the passing of the light through the electro-optical element, the method further comprising the step of:
conditioning the light such that certain known portions of the light are
-
22. removed prior to the detecting step..Iaddend..Iadd.35. An arrangement for measuring a property of a gas by its optical absorption characteristics, comprising:
-
a source of electromagnetic radiation; means for directing the electromagnetic radiation through the gas; means for modulating the electromagnetic radiation, the modulating means including an electro-optical element, means for applying an electric field to the electro-optical element, and means for varying the electro field between two predetermined strengths to effect the modulation; an interferometric device receptive of the electromagnetic radiation and having associated therewith a first and second transmission spectrum each having spectral maxima, the spectral maxima of the second transmission spectrum having a differing degree of coincidence with absorption lines of the gas than spectral maxima of the first transmission spectrum; and means for detecting a property of the gas as a function of an intensity of the electromagnetic radiation following passage through the gas, the
-
-
23. modulating means, and the interferometric device..Iaddend..Iadd.36. The arrangement as recited in claim 35, wherein the interferometric device includes a compound Fabry-Perot birefringent etalon device having associated therewith a first index of refraction and a path length which determine, in conjunction, the first transmission spectrum..Iaddend..Iadd.37. The arrangement as recited in claim 36, wherein the compound Fabry-Perot birefringent etalon device further has associated therewith a second index of refraction which, in conjunction with the path length, determines the second transmission spectrum..Iaddend..Iadd.38. The arrangement as recited in claim 37, wherein the second index of refraction is selected such that the spectral maxima of the second transmission spectrum occur at a wavelength which essentially avoids interference from other gases..Iaddend..Iadd.39. The arrangement as recited in claim 36 wherein the compound Fabry-Perot birefringent etalon has applied on opposing ends disposed along the direction of light propagation through the gas measurement arrangement, a partially reflective surface coating..Iaddend.
Specification