Measuring gaseous oxygen with U.V. absorption

Claim 2

An instrument for measuring the concentration of oxygen in a sample containing water vapor and other interfering gases comprising, means providing ultraviolet light of at least two different wavelengths, one of said wavelengths being in a band that is strongly absorbed by oxygen, the other of said wavelengths being in a band that is less strongly absorbed by oxygen, both of said wavelengths being absorbed by water vapor and other interfering gases in nearly equal degree, a sample chamber through which the sample to be examined can be passed, means for alternately directing light of said first and second wavelengths from said means through said chamber, means for developing electrical signals proportional to the amount of light impinging on it, said means being mounted so as to intercept a portion of the light that passes through said chamber, and a narrow band interference filter passing said two different wavelengths of ultraviolet light and rejecting other wavelengths of ultraviolet light that are less than and greater than the two different wavelengths, said filter being in the optical path between said source and said sample chamber.

Claim 3

An instrument as set forth in claim 1 wherein said means providing ultraviolet light is a single lamp in which the emission is broadened so as to include said first and second wavelengths.

Claim 4

An instrument as set forth in claim 1 wherein said means for alternately directing the light includes an etalon filter having separated plates with opposed interior mirrored surfaces, said etalon filter having a transmission characteristic so as to pass light of the first wavelength when in a first condition and a transmission characteristic so as to pass light of a second wavelength when in a second condition.

Claim 5

Apparatus as set forth in claim 3 wherein control means are provided for causing said etalon filter to alternate between said first and second conditions,

Claim 6

An instrument as set forth in claim 4 wherein said control means includes means for changing the separation between said plates.

Claim 7

An instrument as set forth in claim 4 wherein said control means includes means for tilting said plates.

Claim 8

An instrument for measuring the concentration of oxygen flowing in a transparent tube through which a patient breathes comprising, means for alternately directing to said tube two wavelengths of ultraviolet light that are differently absorbed by oxygen, a photoelectric device mounted so as to receive the light after it has passed through said tube and develop electrical signals proportional to the amount of light so received, and means for deriving an output proportional to the alternating component of said electrical signals and an indicator of the concentration of oxygen within the tube.

Claim 9

An instrument for measuring the concentration of oxygen flowing in a transparent tube through which a patient breathes comprising, means for alternately directing to said tube two wavelengths of ultraviolet light that are differently absorbed by oxygen, a photoelectric device mounted so as to receive the light after it has passed through said tube and develop electrical signals proportional to the amount of light so received, and means for deriving an output proportional to the alternating component of said electrical signals and an indicator of the concentration of oxygen within the tube.

Claim 10

An instrument as set forth in claim 7 wherein said means for alternately directing the two wavelengths of ultraviolet light includes a discharge lamp for emmitting a broad band of ultraviolet light including said two wavelengths, and an etalon filter that can be controlled so as to pass either of the two wavelengths of light.

Claim 11

In an instrument for measuring oxygen in a patient's breath, a discharge lamp containing an element that emits ultraviolet light at a plurality of spectral wavelengths, said discharge lamp having means for broadening its emission to include bands of wavelength on either side of each said spectral emission, at least one of said bands including the wavelengths of an absorption peak of oxygen, means defining an input aperture located so as to receive light from said lamp, a lens for collimating light passing through said input aperture, means defining an output aperture, a lens for focussing collimated light from said collimating lens onto said output aperture, an etalon filter mounted between said collimating and focussing lenses so as to be traversed by the collimated light, means for adjusting said etalon filter between a condition where it passes light having a first wavelength coinciding with a wavelength in an absorption peak of oxygen and condition where it passes light of a second wavelength between the wavelengths of absorption peaks of oxygen, and a narrow band interference filter passing said first and second wavelengths of ultraviolet light and rejecting light having wavelengths outside said first and second wavelengths of light, said filter being located in the optical path between said discharge lamp and said means defining an output aperture.

Claim 12

In an instrument for measuring oxygen in a patient's breath, a discharge lamp containing an element that emits ultraviolet light at a plurality of spectral wavelengths, said discharge lamp having means for broadening its emission to include bands of wavelength on either side of each said spectral emission, at least one of said bands including the wavelengths of an absorption peak of oxygen, means defining an input aperture located so as to receive light from said lamp, a lens for collimating light passing through said input aperture, means defining an output aperture, a lens for focussing collimated light from said collimating lens onto said output aperture, an etalon filter mounted between said collimating and focussing lenses so as to be traversed by the collimated light, means for adjusting said etalon filter between a condition where it passes light having a first wavelength coinciding with a wavelength in an absorption peak of oxygen and condition where it passes light of a second wavelength between the wavelengths of absorption peaks of oxygen, and a narrow band interference filter passing said first and second wavelengths of ultraviolet light and rejecting light having wavelengths outside said first and second wavelengths of light, said filter being located in the optical path between said discharge lamp and said means defining an output aperture.

Claim 13

Apparatus for measuring the concentration of oxygen in a patient's breath comprising, a lamp providing ultraviolet light in a plurality of emission lines, said lamp being such as to broaden the emission about its normal emission lines, an input aperture mounted in the path of some of the light from said source, a collimating lens adapted to project light from said input aperture in substantially parallel paths, a detector, a focussing lens for focussing collimated light received from said collimating lens on said detector, a filter mounted in the path of said collimated light for attenuating light associated with all but one of said emission lines, filtering means mounted in the path of said collimated light that can be controlled so as to alternately pass the ultraviolet light within one broadened emission line that is strongly absorbed by oxygen and ultraviolet light within said broadened emission band that is weakly absorbed by oxygen, and a sample chamber through which a patient can breathe mounted between said filtering means and said detector.

Claim 14

Apparatus for measuring the concentration of oxygen in a patient's breath comprising, a lamp providing ultraviolet light in a plurality of emission lines, said lamp being such as to broaden the emission about its normal emission lines, an input aperture mounted in the path of some of the light from said source, a collimating lens adapted to project light from said input aperture in substantially parallel paths, a detector, a focussing lens for focussing collimated light received from said collimating lens on said detector, a filter mounted in the path of said collimated light for attenuating light associated with all but one of said emission lines, filtering means mounted in the path of said collimated light that can be controlled so as to alternately pass the ultraviolet light within one broadened emission line that is strongly absorbed by oxygen and ultraviolet light within said broadened emission band that is weakly absorbed by oxygen, and a sample chamber through which a patient can breathe mounted between said filtering means and said detector.

Claim 15

In an instrument for measuring oxygen in patient's breath, a discharge lamp containing an element that emits ultraviolet light at a plurality of spectral wavelengths, said discharge lamp having means for broadening its emission to include bands of wavelengths on either side of each said spectral emissions, at least one of said bands including the wavelengths of an absorption peak of oxygen, means defining an input aperture located so as to receive light from said lamp, a lens for collimating light received from said input aperture, means defining an output aperture, a lens for focussing collimated light from said collimating lens onto said output aperture, filtering means mounted between said collimating and focussing lenses so as to be traversed by the collimated light, means for adjusting said filtering means between a condition where it passes light having a first wavelength coinciding with a wavelength in an absorption peak of oxygen and a condition where it passes light of a second wavelength between the wavelengths of absorption peaks of oxygen, and a narrow band interference filter passing said first and second wavelengths of ultraviolet light and rejecting light having wavelengths outside said first and second wavelengths of light, said filter being located in the optical path between said discharge lamp and said means defining an output aperture.

Claim 16

In an instrument for measuring oxygen in patient's breath, a discharge lamp containing an element that emits ultraviolet light at a plurality of spectral wavelengths, said discharge lamp having means for broadening its emission to include bands of wavelengths on either side of each said spectral emissions, at least one of said bands including the wavelengths of an absorption peak of oxygen, means defining an input aperture located so as to receive light from said lamp, a lens for collimating light received from said input aperture, means defining an output aperture, a lens for focussing collimated light from said collimating lens onto said output aperture, filtering means mounted between said collimating and focussing lenses so as to be traversed by the collimated light, means for adjusting said filtering means between a condition where it passes light having a first wavelength coinciding with a wavelength in an absorption peak of oxygen and a condition where it passes light of a second wavelength between the wavelengths of absorption peaks of oxygen, and a narrow band interference filter passing said first and second wavelengths of ultraviolet light and rejecting light having wavelengths outside said first and second wavelengths of light, said filter being located in the optical path between said discharge lamp and said means defining an output aperture.