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US 5,512,757 AGranted
Spectrophotometer and optical system therefor
AssigneeRosemount Analytical Inc.
InventorsCarl N. Cederstrand, Sharam M. Salimian, Rolf W. Siemon
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AssigneeRosemount Analytical Inc.
InventorsCarl N. Cederstrand, Sharam M. Salimian, Rolf W. Siemon
Estimating the term…
The photometer of the present invention includes an optical system in which an emission beam generated by pulsed ultra violet radiation from a source is split into a sample beam and a reference interference beam by spectrally selective mirrors arranged in series. These mirrors reflect a beam having a wavelength range corresponding to an absorption wavelength of the gas to be detected onto one solid state detector and to pass a beam to a second spectrally selective mirror where a beam having second range of wave lengths corresponding to an interfering gas is reflected onto a second solid state detector. This second beam serves to measure the interfering gas and also as an imperfect reference channel. In a preferred embodiment the radiation from the source is split prior to entering the sample cell. One beam is directed through an optical path which avoids the sample cell but which is otherwise identical to the optical path described above, including series arranged spectrally selective mirrors to be further split the beam into two beams having wavelength ranges corresponding to the wavelength ranges of the sample and reference gases. These beams are directed to solid state detectors and the signals derived therefrom are combined with a second set of similar signals derived from the sample and reference beams which have passed through the sample cell.
In a spectrophotometer of the type having a sample cell for containing sample to be analyzed, an emission source for directing radiation through said sample cell, filter means in the path of said radiation for eliminating wavelengths shorter than a designated wavelength, detectors for detecting radiation of selected wavelengths emitted from said sample cell and for producing an electronic signal in response to the detected radiation and means for measuring said electronic signal from said detectors as an indicator of the quantities of sought for component in said sample, the invention comprising:
An emission spectrophotometer comprising a source group, a sample cell, a detector group and a comparison group, said source group including an emitter of ultra violet radiation, filter means in the path of said radiation for eliminating wavelengths shorter than a designated wavelength and a beam splitter dividing the emitted radiation into a first and a second beam, said first beam being directed through said sample cell and said second beam being directed to said comparison group, said detector group including a first and a second spectrally selective mirror disposed in series along the optical axis of said first beam, said first spectrally selective mirror reflecting incident source group radiation from said sample cell below a selected wavelength to a solid state detector and transmitting radiation in excess of said selected wavelength, said second spectrally selective mirror reflecting transmitted radiation from said first spectrally selective mirror below a second selected wavelength to a solid state detector, said comparison group including a first and a second spectrally selective mirror disposed in series along the optical axis of said second beam, said first and second spectrally selective mirrors of said comparison group corresponding in optical characteristics to said first and second spectrally selective mirrors of said detector group, and circuit means for integrating the solid state detector signals thereby to derive a signal directly related to the quantity of a gas being detected which has been compensated for interferant gases and source aberrations.
In a spectrophotometer of the type having a sample cell for containing sample to be analyzed, an emission source for directing radiation through said sample cell, at least two detectors for detecting radiation of different selected wavelengths emitted from said sample cell and for producing an electronic signal in response to the detected radiation and means for measuring and integrating the electronic signal from each detector as an indicator of the quantities of sought for component in said sample, the invention comprising an improved optical system including:
Dependencies are inferred from the claim text.