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US 7,921,693 B2Granted
Photo-acoustic spectrometer apparatus
AssigneeKoninklijke Philips Electronics N.V.
InventorMaarten Marinus Johannes Wilhelm Van Herpen
Life of this patent
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Abstract
A photo acoustic detection cell (6) is located within the optical cavity (3) of a cavity enhanced absorption spectroscopy apparatus (3,4,5). When a sample in the cell (6) absorbs radiation from a pulsed radiation beam coupled into the cavity (3) pressure waves are generated that are detected by a microphone (9). A detected signal (10) output by the microphone (9) may be processed to determine a value for the concentration of an absorber in the sample.
Claims15
A spectrometer apparatus comprising:
- a pulsed radiation beam generator for generating a pulsed radiation beam of a pre-determined radiation wavelength;
- an optical cavity having a plurality of cavity modes, each cavity mode having a cavity mode wavelength;
- a dithering arrangement for dithering the radiation wavelength of the pulsed radiation beam and the plurality of cavity mode wavelengths such that the pulsed radiation beam quasi continuously couples into the optical cavity;
- a photo-acoustic cell located within the optical cavity for containing a sample to be analyzed;
- and
- a detector for detecting pressure waves generated in the photo-acoustic cell when the sample absorbs radiation from the pulsed radiation beam and for producing a detector output signal that is processable to determine a value for a concentration of an absorber in the sample.
3 more elements
A spectroscopy method comprising:
- generating a pulsed radiation beam of predetermined wavelength and directing the pulsed radiation beam to an optical cavity having a plurality of cavity modes, each cavity mode having a corresponding cavity mode wavelength;
- dithering the radiation wavelength of at least the pulsed radiation beam such that the pulsed radiation beam quasi continuously couples into the optical cavity;
- detecting pressure waves generated in a photo-acoustic cell located within the optical cavity when a sample in the photo-acoustic cell absorbs radiation from the pulsed radiation beam to generate a detected signal;
- and
- processing the detected signal to determine a value for a concentration of an absorber in the sample.
2 more elements
A spectroscopy method comprising:
- generating a pulsed radiation beam of predetermined wavelength and directing the pulsed radiation beam to an optical cavity having a plurality of cavity modes, each cavity mode having a corresponding cavity mode wavelength;
- dithering at least one of the radiation wavelength of the pulsed radiation beam and the plurality of cavity mode wavelengths such that the pulsed radiation beam quasi continuously couples into the optical cavity;
- detecting pressure waves generated in a photo-acoustic cell located within the optical cavity when a sample in the photo-acoustic cell absorbs radiation from the pulsed radiation beam to generate a detected signal;
- processing the detected signal to determine a value for a concentration of an absorber in the sample;
- and
- generating a compensation signal for use in compensating the absorption signal for variations in the intensity of the pulsed radiation beam, wherein generating the compensation signal comprises locating a beam splitter between a source of the pulsed radiation beam and the optical cavity to direct a fraction of the radiation from the source to a radiation detector to output the compensation signal.
3 more elements
Dependencies are inferred from the claim text.