Acoustic resonance phase locked photoacoustic spectrometer
AssigneeSouthwest Sciences Incorporated
InventorsJeffrey S. Pilgrim, David S. Bomse, Joel A. Silver
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Abstract
A photoacoustic spectroscopy method and apparatus for maintaining an acoustic source frequency on a sample cell resonance frequency comprising: providing an acoustic source to the sample cell to generate a photoacoustic signal, the acoustic source having a source frequency; continuously measuring detection phase of the photoacoustic signal with respect to source frequency or a harmonic thereof; and employing the measured detection phase to provide magnitude and direction for correcting the source frequency to the resonance frequency.
Claims17
A photoacoustic spectroscopy method for maintaining an acoustic source frequency on a sample cell resonance frequency, the method comprising the steps of:
- providing an acoustic source to the sample cell to generate a photoacoustic signal, the acoustic source having a source frequency;
- continuously measuring detection phase of the photoacoustic signal with respect to a frequency selected from the group consisting of the source frequency and harmonics thereof;
- and
- employing the measured detection phase to provide magnitude and direction for correcting the source frequency to the resonance frequency.
A photoacoustic spectroscopy apparatus for maintaining an acoustic source frequency on a sample cell resonance frequency, said apparatus comprising:
- means for providing an acoustic source to the sample cell to generate a modulated photoacoustic signal, said acoustic source having a source frequency;
- means for continuously measuring detection phase of the photoacoustic signal with respect to a frequency selected from the group consisting of the source frequency and harmonics thereof;
- and
- means for employing the measured detection phase to provide magnitude and direction for correcting the source frequency to the resonance frequency.
An acoustic resonance frequency locked photoacoustic spectrometer comprising:
- a source generating a photoacoustic signal, said source having a source frequency;
- and
- a lock-in amplifier employing a detection phase of the photoacoustic signal with respect to a frequency selected from the group consisting of source frequency and harmonics thereof,
- whereby said amplifier maintains said photoacoustic signal on a resonance frequency of a sample cell.
Dependencies are inferred from the claim text.