SPECTROPHONE ASSEMBLY FOR IDENTIFYING AND DETECTING MULTIPLE SPECIES

• US 20100107734A1
• Filed: 12/02/2009
• Published: 05/06/2010
• Est. Priority Date: 03/24/2004
• Status: Active Grant

• Current Assignee: Robert A. Crane
• Original Assignee: Robert A. Crane
• Inventors: Crane, Robert A.
• Granted Patent: US 8,096,165 B2
• Time in Patent Office: Days
• US Class Current: 73/24.20
• CPC Class Codes: G01N 2291/0215 Mixtures of three or more gases, e.g. air
• CPC Class Codes: G01N 29/036 by measuring frequency or resonance of acoustic waves
• CPC Class Codes: G01N 29/222 Constructional or flow details for analysing fluids optoacoustic fluid cells G01N29/2425
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00
• CPC Class Codes: G01N 29/42 by frequency filtering or by tuning to resonant frequency

Abstract

A spectrophone assembly comprises a single detector chamber, a plurality of lasers, a gas inlet for supplying a gas sample to the single detector chamber, and at least one microphone. The detector chamber has an internal geometry arranged to be simultaneously acoustically resonant at a plurality of different resonant frequencies. Each laser operates at a different wavelength and is positioned to emit radiation into the single detector chamber, and is operable to emit radiation that is amplitude modulated at a frequency rate corresponding to a particular resonant frequency different from the resonant frequency of each other laser, simultaneously with each other laser. The microphone(s) are positioned in the single detector chamber so that each microphone is located at or near a maximum of a corresponding acoustic resonance defined by the internal geometry of the detector chamber.

Claims

1. A spectrophone assembly, comprising:

a single detector chamber;

the detector chamber having an internal geometry arranged to be simultaneously acoustically resonant at a plurality of different resonant frequencies;

a plurality of lasers each operating at a different wavelength and positioned to emit radiation into the single detector chamber;

each laser operable to emit radiation that is amplitude modulated at a frequency rate corresponding to a particular resonant frequency different from the resonant frequency of each other laser, simultaneously with each other laser;

a gas inlet for supplying a gas sample to the single detector chamber; and

at least one microphone positioned in the single detector chamber, each microphone located at or near a maximum of a corresponding acoustic resonance defined by the internal geometry of the detector chamber.

2. The spectrophone assembly of claim 1, wherein the internal geometry of the detector chamber comprises at least two cylindrical tubes internally connected to one another.

3. The spectrophone assembly of claim 1, further comprising:

at least one power meter sensitive to the frequency rate and the wavelength of each laser and positioned to receive radiation from the lasers after said radiation has passed through the detector chamber;

a filter coupled to the at least one power meter and operable to separate exit power measured by the at least one power meter into power components for each of the frequency rates;

a plurality of phase-lock amplifiers, each phase-lock amplifier being;

coupled to a corresponding microphone to receive a signal therefrom;

referenced to the frequency rate corresponding to the position of its respective microphone; and

operable to evaluate the microphone signals and convert them into direct current values;

a computer coupled to the filter to receive the power components therefrom and to the phase-lock amplifiers to receive the direct current values therefrom, and operable to use the power components and the direct current values to generate specie identifications.

4. The spectrophone assembly of claim 3, wherein the at least one power meter comprises a single power meter sensitive to the frequency rate and the wavelength of each laser.

5. The spectrophone assembly of claim 3, wherein the at least one power meter comprises a plurality of power meters, each power meter sensitive to the frequency rate and the wavelength of a particular laser.