262 results about "Photoacoustic spectroscopy" patented technology

A system and method for performing multispectral imaging locates features of interest in a specimen using a technique known as multiphoton photoacoustic spectroscopy. In this technique, a tunable high-power laser is used to initiate multiphoton excitation events which are then detected as an acoustic signal using a sensor such as an ultrasonic piezoelectric transducer. The transducer signal is processed to form a normalized MPPAS signal intensity which may then be used as a basis for forming a spectral image. Unlike other spectroscopies, MPPAS is able to monitor non-fluorescent species based on non-radiative relaxation of the light-absorbing species in the specimen. In addition, since the majority of energy imparted to the light-absorbing molecules is released through non-radiative pathways, sensitive measurements of even fluorescent molecules can be performed. The system and method may be applied to detect malignant cells in tissue samples although other uses are contemplated.

The present invention provides a photoacoustic spectrometer that is field portable and capable of speciating complex organic molecules in the gas phase. The spectrometer has a tunable light source that has the ability to resolve the fine structure of these molecules over a large wavelength range. The inventive light source includes an optical parametric oscillator (OPO) having combined fine and coarse tuning. By pumping the OPO with the output from a doped-fiber optical amplifier pumped by a diode seed laser, the inventive spectrometer is able to speciate mixtures having parts per billion of organic compounds, with a light source that has a high efficiency and small size, allowing for portability. In an alternative embodiment, the spectrometer is scanned by controlling the laser wavelength, thus resulting in an even more compact and efficient design.

Methods and apparatus for detecting photoacoustic signals in fluid media are described. The present invention differs from conventional photoacoustic spectroscopy in that rather than accumulating the absorbed energy in the fluid of a sample cell, the absorbed energy is accumulated in an acoustic detector or sensitive element. In a preferred embodiment, the acoustic detector comprises piezoelectric crystal quartz. The quartz is preferably in the shape of a tuning fork.

A method for analyzing gas concentration using doubly resonant photoacoustic spectroscopy, and a doubly resonant photaoacoustic gas detector comprising: i) a continuous wave light beam whose wavelength coincides with an absorption wavelength of a gaseous analyte; ii) a closed path optical cavity having at least two reflective surfaces; iii) an acoustic resonator chamber contained within said optical cavity, and comprising an acoustic sensor for detecting sound waves generated by a gaseous analyte present within said chamber, the light beam passing sequentially into, through and out of said chamber, and being repeatedly reflected back and forth through said chamber, and being modulated at a frequency which is equal to or equal to one-half of an acoustic resonance frequency of said acoustic resonator chamber.

Methods and apparatus for detecting photoacoustic signals in fluid media are described. The present invention differs from conventional photoacoustic spectroscopy in that rather than accumulating the absorbed energy in the fluid of a sample cell, the absorbed energy is accumulated in an acoustic detector or sensitive element. In a preferred embodiment, the acoustic detector comprises piezoelectric crystal quartz. The quartz is preferably in the shape of a tuning fork.

Methods and apparatus for broad tuning of single wavelength quantum cascade lasers and the use of light output from such lasers for highly sensitive detection of trace gases such as nitrogen dioxide, acetylene, and vapors of explosives such as trinitrotoluene (TNT) and triacetone triperoxide (TATP) and TATP's precursors including acetone and hydrogen peroxide. These methods and apparatus are also suitable for high sensitivity, high selectivity detection of other chemical compounds including chemical warfare agents and toxic industrial chemicals. A quantum cascade laser (QCL) system that better achieves single mode, continuous, mode-hop free tuning for use in L-PAS (laser photoacoustic spectroscopy) by independently coordinating gain chip current, diffraction grating angle and external cavity length is described. An all mechanical method that achieves similar performance is also described. Additionally, methods for improving the sensor performance by critical selection of wavelengths are presented.

A method for analyzing gas concentration using doubly resonant photoacoustic spectroscopy, and a doubly resonant photaoacoustic gas detector comprising:i) a continuous wave light beam whose wavelength coincides with an absorption wavelength of a gaseous analyte;ii) a closed path optical cavity having at least two reflective surfaces;iii) an acoustic resonator chamber contained within said optical cavity, and comprising an acoustic sensor for detecting sound waves generated by a gaseous analyte present within said chamber, the light beam passing sequentially into, through and out of said chamber, and being repeatedly reflected back and forth through said chamber, and being modulated at a frequency which is equal to or equal to one-half of an acoustic resonance frequency of said acoustic resonator chamber.

A method and apparatus are provided that assess reservoir compartmentalization by determining whether there are compositional differences such as whether the isotopic ratios of carbon (13C / 12C) or of oxygen (17O / 18O) are the same or different in various parts of the reservoir. A quartz enhanced photoacoustic spectrometer is provided for analysis of reservoir samples taken in various parts of the reservoir for comparison of geochemical composition to estimate reservoir compartmentalization.

A system of using an interferometer, in combination with a laser, and a detector to determine absorptive characteristics of a material under test. The operation of the interferometer allows for determination of the wavelength of the laser beam and for determining relative changes in the wavelength of the laser beam. A method for using a laser source and an interferometer to determine characteristics of a material under test in accordance with the present invention is also provided.

The invention relates to an infrared photoacoustic spectroscopy detection device and method for decomposed components of sulfur hexafluoride under partial discharge, belonging to the technical field of partial discharge on-line monitoring of SF6 gas insulating electrical equipment. The device of the invention mainly comprises an induction voltage regulator, a corona free experimental transformer, a partial discharge free protective resistor, a standard capacitive voltage divider, a non-inductive resistor, a GIS analog element, a wide-frequency high-speed ultrahigh-capacity digital storage oscillograph and an infrared photoacoustic spectroscopy system. In the method of the invention, infrared photoacoustic spectroscopy detection is carried out on the decomposed gas of SF6 under partial discharge in the GIS analog element by the device of the invention. The invention has high sensitivity, little gas consumption, multiple detection components and strong anti-jamming capability, can effectively detect SF6, CF4, SO2F2, SOF2, SO2, HF and the like as low as 0.01 muL / L, and is suitable for on-line detection. The invention can be widely used for detection of partial discharge decomposed gas of SF6 in the SF6 gas insulating electrical equipment, especially the GIS equipment.

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.

The invention discloses a quartz tuning fork strengthened photoacoustic spectroscopy gas sensor based on an acoustic resonator. The gas sensor comprises a laser (1), a focusing lens (5), a tubular resonator, a quartz tuning fork (11), a function generator (15) electrically connected with the laser (1) and a lock-in amplifier (14) electrically connected with the quartz tuning fork (11), wherein the focusing lens (5) and the tubular resonator are arranged on an optical path (2) of the laser (1); the function generator (15) is electrically connected with the lock-in amplifier (14); the tubular resonator is the acoustic resonator (9) with a slit (91) in the middle; the length of the acoustic resonator is not more than 10mm, the external diameter is not more than 1mm and the internal diameter is not more than 0.6mm; the width of the slit (91) is not more than 0.2mm and the length is not more than the internal diameter of the acoustic resonator (9); prongs (111) of the quartz tuning fork (11) are positioned on the slit (91) and the distances between the prongs (111) and the slit (91) are not less than 0.001mm. The gas sensor has simple structure, small volume and strong anti-jamming property, works stably, is convenient to adjust and use and can be extensively used for detecting the components or contents of the gases.

A miniaturized photoacoustic spectrometer made from a series of stacked substrates. An infrared source is formed in a first substrate. A filter is formed in a second substrate. A micro-trough is machined in a third substrate and a microphone is formed in a fourth substrate. A fifth substrate has a metallic deposit for reflecting light emitted by the infrared source. Resin sealing is provided between the substrates.

An off-resonance photoacoustic spectrometric detection and analysis device consists of a photoacoustic spectrometric module (8). The photoacoustic spectrometric module (8) comprises a light source module (2-1), a photoacoustic signal generation module (2-2), an optical power measurement module (2-3) and a fault diagnostic analysis module (2-4). Optical signals generated by an infrared incoherence light source in the light source module (2-1) are focused by an ellipsoidal reflector to form a focused light beam, the focused light beam is modulated into light of specific frequency and wavelength by chopping blades of an optical chopper and optical filters and then transmitted to the photoacoustic signal generation module (2-2), and the fault diagnostic analysis module (2-4) calculates each gas concentration according to to-be-tested gas photoacoustic signals generated by irradiation, diagnoses faults and alarms. The off-resonance photoacoustic spectrometric detection and analysis device can be used for quantitative detection of gases such as SF6, CF4, SO2F2, SOF2, SO2, SF4 and H2O and is applicable to onsite online monitoring.

The invention provides a system and a method for detecting CO gas based on a quartz tuning fork enhanced photoacoustic spectrometry technology, relates to a system and a method for detecting the CO gas and aims at solving the problem of low detection accuracy of the existing CO gas photoacoustic spectrometry detection technology. A data processing module transmits a current control signal to a laser device controller via a function generator, and meanwhile, transmits a temperature control parameter to the laser device controller; the laser device controller drives a laser device to emit near infrared laser which is incident into a gas chamber after being collimated and focused; the gas absorbs optical energy so that the optical energy is converted into heat energy and further converted into an acoustic pressure signal; a quartz tuning fork mounted in the gas chamber converts an acoustic signal into an electric signal; the electric signal of the quartz tuning fork is converted and amplified and then input into the measurement channel input end of a phase-locked amplifier; the phase-locked amplifier inverts the concentration of the CO gas to be detected by performing secondary harmonic detection in combination with the reference signal of the function generator. The system and the method for detecting the CO gas based on the quartz tuning fork enhanced photoacoustic spectrometry technology are applicable to CO gas detection.

A method and apparatus are provided that assess reservoir compartmentalization by determining whether there are compositional differences such as whether the isotopic ratios of carbon (13C / 12C) or of oxygen (17O / 18O) are the same or different in various parts of the reservoir. A quartz enhanced photoacoustic spectrometer is provided for analysis of reservoir samples taken in various parts of the reservoir for comparison of geochemical composition to estimate reservoir compartmentalization.

A combined analyzing apparatus includes (i) a front end unit 30 including a photoacoustic spectroscope that takes a gas sample inside and analyzes the gas sample by a photoacoustic spectroscopy, (ii) an FTIR 10 that is a light analyzing apparatus that takes the analyzed gas sample inside and analyzes the gas sample based on a change of light which is transmitted through the gas sample, (iii) an MS 20 that is a mass analyzing apparatus that further takes the analyzed gas sample inside and analyzes a mass of an ingredient of the gas sample, (iv) a battery 40 that supplies the front end unit 30, and the FTIR 10 and the MS 20 with electric power source, and (v) a portable case 50 that houses the front end unit 30, the FTIR 10, the MS 20 and the battery 40.

Methods and apparatus for broad tuning of single wavelength quantum cascade lasers and the use of light output from such lasers for highly sensitive detection of trace gases such as nitrogen dioxide, acetylene, and vapors of explosives such as trinitrotoluene (TNT) and triacetone triperoxide (TATP) and TATP's precursors including acetone and hydrogen peroxide. These methods and apparatus are also suitable for high sensitivity, high selectivity detection of other chemical compounds including chemical warfare agents and toxic industrial chemicals. A quantum cascade laser (QCL) system that better achieves single mode, continuous, mode-hop free tuning for use in L-PAS (laser photoacoustic spectroscopy) by independently coordinating gain chip current, diffraction grating angle and external cavity length is described. An all mechanical method that achieves similar performance is also described. Additionally, methods for improving the sensor performance by critical selection of wavelengths are presented.

A system and method for analyzing a target analyte gas concentration using a photoacoustic spectroscopy cell comprising:i) a modulatable light source which provides optical radiation at an absorption wavelength of a target analyte;ii) a resonant acoustic chamber for containing said analyte;iii) a microphone positioned within said chamber whereby the acoustic reactance of the microphone is a substantial factor in determining the acoustic resonant frequency of the acoustic chamber and where the magnitude of the acoustic reactance of the microphone is at least two times the acoustic resistance of the microphone.

The invention relates to an online fault photoacoustic and spectroscopic monitoring system for a power transformer in the technical field of power engineering, comprising 7 tunable cascaded diode lasers, a gas and oil separating room, an optical-acoustic chamber, a lock-in amplifier, a power supply controller of the tunable cascaded diode lasers, a difference amplifier, a convex lens, a laser power meter, a digital recorder, an oil feed-back pump, an electric vacuum pump, a PLC and a computer. Ultrasonic degasification separation is performed for an oil sample in the gas and oil separating room, and fault gas is infused in the optical-acoustic chamber, after being directly modulated, a power supply can generate periodic vibration under the action of an infrared beam, thereby exciting to form a sound wave signal. After being detected by a rheomicrophone, the sound wave signal can be magnified by the lock-in amplifier and then is input in the digital recorder, thus the power transformer can be judged whether the current running state is fine according to the numerical value displayed on the digital recorder. Meanwhile, the data can be transmitted to a remote computer in a wire and wireless communication way.

A method for analyzing a target analyte gas concentration using a photoacoustic spectroscopy cell comprising:i) a modulatable light source which provides optical radiation at an absorption wavelength of a target analyte;ii) a resonant acoustic chamber for containing said analyte;iii) a microphone positioned within said chamber whereby the acoustic reactance of the microphone is substantially equal but opposite in value to the acoustic reactance of the chamber at a selected cell resonance frequency.

A method and apparatus are provided that assess reservoir compartmentalization by determining whether there are compositional differences such as whether the isotopic ratios of carbon (13C / 12C) or of oxygen (17O / 18O) are the same or different in various parts of the reservoir. A quartz enhanced photoacoustic spectrometer is provided for analysis of reservoir samples taken in various parts of the reservoir for comparison of geochemical composition to estimate reservoir compartmentalization.

The invention relates to an enhanced multi-group photoacoustic spectrum gas sensing device based on a quartz tuning fork and belongs to the field of a photoacoustic spectrum detection technology. According to the invention, the quartz tuning fork with high quality factor is used to replace a traditional broadband microphone so as to broaden the dynamic range and realize miniaturization of the whole gas sensing device. By arranging a fiber-optic amplifier between a light source and an optical fiber coupler, laser output power of the light source is increased. Thus, it is easy to capture a weak photoacoustic signal generated by the quartz tuning fork, and detection sensitivity of the gas sensing device can be enhanced.

The invention discloses a photoacoustic spectrometry principle-based longitudinal resonant photoacoustic pool applied to monitoring gases dissolved in transformer oil. The longitudinal resonant photoacoustic pool mainly comprises a resonant cavity, buffer chambers, a Brewster window, a gas inlet, a gas outlet and a microphone, wherein the first buffer chamber and the second buffer chamber are arranged at the two ends of the photoacoustic pool and connected with the gas inlet and the gas outlet respectively; a light inlet is connected to a light outlet through the first buffer chamber, the resonant cavity and the second buffer chamber sequentially; the photoacoustic pool is a cylindrical cavity; the microphone is fixed in the middle of the resonant cavity; the opening of the microphone is aligned with the tube wall of the resonant cavity; a temperature sensor is arranged in the first buffer chamber; and a pressure sensor is arranged in the second buffer chamber. The longitudinal resonant photoacoustic pool for the photoacoustic spectrometry monitoring of the gases is characterized by simple structure, small volume, high sensitivity, quick time response, low background noise, capability of detecting multi-component gases, and good application to the photoacoustic spectrometry monitoring of the gases dissolved in the transformer oil.

The invention relates to an optoacoustic spectroscopy multi-ingredient trace gas detection instrument and method, and belongs to the technical field of trace gas detection. The instrument comprises amedium infrared heat radiation light source, a light gathering mirror, a chopper, an optical filter plate group, an optoacoustic pool, a laser light source, an optical collimator, an air inlet valve,an air outlet valve, a microphone, a control and signal processing circuit and a touch screen, wherein the medium infrared heat radiation light source is longitudinally coupled to the optoacoustic pool after the light gathering; the optoacoustic signals are measured by using the intensity modulation-base wave detection technology; the laser is coupled into the optoacoustic pool from the side surface and is reflected for many times on the surface of the pool wall; the optoacoustic signals are measured by using a wave-length modulation-second harmonic detection technology; the background noise interference is greatly reduced. The advantages, suitable for multi-ingredient gas measurement and realizing high detection sensitivity, of the optoacoustic spectroscopy method of the medium infrared heat radiation light source and the laser optoacoustic spectroscopy method are sufficiently used; the technical complementation is realized; the technical scheme with good competitiveness is provided for the high-sensitivity detection of the multi-ingredient trace gas.

A photoacoustic spectrometer that is intensity-modulated, laser-driven and with a calculable cell constant. The axially symmetrical photoacoustic spectrometer combines first-principles models of acoustic wave propagation with high-resolution spectroscopic measurements, and takes into account molecular relaxation. The spectrometer includes a duct and two chambers disposed at the end of the duct. Inlet and exit tubes, which are disposed in substantially the location of acoustic pressure nodes, permit the gas, gaseous mixture or aerosol to enter and exit the spectrometer. The absolute response of the spectrometer may be modeled and measured. A detailed theoretical analysis of the system and its predicted response may be predicted as a function of gas properties, resonance frequency and sample energy transfer relaxation rates.

The invention discloses a photoacoustic spectroscopy-based transformer fault diagnosis method employing a parameter optimization SVM (support vector machine). According to the photoacoustic spectroscopy, contents of five characteristic gases of transformer oil are detected and calculated; 5 SVMs and 4 kernel functions are subjected to cross combination, and 20 SVM models are formed; the heuristic algorithm is adopted to perform parameter optimization on values of penalty factors c and g, and accordingly the SVM model highest in transformer fault diagnosis accuracy and operation speed is established. The experimental result shows that the SVM model composed of a C-SVC (C-support vector classification) model, an RBF (radial basis function) and the genetic algorithm optimization is highest in transformer fault diagnosis accuracy, with test set of 97.5% and training set of 98.3333%, and the optimizing speed of the genetic algorithm is faster than the particle swarm optimization by double. The photoacoustic spectroscopy-based transformer fault diagnosis method has the advantages such as simple operation, non-contact measurement, no consumption of carrier gas, short detection period, stability and high sensitivity.

The invention which relates to an automatic constant temperature type photoacoustic detection device for SF6 decomposed components and an experiment method thereof belongs to the technical field of SF6 gas insulation device partial discharge online monitoring. The device is characterized in that an automatic constant temperature system is arranged in present infrared photoacoustic spectrum monitoring systems; and according to the method, the device is utilized to detect the SF6 gas partial discharge decomposed components in a GIS (gas insulated substation) simulation element under automatic preset temperature constancy conditions. According to the invention, the influence of external environment can be eliminated, the gas components of SO2, CO2, CF4, SO2F2, SOF2 and the like with the concentrations of low to 0.01muL / L can be effectively detected, the accuracy, the detection precision and the stability are high, and performances of a solid state relay are stable, so the long-term effective working of the automatic constant temperature system can be guaranteed. The device which can be widely applied to the field of the SF6 gas insulation equipment partial discharge online monitoring is especially suitable for detecting the SF6 gas partial discharge decomposed components in the GIS.