121 results about "Tunable diode laser absorption spectroscopy" patented technology

A method and apparatus for remote laser-based detection of gas at levels exceeding natural background levels preferably utilizing wavelength modulated tunable diode laser absorption spectroscopy. In a preferred embodiment, background gas and noise are estimated using statistical moving average and variance calculations. Gas concentration length measurements resulting from the spectroscopy are preferably compared in real-time or near-real-time to the sum of the background and noise estimates and an alarm limit to detect gas presence of concern. Gas levels exceeding this detection threshold are preferably indicated by a prolonged output tone with a pitch indicative of the magnitude of the gas measurement, and gas levels below the detection threshold are preferably indicated by silence.

The invention discloses a low-concentration, multi-component and high-sensitivity gas detection method based on integration of multiple spectrum technologies. Advantages of an ultraviolet differential optical absorption spectroscopy (DOAS) technology and an infrared tunable diode laser absorption spectroscopy (IR-TDLAS) technology are integrated, so that information integration and characteristic signal extraction of two kinds of spectrum are realized. The method disclosed by the invention is used for measuring the NH3 concentration in smoke by utilizing a TDLAS method and simultaneously measuring the concentrations of SO2 and NO2 in smoke by utilizing an ultraviolet DOAS method; interference of three components in the NO absorbancy is removed according to the obtained concentrations and an interference spectrum of three kinds of gas to the NO absorbancy, so that the NO concentration without cross interference is solved; and thus, the measurement precision and the detection lower limit are greatly increased.

The invention discloses a gas flow rate survey meter based on the tunable diode laser absorption spectroscopy technology, comprising a red-light light source, a laser, a signal generator, a laser launcher, a laser receiving device, an optical-fiber interferometer, a data acquisition card, a detector, a locking amplifier and a data processing and displaying module. The gas flow rate survey meter works in an all optical fiber mode, which facilitates the remotely transmission of a signal. Compared with the prior art, the gas flow rate survey meter based on the optical method disclosed by the invention has the advantages of non-invasive monitoring object, high spatial resolution, high dynamic response, high measurement precision and big measurement range. The gas flow rate survey meter is easy to install, prevents dust, prevents from splashing, corroding and shocking and is suitable for monitoring industrial emission with high temperature, high dust content and high toxicity and corrosivity. The gas flow rate survey meter also can be used for measuring high-speed airflow of which the flow velocity reaches thousands of meters / second, and can be used for detecting airplane engines.

The invention discloses a composite multi-harmonic-based online gas concentration measurement method and belongs to the technical field of tunable diode laser absorption spectroscopy (TDLAS). The method comprises the following steps: determining the line width of an absorption line by virtue of a ratio of second harmonics to quadruple harmonics, and calculating to obtain a linear function; and calculating the gas concentration according to a deduced ratio of second harmonics to first harmonics under strong absorption conditions. According to the method, the gas concentration is measured under the strong absorption conditions by the second and first harmonic signal mark-free method of absorption signals, the influence of laser intensity fluctuation, photoelectric amplification factors and other factors is eliminated, the signal to noise ratio and measurement accuracy are improved, the problem that a concentration measurement error is caused in a wavelength modulation method because the linear function of the absorption line is uncertain is effectively solved, the gas concentration measurement accuracy is improved, and the application range of the TDLAS technology is widened.

The invention discloses a gas density quantitative analyzer based on tunable diode laser absorption spectrum technique and state space theory, wherein the hardware portion is composed of an emitter, a receive system and a central processor or the like, the software portion uses Kalman filtering algorithm based on state space. The invention uses a laser beam with continuous frequency change generated by a tunable laser to scan the absorption peak of special gas, feeds the laser beam after the tested gas into a light-sensitive detector which obtains a refractive index relationship relative the laser beam of each frequency and gives strength spectrum data at relative wavelength to be sent to the central processor, uses the gas density analysis software in the central processor to model the spectrum data into a measurement equation and build a gas density state equation while sets density distribution stable along time, uses Kalman filtering algorithm to process and processes gas density robust inversion.

The present disclosure relates to in-situ, line-of-sight measurements of partial pressure and temperature associated with at least one flow channel of a fuel cell. Tunable diode laser absorption spectroscopy (TDLAS) is employed for measurements for which water transition states sensitive to temperature and partial pressure are utilized. Measurements are achievable for a fuel cell operating under both steady-state and time-varying load conditions. For steady-state operation, the water partial pressure increases with increasing current density on a cathode side of the fuel cell due to production of water by electrochemical reaction. Temperature in a gas phase remains relatively constant since the fuel cell housing temperature is controlled externally. For non-steady-state operation of the fuel cell through a time-varying current profile, the water partial pressure responds to the load changes rapidly and follows a current profile. The gas temperature varies in response to the dynamic loading and departures from steady-state conditions become more apparent at higher fuel cell operating temperatures.

The invention discloses a gas concentration on-line measurement method based on a full-width-at-half-maximum integral method and belongs to the technical field of tunable diode laser absorption spectroscopy (TDLAS). According to the method, a gas absorption rate curve which is fitted by a direct absorption method is integrated in a full-width-at-half-maximum range near the central frequency of a spectral line, and the concentration of gas to be measured is determined according to an iterative algorithm. The method has the advantages that the problem of concentration measurement errors caused by inaccurate fitting of the gas absorption rate curve of the direct absorption method under the condition of weak absorption can be effectively solved, the measurement accuracy of gas concentration is improved, and an application range of a TDLAS technology is expanded.

The invention belongs to the technical field of measurement of concentration, temperature, pressure or flow speed of gas and provides a method and a device for improving the detection precision of a tunable laser absorption spectrum. Under a condition that the expense of system hardware is not increased, all pieces of information of spectral lines can be completely acquired and recorded, so that the measurement precision of a TDLAS (tunable diode laser absorption spectroscopy) system is improved; furthermore, the method and the device are suitable for on-line (in-situ) or off-line detection or monitoring application in the concentration, the pressure, the temperature and the flow speed of the gas. According to the technical scheme disclosed by the invention, a method for improving the laser gas analysis sensitivity based on nonlinear tuning comprises the steps of detecting the absorption spectrum of the gas to laser, and measuring parameters including the concentration, the pressure, the temperature and the flow speed of the gas, wherein certain transformation is applied in a laser excitation stage, and corresponding inverse transformation is applied in the stage of detecting the absorption spectral lines of the gas to the laser. The method and the device are mainly applied to gas detection.

The invention discloses a frequency locking device based on tunable laser absorption spectrum, and a frequency locking method of the frequency locking device. The frequency locking device comprises a laser (1), an optical fiber (13), a collimation optical fiber (2), a scattered light collection lens (3), a photoelectric detector (4), a temperature and current control part (5) and a frequency stabilization part (16); particularly, the frequency stabilization part (16) comprises a lock phase amplification device (9), a data acquisition and analysis device (10), a simulation PID device (8), an operational amplifier (7), a addition device (15) and a signal generator (6) which are sequentially connected in series; according to the method, the laser is modulated by a triangle wave superposition sine wave, and the distance between two absorption peaks generated by the rising edge and the falling edge in the received scattered light signal containing gas absorption information is taken as variable value, so that a stable frequency feedback control signal is obtained, and the frequency is stabilized on the specific absorption peak. The device and the method are widely used for detecting the compositions and the contents of substances in the atmosphere by a laser spectrum technology.

A TDLAS (tunable diode laser absorption spectroscopy) temperature calibration system is used for calibrating in TDLAS temperature measurement and is characterized by comprising a standard sensor temperature measurement system and a calibrated TDLAS temperature measurement system for gas temperature measurement in vacuum environment. An optical system in the TDLAS temperature measurement system is located in a thermostatic bath. Thermostatic liquid is reserved between a shell of the optical system and the peripheral wall of the thermostatic bath. A standard sensor in the standard sensor temperature measurement system is located in the thermostatic liquid.

The invention discloses a self-calibration method of a TDLAS (Tunable Diode Laser Absorption Spectroscopy) gas detection system. The self-calibration method comprises the following steps: according to a calculation formula of a Beer-Lambert principle, inputting first incident laser, corresponding to the frequency of target gas generated by a gas absorption spectrum, into an optical path switching device, and absorbing the first incident laser, entering an appointed standard gas chamber after passing through the optical path switching device, by target gas in the appointed standard gas chamber to obtain first transmission laser; converting the first transmission laser to obtain a digital electric signal about the amplitude of the first transmission laser; according to the digital electric signal, calculating to obtain a light intensity value I01 of the first incident laser and a light intensity value It1 of first transmission laser; and based on the two light intensity values and with introduction of the known gas content C0 in the standard gas chamber, inverting a calculation coefficient alpha*L1 of target gas concentration, namely the product of a gas absorption coefficient alpha and standard gas chamber length L1 of the TDLAS gas detection system. The method can be used for performing self-calibration on the calculation coefficient alpha*L1 of target gas in the system.

A system and method to discriminate between a first preselected gas and at least one other preselected gas use of an absorption spectroscopy analyzer that includes a Herriott cell and a temperature sensitive light source. The light source operates at a temperature that emits a beam at a wavelength that corresponds to high absorption by a first preselected gas. When a predetermined level of this gas is detected in a gas sample, the analyzer changes the operating temperature of the light source to emit a beam at a wavelength that corresponds to high absorption by a second preselected gas. The second preselected gas can be a different isotope of the first preselected gas.

The invention relates to a scanning and transceiving integrated remote sensing measuring device and method for motor vehicle exhaust based on TDLAS-based (tunable diode laser absorption spectroscopy-based). Emergence wavelength of lasers covers target absorbing peaks of gas under test through temperature and current control of the lasers; a free light output multi-wavelength coupling unit provideshigh coaxiality or superposition of multiple beams; the coupled beam gains transceiving integration and beam scanning through an off-axis parabolic mirror and a rotating hexahedral reflector; the rotating hexahedral reflector enables the coupled beam to scan exhaust emission plumes and reach strip reflecting stickers on a ground; the transceiving integrated structure focuses light, reflected by the reflecting stickers, to a detector; a detector signal is received and processed by an acquisition processing unit so as to exhaust emission information; the device also includes a wavelength locking unit that locks wavelength of each laser in real time; frequently calibrating a system is not required. The device has high sensitivity and high spectral definition, and is suitable for real-time efficient measurement of exhaust emission.

The invention discloses a device for measuring gas concentration based on a short cavity enhanced correlation spectroscopy, and a method for measuring the gas concentration by adopting the device, and relates to the field of laser absorption spectra, in particular to a high-sensitivity measuring device and a method for the gas concentration. The device and the method aim at solving the problems that the existing cavity enhanced TDLAS (Tunable Diode Laser Absorption Spectroscopy) is poor in stability, high in cost and large in size. Laser modulated by a signal modulator and sent by a multimode laser device is divided into two beams by a beam splitter; one beam passes through a reference gas cell and then is received by a reference detector; the other beam passes through an optical isolator, a pre-diaphragm, a post-diaphragm and a high reflection cavity sample cell provided with high reflectors at the two ends, and then is received by a sample detector; two detector signals are input into a data acquisition processor for analyzing and processing; and finally the concentration of to-be-measured gas is obtained. The device and the method are suitable for measuring the trace gas concentration.

The invention provides a laser beam combiner for simultaneously detecting various types of gas of a TDLAS (Tunable Diode Laser Absorption Spectroscopy) and belongs to the technical field of laser gas detection. In the prior art, the attenuation is high, the work wavelength range is narrow and the construction cost of a beam combining part is high. The laser beam combiner is characterized by being provided with a plurality of paths of incidence optical fibers; an emergent end of each path of the incidence optical fiber is connected with a collimating mirror and each incidence optical fiber is a single-core and single-mode optical fiber; mutually-parallel optical axes of the plurality of collimating mirrors of the plurality of paths of incidence optical fibers are parallel to the optical axis of a concave spherical surface reflection mirror; the mutually-parallel optical axes of the plurality of collimating mirrors intersect with a reflection surface of the concave spherical surface reflection mirror; an incidence end face of an emergent optical fiber is located on a reflection surface focus point F of the concave spherical surface reflection mirror and is vertical to the optical axis of the concave spherical surface reflection mirror; the emergent optical fiber is a single-core and multi-mode optical fiber; the numerical aperture of the concave spherical surface reflection mirror is less than that of the emergent optical fiber.

The invention discloses a device and a method for measuring flame form and temperature synchronously. According to the method, the transient flame form is detected with high-speed schlieren, and the flame temperature is detected with TDLAS (tunable diode laser absorption spectroscopy); detection zones of the high-speed schlieren and the TDLAS are focused in the same detection zone in a constant-volume combustion bomb respectively, the high-speed schlieren and the TDLAS are controlled synchronously by a digital delay generator, and synchronous detection for the flame form and temperature in thetransient flame propagation process is realized. The device comprises the visual constant-volume combustion bomb, a light source, a pinhole diaphragm, an achromatic Fourier transform lens, an adjustable diaphragm, a high-speed camera, a laser, a laser driver, a function generator, an etalon, a reflector, a photoelectric detector, a data acquisition unit and the like. According to the device and the method, the problem about synchronous measurement for the transient flame form and temperature is solved, the clear flame form is obtained with the high-speed schlieren, the high-temporal-resolution flame temperature is obtained with the TDLAS, and combustion characteristics of transient flame are researched through combination of two results of the flame form and temperature.

The invention discloses a method and a device for detecting trace gas by a scattering-enhanced tunable diode laser and belongs to the field of detection technique of trace gas content. The problem that the existing device for detecting the trace gas by adopting a tunable diode laser absorption spectrum technology is not easy to carry due to large size is solved. The device for detecting the trace gas by the scattering-enhanced tunable diode laser comprises the diode laser, a scattering medium, a photoelectric detector, a sawtooth wave signal generator, a sine wave signal generator, a frequency mixer, a current controller, a temperature controller, a data acquisition card and a computer. The method comprises the following steps: the diode laser modulated by sine wave and sawtooth wave is taken as a light source to irradiate the scattering medium; the photoelectric detector transforms a received optical signal passing through the scattering medium into an electrical signal which serves as a sampled signal to be input to the data acquisition card, and the data acquisition card inputs the received sawtooth wave signal, sine wave signal and sampled signal to the computer. The method and the device are applicable to the detection of the trace gas.

The invention provides a mercury vapor continuous monitoring device and monitoring method based on diode laser, belonging to the technical field of mercury vapor monitoring. The invention enables the problems that a conventional mercury vapor measuring system has a complex structure and real-time monitoring of mercury emission in conventional mercury vapor measuring is poor to be overcome. The monitoring device comprises a signal generator, a first laser diode controller, a second laser diode controller, a first laser diode, a second laser diode, a first reflector, a dichroic beam combiner, afirst convex lens, BBO crystals, a second convex lens, a beam splitter prism, a second reflector, a spectroscope, a sample cell, a reference cell, a first optical filter, a second optical filter, a first detector, a second detector and a data acquisition analyzer. According to the monitoring method, diode laser absorption spectroscopy is used to realize continuous monitoring of the concentration of mercury vapor, and spectral information of reference gas is utilized to realize selective identification and quantitative detection of gaseous elemental mercury, thereby eliminating interference brought by gas like sulfur dioxide and nitrogen dioxide. The monitoring device and the monitoring method provided in the invention are used for on-line monitoring of mercury vapor.

The invention discloses an urban gas pipeline wireless monitoring system and monitoring method based on TDLAS (tunable diode laser absorption spectroscopy) sensors. The monitoring system comprises multiple detection devices, an alarming module, a power supply module and a background monitoring center, wherein the multiple detection devices are installed in a gas pipeline at intervals; each detection device comprises a temperature sensor, a TDLAS sensor, a control module and a wireless communication module; the temperature sensor transmits the collected temperature value of the current detection node in the gas pipeline to the control module, and the TDLAS sensor transmits the collected gas concentration value to the control module; and the control module judges whether the concentration value of gas is in a safe range or not, if not, the control module controls the alarming module to give an alarm, and the collected data and judgment results are uploaded to the background monitoring center through the wireless communication module. Through the invention, urban gas pipeline systems can be monitored and managed in time, so that gas leakage is prevented and life safety is guaranteed.

The invention discloses a method of synchronously measuring pressure, temperature and concentration of a flow field in a wavelength modulation and absorption method. The width of wavelength modulation and absorption signals is adopted to invert the pressure of the flow field; an influence curve of the pressure towards the modulation and absorption signal strength is then used for correcting the influence of the pressure towards the modulation and absorption signal strength; and finally, the conventional TDLAS (Tunable Diode Laser Absorption Spectroscopy) double-line method measurement principle is used for inverting the temperature and the component concentration of the flow field. By using the method of the invention, the temperature and the concentration of the flow field under dynamic pressure changes or a high pressure environment can be accurately measured, and the method can also realize synchronous measurement on the pressure of the flow field, and the limitation of the conventional pressure sensor can only realize wall surface pressure measurement is broken through.

The invention relates to a gas concentration monitoring device by combining integrating sphere and diode laser absorption spectroscopy and a monitoring method based on the monitoring device, and relates to the gas concentration monitoring device and the monitoring method based on the monitoring device, and the invention solves the problem of low sensitivity and poor miniaturization degree of the current gas concentration monitoring devices. According to the invention, a diode laser is employed as light source, the output light is passed through a collimating lens and then enters into an integrating sphere through a light entering hole of the integrating sphere, the integrating sphere is filled with gas to be measured with unknown, the laser is interacted with gas, an uniform light field is obtained by multiple uniform scattering in the integrating sphere, the scattered light enables emergence through a light outputting hole of the integrating sphere, the emergent light signals are focused to a light reception surface of a detector by a focusing lens, and transformed to electric signals and collected by a data collection card, and the data is input to a computer through a PCI interface for processing to obtain the gas concentration to be measured. The invention is suitable for monitoring the gas concentration.

The invention discloses a distributed optical fiber methane monitoring system based on TDLAS (tunable diode laser absorption spectroscopy). The system comprises a detection mainframe, a transmission layer and a plurality of detection terminals, wherein the detection mainframe is positioned above a well, belongs to the core of the whole monitoring system, and is used for producing detection laser, summarizing and displaying detection data and controlling the detection terminals; the detection terminals are positioned below the well, and used for persistently and uninterruptedly detecting the methane gas concentration, supporting mutual sharing with the detection mainframe and adjusting the operating mode according to the requirements of the detection mainframe; the transmission layer is used for the data interaction between the detection mainframe above the well and the detection terminals below the well, and used for detecting the transmission operation of the laser. The system has high precision, small zero shift, good stability, good selectivity and a long service life, and can be automatically corrected. The system has good practical value and a wide application prospect in the technical fields of photoelectricity data management and security inspection equipment.

The invention discloses a multi-beam interference suppression method for detecting tunable diode laser absorption spectroscopy (TDLAS) gas in a glass container. Multi-beam interference is formed by multiple reflections and transmissions, caused by the two walls of the glass container, of incident light, so that signal waveforms and detection accuracy are seriously affected. By slanting the glass container to be detected in the laser light path direction at a certain angle, the distances between all the transmission lights can be increased due to the enlargement of an incident angle, so that the multi-beam interference is effectively inhibited. The energy obtained after laser transmission is mainly focused on the direct transmission light and the reflected first transmission light, an incident angle expression, which enables the superimposed part of two coherent beams to be positioned outside a receiving detection range, is standardized, and the minimum value of the incident angle is worked out. On this basis, the maximum signal to noise ratio of a second harmonic signal characteristic value is taken as an optimizing index, and the optimal incident angle in a real system is obtained. The method provided by the invention can efficiently extract the second harmonic signal characteristic value for analyzing the gas in the glass container under the premise of not adding a complex optical device and not performing additional information anti-interference processing.

The invention discloses a TDLAS (tunable diode laser absorption spectroscopy)-based intelligent laser ignition device which comprises a laser ignition device, a TDLAS detecting device and an electronic control device. The laser ignition device is used for transmitting pulse laser to break down oil and gas mixtures in a combustion chamber of an internal combustion engine so as to realize an ignition effect; the TDLAS detecting device is used for detecting combustion products in real time and inputting detection signals into the electronic control unit, and the combustion products are generated after the laser ignition effect is realized; the electronic control unit is used for analyzing the detection signals and generating ignition control signals for controlling the laser ignition device. The invention further discloses a TDLAS-based intelligent laser ignition method. The TDLAS-based intelligent laser ignition method includes detecting the combustion products in real time by the aid of the TDLAS detecting device; adjusting ignition time, a focusing position and ignition energy of next laser ignition according to the detection signals and feedback signals of other sensors or switches; repeatedly carrying out the procedure until a perfect ignition state is approached. The TDLAS-based intelligent laser ignition device and the TDLAS-based intelligent laser ignition method have the advantages that the laser ignition performance and combustion characteristics of the internal combustion engine can be effectively improved by the aid of the TDLAS-based intelligent laser ignition device and the TDLAS-based intelligent laser ignition method, and accordingly purposes of saving energy and reducing emission can be achieved.

The invention provides a gas absorption rate online measuring method based on sinusoidal modulation time domain fitting, and belongs to the technical field of tunable diode laser absorption spectrum (TDLAS). The method is characterized in that a sinusoidal signal is used for modulating tunable diode laser current; the laser wavelength sinusoidal modulation is realized; meanwhile, the incident light intensity laser intensity (base line) is enabled to has the clear expression formula; the absorption rate is converted between the frequency domain and the time domain, the clear base line expression formula is combined; the transmission laser intensity is subjected to fitting on the time domain; the synchronous online measurement of the base line and the gas absorption rate is realized. The method has the advantages that the operation is simple and convenient; the problems that the conventional direct absorption method (triangular or sawtooth signal scanning) base line fitting is greatly influenced by artificial factors; the absorption rate measurement precision is low; the time resolution ratio is low; the data processing is completed, and the like. The measurement measure can be provided for spectral line parameter high-precision calibration and gas parameter online monitoring in a complicated industrial field.

A vacuum cavity for tunable diode laser absorption spectroscopy (TDLAS) temperature measurement and calibration is characterized by comprising an upper vacuum chamber and a lower vacuum chamber which are separated by a transmission lens. A reflecting mirror is arranged at the bottom of the lower vacuum chamber, a testing gas feeding port and a vacuum obtaining system connector are respectively arranged on a lateral wall of the lower vacuum chamber, the testing gas feeding port is connected with a second inflation valve, and the vacuum obtaining system connector is connected with a second isolating valve. A collimator installing frame and a photoelectric detector installing frame are respectively arranged in the upper vacuum chamber, and an optical fiber leading-in port, a vacuumizing port and an argon feeding port are respectively arranged on a lateral wall of the upper vacuum chamber.

The invention discloses a CARS (coherent anti-stokes Raman scattering) and TDLAS (tunable diode laser absorption spectroscopy) collinear temperature measurement device which comprises a CARS unit, a TDLAS unit, an input dichroic mirror, a spatial filter and an output dichroic mirror. According to the device, the input dichroic mirror and the output dichroic mirror are used for combining and splitting TDLAS-technology-based laser omega(LD) and CARS-technology-based stokes light omega(s), and a beam shaping mirror and the spatial filter are used for combining and splitting CARS-technology-based pump light omega(p) and the CARS-technology-based stokes light omega(s), so that a transmitter and a receiver are shared by two measurement units, the complexity of measurement systems is lowered, and a TDLAS-technology-based filter and a TDLAS-technology-based detector are prevented from being damaged by omega(p) and omega(s) with high power; different time resolution and measurement accuracy parameters are provided for the parameter analysis in a temperature field, and meanwhile, data comparison verification between the two measurement systems is facilitated.

The invention provides a small-size oxygen measuring device based on a porous material gas cell, belongs to the field of oxygen measurement, and aims at solving the problems that miniaturization of a single device and integration of a multi-component and multi-point measuring system are difficult to carry out as a large-volume gas cell is adopted by an existing oxygen measuring instrument based on tunable diode laser absorption spectroscopy. According to the small-size oxygen measuring device, an output end of a signal acquisition controller is connected with an input end of a diode laser, output light of the diode laser enters an optical fiber by an optical fiber coupler, light output by the optical fiber is output by a beam collimator and enters to the porous material gas cell and then enters a detector by laser beams in the porous material gas cell, an electric signal output end of the detector is connected with an input end of amplifier, an output end of the amplifier is connected with an input end of a power divider, and the two output ends of the power divider are both connected with an input end of the signal acquisition controller by a phase lock. The small-size oxygen measuring device is used for measuring the concentration of oxygen.