45 results about "Differential absorption lidar" patented technology

A method of acquiring data uses multiple sensors in an aircraft. The method includes the steps of: (a) turning ON a DIAL sensor to detect a target of interest during a first flight pass over a region of interest (ROI), wherein the target of interest is a gas or oil pipeline leak; (b) detecting the target of interest using the DIAL sensor; and (c) storing location of the detected target in a look up table (LUT). The method also includes the steps of: (d) during a second flight pass over the ROI, triggering another sensor to turn ON at or about the location stored in the LUT; and (e) confirming presence of the target of interest using both ON-sensors. If necessary, a third flight pass over the ROI is conducted and yet another sensor is triggered to turn ON at or about the location stored in the LUT. Presence of the target of interest is confirmed using all three ON-sensors.

A machine for detecting sulfur hexafluoride (SF6) leaks using the mid-infrared differential absorption lidar (DIAL) technique with a commercically available, air-cooled, compact, pulsed transversely-excited-atmospheric (TEA) carbon dioxide (CO.sub.2) laser, a Cassegranian optical telescope for focusing both the laser emission and returning reflected signal, a user-operated focusing mechanism, a two-dimensional, thermoelectrically-cooled focal plane array (FPA) sensitive in the mid-infrared wavelength range (10.2-10.6 micrometers), a charge-coupled device (CCD) for 2-D imaging, a computer-based control system to rapidly switch the laser wavelength between 10.2470 micrometers, 10.7415 micrometers, and 10.5518 micrometers to utilize the Differential Absorption Lidar (DIAL) chemical detection technique, a rechargeable battery pack and power supply, and an image and data storage device using a solid-state memory stick.

A differential absorption lidar includes: a light signal generation unit for generating first, second CW light signals with first, second wavelengths having different absorption coefficients with respect to a target, a light intensity modulation unit for subjecting the first, second CW light signal to intensity modulation with a first, second CW modulation signal having a first, second frequency in a baseband, a radiation unit for multiplexing the first, second CW light signals with the intensity modulated, forming the multiplexed light signals with two wavelengths in a predetermined beam size, and radiating the light signals, a reception unit for directly detecting scattered light from the target and converting the scattered light into an electrical signal, and a signal processing unit for extracting only the first, second frequency components from the electric signal, and detecting the concentration of the target from a difference in an amplitude of time wavelengths between two signals.

A continuous wave Light Detection and Ranging (CW LiDAR) system utilizes two or more laser frequencies and time or range shifted pseudorandom noise (PN) codes to discriminate between the laser frequencies. The performance of these codes can be improved by subtracting out the bias before processing. The CW LiDAR system may be mounted to an artificial satellite orbiting the earth, and the relative strength of the return signal for each frequency can be utilized to determine the concentration of selected gases or other substances in the atmosphere.

A method of acquiring data uses multiple sensors in an aircraft. The method includes the steps of: (a) turning ON a DIAL sensor to detect a target of interest during a first flight pass over a region of interest (ROI), wherein the target of interest is a gas or oil pipeline leak; (b) detecting the target of interest using the DIAL sensor; and (c) storing location of the detected target in a look up table (LUT). The method also includes the steps of: (d) during a second flight pass over the ROI, triggering another sensor to turn ON at or about the location stored in the LUT; and (e) confirming presence of the target of interest using both ON-sensors. If necessary, a third flight pass over the ROI is conducted and yet another sensor is triggered to turn ON at or about the location stored in the LUT. Presence of the target of interest is confirmed using all three ON-sensors.

A system for obtaining emission flux of a gas plume, emanating from a source, includes an airborne differential absorption lidar (DIAL) system for determining multiple concentration path length (CPL) values along a flight path; and an airborne wind measuring system (WMS) for determining a wind vector at the aircraft altitude. Also included is a processor for receiving the multiple CPL values determined by the DIAL system and the wind vector determined by the WMS. The processor uses the CPL values to compute either (a) an area-integrated concentration (AIC) value or (b) an average concentration value over a cross-plume extent, defined along the length dimension of the flight path. The processor also scales the wind vector to the near ground altitude level of the gas plume to obtain a scaled wind vector. The emission flux is obtained by multiplying either the AIC value or the average concentration value with a component of the scaled wind vector. The component of the scaled wind vector is defined by a vector perpendicular to the length dimension of the flight path.

The invention discloses an inversion method of micro-pulse differential absorption lidar water vapor spatial and temporal distribution. The inversion method comprises wavelength selection of water vapor detection, calculation and correction of absorption cross sections of water vapor absorption wavelengths and non-absorption wavelengths, and inversion and calibration of water vapor concentrations. An automatic continuous detection device of the micro-pulse differential absorption lidar water vapor spatial and temporal distribution is employed to obtain characteristic backward scattering signals of water vapor absorption in specific spectral lines, the backward scattering signals are subjected to inversion and calibration by a computer utilizing a differential absorption spectrum analysis method, and high-time-resolution, high-spatial-resolution and high-precision water vapor stereo distribution data is obtained.

An interactive combination of Phoswich detector array (PDA) and differential absorption lidar (DIAL) is proposed to trace the unknown radioactive plumes released into the atmosphere from a reactor stack, containment of the nuclear power plants, radioisotope separation laboratories, reprocessing plants or the uranium conversion facilities. The hybrid system represents a powerful technique for the prompt identification and quantification of the effluents with various radionuclide contents to determine the corresponding external dose rate accordingly.

Methods and systems for obtaining a target fluid map of a survey area using a differential absorption LIDAR (DIAL) system are provided. Pulse bursts are transmitted toward the survey area, where each pulse burst includes an off-line pulse and at least one on-line pulse. Pulse bursts, each being associated with a measurement point, are received from the survey area. A concentration path length (CPL) corresponding to a respective on-line pulse, a spatial location associated with the CPL, and an error associated with the CPL are determined for each measurement point. The CPL for each measurement point is arranged within the survey area to form the target fluid map.

A system for obtaining emission flux of a gas plume, emanating from a source, includes an airborne differential absorption lidar (DIAL) system for determining multiple concentration path length (CPL) values along a flight path; and an airborne wind measuring system (WMS) for determining a wind vector at the aircraft altitude. Also included is a processor for receiving the multiple CPL values determined by the DIAL system and the wind vector determined by the WMS. The processor uses the CPL values to compute either (a) an area-integrated concentration (AIC) value or (b) an average concentration value over a cross-plume extent, defined along the length dimension of the flight path. The processor also scales the wind vector to the near ground altitude level of the gas plume to obtain a scaled wind vector. The emission flux is obtained by multiplying either the AIC value or the average concentration value with a component of the scaled wind vector. The component of the scaled wind vector is defined by a vector perpendicular to the length dimension of the flight path.

A triacetone triperoxide cloud associated with a triacetone triperoxide explosive attached to a hard target is remotely detected by operating differential-absorption lidar lasers to transmit a laser beam toward the hard target at differing wavelengths. A backscattered laser beam reflected from the lidar target (hard target, person, aerosols, clouds, buildings) is detected because a cloud of triacetone triperoxide in front of the lidar target and between the lidar target and the differential-absorption lidar system produces a differential-absorption signal having characteristics that identify the triacetone triperoxide. In a second embodiment, a triacetone triperoxide cloud that is absorbing optical radiation from its ambient environment and which is attached to a hard target is detected from a location remote from the triacetone triperoxide explosive by detecting an optical radiation absorption signature characterized by triacetone triperoxide absorption lines.

An interactive combination of Phoswich detector array (PDA) and differential absorption lidar (DIAL) is proposed to trace the unknown radioactive plumes released into the atmosphere from a reactor stack, containment of the nuclear power plants, radioisotope separation laboratories, reprocessing plants or the uranium conversion facilities. The hybrid system represents a powerful technique for the prompt identification and quantification of the effluents with various radionuclide contents to determine the corresponding external dose rate accordingly.

The invention provides a coherent differential absorption laser radar comprising a first tunable continuous wave laser, a second tunable continuous wave laser, a beam splitter, an acousto-optic modulator, a laser amplifier, a circulator, a transmitting and receiving telescope, a coupler, a balance detector, an acquisition card and a digital signal processing system. Two required laser wavelengthsare determined by selecting appropriate absorption lines of gas molecules to be tested in intermediate infrared, then local oscillation light and signal light are split by the beam splitter, frequencies are finally combined by the coupler, and the balance detector is used for detection to obtain a concentration of the gas molecules. Due to the larger gas absorption cross-section coefficient and lower background radiation of the intermediate infrared, the detection sensitivity is improved. The use of coherent detection instead of direct detection reduces the influence of low quantum efficiencyon the precision of detection, improves the utilization of echo signals, and improves the performance of the differential absorption laser radar.

A triacetone triperoxide cloud associated with a triacetone triperoxide explosive attached to a hard target is remotely detected by operating differential-absorption lidar lasers to transmit a laser beam toward the hard target at differing wavelengths. A backscattered laser beam reflected from the lidar target (hard target, person, aerosols, clouds, buildings) is detected because a cloud of triacetone triperoxide in front of the lidar target and between the lidar target and the differential-absorption lidar system produces a differential-absorption signal having characteristics that identify the triacetone triperoxide. In a second embodiment, a triacetone triperoxide cloud that is absorbing optical radiation from its ambient environment and which is attached to a hard target is detected from a location remote from the triacetone triperoxide explosive by detecting an optical radiation absorption signature characterized by triacetone triperoxide absorption lines.

A method of finding a temporal location of a reflected pulse in a system for remotely measuring characteristics of a target scene. The method includes steps of: (a) transmitting a pulse burst of two or more pulses toward the target scene; (b) capturing a copy of the pulse burst transmitted in step (a); (c) measuring an inter-pulse separation between at least two pulses in the pulse burst captured in step (b); (d) receiving a signal reflected from the target scene; (e) determining a temporal location of a first pulse in the signal received in step (d); and (f) determining a temporal location of a second pulse in the signal received in step (d) based on the inter-pulse separation measured in step (c). Step (a) may include transmitting an OFF-line pulse and at least one ON-line pulse in the pulse burst toward the target scene from a differential absorption LIDAR (DIAL) system, where the OFF-line pulse and the ON-line pulse are combined pulses, each individually generated from a separate pulsed laser transmitter and each having a different wavelength.

An improved method for determining whether a measurement point, measured using a differential absorption LIDAR (DIAL) system, represents a plume point or a non-plume point. Concentration path lengths (CPL's) for a plurality of measurement points are determined. An average non-plume CPL, CPL, is provided. For each measurement point, a standard deviation, CPLsd, is calculated based on first order error propagation and it is determined that the measurement point represents a non-plume point when the Hooshmand decision rule (HDR) is met. The HDR is given by,(cpl-CPL_CPLsd)2>(T)2,where cpl is the corresponding CPL of the measurement point being tested and T is a threshold standard deviation level.

A method for improving the accuracy of estimating concentration path length of a target molecule using a differential absorption LIDAR (DIAL) system. In particular, this method allows improved detection of plumes containing the target molecule against inhomogeneous background, such as uncovered ground or ground with various types of cover. In an embodiment of the present invention, spectral surface reflectivity variations are systematically corrected based on interpolation of surface reflectivity measurements of multiple offline beams of different wavelengths, which are relatively close to the online wavelength. In another embodiment, the signal to noise ratio of the received online pulse energy is improved by using multiple laser beams having the online wavelength and the signal to noise ratio of the received pulse energies at an offline wavelength is improved by using multiple laser beams having that offline wavelength.

The invention discloses an 828nm atmospheric water vapor detection differential absorption lidar transmitter system, which includes an 828nm continuous wave seed laser, a single-longitudinal-mode narrow-linewidth pulse Nd:YAG laser, a KTP ring cavity optical parametric oscillator, a PDH seed laser wavelength stabilization unit of a multi-channel absorption cell based on water vapor absorption, andan optical parametric oscillator resonant cavity length locking unit based on a scanning holding technology. The transmitter system can generate single-frequency laser pulse suitable for atmosphericwater vapor detection, and is the core structure of differential absorption lidar.

The invention discloses a differential absorption laser radar transmitter for detecting atmospheric pressure. The transmitter actively stabilizes the wavelength of a continuous wave semiconductor seedlaser device on R21 and R22 absorption lines of HCN gas or R9 and R8 absorption lines of acetylene C2H2 gas by means of the pound drow Howe Technology, the seed laser is injected into an annular resonant cavity of an optical parametric oscillator by adopting a scanning-maintaining-pumping method, and the cavity length is locked; an optical parametric oscillator outputs dual-wavelength signal light within the wave band of 1529.4+ / -0.6 nm or 1520nm+ / -1.0 nm, the signal light is converted into dual-wavelength laser pulses within the wave band of 764.4-765.0 nm or 759.5-760.5 nm through a frequency multiplier, the energy of the dual-wavelength laser pulses is amplified through a parametric amplifier, and the transmitter finally outputs detection laser and reference laser which are stable in wavelength and large in energy, units are organically integrated to form a differential absorption laser radar transmitter. The transmitter is advantaged in that a transmitter system ensures stabilityof the detection wavelength and the reference wavelength of the transmitter on the premise of ensuring higher transmitted pulse energy.

The invention discloses a device for generating multi-wavelength stimulated raman laser, which comprises an optical maser (1), and a focus lens (4), a raman pipe (5) and a collimation component (6) all arranged on an output laser path (2) of the optical maser, and is characterized in that a frequency multiplier (3) is arranged on the laser path between the optical maser (1) and the focus lens (4); mixed gas with air pressure ranging from 1.2 MPa to 3.4 MPa is filled into the raman pipe (5), and comprises deuterium gas, hydrogen and helium; the ratio of the deuterium gas, the hydrogen and the helium is (0.8-1.2) : (0.23-0.27) : (0.29-0.33); the focal distance of the focus lens (4) is from 30 cm to 60 cm; and the collimation component (6) comprises a concave lens (61) and a convex-concave lens (62) with the same optical axis, and the focal distance of the concave lens (61) is from minus 30 cm to 60 cm and the focal distance of the convex-concave lens (62) is from 20 cm to 30 cm. The device can not only directly provide wavelength pairs required by an ozone differential absorption lidar, but also can be independently used as a light emitting source of the lidar, and can emit multi-wavelength differential laser beams with the same laser beam at the same time.

The invention relates to a constant calibration method for a differential absorption laser radar system and belongs to the technical field of laser radar detection. The method comprises the followingsteps that: (1) a first photoelectric detector, an absorption cell and a hard target are respectively placed at the emergent laser of the system; the position of the absorption cell is adjusted, the first photoelectric detector is arranged at the front end of the absorption cell and is used for signal monitoring and initial ON and OFF energy monitoring; (2) the absorption cell is vacuumized through a vacuum pump, and then is filled with a target gas of which the standard concentration is 20000 ppm, and pressure intensity in the absorption cell is recorded; (3) a laser is switched on, and ON and OFF signals detected by the first photoelectric detector and a second photoelectric detector are recorded through by a signal acquisition card; and (3) the constants of the radar system are determined according to acquired data, the absorption cell and the hard target are removed, normal atmospheric detection is performed, an improved inversion formula is adopted to perform normal gas concentration detection. With the method of the invention adopted, the initial energy of laser is monitored; laser states are recorded in real time; and data reliability is improved.

The invention relates to a frequency comb laser radar detection method for simultaneously measuring various components of atmosphere and a system. The method includes the following steps that: S1, a seed laser emits seed light, after the seed light passes through a corresponding frequency comb laser, a plurality of spectral frequencies are outputted, and then emitted into the atmosphere through areflector; S2, a telescope is adopted to collect echo signals generated by the interaction of the laser and the atmosphere, the echo signals sequentially pass a corresponding beam splitter, so that signals of different frequencies can be divided through the beam splitter; S3, the signals of different frequencies pass through a corresponding filter and thereafter are emitted into a corresponding detector; and S4, the detector converts detected optical signals into electrical signals, and then the electrical signals are acquired through a data acquisition unit, and the acquired data are stored in a data processing unit. According to the method and system of the invention adopted, the frequency comb laser is introduced, and an inversion algorithm for simultaneously measuring various atmospheric components is developed based on a traditional differential absorption laser radar inversion technique, and therefore, the method and system have great theoretical and practical value.

A filter for a micropulse differential absorption LIDAR is provided. The filter comprises an etalon including a free spectral range substantially the same as a difference between a first laser wavelength and a second laser wavelength, the etalon further including a finesse providing substantial background noise suppression and substantially constant transmission of the first laser wavelength and the second laser wavelength over a predetermined range of wavelengths, and a first filter having a first filter bandpass selected to include the first laser wavelength and the second laser wavelength.

The invention discloses a novel estimation method for point source CO2 emission based on CO2-DIAL simulation measurement. The method comprises the following steps: inverting CO2 emission of a specific local point source by utilizing a Gaussian diffusion model and CO2 concentration of range analysis; and the method comprises the following steps: calculating and measuring the position of a differential absorption laser radar observation point; establishing a linearization equation by utilizing a Gaussian linear diffusion model; solving the equation by using a Jacobi iterative algorithm; and comparing the CO2 concentrations of the observation points calculated according to different heights of the chimney with the CO2 concentrations of the actually measured observation points, and when the error is minimum, determining the effective emission height of the strong point source so as to determine the CO2 emission intensity of the strong point source. The inversion method provided by the invention is combined with a ground-based CO2 differential absorption laser radar for use, so that the CO2 emission intensity of a point source can be obtained with high precision, and an important supplementary means is provided for artificial CO2 emission monitoring and verification.

The invention discloses an ozone space-time differential absorption laser radar system based on a CO2 single Raman tube and a detection method. The system comprises a laser emission unit, an optical receiving unit and a signal acquisition and signal analysis unit. The laser emission unit adopts a CO2 single Raman tube light source system and also emits lasers of 276 nm, 287 nm and 299 nm; a Cassegram type telescope is used for receiving ultraviolet multi-wavelength back scattering light; a high-resolution grating spectrometer is used for color separation of multi-wavelength back scattering light; the optical signal from the optical receiving unit is converted into a digital signal by the signal acquisition unit and is stored in an industrial personal computer; real-time analysis is performed through the signal analysis unit, the detection blind area can be effectively reduced, the influence of aerosol interference factors is reduced, simultaneous monitoring of boundary layer ozone andfree troposphere ozone is realized, the system is especially suitable for ozone vertical profile monitoring in a heavy haze process, and realizes high-temporal-spatial-resolution and high-precision day and night measurement of the boundary layer ozone and the free troposphere ozone in different weather scenes such as the heavy haze process and clean weather.

The invention provides a method for improving inversion precision of carbon dioxide differential absorption laser radar. The method comprises the following steps: 1, inverting an optical thickness value of each layer of carbon dioxide according to an actual measurement signal of differential absorption laser radar; 2, optimizing the optical thickness value of each layer of carbon dioxide accordingto Chebyshev fitting; and 3, constructing a conditional adjustment model by taking the total carbon dioxide optical thickness value between the lowest signal receiving position and the boundary layeras a limiting condition and taking the signal-to-noise ratio of each layer of signal as a weight to obtain an optimal carbon dioxide optical thickness value of each layer. The inversion method basedon the carbon dioxide differential laser radar profile concentration provided by the invention not only has good precision, but also has strong stability. Therefore, the limitation of carbon dioxide inversion precision on hardware parameters is greatly reduced, and more accurate data is provided for researching carbon cycle and climate change.

The invention belongs to the technical field of laser, and discloses an all-solid-state Tm:LuScO3 Q-switched mode-locked ceramic laser. The laser comprises the components of a pumping source which isused for generating pumping laser with wavelength of 795.7nm; a focusing lens which is used for realizing high transmission rate to the pumping laser and focuses the pumping laser into crystal; a Tm:LuScO3 ceramic laser gain medium which is used for changing the pumping laser with central wavelength of 795.7nm to the laser in a 2[mu]m wave band; a laser resonator which is used for realizing operation of the laser in the 2[mu]m wave band; and an oxide graphene saturable absorber which is used for converting output continuous light to pulse light. The invention provides a solid laser source which emits the laser in the 2[mu]m wave band and in a water molecule strong absorption wave band, such as laser distance measuring machine, coherent Doppler wind measurement radar, water vapor parabolicsurface differential absorption laser radar system, laser ophthalmologic operation and laser micromachining.

The invention discloses a near-infrared all-fiber water vapor differential absorption laser radar, and belongs to the technical field of laser radars. The near-infrared all-fiber water vapor differential absorption laser radar comprises a laser light source used for outputting on-band continuous laser and off-band continuous laser, an optical switch, a pulse generator, an optical amplifier, an optical transceiver telescope, a filter, a detector, an acquisition card and a data processing module. The laser light source adopts a near-infrared long wave band with the wavelength range of 1100-2526 nm as a measurement wave band of water vapor differential absorption, and compared with common near-infrared short waves, molecular Rayleigh signals can be neglected, so that the water vapor inversion precision is improved, and an inversion algorithm is simplified. According to the invention, wavelength division multiplexing is realized by adopting the optical switch, simultaneous detection of on-band and off-band signals is realized, the system structure is simplified, and the system cost is saved.