CN117091760B - Single photon time-dependent ranging and gas concentration detection method, device and medium - Google Patents
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Abstract
The invention relates to the technical field of laser remote sensing gas monitoring, and particularly discloses a single photon time-dependent ranging and gas concentration detection method, a device and a medium, wherein the method comprises the following steps: performing high-speed modulation and pseudo-random coding on a laser emission signal; receiving a scattered signal of the target; performing cross-correlation operation on the accumulated echo signals and the reference coded signals, obtaining an abscissa corresponding to the correlation maximum value, and calculating a detection target distance according to the coding interval and the shift coordinate value; shifting the accumulated signals according to the abscissa values calculated by correlation, extracting signals at corresponding wavelengths, and dividing signals at the ascending section and the descending section of the laser sweep to obtain an original gas absorption spectrum curve; and performing signal fitting on the originally acquired gas absorption spectrum curve, and performing error calculation with a theoretical gas absorption spectrum curve lookup table to obtain an optimal concentration value. The invention reduces the limit of short-distance ranging and low signal-to-noise ratio of the laser radar in the inversion of the short-distance ranging and gas concentration.
Description
Technical Field
The invention relates to the technical field of laser remote sensing gas monitoring, in particular to a single photon time-dependent distance measurement and gas concentration detection method, a device and a medium, which realize remote positioning of gas and rapid gas concentration remote sensing.
Background
There is an increasing demand for quantitative monitoring of gas leakage in industrial and energy production processes. At present, the gas monitoring of a factory is mainly divided into fixed-type and remote-measuring equipment, the in-situ point type short-distance detection limits the large-range gas leakage monitoring of the factory, the in-situ point type chemical monitoring means is easy to be polluted, the false alarm rate is high, the maintenance is complex, and the pollution and damage of the monitoring equipment can be caused after long-term use. For gas leakage, a telemetry device is an important means for developing industrial gas leakage monitoring in a park at present, and two modes of passive and active monitoring mainly exist at present, wherein the passive signal-to-noise ratio is low, the passive spectrum gas imaging spectrum technology utilizes background radiation and heat radiation of a target to detect gas, the sensitivity of detection is ensured by a low-temperature refrigeration type detector, and the device is complex and expensive in cost. The passive spectrum measurement technology is limited by the interference of background radiation, has low accurate quantitative detection precision on gas, and cannot realize gas detection with low leakage rate in a factory. The quantitative evaluation of the gas emission is difficult, accurate information cannot be provided for energy control and environmental effects, and the gas quantification and distance positioning monitoring capability is weak, so that the current quantitative monitoring requirement is met. Active laser monitoring is an effective way. However, in the current active observation equipment, the high-distance resolution monitoring capability of factory monitoring of the differential absorption radar with the ranging positioning and the gas concentration is weak, and the positioning accuracy is on the order of tens of meters, so that the effective positioning capability is weak, the high-real-time monitoring of the gas is weak, and the monitoring time interval is long. The ability to monitor the leak rate for rapid gas quantification is weak. The method is limited by equipment volume and use defects, and the carried platform and observation scene are limited, so that the novel laser remote sensing detection method with the functions of ranging and rapid quantitative monitoring of gas concentration for factory application monitoring has urgent requirements.
Disclosure of Invention
In order to solve the technical problems, the invention provides a single photon time-dependent ranging and gas concentration detection method, a device and a medium, which solve the technical problems existing in the existing laser radar factory gas leakage remote sensing detection.
In order to achieve the above object, the present invention provides the following solutions:
a single photon time-dependent ranging and gas concentration detection method comprising the steps of:
step S1, performing high-speed modulation and pseudo-random coding on a laser emission signal, determining a pseudo-random coding time interval and a sequence length, generating a reference polarization pseudo-random coding signal, emitting the laser signal into a target environment, and ensuring the effect of irradiating laser to a long-distance hard target and covering a gas leakage path;
s2, receiving scattered signals of the laser irradiation surface through a time correlation counting module, and improving the signal to noise ratio through signal accumulation of a laser sweep period;
step S3, performing cross-correlation operation on the accumulated signals and the reference polarization pseudo-random code signals to obtain abscissa positions corresponding to the correlation maximum values, wherein the abscissa positions correspond to shift coordinate values, and calculating the distance information of the detected hard target by combining the pseudo-random code time interval in the step S1;
step S4, shifting the accumulated signals according to the abscissa shift coordinate value corresponding to the maximum value calculated by the cross-correlation operation, extracting the corresponding signal amplitude values at different wavelengths, and dividing the signals of the ascending section and the descending section of the laser sweep to obtain an original gas absorption spectrum curve;
and S5, constructing a theoretical gas absorption spectrum curve lookup table, performing signal fitting according to the acquired gas absorption spectrum curve to obtain a gas absorption spectrum curve signal, performing error calculation on the theoretical gas absorption spectrum curve lookup table and the gas absorption spectrum curve signal to obtain a minimum error value, and substituting the minimum error value into the theoretical gas absorption spectrum curve lookup table to calculate to obtain an optimal concentration value.
Further, a high-speed modulation signal used for modulating the laser emission signal in the step 1 is a triangular wave sweep frequency signal, and the pseudo-random encoding is an M-sequence pseudo-random encoding signal.
Further, the period length of the triangular wave sweep frequency signal is consistent with that of the M-sequence pseudorandom encoding signal.
Further, the time dimension of the signal in the time correlation counting module in step S2 has a conversion relationship with the interval between the laser modulation wavelength dimension, and the time dimension is converted into the wavelength dimension when the gas absorption spectrum curve is calculated, and the conversion relationship is expressed as follows:
，
in the method, in the process of the invention,representing wavelength dimensional data, < >>Representing time dimension data,/->Representation->And->Is a function of the transformation relationship.
Further, the process of calculating the distance information of the detected hard target object in step S3 is as follows:
，
，
wherein,echo signals acquired for a time-dependent counting module, < >>Pseudo-randomly encoded signal for transmitted reference polarization, < >>For the correlation strength signal of the echo signal and the polarization pseudo-random encoded signal,/for the echo signal>For the shift value with the largest correlation, R is the calculated detection distance, c is the light speed, N is the length of the pseudo-random code sequence, and k is the position of the correlation maximum value obtained by carrying out cross correlation between the echo signal and the reference polarization pseudo-random code signal.
Further, in the step 5, in the process of performing signal fitting on the gas absorption spectrum curve, a lorentz equation is selected for fitting, and different wavelength intervals are selected for interpolation fitting.
Further, the step S5 specifically includes:
s5.1, calculating theoretical gas absorption spectrum curves under different temperatures, pressures and concentrations from a spectrum database, and constructing a theoretical gas absorption spectrum curve lookup table;
s5.2, shifting, interpolating and fitting the acquired signals to acquire a final gas absorption spectrum curve;
step S5.3, calculating a gas absorption spectrum curve signal under the corresponding wavelength, performing error calculation with a theoretical gas absorption spectrum curve lookup table to obtain a minimum error value, substituting the minimum error value into the theoretical gas absorption spectrum curve lookup table to calculate an optimal concentration value, wherein the error calculation process is as follows:
，
where SSE is the sum of squares of the errors,gas absorption spectrum curve calculated for the acquisition signal, +.>For the gas absorption spectrum curve in the theoretical gas absorption spectrum curve lookup table, m is the collected gas absorption spectrum curve +.>I.e. the data matrix, j represents the wavelength number of the gas absorption spectrum curve signal.
Further, the spectrum database in step S5.1 is Hitran.
The invention also provides a single photon time-dependent distance measurement and gas concentration detection device, which comprises one or more processors and is used for realizing the single photon time-dependent distance measurement and gas concentration detection method.
The present invention also provides a readable storage medium having stored thereon a program which, when executed by a processor, implements a single photon time dependent ranging and gas concentration detection method as described above.
Compared with the prior art, the invention has the beneficial effects that:
1) The invention realizes the acquisition of the high-precision distance information of the gas absorption spectrum curve and the gas leakage in a certain spectrum range;
2) According to the invention, a laser rapid modulation scheme is constructed by combining a time-dependent counting mode and a laser rapid modulation method, so that the distance resolution and the time resolution of a laser radar gas telemetry system are effectively improved;
3) According to the invention, by combining with a gas absorption spectrum curve database scheme, a theoretical gas absorption spectrum curve and a gas absorption spectrum curve calculated by collecting signals can be quickly searched, so that the gas concentration is calculated, the speed is high, the precision is high, and the reliability of inversion is effectively improved;
4) Compared with the conventional differential absorption laser radar, the method can acquire the signal intensity at two wavelengths, can acquire the absorption line in the whole methane absorption spectrum, has more information and more abundant spectrum information, and can realize multi-spectrum gas absorption spectrum curve detection;
5) Compared with the conventional TDLAS continuous laser remote measuring gas equipment, the device can acquire distance and gas concentration information at the same time, and realize accurate gas leakage monitoring.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments and together with the description serve to explain the invention and do not constitute a undue limitation on the invention, in which:
FIG. 1 is a flow chart of a single photon time dependent ranging and gas concentration detection method of the present invention;
FIG. 2 is a schematic diagram of the wavelength and time dimension modulation of the gas absorption spectrum curve used in a single photon time-dependent ranging and gas concentration detection method of the present invention;
FIG. 3 is a schematic diagram of a laser emitting modulated signal and a receiving modulated signal in a single photon time-dependent ranging and gas concentration detection method according to the present invention, wherein the emitting signal is emitting energy and the receiving signal is receiving photon number;
fig. 4 is a schematic diagram of a received signal extracted from a received signal in a single photon time-dependent ranging and gas concentration detection method according to the present invention, including an original signal diagram a extracted before signal shift, an extracted signal diagram b after shift, and a graph c of a split gas absorption spectrum of an ascending segment and a descending segment of a laser sweep, wherein the ordinate of the graph is the number of received signal photons;
FIG. 5 is a schematic diagram showing the correspondence between the theoretical Hitran gas absorption spectrum curve and the wavelength selected in the single photon time-dependent ranging and gas concentration detection method of the present invention;
FIG. 6 is a schematic diagram of a gas absorption spectrum obtained by curve fitting in a single photon time-dependent ranging and gas concentration detection method of the present invention;
fig. 7 is a schematic structural diagram of a single photon time-dependent ranging and gas concentration detection device according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In order that the above-recited objects, features and advantages of the invention will become more apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
Referring to fig. 1, a single photon time-dependent ranging and gas concentration detection method includes the following steps:
and S1, performing signal modulation on laser, wherein the modulated signals are triangular wave high-speed sweep frequency signals and M-sequence pseudo-random codes, and the adopted laser is a continuous laser.
The laser selected in the example is a near infrared laser, the corresponding wavelength coverage range is the center line of a near infrared methane gas absorption spectrum curve, and the wavelength range of sweep frequency is lambda 0 -λ n ：1653.5-1653.9nm。
In step S1, the modulation signal may be generated by a signal generator unit or an FPGA control unit, where the frequency and resolution of the signal generator meet the requirements, in this example, the triangular wavelength sweep range is 1653.5-1653.9nm, the temperature modulation wavelength change rate is 0.11nm/°c, and the current modulation wavelength change rate is 0.02 nm/mA, and signal regulation is performed by changing the temperature and current values input to the laser.
The order of the M sequence pseudo-random code signal is selected as follows7 th order, corresponding to M sequence length of 2 7 -1=127, the modulation time interval for the M sequence is 10ns, the corresponding theoretical ranging resolution is c×10ns/2=1.5M, and c is the speed of light. The corresponding one M-sequence time period is 10×127=1.27 μs. The same triangular wave high-speed sweep frequency signal period is consistent with the M sequence, the corresponding period frequency is 1/1.27 mu s=787.4 KHz, the wavelength range covered by the laser twice sweep frequency is 1.27 mu s, two gas absorption spectrum curves are realized in one period, and the number of sample points is increased. In the embodiment of the present invention, the signal parameters are described above, and it should be noted that the signal parameters may be other values, which are not limited herein.
As shown in fig. 2, the change of the gas absorption spectrum curve in the corresponding wavelength scanning range and the signal change of the corresponding M-sequence time dimension correspond to the wavelength dimension of the laser sweep, and τ is the corresponding M-sequence time dimension, and the wavelength and the time have a one-to-one correspondence.
In step S1, the emission signal is modulated by a signal, as shown in the emission encoding signal in fig. 3, the laser triangle wave high-speed sweep signal and the M-sequence signal are output by signal superposition, the abscissa is the wavelength dimension converted by the time dimension, the wavelength is continuously changed during the laser sweep, the corresponding signal energy is related to the current sub-motion in the laser, the energy is increased along with the increase of the modulation current, the energy output at the corresponding different wavelengths is approximately linearly changed, and the corresponding signal equation is:
，
for the power variation value of the laser during the modulation with wavelength,/for the laser>Output matrix values corresponding to the pseudo-randomly encoded signal, < >>Superimposed for both signalsTotal output energy with [0 1 ]]N represents the pseudo-random code signal sequence length.
And S2, receiving scattered signals of the laser irradiation surface through a time correlation counting module, and improving the signal to noise ratio through signal accumulation of a plurality of laser sweep periods.
In step S2, signal acquisition and accumulation processing are required for the received target reflected signal, and in this embodiment, the period length of the acquired total echo signal is 1.27 μs, the corresponding period is 787.4KHz, and the corresponding radar echo signal expression is:
，
in the method, in the process of the invention,corresponding to echo signal values received at different wavelengths, a->Corresponding to the original signal energy emitted at the different wavelengths, and (2)>For the laser emission efficiency, +.>For receiving efficiency, +.>For quantum efficiency, +.>For the time interval of the M sequence, +.>For the reflectivity of the detected object, +.>For the wavelength value of the sweep, +.>Is Planck constant, +.>For the speed of light->Receiving optical area, +.>Distance of detection (I)>，/>For laser time of flight>Representing the atmospheric optical thickness.
As shown in fig. 3, after the original echo signal is received and subjected to signal superposition, two absorption valleys On1 and On2 exist in the whole corresponding period, and correspond to the positions of the transmitted signal absorption valleys, the horizontal coordinates of the positions of the received absorption valleys are translated, the horizontal coordinates of the horizontal coordinates correspond to the target detection distance, the whole period range of the signal is 1.27 mu s, and the corresponding maximum detection distance is 190.5m, so that the object in the distance can be identified theoretically.
In step S2, the signals are accumulated, a signal period range is 1.27 μs, in this example, it is assumed that 1000 periods are accumulated, and then the signal quantity is accumulated corresponding to 2000 concentration sweep periods, which is equivalent to a methane concentration time acquisition interval of 1.27ms, the frequency of acquiring the concentration is about 100Hz, in this example, the accumulation frequency is selected to be 1000, and the preset average frequency is in the embodiment of the present invention, and the average frequency can be adjusted according to the signal-to-noise ratio of the actual signal, which is not particularly limited herein.
And S3, performing cross-correlation operation on the accumulated signals and the reference polarization pseudo-random coded signals to obtain an abscissa corresponding to the correlation maximum value position, wherein the abscissa position corresponds to a shift coordinate value, and calculating the distance information of the detected hard target by combining the pseudo-random coded signal time interval in the step S1.
In step S3, including cross-correlation of the signals and solving for the detection distance, in this example, as shown in FIG. 2, there is a signal offset, time of flight, of the echo signalK is the correlation maximum value position of the echo signal and the reference polarization pseudo-random code signal for cross correlation solution, and the corresponding solution formula is:
，
for the correlation operation result matrix,/for the correlation operation result matrix>For the accumulated original signal +.>For reference polarization pseudo-random encoded signal, +.>For the shift value with the largest cross correlation, R is the calculated detection distance and c is the speed of light.
For example, if the position of the shift value where the cross correlation between the received signal and the reference polarization pseudorandom encoded signal is maximum is 10, the corresponding time of flight is 10×10ns=100deg.ns.
In step S3, when the shift value position information corresponding to the maximum cross correlation is calculated, the calculation formula corresponding to the target distance is as follows:
，
for example, the flight time is 100ns, the corresponding detection distance is 100ns×3×10 8 m/s=15 m。
And S4, shifting the accumulated signals according to the shift coordinate values obtained by correlation calculation in the flow, extracting corresponding signal amplitudes at different wavelengths, and dividing the ascending section UP and the descending section DOWN signals of the laser sweep to obtain an original gas absorption spectrum curve.
In step S4, the signal restoration and shift process is required according to the correlation maximum value position coordinate k acquired in step S3, and the corresponding calculation formula is as follows:
，
for shifting the acquired signal by a data matrix, < >>For the collected accumulated data signal, end corresponds to +.>Index position of last value of matrix.
In step S4, the restored signal is shiftedThe signal matrix has one-to-one correspondence with the transmitted signal in the abscissa time and wavelength dimensions, and the restored signal matrix is consistent with the wavelength of the original modulated transmitted signal.
In step S4, signal amplitude extraction is required for the shifted restoration signal, and data extraction operation is performed according to the selected corresponding wavelength or time dimension.
As shown in fig. 4, the signal before the shift and the signal after the shift differ by k bin values on the abscissa and k on the corresponding wavelength dimension, so that the shift operation is performed on the signal according to k.
In step S4, the signal to be extracted is subjected to a segmentation process, and the laser UP-band UP and DOWN-band DOWN signals are segmented and extracted according to the corresponding original wavelength dimension.
In FIG. 4, the right graph corresponds to the swept signals of the segmented UP and DOWN laser segments UP and DOWN, the segmented signals being segmented according to the initial transmit wavelength dimension, the corresponding segmentation range being [ UP: λ ] 1 -λ n/2-1 ], [down:λ n/2 -λ n ]。
In this example, the corresponding M-sequence modulation bin number is 127, so, according to the division principle, signals 1-63 are rising-segment swept signals and falling-segment swept signals are 64-127. In the embodiment of the present invention, the signal length is 127, and it should be noted that the signal length may also be other values, which are not limited herein.
And S5, constructing a theoretical gas absorption spectrum curve lookup table, performing signal fitting according to the originally acquired gas absorption spectrum curve to obtain a gas absorption spectrum curve signal, performing error calculation on the theoretical gas absorption spectrum curve lookup table and the gas absorption spectrum curve signal to obtain a minimum error value, and substituting the minimum error value into the lookup table to calculate to obtain an optimal concentration value.
In step S5, a theoretical gas absorption spectrum curve lookup table is established according to a spectrum database, where the spectrum database is a Hitran theoretical database, and in this example, the selecting gas absorption spectrum curve parameters mainly includes: parameters such as air pressure, temperature, gas type, gas concentration and the like, wherein the corresponding value of the atmospheric pressure is 1atm, the temperature is 300K, the gas type is methane, the concentration range is 100-150000 ppm.m, and a theoretical gas absorption spectrum curve lookup table is constructed. Wherein, each theoretical gas absorption spectrum curve in the lookup table has a one-to-one correspondence with a theoretical concentration value.
In this example, the selected gas pressure and temperature correspond to normal pressure and normal temperature conditions, and for other application scenarios and conditions, the selected parameters may be different, and it should be noted that the database parameter selection may also be other values, which is not limited herein.
In step S5, the original gas transmittance is two gas absorption spectrum curves of the UP section UP and the DOWN section DOWN of the laser scanning, the two curves are fitted, the fitting method used in this example is lorentz equation fitting, the abscissa of the fitting parameter is wavelength, and the ordinate is the transmittance of the gas absorption spectrum curve or the gas absorbance. The corresponding fitting wavelength center is 1653.727nm, and the corresponding fitting wavelength range is 1653.5-1653.9nm.
As shown in fig. 5, the abscissa represents the wavelength dimension corresponding to the gas absorption spectrum curves at different wavelengths.
In step S5, gas concentration inversion is performed according to the theoretical gas absorption spectrum curve lookup table and the received gas absorption spectrum curve, and error calculation is performed on the calculated gas absorption spectrum curve and the theoretical gas absorption spectrum curve, because the theoretical gas absorption spectrum curve in the lookup table has a one-to-one correspondence with the concentration value, when the error calculation value is minimum, the concentration corresponding to the gas absorption spectrum curve participating in calculation in the lookup table is the optimal inversion value. The calculated gas absorption spectrum curve fitting diagram is shown in fig. 6, the error calculation method is to calculate the residual square sum of the corresponding wavelength signals, and the calculation formula is as follows:
，
in the method, in the process of the invention,error sum of squares corresponding to two gas absorption spectrum signals,>for the gas absorption spectrum curve calculated from the actual echo signal,/->Look-up table data of theoretical gas absorption spectrum curves established for corresponding theoretical databases.
Referring to fig. 7, a single photon time-dependent ranging and gas concentration detection apparatus provided in an embodiment of the present invention includes one or more processors configured to implement the single photon time-dependent ranging and gas concentration detection method in the above embodiment.
The embodiment of the single photon time related ranging and gas concentration detecting device can be applied to any device with data processing capability, such as a computer, and the like. The apparatus embodiments may be implemented by software, or may be implemented by hardware or a combination of hardware and software. Taking software implementation as an example, the device in a logic sense is formed by reading corresponding computer program instructions in a nonvolatile memory into a memory by a processor of any device with data processing capability. In terms of hardware, as shown in fig. 7, a hardware structure diagram of an apparatus with optional data processing capability where a single photon time-dependent distance measurement and gas concentration detection apparatus of the present invention is located is shown in fig. 7, and in addition to a processor, a memory, a network interface, and a nonvolatile memory shown in fig. 7, the manufacture of the apparatus with optional data processing capability in the embodiment generally depends on the actual function of the apparatus with optional data processing capability, and may further include other hardware, which is not described herein.
The implementation process of the functions and roles of each unit in the above device is specifically shown in the implementation process of the corresponding steps in the above method, and will not be described herein again.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The embodiment of the invention also provides a readable storage medium, on which a program is stored, which when executed by a processor, implements a single photon time dependent ranging and gas concentration detection method in the above embodiment.
The readable storage medium may be an internal storage unit, such as a hard disk or a memory, of any of the data processing apparatus described in any of the previous embodiments. The readable storage medium may also be an external storage device, such as a plug-in hard disk, a Smart Media Card (SMC), an SD Card, a Flash memory Card (Flash Card), or the like, provided on the apparatus. Further, the readable storage medium may include both internal storage units and external storage devices of any data processing device. The readable storage medium is used for storing the computer program and other programs and data required by the arbitrary data processing apparatus, and may also be used for temporarily storing data that has been output or is to be output.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (8)
1. A single photon time-dependent ranging and gas concentration detection method, comprising the steps of:
step S1, performing high-speed modulation and pseudo-random coding on a laser emission signal, determining a pseudo-random coding time interval and a sequence length, generating a reference polarization pseudo-random coding signal, emitting the laser signal into a target environment, and ensuring the effect of irradiating laser to a long-distance hard target and covering a gas leakage path;
s2, receiving scattered signals of the laser irradiation surface through a time correlation counting module, and improving the signal to noise ratio through signal accumulation of a laser sweep period;
step S3, performing cross-correlation operation on the accumulated signals and the reference polarization pseudo-random code signals to obtain abscissa positions corresponding to the correlation maximum values, wherein the abscissa positions correspond to shift coordinate values, and calculating the distance information of the detected hard target by combining the pseudo-random code time interval in the step S1; the process of calculating the distance information of the detected hard target object is as follows:
，
，
wherein,echo signals acquired for a time-dependent counting module, < >>Pseudo-randomly encoded signal for transmitted reference polarization, < >>For the correlation strength signal of the echo signal and the polarization pseudo-random encoded signal,/for the echo signal>For the shift value with the largest correlation, R is the calculated detection distance, c is the speed of light, N is the length of the pseudorandom sequence, and k is the shift abscissa value;
step S4, shifting the accumulated signals according to the abscissa shift coordinate value corresponding to the maximum value calculated by the cross-correlation operation, extracting the corresponding signal amplitude values at different wavelengths, and dividing the signals of the ascending section and the descending section of the laser sweep to obtain an original gas absorption spectrum curve;
step S5, a theoretical gas absorption spectrum curve lookup table is constructed, signal fitting is carried out according to the collected gas absorption spectrum curve to obtain a gas absorption spectrum curve signal, error calculation is carried out on the theoretical gas absorption spectrum curve lookup table and the gas absorption spectrum curve signal to obtain a minimum error value, and the minimum error value is substituted into the theoretical gas absorption spectrum curve lookup table to obtain an optimal concentration value, and the method specifically comprises the following steps:
s5.1, calculating theoretical gas absorption spectrum curves under different temperatures, pressures and concentrations from a spectrum database, and constructing a theoretical gas absorption spectrum curve lookup table;
s5.2, shifting, interpolating and fitting the acquired signals to acquire a final gas absorption spectrum curve signal;
step S5.3, calculating a gas absorption spectrum curve signal under the corresponding wavelength, performing error calculation with a theoretical gas absorption spectrum curve lookup table to obtain a minimum error value, substituting the minimum error value into the theoretical gas absorption spectrum curve lookup table to calculate an optimal concentration value, wherein the error calculation process is as follows:
，
where SSE is the sum of squares of the errors,gas absorption spectrum curve calculated for the acquisition signal, +.>For the gas absorption spectrum curve in the theoretical gas absorption spectrum curve lookup table, m is the collected gas absorption spectrum curve +.>I.e. the data matrix, j represents the wavelength number of the gas absorption spectrum curve signal.
2. The method of claim 1, wherein the high-speed modulation signal used for high-speed modulating the laser emission signal in step 1 is a triangular wave sweep signal, and the pseudo-random code is an M-sequence pseudo-random code signal.
3. A single photon time dependent ranging and gas concentration detection method as claimed in claim 2 wherein the triangular wave swept signal period is consistent with the M-sequence pseudo-random code signal period length.
4. The method for measuring distance and detecting gas concentration by single photon time correlation according to claim 1, wherein the time dimension of the signal in the time correlation counting module in step S2 has a conversion relation with the interval between the laser modulation wavelength dimension, and the conversion relation is expressed as follows when calculating the gas absorption spectrum curve:
，
in the method, in the process of the invention,representing wavelength dimensional data, < >>Representing time dimension data,/->Representation->And->Is a function of the transformation relationship.
5. The method of claim 1, wherein step 5 is performed by selecting lorentz equations for fitting and selecting different wavelength intervals for interpolation fitting during signal fitting of the gas absorption spectrum curve.
6. A single photon time dependent distance measurement and gas concentration detection method according to claim 1, wherein the spectral database in step S5.1 is Hitran.
7. A single photon time dependent distance measurement and gas concentration detection apparatus comprising one or more processors configured to implement the single photon time dependent distance measurement and gas concentration detection method of any one of claims 1-6.
8. A readable storage medium, having stored thereon a program which, when executed by a processor, implements the single photon time dependent ranging and gas concentration detection method of any of claims 1-6.
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