Implementation method and device for rapidly scanning CRDS sensing

Abstract

The invention discloses an implementation method and device for fast scanning CRDS sensing, and relates to the technical field of ring-down cavities, and the method comprises the following steps: employing a PID algorithm to control and adjust the temperature and pressure in a ring-down cavity to stabilize the resonance mode of the ring-down cavity, and carrying out the collection operation of a cavity mode signal after the adjustment of the temperature and pressure is completed; obtaining a wavelength value of the laser light source after entering the etalon based on the transmittance value, feeding back the wavelength value to a wavelength controller, and adjusting the laser to a spectrum detection wavelength by using the wavelength controller; scanning operation is executed based on the detection wavelength to determine the resonant wavelength, secondary scanning is performed with the resonant wavelength as the center to obtain a ring-down curve, and gas characteristic absorption line measurement is completed through point-by-point scanning. According to the invention, the etalon, the precise wavelength locking and adjusting system and the unique cavity mode scanning mode are utilized to realize high-repetition-frequency rapid scanning of the ring-down signal, so that the triggering speed of the ring-down event is improved.

Description

Technical Field

[0001] The present invention relates to the field of ring-down cavity technology, and in particular to a method and device for realizing fast scanning CRDS sensing. Background Art

[0002] At present, CRDS (Cavity Ring-Down Spectroscopy) technology is widely used in the field of trace gas detection. It is a recognized accurate measurement scheme that relies on a high-fineness resonant cavity. The detection signal-to-noise ratio and sensitivity are 3 to 4 orders of magnitude higher than traditional measurement methods. It is a detection technology specified in many domestic national standards for atmospheric component observations. CRDS technology uses the absorption spectral line characteristics of the substance to be measured for quantitative analysis, and CRDS technology measures the absolute absorption coefficient of the medium in the cavity, so it can be calibrated-free and can still guarantee high accuracy and precision for long-term measurements.

[0003] In the CRDS system for measuring trace gases, the measurement speed of the system is an important factor affecting the gas detection accuracy. The faster the measurement speed per unit time, the more average times, so the higher the detection accuracy. Furthermore, in conventional CRDS detection systems, in order to ensure that the ring-down curve can be scanned each time, the wavelength scanning range is often wider, generally about 1 FSR (free spectral range).

[0004] When scanning a cavity mode signal with a large amplitude, the scanning rate will not be too high, generally in the Hz range. If you want to obtain the entire absorption spectrum of the gas, it may take tens of seconds, resulting in low detection accuracy. In addition, the gas concentration may change during this time, introducing a large measurement error.

[0005] Currently, no effective solution has been proposed for the problems in the related technologies. Summary of the invention

[0006] In view of the problems in the related art, the present invention proposes a method and device for realizing fast scanning CRDS sensing to overcome the above technical problems existing in the existing related art.

[0007] To this end, the specific technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for implementing fast scanning CRDS sensing, the method for implementing fast scanning CRDS sensing comprising the following steps:

[0009] S1. Use PID algorithm to control and adjust the temperature and pressure in the ring-down cavity to stabilize the resonance mode of the ring-down cavity, and perform cavity mode signal acquisition operation after the temperature and pressure are adjusted;

[0010] S2, obtaining the wavelength value of the laser light source after entering the etalon based on the transmittance value, and feeding the wavelength value back to the wavelength controller, and using the wavelength controller to adjust the laser to the spectrum detection wavelength;

[0011] S3. Perform a scanning operation based on the detection wavelength to determine the resonance wavelength, perform a secondary scan with the resonance wavelength as the center to obtain a ring-down curve, and scan point by point to complete the measurement of the gas characteristic absorption spectrum.

[0012] Preferably, using a PID algorithm to control and adjust the temperature and pressure in the ring-down cavity to stabilize the resonance mode of the ring-down cavity, and performing a cavity mode signal acquisition operation after the temperature and pressure are adjusted includes the following steps:

[0013] S11, averaging the temperature values ​​collected by several groups of temperature sensors in the ring-down cavity, and taking the average value as the ring-down cavity temperature;

[0014] S12, comparing the error between the ring-down cavity temperature and the set temperature, and combining the error result with the PID algorithm to determine the linear semiconductor refrigerator control signal;

[0015] S13, using a linear semiconductor cooler control signal to change the ring-down cavity temperature so that the changed ring-down cavity temperature is aligned with the set temperature;

[0016] S14, after completing the temperature control of the ring-down cavity, adjusting the proportional valve opening by using proportional-integral-differential operation to control the pressure value in the ring-down cavity, so as to stabilize the resonance mode of the ring-down cavity;

[0017] S15, after adjusting the temperature and pressure, generate and collect the cavity model signal.

[0018] Preferably, after completing the temperature control of the ring-down cavity, adjusting the proportional valve opening by proportional-integral-differential operation to control the pressure value in the ring-down cavity and stabilizing the resonance mode of the ring-down cavity comprises the following steps:

[0019] S141, after completing the temperature stabilization control of the ring-down cavity, using a pressure sensor to collect the real-time pressure in the ring-down cavity, and comparing the real-time pressure with the set pressure to obtain a pressure error value;

[0020] S142, combining the pressure error value with the PID algorithm to obtain a proportional valve control signal, and using the proportional valve control signal to adjust the proportional valve opening size to regulate the pressure in the ring-down chamber.

[0021] Preferably, after adjusting the temperature and pressure, the generation and collection of the cavity mode signal comprises the following steps:

[0022] S151, after the temperature and pressure are adjusted, determining whether the adjusted temperature and pressure of the ring-down cavity meet the preset requirements, and readjusting the temperature and pressure when the temperature and pressure of the ring-down cavity meet the preset requirements;

[0023] S152, when the temperature and pressure of the ring-down cavity meet the preset requirements, an adjustment completion signal is fed back to the main controller;

[0024] S153, when the main controller receives the signal that the temperature and pressure control adjustment of the ring-down cavity is completed, it starts to execute the cavity mold signal acquisition operation.

[0025] Preferably, obtaining the wavelength value of the laser light source after entering the etalon based on the transmittance value, and feeding the wavelength value back to the wavelength controller, and using the wavelength controller to adjust the laser to the spectrum detection wavelength includes the following steps:

[0026] S21, the laser output is beam split and then passed through an etalon to measure the reflected light intensity and the transmitted light intensity of the laser beam after passing through the etalon;

[0027] S22, determining a transmittance value based on a ratio between the reflected light intensity and the transmitted light intensity, and obtaining a wavelength value of a laser output by the laser according to a curve of a relationship between the transmittance value and the wavelength;

[0028] S23, the etalon obtains the wavelength value and feeds it back to the wavelength controller, and the wavelength controller receives the wavelength setting value set by the master controller;

[0029] S24, the wavelength controller reads the wavelength setting value and the wavelength value adjusts the laser to the wavelength setting value issued by the main controller.

[0030] Preferably, the wavelength controller reads the wavelength setting value and the wavelength value adjusts the laser to the wavelength setting value sent by the master controller, including the following steps:

[0031] S241, the wavelength controller reads the wavelength setting value and the wavelength value and calculates the error signal between the two;

[0032] S242, combining the error signal with the control algorithm to perform proportional, integral and differential gain operations, calculating the adjustment coefficient of the laser current and sending it to the laser current controller;

[0033] S243, after receiving the adjustment coefficient, the laser current controller repeatedly performs the laser wavelength adjustment work until the laser output wavelength reaches the wavelength setting value, and the laser output wavelength is locked to the set wavelength value issued by the main controller.

[0034] Preferably, performing a scanning operation based on the detection wavelength to determine the resonance wavelength, performing a secondary scan with the resonance wavelength as the center to obtain a ring-down curve, and scanning point by point to complete the measurement of the characteristic absorption spectrum of the gas includes the following steps:

[0035] S31, determining the resonance wavelength based on the scanning scheme corresponding to the cavity mode signal acquisition result and the resonance mode in combination with the laser current controller;

[0036] S32, after setting the laser wavelength to a first wavelength based on the resonance wavelength, performing a scanning operation within a preset range, and determining an accurate value of the resonance wavelength according to the scanning result;

[0037] S33, performing scanning at a preset speed within a fixed range with the precise wavelength value as the center, obtaining a ring-down curve according to the scanning result, and determining a ring-down signal based on the ring-down curve;

[0038] S34. Repeat the scanning process according to the number of points of the resonance wavelength until the measurement of the entire gas characteristic absorption spectrum is completed.

[0039] Preferably, determining the resonance wavelength based on the cavity mode signal acquisition result and the scanning scheme corresponding to the resonance mode in combination with the laser current controller comprises the following steps:

[0040] S311, selecting a predefined scanning scheme based on the cavity mode signal acquisition result and the resonance mode, and feeding back the scanning logic of the scanning scheme to the laser current controller;

[0041] S312, the laser current controller analyzes the scanning logic, performs wavelength scanning within the characteristic absorption spectrum of the gas, preliminarily determines that the scanning wavelength is correct, and records the resonance wavelength value of the resonance position.

[0042] Preferably, repeatedly performing the scanning operation according to the number of points of the resonance wavelength until the measurement of the entire gas characteristic absorption spectrum is completed includes the following steps:

[0043] S341, after scanning of a resonance wavelength, switching to the next wavelength, repeating the scanning logic of steps S31 to S33 to obtain a ring-down curve, until the scanning range covers the complete characteristic absorption spectrum of the gas;

[0044] S332, recording the resonance position wavelength and ring-down signal data of each point during the resonance wavelength scanning process, and completing the measurement of the characteristic absorption spectrum of the gas.

[0045] In a second aspect, the present invention further provides a device for implementing fast scanning CRDS sensing, the device comprising:

[0046] The temperature and pressure adjustment unit is used to control and adjust the temperature and pressure in the ring-down cavity by using a PID algorithm to stabilize the resonance mode of the ring-down cavity, and to collect cavity mode signals after the temperature and pressure are adjusted;

[0047] A detection wavelength determination unit is used to obtain the wavelength value of the laser light source after entering the etalon based on the transmittance value, and feed the wavelength value back to the wavelength controller, and use the wavelength controller to adjust the laser to the spectrum detection wavelength;

[0048] The absorption spectrum line measurement unit is used to perform a scanning operation based on the detection wavelength to determine the resonance wavelength, perform a secondary scan with the resonance wavelength as the center to obtain a ring-down curve, and scan point by point to complete the measurement of the gas characteristic absorption spectrum line.

[0049] The beneficial effects of the present invention are:

[0050] The present invention utilizes an etalon, a precision wavelength locking adjustment system and a unique cavity mode scanning method to accurately lock the laser wavelength at the resonant position of the laser resonant cavity, thereby realizing rapid establishment of the cavity mode signal and high repetition frequency rapid scanning of the ring-down signal, so as to improve the detection speed of the system, improve the sensitivity, and further accelerate the triggering speed of the ring-down event, improve the measurement speed of the gas characteristic absorption spectrum, and thus increase the accuracy of gas measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0052] Figure 1 is a flow chart of a method for implementing fast scanning CRDS sensing according to an embodiment of the present invention;

[0053] Figure 2 This is a process for implementing a wavelength controller to control laser current in a method for implementing a fast scanning CRDS sensor according to an embodiment of the present invention;

[0054] Figure 3 is a schematic diagram of the wavelength of transmitted light intensity in a method for realizing fast scanning CRDS sensing according to an embodiment of the present invention;

[0055] Figure 4 is a schematic diagram of the frequency of transmitted light intensity in a method for realizing fast scanning CRDS sensing according to an embodiment of the present invention;

[0056] Figure 5 It is a scanning logic schematic diagram in a method for implementing fast scanning CRDS sensing according to an embodiment of the present invention;

[0057] Figure 6 is a schematic diagram of a device for implementing fast scanning CRDS sensing according to an embodiment of the present invention.

[0058] In the figure:

[0059] 1. Temperature and pressure adjustment unit; 2. Detection wavelength determination unit; 3. Absorption spectrum measurement unit. DETAILED DESCRIPTION

[0060] To further illustrate each embodiment, the present invention provides drawings, which are part of the disclosure of the present invention and are mainly used to illustrate the embodiments. They can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, ordinary technicians in this field should be able to understand other possible implementation methods and advantages of the present invention.

[0061] According to an embodiment of the present invention, a method and device for realizing fast scanning CRDS sensing are provided.

[0062] The present invention is further described with reference to the accompanying drawings and specific embodiments. Figures 1 to 5 As shown, according to the implementation method of the fast scanning CRDS sensing of the embodiment of the present invention, the implementation method of the fast scanning CRDS sensing includes the following steps:

[0063] S1. Use PID algorithm to control and adjust the temperature and pressure in the ring-down cavity to stabilize the resonance mode of the ring-down cavity, and perform cavity mode signal acquisition operation after the temperature and pressure are adjusted.

[0064] In this embodiment, the PID algorithm is used to control and adjust the temperature and pressure in the ring-down cavity to stabilize the resonance mode of the ring-down cavity, and the cavity mode signal acquisition operation is performed after the temperature and pressure are adjusted, including the following steps:

[0065] S11, averaging the temperature values ​​collected by several groups of temperature sensors in the ring-down cavity, and taking the average value as the ring-down cavity temperature;

[0066] S12, comparing the error between the ring-down cavity temperature and the set temperature, and combining the error result with the PID algorithm to determine the linear semiconductor refrigerator control signal;

[0067] S13, using a linear semiconductor cooler control signal to change the ring-down cavity temperature so that the changed ring-down cavity temperature is aligned with the set temperature;

[0068] S14. After completing the temperature control of the ring-down cavity, the proportional valve opening is adjusted using proportional-integral-differential operation to control the pressure value in the ring-down cavity, so as to stabilize the resonance mode of the ring-down cavity.

[0069] Specifically, after completing the temperature control of the ring-down cavity, the proportional valve opening is adjusted by using proportional-integral-differential operation to control the pressure value in the ring-down cavity, and the resonance mode of the ring-down cavity is stabilized, which includes the following steps:

[0070] S141, after completing the temperature stabilization control of the ring-down cavity, using a pressure sensor to collect the real-time pressure in the ring-down cavity, and comparing the real-time pressure with the set pressure to obtain a pressure error value;

[0071] S142, combining the pressure error value with the PID algorithm to obtain a proportional valve control signal, and using the proportional valve control signal to adjust the proportional valve opening size to regulate the pressure in the ring-down chamber.

[0072] S15, after adjusting the temperature and pressure, generate and collect the cavity model signal.

[0073] Specifically, after adjusting the temperature and pressure, the generation and collection of the cavity mode signal includes the following steps:

[0074] S151, after the temperature and pressure are adjusted, determining whether the adjusted temperature and pressure of the ring-down cavity meet the preset requirements, and readjusting the temperature and pressure when the temperature and pressure of the ring-down cavity meet the preset requirements;

[0075] S152, when the temperature and pressure of the ring-down cavity meet the preset requirements, an adjustment completion signal is fed back to the main controller;

[0076] S153, when the main controller receives the signal that the temperature and pressure control adjustment of the ring-down cavity is completed, it starts to execute the cavity mold signal acquisition operation.

[0077] It should be explained that the reason for precise control of the temperature of the ring-down cavity is that the temperature change of the ring-down cavity will cause the mechanical parts to expand and contract, resulting in a slight change in the length of the ring-down cavity, and the temperature change will cause the refractive index of the gas to change. The above two factors will cause the resonance mode of the ring-down cavity to change, so the temperature of the ring-down cavity needs to be precisely controlled.

[0078] First, the temperature of the ring-down cavity is controlled within ±5mK of the preset temperature, and the pressure of the ring-down cavity is controlled within ±10Pa of the set value. These two conditions are to ensure the stability of the resonance mode of the ring-down cavity. Then, the wavelength values ​​of a series of cavity mode signals generated are recorded by scanning the current over a large range.

[0079] S2. Obtain the wavelength value of the laser light source after entering the etalon based on the transmittance value, and feed the wavelength value back to the wavelength controller, and use the wavelength controller to adjust the laser to the spectrum detection wavelength.

[0080] Simply put, the function of the wavelength controller is to receive the wavelength setting value from the main controller, read the transmittance value fed back by the standard tool to calculate the current wavelength value, and use the PID algorithm to control the laser operating current so that the laser output wavelength reaches the wavelength setting value. The wavelength control accuracy is 1MHz.

[0081] In this embodiment, the wavelength value of the laser light source after entering the etalon is obtained based on the transmittance value, and the wavelength value is fed back to the wavelength controller. The wavelength controller is used to adjust the laser to the spectrum detection wavelength, including the following steps:

[0082] S21, the laser output is beam split and then passed through an etalon to measure the reflected light intensity and the transmitted light intensity of the laser beam after passing through the etalon;

[0083] S22, determining a transmittance value based on a ratio between the reflected light intensity and the transmitted light intensity, and obtaining a wavelength value of a laser output by the laser according to a curve of a relationship between the transmittance value and the wavelength;

[0084] S23, the etalon obtains the wavelength value and feeds it back to the wavelength controller, and the wavelength controller receives the wavelength setting value set by the master controller;

[0085] S24, the wavelength controller reads the wavelength setting value and the wavelength value adjusts the laser to the wavelength setting value issued by the main controller.

[0086] Specifically, the wavelength controller reads the wavelength setting value and the wavelength value adjusts the laser to the wavelength setting value issued by the main controller, including the following steps:

[0087] S241, the wavelength controller reads the wavelength setting value and the wavelength value and calculates the error signal between the two;

[0088] S242, combining the error signal with the control algorithm to perform proportional, integral and differential gain operations, calculating the adjustment coefficient of the laser current and sending it to the laser current controller;

[0089] S243, after receiving the adjustment coefficient, the laser current controller repeatedly performs the laser wavelength adjustment work until the laser output wavelength reaches the wavelength setting value, and the laser output wavelength is locked to the set wavelength value issued by the main controller.

[0090] like Figure 2 The specific flow chart of wavelength control for controlling laser current shown needs to be explained that the current wavelength transmitted by the signal acquisition standard in the wavelength controller is compared with the set wavelength input by the main control part to calculate the error signal, and the calculation unit performs proportional (P), integral (I) and differential (D) operations on the error signal to calculate the control signal of the laser current and transmit it to the laser current controller until the laser output wavelength is adjusted to the set wavelength.

[0091] The basic principle of using the etalon as a wavelength monitor is that after lasers of different wavelengths pass through the etalon, the etalon will periodically resonate and strengthen and weaken the lasers, causing lasers of different wavelengths to be incident on the etalon, and the intensity of the transmitted light will show periodicity. Figure 3As shown, however, this periodicity cannot determine the absolute wavelength of the laser output and needs to be combined with the gas absorption peak frequency.

[0092] In actual spectral detection, the gas absorption spectrum width is about several GHz (frequency), so in actual use the laser wavelength is only tuned in a small section, such as Figure 4 As shown, it is the actually used laser frequency part, which works linearly within about ±10GHz with the absorption peak frequency as the center. In the actual gas detection process, the center frequency of the characteristic absorption of the gas is absolute. Combined with the free spectrum region of the ring-down cavity, the wavelength of this local area is precisely determined.

[0093] It should be noted that the laser temperature control part in the laser controller has a laser temperature setting DAC (Digital to Analog Converter) of 16-Bit, a laser temperature setting step of 14mK, and a precisely adjusted hardware PID combined with a linear semiconductor cooler TEC (Thermoelectric cooler) control, and the laser temperature stability reaches ±4mK.

[0094] At the same time, the laser current control unit in the laser controller adopts 16-BitDAC, and the laser working current adjustment step reaches 0.3μA. For the semiconductor laser with a current tuning coefficient of 0.005nm / mA commonly used in CRDS gas sensing equipment, the wavelength tuning resolution is 1.5fm, which is converted to a frequency tuning resolution of 165kHz, providing a basis for achieving precise control of the laser wavelength.

[0095] S3. Perform a scanning operation based on the detection wavelength to determine the resonance wavelength, perform a secondary scan with the resonance wavelength as the center to obtain a ring-down curve, and scan point by point to complete the measurement of the gas characteristic absorption spectrum.

[0096] In this embodiment, performing a scanning operation based on the detection wavelength to determine the resonance wavelength, performing a secondary scan with the resonance wavelength as the center to obtain a ring-down curve, and scanning point by point to complete the measurement of the characteristic absorption spectrum of the gas includes the following steps:

[0097] S31, determining the resonance wavelength based on the scanning scheme corresponding to the cavity mode signal acquisition result and the resonance mode in combination with the laser current controller;

[0098] S32, after setting the laser wavelength to a first wavelength based on the resonance wavelength, performing a scanning operation within a preset range, and determining an accurate value of the resonance wavelength according to the scanning result;

[0099] S33, performing scanning at a preset speed within a fixed range with the precise wavelength value as the center, obtaining a ring-down curve according to the scanning result, and determining a ring-down signal based on the ring-down curve;

[0100] S34. Repeat the scanning process according to the number of points of the resonance wavelength until the measurement of the entire gas characteristic absorption spectrum is completed.

[0101] Specifically, based on the scanning scheme corresponding to the cavity mode signal acquisition result and the resonance mode, determining the resonance wavelength in combination with the laser current controller includes the following steps:

[0102] S311, selecting a predefined scanning scheme based on the cavity mode signal acquisition result and the resonance mode, and feeding back the scanning logic of the scanning scheme to the laser current controller;

[0103] S312, the laser current controller analyzes the scanning logic, performs wavelength scanning within the characteristic absorption spectrum of the gas, preliminarily determines that the scanning wavelength is correct, and records the resonance wavelength value of the resonance position.

[0104] The scanning operation is repeatedly performed according to the number of points of the resonance wavelength until the measurement of the entire gas characteristic absorption spectrum is completed, which includes the following steps:

[0105] S341, after scanning of a resonance wavelength, switching to the next wavelength, repeating the scanning logic of steps S31 to S33 to obtain a ring-down curve, until the scanning range covers the complete characteristic absorption spectrum of the gas;

[0106] S332, recording the resonance position wavelength and ring-down signal data of each point during the resonance wavelength scanning process, and completing the measurement of the characteristic absorption spectrum of the gas.

[0107] like Figure 5 As shown, it needs to be explained that after the resonance mode of the ring-down cavity is preliminarily determined, Figure 5 The scanning scheme shown in the figure performs a fast scan. The specific scanning logic is to first set the wavelength at the first wavelength value of the resonance of the ring-down cavity measured in the previous step, and perform a frequency scan of ±10MHz to determine the precise value of the resonance wavelength. Then, a fast scan of ±2MHz is performed with the wavelength value as the center, and the scanning rate is 1MHz / ms. After scanning the wavelength, move to the next wavelength and repeat the above operation. The calculated repetition frequency of the ring-down event will be greater than 200Hz, which greatly improves the measurement speed compared to the repetition frequency of the second level of the traditional method.

[0108] like Figure 6 According to another embodiment of the present invention, the present invention also provides a device for implementing fast scanning CRDS sensing, the device comprising:

[0109] The temperature and pressure adjustment unit 1 is used to control and adjust the temperature and pressure in the ring-down cavity by using a PID algorithm to stabilize the resonance mode of the ring-down cavity, and to perform a cavity mode signal acquisition operation after the temperature and pressure are adjusted;

[0110] The detection wavelength determination unit 2 is used to obtain the wavelength value of the laser light source after entering the etalon based on the transmittance value, and feed the wavelength value back to the wavelength controller, and use the wavelength controller to adjust the laser to the spectrum detection wavelength;

[0111] The absorption spectrum line measurement unit 3 is used to perform a scanning operation based on the detection wavelength to determine the resonance wavelength, perform a secondary scan with the resonance wavelength as the center to obtain a ring-down curve, and scan point by point to complete the measurement of the gas characteristic absorption spectrum line.

[0112] In summary, with the aid of the above technical solutions of the present invention, the present invention utilizes an etalon, a precise wavelength locking adjustment system and a unique cavity mode scanning method to accurately lock the laser wavelength at the resonant position of the laser resonant cavity, which can realize the rapid establishment of the cavity mode signal and the high repetition frequency rapid scanning of the ring-down signal, so as to improve the detection speed of the system, improve the sensitivity, and thus accelerate the triggering speed of the ring-down event, improve the measurement speed of the characteristic absorption spectrum of the gas, and thus increase the accuracy of gas measurement. While realizing precise temperature and pressure control and ensuring the stability of the cavity mode signal, the present invention can also stabilize the absorption intensity of the characteristic absorption line type and transition spectrum of the gas, provide a basis for rapid scanning based on precise wavelength control, and achieve the laser temperature control accuracy of 4mK, ensuring the stability of the laser output wavelength, and finally realizing a 200Hz ring-down event, which can greatly improve the measurement speed of the gas and the measurement accuracy of the gas concentration.

[0113] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for implementing fast scanning CRDS sensing, characterized in that: The implementation method of the fast scanning CRDS sensing includes the following steps: S1. Use PID algorithm to control and adjust the temperature and pressure in the ring-down cavity to stabilize the resonance mode of the ring-down cavity, and perform cavity mode signal acquisition operation after the temperature and pressure are adjusted; S2, obtaining the wavelength value of the laser light source after entering the etalon based on the transmittance value, and feeding the wavelength value back to the wavelength controller, and using the wavelength controller to adjust the laser to the spectrum detection wavelength; S3. Perform a scanning operation based on the detection wavelength to determine the resonance wavelength, perform a secondary scan with the resonance wavelength as the center to obtain a ring-down curve, and scan point by point to complete the measurement of the gas characteristic absorption spectrum.

2. A method for implementing fast scanning CRDS sensing according to claim 1, characterized in that: The method of using a PID algorithm to control and adjust the temperature and pressure in the ring-down cavity to stabilize the resonance mode of the ring-down cavity, and performing a cavity mode signal acquisition operation after the temperature and pressure are adjusted, comprises the following steps: S11, averaging the temperature values ​​collected by several groups of temperature sensors in the ring-down cavity, and taking the average value as the ring-down cavity temperature; S12, comparing the error between the ring-down cavity temperature and the set temperature, and combining the error result with the PID algorithm to determine the linear semiconductor refrigerator control signal; S13, using a linear semiconductor cooler control signal to change the ring-down cavity temperature so that the changed ring-down cavity temperature is aligned with the set temperature; S14, after completing the temperature control of the ring-down cavity, adjusting the proportional valve opening by using proportional-integral-differential operation to control the pressure value in the ring-down cavity, so as to stabilize the resonance mode of the ring-down cavity; S15, after adjusting the temperature and pressure, generate and collect the cavity model signal.

3. A method for implementing fast scanning CRDS sensing according to claim 2, characterized in that: After completing the temperature control of the ring-down cavity, the proportional valve opening is adjusted by proportional-integral-differential operation to control the pressure value in the ring-down cavity, and the resonance mode of the ring-down cavity is stabilized, which includes the following steps: S141, after completing the temperature stabilization control of the ring-down cavity, using a pressure sensor to collect the real-time pressure in the ring-down cavity, and comparing the real-time pressure with the set pressure to obtain a pressure error value; S142, combining the pressure error value with the PID algorithm to obtain a proportional valve control signal, and using the proportional valve control signal to adjust the proportional valve opening size to regulate the pressure in the ring-down chamber.

4. The method for implementing fast scanning CRDS sensing according to claim 2, characterized in that: The generation and collection of cavity mode signals after adjusting the temperature and pressure include the following steps: S151, after the temperature and pressure are adjusted, determining whether the adjusted temperature and pressure of the ring-down cavity meet the preset requirements, and readjusting the temperature and pressure when the temperature and pressure of the ring-down cavity meet the preset requirements; S152, when the temperature and pressure of the ring-down cavity meet the preset requirements, an adjustment completion signal is fed back to the main controller; S153, when the main controller receives the signal that the temperature and pressure control adjustment of the ring-down cavity is completed, it starts to execute the cavity mold signal acquisition operation.

5. The method for implementing fast scanning CRDS sensing according to claim 1, characterized in that: The method of obtaining the wavelength value of the laser light source after entering the etalon based on the transmittance value, feeding the wavelength value back to the wavelength controller, and adjusting the laser to the spectrum detection wavelength by the wavelength controller comprises the following steps: S21, the laser output is beam split and then passed through an etalon to measure the reflected light intensity and the transmitted light intensity of the laser beam after passing through the etalon; S22, determining a transmittance value based on a ratio between the reflected light intensity and the transmitted light intensity, and obtaining a wavelength value of a laser output by the laser according to a curve of a relationship between the transmittance value and the wavelength; S23, the etalon obtains the wavelength value and feeds it back to the wavelength controller, and the wavelength controller receives the wavelength setting value set by the master controller; S24, the wavelength controller reads the wavelength setting value and the wavelength value adjusts the laser to the wavelength setting value issued by the main controller.

6. A method for implementing fast scanning CRDS sensing according to claim 5, characterized in that: The wavelength controller reads the wavelength setting value and the wavelength value adjusts the laser to the wavelength setting value issued by the main controller, including the following steps: S241, the wavelength controller reads the wavelength setting value and the wavelength value and calculates the error signal between the two; S242, combining the error signal with the control algorithm to perform proportional, integral and differential gain operations, calculating the adjustment coefficient of the laser current and sending it to the laser current controller; S243, after receiving the adjustment coefficient, the laser current controller repeatedly performs the laser wavelength adjustment work until the laser output wavelength reaches the wavelength setting value, and the laser output wavelength is locked to the set wavelength value issued by the main controller.

7. A method for implementing fast scanning CRDS sensing according to claim 6, characterized in that: The method of performing a scanning operation based on the detection wavelength to determine the resonance wavelength, performing a secondary scan with the resonance wavelength as the center to obtain a ring-down curve, and scanning point by point to complete the measurement of the characteristic absorption spectrum of the gas includes the following steps: S31, determining the resonance wavelength based on the scanning scheme corresponding to the cavity mode signal acquisition result and the resonance mode in combination with the laser current controller; S32, after setting the laser wavelength to a first wavelength based on the resonance wavelength, performing a scanning operation within a preset range, and determining an accurate value of the resonance wavelength according to the scanning result; S33, performing scanning at a preset speed within a fixed range with the precise wavelength value as the center, obtaining a ring-down curve according to the scanning result, and determining a ring-down signal based on the ring-down curve; S34. Repeat the scanning process according to the number of points of the resonance wavelength until the measurement of the entire gas characteristic absorption spectrum is completed.

8. The method for implementing fast scanning CRDS sensing according to claim 7, characterized in that: The scanning scheme based on the cavity mode signal acquisition result and the resonance mode, combined with the laser current controller, determines the resonance wavelength, including the following steps: S311, selecting a predefined scanning scheme based on the cavity mode signal acquisition result and the resonance mode, and feeding back the scanning logic of the scanning scheme to the laser current controller; S312, the laser current controller analyzes the scanning logic, performs wavelength scanning within the characteristic absorption spectrum of the gas, preliminarily determines that the scanning wavelength is correct, and records the resonance wavelength value of the resonance position.

9. A method for implementing fast scanning CRDS sensing according to claim 8, characterized in that: The scanning operation is repeatedly performed according to the number of points of the resonance wavelength until the measurement of the entire gas characteristic absorption spectrum is completed, which includes the following steps: S341, after scanning of a resonance wavelength, switching to the next wavelength, repeating the scanning logic of step S31 to step S33 to obtain the ring-down curve, until the scanning range covers the complete characteristic absorption spectrum of the gas; S332, recording the resonance position wavelength and ring-down signal data of each point during the resonance wavelength scanning process, and completing the measurement of the characteristic absorption spectrum of the gas.

10. A fast scanning CRDS sensing implementation device, used to implement the fast scanning CRDS sensing implementation method according to any one of claims 1 to 9, characterized in that: The implementation device includes: The temperature and pressure adjustment unit is used to control and adjust the temperature and pressure in the ring-down cavity by using a PID algorithm to stabilize the resonance mode of the ring-down cavity, and to collect cavity mode signals after the temperature and pressure are adjusted; A detection wavelength determination unit is used to obtain the wavelength value of the laser light source after entering the etalon based on the transmittance value, and feed the wavelength value back to the wavelength controller, and use the wavelength controller to adjust the laser to the spectrum detection wavelength; The absorption spectrum line measurement unit is used to perform a scanning operation based on the detection wavelength to determine the resonance wavelength, perform a secondary scan with the resonance wavelength as the center to obtain a ring-down curve, and complete the measurement of the gas characteristic absorption spectrum line by scanning point by point.

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