Non-contact gas pressure detection device and method based on dual-wavelength laser interference method

Abstract

The invention provides a non-contact gas pressure detection device and method based on a dual-wavelength laser interference method. The device comprises a first laser, a second laser, a first total reflection mirror, a first double-color beam combiner, a second total reflection mirror, a beam expanding system, a beam splitter, a third total reflection mirror, a fourth total reflection mirror, a gas wedge structure measuring cavity, a beam combiner, a second double-color beam combiner, a first focusing lens, a second focusing lens, a first CCD detector, a second CCD detector, a control terminal and a to-be-measured gas source. The gas wedge structure measuring cavity comprises a reference gas cavity and a wedge-shaped gas cavity to be measured, the first laser and the second laser respectively emit a first laser beam and a second laser beam with different wavelengths, and the control terminal analyzes and processes laser interference fringe images generated by the first CCD detector and the second CCD detector to obtain gas pressure; according to the invention, high-precision non-contact measurement of the gas pressure in the cavity can be realized, measurement can be realized in a larger working range, and the device has the advantages of high accuracy and reliability.

Description

TECHNICAL FIELD

[0001] The application relates to a non-contact gas pressure detection device and method based on dual-wavelength laser interference, and belongs to the technical field of pressure detection. BACKGROUND

[0002] In many fields of industrial production and scientific research, accurate measurement of gas pressure is of great significance. For example, in the field of aerospace, the stable control of the gas pressure inside the aircraft is directly related to flight safety and normal operation of equipment; in chemical production, accurate control of the gas pressure in the reaction container can ensure that the chemical reaction proceeds as expected and avoid dangerous accidents. Traditional gas pressure measurement methods, such as mechanical pressure gauges, have limited measurement accuracy and are easily affected by environmental factors. Gas pressure measurement technology based on laser optics provides a new and effective means for gas pressure measurement with its high precision and non-contact measurement, and has gradually become a research hotspot in this field and an important way to realize quantumization of pressure measurement.

[0003] At present, the existing pressure measurement research based on laser optics basically adopts the Fabry-Perot cavity frequency method, such as the "atmospheric pressure measurement system, method, device and medium based on optical pressure standard" disclosed in Chinese invention application No. 2024102577271, the "pressure measurement device based on optical pressure standard of Fabry-Perot resonant cavity" disclosed in Chinese invention application No. 2023103618965, and the "wide-range multi-parameter vacuum measurement device and method" disclosed in Chinese invention application No. 2023109270490.

[0004] However, the above methods and explorations are all based on the laser FP cavity frequency method, which characterizes the gas pressure by the change of the FP cavity resonance frequency under different gas pressures, and realizes high-precision non-intervention measurement of gas pressure. However, there are still some deficiencies that need to be improved:

[0005] Firstly, the change of the FP cavity resonance frequency is not only related to the gas pressure, but also depends on the stability of the cavity length, so the material requirements and environmental conditions such as temperature uniformity and temperature control accuracy are extremely strict. The overall device consists of many devices, has high cost, complex operation, and high requirements for operators; secondly, in order to ensure the constant cavity length and prevent the internal gas pressure from causing the cavity length to change, the pressure of the measured gas cannot exceed atmospheric pressure, and the actual working range is very small. The FP cavity of the reference end of the optical path is generally in a vacuum state, so these factors all affect the further development of laser optical gas pressure measurement technology and greatly limit its popularization and application. SUMMARY

[0006] The application aims to provide a non-contact gas pressure detection device and method based on dual-wavelength laser interference to solve the problems of small actual working range and low accuracy and reliability of gas pressure detection in the prior art.

[0007] The technical solution of the application is:

[0008] The non-contact gas pressure detection device based on dual-wavelength laser interference comprises a laser one, a laser two, a full reflection mirror one, a dichromatic beam combiner one, a full reflection mirror two, a beam expander system, a beam splitter, a full reflection mirror three, a full reflection mirror four, a gas wedge structure measurement cavity, a beam combiner, a dichromatic beam combiner two, a focusing lens one, a focusing lens two, a CCD detector one, a CCD detector two, a control terminal, a gas source to be detected, and a gas piston pressure gauge, the gas wedge structure measurement cavity comprises a reference gas cavity and a wedge-shaped gas cavity to be detected, the wedge-shaped gas cavity to be detected is connected with the gas source to be detected, the reference gas cavity is connected with the gas piston pressure gauge, the laser one and the laser two emit laser beams one and two with different wavelengths respectively, the laser beam one is turned by the full reflection mirror one, then passes through the dichromatic beam combiner one, is turned by the full reflection mirror two again, and is expanded by the beam expander system, the laser beam two passes through the dichromatic beam combiner one, is turned by the full reflection mirror two again, and is expanded by the beam expander system, the expanded laser beam one and the expanded laser beam two are both split into two paths by the beam splitter, one path is a reference beam, which passes through the reference gas cavity of the gas wedge structure measurement cavity, is turned by the full reflection mirror three, and then enters the beam combiner, the other path is a measurement beam, which is turned by the full reflection mirror four, passes through the wedge-shaped gas cavity to be detected of the gas wedge structure measurement cavity, and then enters the beam combiner, the reference beam and the measurement beam with the same wavelength form interference with two laser beams, the interfered laser beam one is focused on the CCD detector one by the focusing lens one after being separated by the dichromatic beam combiner two, the interfered laser beam two is focused on the CCD detector two by the focusing lens two, and the control terminal analyzes and processes the laser interference fringe images generated by the CCD detector one and the CCD detector two, and obtains the gas pressure by using a gas pressure calculation method based on dual-wavelength laser interference.

[0009] Further, the gas wedge structure measurement cavity comprises a hollow cylindrical metal pipe, both ends of the hollow cylindrical metal pipe are sealed by optical glass, and the inside of the hollow cylindrical metal pipe is divided into two chambers that are independent of each other by an intermediate optical glass: an upper reference gas cavity and a lower wedge-shaped gas cavity to be detected, one end of the intermediate optical glass is connected with the front end face of the hollow cylindrical metal pipe, and the other end of the intermediate optical glass is connected with the wall of the hollow cylindrical metal pipe.

[0010] Further, the measurement beam passes through the intermediate optical glass, and the reference beam does not pass through the intermediate optical glass.

[0011] Further, the laser one is a continuous laser with a wavelength of 650 nm, and the laser two is a continuous laser with a wavelength of 532 nm.

[0012] Furthermore, the gas pressure calculation method based on dual-wavelength laser interferometry is as follows:

[0013] The first frequency signal of the equally spaced interference fringes was extracted from the laser interference fringe images of CCD detector 1 and CCD detector 2 using Fourier analysis. Second frequency signal The single-frequency real-time gas pressure measurement result, including the first pressure value, is obtained through the single-wavelength gas pressure calculation formula. Second pressure value ;

[0014] The third pressure value was obtained using the dual-wavelength synthesis theory calculation formula. :

[0015] ,

[0016] in, λ and λ' represent the wavelengths of laser beam one and laser beam two, respectively, and K is the Glaston-Dale constant. The corresponding sensitivity coefficient is determined by calibration experiments; L is the length of the gas to be measured through which the light path passes.

[0017] For the first pressure value Second pressure value and the third pressure value The three measurement results are weighted and averaged to obtain the pressure value of the gas in the wedge-shaped gas chamber to be measured.

[0018] Furthermore, the geometrical optical path lengths of the reference beam and the measurement beam are equal between the beam splitter and the beam combiner.

[0019] Furthermore, the gas wedge structure measuring cavity is equipped with a temperature control device.

[0020] Furthermore, both the gas source to be tested and the working gas of the piston pressure gauge are high-purity nitrogen.

[0021] A method for a non-contact gas pressure detection device employing the dual-wavelength laser interferometry method described above includes the following steps:

[0022] a. Setting the measurement mode: When set to absolute pressure measurement mode, the reference gas chamber is evacuated to a vacuum state by the molecular pump of the gas piston pressure gauge, and the gas pressure is less than 0.01 Pa; when set to gauge pressure measurement mode, the gas piston pressure gauge is in gauge pressure mode and outputs 5 kPa pressure.

[0023] b. The control terminal simultaneously acquires laser interference fringe images from CCD detector one and CCD detector two, and extracts the first frequency signal of the equally spaced interference fringes using Fourier analysis. Second frequency signal The single-frequency real-time gas pressure measurement result, including the first pressure value, is obtained through the single-wavelength gas pressure calculation formula. Second pressure value ;

[0024] d. The third pressure value is obtained by calculating the formula using the dual-wavelength synthesis theory. :

[0025] ,

[0026] in, λ and λ' represent the wavelengths of laser beam one and laser beam two, respectively, and K is the Glaston-Dale constant. The corresponding sensitivity coefficient is determined by calibration experiments; L is the length of the gas to be measured through which the light path passes.

[0027] f. Regarding the first pressure value Second pressure value and the third pressure value The three measurement results are weighted and averaged to obtain the pressure value of the gas in the wedge-shaped gas chamber to be measured.

[0028] Furthermore, in step f, the weight of each measurement result in the weighted average processing is the reciprocal of the variance obtained from the set number of repeated measurements of the upper limit of the system measurement during the calibration experiment.

[0029] The beneficial effects of this invention are:

[0030] I. This non-contact gas pressure detection device and method using dual-wavelength laser interferometry, based on laser coherent interferometry to invert the pressure of the gas medium inside the cavity, can achieve high-precision non-contact measurement of the gas pressure inside the cavity. It can perform measurements over a wider working range and has the advantages of high accuracy and reliability, providing a new approach for pressure measurement traceability technology.

[0031] II. This invention addresses the problem that traditional single-wavelength laser interferometers, which infer pressure changes by measuring the phase change generated after the laser passes through the gas, are easily affected by common-mode errors caused by environmental temperature fluctuations and mechanical vibrations, resulting in limited measurement accuracy. This invention employs a dual-path interference optical path to effectively cancel environmental interference, minimize common-mode errors caused by environmental temperature fluctuations and mechanical vibrations, improve measurement accuracy, and ensure data reliability and system stability.

[0032] III. This non-contact gas pressure detection device and method using dual-wavelength laser interferometry introduces a gas wedge structure into the measurement cavity to form a linearly changing phase field. The Fourier analysis method is used to quickly extract the frequency of the interference fringes, which directly corresponds to the gas pressure change. The operation is highly efficient and easy to automate, avoiding phase ambiguity.

[0033] IV. The non-contact gas pressure detection device and method of the dual-wavelength laser interference method has fast response speed of laser interference measurement technology and is suitable for dynamic and static gas pressure measurement by cooperating with high-speed image acquisition and processing technology. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a schematic diagram of the non-contact gas pressure detection device of the dual-wavelength laser interference method of the embodiment of the present application;

[0035] Figure 2 is a schematic diagram of the gas wedge structure measurement cavity in the embodiment;

[0036] Figure 3 is an interference fringe diagram of the embodiment under the actually measured absolute pressure of 500 kPa, in which the wavelength is 650 nm and 532 nm, wherein (a) is an interference fringe diagram of the laser with a wavelength of 650 nm, and (b) is an interference fringe diagram of the laser with a wavelength of 532 nm;

[0037] wherein 1 is a laser one, 2 is a laser two, 3 is a total reflection mirror one, 4 is a dichromatic beam combiner one, 5 is a total reflection mirror two, 6 is a beam expander system, 7 is a beam splitter, 8 is a total reflection mirror three, 9 is a total reflection mirror four, 10 is a gas wedge structure measurement cavity, 11 is a beam combiner, 12 is a dichromatic beam combiner two, 13 is a focusing lens one, 14 is a focusing lens two, 15 is a CCD detector one, 16 is a CCD detector two, 17 is a control terminal, 18 is a gas source to be measured, and 19 is a gas piston pressure gauge;

[0038] 101 is a reference gas cavity, 102 is a wedge-shaped gas cavity to be measured, 103 is a hollow cylindrical metal pipe, 104 is optical glass, and 105 is intermediate optical glass. DETAILED DESCRIPTION

[0039] The preferred embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0040] The embodiment provides a non-contact gas pressure detection device of a dual-wavelength laser interference method, as shown in Figure 1, including laser one 1, laser two 2, full reflection mirror one 3, double color beam combining mirror one 4, full reflection mirror two 5, beam expander system 6, beam splitter 7, full reflection mirror three 8, full reflection mirror four 9, gas wedge structure measurement cavity 10, beam combining mirror 11, double color beam combining mirror two 12, focusing lens one 13, focusing lens two 14, CCD detector one 15, CCD detector two 16, control terminal 17, gas source to be measured 18 and gas piston pressure gauge 19, the gas wedge structure measurement cavity 10 includes reference gas cavity 101 and wedge-shaped gas cavity to be measured 102, the wedge-shaped gas cavity to be measured 102 is communicated with the gas source to be measured 18, the reference gas cavity 101 is communicated with the gas piston pressure gauge 19, the laser one 1 and the laser two 2 respectively emit laser beams one and two of different wavelengths, the laser beam one is turned by the full reflection mirror one 3, then passes through the double color beam combining mirror one 4, and is turned by the full reflection mirror two 5 and expanded by the beam expander system 6, the laser beam two passes through the double color beam combining mirror one 4, is turned by the full reflection mirror two 5 and expanded by the beam expander system 6, the expanded laser beam one and the expanded laser beam two are both divided into two paths by the beam splitter 7, one path is a reference beam, which passes through the reference gas cavity 101 of the gas wedge structure measurement cavity 10, is turned by the full reflection mirror three 8 and enters the beam combining mirror 11, the other path is a measurement beam, which is turned by the full reflection mirror four 9, passes through the wedge-shaped gas cavity to be measured 102 of the gas wedge structure measurement cavity 10 and enters the beam combining mirror 11, the reference beam and the measurement beam of the same wavelength form interference with two laser beams, the interfered laser beam one is focused on the CCD detector one 15 by the focusing lens one 13 after being separated by the double color beam combining mirror two 12, the interfered laser beam two is focused on the CCD detector two 16 by the focusing lens two 14, the control terminal 17 analyzes and processes the laser interference fringe images generated by the CCD detector one 15 and the CCD detector two 16 and obtains the gas pressure by using the gas pressure calculation method based on the double-wavelength laser interference.

[0041] The non-contact gas pressure detection device based on the double-wavelength laser interference method can realize high-precision non-contact measurement of the gas pressure in the cavity, can realize measurement in a larger working range, has the advantages of high accuracy and reliability, and provides a new idea for pressure measurement traceability technology.

[0042] As Figure 2The gas wedge structure measurement cavity 10 comprises a hollow cylindrical metal tube 103, two ends of the hollow cylindrical metal tube 103 are respectively sealed by optical glass 104, the inside of the hollow cylindrical metal tube 103 is divided into two chambers which are independent of each other by intermediate optical glass 105, the upper chamber is a reference gas cavity 101, and the lower chamber is a wedge-shaped gas cavity to be measured 102, one end of the intermediate optical glass 105 is connected to the front end face of the hollow cylindrical metal tube 103, and the other end of the intermediate optical glass 105 is connected to the wall of the hollow cylindrical metal tube 103. The measurement light beam passes through the intermediate optical glass 105, and the reference light beam does not pass through the intermediate optical glass 105.

[0043] The non-contact gas pressure detection device of the dual-wavelength laser interference method, the laser one 1 adopts a continuous laser with a wavelength of 650nm, and the laser two 2 adopts a continuous laser with a wavelength of 532nm.

[0044] The gas pressure calculation method based on dual-wavelength laser interference is as follows:

[0045] The first frequency signal and the second frequency signal of the equidistant interference fringes are extracted from the laser interference fringe images of the CCD detector one 15 and the CCD detector two 16 by using the Fourier analysis method The single-frequency gas real-time pressure measurement results including the first pressure value and the second pressure value are obtained by using a single-wavelength gas pressure calculation formula.

[0046] The third pressure value is obtained by using a dual-wavelength synthesis theoretical calculation formula

[0047]

[0048] Wherein, λ1 and λ2 are the wavelengths of the laser beam one and the laser beam two respectively, K is the Grashof-Daier constant, is the corresponding sensitive coefficient, which is determined by a calibration experiment; and L is the length of the gas to be measured through which the light path passes.

[0049] The first pressure value , the second pressure value and the third pressure value are weighted and averaged to obtain the pressure value of the gas in the wedge-shaped gas cavity to be measured 102.

[0050] The above gas pressure calculation method based on dual-wavelength laser interference significantly improves the anti-interference ability and measurement resolution, and can realize high-precision, non-contact dynamic / static monitoring of gas pressure.

[0051] ​​​The geometric optical path of the reference light beam and the measurement light beam between the beam splitter 7 and the beam combiner 11 is equal, which reduces the influence of environmental factors on a single light beam and improves the accuracy of the measurement result of the laser interference fringe phase field distribution. The gas wedge structure measurement cavity 10 is provided with a temperature control device to ensure that the uniformity of the internal temperature of the measurement cavity is not greater than 0.01℃. The working gas of the measured gas source 18 and the piston pressure gauge 19 is high-purity nitrogen. In a specific example, the hollow cylindrical metal pipe 103 of the gas wedge structure measurement cavity 10 has an outer diameter of 6cm and a length of 10cm, and the middle optical glass 105 is obliquely cut along the front end face diameter of the hollow cylindrical metal pipe 103 to the pipe wall end of the hollow cylindrical metal pipe 103. The output power of the laser one 1 and the laser two 2 is 10mW. For the collected interference fringe image, the Fourier analysis method is used to extract the frequency to represent the slope of the phase field.

[0052] The embodiment also provides a method of a non-contact gas pressure detection device using the dual-wavelength laser interference method described in any one of the above, comprising the following steps:

[0053] a. Set the measurement mode: when set to absolute pressure measurement mode, the reference gas cavity 101 is pumped to a vacuum state by the molecular pump of the gas piston pressure gauge 19, and the gas pressure is less than 0.01Pa; when set to gauge pressure measurement mode, the gas piston pressure gauge 19 is in gauge pressure mode and outputs a pressure of 5kPa;

[0054] b. Control the terminal 17 to simultaneously collect the laser interference fringe images of the CCD detector one 15 and the CCD detector two 16, as shown in Figure 3 , Figure 3 (a) is a 650nm wavelength laser interference fringe image, Figure 3 (b) is a 532nm wavelength laser interference fringe image, and the Fourier analysis method is used to extract the first frequency signal and the second frequency signal of the equally spaced interference fringes, respectively. The single-frequency gas real-time pressure measurement result includes a first pressure value and a second pressure value

[0055] ;

[0056] ,

[0057] wherein, λ1 and λ2 are the wavelengths of the laser beam one and the laser beam two, respectively, K is the Grashof-Dailey constant, is the corresponding sensitivity coefficient, which is determined by a calibration experiment; and L is the length of the light path through the measured gas. ​

[0058] f、 the first pressure value , the second pressure value and the third pressure value , the three measurement results are weighted and averaged to obtain the pressure value of the gas in the wedge-shaped gas cavity 102 to be measured.

[0059] In step f, the weight of each measurement result in the weighted average processing is the reciprocal of the variance obtained by repeatedly measuring the upper limit of the system measurement (500 kPa absolute pressure) for a certain number of times, such as 10 times, during the calibration experiment.

[0060] The non-contact gas pressure detection method of the dual-wavelength laser interference method can provide accurate pressure reference values in the gauge pressure mode, and can prevent the influence of changes in the properties of the gas in the reference cavity 101 on the accuracy of the measurement results.

[0061] The present application, aiming at the problem that the traditional single-wavelength laser interferometer is easily affected by common-mode errors caused by environmental temperature fluctuations, mechanical vibrations, etc., and the measurement accuracy is limited, adopts a dual-interference optical path, effectively eliminates environmental interference, minimizes common-mode errors such as environmental temperature fluctuations and mechanical vibrations, improves measurement accuracy, and ensures data reliability and system stability.

[0062] The non-contact gas pressure detection device and method of the dual-wavelength laser interference method measure the phase field with linear changes by introducing the gas wedge structure into the measurement cavity, and use the Fourier analysis method to quickly extract the frequency of the interference fringes, which directly corresponds to the change of gas pressure, so that the operation efficiency is high and easy to automate, and the phase ambiguity phenomenon is avoided.

[0063] The non-contact gas pressure detection device and method of the dual-wavelength laser interference method have fast response speed of laser interference measurement technology, and are suitable for dynamic and static gas pressure measurement by cooperating with high-speed image acquisition and processing technology.

[0064] The physical principle of the present application is based on the laser interference phenomenon and the correlation between the refractive index of the gas and the pressure. The specific description is as follows:

[0065] 1) Correlation between gas refractive index and pressure: When a laser beam of a specific wavelength passes through the gas to be measured, the change in the density of the gas molecules will cause the refractive index to change, and the gas refractive index n is approximately linearly related to the pressure: n ≈ 1 + KP, where K is the Gladstone-Dale constant, and P is the gas pressure. Therefore, by analyzing the change of the laser interference fringes, the change of the gas pressure can be characterized.

[0066] 2) For the traditional laser interferometry, when the phase change of the measuring beam exceeds half a wavelength, the phase change cannot correspond to the optical path difference, resulting in phase ambiguity, which leads to low measurement accuracy. In the present application, the structure of the measuring cavity is changed to a wedge shape, the measuring beam passes through the wedge-shaped gas cavity 102 to be measured, and the phase field changes uniformly and linearly. After interference with the reference beam, equally spaced interference fringes are formed. The slope of different gas pressures is different. The greater the gas pressure, the more intense the phase field changes, and the more dense the interference fringes formed. Therefore, the frequency of the interference fringes can be used to represent the gas pressure, that is,

[0067] For the single-wavelength gas pressure change amount ΔP:

[0068]

[0069] wherein, is the sensitive coefficient, λ is the wavelength, is the single-wavelength interference fringe frequency value at a certain gas pressure, L is the length of the optical path through the gas to be measured, and K is the Grasston-Dale constant;

[0070] For the double-wavelength synthesized gas pressure change amount ΔP:

[0071]

[0072] wherein, is the frequency difference of the double-wavelength, and are the corresponding sensitive coefficients, which can be determined by calibration experiments.

[0073] The non-contact gas pressure detection device and method of the double-wavelength laser interferometry can obtain more data, and the accuracy is significantly higher than that of the single-wavelength design. The frequency analysis method used in data processing has higher accuracy and stability than the conventional method of measuring the movement of interference fringes. In the laboratory, compared with the 0.005-grade piston pressure gauge 19, in the pressure range of (5-400) kPa (gauge pressure) / (0-500) kPa (absolute pressure), the deviation between the system measurement value and the standard pressure value is less than ± 0.01% FS, and the performance is greatly improved.

[0074] The above examples only illustrate the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical solution falls within the protection scope of the present application.

Claims

1. A non-contact gas pressure detecting apparatus of a dual-wavelength laser interferometry characterized by: The application relates to a gas pressure measuring device, which comprises a laser one, a laser two, a full reflection mirror one, a double-color beam combining mirror one, a full reflection mirror two, a beam expanding system, a beam splitter, a full reflection mirror three, a full reflection mirror four, a gas wedge structure measuring cavity, a beam combining mirror, a double-color beam combining mirror two, a focusing lens one, a focusing lens two, a CCD detector one, a CCD detector two, a control terminal, a gas source to be measured and a gas piston pressure gauge, the gas wedge structure measuring cavity comprises a reference gas cavity and a wedge-shaped gas cavity to be measured, the wedge-shaped gas cavity to be measured is communicated with the gas source to be measured, the reference gas cavity is communicated with the gas piston pressure gauge, the laser one and the laser two respectively emit laser beams one and two with different wavelengths, the laser beam one is turned by the full reflection mirror one, then passes through the double-color beam combining mirror one, is turned by the full reflection mirror two and is expanded by the beam expanding system, the laser beam two passes through the double-color beam combining mirror one, is turned by the full reflection mirror two and is expanded by the beam expanding system, the expanded laser beam one and the expanded laser beam two are both divided into two paths by the beam splitter, one path is a reference light beam which passes through the reference gas cavity of the gas wedge structure measuring cavity, is turned by the full reflection mirror three and then enters the beam combining mirror, the other path is a measuring light beam which is turned by the full reflection mirror four, passes through the wedge-shaped gas cavity to be measured of the gas wedge structure measuring cavity and then enters the beam combining mirror, the reference light beam and the measuring light beam with the same wavelength form interference with two laser beams, the interfered laser beam one is focused on the CCD detector one by the focusing lens one, the interfered laser beam two is focused on the CCD detector two by the focusing lens two, the control terminal analyzes and processes the laser interference fringe images generated by the CCD detector one and the CCD detector two and obtains the gas pressure by using a gas pressure calculation method based on double-wavelength laser interference.

2. The non-contact gas pressure detecting apparatus of the dual-wavelength laser interferometry according to claim 1, wherein: The gas wedge structure measuring cavity comprises a hollow cylindrical metal pipe, the two ends of the hollow cylindrical metal pipe are sealed by optical glass, the inside of the hollow cylindrical metal pipe is divided into two chambers which are independent of each other by an intermediate optical glass, the upper chamber is a reference gas cavity and the lower chamber is a wedge-shaped gas cavity to be measured, one end of the intermediate optical glass is connected with the front end face of the hollow cylindrical metal pipe and the other end of the intermediate optical glass is connected with the wall of the hollow cylindrical metal pipe.

3. The non-contact gas pressure detecting apparatus of the dual-wavelength laser interferometry according to claim 2, wherein: The measuring light beam passes through the intermediate optical glass and the reference light beam does not pass through the intermediate optical glass.

4. The non-contact gas pressure detecting apparatus of the dual-wavelength laser interferometry according to claim 1, wherein: The laser one is a continuous laser with a wavelength of 650 nm and the laser two is a continuous laser with a wavelength of 532 nm.

5. The non-contact gas pressure measuring apparatus by two-wavelength laser interferometry according to any one of claims 1 to 4, characterized by: The gas pressure calculation method based on double-wavelength laser interference is as follows: The first frequency signal and the second frequency signal of the equal-interval interference fringes are extracted from the laser interference fringe images of the CCD detector one and the CCD detector two respectively and the second frequency signal , and the single-frequency gas real-time pressure measurement results including the first pressure value and the second pressure value are obtained through a single-wavelength gas pressure calculation formula The third pressure value is obtained using a two-wavelength synthesis theoretical calculation formula : ， wherein, respectively the wavelength of the laser beam one and the laser beam two, K is the Grashof number, is the corresponding sensitivity coefficient, determined by calibration experiments; L is the length of the gas to be measured through which the optical path passes. The first pressure value , the second pressure value and the third pressure value are weighted and averaged to obtain the pressure value of the gas in the wedge-shaped cavity to be measured.

6. The non-contact gas pressure measuring apparatus by two-wavelength laser interferometry according to any one of claims 1 to 4, characterized by: The geometric optical path of the reference light beam and the measuring light beam between the beam splitter and the beam combining mirror is equal.

7. The non-contact gas pressure measuring apparatus by two-wavelength laser interferometry according to any one of claims 1 to 4, characterized by: The gas wedge structure measuring cavity is provided with a temperature control device.

8. The non-contact gas pressure measuring apparatus by two-wavelength laser interferometry according to any one of claims 1 to 4, characterized by: The working gas of the gas source to be measured and the piston pressure gauge is high-purity nitrogen.

9. A method of non-contact gas pressure detection using the dual-wavelength laser interferometry of any one of claims 1 to 8, characterized by: The application further discloses a gas pressure measurement method, which comprises the following steps: a, setting the measurement mode: when the absolute pressure measurement mode is set, the reference gas cavity is pumped to a vacuum state by the molecular pump of the gas piston pressure gauge, and the gas pressure is less than 0.01 Pa; when the gauge pressure measurement mode is set, the gas piston pressure gauge is in the gauge pressure mode and outputs a pressure of 5 kPa; b. The control terminal simultaneously collects the laser interference fringe images of the CCD detector one and the CCD detector two, respectively adopts the Fourier analysis method to extract the first frequency signal of the equal interval interference fringe And the second frequency signal , obtains the single frequency gas real-time pressure measurement result including the first pressure value , the second pressure value Through the single wavelength gas pressure calculation formula d. The third pressure value is obtained using the two-wavelength synthesis theoretical calculation formula : ， wherein, respectively the wavelength of the laser beam one and the laser beam two, K is the Grashof number, is the corresponding sensitivity coefficient, determined by calibration experiments; L is the length of the gas to be measured through which the optical path passes. f、 the first pressure value , the second pressure value , and the third pressure value , the three measurement results are weighted and averaged to obtain the pressure value of the gas in the wedge-shaped cavity to be measured.

10. The method of non-contact gas pressure detection using dual-wavelength laser interferometry according to claim 9, wherein: In step f, the weight of each measurement result in the weighted average processing is the inverse of the variance obtained by repeatedly measuring the upper limit of the system in the calibration experiment for a set number of times.

Images