A gas-liquid refractive index measurement method based on feise interference

Abstract

The application discloses a gas-liquid refractive index measuring method based on a Fizeau interference, and belongs to the technical field of gas and liquid refractive index measurement, and comprises the following steps: vacuumizing the inside of a Fizeau interference cavity and keeping the vacuum state, and obtaining interference fringes in the state as reference data; injecting a certain amount of to-be-measured gas or liquid into the Fizeau interference cavity, and obtaining interference fringe data in a sample state; according to previously calibrated interferometer parameters in a vacuum state, combining the interference fringe data obtained in the vacuum state and the sample state, and accurately calculating corrected fringe spacing values of the Fizeau interference cavity in the vacuum state and the sample state. The refractive index is calculated based on the corrected fringe spacing values of the Fizeau interference cavity in the vacuum state and the sample state. The method improves the refractive index measurement precision by improving the signal-to-noise ratio through line integration and combining the fringe spacing correction and the interferometer parameter calibration.

Description

Technical Field

[0001] This invention relates to the field of gas and liquid refractive index measurement technology, and specifically to a gas-liquid refractive index measurement method based on Fizeau interferometry. Background Technology

[0002] Refractive index is a crucial physical parameter of a medium, determining the path and speed of light propagation within it. Currently, there are many methods for measuring refractive index, such as interpolation, the self-diffusivity equation method, the critical angle method for total internal reflection, and optical interferometry. Commonly used optical interferometry techniques include the Michelson interferometry and the Fizeau interferometry. The Michelson interferometry requires moving a mirror to scan the optical path difference, which takes time and necessitates placement within an active or passive vibration isolation system to maintain system stability. The presence of moving parts leads to mechanical aging, uneven speed, and reduced accuracy and lifespan over long-term use. In contrast, the Fizeau interferometry uses a static optical path, eliminating the problems caused by mechanical movement.

[0003] For the Fizeau interferometry method, wavelength changes are extremely sensitive to changes in refractive index. Changes in refractive index can induce significant fringe shifts, which are visually reflected in wavelength changes of 0.1 nm. This ability to amplify refractive index changes into visible fringe shifts lays the core foundation for achieving high-precision refractive index measurements.

[0004] The existing Fizeau interferometry method directly calculates the refractive index using the fringe spacing, and the relative accuracy of the refractive index measurement is approximately... There is still room for improvement in terms of signal-to-noise ratio and measurement accuracy.

[0005] Based on this, the present invention designs a gas-liquid refractive index measurement method based on Fizeau interferometry to solve the above problems. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the existing technology, the present invention provides a gas-liquid refractive index measurement method based on Fizeau interferometry.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for measuring the refractive index of gas and liquid based on Fizeau interferometry includes the following steps: Step 101: Evacuate and maintain the Fizeau interferometer cavity to a vacuum state, and obtain the interference fringes under this state as reference data; Step 102: Inject a fixed amount of the gas or liquid to be tested into the Fizeau interferometer cavity and obtain the interference fringe data in the sample state; Step 103: Based on the interferometer parameters calibrated in the vacuum state beforehand, and combined with the interference fringe data obtained in the vacuum state and the sample state, accurately calculate the corrected fringe spacing value of the Fizeau interferometer cavity in the vacuum state and the sample state.

[0008] Specifically, the following steps are included: (1) The two-dimensional interference fringe images obtained by incident the same monochromatic light on the vacuum state and the sample state are converted into a one-dimensional light intensity distribution curve by performing line integration along the vertical direction of the fringe. (2) By fitting the interference fringes in the vacuum state and the sample state using the nonlinear least squares method, the fringe spacing in the vacuum state can be extracted. With phase and the fringe spacing in the sample state With phase ; (3) The wedge angle of the interferometer is then precisely calibrated in a vacuum state beforehand. and initial stripe thickness The preliminarily extracted fringe spacing is corrected to obtain the corrected fringe spacing value; Step 104: Calculate the refractive index based on the corrected fringe spacing values ​​of the Fizeau interferometer cavity in the vacuum state and the sample state.

[0009] Furthermore, the specific steps of step 101 are as follows: First, the Fizeau interferometer cavity is evacuated to a vacuum and kept stable; then, a monochromatic laser source is activated, and its output light is emitted through the fiber optic coupler, then expanded and collimated by an off-axis parabolic mirror to form a uniform plane wave, which is then incident into the Fizeau interferometer cavity in a vacuum state; alternating bright and dark, high-contrast two-dimensional equal-thickness interference fringes are generated in the Fizeau interferometer cavity, and are acquired and received by the built-in high-resolution CCD camera.

[0010] Furthermore, in step 101, a wavelength is used. Monochromatic laser light source.

[0011] Furthermore, in step 102, while maintaining the same monochromatic light incident and a stable connection with the fiber optic coupler, the gas or liquid sample to be tested is injected into the Fizeau interferometer cavity; due to the different media, the optical path length in the Fizeau interferometer cavity changes, causing an observable shift in the spacing and phase of the two-dimensional interference fringes; the changed interference pattern is acquired by the same built-in CCD camera, thereby obtaining two-dimensional interference fringe data of the optical information of the medium to be tested.

[0012] Furthermore, in step 103, the one-dimensional light intensity distribution curve is modeled by a composite function containing a Gaussian envelope and sinusoidal modulation: in, Indicates the amplitude coefficient. Indicates the independent variable. Indicates the center position of the Gaussian envelope. This represents the width of the Gaussian envelope. Indicates the stripe period. Indicates the initial phase. This indicates the offset.

[0013] Furthermore, in step 103, the corrected fringe spacing value under vacuum is... : Among them, interference level for: .

[0014] Furthermore, in step 103, the corrected fringe spacing value under the injected gas or liquid sample state is... : Among them, interference level for: .

[0015] Furthermore, in step 104, the refractive index formula is: = .

[0016] Furthermore, a gas-liquid refractive index measurement device based on Fizeau interferometry is adopted, which includes an optical fiber coupler (1), an off-axis parabolic mirror (2), a Fizeau interferometer cavity (3), and a CCD camera (4).

[0017] Compared with the prior art, the beneficial effects of this invention are as follows: This method improves the signal-to-noise ratio by combining row integration, fringe spacing correction and interferometer parameter calibration, and is applicable to fields such as gas-liquid purity analysis and impurity content detection, providing a reliable means of refractive index measurement for industrial quality inspection and scientific research. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0019] Figure 1 This is a schematic diagram of the apparatus used in this invention; Figure 2 This is a flowchart of a gas-liquid refractive index measurement method based on Fizeau interferometry according to the present invention; Figure 3This is a schematic diagram of simulated noise fringes for a gas-liquid refractive index measurement method based on Fizeau interferometry according to the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] Example 1: Please refer to the accompanying drawings in the instruction manual. Figure 1 A gas-liquid refractive index measurement device based on Fizeau interferometry includes an optical fiber coupler 1, an off-axis parabolic mirror 2, a Fizeau interferometer cavity 3, and a CCD camera 4. Please refer to the accompanying drawings in the instruction manual. Figure 2 The gas-liquid refractive index measurement method based on Fizeau interferometry includes the following steps: Step 101: Evacuate and maintain the inside of the Fizeau interferometer cavity 3 to a vacuum state, and obtain the interference fringes under this state as reference data; Specifically, first, the Fizeau interferometer cavity 3 is evacuated to a vacuum and kept stable; then, the wavelength is activated. The monochromatic laser source outputs light through an optical fiber coupler 1, which is then expanded and collimated by a high-precision off-axis parabolic mirror 2 to form a uniform plane wave. The light is then incident into a Fizeau interferometer cavity 3 in a vacuum state. Two-dimensional equal-thickness interference fringes with alternating bright and dark patterns and high contrast are generated in the Fizeau interferometer cavity 3 and are acquired and received by a built-in high-resolution CCD camera 4, which can ensure that the original data has a high signal-to-noise ratio.

[0022] Step 102: Inject a quantitative amount of the gas or liquid to be tested into the Fizeau interferometer cavity 3 to obtain interference fringe data in the sample state (sample state); Specifically, under the premise of maintaining the same monochromatic light incident and a stable connection with the fiber optic coupler 1, the gas or liquid sample to be tested is injected into the Fizeau interferometer cavity 3. Due to the different media, the optical path length within the Fizeau interferometer cavity 3 changes, causing an observable shift in the spacing and phase of the two-dimensional interference fringes. This changed interference pattern is acquired under the same conditions, such as by the same built-in CCD camera, thereby obtaining two-dimensional interference fringe data of the optical information of the medium under test.

[0023] Step 103: Based on the interferometer parameters calibrated in the vacuum state beforehand, and combined with the interference fringe data obtained in the vacuum state and the sample state, accurately calculate the corrected fringe spacing value of the Fizeau interferometer cavity 3 in both states.

[0024] Specifically, the following steps are included: (1) Two-dimensional interference fringe images obtained by incident the same monochromatic light onto the vacuum state and the sample state are transformed into a one-dimensional light intensity distribution curve by performing line integration along the direction perpendicular to the fringes. The one-dimensional light intensity distribution curve can be modeled by a composite function containing a Gaussian envelope and sinusoidal modulation: in, Indicates the amplitude coefficient. Indicates the independent variable. Indicates the center position of the Gaussian envelope. This represents the width of the Gaussian envelope. Indicates the stripe period. Indicates the initial phase. Indicates the offset; (2) By fitting the interference fringes under different acquisition conditions using the nonlinear least squares method, the fringe spacing in the vacuum state can be extracted. With phase and the fringe spacing in the sample state With phase .

[0025] (3) The wedge angle of the interferometer is then precisely calibrated in a vacuum state beforehand. and initial stripe thickness The initially extracted fringe spacing was corrected to obtain a more accurate fringe spacing value.

[0026] The corrected fringe spacing value under vacuum is : Among them, interference level for: The corrected fringe spacing value under injected gas or liquid sample conditions is : Among them, interference level for: .

[0027] Step 104: Based on the Fizeau interference principle, calculate the high-precision refractive index using the fringe spacing values ​​of the Fizeau interference cavity 3 under different states after correction.

[0028] According to the Fizeau interference principle, the refractive index... The ratio of the fringe spacing under different conditions is: The refractive index calculated by this method is: = .

[0029] Please refer to Table 1 for the results of calculating the difference between the refractive index and the ideal refractive index for different media and the results of relative accuracy.

[0030] Table 1 This method improves the accuracy of refractive index measurement by combining line integration to enhance the signal-to-noise ratio, fringe spacing correction, and interferometer parameter calibration. It is applicable to fields such as gas-liquid purity analysis and impurity content detection, providing a reliable means of refractive index measurement for industrial quality inspection and scientific research.

[0031] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring the refractive index of gas and liquid based on Fizeau interferometry, characterized in that, Includes the following steps: Step 101: Evacuate and maintain the Fizeau interferometer cavity to a vacuum state, and obtain the interference fringes under this state as reference data; Step 102: Inject a fixed amount of the gas or liquid to be tested into the Fizeau interferometer cavity and obtain the interference fringe data in the sample state; Step 103: Based on the interferometer parameters calibrated in the vacuum state beforehand, and combined with the interference fringe data obtained in the vacuum state and the sample state, accurately calculate the corrected fringe spacing values ​​of the Fizeau interferometer cavity in the vacuum state and the sample state; Specifically, the following steps are included: (1) The two-dimensional interference fringe images obtained by incident the same monochromatic light on the vacuum state and the sample state are converted into a one-dimensional light intensity distribution curve by performing line integration along the vertical direction of the fringe. (2) By fitting the interference fringes in the vacuum state and the sample state using the nonlinear least squares method, the fringe spacing in the vacuum state can be extracted. With phase and the fringe spacing in the sample state With phase ; (3) The wedge angle of the interferometer is then precisely calibrated in a vacuum state beforehand. and initial stripe thickness The preliminarily extracted fringe spacing is corrected to obtain the corrected fringe spacing value; Step 104: Calculate the refractive index based on the corrected fringe spacing values ​​of the Fizeau interferometer cavity in the vacuum state and the sample state.

2. The gas-liquid refractive index measurement method based on Fizeau interferometry according to claim 1, characterized in that, The specific steps of step 101 are as follows: First, the Fizeau interferometer cavity is evacuated to a vacuum and kept stable; then, the monochromatic laser source is turned on, and its output light is emitted through the fiber optic coupler, and then expanded and collimated by the off-axis parabolic mirror to form a uniform plane wave, which is then incident into the Fizeau interferometer cavity in a vacuum state; alternating bright and dark, high-contrast two-dimensional equal-thickness interference fringes are generated in the Fizeau interferometer cavity, and are collected and received by the built-in high-resolution CCD camera.

3. The gas-liquid refractive index measurement method based on Fizeau interferometry according to claim 2, characterized in that, In step 101, wavelength is used. Monochromatic laser light source.

4. The gas-liquid refractive index measurement method based on Fizeau interferometry according to claim 1, characterized in that, In step 102, under the premise of maintaining the same monochromatic light incident and stable connection with the fiber optic coupler, the gas or liquid sample to be tested is injected into the Fizeau interferometer cavity; due to the different media, the optical path in the Fizeau interferometer cavity changes, causing observable shifts in the spacing and phase of the two-dimensional interference fringes; the changed interference pattern is acquired by the same built-in CCD camera, thereby obtaining two-dimensional interference fringe data of the optical information of the medium to be tested.

5. The gas-liquid refractive index measurement method based on Fizeau interferometry according to claim 4, characterized in that, In step 103, the one-dimensional light intensity distribution curve is modeled by a composite function containing a Gaussian envelope and sinusoidal modulation: in, Indicates the amplitude coefficient. Indicates the independent variable. Indicates the center position of the Gaussian envelope. This represents the width of the Gaussian envelope. Indicates the stripe period. Indicates the initial phase. This indicates the offset.

6. The gas-liquid refractive index measurement method based on Fizeau interferometry according to claim 5, characterized in that, In step 103, the corrected fringe spacing value under vacuum is... : Among them, interference level for: 。 7. The gas-liquid refractive index measurement method based on Fizeau interferometry according to claim 6, characterized in that, In step 103, the corrected fringe spacing value under the injected gas or liquid sample state is... : Among them, interference level for: 。 8. The gas-liquid refractive index measurement method based on Fizeau interferometry according to claim 7, characterized in that, In step 104, the refractive index formula is: = 。 9. The gas-liquid refractive index measurement method based on Fizeau interferometry according to claim 1, characterized in that, A gas-liquid refractive index measurement device based on Fizeau interferometry is adopted, which includes an optical fiber coupler (1), an off-axis parabolic mirror (2), a Fizeau interferometer cavity (3), and a CCD camera (4).

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