A real-time measurement method for alcohol concentration based on fringe period measurement

Abstract

The application provides an alcohol concentration real-time measurement method based on fringe period measurement, a laser emits a laser beam, a first half-wave plate adjusts components of s-polarized light and p-polarized light of the laser beam, and a polarization beam splitter prism divides the laser beam into two beams of s-polarized light and p-polarized light; the p-polarized light is transmitted by the polarization beam splitter prism and enters a second half-wave plate, the second half-wave plate converts the p-polarized light into s-polarized light and then the s-polarized light is incident into a sample flow cell; the s-polarized light is refracted by the polarization beam splitter prism and then enters a prism, and after three times of total reflection of the prism, the s-polarized light irradiates the sample flow cell; the sample flow cell contains a solution to be measured, two beams of s-polarized light intersect in the solution to form interference fringes, and the interference fringes are recorded by an image sensor; and the refractive index and concentration change of the solution are inversed by measuring the interference fringe period.

Description

Technical Field

[0001] This application relates to the field of optical detection technology, and in particular to a method for real-time measurement of alcohol concentration based on stripe period measurement. Background Technology

[0002] Current solutions concentration measurement technologies have significant limitations. The conductivity method is only applicable to ionic solutions, limiting its application range; traditional refractometers rely on complex optical paths and high-precision displacement detection systems, resulting in high equipment costs and difficult maintenance; while spectroscopic analysis methods offer high accuracy, they have stringent requirements for spectroscopic equipment, making them unsuitable for the real-time, non-contact, online monitoring needs of industrial sites, especially dynamic production environments (such as pharmaceutical reactors and food fermentation tanks).

[0003] Therefore, there is an urgent need for a concentration detection method that is simple in structure, low in cost, applicable to a variety of solutions, and capable of non-contact online monitoring. Summary of the Invention

[0004] In view of the above practical problems and the shortcomings of existing technologies, the main technical problem to be solved by the present invention is to provide a real-time alcohol concentration measurement method based on fringe period measurement. The solution concentration is inverted by analyzing the periodic changes of interference fringes. It has the advantages of compact structure, fast response and strong anti-interference ability, which significantly improves the accuracy and adaptability of concentration detection, and is especially suitable for online monitoring needs in complex industrial environments.

[0005] To address the aforementioned technical problems, this application provides a real-time alcohol concentration measurement method based on stripe period measurement, employing the following technical solution:

[0006] A real-time alcohol concentration measurement method based on stripe period measurement, the measurement method comprising the following steps:

[0007] Step A: A laser beam is emitted by the laser. The laser beam passes through the first half-wave plate and the polarizing beam splitter in sequence. After the first half-wave plate adjusts the s-polarized and p-polarized components of the laser beam, the polarizing beam splitter splits the laser beam into two beams, s-polarized and p-polarized.

[0008] In the two beams, the p-polarized light is transmitted through the polarizing beam splitter prism and enters the second half-wave plate. The second half-wave plate converts the p-polarized light into s-polarized light and then it enters the sample flow cell. This is denoted as optical path R. In the two beams, the s-polarized light is refracted by the polarizing beam splitter prism and enters the prism. After three total internal reflections by the prism, it illuminates the sample flow cell. This is denoted as optical path O.

[0009] The sample flow cell contains the solution to be tested. Two beams of s-polarized light intersect in the solution to form interference fringes, which are then recorded by an image sensor.

[0010] Step B: By measuring the periodicity of the interference fringes, the refractive index and concentration changes of the solution are inverted. The calculation steps are as follows:

[0011] Let the wave vectors of the light paths R and O be... and The optical path R and optical path O are parallel to the optical axis along the propagation direction. The included angles of the axes are respectively and The angle between optical path R and optical path O is Adjust the light path to make ;

[0012] The formula for the complex amplitude of the optical path R is: The formula for the complex amplitude of optical path O is: ;

[0013] in the formula Angular frequency, For time, For light path The amplitude, For light path The amplitude, let ; Let the wave vector of the beam in the solution be denoted as . , The wavelength of the laser in the solution. , It is the wavelength of laser light in a vacuum. It is the refractive index of the solution;

[0014] The formula for the complex amplitude of interference light is: ;

[0015] With the bottom of the sample flow cell set as Axis, and optical axis Establish a coordinate system based on axes, and let the intensity of the interference light vary with spatial position. And what is changing is... If an observation screen is placed at a certain point, the formula for the intensity distribution of the interference light on the screen is: ;

[0016] set up The formula for the light intensity distribution on the screen is: ;

[0017] Based on the stripe period on the image sensor achievable .

[0018] In a preferred embodiment, a measuring device for performing the measurement method is included, the measuring device comprising a laser, a first half-wave plate, a polarizing beam splitter prism, a second half-wave plate, a prism, a sample flow cell, and an image sensor.

[0019] The laser is used to emit a laser beam. The first half-wave plate is used to adjust the s-polarized and p-polarized components of the laser by 50%. The polarizing beam splitter is used to split the laser beam into two beams, s-polarized and p-polarized. The second half-wave plate is used to convert the p-polarized light into s-polarized light. The sample flow cell contains the solution to be tested.

[0020] In a preferred embodiment, the laser, the first half-wave plate, the polarizing beam splitter prism, the second half-wave plate, the sample flow cell, and the image sensor are arranged sequentially along the laser emission direction; the prism is arranged along the direction in which the laser is refracted by the polarizing beam splitter prism, and the prism is located above the sample flow cell.

[0021] In a preferred embodiment, the measuring device further includes a laser driver circuit board for driving the laser.

[0022] In a preferred embodiment, the image sensor is used to record interference fringes in the solution; the pixel period of the image sensor is less than 1 μm.

[0023] In summary, this application has the following beneficial effects:

[0024] 1. It adopts laser interference fringe period measurement, which does not require direct contact with the solution to be tested, thus avoiding the risk of contamination. It is suitable for real-time concentration monitoring in dynamic production scenarios such as pharmaceutical reaction vessels and food fermentation tanks.

[0025] 2. By adopting a dual-optical-path symmetrical design (optical path R and optical path O share the same path for transmission), the influence of environmental factors such as vibration and temperature drift on interference fringes is effectively offset, thereby improving the stability of industrial field measurements.

[0026] 3. By directly correlating the periodic variation of interference fringes formed by s-polarized light in a solution with the refractive index, and through an accurate model of fringe period-refractive index-concentration, high-sensitivity detection of alcohol concentration can be achieved.

[0027] 4. By abandoning the precision displacement device of traditional refractometers or the complex spectral dispersive system of spectrometers, the interference optical path can be constructed using only a half-wave plate, a polarizing beam splitter prism, and total internal reflection of the prism, reducing the cost of core components by more than 60%. Attached Figure Description

[0028] Figure 1 This is a structural diagram of the alcohol concentration measuring device in a preferred embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of light waves intersecting in a solution in a preferred embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the light wave vector and fringe spacing in a preferred embodiment of the present invention;

[0031] Figure 4 This is a graph showing the relationship between alcohol concentration and refractive index in a preferred embodiment of the present invention;

[0032] Figure 5 This is a graph showing the relationship between the solution refractive index and the stripe spacing on the image sensor in a preferred embodiment of the present invention.

[0033] Figure 6 This is a graph showing the relationship between alcohol concentration and stripe spacing on the image sensor in a preferred embodiment of the present invention.

[0034] Explanation of reference numerals in the attached figures: 1. Laser driver circuit board; 2. Laser; 3. First half-wave plate; 4. Polarizing beam splitter prism; 5. Second half-wave plate; 6. Prism; 7. Sample flow cell; 8. Sample to be tested; 9. Image sensor. Detailed Implementation

[0035] 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 embodiments of the present invention, and not all embodiments. 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.

[0036] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed", "equipped", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0038] The following is in conjunction with the appendix Figures 1-6 This application will be described in further detail.

[0039] This embodiment provides a real-time alcohol concentration measurement method based on stripe period measurement. This method is used for non-contact rapid measurement of liquid concentration, and is especially suitable for the concentration detection of transparent to semi-transparent liquids such as alcohol and sugar solutions.

[0040] This embodiment also provides a solution concentration measuring device for this measurement method, such as... Figure 1 The measuring device includes a laser 2, a first half-wave plate 3, a polarizing beam splitter prism 4, a second half-wave plate 5, a prism 6, a sample flow cell 7, and an image sensor 9. The laser 2, first half-wave plate 3, polarizing beam splitter prism 4, second half-wave plate 5, sample flow cell 7, and image sensor 9 are arranged sequentially along the laser emission direction. The prism 6 is positioned above the sample flow cell 7, along the direction in which the laser is refracted by the polarizing beam splitter prism 4. The measuring device also includes a laser driver circuit board 1 for driving the laser 2.

[0041] The laser 2 is used to emit a laser beam, the first half-wave plate 3 is used to adjust the s-polarized and p-polarized components of the laser by 50%, the polarizing beam splitter 4 is used to split the laser beam into two beams, s-polarized and p-polarized; the second half-wave plate 5 is used to convert the p-polarized light to s-polarized, so that both beams in the solution are s-polarized and can produce interference fringes.

[0042] The sample flow cell 7 contains the solution to be tested. The polarizing beam splitter prism 4 can reflect S-polarized laser light and transmit P-polarized laser light, thereby splitting one beam of light into two beams.

[0043] The prism 6 is used to adjust the direction of the laser beam so that the s-polarized laser enters the sample flow cell 7, causing the two s-polarized beams in the solution to produce interference fringes.

[0044] The image sensor 9 is used to record interference fringes in the solution and convert the light signal into photoelectric signals, so that the subsequent processing system can analyze the fringe period to calculate the refractive index and concentration of the solution. The pixel period of the image sensor 9 is less than 1 μm, and the fringe period that can be measured can be as small as 2 μm, thereby improving the measurement sensitivity and lowering the detection limit.

[0045] The measurement method provided in this embodiment includes the following steps:

[0046] Step A: A laser beam is emitted by the laser. The laser beam passes through the first half-wave plate and the polarizing beam splitter in sequence. After the first half-wave plate adjusts the s-polarized and p-polarized components of the laser beam, the polarizing beam splitter splits the laser beam into two beams, s-polarized and p-polarized.

[0047] In the two beams, the p-polarized light is transmitted through the polarizing beam splitter prism and enters the second half-wave plate. The second half-wave plate converts the p-polarized light into s-polarized light and then it enters the sample flow cell. This is denoted as optical path R. In the two beams, the s-polarized light is refracted by the polarizing beam splitter prism and enters the prism. After three total internal reflections by the prism, it illuminates the sample flow cell. This is denoted as optical path O.

[0048] The sample flow cell contains the solution to be tested. Two beams of s-polarized light intersect in the solution to form interference fringes, which are then recorded by an image sensor.

[0049] Step B, based on the relationship between the interference fringe period and the solution refractive index (e.g.) Figure 5 And it is related to the solution refractive index and solution concentration (e.g.) Figure 4 The changes in the refractive index and concentration of the solution can be inverted by measuring the period of the interference fringes. The calculation steps are as follows:

[0050] like Figures 2-3 Let the wave vectors of the light paths R and O be... and The optical path R and optical path O are parallel to the optical axis along the propagation direction. The included angles of the axes are respectively and The angle between optical path R and optical path O is Adjust the light path to make ;like Figure 1 As shown, the laser 2, the first half-wave plate 3, the polarizing beam splitter prism 4, and the second half-wave plate 5 are coaxially mounted and set as the light propagation path of the optical path R. The light propagation path is perpendicular to the normal direction of the sample flow cell 7 (i.e., the optical axis). The included angle (in the axial direction) is set as ;like Figure 1 The prism 6 is installed at a suitable position so that the light rays illuminating the sample flow cell after three total internal reflections by the prism 6 align with the normal direction (i.e., the optical axis) of the sample flow cell 7. The angle between the axes (direction) is Based on the characteristics of different angles on each facet of prism 6, the included angle is adjusted by rotating prism 6. This can make .

[0051] The formula for the complex amplitude of the optical path R is: The formula for the complex amplitude of optical path O is: ;

[0052] in the formula Angular frequency, For time, For light path The amplitude, For light path The amplitude, let ; Let the wave vector of the beam in the solution be denoted as . , The wavelength of the laser in the solution. , It is the wavelength of laser light in a vacuum. It is the refractive index of the solution;

[0053] The formula for the complex amplitude of interference light is:

[0054] ;

[0055] The formula for light intensity distribution is:

[0056] ;

[0057] With the bottom of the sample flow cell set as Axis, and optical axis Establish a coordinate system based on axes (e.g.) Figure 3 Interference light intensity varies with spatial position And what is changing is... If an observation screen is placed at a certain point, the formula for the intensity distribution of the interference light on the screen is: ;

[0058] set up The formula for the light intensity distribution on the screen is: ;

[0059] Based on the stripe period on the image sensor ,application , , It is the wavelength of laser light in a vacuum. It is the wavelength of the laser in the solution, and the refractive index of the solution. The stripe period on the image sensor can be calculated. Thus, we can conclude that... Therefore, based on the stripe period on the image sensor, Inversion yields the solution refractive index .

[0060] Refractive index of solution By calibrating with the solution concentration and combining the above relationships, the solution concentration and stripe period can be analyzed and obtained. Relationships, such as Figure 6 .

[0061] The above description is merely a preferred embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention by those skilled in the art within the scope of the technology disclosed in the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A method for real-time measurement of alcohol concentration based on stripe period measurement, characterized in that: The measurement method includes the following steps: Step A: A laser beam is emitted by the laser. The laser beam passes through the first half-wave plate and the polarizing beam splitter in sequence. After the first half-wave plate adjusts the s-polarized and p-polarized components of the laser beam, the polarizing beam splitter splits the laser beam into two beams, s-polarized and p-polarized. In the two beams, the p-polarized light is transmitted through the polarizing beam splitter prism and enters the second half-wave plate. The second half-wave plate converts the p-polarized light into s-polarized light and then it enters the sample flow cell. This is denoted as optical path R. In the two beams, the s-polarized light is refracted by the polarizing beam splitter prism and enters the prism. After three total internal reflections by the prism, it illuminates the sample flow cell. This is denoted as optical path O. The sample flow cell contains the solution to be tested. Two beams of s-polarized light intersect in the solution to form interference fringes, which are then recorded by an image sensor. Step B: By measuring the periodicity of the interference fringes, the refractive index and concentration changes of the solution are inverted. The calculation steps are as follows: Let the wave vectors of the light paths R and O be... and The optical path R and optical path O are parallel to the optical axis along the propagation direction. The included angles of the axes are respectively and The angle between optical path R and optical path O is Adjust the light path to make ; The formula for the complex amplitude of the optical path R is: The formula for the complex amplitude of optical path O is: ; in the formula Angular frequency, For time, For light path The amplitude, For light path The amplitude, let ; Let the wave vector of the beam in the solution be denoted as . , The wavelength of the laser in the solution. , It is the wavelength of laser light in a vacuum. It is the refractive index of the solution; The formula for the complex amplitude of interference light is: ; With the bottom of the sample flow cell set as Axis, and optical axis Establish a coordinate system based on axes, and let the intensity of the interference light vary with spatial position. And what is changing is... If an observation screen is placed at a certain point, the formula for the intensity distribution of the interference light on the screen is: ; set up The formula for the light intensity distribution on the screen is: ; Based on the stripe period on the image sensor achievable .

2. The method for real-time measurement of alcohol concentration based on stripe period measurement according to claim 1, characterized in that: The device includes a measuring apparatus for performing the measurement method, the measuring apparatus comprising a laser, a first half-wave plate, a polarizing beam splitter prism, a second half-wave plate, a prism, a sample flow cell, and an image sensor; The laser is used to emit a laser beam. The first half-wave plate is used to adjust the s-polarized and p-polarized components of the laser by 50%. The polarizing beam splitter is used to split the laser beam into two beams, s-polarized and p-polarized. The second half-wave plate is used to convert the p-polarized light into s-polarized light. The sample flow cell contains the solution to be tested.

3. The method for real-time measurement of alcohol concentration based on stripe period measurement according to claim 2, characterized in that: The laser, first half-wave plate, polarizing beam splitter prism, second half-wave plate, sample flow cell, and image sensor are arranged sequentially along the laser emission direction; the prism is arranged along the direction in which the laser is refracted by the polarizing beam splitter prism, and the prism is located above the sample flow cell.

4. The method for real-time measurement of alcohol concentration based on stripe period measurement according to claim 2, characterized in that: The measuring device also includes a laser driver circuit board for driving the laser.

5. The method for real-time measurement of alcohol concentration based on stripe period measurement according to claim 2, characterized in that: The image sensor is used to record interference fringes in the solution; the pixel period of the image sensor is less than 1 μm.

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