Fluorescent optical fiber probe device for three-phase flow detection

Abstract

The invention relates to the technical field of three-phase flow detection, and provides a fluorescent optical fiber probe device for three-phase flow detection. The sapphire probe is arranged in the packaging shell; the small-diameter self-focusing lens and the large-diameter self-focusing lens are connected and are positioned above the sapphire probe; the integrated optical fiber bundle structure is divided into a transmitting optical fiber and a receiving optical fiber in the main cavity; the laser transmitting module is connected with the transmitting optical fiber; the collimating lens is arranged above the receiving optical fiber; the trapezoidal waveguide structure is arranged above the collimating lens; the first optical focusing assembly and the second optical focusing assembly are arranged above the trapezoidal waveguide structure side by side, and a reflection type volume holographic grating is arranged below the first optical focusing assembly; a first photoelectric conversion module and a second photoelectric conversion module; and a main control module. The device provided by the invention can effectively avoid optical power attenuation caused by optical fiber light splitting and a filter plate, and is beneficial to guarantee of optical signal transmission efficiency and detection precision.

Description

Technical Field

[0001] The present invention relates to the technical field of three-phase flow detection, and more specifically, to a fluorescence optical fiber probe device for three-phase flow detection. Background Art

[0002] Three-phase flow monitoring is a key link in the research of industrial multiphase flow. The optical fiber probe technology realizes phase identification through the refractive index difference. When the sensitive head contacts the fluid, the refractive indices of different media modulate the optical signal, which is transmitted through the optical fiber to the photoelectric converter to form a characteristic voltage signal - the gas phase presents a high level, and the liquid phase (oil / water) shows a low level. Although the technology for distinguishing gas-liquid two-phase has become mature, the distinction between oil and water in the liquid phase still faces technical challenges.

[0003] Among the related technologies for distinguishing oil-gas-water three-phase, the optical fiber sensing device based on composite film enhanced reflection deposits chromium / silver / chromium / silica multi-layer films on the surface of the tapered optical fiber in sequence to optimize the reflection characteristics of the optical signal, and combines the threshold comparison method of the infrared light source to enhance the recognition of the light intensity difference between the oil phase and the water phase. However, the existing technology still has the following technical defects: (1) The physical mismatch between the outer diameter of the optical fiber or optical fiber bundle and the sapphire probe causes significant backlight loss, restricting the signal transmission efficiency and limiting the detection accuracy.

[0004] (2) Relying on multi-fiber beam splitting and combining filter slices to separate the reflected light and fluorescence signals results in a significant attenuation of the double-band optical power due to the multiple filtering process. Especially in the weak light detection scenario, the signal-to-noise ratio deteriorates severely, restricting the optical signal transmission efficiency and detection accuracy of the probe. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art or related technologies.

[0006] To this end, the object of the present invention is to provide a fluorescence optical fiber probe device for three-phase flow detection. By constructing a coaxial graded refractive index optical path coupling system and combining the regulation of the axial pitch parameter, the efficient transmission of the emitted laser and the precise focusing and collection of the reverse fluorescence signal are realized. The reflective volume holographic grating is innovatively introduced, and its wavelength selectivity is utilized to diffract the reflected light directionally, and the reflected light is deflected to the focusing channel through the reflecting surface, while the fluorescence signal enters the independent detection path through the zero-order transmission, effectively avoiding the optical power attenuation caused by optical fiber beam splitting and filter slices, which is beneficial to ensuring the optical signal transmission efficiency and detection accuracy.

[0007] To achieve the above object, the technical solution of the present invention provides a fluorescence optical fiber probe device for three-phase flow detection, comprising: an encapsulation housing; a sapphire probe, disposed within the encapsulation housing and extending out of the encapsulation housing; a large-diameter self-focusing lens, disposed within the encapsulation housing and above the sapphire probe; a small-diameter self-focusing lens, disposed within the encapsulation housing and above the large-diameter self-focusing lens; an integrated optical fiber bundle structure, disposed within the encapsulation housing, with one end connected above the small-diameter self-focusing lens, and the other end of the integrated optical fiber bundle structure extending into the main cavity of the encapsulation housing, and being divided into a transmitting optical fiber and a receiving optical fiber within the main cavity; a laser emission module, connected to the transmitting optical fiber; a collimating lens, disposed above the receiving optical fiber; a trapezoidal waveguide structure, disposed above the collimating lens; a first optical focusing component and a second optical focusing component, arranged side by side above the trapezoidal waveguide structure, wherein a reflective volume holographic grating is disposed below the first optical focusing component, corresponding above the collimating lens; the first optical focusing component is connected to a first photoelectric conversion module, and the second photoelectric conversion module is connected above the second optical focusing component; a main control module, respectively connected to the laser emission module, the first photoelectric conversion module, and the second photoelectric conversion module.

[0008] Preferably, the sapphire probe extends out of the narrower end of the encapsulation housing.

[0009] Preferably, the design parameters of the reflective volume holographic grating are determined by a reflective volume holographic grating diffraction efficiency model established based on the Kogelnik coupled-wave theory, and the reflective volume holographic grating diffraction efficiency model includes:

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017] , wherein, is characterized as the angle formed by the incident light with the normal direction z of the recording plane in the holographic medium, Characterized as a grating vector The angle formed with the normal direction z of the recording plane, n0 is characterized as the average refractive index, Characterized as the wavelength of the incident light in vacuum, Characterized as the interference fringe spacing, Characterized as the angle formed by the fringe plane with the object light or the reference light in the holographic medium, Characterized as the wavelength of the recording light in vacuum, Characterized as the wavelength of the recording light in the holographic medium, Characterized as the coupling coefficient of the grating, n1 is characterized as the refractive index modulation degree, Characterized as the incident light wave vector in the medium, Characterized as the wave number in vacuum, Characterized as the average absorption coefficient of the medium, Characterized as the modulation amplitude of the absorption constant, Characterized as the phase mismatch parameter, Characterized as the grating vector generated during interference recording, Characterized as the magnitude of the grating vector generated during interference recording, Characterized as the unit vector of the normal direction z of the recording material, Characterized as the tilt factor of the diffracted light, Characterized as the tilt factor of the incident light, Characterized as the propagation constant root of the solution of the wave coupling differential equation, d is characterized as the physical thickness of the volume grating, S(0) is characterized as the amplitude of the diffracted light, Characterized as the diffraction efficiency, j is the imaginary unit.

[0018] Preferably, for the dual-wavelength scenario of 470nm reflected light and 515nm fluorescence, the refractive index modulation degree of the reflection-type volume holographic grating is 0.115 and the thickness is 50μm.

[0019] Preferably, a reflective film or a mirror is provided on the inclined surface of the trapezoidal waveguide structure, and the inclination angle of the inclined surface with the horizontal straight line is determined according to the diffraction angle of the reflection-type volume holographic grating.

[0020] Preferably, the inclination angle of the inclined surface of the trapezoidal waveguide structure is , where θ1 is the diffraction angle of the reflection-type volume holographic grating.

[0021] Preferably, the distance between the collimating lens and the receiving optical fiber does not exceed 3mm; the distances between the first optical focusing component and the first photoelectric conversion module, and between the second optical focusing component and the second photoelectric conversion module are both less than 15mm.

[0022] In addition, the length of the collimating lens connected to the trapezoidal waveguide structure is 4.8 mm, the length of the reflective volume holographic grating connected to the trapezoidal waveguide structure is 6 mm, and the length of the first optical focusing component connected to the trapezoidal waveguide structure is 6 mm. The linear distance between the collimating lens and the reflective volume holographic grating is 10 mm.

[0023] Preferably, the first optical focusing component is a focusing lens configured with an AR antireflection coating in the range of 400 - 700 nm, and its thickness is 3 mm; The second optical focusing component is a focusing lens configured with an AR antireflection coating in the range of 400 - 700 nm, and its thickness is 3 mm; The collimating lens is a high - refractive - index lens with both sides coated with an AR antireflection coating in the range of 400 - 700 nm, and its thickness is 2 mm. The divergence angle for the reflected light at 470 nm does not exceed 3°, and the divergence angle for the fluorescence at 515 nm does not exceed 2.5°.

[0024] Preferably, the diameter of the large - diameter self - focusing lens is 1 mm, and the pitch is 0.25P - 0.75P; The diameter of the small - diameter self - focusing lens is 0.5 mm, and the pitch is 0.25P.

[0025] Preferably, the integrated optical fiber bundle structure is formed by coupling three optical fibers or seven optical fibers into a bundle. The transmitting optical fiber is a single - mode or multi - mode optical fiber with a numerical aperture of 0.13 - 0.22, and the receiving optical fiber is a multi - mode optical fiber with a numerical aperture of 0.275; Both the first optoelectronic conversion module and the second optoelectronic conversion module include a PIN photodiode and an I / V conversion circuit board connected together. The distance between the PIN photodiode and the first optical focusing component or the second optical focusing component is 7 mm; The laser emission module includes a laser emission control circuit board and a fiber laser emitter connected together.

[0026] Preferably, the three - phase flow detection fluorescent optical fiber probe device further includes: a tapered ferrule press - sealing structure sleeved on the packaging housing and corresponding to the position of the integrated optical fiber bundle structure for high - pressure sealing.

[0027] A three - phase flow detection fluorescent optical fiber probe device proposed by the present invention has the following beneficial technical effects: (1) The three - phase flow detection fluorescent optical fiber probe device proposed by the present invention significantly improves the signal transmission efficiency and detection accuracy.

[0028] (2) A fluorescence optical fiber probe device for three-phase flow detection proposed by the present invention constructs a double self-focusing lens coupling system with a compact axial dimension. Based on the self-focusing lens characteristics of gradient refractive index materials, the pitch of the fixed small-diameter self-focusing lens is optimized to be 0.25P, and at the same time, the pitch of the large-diameter self-focusing lens is adjusted to be 0.25P - 0.75P, preferably 0.25P, to achieve axial matching of the optical field, significantly improving the coupling efficiency, greatly increasing the fluorescence reception power and the reflected light reception power, effectively solving the problem that it is difficult to match the fiber bundle with the sapphire probe, and providing theoretical support for miniaturized probe packaging.

[0029] (3) A fluorescence optical fiber probe device for three-phase flow detection proposed by the present invention innovatively introduces a reflection-type volume holographic grating. Utilizing its wavelength selectivity, the reflected light is directionally diffracted, and through the reflecting surface, it is deflected to the focusing channel, while the fluorescence signal enters the independent detection path through zero-order transmission, effectively avoiding the optical power attenuation caused by fiber beam splitting and filter slices, which is beneficial to ensuring the optical signal transmission efficiency and detection accuracy.

[0030] (4) A fluorescence optical fiber probe device for three-phase flow detection proposed by the present invention is for the dual-wavelength scenario of 470nm reflected light and 515nm fluorescence. The refractive index modulation degree of the reflection-type volume holographic grating is 0.115 and the thickness is 50μm. This reflection-type volume holographic grating has a diffraction efficiency of up to 1 when the incident wavelength is 470nm, and only 0.0162 at the 515nm wavelength. The reflection-type volume holographic grating can effectively achieve the spectral separation of the two wavelengths of 470nm and 515nm.

[0031] (5) A fluorescence optical fiber probe device for three-phase flow detection proposed by the present invention can effectively solve the problem of significant optical power attenuation caused by traditional filter slices and independent fiber beam splitting, and at the same time achieve efficient splitting of the reflected light and fluorescence. While maintaining a high optical power transmission efficiency, it ensures the independence of the reflected light and fluorescence detection.

[0032] (6) The design of a fluorescence optical fiber probe device for three-phase flow detection proposed by the present invention significantly improves the signal-to-noise ratio and detection sensitivity of the dual-band signals through optical path integration and wavelength-selective spatial separation. At the same time, a corresponding probe packaging structure is adopted to enhance the system reliability.

[0033] The additional aspects and advantages of the present invention will be given in the following description part, some of which will become obvious from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0034] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where: Figure 1Shows a structural view of a fluorescence optical fiber probe device for three-phase flow detection according to an embodiment of the present invention; Figure 2 Shows Figure 1 A partially enlarged schematic view of the structure of the fluorescence optical fiber probe device for three-phase flow detection in Figure 3 Shows Figure 1 A schematic view of the structure of the double self-focusing lens probe part of the fluorescence optical fiber probe device for three-phase flow detection in Figure 4 Shows Figure 1 A schematic view of the structure of the connection position between the integrated optical fiber bundle structure and the small-diameter self-focusing lens of the fluorescence optical fiber probe device for three-phase flow detection in Figure 5 Shows a simulation schematic diagram of the reflection of reflected light (blue) and fluorescence (green) by a reflection-type volume holographic grating; Figure 6 Shows a schematic diagram of the relationship between the diffraction efficiency of a reflection-type volume holographic grating and the wavelength; Figure 7 Shows a received optical power data graph of the double self-focusing lens probe for reflected light at different pitches according to an embodiment of the present invention; Figure 8 Shows a received optical power data graph of the double self-focusing lens probe for fluorescence at different pitches according to an embodiment of the present invention; Figure 9 Shows a comparison data graph of the received optical power of the double self-focusing lens probe and the direct coupling probe; Figure 10 Shows a simulation overall model diagram of the fluorescence optical fiber probe device for three-phase flow detection according to an embodiment of the present invention; Figure 11 Shows a schematic diagram of the light reception situation of the first photoelectric conversion module of the fluorescence optical fiber probe device for three-phase flow detection according to an embodiment of the present invention; Figure 12 Shows a schematic diagram of the light reception situation of the second photoelectric conversion module of the fluorescence optical fiber probe device for three-phase flow detection according to an embodiment of the present invention, Wherein, Figures 1 to 5 And Figure 10 The corresponding relationship between the reference numerals and the components in 102. Encapsulation housing, 104. Sapphire probe, 106. Large-diameter self-focusing lens, 108. Small-diameter self-focusing lens, 110. Integrated optical fiber bundle structure, 1102. Transmitting optical fiber, 1104. Receiving optical fiber, 112. Laser emission module, 1122. Laser emission control circuit board, 1124. Fiber laser emitter, 114. Collimating lens, 116. Trapezoidal waveguide structure, 118. First optical focusing component, 120. Second optical focusing component, 122. Reflective volume holographic grating, 124. First photoelectric conversion module, 126. Second photoelectric conversion module, 128. Main control module, 130. PIN photodiode, 132. I / V conversion circuit board, 134. Conical ferrule press-sealing structure, 202. Water tank. Detailed implementation manners

[0035] In order to more clearly understand the above objects, features and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0036] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0037] The following will be combined with Figures 1 to 12 to specifically illustrate a fluorescence optical fiber probe device for three-phase flow detection according to an embodiment of the present invention.

[0038] As Figures 1 to 4As shown, a fluorescence optical fiber probe device for three-phase flow detection according to an embodiment of the present invention includes: a packaging housing 102, a sapphire probe 104, a large-diameter self-focusing lens 106, a small-diameter self-focusing lens 108, an integrated optical fiber bundle structure 110, a laser emission module 112, a collimating lens 114, a trapezoidal waveguide structure 116, a first optical focusing component 118, a second optical focusing component 120, a first photoelectric conversion module 124, a second photoelectric conversion module 126, a main control module 128, etc. The sapphire probe 104 is arranged in the packaging housing 102 and extends out from the narrower end of the packaging housing 102 for direct contact with the three-phase fluid medium. The large-diameter self-focusing lens 106 is arranged in the packaging housing 102 and is above the sapphire probe 104. The small-diameter self-focusing lens 108 is arranged in the packaging housing 102 and is above the large-diameter self-focusing lens 106. The two form an axially dimensionally compact double self-focusing lens coupling system with high coupling efficiency, which can effectively solve the problem that it is difficult to match the diameters of the optical fiber bundle and the sapphire probe 104. The integrated optical fiber bundle structure 110 is arranged in the packaging housing 102 and one end is connected above the small-diameter self-focusing lens 108, such as Figure 3 and Figure 4As shown. The other end of the integrated optical fiber bundle structure 110 extends into the main cavity of the packaging housing 102, and is divided into a transmitting optical fiber 1102 and a receiving optical fiber 1104 in the main cavity. The integrated optical fiber bundle structure 110 is formed by coupling three or seven optical fibers into a bundle. The transmitting optical fiber 1102 is a single-mode or multi-mode optical fiber with a numerical aperture of 0.13 - 0.22, capable of adapting to the transmission of the excitation light. The receiving optical fiber 1104 is a multi-mode optical fiber with a numerical aperture of 0.275, capable of collecting the reflected light and fluorescence. The laser emission module 112 includes a laser emission control circuit board 1122 and a fiber laser emitter 1124, and is used to generate and output laser light. The collimating lens 114 is disposed above the receiving optical fiber 1104, and can collimate and shape the reflected light and fluorescence. The trapezoidal waveguide structure 116 is disposed above the collimating lens 114, and is used to transmit the collimated fluorescence and reflected light, and realize the turning of the reflected light optical path to linear propagation. The first optical focusing component 118 and the second optical focusing component 120 are arranged side by side above the trapezoidal waveguide structure 116. A reflection-type volume holographic grating 122 is disposed below the first optical focusing component 118, corresponding to above the collimating lens 114. The first optical focusing component 118 is connected to the first photoelectric conversion module 124, and the second photoelectric conversion module 126 is connected above the second optical focusing component 120. The first optical focusing component 118 focuses the fluorescence on the first photoelectric conversion module 124, and the second optical focusing component 120 focuses the reflected light on the second photoelectric conversion module 126. The main control module 128 is respectively connected to the laser emission module 112, the first photoelectric conversion module 124, and the second photoelectric conversion module 126. Thus, by constructing a coaxial gradient refractive index optical path coupling system, the efficient transmission of the emitted laser and the precise focusing and collection of the reverse fluorescence signal are realized. The reflection-type volume holographic grating 122 is innovatively introduced, effectively avoiding the optical power attenuation caused by optical fiber beam splitting and filter wafers, which is beneficial to ensuring the optical signal transmission efficiency and detection accuracy.

[0039] Further, the design parameters of the reflection-type volume holographic grating 122 are determined by a reflection-type volume holographic grating diffraction efficiency model established based on the Kogelnik coupled-wave theory. The reflection-type volume holographic grating diffraction efficiency model includes:

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047] , Among them, is characterized by the angle formed by the incident light and the normal direction z of the recording plane in the holographic medium, is characterized by the grating vector and the angle formed by the normal direction z of the recording plane, and n0 is characterized by the average refractive index, is characterized by the wavelength of the incident light in vacuum, is characterized by the interference fringe spacing, is characterized by the angle formed by the fringe plane and the object light or reference light in the holographic medium, is characterized by the wavelength of the recording light in vacuum, is characterized by the wavelength of the recording light in the holographic medium, is characterized by the coupling coefficient of the grating, and n1 is characterized by the refractive index modulation degree, is characterized by the incident light wave vector in the medium, is characterized by the wave number in vacuum, is characterized by the average absorption coefficient of the medium, is characterized by the modulation amplitude of the absorption constant, is characterized by the phase mismatch parameter, is characterized by the grating vector generated during interference recording, is characterized by the magnitude of the grating vector generated during interference recording, is characterized by the unit vector of the normal direction z of the recording material, is characterized by the tilt factor of the diffracted light, is characterized by the tilt factor of the incident light, is characterized by the propagation constant root of the solution of the wave coupling differential equation, d is characterized by the physical thickness of the volume grating, and S(0) is characterized by the amplitude of the diffracted light, is characterized by the diffraction efficiency, and j is the imaginary unit.

[0048] For the double-wavelength scenario of 470 nm excitation light and 515 nm fluorescence, a reflective volume holographic grating structure with a refractive index modulation of 0.115 and a thickness of 50 μm is optimized and designed.

[0049] Specifically, the two recording lights form angles of 0° and 225° with the normal direction z of the recording material respectively. At this time, is half of the included angle of the two recording lights, that is, 67.5°. From the geometric relationship, it can be obtained that at this time is 22.5°, the wavelength of light in vacuum λ0 is recorded as 0.47 μm, the refractive index modulation degree n1 is 0.115, the average refractive index n0 is 1.57, the average absorption coefficient α of the medium and the modulation amplitude α1 of the absorption constant are both set to 0, and the grating thickness d is 50 μm. Thereby determining the grating vector generated during interference recording and its vector magnitude , characterizing the spatial periodic structure of interference recording.

[0050] For the recording wavelength λ0, the Bragg optimal incident angle is determined through the wave vector phase matching condition, that is, it holds when the angle between the incident light and the normal direction z of the recording plane is 0°, to ensure that there is no influence of the angular offset. Calculate the wavelength range point by point. At each specific incident wavelength λ, calculate the incident light wave vector in the medium and its wave number in vacuum, the phase mismatch parameter , as well as the tilt factor of the diffracted light and the tilt factor of the incident light. According to the refractive index modulation degree n1 and the wave number in vacuum, calculate the coupling coefficient of the grating, and establish a coupled wave equation system for the propagation of light waves in the volume grating at each different incident wavelength λ, and solve the numerical solution of the equation system. According to the numerical solution and the physical thickness d of the volume grating, solve the amplitude S(0) of the diffracted light, and finally calculate the diffraction efficiency of the volume grating at each wavelength λ. The results are as Figure 6 shown. This part is realized through Python programming calculation. When using reflective volume holographic grating structures with different refractive index modulation degrees and thicknesses, substitute the corresponding parameter settings to draw the relationship diagram of the corresponding diffraction efficiency and wavelength, and thus determine the design parameters of the reflective volume holographic grating.

[0051] As Figure 5 and Figure 6 can be seen, for the reflective volume holographic grating structure with a refractive index modulation degree of 0.115 and a thickness of 50 μm, the diffraction efficiency can reach 1 when the incident wavelength is 470 nm, while it is only 0.0162 at the wavelength of 515 nm. This significant difference confirms the effectiveness of the reflective volume holographic grating 122 in the dual-wavelength spectral separation of 470 nm and 515 nm.

[0052] Furthermore, a reflective film or a mirror is provided on the inclined surface of the trapezoidal waveguide structure 116, and the inclination angle between the inclined surface and the horizontal straight line is determined according to the diffraction angle of the reflective volume holographic grating 122.

[0053] Furthermore, the inclination angle of the inclined surface of the trapezoidal waveguide structure 116 is , where θ1 is the diffraction angle of the reflection-type volume holographic grating 122.

[0054] Thus, when transmitting the collimated fluorescence and reflected light, the optical path of the reflected light is turned to straight-line transmission. For example, when the diffraction angle of the reflection-type volume holographic grating 122 is 45°, the inclination angle of the inclined surface of the trapezoidal waveguide structure 116 is 67.5°, as Figure 2 shown.

[0055] Furthermore, the distance between the collimating lens 114 and the receiving optical fiber 1104 does not exceed 3 mm; the distances between the first optical focusing component 118 and the first photoelectric conversion module 124, and between the second optical focusing component 120 and the second photoelectric conversion module 126 are both less than 15 mm. Thus, it further ensures that the fluorescence and reflected light can be accurately focused.

[0056] In addition, the connecting length of the collimating lens 114 and the trapezoidal waveguide structure 116 is 4.8 mm, the connecting length of the reflection-type volume holographic grating 122 and the trapezoidal waveguide structure 116 is 6 mm, and the connecting length of the first optical focusing component 118 and the trapezoidal waveguide structure 116 is 6 mm. The straight-line distance between the collimating lens 114 and the reflection-type volume holographic grating 122 is 10 mm.

[0057] Furthermore, the first optical focusing component 118 is a focusing lens configured with an AR antireflection coating of 400 - 700 nm, with a thickness of 3 mm; the second optical focusing component 120 is a focusing lens configured with an AR antireflection coating of 400 - 700 nm, with a thickness of 3 mm; the collimating lens 114 is a high-refractive-index lens with both sides coated with an AR antireflection coating of 400 - 700 nm, with a thickness of 2 mm, and the divergence angle for the reflected light of 470 nm does not exceed 3°, and the divergence angle for the fluorescence of 515 nm does not exceed 2.5°.

[0058] Thus, it further ensures that after the reflected light and fluorescence are preliminarily and simply collimated and shaped, they can be accurately focused respectively.

[0059] Furthermore, the diameter of the large-diameter self-focusing lens 106 is 1 mm, and the pitch is 0.25P - 0.75P; the diameter of the small-diameter self-focusing lens 108 is 0.5 mm, and the pitch is 0.25P.

[0060] By establishing a pitch matching model through ZEMAX optical simulation, the large-diameter self-focusing lens 106 is A (1 mm), and the small-diameter self-focusing lens 108 is B (0.5 mm). The received power of the reflected light by the double self-focusing lens probe at different pitches is as Figure 7 shown. The received power of the fluorescence by the double self-focusing lens probe at different pitches is as Figure 8 shown. FromFigure 7 and Figure 8 It can be seen that when the pitch of A is fixed and the pitch of B is changed, both the reflected light and the fluorescence results show a periodic pattern. At the same time, during the process of changing the pitch of the self-focusing lens, the longer the lens length, the greater the loss.

[0061] A pitch matching model is established through ZEMAX optical simulation. The pitch of the fixed small-diameter lens is optimized to 0.25P, and at the same time, the large-diameter lens is adjusted within the pitch range of 0.25P to 0.75P to achieve axial matching of the light field. The optical powers of both fluorescence and reflected light are set to P0, and simulation calculations are performed. The comparison of the received optical powers between the double self-focusing lens probe and the direct coupling probe is as Figure 9 shown. As Figure 9 can be seen, the received powers of both fluorescence and reflected light are better than those of the direct coupling reference. Especially under the optimized configuration where both lenses use a pitch of 0.25P, the received power of fluorescence reaches 0.454P0, which is 1.57 times higher than 0.290P0 of direct coupling; the reflected light power increases from the reference value of 0.185P0 to 0.482P0, achieving an efficiency gain of 2.6 times.

[0062] As Figures 7 to 9 can be seen, the best effect is achieved when the pitches of both the double self-focusing lenses A and B are 0.25P. Through the parametric design of the pitch, the problem that it is difficult to match the diameter of the optical fiber bundle with that of the sapphire probe 104 is effectively solved, providing theoretical support for the miniaturized probe packaging.

[0063] In this application, the first optoelectronic conversion module 124 and the second optoelectronic conversion module 126 have the same structure. Both the first optoelectronic conversion module 124 and the second optoelectronic conversion module 126 include a PIN photodiode 130 and an I / V conversion circuit board 132 connected to each other. The distance between the PIN photodiode 130 and the first optical focusing component 118 or the second optical focusing component 120 is 7 mm; the laser emission module 112 includes a laser emission control circuit board 1122 and an optical fiber laser emitter 1124 connected to each other. Thus, the separate focusing detection effects of fluorescence and reflected light are further ensured.

[0064] Furthermore, as Figure 1 shown, the fluorescence optical fiber probe device for three-phase flow detection further includes: a tapered ferrule press-sealing structure 134, sleeved on the packaging housing 102 and corresponding to the position of the integrated optical fiber bundle structure 110, which can perform high-pressure sealing to establish a high-pressure sealing connection system.

[0065] Based on the ZEMAX optical simulation platform, a system model of the fluorescence optical fiber probe device for three-phase flow detection proposed in the present invention is constructed. Its core components adopt modular design, as Figure 10As shown in the figure. Integrated optical fiber bundle structure 110: It includes seven 62.5 / 125μm standard optical fibers (numerical aperture 0.275). The top optical fiber is configured as the transmitting optical fiber 1102 as the excitation light transmission channel, and the other six optical fibers are configured as receiving optical fibers 1104 as the light receiving channels. The optical coupling module consists of a double self-focusing lens (with diameter specifications of 0.5mm and 1mm respectively, pitch 0.25P), and a sapphire probe 104 (diameter 0.8mm, end angle 90°). The volume holographic spectral detection includes three lenses coated with 400 - 700nm AR film, a reflective volume holographic grating 122 (diffraction angle 45°), and a waveguide inclined plane coated with a reflective film.

[0066] In the simulation parameter setting, due to software limitations, we cannot simulate the entire fluorescence excitation process. The fluorescence emitted by the analyte in the solution is independent of the excitation light direction and shows spherical radiation. Therefore, we set an elliptical light source to simulate fluorescence emission, and both its power and the power of the excitation light source are set to 1W. It is worth mentioning that when analyzing the reflection signal generated by the contact between the sapphire probe 104 and the air medium, we exclude the interference of the water tank 202 model, which is equivalent to placing the probe in the air. Although the waveguide trapezoidal structure is simplified to an inclined plane due to the limitations of the simulation software for modeling, the setting of its reflective film parameters and the shape structure can ensure the effectiveness of the simulation.

[0067] First, use the ZEMAX simulation software to simulate and calculate the total power of the reflected light and fluorescence of all receiving optical fibers 1104 respectively. Subsequently, connect the probe to the volume holographic spectral system model for simulation to quantitatively obtain the parameters of the reflected light power and fluorescence power received by the detector after spectral splitting. Finally, by comparing and analyzing the simulation data before and after, the system will evaluate the functional effectiveness of the device and its energy conversion efficiency.

[0068] The light reception situations of the first photoelectric conversion module 124 and the second photoelectric conversion module 126 of the fluorescence optical fiber probe device for three-phase flow detection are as Figure 11 and Figure 12 shown.

[0069] From the simulation results, when the probe contacts the air, 82.69% of the light power of the reflected light can be retained after passing through the volume holographic spectral system; when contacting the water medium, the reflected light power decreases by one order of magnitude compared with the bubble environment, but still can maintain a transmission efficiency of 88.17%. This result is consistent with the theoretical expectation, verifying the reliability of the simulation.

[0070] Under the oil medium condition, that is, when fluorescence is emitted from a certain distance from the probe tip and transmitted through an optical fiber (ignoring the influence of the reflected light in the water medium and performing separate simulations), the volume holographic beam splitting system can still maintain 71.11% of the fluorescence power. Considering that in practical applications, the excitation light often differs from the excited fluorescence by three orders of magnitude, simulations were carried out under the condition that the fluorescence power P1 is less than the excitation light P0 by three orders of magnitude. The results show that the system still maintains a transmission efficiency of 71.09%, which is in good agreement with the previous results.

[0071] Further analysis shows that when the excitation light P0 is transmitted in water and excites the fluorescence in the oil medium, the influence of the reflected light on the fluorescence receiver is two orders of magnitude different from the influence of the fluorescence power P1 on the fluorescence receiver. This result indicates that the reflected light signal transmitted by the probe in water will not cause significant interference to the fluorescence detection. Similarly, the influence of the fluorescence signal on the reflected light detector can also be ignored, and there is also a three-order-of-magnitude difference between the two (when in contact with water). And in the case of bubbles, the influence of the reflected light on the fluorescence receiver also has an order-of-magnitude difference compared with the true fluorescence signal P1.

[0072] Through the above simulation experiment analysis, it is proved that the designed device effectively solves the problem of large-scale attenuation of optical power caused by traditional filter plates and independent optical fiber beam splitting, and at the same time realizes the high-efficiency beam splitting of reflected light and fluorescence. While maintaining a high optical power transmission efficiency, the device ensures the independence of reflected light and fluorescence detection.

[0073] In the present invention, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance; the term "plurality" means two or more, unless otherwise clearly defined. Terms such as "installed", "connected", "connected", "fixed" and other terms should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0074] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore, cannot be construed as a limitation of the present invention.

[0075] In the description of this specification, the descriptions of terms such as "one embodiment", "some embodiments", "specific embodiments", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or instance. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0076] The foregoing are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A fluorescence optical fiber probe device for three-phase flow detection, characterized in that Comprising: An encapsulation housing; A sapphire probe, disposed within the encapsulation housing and protruding from the encapsulation housing; A large-diameter self-focusing lens, disposed within the encapsulation housing and above the sapphire probe; a small-diameter self-focusing lens, disposed within the encapsulation housing and above the large-diameter self-focusing lens; An integrated optical fiber bundle structure, disposed within the encapsulation housing, with one end connected above the small-diameter self-focusing lens, and the other end of the integrated optical fiber bundle structure extending into the main cavity of the encapsulation housing, and being divided into a transmitting optical fiber and a receiving optical fiber within the main cavity; a laser emission module, connected to the transmitting optical fiber; a collimating lens, disposed above the receiving optical fiber; a trapezoidal waveguide structure, disposed above the collimating lens; a first optical focusing component and a second optical focusing component, arranged side by side above the trapezoidal waveguide structure, wherein a reflection-type volume holographic grating is disposed below the first optical focusing component, corresponding above the collimating lens; the first optical focusing component is connected to a first photoelectric conversion module, and the second photoelectric conversion module is connected above the second optical focusing component; a main control module, respectively connected to the laser emission module, the first photoelectric conversion module, and the second photoelectric conversion module.

2. The fluorescence optical fiber probe device for three-phase flow detection according to claim 1, wherein The sapphire probe protrudes from the narrower end of the encapsulation housing.

3. The fluorescence optical fiber probe device for three-phase flow detection according to claim 1, characterized in that, A reflection film or a mirror is disposed on the inclined surface of the trapezoidal waveguide structure, and the inclination angle between the inclined surface and the horizontal straight line is determined according to the diffraction angle of the reflection-type volume holographic grating.

4. The fluorescence optical fiber probe device for three-phase flow detection according to claim 3, characterized in that, The inclination angle of the inclined surface of the trapezoidal waveguide structure is , where θ1 is the diffraction angle of the reflection-type volume holographic grating.

5. The fluorescence optical fiber probe device for three-phase flow detection according to claim 1, wherein The distance between the collimating lens and the receiving optical fiber does not exceed 3 mm; the distances between the first optical focusing component and the first photoelectric conversion module, and between the second optical focusing component and the second photoelectric conversion module are both less than 15 mm.

6. The fluorescence optical fiber probe device for three-phase flow detection according to claim 1, characterized in that The first optical focusing component is a focusing lens configured with an AR antireflection coating of 400 - 700 nm and has a thickness of 3 mm; The second optical focusing component is a focusing lens configured with an AR antireflection coating of 400 - 700 nm and has a thickness of 3 mm; the collimating lens is a high-refractive-index lens coated with an AR antireflection coating of 400 - 700 nm on both sides, with a thickness of 2 mm, and the divergence angle for the reflected light at 470 nm does not exceed 3°, and the divergence angle for the fluorescence at 515 nm does not exceed 2.5°.

7. The fluorescence optical fiber probe device for three-phase flow detection according to claim 1, characterized in that, The diameter of the large-diameter self-focusing lens is 1 mm, and the pitch is 0.25P - 0.75P; the diameter of the small-diameter self-focusing lens is 0.5 mm, and the pitch is 0.25P.

8. The fluorescence optical fiber probe device for three-phase flow detection according to claim 1, wherein The integrated optical fiber bundle structure is formed by coupling three optical fibers or seven optical fibers into a bundle. The transmitting optical fiber is a single-mode or multi-mode optical fiber with a numerical aperture of 0.13 - 0.22, and the receiving optical fiber is a multi-mode optical fiber with a numerical aperture of 0.275; both the first photoelectric conversion module and the second photoelectric conversion module include a PIN photodiode and an I / V conversion circuit board connected thereto, and the distance between the PIN photodiode and the first optical focusing component or the second optical focusing component is 7 mm; the laser emission module includes a laser emission control circuit board and a fiber laser emitter connected thereto.

9. The fluorescence optical fiber probe device for three-phase flow detection according to claim 1, wherein It further includes a conical ferrule press-sealing structure which is sleeved on the encapsulation housing and corresponds to the position of the integrated optical fiber bundle structure for high-pressure sealing.

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