Coaxial fiber optic sensor

Abstract

The present invention relates to the technical field of optical fiber sensors, and particularly to a coaxial optical fiber sensor. The coaxial optical fiber sensor of the present invention includes a housing with an inner cavity, a laser, a receiver, and a lens group. Laser interfaces, a detection interface, and a receiver interface that are all communicated with the inner cavity are formed on the housing. The detection laser emitted by the laser forms an emission optical path between the laser interface and the detection interface, and the emission optical path sequentially passes through a lens, a beam splitting prism, and a combined lens; the detection laser returned by the detection interface forms a detection optical path between the detection interface and the receiver interface, and the detection optical path sequentially passes through the combined lens and the beam splitting prism. The present invention makes the emission optical path and the detection optical path of the optical fiber amplifier into an optical path coaxial structure, improving the production efficiency and detection accuracy; and a lens group combining a lens and a combined lens is adopted on the optical path of the emitter for focusing, improving the coupling efficiency between the emitter light and the optical fiber.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber optic sensors, and particularly relates to a coaxial fiber optic sensor. Background Art

[0002] Fiber optic sensors are commonly used sensors in industrial automation and are widely applied. Fiber optic sensors usually include two parts: one is a fiber optic sensing head for transmitting optical signals; the other is a fiber optic amplifier for modulating and demodulating the optical signals transmitted by the fiber optic sensing head.

[0003] Inside the fiber optic amplifier, there are an optical transmitter and an optical receiver. The modulated light generated by the optical transmitter is projected onto the detected object through the fiber optic sensing head. The surface of the detected object will generate reflected light, and the reflected light is transmitted to the optical receiver through another fiber optic sensing head. In this process, the paths of modulated light emission and reception are separated, that is, they are transmitted through two fiber optic sensing heads respectively. The structure is complex, occupies a large space, is not conducive to some high-precision measurements, and the production process of the dual fiber optic sensing heads is complex and the efficiency is low. Summary of the Invention

[0004] The coaxial fiber optic sensor provided by the present invention overcomes the above-mentioned deficiencies of the prior art. It makes the emission optical path and the detection optical path of the fiber optic amplifier into an optically coaxial structure, ensuring that detection can be completed using one fiber optic, improving production efficiency and detection accuracy; it uses a lens group combining a lens and a combined lens to focus on the optical path of the transmitter, improving the coupling efficiency between the light of the transmitter and the fiber optic.

[0005] To achieve the above object, the present invention is realized through the following technical solutions: The coaxial fiber optic sensor provided by the present invention includes a housing with an inner cavity, a laser, a receiver, and a lens group. The lens group includes a lens, a beam splitting prism, and a combined lens. Laser interfaces, a detection interface, and a receiver interface that are all communicated with the inner cavity are further formed on the housing. The laser is installed at the laser interface, the receiver is installed at the receiver interface, the lens, the beam splitting prism, and the combined lens are sequentially arranged between the laser interface and the detection interface, and the receiver interface is arranged on the side of the housing;

[0006] The detection laser emitted by the laser forms an emission optical path between the laser interface and the detection interface, and the emission optical path sequentially passes through the lens, the beam splitting prism, and the combined lens;

[0007] The detection laser returned from the detection interface forms a detection optical path with the receiver interface, and the detection optical path sequentially passes through the combined lens and the beam splitting prism.

[0008] An improvement of the coaxial fiber optic sensor disclosed by the present invention is that the laser interface and the detection interface are relatively arranged on the housing;

[0009] The detection laser emitted by the above-mentioned laser forms an emission optical path between the laser interface and the detection interface and exits from the detection interface. The above-mentioned emission optical path sequentially passes through a lens, a beam splitting prism, and a combined lens. The optical axes of the lens and the combined lens coincide, and the mirror surface of the beam splitting prism facing the laser is perpendicular to the optical axis of the lens or the combined lens;

[0010] A detection optical path is formed between the detection laser returned by the above-mentioned detection interface and the receiver interface. The above-mentioned detection optical path is reflected by the beam splitting surface of the beam splitting prism to the receiver interface after passing through the combined lens. The included angle between the beam splitting surface of the above-mentioned beam splitting prism and the optical axis of the lens or the combined lens is less than 90 degrees. Preferably, the included angle between the beam splitting surface of the beam splitting prism and the optical axis of the lens or the combined lens is 45 degrees. The beam splitting surface of the beam splitting prism is the inclined surface of the prism, and the same applies hereinafter.

[0011] An improvement of the coaxial fiber optic sensor disclosed in the present invention, the above-mentioned receiver interface and the detection interface are relatively arranged on the housing;

[0012] The detection laser emitted by the above-mentioned laser forms an emission optical path between the laser interface and the detection interface and exits from the detection interface. The above-mentioned emission optical path sequentially passes through a lens, a beam splitting prism, and a combined lens. The optical axes of the lens and the combined lens are perpendicular, and the included angle between the beam splitting surface of the beam splitting prism and the optical axis of the lens or the combined lens is less than 90 degrees; preferably, the included angle between the beam splitting surface of the beam splitting prism and the optical axis of the lens or the combined lens is 45 degrees.

[0013] A detection optical path is formed between the detection laser returned by the above-mentioned detection interface and the receiver interface. The above-mentioned detection optical path is transmitted through the inclined surface of the beam splitting prism and passes through the right-angle surface and then reaches the receiver interface after passing through the combined lens. The included angle between the beam splitting surface of the above-mentioned beam splitting prism and the optical axis of the lens or the combined lens is less than 90 degrees.

[0014] Preferably, the beam splitting prism is composed of a pair of right-angled prisms glued together to form a geometric cuboid (including a geometric regular hexahedron, i.e., a cube, and a cuboid with square top and bottom surfaces). A beam splitting film is plated on the inclined surface of one of the right-angled prisms.

[0015] An improvement of the coaxial fiber optic sensor disclosed in the present invention, the above-mentioned coaxial fiber optic sensor further includes an optical fiber assembly. The above-mentioned optical fiber assembly at least includes an optical fiber. The above-mentioned optical fiber is connected to the detection interface, and the center line of the above-mentioned optical fiber coincides with the above-mentioned detection optical path or the emission optical path to satisfy the emission or return of light from the optical fiber.

[0016] An improvement of the coaxial fiber optic sensor disclosed in the present invention, the above-mentioned optical fiber assembly further includes an optical fiber bracket. The optical fiber bracket includes an optical fiber interface that cooperates with the optical fiber. The optical fiber is installed in the optical fiber interface, and the optical fiber bracket is connected to the detection interface.

[0017] An improvement of the coaxial fiber optic sensor disclosed by the present invention. The above-mentioned combined lens includes a lens surface I and a lens surface II. The lens surface I includes a first mirror surface and a second mirror surface. The first mirror surface and the second mirror surface are coaxially arranged, and the first mirror surface is arranged on the outer periphery of the second mirror surface. The lens surface II includes a third mirror surface.

[0018] An improvement of the coaxial fiber optic sensor disclosed by the present invention. The spherical directions of the above-mentioned second mirror surface and the third mirror surface are the same, and the spherical directions of the first mirror surface and the second mirror surface are opposite.

[0019] An improvement of the coaxial fiber optic sensor disclosed by the present invention. The spherical surfaces of the above-mentioned first mirror surface and the second mirror surface protrude outward from the combined lens.

[0020] An improvement of the coaxial fiber optic sensor disclosed by the present invention. The coaxial fiber optic sensor further includes a receiver fixing bracket. The receiver fixing bracket is connected to the receiver interface, and the receiver fixing bracket has a reflection cavity with a parabolic curved surface morphology on the inner surface. The reflection cavity cooperates with the receiver interface and communicates with the inner cavity of the housing. The receiver is arranged in the reflection cavity. The inner surface of the reflection cavity forms a reflection surface, and an additional reflection layer, such as a reflection coating, can be formed on the inner surface, so as to ensure that part of the light is effectively reflected to the receiver and received.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: A laser interface, a detection interface, and a receiver interface are formed on the housing. The detection laser emitted by the laser forms an emission optical path between the laser interface and the detection interface, and the detection laser returned by the detection interface forms a detection optical path with the receiver interface. The emission optical path and the detection optical path are coaxially designed, ensuring that detection can be completed using a single optical fiber, improving production efficiency and detection accuracy; The lens focusing method combining a lens and a combined lens is adopted on the emission optical path, ensuring that the divergence angle of the focused light is extremely small. The smaller divergence angle improves the coupling efficiency between the emitter light and the optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 It is a schematic diagram of the working state of the first embodiment of the present application;

[0024] Figure 2 is Figure 1 a schematic diagram of the emission state of the embodiment;

[0025] Figure 3 Yes Figure 1 Schematic diagram of the reception status of the implementation mode;

[0026] Figure 4 It is a schematic structural diagram of a combined lens;

[0027] Figure 5 It is a schematic diagram of the working status of the second implementation mode of this application;

[0028] Figure 6 It is a schematic diagram of the working status of the third implementation mode of this application;

[0029] Figure 7 It is an equivalent schematic diagram of the lens of this application, where a is the actual lens scheme and b is the equivalent scheme;

[0030] Figure 8 It is a schematic diagram of the detection optical path splitting of this application, where a is the optical path schematic diagram of the first part of light and b is the optical path schematic diagram of the second part of light;

[0031] Figure 9 It is a typical far-field luminous intensity distribution diagram of a laser.

[0032] 1. Laser; 2. Lens; 3. Beam splitter prism; 4. Combined lens; 5. Fiber optic holder; 6. Optical fiber; 7. Housing; 8. Receiver fixing bracket; 9. Receiver Specific implementation mode

[0033] The present invention will be described in detail below in conjunction with the implementation modes shown in the drawings. However, these implementation modes do not limit the present invention, and any structural, method, or functional transformation made by those of ordinary skill in the art based on these implementation modes is included in the protection scope of the present invention.

[0034] In the embodiment shown in the following figure, the beam splitter prism is a cube prism formed by gluing a pair of right-angled prisms.

[0035] As shown in the attached Figure 1 、 2 、3, 5, 6, the coaxial fiber optic sensor provided by the present invention includes a housing 7 with an inner cavity, a laser 1, a receiver 9, and a lens group. The above lens group includes a lens 2, a beam splitter prism 3, and a combined lens 4. The housing 7 is used to fix relevant optical path components. It should be noted that a toothed extinction structure is provided at the top of the housing 7 shown in the drawings, and the toothed extinction structure and the receiver are correspondingly arranged, aiming to reduce the influence of the reflection component generated when the light emitter of the coaxial fiber optic sensor of the present invention passes through the beam splitter prism 3 on the receiver. The lens 2 is a convex lens, and the two surfaces of the lens 2 are aspherical surfaces. The aspherical design is beneficial to the focusing of the light from the laser.

[0036] As shown in the attachedFigure 1 The figure shows the working state of the first embodiment of the present application. Laser interfaces, detection interfaces, and receiver interfaces that are all connected to the inner cavity are further formed on the outer shell 7. The laser interfaces and the detection interfaces are oppositely arranged on the outer shell 7. The laser 1 is installed at the laser interface, the receiver 9 is installed at the receiver interface, the lens 2, the beam splitting prism 3, and the combined lens 4 are sequentially arranged between the laser interface and the detection interface, and the receiver interface is arranged on the side of the outer shell 1.

[0037] As shown in the attached Figure 2 The figure shows Figure 1 the emission state of the embodiment. The detection laser emitted by the laser 1 forms an emission optical path between the laser interface and the detection interface. The emission optical path sequentially passes through the lens 2, the beam splitting prism 3, and the combined lens 4 and exits from the detection interface. The optical axes of the lens 2 and the combined lens 4 coincide, and the mirror surface of the beam splitting prism 3 facing the laser 1 is perpendicular to the optical axis of the lens 2 or the combined lens 4. The laser 1 uses a semiconductor laser as the light emitter. Compared with the LED light emitter used on traditional fiber optic amplifiers, the divergence angle of the semiconductor laser is very small, which is beneficial for the subsequent lens 2 to focus.

[0038] As shown in the attached Figure 3 The figure shows Figure 1 the reception state of the embodiment. A detection optical path is formed between the detection laser returned by the detection interface and the receiver interface. The detection optical path sequentially passes through the combined lens 4 and the beam splitting prism 3. After passing through the combined lens 4, the detection optical path is reflected by the mirror surface formed by the inclined surface of the beam splitting prism 3 to the receiver interface, and the optical receiver 9 converts the optical signal into an electrical signal.

[0039] As shown in the attached Figure 1 and 2 3 and 5, the coaxial fiber optic sensor of the invention further includes a fiber optic component. The fiber optic component at least includes a fiber 6. The fiber 6 is connected to the detection interface. The fiber 6 is used to transmit optical signals, and its center line coincides with the detection optical path or the emission optical path to satisfy the emission or return of light from the fiber 6. The fiber optic component further includes a fiber optic holder 5. The fiber optic holder 5 includes a fiber optic interface that cooperates with the fiber 6. The fiber 6 is installed in the fiber optic interface. The fiber optic holder 5 is connected to the detection interface. The fiber optic holder 5 is used to fix the fiber 6. The fiber optic holder 5 and the outer shell 7 have corresponding limiting structures, which can limit the end face of the fiber 6 at the focus of the light.

[0040] As shown in the attached Figure 4The figure shows a structure of a combined lens in an embodiment. The combined lens 4 includes a lens surface I and a lens surface II. The combined lens 4 has a total of 3 mirror surfaces. The lens surface I includes a first mirror surface and a second mirror surface. The first mirror surface and the second mirror surface are coaxially arranged, and the first mirror surface 401 is arranged on the outer periphery of the second mirror surface 402. The lens surface II includes a third mirror surface 403. The spherical directions of the second mirror surface 402 and the third mirror surface 403 are the same. Functionally, the second mirror surface and the third mirror surface form a concave lens for secondary focusing of the emitter light after focusing by the lens 2. The spherical directions of the first mirror surface 401 and the third mirror surface 403 are opposite. Functionally, the first mirror surface 401 and the third mirror surface 403 form a convex lens to focus the light transmitted back by the fiber optic sensor head onto the optical receiver 9. The light emitted by the laser 1 passes through the lens 2, the beam splitter prism 3, and the combined lens 4 in sequence and is focused on the end face of the optical fiber 6. The light passing through the end face of the optical fiber 6 will be coupled into the optical fiber and transmitted to the other end of the optical fiber 6. When there is a detected object at the other end of the optical fiber 6, the transmitted light will produce diffuse reflection on the object surface. Part of the diffusely reflected light will be transmitted back to the surface of the combined lens 4 through the optical fiber 6. This part of the light passes through the combined lens 4, the beam splitter prism 3, and the receiver fixing bracket 8 in sequence and converges onto the optical receiver 9. The optical receiver 9 converts the optical signal into an electrical signal, and the presence or absence of the detected object can be judged by judging the magnitude of the electrical signal.

[0041] Appendix Figure 5

[0042] Appendix Figure 6

[0043] The working principle of the present invention is as follows:

[0044] The laser emitted by the laser passes through a lens 2 and is focused, then passes through a beam splitter prism, and is focused again by a combination lens, and then exits through an optical fiber or directly through a detection interface. After irradiating the sample, it returns after reflection; when the light received by the fiber optic sensor head passes through the combination lens 4, it can be divided into two parts. One part is the light in the spherical direction passing through the first mirror and the third mirror. This part of the light will be focused and finally converge on the optical receiver 9 again through the beam splitter prism 3; the other part is the light in the spherical direction passing through the second mirror and the third mirror. This part of the light is divergent. When this part of the light is reflected by the beam splitter prism 3, it will reach the inner wall of the receiver fixing bracket 8. The reflective layer on the inner wall can reflect this part of the light and focus these reflected lights on the optical receiver 9. The combination of the two parts is mainly to make full use of the returned light to obtain better detection intensity and detection accuracy.

[0045] As Figure 7 shown, the emission optical path assembly includes a lens 2, a beam splitter prism 3, and a combination lens 4; Figure 9 Figure is a typical far-field luminous intensity distribution diagram of the laser. It can be seen that the divergence angle of the laser is very large and cannot be directly coupled with the optical fiber. Therefore, a lens is needed to focus the laser beam. The present invention uses a double-lens method for focusing, and the divergence angle of the focusing effect is smaller than that of a single lens, which is beneficial to the coupling of light and the optical fiber.

[0046] The light emitted by the laser 1 will first pass through the lens 2. The lens 2 is a convex lens, which will contract the light emitted by the laser 1 to ensure that all the light emitted by the laser 1 can fall within the second mirror surface 402 of the combination lens 4 after passing through the beam splitter prism 3; when the light passing through the lens 2 passes through the beam splitter prism 3, the light will be divided into two parts. One part will continue to transmit along the original optical axis, and the other part will transmit along a direction perpendicular to the original optical axis by 90 degrees and reach the inner surface of the outer shell cavity. The inner surface of the outer shell cavity is provided with a serrated extinction structure to reduce the influence of this part of the light on the optical receiver; the light passing through the beam splitter prism 3 and continuing to transmit along the original optical axis will reach the second mirror surface 402 of the combination lens 4. The second mirror surface 402 and the third mirror surface 403 of the combination lens 4 form a concave lens. At this time, the first mirror surface 401 of the combination lens 4 does not play any role. Therefore, for the emission optical path, it can be Figure 7 equivalent as shown, Figure 7 a and Figure 7 b are schematic diagrams before and after equivalence respectively; the light passing through the combination lens 4 will finally be focused into a point. Fixing the optical fiber end face at this point can effectively couple the light into the optical fiber.

[0047] As Figure 8As shown, the receiving optical path component includes a combined lens 4, a beam splitting prism 3, and a receiver fixing bracket 8; in the case where there is an optical fiber, the diffuse reflection light generated on the surface of the detected object can be transmitted to the inner cavity of the housing through the optical fiber. When this part of the light passes through the combined lens 4, it will be divided into two parts; as Figure 8 As shown in Fig. a, the first part is the light that passes through the third mirror surface 403 and the first mirror surface 401 simultaneously. After passing through the first mirror surface 401 of the combined lens 4, this part of the light will be reflected by the beam splitting prism, and the included angle between the optical axis after reflection and the optical axis before reflection is 90 degrees; under the action of the combined lens 4 and the reflecting prism 3, the first part of the light will be focused on the optical receiver 9.

[0048] As Figure 8 As shown in Fig. b, the second part of the light is the light that passes through the third mirror surface 403 and the second mirror surface 402 simultaneously. After passing through the second mirror surface 402 of the combined prism 4, the divergence angle of this part of the light will increase. Under the action of the beam splitting prism 3, the optical axis of the light with an increased divergence angle will deflect by 90 degrees. A small part of the deflected light directly reaches the optical receiver 9, while most of it reaches the inner surface of the receiver fixing bracket 8. The surface of the receiver fixing bracket 8 is a parabolic curved surface and is coated with a reflective layer. The parabolic reflecting curved surface reflects and focuses the light onto the surface of the optical receiver 9. It should be noted here that in addition to the light whose optical axis is deflected by 90 degrees when the light passing through the combined lens 4 passes through the beam splitting prism 3, there is also some light that passes through the beam splitting prism 3 along the original optical axis, but this part of the light will not affect the detection, so it is not described in detail.

[0049] This invention application combines the emission and detection optical paths of a traditional optical fiber amplifier into one, forming an optical path coaxial structure. In this way, detection can be completed using a single optical fiber. Compared with a dual - fiber sensing head, the single - fiber sensing head can be made smaller in size and can be used for smaller and higher - precision detections; at the same time, the single - fiber sensing head is easier to produce in terms of technology. In the optical path design of the transmitter, a combination of a lens and a combined lens is used for focusing. After focusing, the divergence angle of the light is extremely small, and the smaller divergence angle can improve the coupling efficiency between the light emitted by the transmitter and the optical fiber.

[0050] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above - mentioned exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non - restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

[0051] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. Coaxial fiber optic sensor, comprising a housing with an inner cavity, a laser, a receiver, a lens group, and an optical fiber assembly. The lens group includes a lens, a beam splitting prism, and a combined lens. It is characterized in that The housing is further formed with a laser interface, a detection interface, and a receiver interface that are all in communication with the inner cavity. The laser is installed at the laser interface, the receiver is installed at the receiver interface, the lens, the beam splitting prism, and the combined lens are sequentially arranged between the laser interface and the detection interface, and the receiver interface is arranged on the side of the housing. The detection laser emitted by the laser forms an emission optical path between the laser interface and the detection interface, and the emission optical path sequentially passes through the lens, the beam splitting prism, and the combined lens. A detection optical path is formed between the detection laser returned by the detection interface and the receiver interface, and the detection optical path sequentially passes through the combined lens and the beam splitting prism. Among them, the optical fiber assembly at least includes an optical fiber, the optical fiber is connected to the detection interface, and the center line of the optical fiber coincides with the detection optical path or the emission optical path to satisfy the light emission or return from the optical fiber. The combined lens includes a lens surface Ⅰ and a lens surface Ⅱ. The lens surface Ⅰ includes a first mirror surface and a second mirror surface. The first mirror surface and the second mirror surface are coaxially arranged, and the first mirror surface is arranged on the outer periphery of the second mirror surface. The lens surface Ⅱ includes a third mirror surface. The spherical directions of the second mirror surface and the third mirror surface are the same, and the spherical directions of the first mirror surface and the second mirror surface are opposite.

2. The coaxial fiber optic sensor according to claim 1, It is characterized in that The laser interface and the detection interface are relatively arranged on the housing. The detection laser emitted by the laser forms an emission optical path between the laser interface and the detection interface and exits from the detection interface. The emission optical path sequentially passes through the lens, the beam splitting prism, and the combined lens, wherein the optical axes of the lens and the combined lens coincide, and the mirror surface of the beam splitting prism facing the laser is perpendicular to the optical axis of the lens or the combined lens. A detection optical path is formed between the detection laser returned by the detection interface and the receiver interface. The detection optical path is reflected by the beam splitting surface of the beam splitting prism to the receiver interface after passing through the combined lens, and the included angle between the beam splitting surface of the beam splitting prism and the optical axis of the lens or the combined lens is less than 90 degrees.

3. The coaxial fiber optic sensor according to claim 1, It is characterized in that The receiver interface and the detection interface are relatively arranged on the housing. The detection laser emitted by the laser forms an emission optical path between the laser interface and the detection interface and exits from the detection interface. The emission optical path sequentially passes through the lens, the beam splitting prism, and the combined lens, wherein the optical axes of the lens and the combined lens are perpendicular, and the included angle between the beam splitting surface of the beam splitting prism and the optical axis of the lens or the combined lens is less than 90 degrees. A detection optical path is formed between the detection laser returned by the detection interface and the receiver interface. The detection optical path is reflected by the beam splitting surface of the beam splitting prism to the receiver interface after passing through the combined lens, and the included angle between the beam splitting surface of the beam splitting prism and the optical axis of the lens or the combined lens is less than 90 degrees.

4. The coaxial fiber optic sensor according to claim 1, It is characterized in that The optical fiber component further includes an optical fiber holder, the optical fiber holder includes an optical fiber interface adapted to the optical fiber, the optical fiber is installed in the optical fiber interface, and the optical fiber holder is connected to the detection interface.

5. The coaxial optical fiber sensor according to claim 1, characterized in that the spherical surfaces of the first mirror and the second mirror protrude outward from the combined lens.

6. The coaxial optical fiber sensor according to any one of claims 1-3, characterized in that the beam splitting prism is composed of a pair of right-angled prisms glued together to form a geometric cuboid, and there is a beam splitting film on the inclined surface of one of the right-angled prisms.

7. The coaxial optical fiber sensor according to claim 1, characterized in that the coaxial optical fiber sensor further includes a receiver fixing bracket, the receiver fixing bracket is connected to the receiver interface, and the receiver fixing bracket has a reflection cavity with a parabolic curved surface on the inner surface, the reflection cavity cooperates with the receiver interface and communicates with the inner cavity of the housing, and the receiver is arranged in the reflection cavity.

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