A particle scattering light detection structure based on mie scattering theory

Abstract

The application relates to a particle scattering light detection structure based on Mie scattering theory, belonging to the technical field of particle optical detection, which comprises a main body shell, a communication block is arranged in the main body shell, an irradiation cavity is arranged in the communication block, a light inlet channel and a detection channel are arranged in the main body shell, a main gas path channel extending along the length direction of the gas inlet pipe is arranged in the gas inlet pipe, a reflection channel is further arranged between the light inlet channel and the detection channel in the main body shell, one end of the light inlet channel, the reflection channel and the main gas path channel is communicated with the irradiation cavity, one end of the detection channel is communicated with the other end of the reflection channel, a reflection surface is arranged in the communication block, a compensation gas path channel communicated with the irradiation cavity is arranged in the bottom inner wall of the reflection surface, the irradiation cavity is configured to reflect part of the scattering light emitted by the particles in the direction away from the reflection channel into the reflection channel by the reflection surface, and the compensation gas path channel is used for compensating the gas pressure at the reflection surface in the irradiation cavity.

Description

Technical Field

[0001] This application relates to the field of particle optical detection technology, and in particular to a particle scattering light detection structure based on Mie scattering theory. Background Technology

[0002] Currently, particulate matter detection technology is widely used in environmental monitoring, industrial production, medical and health fields. Traditional optical particulate matter detection technology mainly relies on the principle of light scattering, inferring parameters such as particle size and concentration by measuring the scattering signal of light by particulate matter. With the development of nanotechnology and precision manufacturing, the demand for single particle detection is increasing, especially in the fields of air pollution monitoring and virus detection. The accuracy and sensitivity of single particle scattering measurement technology have become a research hotspot.

[0003] The prior art relates to a speckle elimination device based on Mie scattering and perturbation-driven, including an incident light coupling device, an optical cavity, and optical components. The optical components are positioned opposite the incident light coupling device of the optical cavity. The optical cavity contains a transparent material that fills the entire optical cavity, and the transparent material contains medium particles whose dimensions can cause Mie scattering of the incident laser. The optical cavity and the optical components are each equipped with a perturbation-sensitive device, or only one of them.

[0004] The aforementioned and existing optical detection devices based on Mie scattering rely solely on the natural scattered light from particles, resulting in insufficient light collection and inadequate detection accuracy. Although there are existing solutions that utilize elliptical surfaces to increase the collection of scattered light, in actual fluid detection, when the airflow passes through an elliptical optical cavity from a circular air tube, the non-circular cavity required for optical correction conflicts with the circular, uniform cross-section flow channel required for fluid stability. The abrupt change in the flow channel cross-section leads to boundary layer separation, which in turn generates a backflow zone. Even with an asymmetric cavity, particle settling can still deviate from the focal point, causing signal fluctuations. Summary of the Invention

[0005] This application provides a particle scattering light detection structure based on Mie scattering theory, which can solve the problems of low detection accuracy and low signal-to-noise ratio caused by single-sided collection of scattered light for optical detection of single particles, and the signal fluctuation caused by particle settling off-focus when using an asymmetric elliptical optical structure to collect scattered light.

[0006] The technical solution of this application is as follows: a particle scattering light detection structure based on Mie scattering theory, comprising: The main body shell has a connecting block inside, an irradiation cavity inside the connecting block, an entrance light channel and a detection channel inside the main body shell, the entrance light channel and the detection channel being spaced apart and parallel to each other, an air inlet pipe outside the main body shell, a main air passage extending along its own length inside the air inlet pipe, and a reflection channel inside the main body shell between the entrance light channel and the detection channel. One end of the entrance light channel, the reflection channel and the main air passage are all connected to the irradiation cavity, one end of the detection channel is connected to the other end of the reflection channel, and a reflection component is provided inside the other end of the reflection channel. The main air passage is configured to provide the airflow to be detected and allow it to pass through the irradiation cavity. The light entrance passage is configured to provide an illumination beam and irradiate the airflow to be detected in the irradiation cavity, causing particles in the airflow to emit scattered light. The detection passage is configured to receive the scattered light from the particles and perform detection. A reflective surface is provided inside the connecting block. The reflective surface is located on the inner wall of the irradiation cavity on the side opposite to the reflective passage. A compensation air passage communicating with the irradiation cavity is opened on the bottom inner wall of the reflective surface. The irradiation cavity is configured as follows: The reflective surface is used to reflect a portion of the scattered light emitted by the particles in the direction away from the reflection channel back into the reflection channel; The gas pressure inside the irradiation cavity at the reflective surface is compensated by using a compensating gas path channel.

[0007] By adopting the above scheme, and by setting an illumination cavity with a reflective function inside the connecting block, the reflective surface can collect and reflect the scattered light that originally diverged backward or to the side and downward and could not be directly used, so that it flows into the reflection channel. Without increasing the power of the light source, the number of effective photons received by the photoelectric sensor is increased, thereby improving the detection sensitivity. At the same time, by using the set gas path compensation channel, when the airflow to be detected passes through the detection cavity, the airflow to be detected can automatically guide the external gas into the detection cavity through the gas path compensation channel. Thus, even if the particles in the airflow to be detected deviate in the detection cavity due to the expansion of the flow channel cross section, the compensation airflow can provide reverse support for the deviated particles to ensure that the particles do not deviate from the center focus of the illumination beam, thereby ensuring the luminous effect of the scattered light.

[0008] In one embodiment of this application, the other end of the light input channel extends along the X-axis and is equipped with a point light source device; the other end of the detection channel extends along the X-axis and is equipped with a photoelectric sensor; the other end of the reflection channel extends along the Y-axis and is equipped with a reflection component; and the other end of the main gas path channel extends along the Z-axis and is connected to a gas supply device.

[0009] By adopting the above scheme, the point light source device, photoelectric sensor and main air passage are arranged in three directions, making use of three-dimensional space to reduce the size of the device. At the same time, the main air passage extends along the Z-axis, ensuring that the airflow is vertical or stable in the direction of gravity, reducing airflow turbulence caused by pipe bends, and ensuring the stability of particulate matter when passing through the detection area.

[0010] In one embodiment of this application, the connecting block has an incident light cone-shaped hole inside, the irradiation cavity is connected to the incident light channel through the incident light cone-shaped hole, the connecting block has a reflective cone-shaped hole inside, the irradiation cavity is connected to the reflective channel through the reflective cone-shaped hole, and the connecting block has a columnar vent hole inside, the columnar vent hole is coaxial with the main air passage, and the irradiation cavity is connected to the main air passage through the columnar vent hole.

[0011] By adopting the above scheme, the light-incident cone-shaped aperture can eliminate stray light from the edge of the light source, ensuring that only the collimated central beam enters the irradiation cavity. The reflective cone-shaped aperture limits the field of view and shields the background reflection noise in the non-signal area of ​​the irradiation cavity wall. At the same time, the columnar vent hole is coaxially set with the main air path, ensuring that the airflow to be detected maintains a stable laminar flow state when passing through the optical center, avoiding eddies caused by abrupt changes in the flow channel cross-section, thereby preventing particles from lingering in the detection area or being counted repeatedly, and improving the accuracy of the detection data.

[0012] In one embodiment of this application, the connecting block has a connecting surface inside, and the connecting surface and the reflecting surface enclose each other to form the irradiation cavity. The reflecting surface is an optical wall with a partially elliptical cross-section. The ellipse in which the reflecting surface is located is defined as a connecting ellipse. Two foci located on the major semi-axis of the connecting ellipse are defined as foci F1 and foci F2, respectively. The connecting surface is a wall with a partially circular cross-section, and the circle in which the connecting surface is located is defined as a connecting circle. The center of the connecting circle coincides with the position of the focal point F1 and is located on the central axis of the main air passage.

[0013] By adopting the above scheme and constructing an asymmetric irradiation cavity with an upper circle and a lower ellipse, the optical properties of the ellipse are utilized to concentrate the back-scattered or large-angle scattered light emitted from the first focal point F1 towards the second focal point F2 after reflection by the reflective surface, thereby improving the light collection efficiency. At the same time, the circular design of the connecting surface ensures the smoothness of the fluid dynamics of the airflow to be detected in the upper part of the irradiation cavity, thereby ensuring the stability of particle movement and improving the intensity of the detected scattered light.

[0014] In one embodiment of this application, a first condenser lens and a second condenser lens are further included. The first condenser lens is mounted inside one end of the light-incident channel, and the focal point of the first condenser lens coincides with the focal point F1. The second condenser lens is mounted inside one end of the reflection channel, and the focal point F2 is located on the light-incident surface of the second condenser lens.

[0015] By adopting the above scheme, the first condenser lens concentrates the illumination beam at point F1, thereby enhancing the intensity of scattered light when the illumination beam shines on the particle. At the same time, the incident light surface of the second condenser lens is aligned with point F2, which can efficiently capture the divergent beam from the elliptical reflector, reshape it, and refocus it into the subsequent optical path. This dual-focal conjugate matching design ensures that the energy transmission efficiency of the optical system is maximized and reduces the energy loss of the optical signal during transmission.

[0016] In one embodiment of this application, a compensation gas passage is further included. The compensation gas passage is configured to be connected at one end to the irradiation cavity and at the other end to the static pressure chamber. The static pressure chamber is provided with compensation gas. The compensation gas passage is configured to be driven by the negative pressure of the airflow to be detected to draw in compensation gas from the static pressure chamber to compensate for the gas pressure at the reflective surface inside the irradiation cavity.

[0017] By adopting the above scheme, when the airflow passes through the main air passage, a negative pressure is generated inside the reflective cavity. This negative pressure directly drives the external compensation gas to be automatically drawn into the reflective cavity from the static pressure chamber through the compensation air passage to compensate for the sinking of particles in the irradiation cavity when the negative pressure is generated. No additional power pump is required, the structure is simple and reliable, and the flow rate is adaptively matched with the main airflow speed, realizing the low cost and low power consumption operation of the system.

[0018] In one embodiment of this application, the compensation gas path includes: A uniform flow cavity is formed inside the connecting block and located on the side of the irradiation cavity away from the reflection channel. The uniform flow cavity and the irradiation cavity are connected through an annular air outlet structure. The compensating vent is located on the side of the irradiation cavity away from the reflection channel. Multiple compensating vents are provided, with one end of each vent connected to the static pressure chamber and the other end connected to the uniform flow chamber.

[0019] By adopting the above scheme, the compensating gas is introduced from the bottom of the reflective surface, balancing the low-pressure area at the bottom of the elliptical reflective surface. The lifting force generated by the pressure balance effectively compensates for the particle settling phenomenon caused by the asymmetrical flow channel. At the same time, before entering the irradiation chamber, the airflow passes through the uniform flow chamber to uniformly balance the jet, thereby smoothing the compensating gas. Ultimately, it can form a flowing gas laminar flow on the reflective surface, isolating the dust in the airflow to be tested from the reflective surface, thus achieving maintenance-free self-cleaning of the reflective surface and extending the service life of the equipment.

[0020] In one embodiment of this application, the annular air outlet structure includes: annular air outlet holes, two of which are provided, both of which are coaxial with the major axis of the connecting ellipse and are disposed on the reflective surface. The annular air outlet holes include three arc-shaped channels with a partially circular shape, which surround each other to form the annular air outlet holes. The two sides of the arc-shaped channels are respectively connected to the irradiation cavity and the uniform flow cavity.

[0021] By adopting the above scheme and using the annular air outlet method, the compensation gas can not only be drawn into the airflow to be tested under the negative pressure of the irradiation cavity, but the two annular air outlets can also ensure that the compensation gas in the inner ring is driven by the gas ejected from the annular air outlet in the outer ring as it climbs along the curved surface, thereby supplementing its kinetic energy and further reducing the occurrence of turbulence in the detection cavity due to insufficient kinetic energy of the compensation gas.

[0022] In one embodiment of this application, a light trap is also included. The light trap is assembled inside the main body shell and located on the side of the irradiation cavity opposite to the light inlet channel. An absorption through hole is provided inside the connecting block on the side near the light trap. The illumination beam passes through the absorption through hole and enters the light trap to absorb the illumination beam and part of the scattered light emitted by the particles.

[0023] By adopting the above scheme, a dark field detection environment was constructed by setting up light traps. The light traps are located at the end of the optical path and can absorb the strong illumination beams and small-angle forward scattered light remaining after passing through the airflow. This prevents these high-energy light rays from undergoing diffuse reflection inside the cavity and eventually entering the detection channel, reducing the background noise of the system. This enables the sensor to identify the weak scattered signals generated by tiny particles and improves the signal-to-noise ratio.

[0024] In one embodiment of this application, the reflective component includes: A mounting base, which is fitted inside the other end of the reflection channel; A reflector is mounted on the mounting base and is tilted at 45° along the incident light direction.

[0025] By adopting the above scheme and setting a 45-degree reflector, the scattered light signal transmitted along the Y-axis is refracted into the detection channel distributed along the X-axis, which enables the entire optical path system to be arranged in a flat plane, facilitating the overall assembly of the PCB circuit board and the subsequent connection of signal processing circuits.

[0026] In summary, this application includes at least one of the following beneficial technical effects: by utilizing the geometric focusing characteristics of the elliptical reflector, the backscattered light and large-angle sidescattered light that are wasted in traditional detection methods are effectively recovered and superimposed with the forward / sidescattered light at the second focal point. Without increasing the power and energy consumption of the light source, the light energy input of the photoelectric sensor is significantly improved by expanding the receiving solid angle of the effective scattered light, thereby enhancing the detection sensitivity and resolution of the device for small particles.

[0027] By setting up a gas path compensation channel connected to the detection chamber, the high-speed flow of the air to be tested generates a negative pressure effect, which can automatically drive the compensation gas to be drawn in from the bottom of the reflective surface, forming a flowing clean gas film on the elliptical reflective surface. On the one hand, this balances the low-pressure area at the bottom of the asymmetric flow channel, reducing the risk of particle settling and eccentricity. On the other hand, this gas film acts as a physical barrier, effectively blocking the contact between pollutants in the air to be tested and the optical reflective surface, reducing the occurrence of reflectivity attenuation caused by dust accumulation, and realizing the self-cleaning and long-life operation of the device.

[0028] By constructing a dark field detection environment, the conical structure effectively cuts off the non-collimated light rays at the edge of the light source and the secondary diffuse stray light inside the cavity, ensuring that the detection channel only receives the effective scattered signal emitted by the particles. By utilizing the synergistic effect of optical path spatial filtering and gas path laminar flow shaping, the background noise of the system is reduced, thereby improving the signal-to-noise ratio.

[0029] By setting up an annular air outlet structure and connecting two coaxial annular air outlets to the uniform flow cavity, the compensation gas entering the detection cavity can enter at a low speed and smoothly in a laminar flow. This ensures that the compensation gas can adaptively compensate for the air pressure according to the flow rate of the airflow to be detected, and also ensures that the compensation gas will not change abruptly due to the increase in the flow rate of the airflow to be detected. At the same time, the compensation gas located on the outer ring along the flow direction of the airflow to be detected can provide kinetic energy to the compensation gas located on the inner ring, thereby avoiding the disruption of the fluid morphology of the airflow to be detected and reducing the occurrence of turbulence. Attached Figure Description

[0030] Figure 1 This is a three-dimensional view of a particle scattering light detection structure based on Mie scattering theory provided in the embodiments of this application; Figure 2This is a frontal cross-sectional view of a particle scattering light detection structure based on Mie scattering theory provided in the embodiments of this application; Figure 3 This is a frontal cross-sectional view of a connected block of a particle scattering light detection structure based on Mie scattering theory provided in an embodiment of this application; Figure 4 This is a schematic diagram of the optical path of a connected block of a particle scattering light detection structure based on Mie scattering theory provided in an embodiment of this application; Figure 5 This is a top cross-sectional view of the main gas path of a particle scattering light detection structure based on Mie scattering theory provided in the embodiments of this application; Figure 6 This is a side cross-sectional view of the main gas path of a particle scattering light detection structure based on Mie scattering theory provided in the embodiments of this application; Figure 7 This is a bottom cross-sectional view of a ring-shaped gas outlet structure for particle scattering light detection based on Mie scattering theory provided in an embodiment of this application.

[0031] Explanation of reference numerals in the attached drawings: 1. Main body shell; 11. Light entrance channel; 12. Detection channel; 13. Reflection channel; 14. Point light source device; 15. Photoelectric sensor; 16. Reflection component; 161. Fixing base; 162. Reflector; 2. Connecting block; 21. Irradiation cavity; 22. Reflecting surface; 23. Light entrance cone-shaped hole; 24. Reflection cone-shaped hole; 25. Columnar vent hole; 26. Connecting surface; 27. Absorption through hole; 3. Air inlet pipe; 31. Main air passage; 4. First condensing lens; 5. Second condensing lens; 6. Compensating air passage; 61. Uniform flow cavity; 62. Annular air outlet structure; 621. Annular air outlet; 6211. Arc-shaped channel; 63. Compensating air hole; 7. Dustproof component; 71. Assembly ring; 72. Dustproof net; 8. Light trap. Detailed Implementation

[0032] The following is in conjunction with the appendix Figures 1-7 This application provides a more detailed description of a particle scattering light detection structure based on Mie scattering theory.

[0033] The particle scattering light detection structure based on Mie scattering theory provided in this application embodiment includes: a main shell 1.

[0034] Please see Figure 1 , Figure 2 and Figure 3The main body shell 1 has a connecting block 2 inside, and an irradiation cavity 21 is formed inside the connecting block 2. The main body shell 1 also has an entrance light channel 11 and a detection channel 12 inside, which are spaced apart and parallel to each other. An air inlet pipe 3 is provided outside the main body shell 1, and a main air passage 31 extending along its length is provided inside the air inlet pipe 3. A reflection channel 13 is also formed inside the main body shell 1 between the entrance light channel 11 and the detection channel 12. One end of the entrance light channel 11, the reflection channel 13, and the main air passage 31 are all connected to the irradiation cavity 21. One end of the detection channel 12 is connected to the other end of the reflection channel 13. A reflection component 16 is provided inside the other end of the reflection channel 13. The main air passage 31 is configured to provide the airflow to be detected, allowing the airflow to pass through the irradiation cavity 21. The entrance light channel 11 is configured to provide an illumination beam and irradiate the airflow in the irradiation cavity 21. The airflow is detected so that particles in the airflow emit scattered light. The detection channel 12 is configured to receive and detect the scattered light from the particles. The connecting block 2 has a reflective surface 22 inside. The reflective surface 22 is located on the inner wall of the irradiation cavity 21 on the side away from the reflection channel 13. The bottom inner wall of the reflective surface 22 has a compensation gas path channel 6 that communicates with the irradiation cavity 21. The irradiation cavity 21 is configured to: use the reflective surface 22 to reflect part of the scattered light emitted by the particles in the direction away from the reflection channel 13 into the reflection channel 13; and use the compensation gas path channel 6 to compensate for the gas pressure inside the irradiation cavity 21 at the reflective surface 22. By setting an irradiation cavity 21 with a reflection function inside the connecting block 2, the reflective surface 22 can collect and reflect the scattered light that originally dispersed in the opposite or downward direction, increasing the number of effective photons received by the photoelectric sensor 15, thereby improving the detection sensitivity, and also ensuring that the particles in the airflow to be detected do not shift.

[0035] Please see Figure 2 The other end of the light-inlet channel 11 extends along the X-axis and is equipped with a point light source device 14. The other end of the detection channel 12 extends along the X-axis and is equipped with a photoelectric sensor 15. The other end of the reflection channel 13 extends along the Y-axis and is equipped with a reflection component 16. The other end of the main air passage 31 extends along the Z-axis and is connected to the air supply device. By arranging the point light source device 14, the photoelectric sensor 15, and the main air passage 31 in three directions, the three-dimensional space is utilized to the maximum extent and the size of the device is reduced.

[0036] In this embodiment, the point light source device 14 can be a laser generator.

[0037] Please see Figure 3The connecting block 2 has an entrance conical hole 23 inside, and the irradiation cavity 21 is connected to the entrance channel 11 through the entrance conical hole 23. The entrance conical hole 23 can remove stray light from the edge of the light source and ensure the collimation of the light beam entering the irradiation cavity 21. The connecting block 2 has a reflection conical hole 24 inside, and the irradiation cavity 21 is connected to the reflection channel 13 through the reflection conical hole 24. The connecting block 2 has a columnar vent hole 25 inside, and the columnar vent hole 25 is coaxial with the main air passage 31. The irradiation cavity 21 is connected to the main air passage 31 through the columnar vent hole 25.

[0038] Please continue reading. Figure 3 The connecting block 2 has a connecting surface 26 inside. The connecting surface 26 and the reflecting surface 22 enclose each other to form the irradiation cavity 21. The reflecting surface 22 is an optical wall with a partially elliptical cross-section. The ellipse containing the reflecting surface 22 is defined as the connecting ellipse. The two foci located on the major semi-axis of the connecting ellipse are defined as foci F1 and foci F2, respectively. The connecting surface 26 is a wall with a partially circular cross-section. The circle containing the connecting surface 26 is defined as the connecting circle. The center of the connecting circle coincides with the position of foci F1 and is located on the central axis of the main air passage 31. By constructing an asymmetrical irradiation cavity 21 with an upper circle and a lower ellipse, the optical properties of the ellipse are used to concentrate the back-scattered or large-angle scattered light emitted from the first foci F1 towards the second foci F2 after reflection by the reflecting surface 22, thereby improving the light collection efficiency.

[0039] In this embodiment, the reflecting surface 22 may be an optical reflecting mirror with a partially elliptical shape.

[0040] Please see Figure 3 and Figure 4 It also includes a first condenser lens 4 and a second condenser lens 5. The first condenser lens 4 is mounted inside one end of the light-incident channel 11, and the focal point of the first condenser lens 4 coincides with the focal point F1. The second condenser lens 5 is mounted inside one end of the reflection channel 13, and the focal point F2 is located on the light-incident surface of the second condenser lens 5. The first condenser lens 4 concentrates the illumination beam at point F1, thereby enhancing the intensity of the scattered light when the illumination beam shines on the particles. At the same time, the light-incident surface of the second condenser lens 5 is aligned with point F2, which can efficiently capture the divergent beam that converges from the elliptical reflector 22, ensuring the energy transmission efficiency of the optical system.

[0041] Please continue reading. Figure 3 and Figure 6The compensating gas passage 6 is configured such that one end is connected to the irradiation chamber 21 and the other end is connected to the static pressure chamber. The static pressure chamber contains compensating gas. The compensating gas passage 6 is configured to be driven by the negative pressure of the airflow to be detected, drawing in compensating gas from the static pressure chamber to compensate for the gas pressure at the reflective surface 22 inside the irradiation chamber 21. When the airflow passes through the main gas passage 31, a negative pressure is generated inside the reflective chamber. This negative pressure drives the external compensating gas to be automatically drawn into the reflective chamber from the static pressure chamber via the compensating gas passage 6, lifting the particles sinking in the irradiation chamber 21. No additional power pump is required, and the self-absorbed flow rate is adaptively matched to the main airflow velocity. The compensating gas passage 6 includes: a uniform flow chamber 61, an annular air outlet structure 62, and a compensating air hole 63. The flow cavity 61 is located inside the connecting block 2 and on the side of the irradiation cavity 21 away from the reflection channel 13. The uniform flow cavity 61 is connected to the irradiation cavity 21 through the annular air outlet structure 62. The compensation air hole 63 is located on the side of the irradiation cavity 21 away from the reflection channel 13. Multiple compensation air holes 63 are provided. One end of each compensation air hole 63 is connected to the static pressure chamber, and the other end is connected to the uniform flow cavity 61. The compensation gas is introduced from the bottom of the reflective surface 22, which balances the low pressure area at the bottom of the elliptical reflective surface 22. The lifting force generated by the air pressure balance effectively compensates for the particle settling phenomenon caused by the asymmetric flow channel. At the same time, by setting the annular air outlet structure 62, a layer of flowing gas laminar flow can be formed on the reflective surface 22 to perform self-cleaning of the reflective surface 22.

[0042] In this embodiment, the air inlet pipe 3 has a necking structure with a gradually decreasing diameter at one end near the connecting block 2. Based on the Venturi effect, the gas to be detected in the main air passage flows through the irradiation chamber at a higher velocity, resulting in a lower pressure relative to the static pressure chamber. As a result, the gas automatically draws in compensation gas under the pressure difference with the static pressure chamber.

[0043] In this embodiment, the static pressure chamber is located above the compensation gas passage 6 and is connected to the compensation gas passage 6 through a capillary tube. The static pressure chamber is a hollow box-shaped component that is connected to the atmosphere. Please see Figure 1 and Figure 3 It also includes a dustproof component 7, which includes an assembly ring 71 and a dustproof net 72. The assembly ring 71 is assembled on the outside of the main body shell 1, and the dustproof net 72 is assembled on the inner wall of the assembly ring 71 and located above the compensation air hole 63. The dustproof net 72 further filters the compensation gas before it enters the static pressure chamber or the compensation air passage 6, thereby ensuring the cleanliness of the reflective surface 22 and maintaining the high reflectivity of the reflective surface 22.

[0044] Please see Figure 7The annular air outlet structure 62 includes an annular air outlet 621. Two annular air outlets 621 are provided, both of which are coaxial with the major axis of the connecting ellipse and are disposed on the reflective surface 22. Each annular air outlet 621 includes three arc-shaped channels 6211 with a partially circular shape. The three arc-shaped channels 6211 surround each other to form the annular air outlet 621. The two sides of the arc-shaped channels 6211 are respectively connected to the irradiation cavity 21 and the uniform flow cavity 61. By providing two annular air outlets 621 coaxial with the connecting ellipse on the elliptical reflective surface 22, the turbulence generated when the compensating airflow enters the irradiation cavity 21 can be reduced.

[0045] Please see Figure 3 , Figure 4 and Figure 5 It also includes a light trap 8, which is assembled inside the main body shell 1 and located on the side of the irradiation cavity 21 away from the light entrance channel 11. The connecting block 2 has an absorption through hole 27 on the side near the light trap 8. The connecting surface 26 and the wall of the absorption through hole 27 are coated with an optical absorption coating to reduce background noise from stray light and improve the signal-to-noise ratio. The illumination beam enters the light trap 8 after passing through the absorption through hole 27 to absorb the illumination beam and some of the scattered light emitted by the particles. By setting the light trap 8, the light trap 8 can absorb the strong illumination beam remaining after passing through the airflow and the forward scattered light at a small angle, reducing the background noise of the system and significantly improving the signal-to-noise ratio.

[0046] Please see Figure 2 The reflective component 16 includes a fixed base 161 and a reflector 162. The fixed base 161 is mounted inside the other end of the reflective channel 13. The reflector 162 is mounted on the fixed base 161 and is inclined at 45° along the incident light direction. By setting the 45-degree reflector 162, the scattered light signal transmitted along the Y-axis direction is refracted into the detection channel 12 distributed along the X-axis, which enables the entire optical path system to be arranged in a flat plane.

[0047] In summary, the point light source device 14 emits an illumination beam, while the air supply device blows the airflow to be detected into the main air passage 31. Since the central axis of the main air passage 31 is coaxial with the connecting circle where the connecting surface 26 is located in the reflective cavity, and the focal point of the first condensing lens 4 and the center of the connecting circle coincide with the focal point F1, the illumination beam can accurately illuminate the airflow to be detected. After the particles in the airflow to be detected are illuminated, they emit spherical three-dimensional scattered light. Among them, part of the scattered light incident along the direction of the reflective channel 13 and part of the scattered light directed towards the reflective surface 22 can accurately be directed towards the second condensing lens 5. After the scattered light passes through the second condensing lens 5 and the reflective component 16 in sequence, it is received by the photoelectric sensor 15. By collecting the bidirectional scattered light, the input of the optical signal is increased, thereby improving the signal-to-noise ratio of the output signal of the device and improving the detection accuracy.

[0048] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A particle scattering light detection structure based on Mie scattering theory, characterized in that, include: The main body shell (1) has a connecting block (2) inside, and an irradiation cavity (21) is opened inside the connecting block (2). The main body shell (1) has an entrance light channel (11) and a detection channel (12) inside. The entrance light channel (11) and the detection channel (12) are spaced apart from each other and arranged in parallel. The main body shell (1) has an air inlet pipe (3) outside. The air inlet pipe (3) has a main air passage (31) extending along its own length direction inside. The main body shell (1) also has a reflection channel (13) between the entrance light channel (11) and the detection channel (12) inside. One end of the entrance light channel (11), the reflection channel (13) and the main air passage (31) are all connected to the irradiation cavity (21). One end of the detection channel (12) is connected to the other end of the reflection channel (13). The other end of the reflection channel (13) has a reflection component (16). The main gas path channel (31) is configured to provide the airflow to be detected and allow the airflow to pass through the irradiation cavity (21). The light entrance channel (11) is configured to provide an illumination beam and irradiate the airflow to be detected in the irradiation cavity (21), causing the particles in the airflow to emit scattered light. The detection channel (12) is configured to receive the scattered light from the particles and perform detection. The connecting block (2) has a reflective surface (22) inside. The reflective surface (22) is located on the inner wall of the irradiation cavity (21) on the side away from the reflective channel (13). The bottom inner wall of the reflective surface (22) has a compensation gas path channel (6) communicating with the irradiation cavity (21). The irradiation cavity (21) is configured as follows: The reflective surface (22) is used to reflect part of the scattered light emitted by the particles in the direction away from the reflection channel (13) into the reflection channel (13); The gas pressure inside the irradiation cavity (21) at the reflective surface (22) is compensated by the compensation gas path channel (6).

2. The particle scattering light detection structure based on Mie scattering theory according to claim 1, characterized in that: The other end of the light inlet channel (11) extends along the X-axis and is equipped with a point light source device (14). The other end of the detection channel (12) extends along the X-axis and is equipped with a photoelectric sensor (15). The other end of the reflection channel (13) extends along the Y-axis and is equipped with the reflection component (16). The other end of the main gas path channel (31) extends along the Z-axis and is connected to the gas supply device.

3. The particle scattering light detection structure based on Mie scattering theory according to claim 2, characterized in that: The connecting block (2) has an entrance cone-shaped hole (23) inside, and the irradiation cavity (21) is connected to the entrance channel (11) through the entrance cone-shaped hole (23). The connecting block (2) has a reflection cone-shaped hole (24) inside, and the irradiation cavity (21) is connected to the reflection channel (13) through the reflection cone-shaped hole (24). The connecting block (2) has a columnar vent hole (25) inside, and the columnar vent hole (25) is coaxial with the main air passage (31). The irradiation cavity (21) is connected to the main air passage (31) through the columnar vent hole (25).

4. The particle scattering light detection structure based on Mie scattering theory according to claim 3, characterized in that: The connecting block (2) has a connecting surface (26) inside. The connecting surface (26) and the reflecting surface (22) enclose each other to form the irradiation cavity (21). The reflecting surface (22) is an optical wall with a partially elliptical cross-section. The ellipse in which the reflecting surface (22) is located is defined as the connecting ellipse. The two foci located on the major semi-axis of the connecting ellipse are defined as foci F1 and foci F2, respectively. The connecting surface (26) is a wall with a partially circular cross-section. The circle in which the connecting surface (26) is located is defined as the connecting circle. The center of the connecting circle coincides with the position of the focal point F1 and is located on the central axis of the main air passage (31).

5. The particle scattering light detection structure based on Mie scattering theory according to claim 4, characterized in that: It also includes a first condenser lens (4) and a second condenser lens (5), wherein the first condenser lens (4) is mounted inside one end of the light entrance channel (11), and the focal point of the first condenser lens (4) coincides with the focal point F1; The second condenser lens (5) is mounted inside one end of the reflection channel (13), and the focal point F2 is located on the light-incident surface of the second condenser lens (5).

6. The particle scattering light detection structure based on Mie scattering theory according to claim 4, characterized in that: The compensation gas passage (6) is configured to be connected to the irradiation chamber (21) at one end and to the static pressure chamber at the other end. The static pressure chamber is provided with compensation gas. The compensation gas passage (6) is configured to be driven by the negative pressure of the airflow to be detected to draw in compensation gas from the static pressure chamber in order to compensate for the gas pressure inside the irradiation chamber (21) at the reflective surface (22).

7. The particle scattering light detection structure based on Mie scattering theory according to claim 6, characterized in that, The compensation gas path (6) includes: A uniform flow cavity (61) is formed inside the connecting block (2) and located on the side of the irradiation cavity (21) away from the reflection channel (13). The uniform flow cavity (61) and the irradiation cavity (21) are connected by an annular air outlet structure (62). Compensating vents (63) are located on the side of the irradiation cavity (21) away from the reflection channel (13). Multiple compensating vents (63) are provided. One end of each compensating vent (63) is connected to the static pressure chamber, and the other end is connected to the uniform flow chamber (61).

8. The particle scattering light detection structure based on Mie scattering theory according to claim 7, characterized in that, The annular air outlet structure (62) includes an annular air outlet (621), two of which are provided. Both annular air outlets (621) are coaxial with the major axis of the connecting ellipse and are located on the reflective surface (22). The annular air outlet (621) includes three arc-shaped channels (6211) with a partially circular shape. The three arc-shaped channels (6211) surround each other to form the annular air outlet (621). The two sides of the arc-shaped channels (6211) are respectively connected to the irradiation cavity (21) and the uniform flow cavity (61).

9. A particle scattering light detection structure based on Mie scattering theory according to claim 4, characterized in that: It also includes a light trap (8), which is assembled inside the main body shell (1) and located on the side of the irradiation cavity (21) away from the light inlet channel (11). The connecting block (2) has an absorption through hole (27) on the side near the light trap (8). The illumination beam enters the light trap (8) after passing through the absorption through hole (27) to absorb the illumination beam and part of the scattered light emitted by the particles.

10. A particle scattering light detection structure based on Mie scattering theory according to claim 1, characterized in that, The reflective component (16) includes: A mounting base (161) is fitted inside the other end of the reflective channel (13); A reflector (162) is mounted on the mounting base (161) and is inclined at 45° along the incident light direction.

Images