A particle counting sensor

Abstract

This invention provides a particle counting sensor, including a light source emitting a light beam, an air path assembly for the flow of air to be measured, wherein the light beam and the airflow intersect to form a working optical region, and further including a photodetector and a scattered light collection assembly; surrounding the light beam, the scattered light collection assembly includes a first scattered light collection structure and a second scattered light collection structure respectively disposed on opposite sides of the working optical region; the second scattered light collection structure, the working optical region, the first scattered light collection structure, and the photodetector are arranged sequentially; the first scattered light collection structure has a light reflecting surface inside, which surrounds to form a first reflecting cavity; the first scattered light collection structure has a first light inlet and a first light outlet for communicating with the outside of the first reflecting cavity, the first light inlet facing the working optical region, and the first light outlet being combined with the photodetector; the second scattered light collection structure has a third reflecting surface facing the working optical region, and light from at least a portion of the third reflecting surface is reflected into the first reflecting cavity.

Description

Technical Field

[0001] This invention relates to the field of particle counter technology, and more specifically to a particle counting sensor. Background Technology

[0002] Particle counting sensors typically consist of a light source, an optical module, a gas path module, and a photodetector. The light beam emitted by the light source forms a uniform light field after passing through the optical module. The gas path module delivers the airflow to be detected through the light field, forming the optical working area. Particles in the airflow are illuminated and emit scattered light. This scattered light is received by a photodetector positioned on one side of the optical working area and converted into a photocurrent. The photocurrent is then amplified and processed by a circuit to become a voltage pulse signal. By comparing different voltage pulse signals, the particle size can be determined. The more scattered light the photodetector receives, the higher the accuracy of particle resolution. Current photodetector configurations limit their ability to receive scattered light projected in their direction. To enable the photodetector to receive more scattered light, existing technologies typically place a hemispherical mirror on the side of the optical working area opposite the photodetector. This hemispherical mirror collects the scattered light and reflects it back to the photodetector. Even with this method, some scattered light cannot be collected. Furthermore, due to the divergence angle of the laser, even after the beam is shaped, stray light inevitably exists during the beam propagation process, affecting the accurate counting and resolution of particles by the particle counter. After being received by the photodetector, the stray light affects the particle size resolution and the accurate counting of particles.

[0003] It is evident that there is a need in the field to improve the scattered light receiving structure of particle counting sensors in order to increase the amount of scattered light collected by photodetectors while reducing the influence of stray light. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a particle counting sensor, wherein the scattered light receiving structure is improved to increase the amount of scattered light collected by the photodetector.

[0005] To achieve the above objectives, the present invention provides a particle counting sensor, including a light source emitting a light beam, a gas path assembly for driving the flow of the airflow to be measured, wherein the light beam and the airflow intersect to form a working optical region, and further including a photodetector and a scattered light collecting assembly; surrounding the light beam, the scattered light collecting assembly includes a first scattered light collecting structure and a second scattered light collecting structure respectively disposed on opposite sides of the working optical region; the second scattered light collecting structure, the working optical region, the first scattered light collecting structure, and the photodetector are arranged sequentially; the first scattered light collecting structure has a light reflecting surface inside, which surrounds to form a first reflecting cavity; the first scattered light collecting structure has a first light inlet and a first light outlet communicating with the first reflecting cavity to the outside, the first light inlet facing the working optical region, and the first light outlet being combined with the photodetector; the second scattered light collecting structure has a third reflecting surface facing the working optical region, and light reflected from at least a portion of the third reflecting surface enters the first reflecting cavity through the first light inlet.

[0006] Preferably, the second scattered light collection structure includes a fourth reflective surface facing away from the light working area and a second light inlet facing the light working area, wherein the third reflective surface and the fourth reflective surface are combined to form a second reflective cavity, and the third reflective surface and the fourth reflective surface are the internal surfaces of the second scattered light collection.

[0007] Preferably, the first light inlet and the second light inlet are located on opposite sides of the optical working area, and along the projection line direction of the maximum orthographic projection area of ​​the first light inlet, the orthographic projections of the first light inlet, the second light inlet, and the optical working area have the maximum overlapping projection areas.

[0008] Preferably, the edge of the orthographic projection of the optical working area does not exceed the edges of the orthographic projections of the first light inlet and the second light inlet.

[0009] Preferably, the optical working area is spaced apart from the first light inlet and the second light inlet, and the minimum distance between the optical working area and the first light inlet and the second light inlet is 1-10mm.

[0010] Preferably, the region of the outer surface of the first light-scattering collection structure facing the light beam is a first light-absorbing surface; the region of the outer surface of the second light-scattering collection structure facing the light beam is a second light-absorbing surface.

[0011] Preferably, the first reflective cavity has two opposing reflective surfaces, the two reflective surfaces are closely connected at their peripheries, and the two reflective surfaces respectively surround the first light inlet and the first light outlet.

[0012] Preferably, the fourth reflective surface surrounds the second light inlet.

[0013] Preferably, the first scattered light collection structure includes a first reflector and a second reflector. The side of the first reflector facing away from the light working area has a first reflective surface, and the side of the second reflector facing the light working area has a second reflective surface. The peripheries of the first reflector and the second reflector are closely connected to form the first reflective cavity. The first light inlet is located on the first reflector, and the first light outlet is located on the second reflector.

[0014] Preferably, the second scattered light collection structure includes a third reflector, the side of the third reflector facing the light working area having the third reflective surface; the second scattered light collection structure includes a fourth reflector, the side of the fourth reflector away from the light working area having the fourth reflective surface, the fourth reflector and the periphery of the third reflector being closely connected to form a second reflective cavity, and the fourth reflector having a second light inlet.

[0015] Compared with the prior art, the advantages of the particle counting sensor disclosed in this invention are as follows: the particle scattering light receiving structure of the particle counting sensor can increase the amount of scattered light collected by the photodetector, thereby making the particle counting sensor more accurate; the particle scattering light receiving structure can filter and absorb some stray light, which helps to reduce noise and improve the accuracy of the particle counting sensor. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] like Figure 1 The diagram shown is a structural schematic of a particle counting sensor according to the present invention.

[0018] like Figure 2 The diagram shown is a schematic representation of the gas path assembly of a particle counting sensor according to the present invention.

[0019] like Figure 3 The diagram shown is a structural schematic of a variant of the particle counting sensor of the present invention. Detailed Implementation

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] like Figure 1 and Figure 2 As shown, this application discloses a particle counting sensor including a light source 1 emitting a light beam 21, an airflow path assembly for driving the flow of the air to be measured, and the light beam 21 intersecting with the airflow to form a working optical region 5. The particle counting sensor also includes a photodetector 6 and a scattered light collecting assembly. Surrounding the light beam, the scattered light collecting assembly includes a first scattered light collecting structure 7 and a second scattered light collecting structure 8 respectively disposed on opposite sides of the working optical region. The second scattered light collecting structure 8, the working optical region 5, the first scattered light collecting structure 7, and the photodetector 6 are arranged sequentially. The first scattered light collecting structure 7 has a light reflecting surface inside, which surrounds and forms a first reflecting cavity 70. The first scattered light collecting structure 7 has a first light inlet 701 and a first light outlet 702 for communicating with the outside of the first reflecting cavity 70. The first light inlet 701 faces the working optical region 5, and the first light outlet 702 is combined with the photodetector 6. The second scattered light collecting structure 8 has a third reflecting surface facing the working optical region 5, and light reflected from at least a portion of the third reflecting surface enters the first reflecting cavity 70 through the first light inlet 701. Part of the scattered light 22 enters the first reflecting cavity 70 through the first light inlet 701. Some of this scattered light directly enters the photodetector 6, where it is received and converted into an electrical signal. The remaining scattered light, after entering the first reflecting cavity 70, undergoes one or more reflections by the light reflecting surface before entering the photodetector 7. Part of the scattered light 23 enters the third reflecting surface and, after reflection, enters the first reflecting cavity 70. The scattered light collection assembly can collect the scattered light from both sides of the optical working area 5, thereby increasing the amount of scattered light collected by the photodetector 6.

[0022] In addition, the particle counting sensor also includes an optical shaping component 3 and an optical trap 4. The light source 1 emits a light beam 21. After being compressed and collimated by the optical shaping component 3, the light beam 21 reaches the airflow flowing in the air path component to form an optical working area 5. After passing through the optical working area 5, the light beam 21 reaches the optical trap 4 and is received by it. The gas path assembly includes an inlet 91 and an outlet 92. Outside the beam propagation path, the inlet 91 and outlet 92 are located on opposite sides of the optical working area 5. The inlet 91 has an inlet 911 facing the optical working area 5, and the outlet 92 has an outlet 921 facing the optical working area 5. The inlet 91 delivers a gas flow 90 to be tested to the outlet 92. The beam 21 and the gas flow 90 intersect in the optical working area 5. Particles in the gas flow 90 enter the optical working area 5 and generate scattered light. In the prior art, the size of the optical working area 5 is limited by the laser beam and the gas flow 90 flowing through the inlet 911 and outlet 921 in the gas path assembly. The beam spot cross-sectional size in the optical working area is typically on the order of millimeters. The first scattered light collection structure 7 and the second scattered light collection structure 8 are arranged in a non-contact manner with the gas flow 90 and the beam 21.

[0023] The preferred second light-scattering collection structure 8 includes a fourth reflective surface facing away from the light working area and a second light inlet 801 facing the light working area. The third reflective surface and the fourth reflective surface are combined to form a second reflective cavity 80. The third reflective surface and the fourth reflective surface are the internal surfaces of the second light-scattering collection structure 8.

[0024] Preferably, the first light inlet 701 and the second light inlet 801 are located on both sides of the optical working area 5, and along the projection line direction of the maximum orthographic projection area of ​​the first light inlet 701, the orthographic projection of the first light inlet 701, the orthographic projection of the second light inlet 801 and the orthographic projection of the optical working area 5 have the maximum overlapping projection area.

[0025] Preferably, the edge of the orthographic projection of the optical working area 5 does not exceed the edge of the orthographic projection of the first light inlet 701 and the second light inlet 801, so as to ensure that the scattered light from the optical working area 5 is incident on the first reflective cavity 70 and the second reflective cavity 80 as much as possible.

[0026] Preferably, the first scattered light collecting structure 7 and the second scattered light collecting structure 8 are positioned infinitely close to the light beam 21 without contacting it. Alternatively, the optical working area 5 is spaced apart from the first light inlet 701 and the second light inlet 801, with a minimum distance of 1-10 mm. Examples include 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.8 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 5 mm, 7 mm, and 9 mm. A minimum distance of 1.2 to 5 mm is preferred. The minimum distances between the optical working area 5 and the first light inlet 701 and between the optical working area 5 and the second light inlet 801 can be the same or different.

[0027] Preferably, the maximum diameter of the maximum orthographic projection area of ​​the first light inlet 701 is 1 to 2 times the maximum diameter of the orthographic projection area of ​​the optical working area 5 along the projection line direction of the maximum orthographic projection area of ​​the first light inlet 701, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.81, or 1.9 times. The maximum diameter of the maximum orthographic projection area of ​​the second light inlet 801 is 1 to 2 times the maximum diameter of the orthographic projection area of ​​the optical working area 5 along the projection line direction of the maximum orthographic projection area of ​​the second light inlet 801.

[0028] Preferably, the maximum diameter of the orthographic projection area of ​​the second light inlet 801 along the direction of the projection line of the maximum orthographic projection area of ​​the first light inlet 701 is 0.5-3 times the maximum diameter of the maximum orthographic projection area of ​​the first light inlet 701, for example, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.5, 1.7, 1.9, 2.2, 2.5, 2.8 times, etc., preferably 0.8-1.5 times. The third reflecting surface in the second scattered light collecting structure 8 satisfies the geometrical optical object-image relationship with the region of the first light inlet 701 or the region near the first light inlet 701. Furthermore, a collimating or focusing lens is provided at the second light inlet 801. Light reflected from the second reflecting cavity 80 is compressed and collimated by the collimating or focusing lens at the second light inlet 801 before entering the first light inlet 701, increasing the amount of light reflected from the third reflecting surface entering the first light inlet 701. In the second scattered light collection structure 8, the third reflecting surface, after being collimated or focused by the lens, satisfies the geometrical optical object-image relationship with the region of the first light inlet 701 or near the first light inlet 701. The collimating or focusing lens can be selected from spherical mirrors, aspherical mirrors, cylindrical mirrors, or other lenses with optical compression and focusing capabilities; no specific limitations are imposed here.

[0029] When the maximum diameter of the orthographic projection of the second light inlet 801 is slightly greater than or less than or equal to the maximum diameter of the maximum orthographic projection area of ​​the first light inlet 701 (e.g., 0.5-1.1 times), the light emitted from the second scattering light collection structure 8 can be controlled by adjusting the distance between the first and second light inlets to allow the light to enter the first light inlet 701. For example, the minimum distance between the first and second light inlets can be 2-8 mm, such as 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, etc. When the maximum diameter of the orthographic projection of the second light inlet 801 is greater than the maximum diameter of the maximum orthographic projection area of ​​the first light inlet 701, a collimating or focusing lens is provided in the second light inlet 801. The light reflected from the second reflection cavity 80 is compressed and collimated by the collimating or focusing lens at the second light inlet 801 before entering the first light inlet 701. Here, the distance between the first and second light inlets can also be optimized and adjusted.

[0030] As a practical method, when the orthographic projection of the second light inlet 801 does not exceed the edge of the orthographic projection of the first light inlet 701, the distance between the first light inlet and the second light inlet can be controlled, for example, 2-8 mm, so that the light emitted from the second scattering light collection structure 8 enters the first light inlet 701. When the orthographic projection of the second light inlet 801 exceeds the edge of the orthographic projection of the first light inlet 701, the second light inlet 801 is provided with a collimating or focusing lens. The light reflected by the second reflecting cavity 80 is compressed and collimated by the collimating or focusing lens at the second light inlet 801 before entering the first light inlet 701.

[0031] Preferably, the region on the outer surface of the first light-scattering collection structure 7 facing the light beam 21 is the first light-absorbing surface; the region on the outer surface of the second light-scattering collection structure 8 facing the light beam 21 is the second light-absorbing surface. The first and second light-absorbing surfaces can be formed by coating with light-absorbing paint or by blackening treatment, etc., and there is no specific limitation here. The first light-absorbing surface can absorb some stray light and prevent stray light from entering the photodetector 6.

[0032] Preferably, the light-reflecting surface inside the first reflecting cavity 70 includes two opposing reflecting surfaces, which are closely spaced around their peripheries and surround the first light inlet 701 and the first light outlet 702, respectively. Part of the scattered light 22 is incident on one of the reflecting surfaces, and after one or more reflections on the two reflecting surfaces, it is incident on the light-receiving surface of the photodetector 6, thereby increasing the amount of scattered light collected by the photodetector 7.

[0033] Preferably, a fourth reflective surface surrounds the second light inlet 801.

[0034] The opening shapes of the first light inlet 701, the second light inlet 801, and the first light outlet 702 can be regular polygons such as circles, squares, and rectangles, or they can be irregular shapes. The first light outlet 702 is opened based on the photodetector 6 that is connected to it. As an implementable method, the first light inlet 701 and the second light inlet 801 adopt circular openings.

[0035] As an feasible approach, the first light inlet 701 and the second light inlet 801 are coaxial to maximize the reception of light emitted from the second reflective cavity 80 into the first reflective cavity 70; more preferably, the optical working area 5, the first light inlet 701 and the second light inlet 801 are coaxial to maximize the amount of scattered light received.

[0036] Specifically, the first scattered light collecting structure 7 includes a first reflecting mirror 71 and a second reflecting mirror 72. The side of the first reflecting mirror 71 away from the optical working area 5 has a first reflecting surface, and the side of the second reflecting mirror 72 facing the optical working area 5 has a second reflecting surface. The periphery of the first reflecting mirror 71 and the second reflecting mirror 72 is closely connected to form a first reflecting cavity 70. The first reflecting surface and the second reflecting surface are located inside the first reflecting cavity 70 and are arranged opposite to each other. A first light inlet 701 is located on the first reflecting mirror 71, and a first light outlet 702 is located on the second reflecting mirror 72. The side of the first reflecting mirror 72 facing the optical working area 5 is a light absorbing surface. Part of the scattered light 22 enters the first reflecting cavity 70 through the first light inlet 701 and then directly enters the light receiving surface of the photodetector 6. Part of the scattered light 22 enters the second reflecting surface, is reflected to the first reflecting surface, enters the light receiving surface of the photodetector 6, and then enters the light receiving surface of the photodetector 6 after being reflected once or multiple times by the two reflecting surfaces.

[0037] The second scattered light collection structure 8 includes a third reflector 81, which has a third reflective surface on the side facing the light working area 5.

[0038] See Figure 3The second scattered light collecting structure 8 also includes a fourth reflecting mirror 82. The side of the fourth reflecting mirror 82 away from the optical working area 5 has a fourth reflecting surface. The fourth reflecting mirror 82 and the periphery of the third reflecting mirror 81 are closely connected to form a second reflecting cavity 80. The fourth reflecting mirror 82 has a second light inlet 801. The side of the fourth reflecting mirror 82 facing the optical working area 5 is a second light absorption surface. Part of the scattered light 23 enters the second reflecting cavity 80 through the second light inlet 801, and after one or more reflections between the third and fourth reflecting surfaces, it exits through the second light inlet 801 and enters the first light inlet 701. By setting the fourth reflecting mirror 82, the adjustment requirements for the position of the first light inlet 701 can be reduced, and the light collected by the third reflecting mirror can be prevented from being absorbed by the outer surface of the first scattered light collecting device. The first light inlet 701 does not need to be located at the focal position of the third reflecting mirror 81, and most of the scattered light can enter the first reflecting cavity 70. The third reflecting mirror 81 can be a hemispherical mirror, an aspherical mirror, an ellipsoidal mirror, a cone, etc.

[0039] The first reflecting mirror 71, the second reflecting mirror 72, the third reflecting mirror 81, and the fourth reflecting mirror 82 can be hemispherical mirrors, conical mirrors, ellipsoidal mirrors, aspherical mirrors, etc. Their concave surfaces reflect light. There are no specific restrictions here. As an feasible approach, the first reflecting mirror 71 is a hemispherical mirror, and the photodetector 6 is set at the focal position of the first reflecting surface of the first reflecting mirror 71, which is conducive to the collection of scattered light by the photodetector 6.

[0040] In one specific embodiment, the first reflector 71 has a circular first light inlet 701 at its bottom end facing the light working area 5, the second reflector 72 has a circular first light outlet 702 at its bottom end away from the light working area 5, and the fourth reflector 82 has a circular second light inlet 801 at its bottom end facing the light working area 5. The minimum distance between the light working area 5 and the first light inlet 701 and the second light inlet 801 is 3 mm. The maximum diameter of the maximum orthographic projection area of ​​the first light inlet 701 is 1.3 times the maximum diameter of the orthographic projection area of ​​the light working area 5 along the projection line of the maximum orthographic projection area of ​​the first light inlet 701, and the maximum diameter of the maximum orthographic projection area of ​​the second light inlet 801 is 1.5 times the maximum diameter of the orthographic projection area of ​​the light working area 5 along the projection line of the maximum orthographic projection area of ​​the second light inlet 801.

[0041] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A particle counting sensor, comprising a light source emitting a light beam, a gas path assembly for the flow of air to be measured, wherein the light beam and the airflow intersect to form a working optical region, characterized in that, It also includes a photodetector and a scattered light collection component; surrounding the light beam, the scattered light collection component includes a first scattered light collection structure and a second scattered light collection structure respectively disposed on opposite sides of the optical working area; the second scattered light collection structure, the optical working area, the first scattered light collection structure, and the photodetector are arranged sequentially; the first scattered light collection structure has a light reflecting surface inside, and the light reflecting surface surrounds to form a first reflecting cavity; the first scattered light collection structure has a first light inlet and a first light outlet communicating with the first reflecting cavity and the outside, the first light inlet facing the optical working area, and the first light outlet being combined with the photodetector; the second scattered light collection structure has a third reflecting surface facing the optical working area, and light reflected from at least a portion of the third reflecting surface enters the first reflecting cavity through the first light inlet. The second scattered light collection structure includes a fourth reflective surface facing away from the light working area and a second light inlet facing the light working area. The third reflective surface and the fourth reflective surface are combined to form a second reflective cavity. The third reflective surface and the fourth reflective surface are the internal surfaces of the second scattered light collection. The first scattered light collection structure includes a first reflector and a second reflector. The side of the first reflector facing away from the light working area has a first reflective surface, and the side of the second reflector facing the light working area has a second reflective surface. The peripheries of the first reflector and the second reflector are closely connected to form the first reflective cavity. The first light inlet is located on the first reflector, and the first light outlet is located on the second reflector.

2. The particle counting sensor as described in claim 1, characterized in that, The first light inlet and the second light inlet are located on opposite sides of the optical working area, and along the projection line direction of the maximum orthographic projection area of ​​the first light inlet, the orthographic projections of the first light inlet, the second light inlet, and the optical working area have the maximum overlapping projection areas.

3. The particle counting sensor as described in claim 2, characterized in that, The edge of the orthographic projection of the optical working area does not extend beyond the edges of the orthographic projections of the first and second light inlets.

4. The particle counting sensor as described in claim 1, characterized in that, The optical working area is spaced apart from the first light inlet and the second light inlet, with the minimum distance between the optical working area and the first light inlet and the second light inlet being 1-10mm respectively.

5. The particle counting sensor as described in claim 1, characterized in that, The region on the outer surface of the first light-scattering collection structure facing the light beam is the first light-absorbing surface; the region on the outer surface of the second light-scattering collection structure facing the light beam is the second light-absorbing surface.

6. The particle counting sensor as claimed in claim 1, characterized in that, The first reflective cavity has two opposing reflective surfaces, which are closely connected at their periphery and surround the first light inlet and the first light outlet, respectively.

7. The particle counting sensor as described in claim 1, characterized in that, The fourth reflective surface surrounds the second light inlet.

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