Laser particle detection device

Abstract

The present invention discloses a laser particle detection device, comprising: a laser emission unit, a beam shaping and denoising unit, a light scattering unit and an extinction unit arranged in sequence along the laser emission direction, wherein the light scattering unit is provided with a main light path allowing the laser to enter and exit along the laser emission direction, a gas path allowing the gas to enter and exit, and a first detection light path and a second detection light path allowing the light to be detected to be emitted, and a cavity is formed at the intersection of the main light path and the gas path in the light scattering unit as a particle detection area; a biological particle detection unit connected to the first detection light path; a non-biological particle detection unit connected to the second detection light path; and an air inlet pipe and an exhaust pipe connected to the inlet and outlet of the gas path, respectively. The laser particle detection device of the present invention can effectively suppress the stray light generated by the laser light source and the reflected stray light of the detection light path, so as to improve the signal-to-noise ratio of the detection signal and realize high-sensitivity detection of microbial particles and non-biological particles in the sample gas.

Description

Technical Field

[0001] The present invention relates to the technical field of particle detection in atmospheric environment, in particular to laser particle detection technology. Background Art

[0002] In recent years, people have paid more and more attention to air quality, among which PM2.5 has appeared frequently in people's field of vision. PM2.5 refers to particles in the atmosphere with an aerodynamic equivalent diameter less than or equal to 2.5 microns, also known as respirable particles. PM2.5 has a small particle size, is rich in a large number of toxic and harmful substances, and has a long residence time in the atmosphere and a long transportation distance, so it has a greater impact on human health and atmospheric environmental quality. In addition, there are some microorganisms, bacteria and fungi in the air, which also have a certain impact on people's production and life.

[0003] For these particles (non-biological and biological) in the atmospheric environment, both domestic and foreign countries have begun to study methods for detecting them, mainly through optical methods. For non-biological particles, it is mainly through the use of a certain wavelength of light beam to illuminate the sample gas, and through the collection, analysis and processing of the light signal reflected by the particles, to analyze and detect them; for microbial particles, unlike non-biological particles, these microbial particles contain fluorescent substances, which will emit intrinsic fluorescence under the action of excitation light. They are usually illuminated by near-ultraviolet wavelength excitation light and detected based on the fluorescence signal they produce.

[0004] At present, the detection device for particulate matter in the atmospheric environment is not very appropriate in some details. For optical detection devices, especially weak light signal detection, the transmission of optical signals is crucial in the whole process, and the current detection device does not do much processing on the light generated by the light source. When the light source generates a beam of a certain wavelength, in addition to the beam generated by the central energy, the energy around the central energy will also generate a certain beam, and there are some small light spots. At the same time, due to the limitation of the light outlet device of the light source device, the light will also generate a certain angle of divergent light after coming out of the device, and these small light spots and stray light will have a certain impact on the detection results. Secondly, the existing forward detection optical path structure and vertical detection optical path structure have the problems of being greatly affected by the laser light source and low detection sensitivity; in addition, the existing lateral vertical detection optical path reported, the microbial detection optical path and the non-microbial particle optical path are in a straight line, and the reflected light generated by the objective lens will interfere with each other, reducing the signal-to-noise ratio. Therefore, it is extremely important to suppress the interference light spots and system stray light generated by the light source for optical detection, especially for the weak light signals generated by particulate matter in the gas. Summary of the invention

[0005] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide a laser particle detection device that can effectively suppress the interference light spots and stray light generated by the light source to achieve high-sensitivity detection of microbial particles and non-biological particles in the sample gas.

[0006] According to the present invention, a laser particle detection device is provided, comprising:

[0007] A laser emitting unit, a beam shaping and denoising unit, a light scattering unit and a light extinction unit are sequentially arranged along the laser emitting direction, wherein the light scattering unit is provided with a main light path allowing the laser to enter and exit along the laser emitting direction, a gas path allowing the gas to enter and exit, and a first detection light path and a second detection light path allowing the light to be detected to be emitted, a cavity is formed at the intersection of the main light path and the gas path in the light scattering unit as a particle detection area, and the first detection light path and the second detection light path extend from the particle detection area and are symmetrically arranged on both sides of the main light path;

[0008] a biological particle detection unit connected to the first detection optical path;

[0009] a non-biological particle detection unit connected to the second detection optical path; and

[0010] The air inlet pipe and the exhaust pipe are connected to the inlet and outlet of the air path respectively.

[0011] According to one embodiment of the present invention, the beam shaping and denoising unit comprises an aperture assembly and a cylindrical mirror arranged in sequence along the laser emission direction, and the cylindrical surface of the cylindrical mirror is arranged toward the aperture assembly.

[0012] According to one embodiment of the present invention, the aperture assembly includes a first central circular aperture, a second central circular aperture and a central rectangular aperture which are sequentially arranged along the laser emission direction and whose central axes coincide with each other.

[0013] According to an embodiment of the present invention, the included angle between the central axis of the first detection light path and the second detection light path and the main light path is 30°-45°.

[0014] According to one embodiment of the present invention, the light scattering unit comprises a first concave mirror and a second concave mirror, wherein:

[0015] The concave surface of the first concave mirror is arranged toward the first detection light path and the focus of the first concave mirror is located on the central axis of the first detection light path, and the light to be detected directed to the first concave mirror is converged by the first concave mirror and then emitted from the first detection light path;

[0016] The concave surface of the second concave mirror is arranged toward the second detection light path and the focus of the second concave mirror is located on the central axis of the second detection light path. The light to be detected directed to the second concave mirror is converged by the second concave mirror and then emitted from the second detection light path.

[0017] According to one embodiment of the present invention, the biological particle detection unit includes a first objective lens, at least one filter, a first plano-convex lens and a first photodetector arranged on the axis of the first detection light path in a direction away from the particle detection area, and the first photodetector is used to detect the fluorescence signal generated by the biological particles.

[0018] According to one embodiment of the present invention, the non-biological particle detection unit includes a second objective lens, a second plano-convex lens and a second photodetector arranged on the axis of the second detection light path in a direction away from the particle detection area, and the second photodetector is used to detect the scattered light signals generated by non-biological particles.

[0019] According to one embodiment of the present invention, the extinction unit includes a structured aperture and a light trap sequentially arranged along the laser emission direction.

[0020] According to one embodiment of the present invention, the central hole of the structured aperture has a multi-stage circular ladder structure with gradually increasing aperture along the laser emission direction to prevent laser reflection.

[0021] According to one embodiment of the present invention, the structured aperture is integrated at the exit of the main light path of the scattering unit.

[0022] The beneficial effects of the present invention are:

[0023] 1. Adding a beam shaping and denoising unit between the laser emission unit and the particle detection area can suppress the interference spot and stray light generated by the light source to improve the detection signal-to-noise ratio. The beam shaping and denoising unit can suppress the interference spot and stray light generated by the light source in a large range by combining the aperture assembly with the cylindrical mirror, so as to obtain more accurate detection results;

[0024] 2. Compared with the existing forward detection optical path that uses a filter to filter out the excitation light source, the present invention directly enters the light trap through the excitation light of the particle detection area, and the scattered light and fluorescence signal received by the biological particle fluorescence detection unit and the non-biological particle detection unit are less affected by the excitation light source, so the signal-to-noise ratio is higher;

[0025] 3. The first detection optical path for the biological particle detection unit and the second detection optical path for the non-biological particle detection unit are both at an angle of 30°-45° to the laser emission optical path, so that the biological particle fluorescence detection unit and the non-biological particle detection unit are at a certain angle, so the reflected stray light generated by the objective lens has less influence on each other, so the signal-to-noise ratio is higher;

[0026] 4. Compared with the existing lateral vertical detection optical path, since the forward scattered light intensity is relatively strong, the detection optical path of the present invention adopts a detection method with an angle of 30°-45° with the laser emission optical path, and the detected scattered light and fluorescence signals are stronger, and the detection sensitivity is higher;

[0027] 5. A light-converging concave mirror is set in the detection optical path of the biological particle detection unit and the opposite position of the light-collecting lens group in the non-biological particle detection unit to perform the first light-converging process to improve the collection efficiency of the light signal;

[0028] 6. Both the biological particle detection unit and the non-biological particle detection unit use objective lenses to collect the fluorescence and scattered light emitted by the particles, fully improving the utilization efficiency of fluorescence and scattered light;

[0029] 7. Use the combination of structured aperture and light trap to effectively prevent light reflection and further improve extinction efficiency;

[0030] 8. The air inlet adopts Laval nozzle, which makes the measured airflow in laminar state, and at the same time ensures that the airflow velocity of particles entering each point of the particle detection area is equal, so as to obtain more accurate test results;

[0031] 9. The inner diameter of the exhaust port is larger than that of the air inlet to prevent gas backflow and repeated detection, which will affect the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the optical path in the laser particle detection device in a specific embodiment of the present invention;

[0033] Figure 2 It is a schematic diagram of the structure of the gas path of the laser particle detection device according to a specific embodiment of the present invention;

[0034] Figure 3 yes Figure 1 or Figure 2 Schematic diagram of the structure of the light scattering unit;

[0035] Figure 4 yes Figure 1 or Figure 2 Schematic diagram of the structure of the incident surface of the middle aperture assembly;

[0036] Figure 5 yes Figure 1 or Figure 2 A schematic diagram of the structure of the exit surface of the middle aperture assembly;

[0037] Figure 6 yes Figure 1 or Figure 2 Schematic diagram of the structure of the medium structured aperture.

[0038] In the figure:

[0039] 1-light scattering unit, 11-main light path, 12-gas path, 13-first detection light path, 131-first concave mirror, 14-second detection light path, 141 second concave mirror, 15-particle detection area, 2-exhaust pipe, 3-laser emitting unit; 4-beam shaping and denoising unit, 41-aperture assembly, 411-first central circular aperture, 412-second central circular aperture, 413-central rectangular aperture, 42-cylindrical mirror, 5-biological particle detection unit, 51-first objective lens, 52-filter, 53-first plano-convex lens, 54-first photoelectric detector, 6-non-biological particle detection unit, 61-second objective lens, 62-second plano-convex lens, 63-second photoelectric detector, 7-extinction unit, 71-light trap, 72-structured aperture, 8-intake pipe, 9-air pump. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] like Figures 1 to 3As shown, the embodiment of the present invention discloses a laser particle detection device, including a laser emission unit 3, a beam shaping and denoising unit 4, a light scattering unit 1, a biological particle detection unit 5, a non-biological particle detection unit 6, an extinction unit 7, an air intake pipe 8 and an exhaust pipe 2. The light scattering unit 1 is provided with a main optical path 11 that allows the laser to enter and exit along the laser emission direction, an air path 12 that allows the gas to enter and exit, and a first detection optical path 13 and a second detection optical path 14 that allow the light to be detected to be emitted. The main optical path 11 and the air path 12 form a cavity at the intersection in the light scattering unit 1 as a particle detection area 15. The first detection optical path 13 and the second detection optical path 14 extend from the particle detection area 15 and are symmetrically arranged on both sides of the main optical path 11. The biological particle detection unit 5 and the non-biological particle detection unit 6 are respectively connected to the first detection optical path 13 and the second detection optical path 14. The air intake pipe 8 and the exhaust pipe 2 are respectively connected to the inlet and outlet of the air path 12. Based on the above structure, the laser emitting unit 3, the beam shaping and denoising unit 4, the light scattering unit 1 and the extinction unit 7 are arranged in sequence along the laser emitting direction. The laser is emitted from the laser emitting unit 3, and after being processed by the beam shaping and denoising unit 4 to suppress the stray light of the light source, the laser enters the light scattering unit 1 through the main optical path 11 and meets the sample gas entering the light scattering unit 1 from the air inlet pipe 8 through the air path 12 in the particle detection area 15. The laser irradiates the particles carried by the sample gas to generate scattered light and fluorescence as the light to be detected (wherein the fluorescence is generated by biological particles). A part of the light to be detected enters the biological particle detection unit 5 through the first detection optical path 13 for fluorescence detection of biological particles; the other part enters the non-biological particle detection unit 6 through the second detection optical path 14 for scattered light detection of non-biological particles. The excess laser that is not reflected by the particles passes through the light scattering unit 1 through the main optical path 12 and is finally absorbed by the extinction unit 7.

[0042] In the embodiment of the present invention, the laser emitting unit 3 can use a semiconductor laser, preferably a semiconductor laser with a wavelength of 405nm. It is small in size, light in weight, highly reliable, long in service life, low in power consumption, uses a low voltage constant current power supply mode, has a low power failure rate, is safe to use, and has low maintenance costs.

[0043] The beam shaping and denoising unit 4 may include an aperture assembly 41 and a cylindrical mirror 42 arranged in sequence along the laser emission direction, wherein the cylindrical surface of the cylindrical mirror 42 is arranged toward the aperture assembly 41. Figure 4 and Figure 5As shown, the aperture assembly 41 may include a first central circular aperture 411, a second central circular aperture 412, and a central rectangular aperture 413 which are parallel in the same direction and whose central axes coincide. The first central circular aperture 411, the second central circular aperture 412, and the central rectangular aperture 413 are arranged in sequence along the laser emission direction. Thus, the laser emitted by the laser emission unit 3 passes through the first central circular aperture 411, the second central circular aperture 412, the central rectangular aperture 413, and the cylindrical mirror 42 in sequence and then enters the particle detection area 15 of the light scattering unit 1. Specifically, the first central circular aperture 411 and the second central circular aperture 412 are apertures whose centers are set to a circular aperture, and in particular, the two can be the same aperture; the central rectangular aperture 413 is an aperture whose center is set to a rectangular aperture. In an embodiment of the present invention, the thickness of the first central circular aperture 411, the second central circular aperture 412, and the central rectangular aperture 413 can all be 0.05 mm. In another embodiment of the present invention, the first central circular aperture 411, the second central circular aperture 412 and the central rectangular aperture 413 can be an integrated structure, that is, the aperture assembly 41 adopts an integrated molding process and only uses one aperture piece to effectively suppress the interference light spot and stray light generated by the light source.

[0044] The first detection light path 13 and the second detection light path 14 of the light scattering unit 1 are symmetrically arranged on both sides of the main light path 11, so that the amount of light to be detected entering the first detection light path 13 and the second detection light path 14 is generally the same. Preferably, when the angle between the central axis of the first detection light path 13 and the second detection light path 14 and the main light path is 30°-45°, the absorption effect of the light to be detected is optimal. In an embodiment of the present invention, the light scattering unit 1 may further include a first concave mirror 131 and a second concave mirror 132 for converging the light to be detected. Specifically, Figure 1 As shown, the concave surface of the first concave mirror 131 is arranged toward the first detection light path 13 - for example, the back of the first concave mirror 131 is arranged against the wall opposite to the first detection light path 13 in the particle detection area 15, and the focus of the first concave mirror 131 is located on the central axis of the first detection light path 13, and the light to be detected directed to the first concave mirror 131 is converged by the first concave mirror 131 and then emitted from the first detection light path 13; the concave surface of the second concave mirror 132 is arranged toward the second detection light path 14 - for example, the back of the second concave mirror 132 is arranged against the wall opposite to the second detection light path 14 in the particle detection area 15, and the focus of the second concave mirror 132 is located on the central axis of the second detection light path 14, and the light to be detected directed to the second concave mirror 132 is converged by the second concave mirror 132 and then emitted from the second detection light path 14. Those skilled in the art may also adopt other methods to facilitate the convergence of the light to be detected.

[0045] The biological particle detection unit 5 and the non-biological particle detection unit 6 are intended to detect biological particles and non-biological particles respectively based on the received light signals to be detected. Figure 1 As shown, the biological particle detection unit 5 includes a first objective lens 51, at least one filter 52, a first plano-convex lens 53 and a first photodetector 54 arranged on the axis of the first detection light path 13 in a direction away from the particle detection area 15, and the first photodetector 54 is used to detect the fluorescence signal generated by the biological particles. In the embodiment of the present invention, the biological particle detection unit 5 includes two filters 52, which further improve the biological fluorescence detection efficiency by filtering out stray light. The non-biological particle detection unit 6 may include a second objective lens 61, a second plano-convex lens 62 and a second photodetector 63 arranged on the axis of the second detection light path 14 in a direction away from the particle detection area 15, and the second photodetector 63 is used to detect the scattered light signal generated by the non-biological particles. The biological particle detection unit 5 and the non-biological particle detection unit 6 use a lens plus a converging lens to collect light, which can fully improve the light absorption efficiency. In the embodiment of the present invention, the first photodetector 54 and the second photodetector 63 are both PMT photodetectors. In other embodiments, the first photodetector 54 and the second photodetector 63 can also be other photodetectors, but are not limited thereto.

[0046] The extinction unit 7 may include a structured aperture 72 and a light trap 71 arranged in sequence along the laser emission direction. Figure 6 As shown, the central hole of the structured aperture 72 has a multi-stage circular ladder structure with an aperture gradually increasing along the laser emission direction to prevent light reflection and further improve the extinction efficiency.

[0047] Further Figure 2 As shown, the air inlet pipe 8 can be a Laval nozzle 8 inserted at the entrance of the air path 12 to prevent gas flocculation and ensure that the air flow velocity of the sample gas entering each point of the particle detection area 15 is equal. The exhaust pipe 2 inserted at the outlet of the air path 12 can be set so that the inner diameter of the air inlet end is larger than the inner diameter of the air outlet end of the air inlet pipe 8 to prevent gas backflow. In an embodiment of the present invention, the air inlet pipe 8 is connected to a gas generator for providing sample gas; the outer end of the exhaust pipe 2 is connected to an air pump 9 to facilitate the discharge of the sample gas detected in the particle detection area 15 through the exhaust pipe 2. Preferably, the central axis of the air path 12 can be set perpendicular to the main light path 11 to facilitate smooth circulation of the sample gas.

[0048] In the embodiment of the present invention, the laser emission unit 3 and the beam shaping and denoising unit 4 are embedded in the entrance of the main optical path 11 of the light scattering unit 1; the biological particle detection unit 5, the non-biological particle detection unit 6 and the extinction unit 7 are respectively embedded in the exit of the first detection optical path 13, the exit of the second detection optical path 14 and the exit of the main optical path 11 of the light scattering unit 1, so as to further improve the overall firmness of the device and achieve the purpose of reducing the volume of the device. Preferably, the structured aperture 72 can be integrated at the exit of the main optical path 11 of the scattering unit 1 to make the structure of the laser particle detection device as simple as possible.

[0049] The working principle of the laser particle detection device of the present invention is as follows: the laser emitting unit 3 emits laser light, and the beam shaping and denoising unit 4 is composed of an aperture assembly 41 and a cylindrical mirror 42. The aperture assembly 41 includes a first central circular aperture 411, a second central aperture 412 and a central rectangular aperture 413. The light spot generated by the laser emitting unit 3 passes through the first central circular aperture 411 and the second central aperture 412 in sequence, and the small light spots around the central light spot and the stray light caused by the device can be filtered out to obtain a central circular light spot, and then pass through the central rectangular aperture 413 to obtain a flat rectangular light spot, and finally pass through the cylindrical mirror 42 to converge into a flat linear light spot, which is irradiated on the sample gas in the particle detection area 15. The laser passing through the particle detection area 15 enters the extinction unit 7 and is absorbed by the light trap 71. Under the action of the air pump, the sample gas enters the particle detection area 15 through the air inlet pipe 8. Under the action of the laser, the particles carried by the sample gas generate scattered light and fluorescence as the light to be detected. Part of the light to be detected that enters the biological particle detection unit 5 through the first detection optical path 13 is sequentially converged by the first concave mirror 131, collected by the first objective lens 51, converged by the first plano-convex lens 53, and filtered out by at least one filter 52 to obtain the fluorescence emitted by the microbial particles, and finally converted and processed by the first photodetector 54 to obtain an accurate result. Part of the light to be detected that enters the non-biological particle detection unit 6 through the second detection optical path 14 is sequentially converged by the second concave mirror 141, collected by the second objective lens 61, and converged by the second plano-convex lens 62, and the obtained scattered light is transmitted to the second photodetector 63 for conversion and processing to obtain an accurate result. Because the fluorescence signal is weaker than the laser scattered light signal, the infection of the biological fluorescence signal can be approximately ignored when detecting the scattered light signal of the non-biological particles. At the same time, signal processing will be performed when detecting the non-biological particles, and the scattered light signal generated by the biological particles will be filtered out to obtain the scattered light signal of the non-biological particles.

[0050] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A laser particle detection device, characterized in that: include: A laser emitting unit (3), a beam shaping and denoising unit (4), a light scattering unit (1) and a light extinction unit (7) are sequentially arranged along a laser emitting direction, wherein the light scattering unit (1) is provided with a main light path (11) for allowing laser to enter and exit along the laser emitting direction, a gas path (12) for allowing gas to enter and exit, and a first detection light path (13) and a second detection light path (14) for allowing light to be detected to be emitted, wherein a cavity is formed at the intersection of the main light path (11) and the gas path (12) in the light scattering unit (1) to serve as a particle detection area (15), and the first detection light path (13) and the second detection light path (14) extend from the particle detection area (15) and are directed to the particle detection area (15). symmetrically arranged on both sides of the main light path (11), the central axes of the first detection light path (13) and the second detection light path (14) being at an angle of 30°-45° with the main light path along the laser emission direction, wherein the light to be detected comprises scattered light and fluorescence generated by particles carried by the sample gas irradiated by the laser, and the fluorescence is generated by biological particles, and the beam shaping and denoising unit (4) comprises an aperture assembly (41) and a cylindrical mirror (42) arranged in sequence along the laser emission direction, and the aperture assembly (41) comprises a first central circular aperture (411), a second central circular aperture (412) and a central rectangular aperture (413) arranged in sequence along the laser emission direction and with the central axes coinciding with each other; A biological particle detection unit (5) connected to the first detection light path (13), comprising a first objective lens (51); a non-biological particle detection unit (6) connected to the second detection optical path (14), comprising a second objective lens (61); and An air inlet pipe (8) and an air outlet pipe (2) are respectively connected to the inlet and outlet of the air circuit (12).

2. The laser particle detection device according to claim 1, characterized in that: The cylindrical surface of the cylindrical mirror (42) is arranged facing the aperture unit (41).

3. The laser particle detection device according to claim 1, characterized in that: The light scattering unit (1) comprises a first concave mirror (131) and a second concave mirror (132), wherein: The concave surface of the first concave mirror (131) is arranged toward the first detection light path (13) and the focus of the first concave mirror (131) is located on the central axis of the first detection light path (13), and the light to be detected directed toward the first concave mirror (131) is converged by the first concave mirror (131) and then emitted from the first detection light path (13); The concave surface of the second concave mirror (132) is arranged toward the second detection light path (14) and the focus of the second concave mirror (132) is located on the central axis of the second detection light path (14); the light to be detected directed toward the second concave mirror (132) is converged by the second concave mirror (132) and then emitted from the second detection light path (14).

4. The laser particle detection device according to claim 1, characterized in that: The biological particle detection unit (5) comprises the first objective lens (51), at least one filter (52), a first plano-convex lens (53) and a first photodetector (54) arranged on the axis of the first detection light path (13) in a direction away from the particle detection area (15), wherein the first photodetector (54) is used to detect the fluorescent signal generated by the biological particles.

5. The laser particle detection device according to claim 1, characterized in that: The non-biological particle detection unit (6) comprises a second objective lens (61), a second plano-convex lens (62) and a second photodetector (63) arranged on the axis of the second detection light path (14) in a direction away from the particle detection area (15), wherein the second photodetector (63) is used to detect scattered light signals generated by non-biological particles.

6. The laser particle detection device according to claim 1, characterized in that: The extinction unit (7) comprises a structured aperture (72) and a light trap (71) arranged in sequence along the laser emission direction.

7. The laser particle detection device according to claim 6, characterized in that: The central hole of the structured diaphragm (72) has a multi-stage circular ladder structure with an aperture gradually increasing along the laser emission direction, so as to prevent laser reflection.

8. The laser particle detection device according to claim 7, characterized in that: The structured diaphragm (72) is integrated at the exit of the main light path (11) of the scattering unit (1).

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