A particle counter

Abstract

The application discloses a particle counter, which comprises a pumping source for emitting first wavelength laser; the first wavelength laser emitted by the pumping source enters a laser resonant cavity; a laser crystal is arranged in the laser resonant cavity, and the laser crystal is irradiated by the first wavelength laser to form second wavelength laser, and the second wavelength laser forms light oscillation in the laser resonant cavity; a convex lens group comprises two convex lenses with the same focal length and arranged at intervals, the convex lens group is arranged between the pumping source and the laser resonant cavity, and the convex lens group focuses the first wavelength laser on the laser crystal; an aerosol generating device provides an aerosol airflow into the laser resonant cavity, and the aerosol airflow passes through the light beam of the second wavelength laser; and a photoelectric detection device detects the scattering light signal of the aerosol particles. The application can realize detection of dust particles with a particle size of 0.1 microns, and has the advantages of low power consumption, portability and high detection precision.

Description

Technical Field

[0001] This invention relates to the field of gas detection technology, and more particularly to a particle counter. Background Technology

[0002] Currently, laser-based particle counters are relatively mature for detecting particles larger than 0.3 micrometers in diameter, accurately detecting their concentration. However, for particles smaller than 0.3 micrometers, the scattered light intensity is extremely weak because it is proportional to the sixth power of the particle size. Furthermore, Rayleigh scattering in the air contributes as background noise. Therefore, a high-energy laser beam with a suitable beam shape is required to detect particles smaller than 0.3 micrometers, typically requiring a laser power of 40 watts or higher. However, using high-power lasers results in high electrical power and high heat generation.

[0003] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0004] In view of the problems pointed out in the background art, the present invention provides a particle counter that can detect dust particles with a diameter of 0.1 micrometers, and has the advantages of low power consumption, portability and high detection accuracy.

[0005] To achieve the above-mentioned objectives, the present invention employs the following technical solution: In some embodiments, a particle counter is provided, comprising: A pump source, configured to emit a first wavelength of laser light; A laser resonant cavity, wherein the first wavelength laser emitted from the pump source enters the laser resonant cavity; A laser crystal is disposed within the laser resonant cavity, and the laser crystal is configured to generate a second wavelength laser when irradiated by a first wavelength laser, the second wavelength laser generating optical oscillation within the laser resonant cavity; A convex lens group includes two convex lenses with the same focal length and arranged at intervals. The convex lens group is disposed between the pump source and the laser resonant cavity. The convex lens group is configured to focus the first wavelength laser onto the laser crystal. An aerosol generator is configured to provide an aerosol gas flow into the laser resonant cavity, the aerosol gas flow passing through a beam of a second wavelength laser. A photoelectric detection device configured to detect the scattered light signal from aerosol particles.

[0006] In some embodiments, the laser resonant cavity is composed of a plano-concave cylindrical mirror and a plano-concave mirror, wherein the concave surface of the plano-concave cylindrical mirror faces the laser resonant cavity, and the concave surface of the plano-concave mirror faces the laser resonant cavity.

[0007] In some embodiments, the particle counter includes a substrate in which an optical chamber is formed, through which the second wavelength laser passes and a photosensitive region is located within the optical chamber; The substrate has a window located near the plano-concave reflector, and a detachable sealing part is provided inside the window.

[0008] In some embodiments, the particle counter includes a substrate in which an optical chamber is formed, through which the second wavelength laser passes and a photosensitive region is located within the optical chamber; The substrate is provided with a clean air inlet and a clean air outlet, and the clean air enters the light chamber sequentially through the clean air inlet and the clean air outlet.

[0009] In some embodiments, the photoelectric detection device includes a second photodetector and a second scattered light collection system, wherein the second scattered light collection system uses a set of Manning lenses to collect scattered light signals.

[0010] In some embodiments, the particle counter includes a substrate in which an optical chamber is formed, through which the second wavelength laser passes and a photosensitive region is located within the optical chamber; A transparent sheet is disposed on the substrate, and a light-transmitting hole is disposed on the Manning lens. The transparent sheet is configured to close the light-transmitting hole on the Manning lens near the second photodetector, thereby sealing the light chamber.

[0011] In some embodiments, the photoelectric detection device includes a first photodetector and a first scattered light collection system, wherein the first scattered light collection system uses an aspherical lens to collect scattered light signals.

[0012] In some embodiments, the first photodetector is further configured to detect the light intensity within the laser resonant cavity, and the system adjusts the current of the pump source based on the detected light intensity to keep the light intensity within the laser resonant cavity constant.

[0013] In some embodiments, the laser crystal is surrounded by an indium foil.

[0014] In some embodiments, a particle counter is provided, comprising: A pump source, configured to emit a first wavelength of laser light; A laser resonant cavity is formed by a plano-concave cylindrical mirror and a plano-concave mirror. The concave surface of the plano-concave cylindrical mirror faces the laser resonant cavity. The first wavelength laser enters the laser resonant cavity through the plano-concave cylindrical mirror. A laser crystal is disposed within the laser resonant cavity, and the laser crystal is configured to generate a second wavelength laser when irradiated by a first wavelength laser, the second wavelength laser generating optical oscillation within the laser resonant cavity; An aerosol generator is configured to provide an aerosol gas flow into the laser resonant cavity, the aerosol gas flow passing through a beam of a second wavelength laser. A photoelectric detection device configured to detect the scattered light signal from aerosol particles.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are: The particle counter disclosed in this application utilizes a pump source, a laser crystal, and related optical paths. It employs a low-energy pump source outside the laser resonant cavity, uses a laser crystal to obtain a high-power laser within the laser resonant cavity, and utilizes the high-power laser source within the cavity to detect particles with a diameter of 0.1-0.3 micrometers. It also has the advantages of low power consumption, portability, and high detection accuracy.

[0016] The first wavelength laser beam is focused onto the laser crystal using a convex lens group. The size of the focused laser beam can be adjusted by changing the focal length of the two convex lenses.

[0017] By using a planar cylindrical mirror instead of a plane mirror, the thickness of the light beam in the photosensitive area is compressed, which not only further improves the power density in the photosensitive area, but also makes the travel time of particles passing through the light beam shorter and the pulse width of the generated pulse signal narrower. Under the same bandwidth measurement circuit, this scheme can measure particulate aerosols with a higher concentration upper limit.

[0018] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0019] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1This is a schematic diagram of a particle counter according to some embodiments; Figure 2 This is yet another schematic diagram of the principle of a particle counter according to some embodiments; Figure 3 A cross-sectional view of a particle counter according to some embodiments; Figure 4 The absorption cross section of a Pr:YLF crystal according to some embodiments; Figure 5 The emission cross section of a Pr:YLF crystal according to some embodiments; Figure 6 This is a schematic diagram of the response spectrum of a silicon photodiode according to some embodiments; Figure label: 10. Pump source; 11. First wavelength laser; 12. Heat sink; 21. Plano-concave cylindrical mirror; 22. Plano-concave mirror; 30. Laser crystal; 31. Second wavelength laser; 41. Aerosol nozzle; 42. Aerosol outlet; 50. First photoelectric detection module; 51. First photoelectric detector; 52. First scattered light collection system; 53. Aspherical lens; 60. Second photoelectric detection module; 61. Second photoelectric detector; 62. Second scattered light collection system; 63. Manning mirror; 70. Matrix; 71. Light chamber; 72. Window; 73. Transparent sheet; 74. Clean air inlet; 75. Clean air outlet; 80. Photosensitive area; 90. Convex lens group; 91. Convex lens. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0023] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0024] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0025] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0026] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0027] In some embodiments, a particle counter is provided to achieve at least the technical effects of low power consumption, portability, and high detection accuracy. This particle counter can detect particles with a diameter of 0.3 micrometers or larger, as well as particles with a diameter of 0.1-0.3 micrometers.

[0028] In existing technologies, laser-based particle counters can detect particle concentrations larger than 0.3 micrometers, but they cannot detect particles with a diameter of 0.1-0.3 micrometers. The core technical challenge limiting the detection of particles with a diameter of 0.1-0.3 micrometers by existing particle counters is the inability to obtain a high-power laser source capable of detecting particles with a diameter of 0.1-0.3 micrometers.

[0029] In instruments for detecting particles larger than 0.3 micrometers, semiconductor laser diodes are generally used as the light source. Semiconductor laser diodes have advantages such as low cost, small size, and light weight.

[0030] However, when detecting particles with a diameter of 0.1-0.3 micrometers, the intensity of the scattered light is approximately proportional to the sixth power of the particle size, resulting in very weak scattered light intensity. This necessitates a higher power light source, and laser diodes with output power only reaching the watt level are clearly insufficient to meet the detection requirements.

[0031] When detecting dust particles with a diameter of 0.1-0.3 micrometers, the scattered light is extremely weak due to the very small particle size, and the Rayleigh scattering power from the air is already significant. Furthermore, Rayleigh scattering from the air acts as background noise, drastically reducing the signal-to-noise ratio (SNR) of the scattered light signal. Since the noise from Rayleigh scattering is proportional to the square root of the Rayleigh scattering intensity, and the scattered light signal from dust particles is proportional to the incident light power, increasing the laser power by n times will increase the SNR of the scattered light signal by the square root of n times.

[0032] For example, when using a 640nm wavelength laser, a laser power of at least 40 watts is required to effectively detect particles with a diameter of 0.1 micrometers. However, using a high-power laser diode means even higher electrical power and more heat generation, making it difficult to manufacture portable detection instruments.

[0033] In summary, due to the current limitations of laser diode technology, it is impossible to obtain a high-power laser source capable of detecting particles in the 0.1-0.3 micrometer range using laser diodes alone.

[0034] In view of the above technical background, this embodiment proposes a particle counter, referring to... Figures 1 to 3By creatively utilizing the combination of pump source 10, laser crystal 30 and related optical paths, a high-power laser source is obtained to achieve particle detection with a particle size of 0.1-0.3 micrometers, while also having the advantages of low power consumption, portability and high detection accuracy. Figure 1 This is the X-view of the particle counter. Figure 2 This is the Y-view of the particle counter. Figure 3 This is a cross-sectional view of a particle counter structure.

[0035] Specifically, the particle counter includes a pump source 10 configured to emit a first wavelength laser 11. The light source 10 produces a linear light spot, capable of generating a sheet-like beam suitable for dust particle size detection.

[0036] In one specific embodiment, the pump source 10 is a laser diode, which is low in cost, small in size and light in weight, which is beneficial to the compactness of the overall structure and the convenient design.

[0037] The particle counter includes a laser resonant cavity. The laser resonant cavity is a steady-state internal resonant cavity. The first wavelength laser 11 emitted by the pump source 10 enters the laser resonant cavity.

[0038] The particle counter includes a laser crystal 30 disposed in a laser resonant cavity. The laser crystal 30 is configured to be irradiated by a first wavelength laser 11 to form a second wavelength laser 31, and the second wavelength laser 31 forms optical oscillations in the laser resonant cavity.

[0039] In other words, the first wavelength laser 11 entering the laser resonant cavity is focused onto the laser crystal 30, and the laser crystal 30 is irradiated to form the second wavelength laser 31.

[0040] The cavity mirrors forming the laser resonant cavity have high reflectivity for the second wavelength laser 31. Because the laser resonant cavity is a steady-state cavity, it has low intracavity loss, and the second wavelength laser 31 has high intensity within the cavity. The second wavelength laser 31 undergoes a high number of reflections within the laser resonant cavity, fully utilizing the reflected signal generated by the light energy, resulting in high light energy utilization.

[0041] In other words, by using a low-power pump source 10 outside the laser resonator, a high-power laser can be obtained inside the laser resonator. In this way, the high-power laser source inside the cavity can be used to detect particles with a diameter of 0.1-0.3 micrometers.

[0042] Particle detection inside a laser resonant cavity can achieve extremely high energy density in the photosensitive region compared to detection outside the cavity.

[0043] The particle counter includes an aerosol generator configured to supply an aerosol gas flow into the laser resonant cavity, the aerosol gas flow passing through the beam of a second wavelength laser 31.

[0044] The specific structure of the aerosol generating device can be referred to in the prior art, and will not be elaborated in this embodiment. The aerosol generating device includes an aerosol nozzle 41 and an aerosol outlet 42. The aerosol gas flow from the aerosol nozzle 41 passes through the beam of the second wavelength laser 31 at a certain speed. When the aerosol particles pass through the laser beam, they will scatter the laser beam, and the aerosol particles will flow out from the aerosol outlet 42.

[0045] The particle counter includes a photodetector configured to detect the scattered light signal from aerosol particles.

[0046] Because the second wavelength laser beam 31 in the laser resonant cavity has high power, aerosol particles passing through the second wavelength laser beam can generate strong scattered light. When detecting particles with a diameter of 0.1-0.3 micrometers, although the scattering is relatively weak due to the small particle size, the high power of the laser beam still allows for the detection of particle signals, thereby achieving the detection of particles with a diameter of 0.1-0.3 micrometers and meeting the requirements for small particle detection.

[0047] In some embodiments, the particle counter further includes a convex lens group 90, which includes two convex lenses 91 with the same focal length and arranged at intervals. The convex lens group 90 is disposed between the pump source 10 and the laser resonant cavity, and is configured to focus the first wavelength laser 11 onto the laser crystal 30.

[0048] The size of the focused laser beam 11 of the first wavelength can be adjusted by adjusting the focal length of the two convex lenses 91.

[0049] In some embodiments, the coating on the convex lens 91 has high transmittance for 400-700nm laser light.

[0050] In some embodiments, the laser resonant cavity is composed of a plano-concave cylindrical mirror 21 and a plano-concave mirror 22. The plano-concave cylindrical mirror 21 and the plano-concave mirror 22 are arranged at intervals along the irradiation direction of the first wavelength laser 11. The concave surface of the plano-concave cylindrical mirror 21 faces the interior of the laser resonant cavity, and the flat surface of the plano-concave cylindrical mirror 21 faces the exterior of the laser resonant cavity. The concave surface of the plano-concave mirror 22 faces the interior of the laser resonant cavity, and the flat surface of the plano-concave mirror 22 faces the exterior of the laser resonant cavity. The first wavelength laser 11 enters the laser resonant cavity through the plano-concave cylindrical mirror 21. A laser resonant cavity is constructed by using plano-concave cylindrical mirror 21 and plano-concave mirror 22. With appropriate lens parameters of curvature, a sheet-like light spot is formed in the photosensitive area 80 through which aerosol particles pass. By utilizing the special structure of the cavity mirror, the light beam in the photosensitive area 80 is narrowed, which greatly compresses the time for particles to pass through the light beam. The pulse width of the generated pulsed particle signal is narrower. Under the same bandwidth circuit, while meeting the maximum overlap loss parameter of 10% mentioned in the standard, this scheme can measure a higher upper limit of particle concentration.

[0051] In other words, by using a planar cylindrical mirror 21 instead of a planar mirror, the thickness of the light beam in the photosensitive area is compressed, which not only further improves the power density in the photosensitive area, but also makes the travel time of particles passing through the light beam shorter and the pulse width of the generated pulse signal narrower. Under the same bandwidth measurement circuit, this scheme can measure particulate aerosols with a higher concentration upper limit.

[0052] The plano-concave cylindrical reflector 21 and the plano-concave reflector 22 have high reflectivity for the second wavelength laser 31. Because the laser resonant cavity is a steady-state cavity, it has low intracavity loss, and the second wavelength laser 31 has high intensity within the cavity. The second wavelength laser 31 undergoes a high number of reflections within the laser resonant cavity, fully utilizing the reflected signal generated by the light energy, resulting in high light energy utilization.

[0053] This invention is based on the internal cavity detection principle of a solid-state laser, which enables the measurement of aerosol particles with a lower limit of 0.1 μm. By using the beam narrowing technology of cylindrical mirrors, the beam thickness inside the laser resonant cavity is reduced, resulting in a high power density laser beam and increasing the upper limit of the concentration of the measured particles.

[0054] In some embodiments, the plano-concave cylindrical mirror 21 and the plano-concave mirror 22 are both coated with a reflective film with high reflectivity to the second wavelength laser 31 on the side facing the laser resonator, so that the reflectivity of the plano-concave cylindrical mirror 21 and the plano-concave mirror 22 to the second wavelength laser 31 is not less than 95%, which helps to reduce intracavity loss and increase intracavity optical power.

[0055] In one specific embodiment, the reflectivity of the plano-concave cylindrical reflector 21 to the second wavelength laser 31 is not less than 99.9%, and the reflectivity of the plano-concave reflector 22 to the second wavelength laser 31 is not less than 99.9%.

[0056] In some embodiments, the transmittance of the plano-concave cylindrical reflector 21 to the first wavelength laser 11 is not less than 80%, so as to ensure that as much of the first wavelength laser 11 as possible enters the laser resonant cavity.

[0057] In some embodiments, the concave side of the plano-concave cylindrical reflector 21 is coated with a dielectric film layer, which has high transmittance to the first wavelength laser 11 and high reflectance to the second wavelength laser 31. For example, the dielectric film layer has high transmittance to 445nm laser and high reflectance to 640nm laser.

[0058] The concave side of the plano-concave reflector 22 is coated with a dielectric film layer, which has high transmittance for the first wavelength laser 11 and high reflectivity for the second wavelength laser 31. For example, the dielectric film layer has high transmittance for 445nm laser and high reflectivity for 640nm laser.

[0059] In some embodiments, the laser crystal 30 is a Pr:YLF crystal. The theoretical analysis for selecting a Pr:YLF crystal is as follows: Particle scattering has the following characteristics: (1) the intensity of scattered light is proportional to the intensity of incident light; (2) the intensity of scattered light is approximately proportional to the sixth power of the particle size; (3) the intensity of scattered light is approximately inversely proportional to the fourth power of the incident light wavelength.

[0060] In other words, the scattering signal of a 0.1-micrometer particle is only about 1 / 700th of the scattering signal of a 0.3-micrometer particle. In order to detect the scattering signal of small-diameter particles, on the one hand, the power of the incident laser should be increased, and on the other hand, light with the shortest possible wavelength should be used.

[0061] The detection capability of a particle counter is also related to the response spectrum of the detector used to detect scattered light. This detector can be a photomultiplier tube, a silicon photodiode, or a gallium arsenide photodiode. The response spectrum of a commonly used silicon photodiode is as follows: Figure 6 As shown, silicon photodiodes, as commonly used photoelectric detection devices, have the advantages of low dark current and large dynamic range, but their response spectrum is mainly in the range of 0.6-1 micrometer. Therefore, the wavelength of the light source is required to be optimal within this range.

[0062] The detection capability of small-particle-sized scattering signals is also affected by the photodetector. Commonly used silicon photodetectors have the advantages of low dark current and large dynamic range, but their high response is mainly in the 0.6-1 micrometer wavelength range. Therefore, the laser wavelength should be selected within this range.

[0063] Lasers also possess a unique characteristic: the optical power inside the resonant cavity is significantly higher than the output power outside the cavity. The ratio of output power to cavity power is approximately equal to the transmittance of the output cavity mirror. In other words, if a cavity mirror with a reflectivity of 99.99% is used, the generated laser light will continuously reflect within the resonant cavity, with only 0.001% of the light projecting out. Therefore, the cavity power is 10,000 times the output power. Consequently, detecting dust particles inside the cavity will greatly enhance detection capabilities.

[0064] Based on the above considerations, we adopted a scheme that uses a laser diode as the pump source 10, a Pr:YLF crystal as the laser crystal 30, and a high-reflectivity resonant mirror for detection within the laser resonant cavity, which can achieve the detection of dust particles as small as 0.1 micrometers.

[0065] Pr:YLF crystals possess a unique stepped energy level structure. The stimulated absorption cross-sections of Pr:YLF crystals at various wavelengths are as follows: Figure 4 As shown, the stimulated emission cross section is as follows Figure 5 As shown.

[0066] Figure 4 Curves a and b represent the absorption cross-sections of the Pr:YLF crystal for pump light with different polarization directions. A larger absorption cross-section means a higher absorption rate. As can be seen from the figures, the crystal absorbs pump light in the 430-490 nm range, with three absorption peaks at 444 nm, 469 nm, and 479 nm. The absorption cross-sections are relatively large, and the efficiency of generating the second wavelength laser is highest when the pump light wavelength is at these three wavelengths.

[0067] Based on this, the particle counter in this case uses a laser diode capable of emitting a first wavelength laser with a wavelength range of [439, 449] nm as the pump source 10, which can output about 5W of optical power and is relatively inexpensive.

[0068] Figure 5 Curves c and d represent the emission cross-sections of the Pr:YLF crystal in different polarization directions; a larger emission cross-section indicates a higher emissivity. As shown in the figure, Pr:YLF exhibits emission peaks at 479, 523, 640, 604, 607, 698, and 721 nm. Since the emission and absorption peaks coincide at 479 nm, it is unsuitable for generating laser light at this wavelength. 640 nm has a relatively high emission cross-section, making it the most suitable wavelength for laser generation, followed by 523 nm. Other wavelengths have low absorption rates, resulting in lower pump light conversion efficiency, and are unsuitable for laser generation unless specific requirements dictate otherwise.

[0069] In summary, within the visible light spectrum, Pr:YLF crystals can generate a variety of different transition wavelengths, covering a wide range and exhibiting a large emission cross-section. Laser output can be achieved in six visible light bands: near-infrared (720 nm), red (695 nm), red (639 nm), orange (607 nm), green (522 nm), and blue (479 nm). Therefore, Pr:YLF crystals are ideal working media for obtaining visible light lasers.

[0070] Among them, the blue light band (479 nm) belongs to the quasi-third level, while the other five bands are typical fourth-level processes. Furthermore, from... Figure 4It can be seen that the region with strong gain in the emission spectrum of Pr:YLF crystal is located in the 640nm band, while the absorption rate at 444nm is relatively high.

[0071] Based on the above analysis, the particle counter in this case uses a laser diode capable of emitting a first wavelength laser in the wavelength range of [439, 449] nm as the pump source for the Pr:YLF crystal. The stimulated emission of the Pr:YLF crystal generates a second wavelength laser in the wavelength range of [638, 642] nm, which has significant advantages in terms of technology and cost. Using a second wavelength laser of [638, 642] nm for the Pr:YLF crystal can balance the intensity of scattered light and the spectral response characteristics of the photoelectric detection device, making it very suitable as the light source for a laser particle counter.

[0072] Based on the above analysis, in some embodiments, a pump source 10 capable of emitting wavelengths in the range of [400, 700] nm is used as the light source for the Pr:YLF crystal. The Pr:YLF crystal generates laser light with a wavelength range of [500, 700] nm through stimulated emission, so as to detect particles in the resonant cavity.

[0073] That is to say, the wavelength range of the first wavelength laser emitted by the pump source 10 is [400, 700] nm, and the wavelength range of the second wavelength laser 31 generated by the Pr:YLF crystal is [500, 700] nm.

[0074] Furthermore, as mentioned above, the Pr:YLF crystal absorbs pump light in the range of 430-490 nm. Therefore, a pump source 10 capable of emitting light with a wavelength range of [430, 490] nm is used as the light source for the Pr:YLF crystal. That is to say, the wavelength range of the first wavelength laser 11 emitted by the pump source 10 is [430, 490] nm.

[0075] Furthermore, as mentioned above, the Pr:YLF crystal absorbs pump light in the range of 430-490nm, with three absorption peaks at 444nm, 469nm, and 479nm. The absorption cross-section is relatively large, and the efficiency of generating the second wavelength laser is highest when the pump light wavelength is within these three wavelengths. Therefore, a pump source 10 capable of emitting wavelengths in the range of [439, 449]nm, [464, 474]nm, or [474, 484]nm is used as the light source for the Pr:YLF crystal.

[0076] That is to say, the wavelength range of the first wavelength laser 11 emitted by the pump source 10 is [439, 449] nm or [464, 474] nm or [474, 484] nm.

[0077] Furthermore, as mentioned above, Pr:YLF crystals have a high emission cross-section at 640nm, making them most suitable for generating lasers at this wavelength, followed by 523nm. Other wavelengths have low absorption rates, resulting in lower pump light conversion efficiency. Based on this, the wavelength range of the second wavelength laser generated by the Pr:YLF crystal is set to [638, 642]nm or [521, 525]nm.

[0078] In some embodiments, the wavelength of the first wavelength laser 11 is 445 nm, and the wavelength of the second wavelength laser 31 is 640 nm.

[0079] In some embodiments, the photoelectric detection device includes a first photoelectric detection module 50, which is configured to detect the scattered light signal of particles with a diameter of 1-5 micrometers.

[0080] The first photoelectric detection module 50 includes a first photoelectric detector 51 and a first scattered light collection system 52. The first scattered light collection system 52 uses an aspherical lens 53 to collect scattered light signals.

[0081] In some embodiments, the first photodetector is further configured to detect the light intensity within the laser resonant cavity, and the system adjusts the current of the pump source based on the detected light intensity to keep the light intensity within the laser resonant cavity constant.

[0082] This application is based on the Rayleigh scattering principle, utilizing Rayleigh scattering in air to detect the light intensity inside a laser resonant cavity. Under the action of an aspherical lens 53, the light beam in the photosensitive area is imaged onto the first photodetector 51. The concentration of 0.5μm particles in the optical chamber is less than 300,000 / ft. 3 When the Rayleigh scattering intensity is unaffected by particles, the real-time power monitoring and adjustment function is activated, ensuring the consistency of light intensity inside the laser resonant cavity. This greatly improves the consistency of sensor measurements, thereby ensuring the reliability of equipment measurements.

[0083] In other words, this application uses the Rayleigh scattering principle to monitor the light intensity inside the laser resonant cavity in real time, and uses an automatic current adjustment program to perform power compensation adjustment to ensure the measurement consistency of the sensor and the reliability of the equipment.

[0084] In some embodiments, the aspherical lens 53 is a coated lens with a coating wavelength of HT@640nm and HR@445nm, which images the light intensity signal generated by Rayleigh scattering onto the first photodetector 51, thereby isolating the interference of the 445nm pump light.

[0085] In some embodiments, the photoelectric detection device includes a second photoelectric detection module 60, which is configured to detect the scattered light signal of particles with a diameter of 0.1-1 micrometer.

[0086] The second photoelectric detection module 60 includes a second photoelectric detector 61 and a second scattered light collection system 62. The second scattered light collection system 62 uses a set of Manning lenses 63 to collect scattered light signals. By setting a set of Manning lenses 63, the light signal collection angle can be increased and spherical aberration generated during the imaging process can be eliminated, so that the particulate matter signal can be accurately imaged on the photosensitive surface of the second photoelectric detector 61.

[0087] In some embodiments, the particle counter includes a substrate 70, within which an optical chamber 71 is formed. A second wavelength laser 31 passes through the optical chamber 71, and a photosensitive region 80 is located within the optical chamber 71.

[0088] The pump source 10, the convex lens group 90, the plano-concave cylindrical mirror 21, and the laser crystal 30 are disposed on the first side of the substrate 70, for example... Figure 3 The left side of the indicated orientation. The plano-concave reflector 22 is disposed on the second side of the substrate 70, for example... Figure 3 The right side of the indicated orientation. The first photodetector 51 is disposed on the third side of the substrate 70, for example... Figure 3 The lower side of the indicated orientation. The second photodetector 61 is disposed on the fourth side of the substrate 70, for example... Figure 3 The aerosol nozzle 41 is located on the upper side of the substrate 70, as shown. For example, on the fifth side of the substrate 70... Figure 3 The rear side is shown in the orientation. The aerosol outlet 42 is located on the sixth side of the substrate 70, for example... Figure 3 The front side of the indicated direction.

[0089] In some embodiments, the substrate 70 is provided with a window 72, which is located near the plano-concave reflector 22, and a sealing part is detachably provided inside the window 72. For example, the sealing part is a plug.

[0090] When the sensor fails to restore its power to the factory level after prolonged operation, the first step is to rule out whether the lens is dirty. An optical swab soaked in alcohol can be inserted through window 72 to wipe the optical lens, facilitating instrument maintenance.

[0091] For example, remove the sealing part, insert a cotton swab through window 72 into the light chamber 71, and wipe the plano-concave reflector 22.

[0092] In some embodiments, the substrate 70 is provided with a clean air inlet 74 and a clean air outlet 75, which are connected by an air passage. External clean air enters the light chamber 71 sequentially through the clean air inlet 74 and the clean air outlet 75.

[0093] Using clean gas ensures that the optical components inside the laser resonator are not exposed to the aerosol environment, thus extending the reliability of the equipment.

[0094] In some embodiments, the clean gas outlet 75 adopts a variable diameter design, which acts as an aperture, effectively weakening the oscillation of stray light in the optical path of the laser resonant cavity, and helping to reduce optical noise in the gas chamber.

[0095] In some embodiments, a transparent sheet 73 is provided on the substrate 70, and a light-transmitting hole is provided on the Manning lens 63. The transparent sheet 73 is configured to close the light-transmitting hole on the Manning lens 63 near the second photodetector 61 to close the light chamber.

[0096] The transparent sheet 73 faces the second photodetector 61, which detects particle size signals through the transparent sheet 73. The transparent sheet 73 also serves to seal the optical chamber 71.

[0097] The light-passing aperture of the Mankin mirror 63 is designed with a chamfer, which greatly reduces the impact of stray light signals on the optical noise of the first photodetector 51 and the second photodetector 61.

[0098] In some embodiments, the laser crystal 30 is wrapped with indium foil to improve heat dissipation efficiency and is fixed on a heat sink made of copper material, which can quickly dissipate the heat generated when the crystal is working.

[0099] In some embodiments, the pump source 10 is fixed on the heat sink 12. During operation, the heat sink 12 must be cooled by a cooling fan to ensure the stability of its power and wavelength.

[0100] In some embodiments, the cross-section of the aerosol nozzle 41 is elliptical, and its widest position dimension is the light spot width, ensuring that all particles generate corresponding signals as they pass through the photosensitive area.

[0101] The working principle of the particle counter in this application is as follows: the pump source 10 emits a first wavelength laser 11, which passes through the convex lens group 90 and the plano-concave cylindrical mirror 21 in sequence and enters the laser resonant cavity. The first wavelength laser 11 is focused onto the laser crystal 30. The laser crystal 30 is stimulated to generate a second wavelength laser 31, which resonates between the plano-concave cylindrical mirror 21 and the plano-concave mirror 22. The aerosol generator inputs aerosol into the laser resonant cavity. The aerosol flows out from the aerosol nozzle 41 and passes through the beam of the second wavelength laser 31 at a certain speed. When the aerosol particles pass through the beam of the second wavelength laser 31, they will scatter the laser. Because the second wavelength laser beam 31 has high power, it can generate strong scattered light. Although the scattering of 0.1-micron particles is relatively weak due to their small particle size, the high power of the laser beam still allows for the detection of particle signals, thus enabling the detection of 0.1-micron particle size.

[0102] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0103] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A particle counter, characterized in that, include: A pump source, configured to emit a first wavelength of laser light; A laser resonant cavity, into which the first wavelength laser emitted from the pump source enters; A laser crystal is disposed within the laser resonant cavity, and the laser crystal is configured to generate a second wavelength laser when irradiated by a first wavelength laser, the second wavelength laser generating optical oscillation within the laser resonant cavity; A convex lens group includes two convex lenses with the same focal length and arranged at intervals. The convex lens group is disposed between the pump source and the laser resonant cavity. The convex lens group is configured to focus the first wavelength laser onto the laser crystal. An aerosol generator is configured to provide an aerosol gas flow into the laser resonant cavity, the aerosol gas flow passing through a beam of a second wavelength laser. A photoelectric detection device configured to detect the scattered light signal from aerosol particles.

2. The particle counter according to claim 1, characterized in that, The laser resonant cavity is composed of a plano-concave cylindrical mirror and a plano-concave mirror, with the concave surface of the plano-concave cylindrical mirror facing the laser resonant cavity and the concave surface of the plano-concave mirror facing the laser resonant cavity.

3. The particle counter according to claim 2, characterized in that, The particle counter includes a substrate, in which an optical chamber is formed. The second wavelength laser passes through the optical chamber, and the photosensitive region is located within the optical chamber. The substrate has a window located near the plano-concave reflector, and a detachable sealing part is provided inside the window.

4. The particle counter according to claim 1, characterized in that, The particle counter includes a substrate, in which an optical chamber is formed. The second wavelength laser passes through the optical chamber, and the photosensitive region is located within the optical chamber. The substrate is provided with a clean air inlet and a clean air outlet, and the clean air enters the light chamber sequentially through the clean air inlet and the clean air outlet.

5. The particle counter according to claim 1, characterized in that, The photoelectric detection device includes a second photoelectric detector and a second scattered light collection system. The second scattered light collection system uses a set of Manning lenses to collect scattered light signals.

6. The particle counter according to claim 5, characterized in that, The particle counter includes a substrate, in which an optical chamber is formed. The second wavelength laser passes through the optical chamber, and the photosensitive region is located within the optical chamber. A transparent sheet is disposed on the substrate, and a light-transmitting hole is disposed on the Manning lens. The transparent sheet is configured to close the light-transmitting hole on the Manning lens near the second photodetector, thereby sealing the light chamber.

7. The particle counter according to claim 1, characterized in that, The photoelectric detection device includes a first photoelectric detector and a first scattered light collection system, wherein the first scattered light collection system uses an aspherical lens to collect scattered light signals.

8. The particle counter according to claim 7, characterized in that, The first photodetector is also configured to detect the light intensity within the laser resonant cavity, and the system adjusts the current of the pump source based on the detected light intensity to keep the light intensity within the laser resonant cavity constant.

9. The particle counter according to claim 1, characterized in that, The laser crystal is surrounded by indium foil.

10. A particle counter, characterized in that, include: A pump source, configured to emit a first wavelength of laser light; A laser resonant cavity is formed by a plano-concave cylindrical mirror and a plano-concave mirror. The concave surface of the plano-concave cylindrical mirror faces the laser resonant cavity. The first wavelength laser enters the laser resonant cavity through the plano-concave cylindrical mirror. A laser crystal is disposed within the laser resonant cavity, and the laser crystal is configured to generate a second wavelength laser when irradiated by a first wavelength laser, the second wavelength laser generating optical oscillation within the laser resonant cavity; An aerosol generator is configured to provide an aerosol gas flow into the laser resonant cavity, the aerosol gas flow passing through a beam of a second wavelength laser. A photoelectric detection device configured to detect the scattered light signal from aerosol particles.

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