Particle counter

Abstract

The utility model relates to a particle counter, which comprises a scattering cavity, a light source cavity, an air inlet pipe, an air outlet pipe, a reflecting mirror, a photodiode, a light filtering hole, a light trap and the like. A laser in the light source cavity shapes laser beams through an aspherical lens and a cylindrical lens, and the laser beams are scattered with gas particles through the scattering cavity. The vertical scattered light is reflected to the photodiode by the reflector, is converted into an electric signal, is amplified, is collected to a computer through a collection card, and is processed and counted through an upper computer program. The filter hole and the light trap absorb stray light, and noise interference is reduced. The air inlet pipe adopts a sheath flow device structure, particle beam width is reduced, and counting precision is improved. The photoelectric detector adopts a high-sensitivity photodiode, and meanwhile collection and detection of scattered light are optimized. And an upper computer program judges the corresponding particle size by screening and comparing the voltage amplitudes and performs counting, so that the counting efficiency and the counting precision are improved. Corrosion-resistant materials are designed and selected, a dustproof and moistureproof structure is added, and durability and stability of equipment are ensured. The particle counter is suitable for the fields of laboratories, industrial sites and medical treatment and public health, has the advantages of miniaturization, portability, low cost, easiness in maintenance and the like, can monitor the concentration of particulate matters in the environment in real time, and ensures the cleanliness of production and medical treatment and public health environments. Through a counting system of an upper computer program and an optimized optical and gas circuit structure, the detection efficiency and precision are remarkably improved, and wide application prospects are achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the related technical field of optical particle detection, more accurately, it relates to a particle counter. BACKGROUND

[0002] The particle counter is used for measuring the number and particle size distribution of dust particles in a unit volume in a clean environment, and is widely applied to authoritative institutions such as drug testing offices, blood centers, epidemic prevention stations, disease control centers, quality supervision offices, and production enterprises and scientific research departments such as electronic industry, pharmaceutical workshop, semiconductor, optics or precision machinery processing, plastic, paint spraying, hospital, environmental protection, testing office, etc. Laser air particle counter has become the mainstream product of multiple industries due to its fast test speed, wide dynamic distribution, and no influence of human factors.

[0003] The particle counter is an instrument for counting particles by using light scattering principle. Its working principle is that a particle passes through a strong light, the particle emits scattered light, the scattered light is reflected to a photoelectric detector through a condenser mirror, the light pulse is converted into an electric pulse, and the particle number is calculated through the pulse number. The existing particle counter mainly includes optical structure, air sampling structure, scattered light collection structure, signal acquisition module, and accommodates these modules in a cavity.

[0004] The existing particle counter is mostly large in size, not suitable for complex and changeable scenes, and needs to be miniaturized. In addition, when the particle concentration measured is too high, multiple particles pass through the light sensitive area at the same time, which will cause overlapping phenomenon, and be regarded as a particle, resulting in counting omission. Moreover, the light sensitive area of the particle counter is easily affected by stray light generated by laser reflection of the inner wall, thereby affecting the counting accuracy.

[0005] The traditional particle counter adopts a comparison circuit to screen the pulse signal voltage amplitude, and counts through an FPGA or STM32 module. The hardware design process is complex and tedious, and the existence of these hardware makes the structure of the counter more bloated and inconvenient for subsequent particle counter correction and modification. UTILITY MODEL CONTENTS

[0006] The utility model aims at providing a particle counter, which adopts a modular structure, improves each structure, reduces the number of parts, realizes miniaturization design of the particle counter, improves the stability of the air path, reduces the overlap rate of the particles to be measured, and improves the detection accuracy of the particle counter.

[0007] In order to solve the above problems, the utility model discloses a particle counter, include: for output laser beam's laser, set up on the light beam transmission path's shaping lens and scattering cavity. Shaping lens combines aspheric mirror and cylindrical lens, can adjust the divergency of different optical axis direction, make the light spot intensity and size modulation of light beam in photosensitive area to reasonable range. Scattering cavity is equipped with air inlet pipe, air outlet pipe, reflector, photodetector, optical filter hole, optical trap and acquisition card, wherein, the measured air flow passes through air inlet pipe and enters scattering cavity, and is discharged from air outlet pipe, optical filter hole carries out optical filter processing to the laser produced by laser, reduces the reflection of stray light in the cavity, reduces noise signal, improves the counting accuracy. Reflector and photodetector are used for reflecting and receiving respectively the vertical direction scattered light produced by the interaction of the light beam entering the scattering cavity and the measured air flow, and the horizontal direction laser after gas path scattering is shot into optical trap, avoids the influence of the excessive stray light on the result of detector. Acquisition card gathers the electric signal produced by photodetector into host computer program.

[0008] Laser, optical trap, reflector, photodetector, air inlet pipe, air outlet pipe six devices are connected to the six faces of scattering cavity through six through holes. The two faces of laser and optical trap coaxial constitute the incidence structure and stray light absorption mechanism of laser, and the two faces of air inlet pipe and air outlet pipe coaxial constitute the gas path structure of counter, and the two faces of reflector and photodetector coaxial constitute the collection structure of scattered light.

[0009] In addition to laser emitter, light shaping mirror and light detection piece inside particle counter, the rest surface is provided with light absorption layer, so that the influence of stray light on measurement result is reduced to the maximum extent.

[0010] The air inlet pipe is an air inlet pipe structure containing a sheath flow device, and the sheath gas is introduced into the left and right sides of the measured gas to reduce the beam waist width of the particle beam, thereby reducing the situation that multiple particles pass through the laser photosensitive area at the same time and improving the overall counting efficiency of the system. The air inlet pipe is connected to the scattering cavity from the air inlet hole, and the air outlet pipe is connected to the scattering cavity from the air outlet hole.

[0011] The reflector is located in the bottom through hole of the scattering cavity, and the reflector is fixed below the reflector bottom cover. The bottom through hole is a stepped hole, and the reflector and the reflector cover are embedded and positioned in the bottom through hole.

[0012] The photodetector is a photodiode, located in the top through hole of the scattering cavity, and the sensor fixing structure is arranged above the photodetector to fix the sensor and ensure the air tightness of the scattering cavity. The pins of the photodiode are connected to the acquisition card outside the scattering cavity through a preamplifier circuit. The channel of the photodiode receiving scattered light is designed to be lengthened. The purpose of the lengthening design is to reduce the stray light received by the photodiode into the photosensitive cavity, reduce the background noise in the signal, and improve the signal-to-noise ratio.

[0013] The signal processing is mainly completed by the host computer program, after the host computer program receives the pulse electric signal of the scattered light, the pulse electric signal is divided according to the voltage amplitude, the scattered light signals of particles of different particle sizes corresponding to different voltage amplitudes are generated, and the number of particles of the corresponding particle size can be counted by counting the signals of different voltage amplitudes. The particle counter can also be conveniently corrected by modifying the threshold value of the screening voltage signal. Finally, the counting result of the particles and the pulse signal waveform diagram are output.

[0014] The laser generated by the laser is irradiated into the scattering cavity through the front-end through hole after the shaping lens, after the scattering of the particles in the scattering cavity and the gas path, the remaining light is irradiated into the optical trap structure of the rear-end through hole, the stray light is absorbed by the optical trap, the influence on the photodetector is avoided, so that the noise signal is reduced, and the signal-to-noise ratio is improved.

[0015] Compared with the prior art, the particle counter disclosed by the utility model reduces the stray light in the particle laser through the design of the light filtering hole, the optical trap cavity, the optical trap cone, the extended scattered light channel and the light absorption coating on the inner wall of the light sensitive area, reduces the background noise generated by the stray light, improves the signal-to-noise ratio, and improves the detection accuracy of the particle counter. The gas flow beam waist width entering the scattering cavity is reduced by adopting the sheath flow device, the gas flow rate is reduced, the scattering of multiple particles by laser is reduced, the signal overlap interference is reduced, the counting error is reduced, and the counting accuracy of the particle counter is improved. In addition, the particle counting mode is optimized from hardware counting to software counting, the counting efficiency of the particle counter is improved, the structure design of the particle counter is simplified, the cost is reduced, and the particle counter can be applied to more complex scenes.

[0016] The particle counter of the utility model not only can improve the detection accuracy and efficiency, but also has the advantages of simple structure, low cost, easy maintenance and the like. In practical application, it can adapt to various complex environments, meet the needs of different users, and has wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical scheme of the embodiments of the utility model or the prior art, the drawings required to be used in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the utility model, and those skilled in the art can also obtain other drawings according to these drawings without creating creative labor.

[0018] Figure 1 The utility model provides a kind of particle counter's split structure schematic diagram.

[0019] Figure 2 The utility model provides a kind of optical path profile structure schematic diagram of particle counter.

[0020] Figure 3 A particle counter's gas path profile structure schematic view is provided.

[0021] Figure 4 A particle counter's stray light elimination system structure schematic view is provided.

[0022] Figure 5 A particle counter's sheath flow device air inlet pipe structure schematic view is provided.

[0023] As Figures 1-5 shown, a particle counter of the present application comprises a scattering cavity 1, a light source cavity 2, an air inlet pipe 3, a sampling tube air inlet 4, an air outlet pipe 5, a mirror base 6, a detector base 7, a light trap cavity 8, a light trap cone 9, a photodiode 10, a mirror 11, and a light filter hole 12; wherein the sampling tube air inlet 4 comprises a sheath gas air inlet 41, a sheath gas air inlet 43, and a sample gas air inlet 42. The air inlet pipe 3 comprises an air inlet 31. The light source cavity 2 comprises an aspheric lens 23 and a cylindrical lens 24. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0025] Specifically, as Figure 2 shown, the laser from the light source cavity 2 is shaped by the aspheric lens 23 and the cylindrical lens 24 and then reaches the scattering cavity 1, where it has a scattering reaction with the particles in the gas from the air inlet 31. The generated vertical direction scattering light is focused on the photodiode 10 by the mirror 11, the photodiode converts the light signal into an electric signal, and sends the electric signal to the subsequent signal processing circuit and counting system. The horizontal direction transmission light and scattering light are injected into the light trap cavity 8, the light filter hole 12 and the light trap absorb the stray light, thereby reducing the noise signal received by the photodiode 10.

[0026] Specifically, the light source cavity 2, the light trap cavity 8, the mirror 11, the photodiode 10, the air inlet pipe 3, and the air outlet pipe 5 are connected to the six faces of the scattering cavity 1 through six through holes respectively. The two faces of the laser and the light trap coaxial constitute the incidence structure and stray light absorption structure of the laser, the two faces of the air inlet pipe and the air outlet pipe coaxial constitute the gas path structure of the counter, and the two faces of the mirror and the photodetector coaxial constitute the collection structure of the scattering light.

[0027] Specifically, as shown in Figure 4 The filter hole 12, the light trap cavity 8, the light trap cone 9 and the sensor fixing structure 7 constitute a stray light elimination system of the system, the filter hole 12 filters the laser generated by the laser in the forward direction through the trapezoidal structure, avoids irradiating the cavity wall to generate redundant stray light, the front trapezoidal structure of the light trap cavity 8 is the same as the filter hole, and the reflection of the stray light in the cavity wall is avoided. The rear end structure combines the light trap cone 9, absorbs the directly incoming laser, avoids reflecting the noise signal interference back to the light sensitive area, greatly reduces the background noise of the photodiode signal, and improves the counting efficiency of the particle counter as a whole. In addition, the light absorption layer is arranged on the surface of the shell except the light emitter, the light shaping mirror and the light detection part.

[0028] Specifically, as shown in Figure 5 The gas inlet pipe 3 is a gas inlet pipe structure with a sheath flow device, and the sheath gas is introduced into the left and right sides of the measured gas, so that the beam waist width of the particle beam is reduced, the situation that multiple particles pass through the laser light sensitive area at the same time is reduced, and the overall counting efficiency of the system is improved. The gas inlet pipe 3 is connected to the scattering cavity 1 from the gas inlet hole, and the gas outlet pipe 5 is connected to the scattering cavity 1 from the gas outlet hole. The reflector 11 is located in the bottom hole of the scattering cavity, and the reflector bottom cover is fixed below. The bottom hole is a stepped hole, and the reflector and the reflector cover are embedded and positioned in the bottom hole.

[0029] The photodetector is a photodiode 10 located in the top hole of the scattering cavity. The sensor fixing structure is arranged above the photodetector, the sensor is fixed, and the air tightness of the scattering cavity is ensured. The pins of the photodiode are connected to the acquisition card outside the scattering cavity through the preamplifier circuit.

[0030] Compared with the prior art, the particle counter disclosed by the utility model reduces the stray light in the particle laser through the design of the filter hole, the light trap cavity, the light trap cone, the extended scattering light channel and the light absorption coating on the inner wall of the light sensitive area, reduces the background noise generated by the stray light, improves the signal-to-noise ratio, and thus improves the detection accuracy of the particle counter. The particle counter disclosed by the utility model adopts a sheath flow device at the gas inlet, so that the beam waist width of the gas flow entering the scattering cavity is reduced, the gas flow rate is reduced, the scattering of multiple particles through the laser at the same time is reduced, the counting error caused by the signal overlapping interference is reduced, and the technical efficiency and accuracy of the particle counter are improved. In addition, the miniaturized design of the particle counter also reduces the cost, and can be applied to more complex scenes.

[0031] In the design of the scattering cavity, in order to further improve the performance of the particle counter, the optimized optical structure and air path structure are adopted. First, the aspheric lens 23 and the cylindrical lens 24 in the light source cavity 2 can not only adjust the divergence of the light beam, but also can keep the best spot shape when the light beam passes through the scattering cavity 1, thereby improving the intensity and detection accuracy of the scattering signal.

[0032] In addition, the arrangement of the reflector 11 and the photodetector 10 is also optimized and designed. The reflector 11 is a concave spherical reflector made of high reflectivity material. The curvature radius of the concave spherical mirror can be obtained through the imaging conjugate position calculation formula of the concave spherical mirror and the distance from the reflector to the photosensitive area and the photodiode, so that the scattered light can be reflected to the photodetector 10 to the maximum extent, thereby improving the intensity of the scattering signal. The photodetector 10 selects a high-sensitivity photodiode, which can convert weak light signals into electrical signals, thereby realizing high-precision particle counting.

[0033] The signal processing is mainly completed by the host computer program. After the host computer program receives the pulsed electrical signal of the scattered light, the pulsed electrical signal is divided according to the voltage amplitude. Different voltage amplitudes correspond to the scattering light signals generated by particles of different particle sizes. By counting the signals of different voltage amplitudes, the number of particles of corresponding particle size can be counted. The particle counter can also be easily corrected by modifying the threshold value of the screening voltage signal. Finally, the counting result of the particles and the pulse signal waveform diagram are output.

[0034] In order to ensure the reliability and stability of the particle counter, the utility model also considers multiple factors in the design process. For example, in the manufacturing material of the scattering cavity 1, high-strength and corrosion-resistant materials are selected to ensure the durability and stability of the equipment in long-term use. Dustproof and moisture-proof structure is also provided to prevent the influence of the external environment on the particle counter.

[0035] In summary, the particle counter of the utility model adopts modular design and optimized optical and air path structure, which not only improves the detection accuracy and efficiency, but also has the advantages of simple structure, low cost, easy maintenance and wide application prospect.

Claims

1. A particle counter, characterized by, The application relates to a laser particle counter. The laser particle counter comprises a laser for outputting a laser beam, a shaping lens arranged on a beam transmission path, the shaping lens being a non-spherical lens and a cylindrical lens, capable of adjusting the divergence of different optical axes, so that the spot intensity and size of the laser beam in a photosensitive area are modulated to a reasonable range, a scattering cavity provided with an air inlet pipe, an air outlet pipe, a reflecting mirror, a photoelectric detector and a light trap, wherein the air inlet pipe is used for guiding the measured air flow into the scattering cavity, the air outlet pipe is used for discharging the measured air flow, the reflecting mirror is used for reflecting the vertical direction scattered light generated by the interaction between the laser beam entering the scattering cavity and the measured air flow, the photoelectric detector is used for receiving the vertical direction scattered light reflected by the reflecting mirror, a light filtering hole is used for filtering stray light before the stray light is incident on the photosensitive area, and the light trap is used for capturing the horizontal direction laser to avoid the influence of the redundant stray light on the photoelectric detector. The shaping lens can control the spot intensity and size of the laser beam in the photosensitive area by adjusting the relative position of the shaping lens and the laser.

2. The particle counter of claim 1, wherein, The inner wall of the scattering cavity is made of light-absorbing material to reduce the interference of light reflection on the measurement results.

3. The particle counter of claim 1, wherein, The laser is a semiconductor laser capable of stably outputting a laser beam of a specific wavelength.

4. The particle counter of claim 1, wherein, The photoelectric detector is a high-sensitivity photodiode capable of accurately detecting a weak scattered light signal.

5. The particle counter of claim 1, wherein, The air inlet pipe is provided with a sheath flow device, and sheath gas is introduced on the left and right sides of the measured gas, so that the beam waist width of the particle beam is reduced, the situation that multiple particles pass through the laser photosensitive area at the same time is reduced, and the overall counting efficiency of the system is improved.

6. The particle counter of claim 1, wherein, The light trap and the light filtering hole are made of light-absorbing material and can efficiently absorb the incident stray laser.

7. The particle counter of claim 1, wherein, ​

Images