Laser particulate sensor

Abstract

This invention discloses a laser particulate matter sensor, including a reflection module comprising multiple reflectors. A first beam emitted from a laser source intersects with a gas path, the intersection area being a measurement-sensitive region. The first beam is reflected by the reflection module to form a second beam, which passes through the measurement-sensitive region. A photoelectric conversion unit comprises multiple photoelectric conversion units for detecting the scattered signals of the first or second beam. This invention achieves simultaneous acquisition of both vertical and forward signals, and doubles the amount of vertical and forward scattered signals. It significantly improves the detection accuracy of the laser particulate matter sensor for PM2.5 and can effectively identify the concentration of large particles such as PM10, providing high-precision detection results.

Description

Technical Field

[0001] This invention relates to a laser particulate sensor. Background Technology

[0002] Laser particulate matter sensors are used to detect the concentration of particulate matter in the air and are widely used in consumer products such as air purifiers, air conditioners, fresh air systems, smart homes, air quality testing equipment, particulate matter detectors, and in-vehicle air purifiers.

[0003] The composition of particulate matter in the atmosphere is very complex, and its physical properties (substance type, volume, density, shape, surface roughness, reflectivity, etc.) are also quite complex. Among the existing technologies, the most accurate and traceable standard method for measuring the mass concentration of atmospheric particulate matter (aerosol) is the gravimetric method. Any professional-grade instrument is calibrated for the gravimetric method.

[0004] The biggest advantage of the gravimetric method is that it perfectly avoids certain difficult-to-determine physical properties of substances, directly collects a unit volume sample for weighing, and is simple and accurate; however, its disadvantages are also obvious: the equipment is complex and expensive, it cannot monitor in real time, and can only detect the mass concentration of particulate matter in the air at a certain time period.

[0005] Based on the aforementioned shortcomings of the weighing method and the need for real-time monitoring in practical applications, the mainstream detection technology that has emerged is a variety of detection devices developed based on the principle of light scattering, such as various existing laser particulate matter sensors. The principle of these sensors is mainly to calculate the particulate matter mass concentration based on the intensity of the scattered light when the particles pass through the optical path. This is currently the only in-situ method for measuring particulate matter mass concentration, and it is also the particulate matter mass concentration measurement method with the best real-time performance.

[0006] like Figure 1 As shown, existing laser sensor technology includes a laser source 11, a duct perpendicular to or intersecting it, a photoelectric conversion unit 12, and a back-end circuit processing unit. Since the concentration of small particulate matter in indoor air is sufficient, the sample size of the scattered signal meets the analytical requirements. Therefore, the above technology can collect the scattered signal and then perform complex calculations and calibration to obtain the PM2.5 concentration value. However, because large particles are easily settled, their content is much lower than that of small particles, and the sample size of the scattered signal cannot meet the analytical requirements, thus failing to obtain the concentration values ​​of large particles such as PM10.

[0007] According to Mie theory, as particle size increases, scattered light gradually concentrates forward. Existing laser sensors are often single-channel and arranged at 90°. Although this helps in the detection of PM2.5, it will lead to an underestimation of the scattered light from large particles, resulting in the inability to effectively detect the concentration of large particles such as PM10.

[0008] Due to the aforementioned shortcomings, existing laser particulate matter sensors cannot effectively capture and identify signals of large particulate matter such as PM10, thus failing to accurately output the concentration of large particulate matter such as PM10. Summary of the Invention

[0009] In view of this, the present invention proposes a laser particulate matter sensor, which improves the detection accuracy of laser particulate matter sensors, especially for the detection of large particulate matter concentrations, and is effective and accurate.

[0010] The present invention adopts the following technical solution: a laser particulate sensor for detecting particulate matter in a gas path, comprising a photoelectric conversion unit, a laser source, and a reflection module, wherein the reflection module comprises multiple reflectors, wherein: a first beam emitted by the laser source intersects with the gas path, and the intersection area is a measurement sensitive area; the first beam is reflected by the reflection module to form a second beam, and the second beam passes through the measurement sensitive area; there are multiple photoelectric conversion units, and the photoelectric conversion units are used to detect the scattering signals of the first beam and the second beam.

[0011] Optionally, there are two reflectors. The reflection module includes a first reflector and a second reflector, wherein the first reflector is located in front of the first beam emitted by the laser source, and the second reflector is located to the side of the first beam emitted by the laser source. The first beam is reflected sequentially by the first and second reflectors, and the resulting second beam passes through the measurement sensitive area. The photoelectric conversion unit includes a first photoelectric conversion unit and a second photoelectric conversion unit, wherein the first photoelectric conversion unit is used to detect the vertical scattering signal of the first beam and the forward scattering signal of the second beam, and the second photoelectric conversion unit is used to detect the vertical scattering signal of the second beam and the forward scattering signal of the first beam.

[0012] Optionally, the incident angle of the first beam entering the first reflecting mirror is 22.5°.

[0013] Optionally, the laser source, the first photoelectric conversion unit, the second photoelectric conversion unit, the first reflector, and the second reflector are located on the same plane and perpendicular to the gas path.

[0014] Optionally, within the plane, the second reflector is located on one side of the first beam, and the first photoelectric conversion unit and the second photoelectric conversion unit are located on the other side of the first beam.

[0015] Optionally, there are three reflectors, and the reflection module includes a third reflector, a fourth reflector, and a fifth reflector, wherein:

[0016] The third reflecting mirror is located in front of the first beam emitted by the laser source, the fourth reflecting mirror is located on one side of the mirror surface of the third reflecting mirror, and the fifth reflecting mirror is located on one side of the mirror surface of the fourth reflecting mirror. After the first beam is reflected in sequence by the third, fourth and fifth reflecting mirrors, the second beam formed passes through the measurement sensitive area.

[0017] The photoelectric conversion unit includes a third photoelectric conversion unit and a fourth photoelectric conversion unit, wherein the third photoelectric conversion unit is used to detect the vertical scattering signal of the first beam and the forward scattering signal of the second beam, and the fourth photoelectric conversion unit is used to detect the vertical scattering signal of the second beam and the forward scattering signal of the first beam.

[0018] Optionally, the incident angle of the first beam entering the third reflector is 45°; the exit angle of the second beam exiting the fifth reflector is 22.5°.

[0019] Optionally, the laser source, the third photoelectric conversion unit, the fourth photoelectric conversion unit, the third reflector, the fourth reflector, and the fifth reflector are located in the same plane and perpendicular to the gas path.

[0020] Optionally, within the plane, the fourth reflector, the fifth reflector, and the fourth photoelectric conversion unit are located on one side of the first beam, and the third photoelectric conversion unit is located on the other side of the first beam.

[0021] Optionally, the distance between the plurality of photoelectric conversion units and the measurement sensitive area is equal.

[0022] According to the technical solution of the present invention, the laser particulate sensor includes a photoelectric conversion unit, a laser source, and a reflection module. A first beam emitted from the laser source is reflected by the reflection module to form a second beam, which then passes through the measurement sensitive area. Compared with the original technology, which had a single signal and low signal quantity, the present invention achieves simultaneous acquisition of both vertical and forward signals, and doubles the amount of vertical and forward scattered signals. This greatly improves the detection accuracy of the laser particulate sensor for PM2.5 and can effectively identify the concentration of large particles such as PM10, providing high-precision detection results. Attached Figure Description

[0023] For illustrative and not limiting purposes, the invention will now be described with reference to preferred embodiments thereof, particularly the accompanying drawings, in which:

[0024] Figure 1 This is a schematic diagram of an existing laser particulate sensor;

[0025] Figure 2 This is a schematic diagram of the structure of the laser particulate sensor of the present invention;

[0026] Figure 3This is a schematic diagram of the structure of the laser particulate sensor according to Embodiment 1 of the present invention;

[0027] Figure 4 This is a schematic diagram of the structure of the laser particulate sensor in Embodiment 2 of the present invention.

[0028] In the diagram, 11-laser source, 12-photoelectric conversion unit, 13-first beam, 21-laser source, 22-first photoelectric conversion unit, 23-second photoelectric conversion unit, 24-first reflector, 25-second reflector, 26-first beam, 27-second beam, 28-normal of the first reflector, 29-reflection module, 30-third reflector, 31-fourth reflector, 32-fifth reflector, 33-third photoelectric conversion unit, 34-fourth photoelectric conversion unit. Detailed Implementation

[0029] In this embodiment of the invention, the detection accuracy of the laser particulate sensor is improved by special design of the light beam and the corresponding photoelectric conversion unit. In particular, it is effective and accurate in detecting the concentration of large particulate matter, and can provide the concentration values ​​of PM2.5 and large particulate matter at the same time. The following is a detailed explanation.

[0030] like Figure 2 As shown, this invention discloses a laser particulate sensor for detecting particulate matter in a gas path, comprising a photoelectric conversion unit, a laser source 21, and a reflection module 29. The reflection module 29 includes multiple reflectors, wherein: a first beam 26 emitted by the laser source 21 (beam direction as shown by the arrow in the figure) intersects with the gas path, and the intersection area is the measurement sensitive area; after the first beam 26 is reflected by the reflection module 29, a second beam 27 is formed, and the second beam 27 passes through the measurement sensitive area; multiple photoelectric conversion units are used to detect the scattering signals of the first beam 26 and the second beam 27.

[0031] The photoelectric conversion unit preferably detects the vertical scattering signal of one beam and the forward scattering signal of the other beam.

[0032] Example 1

[0033] like Figure 3 As shown in the figure, an embodiment of the present invention discloses a laser particulate sensor, including a photoelectric conversion unit, a laser source 21 and a reflection module 29. The reflection module 29 includes two reflectors, wherein the first beam 26 emitted by the laser source 21 (the beam direction is shown by the arrow in the figure) intersects with the gas path, and the intersection area is the measurement sensitive area.

[0034] The first reflector 24 is located in front of the first beam 26 emitted by the laser source 21, and the second reflector 25 is located to the side of the first beam 26 emitted by the laser source 21. After the first beam 26 is reflected by the first reflector 24 and the second reflector 25 in sequence, the second beam 27 formed passes through the measurement sensitive area.

[0035] The photoelectric conversion unit includes a first photoelectric conversion unit 22 and a second photoelectric conversion unit 23. The first photoelectric conversion unit 22 is used to detect the vertical scattering signal of the first beam 26 and the forward scattering signal of the second beam 27. The forward direction refers to the direction of the second beam 27 and is located in front of the plane perpendicular to the second beam 27 through the measurement sensitive area, that is, the angle between the line connecting the measurement sensitive area and the first photoelectric conversion unit 22 and the second beam 27 is greater than 90°. The second photoelectric conversion unit 23 is used to detect the vertical scattering signal of the second beam 27 and the forward scattering signal of the first beam 26.

[0036] The incident angle of the first beam 26 entering the first reflecting mirror 24 is 22.5°, and 28 is the normal of the first reflecting mirror.

[0037] The laser source 21, the first photoelectric conversion unit 22, the second photoelectric conversion unit 23, the first reflector 24, and the second reflector 25 are located in the same plane and perpendicular to the gas path. The laser source, photoelectric conversion module, and reflector are all solid objects with volume; the reflector is sheet-like, and the photosensitive surface of the photoelectric conversion unit is also sheet-like. "In the same plane" means that the centers of all components are located in the same plane. Both the first beam 26 and the second beam 27 are perpendicular to the gas path. Being located in the same plane is a preferred embodiment of this invention, but the invention is not limited to this.

[0038] Within the aforementioned plane, the second reflector 25 is located on one side of the first beam 26, and the first photoelectric conversion unit 22 and the second photoelectric conversion unit 23 are located on the other side of the first beam 26.

[0039] In this embodiment of the invention, the first photoelectric conversion unit 22 is located directly below the intersection sensitive area, with its normal forming a 90° angle with the first beam 26. The second photoelectric conversion unit 23 is located forward and downward of the first beam 26, with its normal forming a 45° angle with the first beam 26. The first reflector 24 is located directly in front of the first beam 26, and the second reflector 25 is located forward and upward of the first beam 26, parallel to the first beam 26. After passing through the first reflector 24 and the second reflector 25, the first beam 26 is reflected into a second beam 27 forming a 45° angle with the original first beam 26. The normal of the second photoelectric conversion unit 23 forms a 90° angle with the second beam 27, while the first photoelectric conversion unit 22 is located forward of the second beam 27, with its normal forming a 45° angle with the second beam 27.

[0040] The first photoelectric conversion unit 22 and the second photoelectric conversion unit 23 are equidistant from the measurement sensitive area.

[0041] The working principle of this invention is as follows: When the first beam 26 passes through the measurement sensitive area, the first photoelectric conversion unit 22 receives the vertically scattered signal, while the second photoelectric conversion unit 23 receives the forward-scattered signal; when the second beam 27 passes through the measurement sensitive area, the second photoelectric conversion unit 23 receives the vertically scattered signal, while the first photoelectric conversion unit 22 receives the forward-scattered signal. Therefore, compared with the original technology, which has a single signal and a small signal quantity, this invention achieves simultaneous collection of both vertical and forward signals, and doubles the amount of vertical and forward scattered signals. Since the vertical signal is correlated with PM2.5 and the forward signal is correlated with large particulate matter, the amount of collected signal samples meets the detection conditions, enabling high-precision detection results for PM2.5 and large particulate matter, and outputting the concentration values ​​of PM2.5 and large particulate matter.

[0042] Example 2

[0043] like Figure 4 As shown, this embodiment discloses another type of laser particulate sensor, including a photoelectric conversion unit, a laser source 21 and a reflection module. The reflection module includes three reflectors. The first beam 26 emitted by the laser source 21 intersects with the gas path, and the intersection area is the measurement sensitive area.

[0044] The third reflector 30 is located in front of the first beam 26 emitted by the laser source 21, the fourth reflector 31 is located on one side of the mirror surface of the third reflector 30, and the fifth reflector 32 is located on one side of the mirror surface of the fourth reflector 31. After the first beam 26 is reflected in sequence by the third reflector 30, the fourth reflector 31 and the fifth reflector 32, the second beam 27 formed passes through the measurement sensitive area.

[0045] The photoelectric conversion unit includes a third photoelectric conversion unit 33 and a fourth photoelectric conversion unit 34. The third photoelectric conversion unit 33 is used to detect the vertical scattering signal of the first beam 26 and the forward scattering signal of the second beam 27. The fourth photoelectric conversion unit 34 is used to detect the vertical scattering signal of the second beam 27 and the forward scattering signal of the first beam 26.

[0046] The first beam 26 enters the third reflector 30 at an incident angle of 45°; the second beam 27 exits from the fifth reflector 32 at an exit angle of 22.5°.

[0047] The laser source 21, the third photoelectric conversion unit 33, the fourth photoelectric conversion unit 34, the third reflector 30, the fourth reflector 31 and the fifth reflector 32 are located on the same plane and are perpendicular to the gas path.

[0048] Within the aforementioned plane, the fourth reflector 31, the fifth reflector 32, and the fourth photoelectric conversion unit 34 are located on one side of the first beam 26, while the third photoelectric conversion unit 33 is located on the other side of the first beam 26.

[0049] The third photoelectric conversion unit 33 and the fourth photoelectric conversion unit 34 are equidistant from the measurement sensitive area.

[0050] This invention addresses the shortcomings of existing laser particulate matter sensors, such as low detection accuracy and inability to effectively identify large particles. It innovatively designs the beam and corresponding photoelectric conversion unit, which helps to improve the detection accuracy of laser particulate matter sensors for PM2.5 and can effectively identify the concentration of large particles such as PM10, providing high-precision detection results.

[0051] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A laser particulate sensor for detecting particulate matter in a gas path, comprising a photoelectric conversion unit and a laser source (21), characterized in that, The laser particulate sensor further includes a reflection module (29), which comprises multiple reflectors, wherein: The first beam (26) emitted by the laser source (21) intersects with the gas path, and the intersection area is the measurement sensitive area; The first beam (26) is reflected by the reflection module (29) to form a second beam (27), and the second beam (27) passes through the measurement sensitive area; Multiple photoelectric conversion units are used to detect the scattering signals of the first beam (26) and the second beam (27). One of the photoelectric conversion units is used to detect the vertical scattering signal of the first beam (26) and the forward scattering signal of the second beam (27), and the other of the photoelectric conversion units is used to detect the vertical scattering signal of the second beam (27) and the forward scattering signal of the first beam (26).

2. The laser particulate sensor according to claim 1, characterized in that, There are two reflectors, and the reflection module (29) includes a first reflector (24) and a second reflector (25), wherein: The first reflector (24) is located in front of the first beam (26) emitted by the laser source (21), and the second reflector (25) is located to the side of the first beam (26) emitted by the laser source (21). After the first beam (26) is reflected by the first reflector (24) and the second reflector (25) in sequence, the second beam (27) formed passes through the measurement sensitive area. The photoelectric conversion unit includes a first photoelectric conversion unit (22) and a second photoelectric conversion unit (23), wherein the first photoelectric conversion unit (22) is used to detect the vertical scattering signal of the first beam (26) and the forward scattering signal of the second beam (27), and the second photoelectric conversion unit (23) is used to detect the vertical scattering signal of the second beam (27) and the forward scattering signal of the first beam (26).

3. The laser particulate sensor according to claim 2, characterized in that, The incident angle of the first beam (26) entering the first reflector (24) is 22.5°.

4. The laser particulate sensor according to claim 2 or 3, characterized in that, The laser source (21), the first photoelectric conversion unit (22), the second photoelectric conversion unit (23), the first reflector (24), and the second reflector (25) are located on the same plane and are perpendicular to the gas path.

5. The laser particulate sensor according to claim 4, characterized in that, In the plane, the second reflector (25) is located on one side of the first beam (26), and the first photoelectric conversion unit (22) and the second photoelectric conversion unit (23) are located on the other side of the first beam (26).

6. The laser particulate sensor according to claim 1, characterized in that, The reflector is three in number, and the reflective module includes a third reflector (30), a fourth reflector (31), and a fifth reflector (32), wherein: The third reflector (30) is located in front of the first beam (26) emitted by the laser source (21), the fourth reflector (31) is located on one side of the mirror surface of the third reflector (30), and the fifth reflector (32) is located on one side of the mirror surface of the fourth reflector (31). After the first beam (26) is reflected in sequence by the third reflector (30), the fourth reflector (31) and the fifth reflector (32), the second beam (27) formed passes through the measurement sensitive area. The photoelectric conversion unit includes a third photoelectric conversion unit (33) and a fourth photoelectric conversion unit (34), wherein the third photoelectric conversion unit (33) is used to detect the vertical scattering signal of the first beam (26) and the forward scattering signal of the second beam (27), and the fourth photoelectric conversion unit (34) is used to detect the vertical scattering signal of the second beam (27) and the forward scattering signal of the first beam (26).

7. The laser particulate sensor according to claim 6, characterized in that, The incident angle of the first beam (26) entering the third reflecting mirror (30) is 45°; The second beam (27) exits from the fifth reflector (32) at an angle of 22.5°.

8. The laser particulate sensor according to claim 6 or 7, characterized in that, The laser source (21), the third photoelectric conversion unit (33), the fourth photoelectric conversion unit (34), the third reflector (30), the fourth reflector (31), and the fifth reflector (32) are located on the same plane and are perpendicular to the gas path.

9. The laser particulate sensor according to claim 8, characterized in that, Within the plane, the fourth reflector (31), the fifth reflector (32), and the fourth photoelectric conversion unit (34) are located on one side of the first beam (26), and the third photoelectric conversion unit (33) is located on the other side of the first beam (26).

10. The laser particulate sensor according to any one of claims 1-9, characterized in that, The distances between the multiple photoelectric conversion units and the measurement sensitive area are equal.

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