Biological aerosol monitoring apparatus and monitoring method

Abstract

A biological aerosol monitoring apparatus, comprising a light path, a gas path and a signal processing system, wherein the light path comprises a laser irradiation light path configured to irradiate particles to be tested, a scattered light collection light path configured to receive scattered light signals, and a fluorescence collection light path configured to receive fluorescence signals. A focal point (M) of an excitation light source (101) configured to irradiate said particles is located before or behind a photosensitive area (G) on an optical axis of the laser irradiation light path, such that the cross section of an excitation light spot in the photosensitive area (G) that is perpendicular to the optical axis of the laser irradiation light path is a rectangular shape, and when a single aerosol particle passes through the photosensitive area (G), the single aerosol particle is continuously irradiated by excitation light to obtain an intrinsic fluorescence bleaching speed. Information such as an intrinsic fluorescence bleaching speed, a scattered light peak value and a relative fluorescence intensity of aerosol particles is integrated, such that preliminary classification of biological particles is realized, instrument alerts caused by non-target microorganisms are significantly reduced, and the capability of an instrument for identifying the types of biological aerosols is improved, thereby reducing the frequency and cost of subsequent biological detection.

Description

Bioaerosol monitoring device and monitoring method Technical Field

[0001] The present invention relates to real-time monitoring of bioaerosols, and in particular to a bioaerosol monitoring device and a monitoring method. Background Art

[0002] Real-time monitoring of bioaerosols has important applications. Excitation light-induced intrinsic fluorescence detection technology offers significant advantages in real-time bioaerosol monitoring due to its rapid speed, high sensitivity, lack of consumables, and non-invasive nature. The technology works because bioaerosol particles contain organic molecules such as tryptophan, reduced coenzyme I (NADH), and riboflavin. These components produce intrinsic fluorescence under ultraviolet light, while non-biological aerosol particles generally lack this ability. This allows for the identification of biological aerosol particles.

[0003] However, existing technologies currently have the following major problems: First, cigarette particles, kaolin, and dust containing polycyclic aromatic hydrocarbons in airborne particles can also generate intrinsic fluorescence signals. Most existing technologies are unable to distinguish these interferents, which may cause false detection or false alarms of the instrument; Second, there are many types of bioaerosol particles. In practical applications, it is often necessary to monitor only a few or a dozen biological targets. Most existing technologies can only monitor the total number of fluorescent particles in general and cannot classify aerosol particles. For example, pollen or some harmless microbial species do not need to be monitored. Therefore, preliminary screening of biological particles is required to reduce the frequency and cost of subsequent biological detection.

[0004] Patent document CN108375530A discloses a real-time bioaerosol detection method and device, comprising an optical path, an air path intersecting the optical path, and a signal processing system connected to the optical path. The optical path comprises a laser emission path for illuminating the particles being measured, a scattered light collection path for receiving scattered light signals, and a fluorescence collection path for receiving fluorescence signals. The air path is used to sample the particles being measured, with a minimum detection resolution of one microbial particle. The optical signal processing system, used to analyze and process the signals, includes a scattered light preamplifier and a fluorescence preamplifier. These systems can simultaneously monitor the concentration of microbial and non-microbial particles in the air. By distinguishing between microbial and non-microbial particles, they achieve real-time monitoring of the concentration and number of microbial particles in the air and improve monitoring accuracy. Patent document CN103940709 discloses a real-time microbial particle counter that determines the particle size and biological properties of the particles being measured by detecting the scattered light and fluorescence intensity emitted by individual particles under excitation light. However, the above two patent documents can only detect the peak value of scattered light pulse and fluorescence pulse, the microbial determination index is single, and the fluorescence bleaching information cannot be tested. Many interference substances are detected, and the instrument false alarm rate is high.

[0005] Patent document CN110411995A discloses a bioaerosol monitoring device and method based on intrinsic fluorescence bleaching characteristics. By detecting fluorescence bleaching information, the device distinguishes aerosol particle types based on the fluorescence bleaching characteristics. However, the instrument first enriches and samples multiple aerosol particles together, then irradiates the collected particle group for a long time to obtain the fluorescence bleaching characteristics. The disadvantages are: 1) it measures the cumulative fluorescence of multiple particles, and cannot obtain the scattered light, intrinsic fluorescence, and fluorescence bleaching characteristics of individual aerosol particles. Therefore, it is difficult to accurately determine the test results for samples containing multiple aerosol particles; 2) it requires enrichment of a certain number of aerosol particles for testing, resulting in low detection sensitivity, and the lack of real-time monitoring, resulting in a certain lag in the determination of the results.

[0006] Summary of the Invention

[0007] To address the above-mentioned existing problems, the present invention provides a bioaerosol monitoring device and method. These devices utilize the fact that the intrinsic fluorescence bleaching rates of organic molecules within bioaerosol particles differ under the same excitation light irradiation. For example, components such as riboflavin bleach faster, while components such as NADH bleach more slowly or almost not at all. By analyzing the area, amplitude, and other information of the intrinsic fluorescence pulse signals generated by aerosol particles under continuous irradiation when they pass through a light-sensitive area, combined with information such as the elastically scattered light pulse signals of the particles, characteristic information of different types of aerosol particles can be collected, providing a basis for preliminary classification of aerosol particles.

[0008] The technical solutions of the present invention are as follows:

[0009] On one hand, the present invention provides a bioaerosol monitoring device, comprising an optical path, an air path intersecting the optical path, and a signal processing system connected to the optical path; the optical path comprises a laser irradiation optical path for irradiating measured particles, a scattered light collection optical path for receiving scattered light signals, and a fluorescence collection optical path for receiving fluorescence signals; the air path is used to sample the measured particles; the signal processing system is used to analyze and process signals; the intersection area of ​​the laser irradiation optical path and the air path is a photosensitive area; the device is characterized in that the focus of the excitation light source for irradiating the measured particles is located before or after the photosensitive area on the optical axis of the laser irradiation optical path, so that the cross-section of the excitation light spot perpendicular to the optical axis of the laser irradiation optical path in the photosensitive area is rectangular, and when a single aerosol particle passes through the photosensitive area, it is continuously irradiated by the excitation light, thereby obtaining an intrinsic fluorescence bleaching rate.

[0010] Preferably, the laser irradiation light path for irradiating the measured particles includes an excitation light source, the light emitted by the excitation light source is parallel to the X-axis direction and collimated by an aspheric mirror to form a parallel beam, and then focused by a cylindrical mirror and passes through the photosensitive area to reach the light trap. In the Y-axis direction of the photosensitive area, there are a curved reflector and a dichroic mirror, and the dichroic mirror is arranged at 45 degrees to the Y-axis. The dichroic mirror has high reflectivity for elastic scattered light and high transmittance for the fluorescent band.

[0011] Preferably, the scattered light collecting optical path for receiving the scattered light signal comprises a focusing mirror, a scattering aperture and a scattered light receiver which are sequentially placed along the transmission direction of the elastic scattered light.

[0012] Preferably, the fluorescence collection optical path for receiving the fluorescence signal includes a fluorescence filter, a fluorescence focusing lens, a fluorescence diaphragm and a fluorescence receiver which are sequentially placed along the fluorescence transmission direction.

[0013] Preferably, the air circuit is composed of an air inlet nozzle, an air outlet nozzle and an air pump, and the air inlet direction of the air circuit is parallel to the Z axis and passes through the light sensitive area.

[0014] Preferably, the signal processing system includes a scattered light amplification circuit, a scattered light AD conversion circuit, a fluorescence amplification circuit, a fluorescence AD ​​conversion circuit and an FPGA circuit; the elastic scattered light pulse signal collected by the scattered light receiver is sequentially amplified by the scattered light amplification circuit, converted into a digital signal by the scattered light AD conversion circuit and reaches the FPGA circuit; the intrinsic fluorescence pulse signal collected by the fluorescence receiver is sequentially amplified by the fluorescence amplification circuit, converted into a digital signal by the fluorescence AD ​​conversion circuit and reaches the FPGA circuit, and the FPGA circuit is used to calculate the relative fluorescence intensity of the measured aerosol particles, the ratio of the scattering peak values ​​and the intrinsic fluorescence bleaching rate.

[0015] On the other hand, the present invention also provides a method for bioaerosol monitoring using the above-mentioned bioaerosol monitoring device, comprising the following steps:

[0016] S1. Construct a three-dimensional coordinate system for the peak value, relative fluorescence intensity, and intrinsic fluorescence bleaching rate of elastically scattered light pulse signals of different bioaerosol particles:

[0017] S1.1 When bioaerosol particles pass through the light-sensitive area, they stimulate elastic scattered light pulse signals and intrinsic fluorescence pulse signals, which are received by the scattered light receiver and fluorescence receiver respectively. After being processed by the signal amplification circuit and A / D conversion circuit, they are transmitted to the FPGA circuit;

[0018] S1.2 calculates the peak value h0 of the elastic scattered light pulse signal of the bioaerosol particles to be measured, the peak value h1 of the intrinsic fluorescence pulse signal, and the area s1 of the intrinsic fluorescence pulse signal through the FPGA circuit;

[0019] S1.3. Calculate the relative fluorescence intensity using the FPGA circuit, i.e., the ratio of the peak value h1 of the intrinsic fluorescence pulse signal to the peak value h0 of the elastically scattered light pulse signal;

[0020] S1.4. Calculate the intrinsic fluorescence bleaching rate using an FPGA circuit, i.e., the ratio of the area s1 of the intrinsic fluorescence pulse signal to the peak h1 of the intrinsic fluorescence pulse signal;

[0021] S1.5 Repeat steps S1.1-S1.4 using different bioaerosol particles to construct a three-dimensional coordinate system for the peak value, relative fluorescence intensity, and intrinsic fluorescence bleaching rate of the elastically scattered light pulse signal of the different bioaerosol particles;

[0022] S2. When the bioaerosol particles to be tested pass through the photosensitive area, they stimulate elastic scattered light pulse signals and intrinsic fluorescence pulse signals, which are received by the scattered light receiver and fluorescence receiver, respectively, and transmitted to the FPGA circuit;

[0023] S3. Calculate the peak value, relative fluorescence intensity, and intrinsic fluorescence bleaching rate of the elastically scattered light pulse signal of the biological aerosol particles to be tested through the FPGA circuit, and determine the type of the aerosol particles to be tested by comparing the landing area in the three-dimensional coordinate system.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The focus of the excitation light is not located at the photosensitive area, but before or after the photosensitive area on the optical axis of the illumination light path. This makes the cross-section of the excitation light spot perpendicular to the X-axis in the photosensitive area approximately rectangular, rather than a thin line. When a single aerosol particle passes through the photosensitive area, it will be continuously irradiated by the excitation light for a period of time, and the fluorescence bleaching characteristics of the single aerosol particle can be obtained.

[0026] 2) Due to the different components of different aerosol particles, the bleaching rates of the fluorescence signal are different, and their fluorescence pulse waveforms will also be significantly different. For aerosol particles whose fluorescent components do not contain bleaching components, their fluorescence pulse waveform is approximately rectangular; for aerosol particles whose fluorescent components contain only a small amount of bleaching components, their fluorescence pulse waveform is approximately trapezoidal; for aerosol particles whose fluorescent substances are mainly bleaching components, their fluorescence pulse waveform is approximately triangular. Because the airflow velocity and the size of the illumination beam are fixed, the time it takes for an aerosol particle to pass through the photosensitive area, that is, the duration of the fluorescence pulse signal, is basically fixed. The ratio of the area to the peak value of the fluorescence pulse signal of a single aerosol particle is calculated using FPGA, reflecting the fluorescence bleaching rate of the particle.

[0027] 3) The intrinsic fluorescence bleaching rate can effectively distinguish between interfering substances and different types of bioaerosols, greatly reducing or even avoiding false detections by the instrument.

[0028] 4) By comprehensively analyzing the intrinsic fluorescence bleaching rate, scattered light peak, relative fluorescence intensity and other information of aerosol particles, preliminary classification of biological particles can be achieved, significantly reducing instrument alarms caused by non-target microorganisms, and improving the instrument's ability to identify bioaerosol types, thereby reducing the frequency and cost of subsequent biological detection.

[0029] 5) By placing a dichroic mirror in the optical path, the fluorescence signal is separated into two or more fluorescence bands, thereby obtaining a multi-channel fluorescence pulse signal. The bleaching rate of fluorescence in different bands is calculated separately, and the judgment index of aerosol particle classification is increased, thereby achieving more accurate and precise judgment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is a schematic diagram of the optical path of an embodiment of a bioaerosol monitoring device of the present invention.

[0031] FIG2 is a schematic diagram of the illumination light path and the gas path in an embodiment of the bioaerosol monitoring device of the present invention.

[0032] FIG3 is a schematic diagram of a signal processing system of an embodiment of a bioaerosol monitoring device according to the present invention.

[0033] FIG4 is a schematic diagram of the fluorescence signal pulse waveforms of aerosol particles with different bleaching rates according to the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention should not be limited thereto.

[0035] Please refer to Figures 1 and 2. Figure 1 is a schematic diagram of the optical path of an embodiment of the bioaerosol monitoring device of the present invention, and Figure 2 is a schematic diagram of the illumination optical path and the gas path in the embodiment of the bioaerosol monitoring device of the present invention. As shown in the figure, the bioaerosol monitoring device of this embodiment includes an optical path, a gas path and a signal processing system. The optical path includes an excitation light source 101. The excitation light beam emitted by the excitation light source 101 is parallel to the X-axis direction and collimated by the aspheric mirror 102 to form a parallel light beam, and then focused by the cylindrical mirror 103 and passes through the photosensitive area G to reach the light trap 105. The focus M of the excitation light beam is located between the photosensitive area G and the light trap 105 on the optical axis of the illumination light path. The cross section of the photosensitive area G perpendicular to the X-axis is approximately rectangular. In the Y-axis direction of the photosensitive area G are the curved reflectors 10 4. Photosensitive area G, dichroic mirror 106. The dichroic mirror 10 is set at 45 degrees to the Y axis. The dichroic mirror 106 has high reflectivity for elastic scattered light and high transmittance for the fluorescent band. Along the direction of elastic scattered light, there are scattered light focusing mirror 111, scattered light diaphragm 112, and scattered light receiver 113. Along the direction of fluorescence, there are fluorescent filter 107, fluorescent focusing mirror 108, fluorescent diaphragm 109, and fluorescent receiver 110. The scattered light receiver 113 and the fluorescent receiver 110 simultaneously reach the FPGA circuit (not shown) after passing through the signal amplification circuit and AD conversion circuit; the air path consists of an air inlet nozzle 201, an exhaust nozzle 20 and an air pump. The air inlet direction of the air path is parallel to the Z axis and passes through the photosensitive area G; the intersection of the illumination light path and the air path channel is the photosensitive area G.

[0036] In the XOY plane, light emitted by the excitation light source 101 is collimated by the aspheric mirror 102 to form a parallel beam. It is then focused by the cylindrical mirror 103 and passes through the photosensitive region G to the light trap 105. The focus of the excitation light is located between the photosensitive region G and the light trap 105 on the optical axis of the illumination light path. At this point, the photosensitive region has a roughly rectangular cross-section perpendicular to the X-axis. The elastically scattered light and intrinsic fluorescence (if any) generated by the excited aerosol particles passing through the photosensitive region are collected by the curved reflector 104 of the collection unit and converted into parallel light that reaches the dichroic mirror 106. The dichroic mirror 106 has high reflectivity for the elastically scattered light and high transmittance for the fluorescence wavelength range. Therefore, the elastically scattered light is reflected by the dichroic mirror 106 to the focusing mirror 111, then passes through the scattering aperture 112 to reach the scattered light receiver 113. The fluorescence is transmitted through the dichroic mirror 106, passes through the fluorescence filter 107, the focusing mirror 108, and the fluorescence aperture 109, and reaches the fluorescence receiver 110. The scattered light pulse signal obtained by the scattered light receiver 113 reaches the FPGA circuit 303 after passing through the first signal amplification circuit 301 and the first AD conversion circuit 302. The fluorescence pulse signal obtained by the fluorescence receiver 110 reaches the FPGA circuit 303 synchronously after passing through the second signal amplification circuit 304 and the second AD conversion circuit 305, as shown in Figure 3.

[0037] FIG2 is a schematic diagram showing the relative positions of the illumination optical path and the gas path. In the XOZ plane, the gas path is composed of an air inlet nozzle 201, an exhaust nozzle 202, and an air pump. The air inlet direction of the gas path is parallel to the Z axis and passes through the light-sensitive area G.

[0038] The fluorescence pulse waveforms of different aerosol particles will also be different, as shown in Figure 4. For aerosol particles whose fluorescent components do not contain bleaching components, their fluorescence pulse waveforms are approximately rectangular, as shown in Figure 4(a); for aerosol particles whose fluorescent components contain only a small amount of bleaching components, their fluorescence pulse waveforms are approximately trapezoidal, as shown in Figure 4(b); for aerosol particles whose fluorescent substances are mainly bleaching components, their fluorescence pulse waveforms are approximately triangular, as shown in Figure 4(c).

[0039] The monitoring method of the present invention is as follows:

[0040] (1) After the monitoring device is activated, the aerosol particles being measured will emit elastic scattered light pulse signals, and some particles will also emit intrinsic fluorescence pulse signals. If the measured particle only emits elastic scattered light signals, it is determined to be a non-biological particle. Otherwise, the elastic scattered light signal and intrinsic fluorescence pulse signal of the measured particle are simultaneously transferred to the FPGA circuit after passing through the weak signal amplification circuit and the AD conversion circuit. The FPGA circuit calculates the peak value h0 of the scattered pulse signal of the measured aerosol particle, the area s1 of the fluorescence pulse signal, and the peak value h1 of the fluorescence pulse signal;

[0041] (2) FPGA further calculates the relative fluorescence intensity of the aerosol particles being measured, that is, the ratio of the fluorescence peak to the scattering peak h1 / h0, and the intrinsic fluorescence bleaching rate s1 / h1.

[0042] (3) According to steps (1) and (2), the scattered light peak value h0, relative fluorescence intensity h1 / h0, and intrinsic fluorescence bleaching rate s1 / h1 of various aerosol particles that can emit intrinsic fluorescence are tested, and then a three-dimensional coordinate system is established based on these three test values, the coordinates of different types of aerosol particles are marked, and the regions corresponding to the different types of aerosol particles are divided in the coordinate system.

[0043] (4) When testing unknown fluorescent aerosol particles, the monitoring device detects and calculates the scattered light peak, relative fluorescence intensity, and intrinsic fluorescence bleaching rate of the aerosol particles being tested, thereby obtaining the landing point position of the particles being tested in the three-dimensional coordinate system, and then determining the type of the aerosol particles being tested based on the corresponding divided area in step (3) corresponding to the landing point position.

[0044] Experiments show that the present invention collects characteristic information of different types of aerosol particles by analyzing the area, amplitude, and other information of the intrinsic fluorescence pulse signal generated by aerosol particles under continuous irradiation when passing through the photosensitive area, and combining it with the elastically scattered light pulse signal of the particles, providing a basis for the preliminary classification of aerosol particles.

Claims

1. A bioaerosol monitoring device, comprising an optical path, an air path intersecting the optical path, and a signal processing system connected to the optical path; the optical path comprises a laser irradiation optical path for irradiating particles to be measured, a scattered light collection optical path for receiving scattered light signals, and a fluorescence collection optical path for receiving fluorescence signals; the air path is used to sample particles to be measured; the signal processing system is used to analyze and process signals; the intersection of the laser irradiation optical path and the air path is a light sensitive area (G); characterized in that, The focus (M) of the excitation light source for irradiating the measured particles is located before or after the photosensitive area (G) on the optical axis of the laser irradiation light path, so that the cross-section of the excitation light spot perpendicular to the optical axis of the laser irradiation light path in the photosensitive area (G) is rectangular. When a single aerosol particle passes through the photosensitive area, it is continuously irradiated by the excitation light to obtain the intrinsic fluorescence bleaching rate.

2. The bioaerosol monitoring device according to claim 1, characterized in that: The laser irradiation optical path for irradiating the measured particles comprises an excitation light source (101). The light emitted by the excitation light source (101) is collimated in parallel with the X-axis direction by an aspherical mirror (102) to form a parallel light beam, and then focused by a cylindrical mirror (103) to pass through a light sensitive area (G) to reach a light trap (105). In the Y-axis direction of the light sensitive area (G), there are a curved reflector (104) and a dichroic mirror (106) in sequence. The dichroic mirror (106) is arranged at 45° with the Y-axis. The dichroic mirror (106) has high reflectivity for elastic scattered light and high transmittance for a fluorescent wavelength band.

3. The bioaerosol monitoring device according to claim 1, characterized in that: The scattered light collecting optical path for receiving scattered light signals comprises a focusing mirror (111), a scattering aperture (112) and a scattered light receiver (113) which are sequentially arranged along the transmission direction of the elastic scattered light.

4. The bioaerosol monitoring device according to claim 1, characterized in that: The fluorescence collection optical path for receiving the fluorescence signal comprises a fluorescence filter (107), a fluorescence focusing lens (108), a fluorescence diaphragm (109) and a fluorescence receiver (110) which are sequentially arranged along the fluorescence transmission direction.

5. The bioaerosol monitoring device according to claim 1, characterized in that: The air path is composed of an air inlet nozzle (201), an air outlet nozzle (202) and an air pump. The air inlet direction of the air path is parallel to the Z axis and passes through the light sensitive area (G).

6. The bioaerosol monitoring device according to claim 1, characterized in that: The signal processing system comprises a scattered light amplifying circuit (301), a scattered light AD conversion circuit (302), a fluorescence amplifying circuit (303), a fluorescence AD ​​conversion circuit (305) and an FPGA circuit (303); the elastic scattered light pulse signal collected by the scattered light receiver (113) is sequentially amplified by the scattered light amplifying circuit (301), converted into a digital signal by the scattered light AD conversion circuit (302) and reaches the FPGA circuit (303); the intrinsic fluorescence pulse signal collected by the fluorescence receiver (110) is sequentially amplified by the fluorescence amplifying circuit (303), converted into a digital signal by the fluorescence AD ​​conversion circuit (305) and reaches the FPGA circuit (303); the FPGA circuit is used to calculate the relative fluorescence intensity of the measured aerosol particles, the ratio of the scattering peak value and the intrinsic fluorescence bleaching speed.

7. A bioaerosol monitoring method is implemented using the bioaerosol monitoring device according to any one of claims 1 to 6, comprising the following steps: S1. Construct a three-dimensional coordinate system for the peak value, relative fluorescence intensity and intrinsic fluorescence bleaching rate of elastic scattered light pulse signals of different bioaerosol particles: S1.1 When the bioaerosol particles pass through the light-sensitive area, elastic scattered light pulse signals and intrinsic fluorescence pulse signals are stimulated, which are received by the scattered light receiver (113) and the fluorescence receiver (110) respectively, and are transmitted to the FPGA circuit after being processed by the signal amplification circuit and the AD conversion circuit; S1.2 calculates the peak value h0 of the elastic scattered light pulse signal of the bioaerosol particles to be tested, the peak value h1 of the intrinsic fluorescence pulse signal, and the area s1 of the intrinsic fluorescence pulse signal through the FPGA circuit; S1.

3. Calculate the relative fluorescence intensity, i.e., the ratio of the peak value h1 of the intrinsic fluorescence pulse signal to the peak value h0 of the elastic scattered light pulse signal, through the FPGA circuit; S1.

4. Calculate the intrinsic fluorescence bleaching rate, that is, the ratio of the area s1 of the intrinsic fluorescence pulse signal to the peak value h1 of the intrinsic fluorescence pulse signal, through the FPGA circuit; S1.5 Repeat steps S1.1-S1.4 using different bioaerosol particles to construct a three-dimensional coordinate system of the peak value, relative fluorescence intensity and intrinsic fluorescence bleaching rate of the elastic scattered light pulse signal of different bioaerosol particles; S2. When the bioaerosol particles to be tested pass through the light-sensitive area, elastic scattered light pulse signals and intrinsic fluorescence pulse signals are stimulated, which are received by the scattered light receiver (113) and the fluorescence receiver (110) respectively and transmitted to the FPGA circuit; S3. The peak value, relative fluorescence intensity and intrinsic fluorescence bleaching rate of the elastic scattered light pulse signal of the biological aerosol particles to be tested are calculated by the FPGA circuit, and the type of the aerosol particles to be tested is determined by comparing the landing area in the three-dimensional coordinate system.

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