PM0.1 concentration detection sensor and method based on multi-angle laser scattering and air purification device

Abstract

The invention relates to a PM0.1 concentration detection sensor and method based on multi-angle laser scattering and an air purification device. The sensor comprises a laser emission module, an extinction air chamber, a dual-angle detection array, a reference light compensation module, a signal preprocessing module, a signal processing and calculating module and an output module. The laser emission module is used for forming parallel laser beams; the inner wall of the extinction air chamber is coated with an aluminum oxide matte coating; the double-angle detection array comprises a 90-degree + / -5-degree lateral detector and a 5-15-degree forward detector, the 90-degree + / -5-degree lateral detector is located on the front side face of the extinction air chamber, and the 5-15-degree forward detector is located in the forward direction of the extinction air chamber; the reference light compensation module adopts an independent detector; the signal preprocessing module performs phase-locked amplification and dark current compensation processing on the signal; the signal processing and calculating module is used for calculating the final concentration of PM0.1; and the output module is used for outputting a final PM0.1 concentration detection result. According to the invention, ultrafine particles can be detected in real time.

Description

Technical Field

[0001] The present invention belongs to the technical field of PM0.1 concentration detection, and particularly relates to a PM0.1 concentration detection sensor, method and air purification device based on multi-angle laser scattering. Background Art

[0002] Traditional particulate matter detection technologies include light scattering method and laboratory method, among which:

[0003] Light scattering method: Using a conventional laser sensor (such as PM2.5 detection), relying on single 90° scattering, the detection lower limit > 0.5μm (such as patent CN208902426U), which cannot meet the PM0.1 requirement.

[0004] Laboratory method: The β-ray method (such as patent CN110595648B) and the electrophoretic mobility classification method have high precision (detection lower limit 0.01μm), but the equipment of this method is large in volume (> 0.5m 3 ), and the cost > 500,000 yuan, which cannot be used for civilian purposes.

[0005] In summary, the existing detection technologies have the following technical defects:

[0006] Insufficient sensitivity: The scattered light of small particles (< 0.1μm) is weak, and single-angle detection is easy to lose signals.

[0007] Poor environmental adaptability: Optical path pollution and changes in temperature and humidity lead to detection drift (drift of the existing technology > 15%, CN112393245A).

[0008] High cost: There is a lack of high-cost performance solutions for civilian equipment. Summary of the Invention

[0009] The purpose of the present invention is to provide a PM0.1 concentration detection sensor with low cost, high sensitivity and strong environmental adaptability to solve the problem that the existing technology cannot detect ultrafine particulate matter in real time.

[0010] The present invention provides a PM0.1 concentration detection sensor based on multi-angle laser scattering, including a laser emission module, an extinction gas chamber, a dual-angle detection array, a reference light compensation module, a signal preprocessing module, a signal processing and calculation module, and an output module;

[0011] The laser emission module includes a 405nm laser and a collimating lens, and is used to emit 405nm violet light through the 405nm laser and form a parallel laser beam through the collimating lens;

[0012] The extinction cell is arranged at the optical path outlet of the laser emission module. The parallel laser beam is perpendicularly incident on the center of the extinction cell and is orthogonal to the air flow direction. The inner wall of the extinction cell is coated with an alumina matte coating. The extinction cell is provided with a constant-speed fan and a flow-limiting orifice plate for stabilizing the air flow.

[0013] The dual-angle detection array includes a 90°±5° lateral detector and a 5-15° forward detector. The 90°±5° lateral detector is located on the positive side of the extinction cell, and the 5-15° forward detector is located in the forward direction of the extinction cell. The dual-angle detection array forms an orthogonal optical path with the laser beam emitted from the extinction cell.

[0014] The reference light compensation module uses an independent detector to monitor the laser intensity in real time for compensating the light source fluctuation. The compensation formula is:

[0015]

[0016] In the formula, C is the compensated PM0.1 concentration; K is the calibration coefficient, which is the proportional coefficient determined through the standard PM0.1 aerosol experiment and is dimensionless; I 90° is the 90° lateral scattered light intensity, that is, the scattered light intensity received by the detector in the 90°±5° direction, with the unit of μW / cm 2 ; I 5° is the forward 5-15° scattered light intensity, that is, the scattered light intensity received by the detector in the 5-15° direction, with the unit of μW / cm 2 ; α is the dynamic weight factor, that is, the weighting coefficient of the forward scattering signal, with the value range of 0.3 to 0.5; Q is the volume of air passing through the extinction cell per unit time, with the unit of L / min; t is the sampling time, that is, the integration time for single-concentration calculation, with the unit of minute; Iref is the reference light intensity, that is, the laser intensity directly detected by the independent detector, with the unit of μW / cm 2 ;

[0017] The signal preprocessing module is used to receive the scattered light signals output by the dual-angle detection array and perform phase-locked amplification and dark current compensation processing in sequence.

[0018] The signal processing and calculation module is used to correct the light intensity through reference light normalization and temperature compensation based on the preprocessed signals, and calculate the final PM0.1 concentration based on the corrected light intensity.

[0019] The output module is used to output the final PM0.1 concentration detection result.

[0020] Furthermore, the roughness Ra of the alumina matte coating is ≤0.5 μm, and the stray light suppression rate is >99.5%.

[0021] Further, the volume of the extinction cell ≤ 5 cm 3 .

[0022] Further, the 90° ± 5° lateral detector uses an APD detector to collect Mie scattering signals with a responsivity of 0.7 A / W @ 405 nm.

[0023] Further, the 5 - 15° forward detector uses a photodiode to collect Rayleigh scattering signals with a responsivity > 0.5 A / W @ 405 nm.

[0024] The present invention also provides a PM0.1 concentration detection method using the sensor, including the following steps:

[0025] Step 1, system initialization:

[0026] 1) Optical path calibration:

[0027] The laser module emits 405 nm violet light, and the collimating lens forms a parallel light beam with a divergence angle < 0.5°;

[0028] The reference light compensation module monitors the laser intensity in real time and establishes a reference value Iref_base;

[0029] 2) Chamber pretreatment:

[0030] The constant - speed fan is started to purge the extinction cell at a flow rate of 0.5 L / min ± 5% to remove residual particles;

[0031] 3) Parameter loading:

[0032] Read the calibration coefficient K, the dynamic weight factor look - up table library, and the temperature compensation coefficient from the EEPROM;

[0033] Step 2, scattered light signal acquisition:

[0034] 1) Optical path configuration:

[0035] The laser beam is perpendicularly incident on the center of the extinction cell, orthogonal to the gas flow direction, with a flow velocity of 2 m / s ± 10%;

[0036] 2) Signal acquisition:

[0037] 90° lateral scattered light intensity I 90 °: The APD detector is used to collect Mie scattering signals with a responsivity of 0.7 A / W @ 405 nm;

[0038] 5° forward scattered light intensity I5°: The photodiode is used to collect Rayleigh scattering signals with a responsivity of 0.5 A / W @ 405 nm;

[0039] Reference light intensity I_ref: The independent detector is used to monitor the laser intensity in real time to compensate for the light source fluctuation;

[0040] 3) Sampling strategy:

[0041] Synchronously collect I 90 °, I5°, I_ref every 0.5 seconds, and collect 100 groups of data and take the average to reduce random noise;

[0042] Step 3, signal preprocessing:

[0043] 1) Lock-in amplification:

[0044] The signal passes through a 50 kHz band-pass filter to suppress ambient light and circuit noise, and the noise suppression ratio > 40 dB;

[0045] 2) Dark current compensation:

[0046] Deduct the dark current of the detector, and the dark current of the APD detector < 10 nA @ 25 °C);

[0047] Step 4, signal processing and algorithm fusion;

[0048] 1) Calculation of dynamic weight factor α:

[0049] According to the current light intensity ratio Query the particle size distribution library to determine the α value. When the light intensity ratio > 2, α = 0.3; when the light intensity ratio < 1, α = 0.5;

[0050]

[0051] 2) Normalization of reference light:

[0052] Calculate the real-time normalization factor Compensate for laser power drift;

[0053] Corrected light intensity:

[0054] I 90_nor m = I 90_corrected · norm_factor, I 5_norm = I 5_corrected · norm_factor;

[0055] 3) Temperature compensation:

[0056] Read the value of the temperature sensor and apply a second-order polynomial to correct the light intensity:

[0057] I 90_temp = I 90_norm · (1 + a · T + b · T 2 ), I 5_temp = I 5_norm · (1 + a · T + b · T 2);Coefficient a = -0.002 / °C, coefficient b = 0.0001 / °C 2 ;

[0058] Step 5, Concentration calculation and output:

[0059] 1) Application of concentration formula:

[0060] Parameter values: Q = 0.5 L / min, t = 0.5 min;

[0061] 2) Range switching:

[0062] If C > 1000 μg / m 3 , automatically switch to the low-gain mode to expand the dynamic range;

[0063] 3) Result output:

[0064] Send the concentration value to the display module or the main control MCU of the air purifier.

[0065] The present invention also provides an air purification device, including the PM0.1 concentration detection sensor described above. The output module outputs the concentration value through the UART protocol, with a resolution of 0.1 μg / m 3 , and the sensor is powered by 5V with a power consumption ≤ 0.5W.

[0066] Furthermore, the air purification device automatically adjusts the filter wind speed according to the PM0.1 concentration.

[0067] By means of the above solution, the PM0.1 concentration detection sensor, method and air purification device based on multi-angle laser scattering have the following technical effects:

[0068] 1) Ultra-sensitive detection ability.

[0069] Detection lower limit: 0.05 μm (PM0.1), which is 10 times higher than that of traditional laser sensors (0.5 μm), and for the first time realizes the accurate monitoring of ultrafine particles by civilian equipment.

[0070] Particle size resolution: Based on the Mie scattering theory, distinguish particles with a size of 0.05 - 0.1 μm (accuracy ±8%), while traditional technologies can only identify particles > 0.5 μm.

[0071] Data support: Laboratory calibration shows that the detection signal-to-noise ratio for 0.05 μm polystyrene latex spheres (PSL) > 15 dB (traditional solution < 5 dB).

[0072] 2) Anti-interference and stability (strong environmental adaptability).

[0073] Stray light suppression: The extinction chamber design (inner wall with Al2O3 matte coating) makes the proportion of stray light < 0.5% (traditional solution > 10%).

[0074] Temperature and humidity compensation: Built-in temperature model (-10°C to 50°C) + reference light normalization, detection drift < 3% (industry standard < 15%).

[0075] Vibration resistance: IP54 protection + structural optimization, signal fluctuation caused by vibration (10 - 500 Hz) < 1.5% (key index for vehicle-mounted scenarios). 3) Algorithm innovation (dynamic adaptability)

[0076] Dual-angle fusion algorithm: 90° (Mie scattering) + 5 - 15° (Rayleigh scattering) signals are dynamically weighted (α = 0.3 - 0.5), adapting to complex particle size distributions (such as cigarette smoke (0.01 - 0.5μm) and industrial dust (0.1 - 2μm)).

[0077] Real-time response: 1Hz data update (traditional devices are 5 - 10Hz but with low accuracy), meeting the closed-loop requirements of "real-time detection - real-time purification" for air purifiers.

[0078] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly and implement it in accordance with the content of the specification, the following describes in detail with reference to the preferred embodiments of the present invention and the accompanying drawings. Brief description of the drawings

[0079] Figure 1 It is a schematic structural diagram of the PM0.1 concentration detection sensor based on multi-angle laser scattering of the present invention;

[0080] Figure 2 It is a PM0.1 concentration detection flow chart of the present invention. Detailed description of the specific embodiments

[0081] The following combines the drawings and embodiments to further describe in detail the specific embodiments of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0082] Term explanation:

[0083] Mie scattering: When the particle size is close to the laser wavelength (0.1μm ≈ 405nm / 4), anisotropic scattering occurs, and the signal is the strongest in the 90° direction.

[0084] Phase-locked amplification: By locking the phase of the reference signal, the same-frequency signal is extracted to suppress broadband noise (such as ambient light, circuit noise).

[0085] Dynamic weight factor α: Adjust the weights of the dual-angle signals according to the particle size distribution (α → 0.5 for small particles, α → 0.3 for large particles), and model based on Mie scattering theory.

[0086] As shown Figure 1 In this embodiment, a PM0.1 concentration detection sensor based on multi-angle laser scattering is provided, which includes a laser emission module, an extinction gas chamber, a dual-angle detection array, a reference light compensation module (beam splitter, independent detector), a signal preprocessing module, a signal processing and calculation module, and an output module.

[0087] The laser emission module includes a 405 nm laser and a collimating lens, which are used to emit 405 nm violet light through the 405 nm laser and form a parallel laser beam through the collimating lens; the laser emission module uses short-wavelength laser: 405 nm violet light (wavelength 405 ± 10 nm, power 5 mW) to enhance the scattering cross-section of small particles (3 orders of magnitude higher than that of 850 nm laser).

[0088] The extinction gas chamber is arranged at the optical path outlet of the laser emission module, and the parallel laser beam is perpendicularly incident on the center of the extinction gas chamber and is orthogonal to the air flow direction; the inner wall of the extinction gas chamber is coated with an alumina matte coating; the extinction gas chamber is provided with a constant-speed fan (0.5 L / min ± 5%) and a flow-limiting orifice plate for stabilizing the air flow.

[0089] The dual-angle detection array includes a 90° ± 5° lateral detector and a 5 - 15° forward detector. The 90° ± 5° lateral detector is located on the positive side of the extinction gas chamber, and the 5 - 15° forward detector is located in front of the extinction gas chamber. The dual-angle detection array forms an orthogonal optical path with the laser beam emitted from the extinction gas chamber.

[0090] The reference light compensation module uses an independent detector to monitor the laser intensity in real time for compensating the light source fluctuation, and the compensation formula is:

[0091]

[0092] The meanings of each parameter are as follows:

[0093] C - PM0.1 concentration

[0094] Definition: The mass concentration of PM0.1 (≤ 0.1 μm) ultrafine particles in the air, with the unit of μg / m 3 .

[0095] Detection range: 0.1 - 1000 μg / m 3 (Automatic range switching).

[0096] Accuracy: ±10% (@10 - 500 μg / m 3, compared with the beta-ray method).

[0097] Example: When the calculation result is 50 μg / m 3 It means that there are 50 micrograms of PM0.1 particles per cubic meter of air.

[0098] K - calibration coefficient

[0099] Definition: The proportionality coefficient determined through the standard PM0.1 aerosol experiment, dimensionless.

[0100] Function: Convert the light intensity signal into the actual concentration, considering factors such as the optical path efficiency and particle scattering cross-section.

[0101] Calibration method:

[0102] Use polystyrene latex spheres (PSL, 0.05 - 0.5 μm) to establish a standard curve, formula:

[0103]

[0104] The range of K values measured in the laboratory: 0.8 - 1.2 (under different particle size distributions).

[0105] I 90 ° - 90° lateral scattered light intensity

[0106] Definition: The scattered light intensity received by the detector in the direction of 90° ± 5°, with the unit of μW / cm 2 .

[0107] Physical meaning: Reflect the Mie scattering signal (sensitive to 0.1 μm particles).

[0108] Experimental data:

[0109] For 0.1 μm particles, the 90° scattered light intensity is about 2 times that of the forward 5° (Mie scattering theory).

[0110] Detector sensitivity: The responsivity of APD (Hamamatsu S1223) is 0.7 A / W @ 405 nm.

[0111] α - dynamic weight factor

[0112] Definition: The weighting coefficient of the forward scattering signal, with the value range of 0.3 - 0.5.

[0113] Function: Adaptively adjust the weights of the double-angle signals according to the particle size distribution, and enhance the detection ability of small particles.

[0114] Adjustment strategy:

[0115] Lookup table method: Based on the particle size distribution library (e.g., for 0.05μm particles, α = 0.5; for 0.5μm particles, α = 0.3). The α value is adaptively adjusted by looking up the table according to the particle size distribution.

[0116] Algorithm implementation: The MCU dynamically updates the α value according to historical data and the current light intensity ratio.

[0117] I5° - Forward 5 - 15° scattered light intensity

[0118] Definition: The scattered light intensity received by the detector in the 5 - 15° direction, with the unit of μW / cm 2 。

[0119] Physical meaning: Enhance the Rayleigh scattering signal (sensitive to particles < 0.1μm).

[0120] Experimental verification: The forward scattered light intensity of 0.05μm particles is 3 times that at 90° (Rayleigh scattering theory).

[0121] Detector model: Photoelectric diode (S1133 - 01), responsivity 0.5A / W @ 405nm.

[0122] Q - Sampling flow rate

[0123] Definition: The volume of air passing through the gas chamber per unit time, with the unit of L / min.

[0124] Parameter value: 0.5L / min ± 5% (controlled by a constant - speed fan + restricted - orifice plate).

[0125] Function: The larger the flow rate, the more particles are detected per unit time, and the signal - to - noise ratio is improved. In the formula, Q·t represents the total sampling volume (L), which converts the light intensity signal into concentration (μg / m 3 )。

[0126] t - Sampling time

[0127] Definition: The integration time for single - concentration calculation, with the unit of minute.

[0128] Value range: 0.1 - 1 minute (default 0.5 minute, corresponding to a response time < 5 seconds).

[0129] Trade - off: Long integration time (1 minute): Stable signal, suitable for low - concentration scenarios. Short integration time (0.1 minute): Fast response, suitable for sudden pollution scenarios.

[0130] I ref - Reference light intensity

[0131] Definition: The laser intensity directly detected by an independent reference optical path, with the unit of μW / cm 2 。

[0132] Function: Compensate for laser power fluctuations (such as temperature drift, aging attenuation).

[0133] Experimental data:

[0134] Temperature drift: The rate of change of laser power with temperature is approximately -0.2% / °C (based on 25°C).

[0135] Compensation effect: After the reference light is normalized, the influence of temperature drift is reduced from ±5% to ±1.2%.

[0136] Table 1 Parameter summary

[0137]

[0138]

[0139] The signal preprocessing module is used to receive the scattered light signals output by the dual-angle detection array and perform phase-locked amplification and dark current compensation processing in sequence.

[0140] The signal processing and calculation module is used to correct the light intensity based on the preprocessed signals through reference light normalization and temperature compensation (temperature compensation model, based on second-order polynomial fitting to correct the influence of ambient temperature), and calculate the final PM0.1 concentration based on the corrected light intensity.

[0141] The output module is used to output the detection result of the final PM0.1 concentration.

[0142] Compared with the prior art, this sensor has the following advantages:

[0143] 1. For the first time, forward scattering at 5-15° and 90° side scattering are combined for PM0.1 detection (the prior art only uses a single angle).

[0144] 2. Dynamic weight factor α + reference light compensation, breaking through the detection sensitivity of small particles (detection lower limit 0.05μm). Traditional algorithms cannot fuse multi-angle signals.

[0145] 3. Miniaturized design (volume < 100 cm 3 ) + low cost (< 200 yuan), suitable for civilian air purifiers. The purification efficiency is increased by 30%.

[0146] The comparison table with the prior art is shown in Table 2.

[0147] Table 2 Comparison table

[0148]

[0149] In this embodiment, the roughness Ra of the alumina matte coating ≤ 0.5μm, and the stray light suppression rate > 99.5%.

[0150] In this embodiment, the volume of the extinction cell ≤ 5 cm 3 . The optical path is orthogonally arranged, and the cell size is (3 cm × 2 cm × 1 cm).

[0151] In this embodiment, dual-angle scattering detection is adopted with 90° lateral (main Mie scattering signal) + 5 - 15° forward (enhanced small particle signal). The 90° ± 5° lateral detector adopts an APD detector (APD, Hamamatsu S1223, avalanche photodiode) for collecting Mie scattering signals, with a responsivity of 0.7 A / W @ 405 nm.

[0152] In this embodiment, the 5 - 15° forward detector adopts a photodiode for collecting Rayleigh scattering signals, with a responsivity > 0.5 A / W @ 405 nm.

[0153] As shown in Figure 2 , this embodiment also provides a PM0.1 concentration detection method using the sensor, including the following steps:

[0154] Step 1, system initialization:

[0155] 1) Optical path calibration:

[0156] The laser module emits 405 nm violet light (5 mW), and the collimating lens forms a parallel beam with a divergence angle < 0.5°;

[0157] The reference light compensation module (reference light detector) monitors the laser intensity in real time to establish a reference value Iref_base;

[0158] 2) Cell pretreatment:

[0159] The constant-speed fan is started to purge the extinction cell (inner wall with Al2O3 matte coating) at a flow rate of 0.5 L / min ± 5% to remove residual particles;

[0160] 3) Parameter loading:

[0161] Read the calibration coefficient K, the dynamic weight factor look-up table library (particle size - α mapping table), and the temperature compensation coefficient from the EEPROM;

[0162] Step 2, scattered light signal acquisition:

[0163] 1) Optical path configuration:

[0164] The laser beam is vertically incident on the center of the extinction cell, orthogonal to the air flow direction, with a flow velocity of 2 m / s ± 10%;

[0165] 2) Signal acquisition:

[0166] The 90° lateral scattered light intensity I 90°: The Mie scattering signal is collected by an APD detector (Hamamatsu S1223), with a responsivity of 0.7 A / W @ 405 nm;

[0167] The forward scattered light intensity I5° at 5°: The Rayleigh scattering signal is collected by a photodiode (S1133-01), with a responsivity of 0.5 A / W @ 405 nm;

[0168] The reference light intensity I_ref: The laser intensity is monitored in real time by an independent detector to compensate for the light source fluctuation;

[0169] 3) Sampling strategy:

[0170] Collect I 90 °, I5°, and I_ref (16-bit ADC, 200 kS / s) synchronously every 0.5 seconds. A total of 100 groups of data are collected and averaged to reduce random noise;

[0171] Step 3, Signal preprocessing:

[0172] 1) Lock-in amplification:

[0173] The signal passes through a 50 kHz band-pass filter (synchronized with the laser modulation frequency) to suppress ambient light (such as sunlight) and circuit noise, with a noise suppression ratio > 40 dB;

[0174] 2) Dark current compensation:

[0175] Deduct the detector dark current. The dark current of the APD detector < 10 nA @ 25 °C), formula:

[0176] I 90_corrected = I 90° - I dark_90 , I 5_corrected = I 5° - I dark_5；

[0177] Step 4, Signal processing and algorithm fusion;

[0178] 1) Calculation of the dynamic weight factor α:

[0179] According to the current light intensity ratio Query the particle size distribution library to determine the α value. When the light intensity ratio > 2, α = 0.3; when the light intensity ratio < 1, α = 0.5;

[0180]

[0181] 2) Reference light normalization:

[0182] Calculate the real-time normalization factor Compensate for the laser power drift; the corrected light intensity: I 90_norm = I90_corrected · norm_factr, I 5_norm = I 5_corrected · norm_factor;

[0183] 3) Temperature compensation:

[0184] Read the temperature sensor value (±0.5°C accuracy), and apply a second-order polynomial to correct the light intensity: I 90_temp = I 90_norm · (1 + a·T + b·T 2 ), I 5_temp = I 5_norm · (1 + a·T + b·T 2 ); Coefficient a = -0.002 / °C, coefficient b = 0.0001 / °C 2 ;

[0185] Step 5, Concentration calculation and output:

[0186] 1) Application of the concentration formula:

[0187] Parameter values: Q = 0.5 L / min, t = 0.5 min (total sampling volume 0.25 L);

[0188] 2) Range switching:

[0189] If C > 1000 μg / m 3 , automatically switch to the low-gain mode (detector attenuator enabled) to expand the dynamic range;

[0190] 3) Result output:

[0191] Send the concentration value (0.1 μg / m 3 resolution) to the display module or the main control MCU of the air purifier via the UART protocol.

[0192] Step 6. System control and feedback (integrated application)

[0193] 1) Link with the air purifier:

[0194] When C > 50 μg / m 3 , trigger the high-speed filter mode (5 m / s), and if C < 15 μg / m 3 after 30 minutes, switch back to the low speed.

[0195] 2) Abnormal alarm:

[0196] If C > 500 μg / m is detected continuously 3 times 3 , start the UV-C disinfection module (integrated purifier scenario).

[0197] This embodiment also provides an air purification device, including the PM0.1 concentration detection sensor described above, and the linkage process is as in step 6 above.

[0198] In this embodiment, the air purification device automatically adjusts the filter screen wind speed according to the PM0.1 concentration.

[0199] The technical effects of the relevant steps in this detection method are as follows:

[0200] 1. Multi-angle scattering signal fusion

[0201] Steps 2 and 4: Simultaneously collect 90° and 5° scattered light, and adaptively adjust the weight through the dynamic α value to solve the problem of weak signals of small particles.

[0202] Technical support: Mie scattering theory (strong 90° signal for 0.1μm particles) + Rayleigh scattering theory (strong forward signal for particles < 0.1μm).

[0203] 2. Real-time compensation of reference light

[0204] Steps 2 and 4: Eliminate laser power fluctuations (such as temperature drift) through I_ref normalization, and the temperature drift after compensation < 1.2%.

[0205] Hardware implementation: The independent detector is isolated from the main optical path to avoid interference from scattered light.

[0206] 3. Dynamic weight factor α

[0207] Step 4: Use the look-up table method to dynamically adjust α according to the light intensity ratio to adapt to complex particle size distributions (such as cigarette smoke and industrial dust).

[0208] Experimental data: The error < 5% when α = 0.5 for 0.05μm particles, and the error < 8% when α = 0.3 for 0.5μm particles.

[0209] 4. Phase-locked amplification technology

[0210] Step 3: Extract the 50kHz modulation signal to suppress ambient light and circuit noise, and the signal-to-noise ratio is increased by 30dB.

[0211] Hardware design: The analog phase-locked loop (AD630) and digital signal processing (MCU) work together.

[0212] The application scenarios of the present invention will be described in detail below through specific examples.

[0213] Application scenario example (vehicle-mounted air purifier)

[0214] 1. Detection stage:

[0215] After the vehicle starts, the sensor samples at a flow rate of 0.5L / min and displays the PM0.1 concentration in real time.

[0216] 2. Purification stage:

[0217] When C > 30 μg / m 3 , the air conditioner switches to the internal circulation and increases the airspeed to 3 m / s.

[0218] 3. Result feedback:

[0219] The mobile phone APP pushes real-time data and displays the remaining life of the filter (calculated based on the cumulative purification volume).

[0220] Table 3 Verification data of the detection method

[0221]

[0222] Example

[0223] Example 1 Independent detection sensor

[0224] 1) Technical parameters

[0225] Table 4 Technical parameter table

[0226]

[0227] 2) Structural design

[0228] Optical path layout: The laser passes through a collimating lens (focal length 10 mm, diameter 5 mm) to form a parallel light beam (divergence angle < 0.5°) and is vertically incident on the center of the gas chamber.

[0229] 90° detector: Located on the positive side of the gas chamber, 15 mm away from the beam center, and the receiving solid angle Ω = 0.1 sr.

[0230] 5° detector: Located in the forward direction of the gas chamber, with an angle of 5° ± 1° with the laser beam, and the scattered light is focused through a parabolic mirror (focal length 20 mm).

[0231] Airflow control: A micro fan (model: Nidec MU0501V1) drives the airflow, and the flow rate is stabilized to 0.5 L / min ± 5% through a flow-limiting orifice plate (diameter 0.5 mm).

[0232] 3) Performance indicators

[0233] Table 5 Performance indicators

[0234]

[0235] 4) Application scenarios

[0236] Vehicle-mounted air purifier:

[0237] Installation location: Near the air conditioner outlet (airflow speed 1.5 m / s).

[0238] Function: Real-time display of PM0.1 concentration. When the standard is exceeded, it will link to the internal circulation of the air conditioner and prompt to replace the filter screen.

[0239] Actual measurement case: In the scenario of smoking in a certain SUV, the PM0.1 peak value reaches 300 μg / m 3 , and it drops to 50 μg / m after 10 minutes when the sensor triggers the internal circulation. 3 .

[0240] Household disinfection machine:

[0241] Integration method: Embedded in the air outlet of the disinfection machine, and communicates with the main control MCU through the UART protocol.

[0242] Function: During UV-C disinfection, it can monitor the residual nanoscale aerosol (such as coronavirus) in real time, and automatically turn off the UV lamp after disinfection is completed.

[0243] Air purification device integrating PM0.1 detection in Example 2

[0244] 1) Linkage control logic

[0245] Air velocity adjustment strategy:

[0246] Table 6 Air velocity adjustment strategy

[0247] <![CDATA[PM0.1 concentration (μg / m 3 )]]> Filter screen air velocity (m / s) Response time ＜15 Low speed (1.5 m / s) Real-time 15～50 Medium speed (3 m / s) < 30 seconds ＞50 High speed (5 m / s) < 10 seconds

[0248] Algorithm optimization:

[0249] Adopt a dynamic weight factor α (0.3 - 0.5), which is adjusted according to the particle size distribution by looking up the table. For example:

[0250] Cigarette smoke (0.01 - 0.5 μm): α = 0.5 (enhance the forward signal).

[0251] Pollen (> 0.1 μm): α = 0.3 (focus on the lateral signal).

[0252] 2) Purification efficiency test

[0253] Test conditions:

[0254] Cabin: 30m 3 Stainless steel cabin, temperature 25 °C, RH 50%.

[0255] Pollutant: NaCl aerosol (median particle size 0.07 μm, concentration 500 μg / m 3 ).

[0256] Result comparison:

[0257] Table 7 Result comparison

[0258]

[0259] Note: The purification efficiency test is based on the "Indoor Air Quality Standard" GB / T 18883-2022.

[0260] 3) Structural design

[0261] Sensor integration:

[0262] Location: Middle of the air duct (airflow speed 2 m / s), optimizing the flow field uniformity through a deflector plate.

[0263] Protection: IP54 waterproof grade, with a pre-filter layer in front of the filter (filtering particles > 1 μm), extending the sensor life.

[0264] Filter configuration:

[0265] Material: Electret meltblown cloth + activated carbon composite filter.

[0266] Filtration efficiency: > 99.97% @ 0.1 μm (DOP test), dust holding capacity > 2000 g.

[0267] 4) User interface and function expansion

[0268] Display and control:

[0269] The OLED screen displays the PM0.1 concentration in real time (resolution 0.1 μg / m 3 ), filter life (calculated based on the cumulative purification amount).

[0270] APP linkage: Connect to the mobile phone via Bluetooth / WiFi, and push air quality reports (daily / weekly reports), filter replacement reminders.

[0271] Value-added functions:

[0272] Allergen mode: When PM0.1 > 30 μg / m is detected 3 , automatically turn on the HEPA + UV-C collaborative purification.

[0273] Intelligent scenario: Link with the smart home system, and automatically increase the wind speed when someone enters the room.

[0274] Laboratory data

[0275] 1) Calibration experiment:

[0276] Standard substance: Polystyrene latex spheres (PSL, 0.05 - 0.5 μm, traceable to NIST).

[0277] Linearity: R 2 = 0.978 (10 - 500 μg / m 3 ), fitting formula:

[0278] C measured = 1.02C β-ray -1.5。

[0279] 2) Environmental adaptability test:

[0280] Table 8 Test data

[0281]

[0282] 3) Anti-interference test:

[0283] Vibration test: Sweep frequency from 10 - 500 Hz (amplitude 0.5 mm), signal fluctuation < 1.5%.

[0284] Dust durability: Continuous operation for 1000 hours (simulating PM2.5 = 200 μg / m 3 ), drift < 5%.

[0285] 4) Filter life test: Treat air with PM0.1 = 100 μg / m 3 and the efficiency is still > 95% after cumulative purification of 5000 m 3 .

[0286] The present invention has the following technical effects:

[0287] 1) Ultra-sensitive detection ability.

[0288] Detection limit: 0.05 μm (PM0.1), which is 10 times higher than that of traditional laser sensors (0.5 μm), and for the first time realizes precise monitoring of ultrafine particles by civilian equipment.

[0289] Particle size resolution: Based on Mie scattering theory, it can distinguish particles with a size of 0.05 - 0.1 μm (accuracy ±8%), while traditional technologies can only identify particles larger than 0.5 μm.

[0290] Data support: Laboratory calibration shows that the detection signal-to-noise ratio for 0.05 μm polystyrene latex spheres (PSL) > 15 dB (traditional scheme < 5 dB).

[0291] 2) Anti-interference and stability (strong environmental adaptability).

[0292] Stray light suppression: The design of the extinction chamber (inner wall with Al2O3 matte coating) makes the proportion of stray light < 0.5% (traditional scheme > 10%).

[0293] Temperature and humidity compensation: Built-in temperature model (-10°C to 50°C) + reference light normalization, detection drift < 3% (industry standard < 15%).

[0294] Vibration resistance: IP54 protection + structural optimization, signal fluctuation caused by vibration (10 - 500 Hz) < 1.5% (key indicator for in-vehicle scenarios). 3) Algorithm innovation (dynamic adaptability)

[0295] Dual-angle fusion algorithm: Dynamically weighted signals of 90° (Mie scattering) + 5 - 15° (Rayleigh scattering) (α = 0.3 - 0.5), adaptable to complex particle size distributions (such as cigarette smoke (0.01 - 0.5 μm) and industrial dust (0.1 - 2 μm)).

[0296] Real-time response: 1 Hz data update (traditional devices are 5 - 10 Hz but with low accuracy), meeting the closed-loop requirement of "real-time detection - real-time purification" for air purifiers.

[0297] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A PM0.1 concentration detection sensor based on multi-angle laser scattering, characterized in that, It includes a laser emission module, an extinction gas chamber, a dual-angle detection array, a reference light compensation module, a signal preprocessing module, a signal processing and calculation module, and an output module; The laser emission module includes a 405nm laser and a collimating lens, which are used to emit 405nm violet light through the 405nm laser and form a parallel laser beam through the collimating lens; The extinction gas chamber is arranged at the optical path outlet of the laser emission module. The parallel laser beam is perpendicularly incident on the center of the extinction gas chamber and is orthogonal to the air flow direction. The inner wall of the extinction gas chamber is coated with an alumina matte coating. The extinction gas chamber is provided with a constant-speed fan and a flow-limiting orifice plate for stabilizing the air flow; The dual-angle detection array includes a 90°±5° lateral detector and a 5-15° forward detector. The 90°±5° lateral detector is located on the positive side of the extinction gas chamber, and the 5-15° forward detector is located in the forward direction of the extinction gas chamber. The dual-angle detection array forms an orthogonal optical path with the laser beam emitted from the extinction gas chamber; The reference light compensation module uses an independent detector to monitor the laser intensity in real time for compensating the light source fluctuation. The compensation formula is: Where C is the PM0.1 concentration after compensation; K is the calibration coefficient, a proportionality coefficient determined by the standard PM0.1 aerosol experiment, dimensionless; I 90° is the 90° side-scattering light intensity, that is, the scattered light intensity received by the detector in the direction of 90°±5°, with the unit of μW / cm 2 ; I 5° is the forward 5-15° scattered light intensity, that is, the scattered light intensity received by the detector in the 5-15° direction, with the unit of μW / cm 2 ; α is the dynamic weight factor, that is, the weighting coefficient of the forward scattering signal, with the value range of 0.3 to 0.5; Q is the air volume passing through the extinction cell per unit time, with the unit of L / min; t is the sampling time, that is, the integration time for single-concentration calculation, with the unit of minute; Iref is the reference light intensity, that is, the laser intensity directly detected by the independent detector, with the unit of μW / cm 2 ; The signal preprocessing module is used to receive the scattered light signal output by the dual-angle detection array and perform phase-locked amplification and dark current compensation processing in sequence; The signal processing and calculation module is used to correct the light intensity based on the preprocessed signal through reference light normalization and temperature compensation, and calculate the final PM0.1 concentration based on the corrected light intensity; The output module is used to output the final PM0.1 concentration detection result.

2. The PM0.1 concentration detection sensor based on multi-angle laser scattering according to claim 1, characterized in that, The roughness Ra of the alumina matte coating is ≤0.5μm, and the stray light suppression rate is >99.5%; 3. The PM0.1 concentration detection sensor based on multi-angle laser scattering according to claim 1, characterized in that, The volume of the extinction gas chamber ≤ 5 cm 3 .

4. The PM0.1 concentration detection sensor based on multi-angle laser scattering according to claim 1, characterized in that, The 90°±5° lateral detector uses an APD detector to collect Mie scattering signals, and the responsivity is 0.7A / W@405nm; 5. The PM0.1 concentration detection sensor based on multi-angle laser scattering according to claim 4, wherein The 5-15° forward detector uses a photodiode to collect Rayleigh scattering signals, and the responsivity is >0.5A / W@405nm; 6. A method for detecting the PM0.1 concentration by using the sensor according to claims 1 to 5, characterized in that, It includes the following steps: Step 1, system initialization: 1) Optical path calibration: The laser module emits 405nm violet light, and the collimating lens forms a parallel light beam with a divergence angle <0.5°; The reference light compensation module monitors the laser intensity in real time and establishes a reference value Iref_base; 2) Gas chamber preprocessing: The constant-speed fan is started to purge the extinction gas chamber at a flow rate of 0.5L / min±5% to remove residual particles; 3) Parameter loading: Calibration coefficient K, dynamic weight factor look-up table library, and temperature compensation coefficient are read from the EEPROM; Step 2, scattered light signal acquisition: 1) Optical path configuration: The laser beam is perpendicularly incident on the center of the extinction gas chamber and is orthogonal to the air flow direction, with a flow velocity of 2m / s±10%; 2) Signal acquisition: 90° lateral scattering light intensity I 90 °: The Mie scattering signal is collected by an APD detector, with a responsivity of 0.7 A / W @ 405 nm; The forward scattered light intensity I5° at 5°: The Rayleigh scattering signal is collected through a photodiode, and the responsivity is 0.5A / W@405nm; The reference light intensity I_ref: The laser intensity is monitored in real time through an independent detector to compensate the light source fluctuation; 3) Sampling strategy: Synchronously collect I every 0.5 seconds 90 °, I5°, I_ref, and collect 100 groups of data in total and take the mean value to reduce random noise; Step 3, signal preprocessing: 1) Phase-locked amplification: The signal passes through a 50kHz band-pass filter to suppress ambient light and circuit noise, and the noise suppression ratio is >40dB; 2) Dark current compensation: Subtract the detector dark current, with the APD detector dark current < 10 nA @ 25 °C); Step 4, signal processing and algorithm fusion; 1) Calculation of dynamic weight factor α: According to the current light intensity ratio Query the particle size distribution library to determine the α value. When the light intensity ratio > 2, α = 0.3; When the light intensity ratio < 1, α = 0.5; 2) Normalization of reference light: Calculate real-time normalization factor Compensate for laser power drift; Corrected light intensity: I 90_norm = I 90_corrected · norm_factor, I 5_norm = I 5_corrected · norm_factor; 3) Temperature compensation: Read the temperature sensor value (±0.5 °C accuracy) and apply a second-order polynomial to correct the light intensity: I 90_temp = I 90_norm ·(1 + a·T + b·T 2 ), I 5_temp = I 5_norm ·(1 + a·T + b·T 2 ) Coefficient a = -0.002 / °C, coefficient b = 0.0001 / °C 2 ; Step 5, concentration calculation and output: 1) Application of concentration formula: Parameter values: Q = 0.5 L / min, t = 0.5 min; 2) Range switching: If C > 1000 μg / m 3 , automatically switch to the low-gain mode to expand the dynamic range; 3) Result output: Send the concentration value to the display module or the main control MCU of the air purifier.

7. An air purification device, characterized in that, Including the PM0.1 concentration detection sensor described in any one of claims 1-5, the output module outputs the concentration value through the UART protocol, with a resolution of 0.1 μg / m 3 , the sensor is powered by 5V, and the power consumption ≤ 0.5W.

8. The air purification device according to claim 7, characterized in that, It automatically adjusts the filter wind speed according to the PM0.1 concentration.

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