Anti-interference point type laser smoke detector and detection method

Abstract

The invention belongs to the field of fire smoke detection, and discloses an anti-interference point type laser smoke detector and a detection method. The detector comprises an optical darkroom, a processing module and an alarm module, a light source module and a photodiode are arranged in the optical darkroom; the light source module comprises a blue laser light source, a green laser light source and an infrared laser light source, and included angles between emergent light rays of the blue laser light source and the green laser light source at a convergent point and scattered light rays scattered to the photodiode are acute angles; the included angle between the emergent light of the infrared laser light source at the convergent point and the scattered light scattered to the photodiode is an obtuse angle; and the processing module is used for identifying fire smoke. According to the detector, the fire smoke type can be accurately identified according to multiple physical parameters of the aerosol, false alarms during detection are remarkably reduced, and the response speed is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to fire alarms, and more specifically, relates to an anti-interference point-type laser smoke detector and a detection method. Background Art

[0002] Smoke detection is a key technology for protecting the lives and property of citizens during fires, especially in today's society where fire and electricity usage are high. Point-type laser smoke detectors utilize the principle of light scattering. Based on the coupling between scattered light intensity and characteristic parameters such as smoke particle size and concentration, they collect scattered light signals generated by the laser beam on the surface of smoke particles to achieve highly sensitive smoke detection, providing higher detection efficiency and accuracy in many complex scenarios. This technology not only significantly improves the response speed of fire alarm systems, but also provides a more reliable early warning method for fires in key scenarios such as smart buildings, industrial plants, and tunnel transportation. Therefore, researching and promoting point-type laser smoke detection technology has important engineering value and application prospects for improving public safety and promoting intelligent fire monitoring.

[0003] Currently, photoelectric smoke detectors on the market still commonly use single- or dual-wavelength light waves to detect fire smoke. For example, Chinese invention patent specification CN112330918A (application publication number) proposes using a dual-band smoke detector to emit two wavelengths of light waves to detect and identify smoke. The reflected wave signal is transmitted to a signal processing circuit board, and after a threshold is set, an alarm is determined to achieve active, real-time detection of fire smoke. Chinese invention patent specification CN118230492A (application publication number) uses two wavelengths of light, near-infrared and blue light, to distinguish different types of smoke particles. Specifically, a photodiode (PD) receives the photocurrent reflected by smoke particles from the two wavelengths, calculates the average particle size of the particles, and determines whether they are fire particles based on the particle size range of the fire smoke particles. This method can, to a certain extent, distinguish interfering smoke and reduce the detector's false alarm rate. However, simulations and experiments revealed that the use of dual-wavelength light still has certain limitations. Smoke detectors based on dual-wavelength light are still unable to effectively distinguish interference sources, especially kitchen fume interference sources, and have an extremely high false alarm rate. This requires long periods of signal detection and complex calculations to accurately determine the source of fume interference, seriously affecting the real-time and reliability of the fire warning system. Summary of the Invention

[0004] In response to the above defects or improvement needs of the prior art, the present invention provides an anti-interference point-type laser smoke detector and a detection method, thereby solving the technical problem of high false alarm rate of fire detection in the prior art.

[0005] To achieve the purpose of the present invention, in a first aspect, an anti-interference point-type laser smoke detector is provided, comprising: an optical darkroom, a processing module and an alarm module; a light source module and a photodiode are provided in the optical darkroom;

[0006] The light source module includes a blue laser light source, a green laser light source, and an infrared laser light source, which are sequentially arranged around the inner wall of the optical darkroom. The angles between the outgoing light of the blue laser light source and the green laser light source at the convergence point and the scattered light scattered to the photodiode are both acute angles, and the angle between the outgoing light of the infrared laser light source at the convergence point and the scattered light scattered to the photodiode is obtuse. The convergence point is the convergence point of the light sources in the light source module;

[0007] The processing module is used to perform the following operations: S1: obtain the scattered light intensity value of each light source, and subtract it from the scattered light intensity value received when no aerosol is introduced into the optical darkroom to obtain the blue laser scattered light intensity change value P B , Green laser scattered light intensity change value P G and the change in the intensity of the infrared laser scattered light P I ; S2: When P B Greater than the preset threshold P G Greater than the preset threshold and P I Greater than the preset threshold When R2 is less than the preset threshold R, record the current R1 and R2; S3: judge when R2 is less than the preset threshold R 2TH1 Or R2 is greater than the preset upper threshold R 2TH2 , and R1 is greater than the preset upper threshold R 1TH2 When R1 is greater than or equal to the preset lower threshold R 1TH1 Less than or equal to the preset upper threshold R 1TH2 , and R2 is greater than or equal to the preset threshold lower limit R 2TH1 Less than or equal to the preset upper threshold R 2TH2 When the alarm module sends an alarm signal;

[0008] Among them, R1 and R2 satisfy the relationship:

[0009] As a preferred embodiment of the present invention, the wavelength of the blue laser light source is 435-450 nm, the wavelength of the green laser light source is 492-577 nm, and the wavelength of the infrared laser light source is 1000-1700 nm.

[0010] As a preferred embodiment of the present invention, the angle between the outgoing light of the blue laser light source at the convergence point and the scattered light scattered to the photodiode is 15°-45°, the angle between the outgoing light of the green laser light source at the convergence point and the scattered light scattered to the photodiode is 25°-55°, and the angle between the outgoing light of the infrared laser light source at the convergence point and the scattered light scattered to the photodiode is 135°-165°.

[0011] As a preferred embodiment of the present invention, the angle between the outgoing light of the blue laser light source at the convergence point and the scattered light scattered to the photodiode is 30°, the angle between the outgoing light of the green laser light source at the convergence point and the scattered light scattered to the photodiode is 40°, and the angle between the outgoing light of the infrared laser light source at the convergence point and the scattered light scattered to the photodiode is 150°.

[0012] As a preferred embodiment of the present invention, in S3 of the processing module, when R2 is less than the preset threshold value R 2TH1 Or R2 is greater than the preset upper threshold R 2TH2 , and R1 is greater than the preset upper threshold R 1TH2 , it is determined to be white smoke from a fire, and an alarm signal is sent out through the alarm module; when R1 is greater than or equal to the preset lower threshold R 1TH1 Less than or equal to the preset upper threshold R 1TH2 , and R2 is greater than or equal to the preset threshold lower limit R 2TH1 Less than or equal to the preset upper threshold R 2TH2 When the smoke is emitted, it is determined to be a fire and an alarm signal is sent out through the alarm module.

[0013] As a preferred embodiment of the present invention, both R1 and R2 are obtained by solving the scattered light intensity value and the corresponding relationship obtained by introducing fire smoke and interfering aerosol with known particle size, refractive index and ellipsoidality into the optical darkroom;

[0014] The fire smoke includes black smoke and white smoke; and the interfering aerosol includes unthawed minced meat fume, water vapor and dust.

[0015] As a preferred embodiment of the present invention, the blue laser light source, the green laser light source, the infrared laser light source and the photodiode are all arranged on the same plane.

[0016] In another aspect of the present invention, an anti-interference point laser smoke detection method is provided, which uses any of the fire smoke detectors described above for detection, comprising the following steps:

[0017] S1: Obtain the scattered light intensity value of each light source and compare it with the scattered light intensity value received when no aerosol is introduced into the optical darkroom. After subtraction, the blue laser light source scattered light intensity change value P B , Green laser light source scattered light intensity change value P G And the change value P of the scattered light intensity of the infrared laser light source and the green laser light source I ;

[0018] S2: When P B Greater than the preset threshold P G Greater than the preset threshold and P I Greater than the preset threshold When , record the current R1 and R2;

[0019] S3: Determine when R2 is less than the preset threshold R 2TH1 Or R2 is greater than the preset upper threshold R 2TH2 , and R1 is greater than the preset upper threshold R 1TH2 When R1 is greater than or equal to the preset lower threshold R 1TH1 Less than or equal to the preset upper threshold R 1TH2 , and R2 is greater than or equal to the preset threshold lower limit R 2TH1 Less than or equal to the preset upper threshold R 2TH2 When the alarm module sends an alarm signal;

[0020] Among them, R1 and R2 satisfy the relationship:

[0021] As a preferred embodiment of the present invention, in the step S3,

[0022] When R1 is greater than or equal to the preset lower threshold R 1TH1 Less than or equal to the preset upper threshold R 1TH2 , and R2 is greater than or equal to the preset threshold lower limit R 2TH1 Less than or equal to the preset upper threshold R 2TH2 When the black smoke is detected, it is determined to be a fire, and an alarm signal is sent out through the alarm module;

[0023] When R2 is less than the preset lower threshold R 2TH1 Or R2 is greater than the preset upper threshold R 2TH2 , and R1 is greater than the preset upper threshold R 1TH2 , it is determined to be white smoke from a fire, and an alarm signal is sent out through the alarm module;

[0024] When R1 is greater than or equal to the preset lower threshold R 1TH1 Less than or equal to the preset upper threshold R 1TH2 , and R2 is less than the preset threshold value R 2TH1 , it is determined to be an interfering aerosol and no alarm signal is triggered;

[0025] When R1 and R2 fall outside the above situations, they are both determined to be interfering aerosols and no alarm signal is triggered.

[0026] As a preferred embodiment of the present invention, the step S1 includes:

[0027] Initialization: In an environment without fire smoke, start each light source in turn and obtain the scattered light intensity value of the scattered light from the corresponding light source received by the photodiode. After filtering, the background value of each signal is obtained and recorded as the blue laser scattered light intensity value. Green laser scattered light intensity value Infrared laser scattered light intensity value

[0028] At preset intervals, the blue laser light source, green laser light source, and infrared laser light source are turned on in sequence to send three optical pulse signals. The scattered light intensity values ​​of the scattered light from the corresponding light sources received by the photodiode are obtained, and the background values ​​of each signal are subtracted to obtain the blue laser scattered light intensity change values ​​P and P, respectively. B , Green laser scattered light intensity change value P G and the change in the intensity of the infrared laser scattered light P I .

[0029] In general, the above technical solutions conceived by the present invention have the following technical advantages compared with the existing technology:

[0030] 1. This invention proposes an anti-interference point-type laser smoke detector. Leveraging the laser's collimation and slow attenuation characteristics, the optical path structure of the invention is designed by deploying three laser light sources of different wavelengths, replacing the light-emitting diodes (LEDs) commonly used in photoelectric smoke detectors. This optical path structure significantly improves the ability to identify smoke particle size and shape, thereby effectively enhancing the anti-interference performance of smoke detection, significantly reducing false alarms in complex fire detection environments, and improving detection responsiveness.

[0031] 2. The present invention takes into account both performance and structural design difficulty, and optimizes the layout angles of the three laser light sources so that each laser light source can achieve optimal coverage and minimal interference overlap in an optical darkroom, thereby improving overall detection stability and discrimination resolution.

[0032] 3. Since methane gas has the best absorption effect on monochromatic light with a wavelength of about 1653.7nm, the present invention preferably uses infrared light as one of the laser light sources, which provides feasibility for the design of subsequent methane smoke composite detectors.

[0033] 4. The present invention proposes to combine the point laser smoke detection method with the above-mentioned preferred anti-interference point laser smoke detector hardware structure, and optimize the appropriate alarm threshold to significantly improve the fire alarm response speed and achieve reliable alarm of early fires. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the three-dimensional structure of the anti-interference point-type laser smoke detector used as an example in the present invention;

[0035] Figure 2 1 is a schematic top view of an anti-interference point-type laser smoke detector according to an example of the present invention;

[0036] Figure 3 It is a hardware design block diagram of the present invention as an example of the present invention;

[0037] Figure 4 is a software program flow chart of an example of the present invention;

[0038] Figure 5 This is a diagram of the particle classification results of the actual experiment of the present invention.

[0039] The meanings of the reference numerals in the figure are: 1 is a laser light source emitting green light, 2 is a laser light source emitting blue light, 3 is a laser light source emitting infrared light, 4 is a photodiode receiving laser light, and 5 is a cloud of smoke. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0041] The design concept of this application specifically involves simulations of schemes with different numbers of channels and different wavelengths of light sources, and the relationship between scattered light intensity and different smoke characteristics. To effectively distinguish fire smoke from various interference sources, light sources were arranged at different angles, with increments of 5 degrees. Simulations were also conducted for schemes with single, dual, triple, and multiple wavelengths. The simulation results for single-wavelength, multi-angle scattered light showed that the scattered light intensity characteristics of fire smoke and interference sources were difficult to distinguish. The simulation results for dual-wavelength, multi-angle scattered light showed that there was still a small amount of overlap in the scattered light intensity characteristics of fire smoke and interference sources. The simulation results for a three-wavelength light source showed that compared to the single-wavelength and dual-wavelength schemes, the three-wavelength light source scheme significantly improved anti-interference capabilities and effectively reduced false alarms. Simulation tests for schemes with four or more wavelengths showed that while the performance of distinguishing fire smoke from interference sources improved, the effect was not significant. Considering that the introduction of more light sources would increase the difficulty of optical path design, the present invention adopts a three-wavelength light source as the optimal solution that strikes a balance between performance and structural design. Furthermore, when using three light sources—blue, green, and infrared—as incident light sources, processing and analyzing the scattered light intensity signal revealed differences in the response characteristics of fire smoke and interference sources, demonstrating that a preliminary distinction between fire smoke and interference sources has been achieved. Subsequent optical path and circuit design was conducted based on these simulation results. Specifically, the wavelengths and angles that maximized the distinction between standard fire aerosols and interference source aerosols were selected. Furthermore, consideration was given to other factors, such as the need to avoid interference from external ambient light sources when collecting light scattering signals and ensuring that smoke could enter the detection area. The detector's optical chamber design determined the placement of the light source and photodiode.

[0042] Based on the above design ideas and the design of the detector, the size of the hardware circuit is determined, and the circuit design is completed according to the functional requirements. Figure 1-Figure 2 As shown, the anti-interference point-type laser smoke detector designed by the present invention includes: an optical darkroom, a light source module, a photodiode, a processing module and an alarm module;

[0043] The optical darkroom is provided with a plurality of through holes for introducing the aerosol to be detected;

[0044] The photodiode is set on the inner wall of the optical darkroom, and is used to receive the light signal generated by the scattering of aerosol particles and convert it into a corresponding electrical signal output;

[0045] The light source module includes three laser light sources, namely a blue laser light source, a green laser light source, and an infrared laser light source, which are arranged in sequence around the inner wall of the optical darkroom. The angles between the outgoing light of the blue laser light source and the green laser light source at the convergence point and the scattered light scattered to the photodiode are both acute angles, and the angle between the outgoing light of the infrared laser light source at the convergence point and the scattered light scattered to the photodiode is obtuse angle; wherein the convergence point is the common convergence point of each light source in the light source module;

[0046] The processing module is used to perform the following operations:

[0047] S1: Every preset sampling period, turn on the blue laser light source, green laser light source and infrared laser light source in turn and record the AD sampling value of the three-way light scattering signal intensity received by the photodiode, and subtract it from the scattered light intensity value received by the photodiode when no aerosol is introduced into the optical darkroom to obtain the blue laser light source scattered light intensity change value P B , Green laser light source scattered light intensity change value P G And the change value P of the scattered light intensity of the infrared laser light source and the green laser light source I ;

[0048] S2: When P B Greater than the preset threshold P G Greater than the preset threshold and P I Greater than the preset threshold When , record the ratios R1 and R2 between the intensities of the two different laser light sources;

[0049] S3: Determine when R2 is less than the preset threshold R 2TH1 Or R2 is greater than the preset upper threshold R 2TH2 , and R1 is greater than the preset upper threshold R 1TH2 When R1 is greater than or equal to the preset lower threshold R 1TH1 Less than or equal to the preset upper threshold R 1TH2 , and R2 is greater than or equal to the preset threshold lower limit R 2TH1 Less than or equal to the preset upper threshold R 2TH2 When the alarm module sends an alarm signal;

[0050] Among them, R1 and R2 satisfy the relationship:

[0051] The parameter R1 is introduced to characterize the relationship between the green and infrared light scattering intensities, reflecting the particle size characteristics of the measured particles, thereby distinguishing fire smoke from ambient dust. The parameter R2 is introduced to characterize the relationship between the blue and green light scattering intensities, reflecting the particle shape characteristics of the measured particles, and is used to distinguish between white smoke and oil smoke, which have similar particle sizes but different shapes. By jointly analyzing parameters R1 and R2, effective differentiation of different smoke types is achieved.

[0052] In the present invention, the wavelength of the blue laser light source is 435-450 nm, the wavelength of the green laser light source is 492-577 nm, and the wavelength of the infrared laser light source is 1000-1700 nm.

[0053] like Figure 3 As shown in the figure, this hardware design block diagram illustrates the circuit design of an anti-interference point-type laser smoke detector. This circuit system uses a 5V DC power supply to provide unified power to the system. The entire system consists of multiple modules, including a light source module, a photoelectric detection module, a signal conditioning module, a processing module (hereinafter referred to as the MCU module), and an alarm module.

[0054] The light source module includes three lasers: a blue laser, a green laser, and an infrared laser. These three lasers are controlled to emit laser light in sequence. If smoke particles are present in the optical darkroom, they will generate a strong scattered light signal. The MCU timing control logic ensures that the three laser light sources operate alternately.

[0055] The photoelectric detection module, consisting of a photodiode, is located on the inner wall of the optical darkroom. It receives the light signal generated by aerosol particle scattering and converts it into a corresponding electrical signal output. This electrical signal is first amplified and filtered by the signal conditioning circuit before being sent to the MCU for ADC sampling, which converts the analog signal into a digital signal.

[0056] The MCU module, as the core control and processing unit, performs several key functions, including controlling the timing of light source emission, ADC sampling, executing anti-interference intelligent recognition algorithms, and determining alarm conditions. After collecting the intensity of the three optical signals, the MCU calculates the current smoke type based on preset thresholds and characteristic ratios and determines whether to trigger an alarm condition. If it determines that the smoke is from a fire, the MCU drives the LED light alarm module through the control output interface to generate an alarm.

[0057] In some embodiments, a specific spatial angle is formed between the three laser light sources and the photodiode to achieve efficient scattering area coverage and signal separation. Among them, the angle between the outgoing light of the blue laser light source at the convergence point and the scattered light scattered to the photodiode is 15°-45°, the angle between the outgoing light of the green laser light source at the convergence point and the scattered light scattered to the photodiode is 25°-55°, and the angle between the outgoing light of the infrared laser light source at the convergence point and the scattered light scattered to the photodiode is 135°-165°. Preferably, the angles between the blue laser light source, the green laser light source and the infrared laser light source and the photodiode are 30°, 40° and 150° respectively. This angle combination has been verified by optimized simulation and actual measurement, and can significantly improve the difference in scattering signals of different types of smoke particles and enhance the accuracy of distinguishing fire smoke from interference source smoke.

[0058] In some embodiments, the three lasers and the photodiode are coplanar and installed on the same plane of the detector structure, which helps to simplify the system structure and improve detection accuracy.

[0059] The present invention also provides an anti-interference point laser smoke detector and detection method, that is, a design method for a point laser smoke detector that uses three different wavelength lasers to distinguish between fire smoke and interference sources. The software program flow chart is as follows: Figure 4 As shown, the following steps are included:

[0060] Step 1: Initialize the system. In a smoke-free environment, turn on the blue laser light source, green laser light source, and infrared laser light source in sequence. Record the AD sampling values ​​of the three-way light scattering signal intensity received by the photodiode respectively, and then use the sliding smoothing filter algorithm to The background value of the three-way light scattering signal intensity is filtered, that is, as the background value of each signal, it is recorded as the scattered light intensity value of the blue light signal emitted by the blue light source. The scattered light intensity value of the green light signal emitted by the green light source The scattered light intensity value of the red light signal emitted by the infrared light source

[0061] Step 2: At every time t, turn on the blue laser light source, green laser light source, and infrared laser light source in sequence to send three optical pulse signals. Subtract the filtered background value from the AD sampling value of the three-way light scattering signal intensity received by the photodiode. Denoted as blue light scattering signal P B , green light scattering signal P G , red light scattering signal P I ;

[0062] Step 3: When the light scattering signals P corresponding to the blue laser light source, the green laser light source, and the infrared laser light source are B 、P G 、P I Are higher than the corresponding preset threshold value When the pre-researched anti-interference intelligent recognition algorithm is combined, otherwise return to step 2 to loop. Here, the parameter R1 is specifically introduced to represent the relationship between the scattered light intensity of the green laser light source and the scattered light intensity of the infrared laser light source, and the parameter R2 is introduced to represent the relationship between the scattered light intensity of the blue light and the scattered light intensity of the green light, that is, when R2 is less than the preset threshold lower limit R 2TH1 Or R2 is greater than the preset upper threshold R 2TH2 , and R1 is greater than the preset upper threshold R 1TH2 When R1 is greater than or equal to the preset lower threshold R 1TH2 Less than or equal to the preset upper threshold R 1TH2 , and R2 is greater than or equal to the preset threshold lower limit R 2TH1 Less than or equal to the preset upper threshold R 2TH2 When an alarm occurs, an alarm signal is sent out through the alarm module;

[0063] Among them, R1 and R2 satisfy the relationship:

[0064] Furthermore, the specific method for distinguishing smoke types in step 3 is as follows:

[0065] Step 3.1: According to the experimental test results, the lower limit of the threshold of R1 is preset to R 1TH1 , the upper threshold is R 1TH2 , the lower threshold of R2 is R 2TH1 , the upper threshold is R 2TH2 If R1 is between the preset lower threshold R 1TH1 and the preset upper threshold R 1TH2 If R2 is less than the preset lower threshold R 2TH1 , the smoke type is determined to be interference source dust, and no alarm signal is triggered. If R2 is between the preset threshold lower limit R 2TH1 and the preset upper threshold R 2TH2 When the value is between (including both end points), the current smoke type is determined to be black smoke and an alarm signal is triggered;

[0066] Step 3.2: When R2 is less than the preset threshold R 2TH1 Or R2 is greater than the preset upper threshold R 2TH2 Under the condition that R1 is greater than the preset upper threshold R 1TH2 The current smoke type can be determined to be white smoke, triggering an alarm signal;

[0067] Step 3.3: If R1 and R2 are in a range other than that in Step 3.1 and Step 3.2, the current smoke is regarded as interference source smoke and no alarm signal is triggered.

[0068] Among them, through the joint analysis of parameters R1 and R2, different smoke types can be effectively distinguished. The design idea is:

[0069] (1) The mathematical expression of the "three-stage" theoretical model of particle scattered light is shown in the following formula (1). According to the theoretical model, when the wavelength of light is close to the aerosol particle size, the scattered light intensity is approximately proportional to the volume of the aerosol. When the wavelength of light is much smaller than the aerosol particle size, the scattered light intensity is approximately proportional to the surface area of ​​the aerosol. Therefore, the parameter R1 selected by the present invention is the ratio of the scattered signal of the green laser light source to the light signal of the infrared laser light source. By measuring the aerosol particle size, the distinction between fire smoke and dust is achieved.

[0070]

[0071] Where I SI , I SII , I SIII are the scattered light intensity values ​​when the wavelength is much larger than the aerosol particle size, close to the aerosol particle size, and much smaller than the aerosol particle size, respectively. I is the conversion coefficient between particle size and scattered light intensity, x is the particle size, and λ is the wavelength of the incident laser.

[0072] (2) Since the particle sizes of white smoke and some oil smoke are similar, they cannot be distinguished by particle size. The research results show that white smoke from fire is generally long chain-shaped, while kitchen oil smoke is generally spherical. Based on the simulation results and experimental results, the parameter R2 selected by the present invention is the ratio of the blue light scattering signal to the green light scattering signal, which is used to distinguish white smoke from oil smoke.

[0073] In some embodiments, a photodiode serves as the core photoelectric conversion element, directly converting the incident light scattering signal into a photocurrent signal that responds linearly with light intensity through the photoelectric effect. Specifically, as the light scattering intensity increases, the photodiode output current increases accordingly. To achieve anti-interference and signal adaptation, the present invention constructs an integral filter circuit based on an operational amplifier, performs time-domain integration processing on the photocurrent, and converts the current signal into a voltage signal with noise suppression characteristics. The conversion relationship is shown in the following equation. This circuit effectively filters high-frequency noise and ensures that the output voltage amplitude maintains a corresponding relationship with the original light signal intensity. The digital value ultimately collected by the AD converter is a direct quantization value representing the light scattering signal intensity P.

[0074]

[0075] Where U is the collected voltage signal, I is the current of the photodiode, C is the capacitance of the integrating capacitor, and T is the integration time, which is generally tens of milliseconds. T is determined by iterative analysis of experimental data.

[0076] In some embodiments, in step 1, considering the computing power of the single-chip microcomputer selected for the hardware circuit of the present invention and the detector response time requirements, the sliding window size N of the sliding smoothing filter is set to 20, and the background value of the light scattering signal intensity in the test environment when there is no smoke is filtered.

[0077] In some embodiments, in step 3, the determination threshold value of the light scattering signal intensity is The threshold value R of the light scattering signal intensity ratio 1TH1 、R 1TH2 、R 2TH1 、R 2TH2 They are all determined by experimental data in a controlled laboratory environment based on the light scattering characteristics of known smoke samples. Among them, the ratio of the green light scattering signal to the infrared light scattering signal R1 reflects the particle size characteristics of the aerosol particles, and the lower limit of the particle size characteristic threshold is R 1TH1 , the upper limit is R 1TH2 The ratio of blue light scattering signal to green light scattering signal R2 reflects the particle shape characteristics of aerosol particles. The lower limit of the particle shape characteristic threshold is R 2TH1 , the upper limit is R 2TH2 .

[0078] To verify the performance advantages of the anti-interference point-type laser smoke detector proposed in this invention, we conducted comparative experiments. Several mainstream photoelectric smoke detectors were selected as comparison samples. These were placed in the same experimental environment as the anti-interference point-type laser smoke detector designed in this invention. Experiments were conducted simultaneously under typical fire smoke (such as black smoke and white smoke) and common interference sources (such as oil smoke, water vapor, and dust).

[0079] Experimental results show that traditional photoelectric smoke detectors suffer from frequent false alarms and poor stability when exposed to interference sources such as dust, water vapor, and oil smoke. They also exhibit slow response speeds when exposed to standard fire particles. Under the same conditions, the anti-interference point-type laser smoke detector of the present invention demonstrates significant advantages: faster response speed, enabling rapid early warning of fires, an extremely low false alarm rate, and excellent recognition and anti-interference capabilities for interference sources such as oil smoke and water vapor.

[0080] Finally, we statistically analyzed the scattered light signal data collected by the detector of the present invention, and combined with the proposed parameter models R1 and R2, we plotted the following: Figure 5The experimental particle classification results are shown in the figure. It can be clearly seen from the figure that different types of aerosol particles show good clustering characteristics in the parameter space, and the boundary between fire smoke and interference sources is clear, further verifying that the detector of the present invention has the ability to identify smoke types with high precision and high stability.

[0081] Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if such modifications and variations fall within the scope of protection of the present invention and its equivalents, the present invention is intended to include such modifications and variations. The above-described embodiments are merely preferred embodiments for the purpose of fully illustrating the present invention and are not intended to limit the scope of protection. Any equivalent substitutions or modifications made by those skilled in the art based on the present invention are also within the scope of protection of the present invention.

Claims

1. An anti-interference point-type laser smoke detector, characterized in that: include: An optical darkroom, a processing module and an alarm module; the optical darkroom is provided with a light source module and a photodiode; The light source module includes a blue laser light source, a green laser light source, and an infrared laser light source, which are sequentially arranged around the inner wall of the optical darkroom. The angles between the outgoing light of the blue laser light source and the green laser light source at the convergence point and the scattered light scattered to the photodiode are both acute angles, and the angle between the outgoing light of the infrared laser light source at the convergence point and the scattered light scattered to the photodiode is obtuse. The convergence point is the convergence point of the light sources in the light source module; The processing module is used to perform the following operations: S1: obtain the scattered light intensity value of each light source, and subtract it from the scattered light intensity value received when no aerosol is introduced into the optical darkroom to obtain the blue laser scattered light intensity change value P B , Green laser scattered light intensity change value P G and the change in the intensity of the infrared laser scattered light P I ; S2: When P B Greater than the preset threshold P G Greater than the preset threshold and P I Greater than the preset threshold When R2 is less than the preset threshold R, record the current R1 and R2; S3: judge when R2 is less than the preset threshold R 2TH1 Or R2 is greater than the preset upper threshold R 2TH2 , and R1 is greater than the preset upper threshold R 1TH2 When R1 is greater than or equal to the preset lower threshold R 1TH1 Less than or equal to the preset upper threshold R 1TH2 , and R2 is greater than or equal to the preset threshold lower limit R 2TH1 Less than or equal to the preset upper threshold R 2TH2 When the alarm module sends an alarm signal; Among them, R1 and R2 satisfy the relationship:

2. The anti-interference point-type laser smoke detector according to claim 1, characterized in that: The wavelength of the blue laser light source is 435-450 nm, the wavelength of the green laser light source is 492-577 nm, and the wavelength of the infrared laser light source is 1000-1700 nm.

3. The anti-interference point-type laser smoke detector according to claim 1, characterized in that: The angle between the outgoing light of the blue laser light source at the convergence point and the scattered light scattered to the photodiode is 15°-45°, the angle between the outgoing light of the green laser light source at the convergence point and the scattered light scattered to the photodiode is 25°-55°, and the angle between the outgoing light of the infrared laser light source at the convergence point and the scattered light scattered to the photodiode is 135°-165°.

4. The anti-interference point-type laser smoke detector according to claim 1, characterized in that: The angle between the outgoing light of the blue laser light source at the convergence point and the scattered light scattered to the photodiode is 30°, the angle between the outgoing light of the green laser light source at the convergence point and the scattered light scattered to the photodiode is 40°, and the angle between the outgoing light of the infrared laser light source at the convergence point and the scattered light scattered to the photodiode is 150°.

5. The anti-interference point-type laser smoke detector according to claim 1, characterized in that: In step S3 of the processing module, when R2 is less than the preset lower threshold R 2TH1 Or R2 is greater than the preset upper threshold R 2TH2 , and R1 is greater than the preset upper threshold R 1TH2 , it is determined to be white smoke from a fire, and an alarm signal is sent out through the alarm module; when R1 is greater than or equal to the preset threshold lower limit R 1TH1 Less than or equal to the preset upper threshold R 1TH2 , and R2 is greater than or equal to the preset threshold lower limit R 2TH1 Less than or equal to the preset upper threshold R 2TH2 When the smoke is emitted, it is determined to be a fire and an alarm signal is sent out through the alarm module.

6. The anti-interference point-type laser smoke detector according to claim 1, characterized in that: R1 and R2 are both obtained by solving the scattered light intensity value and the corresponding relationship obtained by introducing fire smoke and interfering aerosol with known particle size, refractive index and ellipsoidality into the optical darkroom; The fire smoke includes black smoke and white smoke; and the interfering aerosol includes unthawed minced meat fume, water vapor and dust.

7. The anti-interference point-type laser smoke detector according to claim 1, characterized in that: The blue laser light source, the green laser light source, the infrared laser light source and the photodiode are all arranged on the same plane.

8. An anti-interference point-type laser smoke detector and detection method, characterized in that: The fire smoke detector according to any one of claims 1 to 7 is used for detection, comprising the following steps: S1: Obtain the scattered light intensity value of each light source and compare it with the scattered light intensity value received when no aerosol is introduced into the optical darkroom. After subtraction, the blue laser light source scattered light intensity change value P B , Green laser light source scattered light intensity change value P G And the change value P of the scattered light intensity of the infrared laser light source and the green laser light source I ; S2: When P B Greater than the preset threshold P G Greater than the preset threshold and P I Greater than the preset threshold When , record the current R1 and R2; S3: Determine when R2 is less than the preset threshold R 2TH1 Or R2 is greater than the preset upper threshold R 2TH2 , and R1 is greater than the preset upper threshold R 1TH2 When R1 is greater than or equal to the preset lower threshold R 1TH1 Less than or equal to the preset upper threshold R 1TH2 , and R2 is greater than or equal to the preset threshold lower limit R 2TH1 Less than or equal to the preset upper threshold R 2TH1 When the alarm module sends an alarm signal; Among them, R1 and R2 satisfy the relationship:

9. The anti-interference point-type laser smoke detector and detection method according to claim 8, characterized in that: In the S3 step, When R1 is greater than or equal to the preset lower threshold R 1TH1 Less than or equal to the preset upper threshold R 1TH2 , and R2 is greater than or equal to the preset threshold lower limit R 2TH1 Less than or equal to the preset upper threshold R 2TH2 When the black smoke is detected, it is determined to be a fire, and an alarm signal is sent out through the alarm module; When R2 is less than the preset lower threshold R 2TH1 Or R2 is greater than the preset upper threshold R 2TH2 , and R1 is greater than the preset upper threshold R 1TH2 , it is determined to be white smoke from a fire, and an alarm signal is sent out through the alarm module; When R1 is greater than or equal to the preset lower threshold R 1TH1 Less than or equal to the preset upper threshold R 1TH2 , and R2 is less than the preset threshold value R 2TH1 , it is determined to be an interfering aerosol and no alarm signal is triggered; When R1 and R2 fall outside the above situations, they are both determined to be interfering aerosols and no alarm signal is triggered.

10. The anti-interference point-type laser smoke detector and detection method according to claim 8, characterized in that: In the step S1, it includes: Initialization: In an environment without fire smoke, start each light source in turn and obtain the scattered light intensity value of the scattered light from the corresponding light source received by the photodiode. After filtering, the background value of each signal is obtained and recorded as the blue laser scattered light intensity value. Green laser scattered light intensity value Infrared laser scattered light intensity value At preset intervals, the blue laser light source, green laser light source, and infrared laser light source are turned on in sequence to send three optical pulse signals. The scattered light intensity values ​​of the scattered light from the corresponding light sources received by the photodiode are obtained, and the background values ​​of each signal are subtracted to obtain the blue laser scattered light intensity change values ​​P and P, respectively. B , Green laser scattered light intensity change value P G and the change in the intensity of the infrared laser scattered light P I .

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