A hazardous chemical detection system and method
By using Bessel beam excitation and time-gated technology, combined with mechanical offset components, the problems of insufficient penetration and signal interference in Raman detection in complex media have been solved, enabling efficient and accurate detection of hazardous chemicals.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANCHANG UNIV
- Filing Date
- 2026-05-22
- Publication Date
- 2026-07-14
AI Technical Summary
Existing Raman detection methods have weak penetration and are easily affected by ambient stray light and container autofluorescence when detecting hazardous chemicals in complex scattering media such as closed containers, packaging bags, or turbid liquids, leading to a decrease in detection accuracy.
The signal excitation and acquisition modules, consisting of a nanosecond pulsed laser, a phase modulation device, a lens assembly, and a Raman spectrometer, combined with mechanical offset components and signal control components, achieve non-destructive testing of hazardous chemicals through Bessel beam excitation and time-gated technology.
It significantly improves detection depth, suppresses fluorescence background signals, and enhances the signal-to-noise ratio, enabling flexible detection of hazardous chemicals in complex media.
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Figure CN122385477A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of hazardous chemical detection technology, and in particular to a hazardous chemical detection system and detection method. Background Technology
[0002] Hazardous chemicals are an important part of the national economy; however, systemic safety risks still exist in their production, storage, and transportation, leading to frequent major accidents that seriously endanger people's lives and property and hinder high-quality economic development. Therefore, in recent years, governments worldwide have attached great importance to researching new methods for detecting hazardous chemicals.
[0003] Compared to techniques such as mass spectrometry and gas / liquid chromatography, Raman spectroscopy obtains information on molecular vibration and rotation by analyzing scattering spectra. It can be used for Raman spectroscopy measurements on gaseous, liquid, powder, and various solid samples without special treatment. It has advantages such as being non-invasive and requiring no complicated sample transportation or processing, and is one of the important technological development directions for hazardous chemical detection methods.
[0004] Current Raman detection methods have the following shortcomings in practical applications: (i) It has weak penetrating power and is inadequate when detecting hazardous chemicals in complex scattering media such as sealed containers, packaging bags or turbid liquids. (ii) Raman signals are susceptible to interference from factors such as ambient stray light and container autofluorescence, which reduces the accuracy of detection. Summary of the Invention
[0005] The present invention aims to at least improve one of the technical problems existing in the prior art. To this end, the present invention proposes a hazardous chemical detection system and detection method.
[0006] The technical solution of the present invention is as follows: A hazardous chemical detection system includes a signal excitation module and a signal acquisition module, wherein: The signal excitation module includes a nanosecond pulse laser, a phase modulation device, a first reflector, and a first lens assembly arranged sequentially along the optical path. Based on the phase modulation device, the Gaussian beam generated by the nanosecond pulse laser is converted into a non-diffraction Bessel beam. After being reflected by the first reflector, the beam enters the first lens assembly, forming a spectral detection depth region with stable energy distribution along the propagation direction and consistent lateral dimensions inside the sample under test, so as to obtain the excitation optical path of the sample under test. The signal acquisition module includes: The optical components include a second lens assembly, a conical lens, a Raman filter assembly, a focusing lens, and a Raman spectrometer that propagate along the optical path. The Raman spectrometer has a detector. Based on the second lens assembly and the conical lens, the non-diffraction Bessel beam is converted into parallel light. After being filtered and focused, the light enters the detector for Raman signal acquisition to obtain the collection optical path of the sample to be tested. The mechanical offset component includes a movable electromechanical platform mounted on one side of the signal excitation module. The optical component is mounted on the electromechanical platform. By controlling the electromechanical platform to move in a direction perpendicular to the non-diffraction Bessel beam, the offset distance between the signal collection optical path and the excitation optical path can be adjusted. A signal control component is connected to the nanosecond pulsed laser and the detector, enabling both to set the receiving delay and activation time width for the detector under a unified nanosecond timing reference, thereby suppressing the acquisition of fluorescence signals.
[0007] In one possible technical solution, the signal control component further includes: A clock reference unit, connected to the nanosecond pulse laser and the detector, is used to provide a unified nanosecond timing reference for the nanosecond pulse laser and the detector; A gated delay unit, whose output channels are respectively connected to the gated trigger input terminals of the nanosecond pulse laser and the detector, is used to set the receiving delay of the detector; A gated exposure control unit, connected to the detector, is used to set the duration of the detector's activation and suppress the acquisition of fluorescence signals.
[0008] In one possible technical solution, the phase modulation device is further defined as an axonometric pyramid or a spatial light modulator. When the phase modulation device is an axonometric pyramid, it employs an axonometric pyramid with a base angle of 2° and a cone angle of 176°, which can convert the Gaussian beam generated by the nanosecond pulse laser into a diffraction-free Bessel beam. According to beam propagation theory, the cone angle of the axonometric pyramid is inversely proportional to the diffraction-free distance and directly proportional to the size of the central spot. The 176° cone angle can form an ideal diffraction-free region inside the sample when subsequently used in conjunction with a telescope system.
[0009] In one possible technical solution, the first lens assembly and the second lens assembly have the same structure, both including a pair of achromatic confocal lenses with a focal length ratio of 1:10.
[0010] In one possible technical solution, the first lens assembly further includes: The first and second lenses, set along the optical path, can expand and collimate the original Bessel beam generated by the axial pyramid, compensating for the diffraction effect caused by the longer wavelength, extending the non-diffraction distance before entering the sample to be tested by about 10 mm, and controlling the lateral main lobe diameter to about 20 μm, thereby forming a spectral detection focal depth region with stable energy distribution along the propagation direction and consistent lateral size inside the hazardous chemical to be tested. The second lens assembly includes: The third and fourth lenses, positioned along the optical path, are used to ensure that the light rays in the collection area and the light rays in the excitation area are highly coincident, thus converting the Bessel beam into parallel light.
[0011] In one possible technical solution, the Raman filter assembly further includes a dichroic mirror and a high-pass filter for filtering out elastically scattered background light from the reflected signal of the sample under test and collecting the Raman signal.
[0012] In one possible technical solution, the Raman spectrometer further includes an incident needle, a fifth lens, a second reflecting mirror, a third reflecting mirror, a prism, a converging lens, and a detector arranged sequentially along the optical path, wherein the incident needle has a slit channel and is transmitted to the converging lens via an optical fiber.
[0013] A method for detecting hazardous chemicals, wherein the detection is performed using the hazardous chemical detection system described above, and includes the following: S1, based on the signal control component, set the laser repetition frequency of the nanosecond pulse laser and the detector, and set the trigger mode, gating delay time and opening time width of the detector; S2, acquire the pulsed laser beam emitted by the nanosecond pulsed laser; S3, the phase modulation device receives the pulsed laser beam and modulates it into a Bessel beam; after adjustment by the first reflecting mirror and the first lens assembly, a diffraction-free region is constructed above the sample to be tested and acts on the sample to be tested to generate a pulsed Raman signal beam, which serves as the trigger condition for the detector. S4, drive the electromechanical platform to move to control the offset distance between the second transmission component and the first transmission component, thereby controlling the offset distance between the incident laser and the Raman signal of the sample under test; S5, the pulsed Raman signal beam passes through the second lens assembly and the conical lens. Based on the conical lens, the pulsed Raman signal beam is transformed into a Bessel beam, which is then coupled and focused into the optical fiber by the Raman filter assembly and enters the detector of the Raman spectrometer. S6, the detector receives Raman photons from deep within the sample under test within a window of preset opening time width, achieving non-destructive testing and effectively suppressing long-lived fluorescence background signals.
[0014] A computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the hazardous chemical detection method described above.
[0015] A computer storage medium storing instructions that, when executed on a computer, cause the computer to perform the hazardous chemical detection method described above.
[0016] The hazardous chemical detection system and method according to the present invention have the following advantages: Significantly improved detection depth: The non-diffraction characteristics of Bessel beams result in low attenuation and long focal depth in scattering media, which can effectively excite deep targets and solve the problem of insufficient penetration of traditional Gaussian beams.
[0017] Significantly improved signal-to-noise ratio: Picosecond-precision time gating fundamentally suppresses nanosecond-level fluorescence background, combined with spatial offset technology and spatial filtering via a confocal aperture. By adjusting the Bessel beam ratio and spatial offset distance, the system can flexibly adapt to the detection needs of hazardous chemicals within complex media.
[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 This is an optical schematic diagram of a hazardous chemical detection system according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the device structure of a hazardous chemical detection system according to an embodiment of the present invention; Figure 3 This is a schematic diagram of an ammonium nitrate powder sample with a complex internal structure, representing an embodiment of the present invention. Figure 4 This is a flowchart of a hazardous chemical detection method according to an embodiment of the present invention; Figure 5 This is a Bessel beam excitation and detection depth distribution map of ammonium nitrate powder according to an embodiment of the present invention; Figure 6 This is a spatial offset distribution diagram of the Raman signal of ammonium nitrate powder at different depths according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the excitation and collection sequence of a hazardous chemical detection method according to an embodiment of the present invention; Figure 8 This is a schematic diagram illustrating the effect of the spectral acquisition method according to an embodiment of the present invention.
[0021] Figure label: 1. Nanosecond pulsed laser; 2. Phase modulation device; 3. First reflecting mirror; 8. Conical lens; 10. Focusing lens; 17. Detector; 4. First lens; 5. Second lens; 6. Third lens; 7. Fourth lens; 9. Dichroic mirror; 11. Incident needle; 12. Fifth lens; 13. Second reflecting mirror; 14. Third reflecting mirror; 15. Prism; 16. Converging lens; 17. Detector. Detailed Implementation
[0022] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.
[0023] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component.
[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0025] The terms "first," "second," "third," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects and not to describe a particular order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, it may include a series of steps or units, or optionally, steps or units not listed, or other steps or units inherent to these processes, methods, products, or devices.
[0026] The accompanying drawings show only the portions relevant to this application, not all of them. Before discussing exemplary embodiments in more detail, it should be noted that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe operations (or steps) as sequential processes, many of these operations may be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations may be rearranged. The process may be terminated when its operation is completed, but may also have additional steps not included in the drawings. The process may correspond to a method, function, procedure, subroutine, subprogram, etc.
[0027] The terms “component,” “module,” “system,” “unit,” etc., used in this specification are used to refer to computer-related entities, hardware, firmware, combinations of hardware and software, software, or software in execution. For example, a unit can be, but is not limited to, a process running on a processor, a processor, an object, an executable file, a thread of execution, a program, and / or distributed between two or more computers. Furthermore, these units can be executed from various computer-readable media on which various data structures are stored. Units can communicate, for example, via local and / or remote processes based on signals having one or more data packets (e.g., data from a second unit interacting with another unit between a local system, a distributed system, and / or a network; for example, the Internet interacting with other systems via signals).
[0028] Example 1 like Figures 1 to 8 As shown, this embodiment provides a hazardous chemical detection system, which includes a signal excitation module and a signal acquisition module, wherein: The signal excitation module includes a nanosecond pulse laser 1, a phase modulation device 2, a first reflector 3, and a first lens assembly arranged sequentially along the optical path. Based on the phase modulation device 2, the Gaussian beam generated by the nanosecond pulse laser 1 is converted into a non-diffraction Bessel beam. After being reflected by the first reflector 3, the beam enters the first lens assembly, forming a spectral detection depth region with stable energy distribution along the propagation direction and consistent lateral dimensions inside the sample to be tested, so as to obtain the excitation optical path of the sample to be tested. The signal acquisition module includes: The optical components include a second lens assembly that propagates along the optical path, a conical lens 8, a Raman filter assembly, a focusing lens 10, and a Raman spectrometer. The Raman spectrometer has a detector 17. Based on the second lens assembly and the conical lens 8, the non-diffraction Bessel beam is converted into parallel light. After being filtered and focused, the light enters the detector 17 to collect Raman signals, so as to obtain the collection optical path of the sample to be tested. The mechanical offset component includes a movable electromechanical platform mounted on one side of the signal excitation module. The optical component is mounted on the electromechanical platform. By controlling the electromechanical platform to move in a direction perpendicular to the non-diffraction Bessel beam, the offset distance between the signal collection optical path and the excitation optical path can be adjusted. A signal control component, connected to the nanosecond pulsed laser 1 and the detector 17, enables both to operate under a unified nanosecond timing reference, setting a receiving delay and activation time width for the detector 17 to suppress fluorescence signal acquisition. The signal control component includes: A clock reference unit, connected to the nanosecond pulse laser 1 and the detector 17, is used to provide a unified nanosecond timing reference for the nanosecond pulse laser 1 and the detector 17. The gated delay unit has its output channels connected to the gated trigger input terminals of the nanosecond pulse laser 1 and the detector 17, respectively, and is used to set the receiving delay of the detector 1. Specifically, the gated delay unit can use a digital delay generator and a lock-in amplifier to wait for the surface fluorescence and surface Raman to decay in the short optical path, while waiting for Raman photons from the deep layer of the sample to reach the detection area. The gated exposure control unit is connected to the detector 1 and is used to set the time width of the detector 1 to suppress the acquisition of fluorescence signals.
[0029] It should be noted that, in this embodiment, the nanosecond pulse laser uses a wavelength of 785nm, a single pulse energy of 1mJ, a pulse width of 10ns, an emitted laser diameter of 10mm, and a repetition frequency that is adjustable in the range of 20Hz to 1KHz, and is used to excite the hazardous chemical to be detected to generate a pulsed Raman signal. It should be noted that in this embodiment, the phase modulation device 2 is an axonometric pyramid or a spatial light modulator. When the phase modulation device is an axonometric pyramid, it uses an axonometric pyramid with a base angle of 2° and a cone angle of 176°, which can convert the Gaussian beam generated by the nanosecond pulse laser into a diffraction-free Bessel beam. According to beam propagation theory, the cone angle of the axonometric pyramid is inversely proportional to the diffraction-free distance and directly proportional to the size of the central spot. The 176° cone angle can form an ideal diffraction-free region inside the sample when subsequently used in conjunction with a telescope system.
[0030] It should be noted that in this embodiment, the first lens assembly and the second lens assembly have the same structure, both including a pair of achromatic confocal lenses with a focal length ratio of 1:10. The focal length ratio of the lens assembly can be adjusted according to the estimated burial depth of the target hazardous chemical, so that the "diffraction-free distance" of the Bessel beam precisely covers the target depth range. The 1:10 ratio in this embodiment should not be used to limit the scope of protection of this invention.
[0031] It should be noted that, in this embodiment, the first lens assembly includes: The first lens 4 and the second lens 5, set along the optical path, can expand and collimate the original Bessel beam generated by the axial pyramid, compensate for the diffraction effect caused by the longer wavelength, extend the non-diffraction distance before entering the sample to be tested by about 10 mm, and control the lateral main lobe diameter to about 20 μm, thereby forming a spectral detection focal depth region with stable energy distribution along the propagation direction and consistent lateral size inside the hazardous chemical to be tested. The second lens assembly includes: The third lens 6 and the fourth lens 7, which are set along the optical path, are used to ensure that the light rays in the collection area and the light rays in the excitation area are highly coincident, so as to convert the Bessel beam into parallel light.
[0032] It should be noted that, in this embodiment, the Raman filter assembly includes a dichroic mirror 9 and a high-pass filter, which are used to filter out the elastically scattered background light from the reflected signal of the sample under test and collect the Raman signal.
[0033] It should be noted that, in this embodiment, the Raman spectrometer includes an incident needle 11, a fifth lens 12, a second reflecting mirror 13, a third reflecting mirror 14, a prism 15, a converging lens 16, and a detector 17 arranged sequentially along the optical path, wherein the incident needle 11 has a slit channel and is transmitted to the focusing lens 10 via an optical fiber.
[0034] It should be noted that, in this embodiment, the focusing lens 10 is an achromatic lens with a focal length of 75mm, used to converge parallel light into a single point and couple it from the optical fiber into the Raman spectrometer.
[0035] It should be noted that, in this embodiment, the slit channel diameter of the incident needle 11 is 25 μm, which matches the spot size generated by the focusing lens 10.
[0036] The detector 17 uses an enhanced charge-coupled device (ICCD) and works synchronously with the external trigger mode and gated delay unit to achieve nanosecond-level time-resolved Raman signal acquisition. It is used to transmit the Raman signal in the optical fiber and to separate the Raman signal by dispersion before it enters the detector.
[0037] This embodiment also provides a method for detecting hazardous chemicals, which includes the following: S1, based on the signal control component, set the laser repetition frequency of the nanosecond pulse laser and the detector, and set the trigger mode, gating delay time and opening time width of the detector; S2, acquire the pulsed laser beam emitted by the nanosecond pulsed laser; S3, the phase modulation device receives the pulsed laser beam and modulates it into a Bessel beam; after adjustment by the first reflecting mirror and the first lens assembly, a diffraction-free region is constructed above the sample to be tested and acts on the sample to be tested to generate a pulsed Raman signal beam, which serves as the trigger condition for the detector. S4, drive the electromechanical platform to move to control the offset distance between the second transmission component and the first transmission component, thereby controlling the offset distance between the incident laser and the Raman signal of the sample under test; S5, the pulsed Raman signal beam passes through the second lens assembly and the conical lens. Based on the conical lens, the pulsed Raman signal beam is transformed into a Bessel beam, which is then coupled and focused into the optical fiber by the Raman filter assembly and enters the detector of the Raman spectrometer. S6, the detector receives Raman photons from deep within the sample under test within a window of preset opening time width, achieving non-destructive testing and effectively suppressing long-lived fluorescence background signals.
[0038] To verify the effectiveness of the present invention, the following specific implementation examples are provided: Taking the detection of ammonium nitrate powder stored in a 3mm thick green glass bottle through a 0.05mm thick nylon bag as an example, the above-mentioned hazardous chemical detection method was used to detect it: First, turn on the nanosecond pulse laser 1 to emit a pulse laser with a wavelength of 785nm.
[0039] Then, through modulation by phase modulation device 2, the Gaussian beam of nanosecond pulse laser 1 is modulated into a Bessel beam. The modulated Bessel beam, after beam expansion and collimation adjustment by the first lens assembly, can form a diffraction-free region before entering the sample, with an excitation depth of approximately 10 mm and a depth distribution as shown in the figure. Figure 5 As shown; the probe optical route consists of the same lens assembly and axial pyramid, and its detection depth is similar to the excitation depth; the spatially shifted Raman signal distribution of the ammonium nitrate powder at a depth of approximately 3 mm is shown in the figure. Figure 6 As shown, the offset distance of the third lens 6 needs to be fixed at 10mm, and the electromechanical platform is driven by a stepper motor to complete the horizontal offset of the third lens 6 relative to the second lens 5.
[0040] Furthermore, the timing sequence of spectral signal excitation and collection in this embodiment is as follows: Figure 7 As shown.
[0041] The gating delay time is finely adjusted by a digital delay generator: the first output channel of the digital delay generator is connected to the external trigger input of the nanosecond pulse laser to control the laser emission timing; the second output channel is connected to the gating delay unit and then to the gating trigger input of the detector.
[0042] The total delay time ttotal is set to 3.2 ns. This delay time consists of the base delay t0 = 3 ns and the offset compensation delay. It consists of two parts: the lateral diffusion path caused by compensating for spatial offset; and the detector activation time width. The time window is set to 6.8 ns, during which the detector is only turned on, accurately receiving Raman photons from deep within the sample and effectively suppressing long-lived fluorescence background signals.
[0043] Preferably, for extremely weak signals, the number of signal photons can be increased by increasing the repetition rate, i.e., increasing the cumulative number of laser pulses.
[0044] Finally, the collected Raman signal is coupled and focused into the optical fiber by the second lens assembly, the axon pyramid, and the Raman filter assembly consisting of a dichroic mirror and a high-pass filter before entering the Raman spectrometer.
[0045] The effect diagram of the spectral acquisition method provided in this embodiment is shown below. Figure 8 As shown, the effectiveness of this application is compared with that of traditional confocal Raman acquisition methods. Traditional confocal Raman technology can only acquire a mixed signal of surface and fluorescence signals, making it difficult to detect the Raman signal of deep targets or making it easy for the signal to be masked by surface and fluorescence signals. However, by applying the method of this invention, the combination of Bessel's non-diffraction property and spatially shifted Raman can detect Raman signals at deeper depths of the target sample. Furthermore, the combination of time-gated Raman technology effectively suppresses the fluorescence signal, thus more effectively acquiring the required molecular information and achieving the standard of non-destructive testing.
[0046] The hazardous chemical detection system and method according to the present invention have the following advantages: Significantly improved detection depth: The non-diffraction characteristics of Bessel beams result in low attenuation and long focal depth in scattering media, which can effectively excite deep targets and solve the problem of insufficient penetration of traditional Gaussian beams.
[0047] Significantly improved signal-to-noise ratio: Picosecond-precision time gating fundamentally suppresses nanosecond-level fluorescence background, combined with spatial offset technology and spatial filtering via a confocal aperture. By adjusting the Bessel beam ratio and spatial offset distance, the system can flexibly adapt to the detection needs of hazardous chemicals within complex media.
[0048] Optionally, embodiments of this application also provide an electronic device, including a processor, a memory, and a program or instructions stored in the memory and executable on the processor. When the program or instructions are executed by the processor, they implement the various processes of the above-described embodiment of a hazardous chemical detection method and achieve the same technical effect. To avoid repetition, they will not be described again here.
[0049] This application also provides a readable storage medium storing a program or instructions. When the program or instructions are executed by a processor, they implement the various processes of the above-described embodiment of a hazardous chemical detection method and achieve the same technical effect. To avoid repetition, they will not be described again here.
[0050] The processor is the processor in the electronic device described in the above embodiments. The readable storage medium includes computer-readable storage media, such as computer read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk.
[0051] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention.
[0052] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.
[0053] Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The reference to "embodiment" herein means that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily indicate the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.
[0054] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
Claims
1. A hazardous chemical detection system, characterized in that, It includes a signal excitation module and a signal acquisition module, wherein: The signal excitation module includes a nanosecond pulse laser (1), a phase modulation device (2), a first reflector (3), and a first lens assembly arranged sequentially along the optical path. Based on the phase modulation device (2), the Gaussian beam generated by the nanosecond pulse laser (1) is converted into a non-diffraction Bessel beam. After being reflected by the first reflector (3), the beam enters the first lens assembly, forming a spectral detection depth region inside the sample to be tested, so as to obtain the excitation optical path of the sample to be tested. The signal acquisition module includes: The optical components include a second lens assembly that propagates along the optical path, a conical lens (8), a Raman filter assembly, a focusing lens (10), and a Raman spectrometer. The Raman spectrometer has a detector (17). Based on the second lens assembly and the conical lens (8), the non-diffraction Bessel beam is converted into parallel light. After being filtered and focused, the light enters the detector (17) to collect Raman signals, so as to obtain the collection optical path of the sample to be tested. The mechanical offset component includes a movable electromechanical platform mounted on one side of the signal excitation module. The optical component is mounted on the electromechanical platform. By controlling the electromechanical platform to move in a direction perpendicular to the non-diffraction Bessel beam, the offset distance between the signal collection optical path and the excitation optical path can be adjusted. The signal control component is connected to the nanosecond pulse laser (1) and the detector (17) so that the two are under a unified nanosecond timing reference, and the receiver delay and turn-on time width of the detector (17) are set to suppress the acquisition of fluorescence signal.
2. The hazardous chemical detection system according to claim 1, characterized in that, The signal control component includes: A clock reference unit, connected to the nanosecond pulse laser (1) and the detector (17), is used to provide a unified nanosecond timing reference for the nanosecond pulse laser (1) and the detector (17); The gated delay unit has its output channels connected to the gated trigger input terminals of the nanosecond pulse laser (1) and the detector (17) respectively, and is used to set the receiving delay of the detector (1); The gating exposure control unit is connected to the detector (1).
3. The hazardous chemical detection system according to claim 1, characterized in that, The phase modulation device (2) is an axial pyramid or a spatial light modulator. When the phase modulation device is an axial pyramid, it adopts an axial pyramid (2) with a base angle of 2° and a cone angle of 176°.
4. The hazardous chemical detection system according to claim 1, characterized in that, The first lens assembly and the second lens assembly have the same structure, both including a pair of achromatic confocal lenses with a focal length ratio of 1:
10.
5. The hazardous chemical detection system according to claim 4, characterized in that, The first lens assembly includes: A first lens (4) and a second lens (5) are arranged along the optical path direction; The second lens assembly includes: The third lens (6) and the fourth lens (7) are set along the optical path.
6. The hazardous chemical detection system according to claim 1, characterized in that, The Raman filter assembly includes a dichroic mirror (9) and a high-pass filter for filtering out elastically scattered background light from the reflected signal of the sample under test and collecting the Raman signal.
7. The hazardous chemical detection system according to claim 1, characterized in that, The Raman spectrometer includes an incident needle (11), a fifth lens (12), a second mirror (13), a third mirror (14), a prism (15), a converging lens (16), and a detector (17) arranged sequentially along the optical path. The incident needle (11) has a slit channel and is transmitted to the converging lens (10) via an optical fiber.
8. A method for detecting hazardous chemicals, characterized in that, The detection is performed using the hazardous chemical detection system as described in any one of claims 1 to 7, including the following: S1, based on the signal control component, set the laser repetition frequency of the nanosecond pulse laser and the detector, and set the trigger mode, gating delay time and opening time width of the detector; S2, acquire the pulsed laser beam emitted by the nanosecond pulsed laser; S3, the phase modulation device receives the pulsed laser beam and modulates it into a Bessel beam; after adjustment by the first reflecting mirror and the first lens assembly, a diffraction-free region is constructed above the sample to be tested and acts on the sample to be tested to generate a pulsed Raman signal beam, which serves as the trigger condition for the detector. S4, drive the electromechanical platform to move to control the offset distance between the second transmission component and the first transmission component, thereby controlling the offset distance between the incident laser and the Raman signal of the sample under test; S5, the pulsed Raman signal beam passes through the second lens assembly and the conical lens. Based on the conical lens, the pulsed Raman signal beam is transformed into a Bessel beam, which is then coupled and focused into the optical fiber by the Raman filter assembly and enters the detector of the Raman spectrometer. S6, the detector receives Raman photons from deep within the sample under test within a window of a preset on time width.
9. A computer device, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the hazardous chemical detection method as described in claim 8.
10. A computer storage medium, characterized in that, The computer storage medium stores instructions that, when executed on the computer, cause the computer to perform the hazardous chemical detection method as described in claim 8.