Laser-induced spectrum detection system

Abstract

The invention provides a laser-induced spectrum detection system, and relates to the technical field of laser-induced spectrums, and the system comprises a laser-induced light source, a space coupling structure, a zoom lens group and a transmit-receive lens group which are sequentially arranged on a main optical axis of the system; the induction laser sequentially passes through the space coupling structure, the zoom lens group and the transceiving lens group and is emitted to a tested sample; signal light returns from a tested sample, sequentially passes through the transceiving lens group, the zoom lens group and the space coupling structure and then is guided into the spectrum acquisition system, and the data processing and control system is in communication connection with the spectrum acquisition system; the space coupling structure is used for separating an emission path of the induction laser and an acquisition path of the signal light; the zoom lens group is used for synchronously adjusting the size of an induced laser spot and the size of a signal detection view field; the proportion of the size of the induction laser spot to the size of the signal detection view field is kept constant in the zooming and distance changing process. The entering proportion of stray light is reduced, and the signal-to-noise ratio is improved.

Description

Technical Field

[0001] This invention relates to the field of laser-induced spectroscopy technology, and in particular to a laser-induced spectroscopy detection system. Background Technology

[0002] Laser-induced spectral detection systems commonly face a problem in practical detection processes: the signal light generated by the laser is very weak and easily mixes with background ambient light, atmospheric interference light, and the strongly scattered light from the excitation laser. This multi-source mixed light significantly reduces the signal-to-noise ratio of the received signal, severely affecting the sensitivity of the detection equipment and making it difficult to accurately detect and analyze trace components in the sample.

[0003] To improve the signal-to-noise ratio, existing systems typically employ dichroic mirrors or filters to separate the signal light from the induced laser and various interfering lights. These optical elements are designed to selectively transmit or reflect light of specific wavelengths to filter out unwanted scattered laser light and background light, thereby improving signal purity.

[0004] However, due to the inherent physical characteristics of dichroic mirrors and filters, such as limited extinction ratio, spectral bandwidth, and transmittance steepness, it is difficult to achieve ideal spectral filtering effects. This means that some interfering light will still mix into the signal light path, and may also cause some loss of the target signal light, resulting in limited improvement in the signal-to-noise ratio. Summary of the Invention

[0005] This invention provides a laser-induced spectral detection system to address the shortcomings of existing technologies that struggle to achieve ideal spectral filtering effects, resulting in limited improvement in signal-to-noise ratio. This system reduces the proportion of stray light entering the system and improves the signal-to-noise ratio.

[0006] This invention provides a laser-induced spectral detection system, comprising: Laser-induced light source, used to emit induced laser light; A spatial coupling structure is used to separate the emission path of the induced laser from the acquisition path of the signal light; The zoom lens group is used to adjust the size of the induced laser spot on the surface of the sample under test, and simultaneously adjust the size of the signal detection field of view; wherein, the ratio of the size of the induced laser spot to the size of the signal detection field of view remains constant during the zooming and distance adjustment process; A transceiver assembly is used to emit the induced laser onto the surface of the sample under test and to receive the signal light generated by the sample under test. A spectral acquisition system is used to split and acquire data of the signal light received by the spatial coupling structure; A data processing and control system, which is communicatively connected to the spectral acquisition system, is used to analyze, process, and control the spectral data output by the spectral acquisition system; The laser-induced light source, the spatial coupling structure, the zoom lens group, and the transceiver group are arranged sequentially on the main optical axis of the system. The induced laser passes sequentially through the spatial coupling structure, the zoom lens group, and the transceiver group and is directed toward the sample under test. The signal light returns from the sample under test, passes sequentially through the transceiver group, the zoom lens group, and the spatial coupling structure, and is then introduced into the spectral acquisition system.

[0007] In some embodiments, the spatial coupling structure includes at least one mirror; wherein at least one of the mirrors has a small aperture; the aperture is used to allow the induced laser to pass through and reach the zoom lens group; the reflective surface of the at least one mirror is used to reflect the signal light and guide it to the spectral acquisition system.

[0008] In some embodiments, the aperture is provided with an optical device for shaping the divergence angle, diameter, and spatial distribution of the induced laser, or with an optical device for collimating the induced laser.

[0009] In some embodiments, the system further includes: a coupling mirror assembly; The coupling mirror assembly is positioned on the main optical axis and located before or within the spatial coupling structure, for focusing and shaping the induced laser emitted by the laser-induced light source; or, The coupling mirror group is located on the optical path after the signal light is separated by the spatial coupling structure, and is used to focus the signal light into the spectral acquisition system.

[0010] In some embodiments, the spatial coupling structure includes a multi-core fiber bundle; the multi-core fiber bundle includes an emitting fiber connected to the laser-induced light source for emitting the induced laser, and a receiving fiber connected to the spectral acquisition system for receiving the signal light.

[0011] In some embodiments, the spacing between the fiber core of the transmitting fiber and the fiber core of the receiving fiber is within 0.1 mm to 5 mm.

[0012] In some embodiments, the system further includes a coupling mirror group, which is used to reflect the induced laser emitted by the transmitting optical fiber to the zoom lens group and simultaneously reflect the signal light to the receiving optical fiber.

[0013] In some embodiments, the zoom lens group and the transceiver lens group include one or more of lenses, mirrors, or diffractive optical devices.

[0014] In some embodiments, the system further includes an aperture stop and a field stop; the aperture stop is disposed in front of the zoom lens group, and the field stop is disposed behind the transceiver lens group.

[0015] The laser-induced spectral detection system provided by this invention constructs the emission path of the induced laser and the acquisition path of the signal light through a laser-induced light source, a spatial coupling structure, a zoom lens group, a transceiver lens group, a spectral acquisition system, and a data processing and control system. The spatial coupling structure separates the emission path of the induced laser and the acquisition path of the signal light. The zoom lens group synchronously adjusts the size of the induced laser spot and the size of the signal detection field of view, so that the ratio of the size of the induced laser spot to the size of the signal detection field of view remains constant during zooming and distance adjustment, thereby reducing the proportion of stray light entering and improving the signal-to-noise ratio. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a typical laser-induced spectral detection scheme based on a dichroic mirror.

[0018] Figure 2 This is a schematic diagram of a typical laser-induced spectral detection scheme based on filters.

[0019] Figure 3 This is one of the structural schematic diagrams of the laser-induced spectral detection system provided in the embodiments of the present invention.

[0020] Figure 4 This is the second schematic diagram of the structure of the laser-induced spectral detection system provided in the embodiment of the present invention.

[0021] Figure 5 This is the third schematic diagram of the structure of the laser-induced spectral detection system provided in the embodiments of the present invention.

[0022] Figure 6 This is the fourth schematic diagram of the laser-induced spectral detection system provided in the embodiments of the present invention.

[0023] Figure 7 This is the fifth schematic diagram of the structure of the laser-induced spectral detection system provided in the embodiments of the present invention.

[0024] Figure label: 1: Induced laser spot; 2: Signal detection field of view; 3: Transceiver lens group; 4: Zoom lens group; 5: Coupler lens group; 6: Spatial coupling structure; 61: First reflecting mirror; 62: Second reflecting mirror; 7: Laser-induced light source; 71: First laser-induced light source; 72: Second laser-induced light source; 8: Spectral acquisition system; 9: Data processing and control system; 10: Aperture stop; 11: Field stop. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0026] Fluorescence generated by laser excitation of a substance is called laser-induced fluorescence (LIF). When a substance is irradiated with light of a specific wavelength, the irradiated substance has a certain probability of absorbing photons, causing the particles to transition to an excited state and then radiatively transition to a lower energy level, emitting photons. The energy of the photons absorbed and emitted by the substance is related to the energy difference between the energy levels of the fluorescent particles, therefore the wavelength range of photons absorbed and emitted by each substance is relatively fixed. Typically, the wavelength of the fluorescent photons is longer than the wavelength of the incident photons.

[0027] Raman spectroscopy is produced by the Raman scattering effect. The Raman scattering effect refers to the phenomenon where, when light shines on a surface, molecules absorb some energy, vibrate in different ways and to varying degrees, and then scatter light of different frequencies. Raman spectroscopy reflects the correlation between the vibrational energy levels (lattice vibrational energy levels) and rotational energy levels of molecules, thus allowing the identification of information about the molecular structure of matter. Laser-induced Raman spectroscopy (LIRS) is an analytical method based on the Raman scattering effect, analyzing the scattered spectra at frequencies different from the incident light to obtain information about the characteristics of molecules. LIRS can be used to analyze and identify the components of both organic and inorganic substances, and is a method for studying the molecular structure of matter.

[0028] Laser-induced breakdown spectroscopy (LIBS), also known as laser-induced plasma spectroscopy (LIPS), is an analytical technique based on the plasma emission spectrum generated by the interaction between a laser and a material. This method involves ablating a sample with a laser and then detecting the spectrum of plasma emission to achieve quantitative and qualitative analysis of the material composition. It can also be used for identification and classification.

[0029] The aforementioned laser-induced spectroscopy techniques typically employ gratings for spectral dispersion, followed by intensity detection using devices such as Complementary Metal-Oxide-Semiconductor (CMOS) or Charge-Coupled Device (CCD) to obtain the correlation between spectral intensity and wavelength. For example, common laser-induced spectral signal detection systems utilize Czerny-Turner spectrometers or echelle grating spectrometers for spectral detection. However, a common problem in practical detection is that the laser-induced signal light is extremely weak and readily mixes with ambient light, atmospheric interference, and the intensely scattered light from the excitation laser. This multi-source mixing significantly reduces the signal-to-noise ratio of the received signal, severely impacting the sensitivity of the detection equipment and hindering accurate detection and analysis of trace components in the sample. Especially when adjusting the induced laser brightness, varying the laser induction range, or changing the induction distance, the complex nature of the interference makes it difficult for existing artificial intelligence algorithms to effectively filter out noise and background interference.

[0030] Figure 1 This is a schematic diagram illustrating the principle of a typical laser-induced spectral detection scheme based on a dichroic mirror, such as... Figure 1 As shown, the induced laser emitted by the induced laser emission source illuminates a dichroic mirror. After reflection by the dichroic mirror, the induced laser is directed towards the target, inducing the target to generate signal light. The signal light and interference light (atmospheric stray light and induced laser echo) return together and illuminate the dichroic mirror. The dichroic mirror transmits the signal light while reflecting the interference light, and the spectrometer receives the separated signal light.

[0031] Figure 2 This is a schematic diagram of a typical laser-induced spectral detection scheme based on filters, such as... Figure 2As shown, the induced laser emitted by the induced laser emission source passes through a zoom optical lens group. The zoom optical lens group adjusts the zoom of the induced laser beam. After leaving the zoom optical lens group, the induced laser beam is directed towards the target, inducing the target to generate signal light. The signal light returns along with interference light (atmospheric stray light and induced laser echo), is received and collected by an optical receiving lens group, and then enters a filter. The filter removes the interference light, and a spectrometer receives the filtered signal light.

[0032] Although dichroic mirrors or filters can separate signal light from interference light, the inherent physical characteristics of these mirrors and filters, such as limited extinction ratio, spectral bandwidth, and transmittance steepness, make it difficult to achieve ideal beam splitting and filtering effects. This means that some interference light will still mix into the signal light path, and may also cause some loss of the target signal light, resulting in limited improvement in the signal-to-noise ratio.

[0033] For example, a typical dichroic mirror or filter has a high reflectivity (i.e., a transmittance ratio of less than 1 / 10) with an optical density (OD) value greater than 6. 6 To achieve high transmittance of over 90%, a spectral width of 10-30 nm is required, which may result in a spectral width of 50-500 cm. -1 Raman spectral information is lost over a wide range; at long distances, the peak intensity of laser emission can reach gigawatts (GW), which means that even after attenuation to an OD value of 6, the laser signal intensity is still only 10 times that of the original signal. 3 ~10 4 Extraction of severely interfering signals.

[0034] Figure 3 This is one of the structural schematic diagrams of the laser-induced spectral detection system provided in the embodiments of the present invention, such as... Figure 3 As shown, the laser-induced spectral detection system provided by the present invention includes: a transceiver group 3, a zoom lens group 4, a spatial coupling structure 6, a laser-induced light source 7, a spectral acquisition system 8, and a data processing and control system 9.

[0035] The laser-induced light source 7 is used to emit induced laser light; the spatial coupling structure 6 is used to separate the emission path of the induced laser light from the acquisition path of the signal light; the zoom lens group 4 is used to adjust the size of the induced laser spot 1 on the surface of the sample under test, and simultaneously adjust the size of the signal detection field of view 2; wherein, the ratio of the size of the induced laser spot 1 to the size of the signal detection field of view 2 remains constant during the zoom and distance adjustment process; the transceiver lens group 3 is used to emit the induced laser light to the surface of the sample under test and receive the signal light generated by the sample under test; the spectral acquisition system 8 is used to split the signal light received by the spatial coupling structure 6 and acquire data; the data processing and control system 9 is communicatively connected to the spectral acquisition system 8, and the data processing and control system 9 is used to analyze, process and control the spectral data output by the spectral acquisition system 8.

[0036] The laser-induced light source 7, the spatial coupling structure 6, the zoom lens group 4, and the transceiver group 3 are arranged sequentially on the main optical axis of the system; the induced laser passes through the spatial coupling structure 6, the zoom lens group 4, and the transceiver group 3 in sequence and is directed toward the sample under test; the signal light returns from the sample under test, passes through the transceiver group 3, the zoom lens group 4, and the spatial coupling structure 6 in sequence, and is then introduced into the spectral acquisition system 8.

[0037] Specifically, the laser-induced light source 7 is responsible for emitting high-energy, highly stable, or specific wavelength induced lasers. Figure 3 The pink arrows represent the optical path of the induced laser, while the red arrows represent the optical path of the signal light. These laser pulses or continuous beams are precisely guided to the surface of the sample being measured. Through interaction with the sample material, specific physicochemical processes are excited, such as the generation of plasma, fluorescence, or Raman scattering, thereby initiating the entire spectroscopic detection process.

[0038] The spatial coupling structure 6 separates the high-intensity induced laser emission path from the acquisition path of the weak signal light returning from the sample under test, and is one of the key components for achieving a high signal-to-noise ratio in the system. This optical isolation mechanism can effectively prevent the strong excitation laser from entering the sensitive signal acquisition system, thereby protecting the spectral acquisition system 8 from damage or saturation caused by strong light, eliminating the interference of strong laser scattering on the weak signal at the source, and greatly improving the system's signal-to-noise ratio and detection limit.

[0039] The zoom lens group 4 can dynamically adjust the size of the induced laser spot 1 and simultaneously adjust the size of the signal detection field of view 2, making it a core component for maintaining high performance at different working distances. Throughout the zoom and distance adjustment process (i.e., changing the working distance), the ratio of the size of the induced laser spot 1 to the size of the signal detection field of view 2 remains constant. This allows the system to limit the spectral acquisition system 8 to focus only on the core signal-generating region, meaning the area of ​​non-signal-generating regions covered by the signal detection field of view 2 is minimized. Consequently, the amount of stray light and background noise entering the spectral acquisition system 8 from these non-signal-generating regions is also minimized, thereby improving the signal-to-noise ratio.

[0040] The transceiver group 3 is responsible for bidirectional optical transmission. The transceiver group 3 accurately emits and focuses the shaped and focused induced laser onto the surface of the sample under test, ensuring that the laser energy density reaches the level required for excitation; at the same time, the transceiver group 3 also efficiently collects the weak signal light generated and scattered back from the surface of the sample under test, collimates or focuses it, and guides it to the subsequent spectral acquisition system 8.

[0041] The spectral acquisition system 8 is responsible for converting the signal light emanating from the spatial coupling structure 6 into analyzable digital spectral data. The spectral acquisition system 8 first disperses the signal light, then uses a highly sensitive detector to convert the light intensity information at different wavelengths into electrical signals, and finally acquires the data to form the raw spectrum.

[0042] The data processing and control system 9 is communicatively connected to the spectral acquisition system 8, performing spectral data analysis, processing, and comprehensive control of the entire system. The data processing and control system 9 performs qualitative identification and quantitative analysis on the acquired raw spectral data; it applies various algorithms for preprocessing, including noise reduction, background subtraction, baseline correction, and wavelength calibration, to improve data accuracy and analytical reliability; it provides a user interface and logic control to enable the setting, timing synchronization, and operation of all hardware components, including the laser-induced light source 7 and the spectral acquisition system 8, ensuring the system operates in optimal condition. The data processing and control system 9 is also communicatively connected to the laser-induced light source 7, controlling the power, pulse repetition frequency, and operating mode of the induced laser emitted by the laser-induced light source 7.

[0043] The laser-induced light source 7 emits an induced laser beam, which first passes through the spatial coupling structure 6. The spatial coupling structure 6 acts as a transparent channel, allowing the high-intensity induced laser beam to pass through without attenuation, thereby maximizing the retention of laser energy. Subsequently, the induced laser beam enters the zoom lens group 4, which precisely shapes and focuses the laser beam, dynamically adjusting the size of the induced laser spot 1 and simultaneously adjusting the size of the signal detection field of view 2 to adapt to different analytical needs. Finally, the shaped and focused induced laser beam reaches the transceiver group 3, which precisely guides and ultimately focuses the laser beam onto the surface of the sample being tested, ensuring that the optimal laser energy density is achieved in that region, thereby achieving effective excitation.

[0044] When the induced laser interacts with the sample to be tested (such as by exciting plasma, fluorescence, or Raman scattering) to generate signal light, these weak light signals carrying the chemical information of the sample to be tested will return along the opposite path to the induced laser and be accurately introduced into the spectral acquisition system 8, and analyzed and controlled by the data processing and control system 9.

[0045] The signal light is first efficiently collected by the transceiver group 3, then passes through the zoom lens group 4. After entering the spatial coupling structure 6, the signal light separates the acquisition path from the emission path of the induced laser, deflecting the signal light off the principal optical axis to prevent the induced laser from interfering with the subsequent detection system. The separated signal light is then introduced into the spectral acquisition system 8, where it is split and converted into an electrical signal to generate raw spectral data. The spectral acquisition system 8 transmits the generated spectral data to the data processing and control system 9 in real time. The data processing and control system 9 analyzes, corrects, and processes the spectral data (such as denoising and quantitative analysis), while simultaneously controlling the parameters and timing of the entire detection system.

[0046] The laser-induced spectral detection system provided in this embodiment of the invention constructs the emission path of the induced laser and the acquisition path of the signal light through a laser-induced light source 7, a spatial coupling structure 6, a zoom lens group 4, a transceiver lens group 3, a spectral acquisition system 8, and a data processing and control system 9. The spatial coupling structure 6 separates the emission path of the induced laser and the acquisition path of the signal light. The zoom lens group 4 synchronously adjusts the size of the induced laser spot 1 and the size of the signal detection field of view 2, so that the ratio of the size of the induced laser spot 1 to the size of the signal detection field of view 2 remains constant during zooming and distance adjustment, thereby reducing the proportion of stray light entering and improving the signal-to-noise ratio.

[0047] In some embodiments, the laser-induced light source 7 can be a semiconductor laser, a solid-state laser, or a gas laser, such as an Nd:YAG laser, or a semiconductor laser with fiber-coupled output, or a carbon dioxide laser; the laser-induced light source 7 can be a laser capable of pulsed output or a continuously output laser; the laser-induced light source 7 can also be a single laser capable of outputting 2 to 100 pulses with adjustable intervals through power supply or optical modulation methods to continuously achieve excitation; the laser-induced light source 7 can be composed of 2 to 5 lasers combined together, controlled by a unified timing output device, to achieve excitation according to a set time interval; the laser-induced light source 7 can output multiple wavelengths of laser light simultaneously or from different light sources as needed to improve the excitation effect of the plasma.

[0048] In some embodiments, the transceiver assembly 3 includes one or more of a lens, a mirror, or a diffractive optics device.

[0049] Specifically, the transceiver group 3 can consist of 1 to 20 lenses, 1 to 5 mirrors, 1 to 2 diffractive optical elements, or other combinations of lenses, mirrors, and diffractive optical elements. Diffractive optical elements are optical devices that shape, spatially distribute, and spectrally control emitted laser light based on the diffraction effect, such as Fresnel mirrors.

[0050] The scheme for constructing the transceiver group 3 based on the lens group is as follows: A lens group consisting of 1 to 20 lenses can precisely control the divergence angle and spot diameter of the laser, projecting a spot of the required size (including converging to an extremely small point) at the desired distance. A lens group consisting of one or more lenses can efficiently collect signal light and collimate it into a beam with the required divergence angle and diameter.

[0051] The scheme for constructing transceiver group 3 based on the mirror group is as follows: By using a mirror assembly consisting of 1 to 5 mirrors, the emission direction, divergence angle, and spot diameter of the laser can be flexibly controlled to form a spot of the desired size (including convergence to an extremely small point) at the required distance. Utilizing the same optical path design, efficient collection of the signal light is achieved, and it is collimated into a beam with the required divergence angle and diameter.

[0052] The following is a scheme for constructing transceiver group 3 by combining diffractive optical devices: To achieve long-distance laser focusing and emission, and the acquisition of excitation signals, diffractive optics are positioned behind mirrors or lens arrays to precisely shape the laser beam. For example, the emitted laser beam is shaped into approximately parallel light by lenses and mirrors, and then further refined into a slender linear spot (0.1–5 mm wide and 1–1000 mm long) by one or more Fresnel mirrors, enabling scanning and signal acquisition over a large area. Similarly, diffractive optics can be used to form any number of array spots ranging from 2×2 to 100×100 to achieve simultaneous multi-point laser induction and signal light acquisition.

[0053] In some embodiments, the zoom lens group 4 includes one or more of a lens, a mirror, or a diffractive optics.

[0054] Specifically, the zoom lens group 4 can be composed of 1 to 20 lenses or mirrors, or it can be composed of other numbers of lenses, mirrors and diffractive optical devices, or it can be a combination of the above methods.

[0055] In some embodiments, the spectral acquisition system 8 may include a spectrometer and a detector; wherein the spectrometer separates the received plasma light into monochromatic lights of different wavelengths and orders, and the detector is used to image the monochromatic light obtained by the spectrometer after being detected and digitized by a charge-coupled device. The detector may be an imaging device such as a CCD or CMOS, or one or more photosensitive devices arranged in a linear array, such as one or more photodiodes or photomultiplier tubes. The spectral acquisition system 8 may also be an integrated spectral detection device, including but not limited to a Czerny-Turner spectrometer, an echelle grating spectrometer, a Fourier spectrometer, as well as a photometer, a wavelength meter, etc.

[0056] In some embodiments, the data processing and control system 9 serves as the core hub of the system, integrating two major functions: processing and analyzing spectral data and controlling and managing system operation.

[0057] The data processing and control system 9 supports manual or automatic modes for acquiring and initially processing spectral data, ensuring flexibility and efficiency in data input. To ensure the accuracy and reliability of the analysis, the data processing and control system 9 provides comprehensive spectral data correction functions to optimize data quality and serve subsequent quantitative and qualitative analyses. These functions include, but are not limited to, wavelength alignment correction, noise reduction, background subtraction, and baseline correction. With its powerful processing capabilities, the data processing and control system 9 can quickly perform the required qualitative and quantitative analyses and accurately identify sample categories in real time based on changes in the intensity of the spectral signal.

[0058] For laser-induced breakdown spectroscopy, the data processing and control system 9 can perform quantitative analysis of elemental, molecular, and ionic composition from the plasma spectrum generated by laser ablation. For example, it can analyze the content of any element in an alloy; analyze the silicate content in ores; and analyze the Fe content on corroded metal surfaces. 3+ and Fe 2+ And Fe atomic content ratio analysis. The data processing and control system 9 can perform cluster analysis on samples based on the combined characteristics of multiple elements and multiple spectral lines, including but not limited to the origin and quality classification of samples (taking coal as an example, it can perform category analysis, such as distinguishing between lignite and anthracite; and distinguishing between different origins and mining areas).

[0059] For laser-induced Raman spectroscopy, the data processing and control system 9 can achieve qualitative identification and quantitative analysis of molecular components, ionic components, and chemical bonds based on the peak position, peak shift, and peak intensity of the Raman spectrum.

[0060] For laser-induced fluorescence spectroscopy, the data processing and control system 9 can identify physical properties and analyze biological properties by measuring the center wavelength and peak intensity of the fluorescence spectrum emitted after the excitation light is absorbed by the sample. The identification of physical properties includes the identification of molecules, ions, and chemical bonds. Taking biology as an example, the growth status of plants can be analyzed by the spectral characteristics of chlorophyll.

[0061] The data processing and control system 9 provides an intuitive interface for setting and managing various operating parameters of the equipment, coordinating the timing relationships between different components (such as lasers, detectors, etc.), and displaying key parameters and system status in real time to ensure stable and efficient operation of the equipment.

[0062] The data processing and control system 9 can be flexibly deployed on a variety of hardware platforms to adapt to different application environments and operational needs, including but not limited to: personal computers, dedicated displays, tablet computers and industrial control systems.

[0063] In some embodiments, the laser-induced spectral detection system further includes an aperture stop 10 and a field stop 11; the aperture stop 10 is disposed in front of the zoom lens group 4, and the field stop 11 is disposed behind the transceiver lens group 3.

[0064] Specifically, the aperture stop 10 is positioned in front of the zoom lens group 4. This means that in the induced laser emission path, the aperture stop 10 is located after the spatial coupling structure 6 and before the zoom lens group 4, while in the signal light acquisition path, the aperture stop 10 is located after the transceiver group 3 and before the zoom lens group 4.

[0065] An aperture stop limits the effective diameter of the light beam passing through the optical system, i.e., the numerical aperture of the control system. Aperture stop 10 determines how much light can enter or leave the zoom lens group 4. By adjusting the size of aperture stop 10, the distribution and intensity of laser energy reaching the surface of the sample under test, as well as the brightness of the signal light collected from the sample under test, can be controlled.

[0066] For signal acquisition, an appropriately sized aperture stop helps optimize the system's resolution and depth of field. A smaller aperture can increase the depth of field, allowing signals on different focal planes to be clearly imaged and potentially reducing optical aberrations; while a larger aperture can collect more signal light, increasing signal intensity. Furthermore, it helps block off-axis stray light from entering the subsequent optical path, thereby reducing background noise that this stray light might introduce.

[0067] The field stop 11 is positioned behind the transceiver group 3, which typically means that the field stop 11 is located between the transceiver group 3 and the sample under test. The field stop precisely defines the sample area that the optical system can "see," i.e., the physical boundary of the signal detection field of view 2.

[0068] The field stop 11 works in close coordination with the synchronous adjustment mechanism of the zoom lens group 4. The zoom lens group 4 ensures that the size of the induced laser spot 1 and the size of the signal detection field of view 2 remain in a constant ratio during zooming and distance adjustment. The presence of the field stop 11 further enhances and refines this matching at the physical level. Through physical blocking, it strictly limits the spectral acquisition system 8 to focusing only on the laser-excited measurement area. This means that the field stop 11 minimizes the amount of light entering the spectral acquisition system 8 from non-signal generation areas. Any scattered light, ambient light, or background radiation (stray light and background noise) from outside the laser excitation range of the sample surface will be effectively blocked by the field stop 11.

[0069] The laser-induced spectral detection system provided in this embodiment of the invention uses an aperture stop 10 to control the system's brightness and resolution, and a field stop 11 to precisely define the signal acquisition area. Together with the zoom lens group 4, they greatly suppress background noise from the source, significantly improving the system's signal-to-noise ratio and measurement accuracy.

[0070] In some embodiments, the spatial coupling structure 6 includes at least one mirror; wherein the at least one mirror has a small hole; the small hole is used to allow the induced laser to pass through and reach the zoom lens group 4; the reflective surface of the at least one mirror is used to reflect the signal light and guide it to the spectral acquisition system 8.

[0071] Specifically, the spatial coupling structure 6 includes at least one reflector. The reflector can be planar, concave, or convex. Its function is to reflect the laser light. It can be integrally machined from materials such as metal, glass, or plastic, with a surface coated with a high-reflectivity film of aluminum, silver, gold, or a dielectric material. Alternatively, a mirror can be bonded to the surface of the structure. The reflector can be spherical or aspherical, or have a special surface microstructure or coating to modulate the emitted laser light. The reflector can consist of 1 to 10 optical components, including reflectors, scattering surfaces, or diffractive optical elements, as well as combinations of reflectors, scattering surfaces, or diffractive optical elements with lenses, prisms, or other optical components.

[0072] At least one reflector includes at least one reflector with a pinhole, which can be a rectangular aperture. The pinhole acts as a "channel" for the induced laser, allowing the laser beam to pass through with almost no attenuation, continuing its journey along the principal optical axis and heading towards the zoom lens group 4. This design maximizes the energy (power) and beam quality of the laser, ensuring that the induced laser reaches the surface of the sample under test with the expected energy density. Simultaneously, since the powerful laser beam does not directly impact the reflective surface of the reflector, this effectively avoids potential damage, thermal deformation, or additional stray scattering to the reflector caused by high-power laser irradiation, thus ensuring the stability of the entire optical system and a high signal-to-noise ratio of the spectral signal.

[0073] The signal light returning from the surface of the sample under test, after passing through the transceiver group 3 and the zoom lens group 4, will return to the spatial coupling structure 6. At this time, the signal light usually returns in the form of a diverging beam. The spot size of the signal light is usually much larger than the size of the aperture, so it is usually possible to achieve that more than 90% of the signal light is reflected by the reflective surface around the aperture of the mirror and deflected according to the preset optical path, and then received by the spectral acquisition system 8.

[0074] The laser-induced spectral detection system provided in this embodiment of the invention eliminates the possibility of strong induced laser directly entering the sensitive spectral acquisition system 8 by passing the induced laser through a small hole and reflecting and deflecting the signal light through a reflector.

[0075] In some embodiments, an optical device for shaping the divergence angle, diameter, and spatial distribution of the induced laser is provided inside the aperture; or, an optical device for collimating the induced laser is provided; or an optical device for merging the induced laser beams is provided.

[0076] Specifically, the small hole in the spatial coupling structure 6 is not merely a physical channel through which the induced laser penetrates, but is designed as a complex component integrating multiple optical devices. Within this small hole, the aforementioned transmission mirror, reflection mirror, and various optical devices based on the principles of diffraction, interference, and polarization can be configured to preprocess and optimize the induced laser, ensuring that the laser reaches the subsequent optical path and the sample under test in the best possible condition.

[0077] The aperture contains optical devices for collimating the induced laser, such as collimating lenses and achromatic doublet lenses, which convert the diverging laser beam into a nearly parallel beam. This ensures that the induced laser has good collimation before entering the zoom lens group 4 and the transceiver lens group 3, thereby reducing optical system aberrations, minimizing energy loss, preventing beam quality degradation, ensuring the effectiveness of subsequent beam shaping, focusing, and transmission, and making it easier for subsequent optical components to achieve precise focal spot control.

[0078] Alternatively, the aperture may contain optical devices, such as a lens group of one to ten elements, for shaping the divergence angle, diameter, and spatial distribution of the induced laser. Precise adjustment of the divergence angle adjusts the beam's divergence or convergence characteristics to suit specific working distances or focusing requirements. Precise control of the induced laser beam diameter through shaping is crucial for achieving a specific spot size. Spatial distribution shaping transforms a non-uniform laser beam into a uniform spot with a flat top or a specific shape (such as linear or rectangular).

[0079] Alternatively, the aperture can contain optical devices for merging the induced laser beams, such as prisms or polarizers. If the laser-induced source 7 is actually composed of multiple lasers, optical devices can be placed within the aperture to merge these independent beams into a single coaxial beam, allowing it to pass through the subsequent zoom lens group 4 and transceiver lens group 3. This merging capability enables the system to easily utilize multi-wavelength lasers for excitation, or combine different types of lasers to achieve more flexible excitation strategies, greatly enhancing the system's versatility and adaptability without requiring independent optical paths for each laser beam.

[0080] When the laser-induced light source 7 emits induced laser light through space and the spectral acquisition system 8 receives the signal light through an optical fiber, the induced laser beam enters the spatial coupling structure 6 in the form of a spatial beam. A pinhole is used to allow the induced laser to pass directly through. Inside the pinhole, optical devices are installed to shape the divergence angle, diameter, and spatial distribution of the induced laser, or to collimate the induced laser. The signal light returning from the sample under test is deflected by a reflector. Behind the reflector, an optical fiber fixing structure is provided, and one or more up to ten lens groups are arranged at the end face of the optical fiber to efficiently converge the reflected signal light and couple it into the receiving optical fiber.

[0081] In a system where the laser-induced light source 7 emits an induced laser through an optical fiber, and the spectral acquisition system 8 receives the signal light through space, the induced laser is introduced through the end face of the optical fiber, which can directly penetrate or approach a small hole on the reflector. Within the small hole, optical devices are installed for collimating, controlling the divergence angle, diameter, and spatial distribution of the diverging laser beam emitted from the optical fiber, or for beam combining, such as prisms and polarizers. The signal light returning from the sample is deflected by the reflector. The deflected signal light, as a spatial beam, is directly introduced into the spatial entrance of the spectral acquisition system 8.

[0082] In a system where the laser-induced light source 7 emits induced laser light through an optical fiber, and the spectral acquisition system 8 receives signal light through an optical fiber, the induced laser light is introduced through the end face of the first optical fiber, which can directly penetrate or approach a small hole on the reflector. Within the small hole, optical devices are installed for collimating, controlling the divergence angle, diameter, and spatial distribution of the diverging laser beam emitted from the optical fiber, or for beam combining, such as prisms and polarizers. The signal light returning from the sample is deflected by the reflector. Behind the reflector, an optical fiber fixing structure is provided for fixing the second receiving optical fiber, and a lens group of one to ten elements is configured to efficiently converge the reflected signal light and couple it into the receiving optical fiber.

[0083] When the laser-induced light source 7 emits induced laser light in space and the spectral acquisition system 8 receives the signal light in space, the induced laser beam enters the spatial coupling structure 6 as a spatial beam and directly passes through a small hole on the reflector. Optical devices are installed inside the small hole to shape the divergence angle, diameter, and spatial distribution of the induced laser, or to collimate the induced laser. The signal light returning from the sample is deflected by the reflector. The deflected signal light, as a spatial beam, is directly introduced into the spatial entrance of the spectral acquisition system 8.

[0084] The laser-induced spectral detection system provided in this embodiment of the invention extends the function of the spatial coupling structure 6 from simple optical path separation to fine preprocessing of the induced laser by integrating optical devices within the aperture. The beam quality and shape of the induced laser are optimized before it enters the main optical path, ensuring efficient and precise sample excitation. This pre-positioned laser beam control component significantly improves the performance, flexibility, and reliability of the entire laser-induced spectral detection system.

[0085] In some embodiments, the laser-induced spectral detection system further includes: a coupling mirror group 5; The coupling mirror group 5 is positioned on the main optical axis and located before or within the spatial coupling structure 6, used to focus and shape the induced laser emitted from the laser-induced light source 7; or, The coupling mirror group 5 is located on the optical path after the signal light is separated by the spatial coupling structure 6, and is used to focus the signal light into the spectral acquisition system 8.

[0086] Specifically, the coupling mirror group 5 can consist of 1 to 5 lenses or mirrors, or a combination of lenses and mirrors.

[0087] When the coupling mirror group 5 is positioned on the main optical axis and is located before or in the spatial coupling structure 6, the coupling mirror group 5 focuses and shapes the induced laser emitted by the laser-induced light source 7, while precisely controlling aberrations to avoid the influence of errors caused by subsequent optical paths.

[0088] It should be noted that when the coupling mirror group 5 is located within the spatial coupling structure 6, the coupling mirror group 5 can be located within a small hole on the reflector.

[0089] When the coupling mirror group 5 is placed on the optical path after the signal light is separated by the spatial coupling structure 6, the signal light deflected from the spatial coupling structure 6 is usually divergent. The function of the coupling mirror group 5 is to efficiently converge the signal light to the entrance of the spectrum acquisition system 8.

[0090] The laser-induced spectral detection system provided in this embodiment of the invention uses a coupling mirror group 5, which, through precise beam control and efficient optical coupling, can compensate for and eliminate performance differences between different optical components, ensuring that the induced laser can excite the sample in the best state, or ensuring that the weak signal light energy returned from the sample under test enters the spectral acquisition system 8 with maximum efficiency and highest quality.

[0091] In some embodiments, the spatial coupling structure 6 includes a multi-core fiber bundle; the multi-core fiber bundle includes an emitting fiber connected to the laser-induced light source 7 for emitting induced laser, and a receiving fiber connected to the spectral acquisition system 8 for receiving signal light.

[0092] Specifically, the spatial coupling structure 6 includes a multi-core fiber bundle, which is an optical fiber assembly formed by binding multiple independent optical fibers together through fusion, bonding, or mechanical fixation. The multi-core fiber bundle includes a transmitting fiber connected to the laser-induced light source 7 and a receiving fiber connected to the spectral acquisition system 8. The transmitting fiber is used to emit induced laser light, and the receiving fiber is used to receive signal light.

[0093] The induced laser emitted by the laser-induced light source 7 is precisely guided to the near end of the transmitting fiber through an optical fiber coupler. The induced laser propagates along the transmitting fiber and exits from the far end, striking the sample under test to achieve excitation. After the induced laser excites signal light on the sample surface, this signal light is efficiently captured by the receiving fiber adjacent to the far end of the transmitting fiber. The signal light is then transmitted through the receiving fiber, exiting from the near end and being introduced into the spectral acquisition system 8.

[0094] The laser-induced spectral detection system provided in this embodiment of the invention has an independent transmitting fiber and a receiving fiber throughout the transmission path, which ensures that the induced laser is mainly emitted from the transmitting fiber, while the signal light is mainly captured by the receiving fiber, thus avoiding the direct excitation laser from entering the receiving fiber.

[0095] In some embodiments, the spacing between the fiber core of the transmitting fiber and the fiber core of the receiving fiber is within 0.1 mm to 5 mm.

[0096] Specifically, the spacing between the fiber cores of the transmitting and receiving fibers is limited to a range of 0.1 mm to 5 mm. The lower limit of 0.1 mm allows the receiving fiber to be positioned as close as possible to the laser excitation point. Signal light emitted from the surface of the sample under test is typically isotropic or diverges over a wide angle. The closer the receiving fiber is to the excitation point, the larger the solid angle it can capture, resulting in higher signal light intensity, which is crucial for detecting weak signals. The upper limit of 5 mm ensures that the receiving fiber can cover a sufficiently large signal collection area, especially when the signal distribution on the sample surface is uneven or the excitation point has slight drift. Furthermore, during remote detection, minor deviations from the optical axis due to the fiber core spacing within the 0.1 mm to 5 mm range can be approximately ignored.

[0097] The transmitting or receiving optical fiber is placed on the optical axis to achieve ideal symmetrical illumination; or the transmitting and receiving optical fibers are arranged symmetrically to reduce overall deviation.

[0098] The laser-induced spectral detection system provided in this invention can effectively solve the off-axis deviation problem in long-distance laser-induced spectral detection by precisely controlling the spacing between the fiber cores of the transmitting fiber and the receiving fiber, thus ensuring stable excitation of the induced laser and efficient and accurate collection of the signal light.

[0099] In some embodiments, the laser-induced spectral detection system further includes a coupling mirror group 5, which is used to reflect the induced laser emitted by the transmitting fiber to the zoom lens group 4, and simultaneously reflect the signal light to the receiving fiber.

[0100] Specifically, the coupling mirror group 5 can consist of one or more mirrors. For example, the coupling mirror group 5 can be an off-axis large-aperture aspherical mirror. The induced laser emitted from the transmitting fiber may have a certain divergence angle. The coupling mirror group 5 can efficiently converge, collimate, or shape these laser beams and accurately reflect them, guiding them to the zoom mirror group 4 on the principal optical axis. This ensures that the induced laser has optimal beam quality and energy distribution when entering the subsequent optical path, laying the foundation for precise focusing and excitation on the surface of the sample under test.

[0101] The signal light returning from the sample under test, after passing through the transceiver group 3 and the zoom lens group 4, is incident again on the coupling lens group 5. The coupling lens group 5 can efficiently collect these weak and usually divergent signal lights and accurately reflect and focus them into the core of the receiving fiber, which is separate from the transmitting fiber.

[0102] In this configuration, the spatial coupling structure 6 achieves effective separation of the induced laser and the signal light by physically separating the transmitting and receiving fibers and utilizing the focusing / collimating characteristics of the reflector. The induced laser is emitted from the transmitting fiber and directed towards the sample under test via the reflector; the signal light returns from the sample and is focused onto the receiving fiber via the same reflector. Precise fiber end-face positioning prevents the induced laser from directly entering the receiving fiber.

[0103] The laser-induced spectral detection system provided in this embodiment of the invention ensures the purity and efficiency of laser excitation and signal collection through the coupling mirror group 5, and, combined with the physically separated fiber layout, minimizes background noise and significantly improves the signal-to-noise ratio and detection limit.

[0104] In some embodiments, the zoom lens group 4 is a Kohler three-element structure, and the transceiver lens group 3 is a single Fresnel lens.

[0105] Specifically, the zoom lens group 4 is a Kohler three-lens structure consisting of three lenses: convex lenses at the front and back, and a concave lens in the middle. Zooming is achieved by adjusting the relationship between the lenses. Zoom lens group 4 ensures excellent uniformity and shape stability of the induced laser spot 1 throughout the entire zoom range. Simultaneously, it precisely controls the aperture and position of the signal detection field of view 2, maintaining an ideal match with the induced laser spot 1. The transceiver lens group 3 is a single Fresnel lens, which, based on the principle of diffraction, converges the induced laser and signal light.

[0106] The laser-induced spectral detection system provided in this embodiment of the invention uses a Kohler three-element zoom lens group 4 to ensure precise matching and uniformity of the induced laser spot 1 and the signal detection field of view 2 during zooming, thereby greatly improving the signal-to-noise ratio. The Fresnel lens, serving as the transceiver lens group 3, enables the convergence of the induced laser and the signal light.

[0107] The laser-induced spectral detection system provided by the present invention will be further described below with reference to several specific embodiments.

[0108] Example 1 describes a remote laser-induced fluorescence detection system specifically designed for detection applications at distances of 10m to 100m. The system employs a coaxial transceiver integrated optical layout and possesses precise zoom and field-of-view synchronization control capabilities. Figure 4 This is a second schematic diagram of the structure of the laser-induced spectral detection system provided in this embodiment of the invention, as shown below. Figure 4As shown, the structure of the laser-induced spectral detection system is as follows: the laser-induced light source 7, the coupling mirror group 5, the zoom mirror group 4, and the transceiver mirror group 3 are arranged sequentially on the main optical axis of the system; the spatial coupling structure 6 includes a first reflecting mirror 61 with a small hole, and the coupling mirror group 5 is located in the small hole of the first reflecting mirror 61; the aperture stop 10 is set in front of the zoom mirror group 4, and the field stop 11 is set behind the transceiver mirror group 3; the laser-induced light source 7 emits induced laser through an optical fiber, the spectral acquisition system 8 receives signal light through an optical fiber, and the spectral acquisition system 8 is communicatively connected to the data processing and control system 9.

[0109] The parameters of each component in the system are as follows: the laser-induced light source 7 is a semiconductor laser module capable of achieving adjustable induced laser output from 1 to 10W; the core diameter of the laser coupling output fiber is 0.1mm, and the numerical aperture (NA) is 0.22; the core diameter of the spectral signal coupling input fiber is 0.4mm, and the numerical aperture (NA) is 0.22; the coupling mirror group 5 consists of one aspherical lens; the first reflecting mirror 61 is a parabolic reflecting surface with a 45° incident angle, coated with a silver film and a surface SiO2 protective film; the zoom lens group 4 consists of three lenses. It has a divergence angle adjustment capability of 50~100mrad; due to the influence of the laser irradiation distance, the transceiver group 3 is composed of a convex lens with a diameter of 100mm; the diameter adjustment range of the induced laser spot 1 is 1.0m to 2.0m, and the diameter adjustment range of the signal detection field of view 2 is 0.8m to 1.6m; the spectral acquisition system 8 is a fiber optic spectrometer with a Czerny-Turner structure, which uses a 4096-pixel linear CCD array to acquire the spectral signal after spectral dispersion; the data processing and control system 9 is a desktop computer.

[0110] The system works as follows: The laser-induced light source 7 emits an induced laser through a laser-coupled output fiber. This induced laser passes through a coupling lens group 5, a zoom lens group 4, and a transceiver group 3 before being projected onto the sample. The coupling lens group 5 initially focuses and shapes the induced laser, the zoom lens group 4 adjusts the emission angle of the induced laser, and the transceiver group 3 projects the induced laser onto the sample to generate signal light. The coupling lens group 5, in conjunction with the zoom lens group 4 and the transceiver group 3, obtains an induced laser of a specific shape and size at a specific distance.

[0111] After passing through the transceiver lens group 3 and the zoom lens group 4, the signal light is incident on the first reflecting mirror 61 and reflected by the first reflecting mirror 61 to the spectral signal coupling input optical fiber, where it is received by the spectral acquisition system 8. The field stop 11, in conjunction with the zoom lens group 4, synchronously controls the field of view. The aperture stop 10 adjusts the intensity of the signal light entering the system, maintaining a constant light intensity during zooming.

[0112] The spectral acquisition system 8 distinguishes the received plasma light into monochromatic lights of different wavelengths and orders, and performs digital imaging of the monochromatic lights. The data processing and control system 9 executes the following steps in sequence: (1) wavelength calibration; (2) linear normalization of spectral signal intensity; (3) elimination of abnormal noise signals by wavelet transform; (4) obtaining curve functions by nonlinear fitting of spectral data; (5) calculating the peak area of ​​fluorescence signal; (6) obtaining the center wavelength by integration; (7) establishing an analysis data model of interference factors by machine learning algorithms, and extracting and correcting effective spectral information; (8) based on machine learning or deep learning algorithms such as Convolutional Neural Network (CNN) and Support Vector Regression (SVR), the chlorophyll content information of plants is derived from the extracted spectral data information, thereby realizing the recording of the change law of plant growth status.

[0113] In implementing co-focusing, it is necessary to achieve a fixed ratio between the induced laser spot 1 illumination range and the signal detection field of view 2 under two scenarios: arbitrary distance detection within a range of 10 to 100 m and adjustment of the spot diameter from 1.0 m to 2.0 m. This can significantly reduce noise interference from stray light in the external environment and improve the detection capability of weak fluorescence signals.

[0114] In Embodiment 1, the zoom lens group 4, combined with the induced laser parameters via the coupling lens group 5, controls the spacing between the internal lenses to vary within the range of 0.5 to 5.5 mm, thereby adjusting the diameter of the induced laser spot 1 from 1.0 m to 2.0 m. The aperture stop 10 and the field stop 11 work together, and in conjunction with the zoom lens group 4 under different diameter induced laser spot 1 conditions, the aperture of the aperture stop 1 is nonlinearly varied within the range of 6 to 22 mm, while the relative positions of the aperture stop 10 and the field stop 11 are varied within the range of 25 mm to 32 mm. This ensures that the ratio between the signal detection field of view 2 and the diameter of the induced laser spot 1 remains constant, thus achieving the co-zoom described in this patent.

[0115] Example 2 describes a detection system suitable for simultaneous acquisition and analysis of laser-induced breakdown spectroscopy and Raman spectroscopy at a distance of 1m to 2m. Figure 5 This is the third schematic diagram of the structure of the laser-induced spectral detection system provided in this embodiment of the invention, as shown below. Figure 5As shown, the structure of the laser-induced spectral detection system is as follows: the laser-induced light source 7, the zoom lens group 4, and the transceiver lens group 3 are arranged sequentially on the main optical axis of the system; the spatial coupling structure 6 includes a first reflecting mirror 61 with a small hole and a second reflecting mirror 62. The first reflecting mirror 61 is tilted on the main optical axis, and the second reflecting mirror 62 is parallel to the first reflecting mirror 61. The coupling lens group 5 is located on the reflection path of the second reflecting mirror 62; the laser-induced light source 7 emits induced laser light through space, the spectral acquisition system 8 receives the signal light through optical fiber, and the spectral acquisition system 8 is communicatively connected to the data processing and control system 9.

[0116] The parameters of each component in the system are as follows: The laser-induced light source 7 is a 1064nm semiconductor-pumped solid-state laser, capable of achieving 1~10W adjustable continuous induced laser output after realizing nanosecond pulse width pulsed laser output; the induced laser spot 1 is in a focused state, with a spot diameter of approximately 0.6mm; the signal detection field of view 2 is also in a near-focused state, determined by the diameter of the coupling fiber and the radial magnification of the optical system. Since the magnification of the optical system is taken as 5 times and the fiber core diameter is 0.4mm, the signal detection field of view 2 is approximately 2.0mm; the zoom lens group 4 consists of one concave lens, enabling zooming of the laser ablation distance from 1m to 2m, while simultaneously achieving approximate collimation of the signal light; affected by the laser ablation distance, the transmission and reception... The mirror group 3 consists of a 50mm diameter aspherical convex lens; the first reflecting mirror 61 and the second reflecting mirror 62 are both planar emission mirrors, wherein the first reflecting mirror 61 has a circular straight hole inclined at a 45° angle to the surface; the coupling mirror group 5 consists of a biconvex lens and a binary optical micro-machining structure; the spectral acquisition system 8 is a Czerny-Turner structure fiber optic spectrometer, which uses a 4096-pixel linear CCD to acquire the spectral signal after spectral dispersion; the data processing and control system 9 includes a wavelength meter based on grating rotation scanning to detect the intensity of light signals of different wavelengths, and a dedicated circuit system developed based on programmable logic devices, and integrates control signal communication with an RS232 serial port, all integrated into the device.

[0117] The system works as follows: The laser-induced light source 7 emits an induced laser through a laser-coupled output fiber. The induced laser passes through a small hole on the first reflecting mirror 61, then through the zoom lens group 4 and the transceiver group 3, and finally onto the sample under test. The zoom lens group 4 adjusts the emission angle of the induced laser, and the transceiver group 3 transmits the induced laser onto the sample under test to generate signal light.

[0118] After passing through the transceiver lens group 3 and the zoom lens group 4, the signal light is projected onto the first reflector 61. The first reflector 61 reflects the signal light onto the second reflector 62, which in turn reflects the signal light onto the coupling lens group 5, which then focuses the signal light onto the optical fiber connected to the spectral acquisition system 8.

[0119] The spectral acquisition system 8 distinguishes the received plasma light into monochromatic light of different wavelengths and orders, and performs digital imaging of the monochromatic light. The data processing and control system 9 performs the following steps: (1) Acquire the emission spectrum of the excited plasma by nanosecond pulsed laser ablation; (2) Acquire the Raman spectrum excited by 3W continuous laser; (3) Linearly normalize the intensity of the spectral signal; (4) Identify the emission spectral peaks of the elemental components; (5) Calculate the peak area of ​​the emission wavelength of the selected elemental spectral signal by Lorentz fitting; (6) Correct the peak area intensity ratio by combining the emission spectral characteristic formula of the plasma with parameters such as electron temperature, thereby realizing the simultaneous quantitative analysis of 12 elemental components such as Cr, Mg, Na, and Al in the sample; (7) Identify the spectral peaks of the Raman spectrum to determine the molecular composition of the sample; (8) Combine the analysis results of the laser-induced breakdown spectrum with the analysis results of the Raman spectrum to realize the identification of the molecular and elemental components of the sample, and comprehensively judge the composition and characteristics of the plastic sample accordingly.

[0120] During the zoom process, the zoom lens group 4 works in conjunction with the transceiver lens group 3 to achieve zooming over a distance of 1 to 2 meters. Under the control of the aperture edge aperture of the transceiver lens group 3, the zoom lens group 4, and the coupling lens group 5, and combined with the calculated reasonable spatial distance position, the field of view of the detection signal light is precisely limited, ensuring the signal-to-noise ratio and effectively improving the spectral signal detection effect.

[0121] Example 3 is an improvement based on Example 2. Figure 6 This is the fourth schematic diagram of the laser-induced spectral detection system provided in this embodiment of the invention, as shown below. Figure 6 As shown, the difference between Embodiment 3 and Embodiment 2 is that the laser-induced light source 7 includes a first laser-induced light source 71 and a second laser-induced light source 72, both of which are 1064nm semiconductor-pumped solid-state lasers; both the first reflector 61 and the second reflector 62 have rectangular holes inclined at a 45° angle to their surfaces. The induced laser emitted by the second laser-induced light source 72 exits through the rectangular hole of the second reflector 62, reaches the first reflector 61, and is combined by a right-angle prism on the first reflector 61 before exiting through the zoom lens group 4.

[0122] Example 4 mainly introduces the implementation method of the spatial coupling structure 6 being a dual-core optical fiber and the coupling mirror group 5 being a large-aperture off-axis aspherical mirror. Figure 7 This is the fifth schematic diagram of the laser-induced spectral detection system provided in the embodiments of the present invention, as shown below. Figure 7As shown, the spatial coupling structure 6 is implemented using a dual-core optical fiber. One core is connected to the laser-induced light source 7 to emit the induced laser; the other core is connected to the spectral information processing system 8 to acquire the spectral signal. The coupling mirror group 5 is a large-aperture off-axis aspherical mirror. In the laser emission path, the coupling mirror group 5 reflects the induced laser emitted from the fiber core connected to the laser-induced light source 7 in the spatial coupling structure 6 to the zoom mirror group 4. In the signal receiving path, the coupling mirror group 5 reflects the signal light to the fiber core connected to the spectral information processing system 8 in the spatial coupling structure 6. The zoom mirror group 4 is a Kohler triple-lens structure consisting of three lenses: convex lenses at the front and back, and a concave lens in the middle. Zooming is achieved by adjusting the relationship between the lenses. The transceiver group 3 is a Fresnel lens, which, based on the principle of diffraction, converges the induced laser and the signal light.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser-induced spectral detection system, characterized in that, include: Laser-induced light source, used to emit induced laser light; A spatial coupling structure is used to separate the emission path of the induced laser from the acquisition path of the signal light; The zoom lens group is used to adjust the size of the induced laser spot on the surface of the sample being tested, and simultaneously adjust the size of the signal detection field of view; wherein, the ratio of the size of the induced laser spot to the size of the signal detection field of view remains constant during the zooming and distance adjustment process; A transceiver assembly is used to emit the induced laser onto the surface of the sample under test and to receive the signal light generated by the sample under test. A spectral acquisition system is used to split and acquire data of the signal light received by the spatial coupling structure; A data processing and control system, which is communicatively connected to the spectral acquisition system, is used to analyze, process, and control the spectral data output by the spectral acquisition system; The laser-induced light source, the spatial coupling structure, the zoom lens group, and the transceiver group are arranged sequentially on the main optical axis of the system. The induced laser passes sequentially through the spatial coupling structure, the zoom lens group, and the transceiver group and is directed toward the sample under test. The signal light returns from the sample under test, passes sequentially through the transceiver group, the zoom lens group, and the spatial coupling structure, and is then introduced into the spectral acquisition system.

2. The laser-induced spectral detection system according to claim 1, characterized in that, The spatial coupling structure includes at least one reflector; wherein at least one of the reflectors has a small aperture; the small aperture is used to allow the induced laser to pass through and reach the zoom lens group; the reflective surface of the at least one reflector is used to reflect the signal light and guide it to the spectral acquisition system.

3. The laser-induced spectral detection system according to claim 2, characterized in that, The aperture is provided with an optical device for shaping the divergence angle, diameter, and spatial distribution of the induced laser, or with an optical device for collimating the induced laser.

4. The laser-induced spectral detection system according to claim 2, characterized in that, The system also includes: a coupling mirror assembly; The coupling mirror assembly is positioned on the main optical axis and located before or within the spatial coupling structure, for focusing and shaping the induced laser emitted by the laser-induced light source; or, The coupling mirror group is located on the optical path after the signal light is separated by the spatial coupling structure, and is used to focus the signal light into the spectral acquisition system.

5. The laser-induced spectral detection system according to claim 1, characterized in that, The spatial coupling structure includes a multi-core fiber bundle; the multi-core fiber bundle includes an emitting fiber connected to the laser-induced light source for emitting the induced laser, and a receiving fiber connected to the spectral acquisition system for receiving the signal light.

6. The laser-induced spectral detection system according to claim 5, characterized in that, The spacing between the fiber core of the transmitting fiber and the fiber core of the receiving fiber is within 0.1 mm to 5 mm.

7. The laser-induced spectral detection system according to claim 5, characterized in that, The system further includes a coupling mirror group, which is used to reflect the induced laser emitted by the transmitting fiber to the zoom lens group, and simultaneously reflect the signal light to the receiving fiber.

8. The laser-induced spectral detection system according to claim 1, characterized in that, The zoom lens group and the transceiver lens group include one or more of lenses, mirrors, or diffractive optical devices.

9. The laser-induced spectral detection system according to claim 1, characterized in that, The system also includes an aperture stop and a field stop; the aperture stop is located in front of the zoom lens group, and the field stop is located behind the transceiver lens group.

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