Double-telecentric optical machine structure and optical path system for coal quality analysis

Abstract

The application discloses a kind of double telecentric light machine structures and optical path systems for coal quality analysis, belong to measurement technical field, a kind of double telecentric light machine structures, including dichroic mirror and collimating lens group, the reflecting surface of the collimating lens group is aligned to the dichroic mirror, it is characterized in that, the collimating lens group includes first collimating lens, second collimating lens and aperture diaphragm, the first collimating lens is set to align the reflecting surface of the dichroic mirror, and second collimating lens is set in the side of the first collimating lens away from the dichroic mirror, the aperture diaphragm is set in the side of the second collimating lens away from the first collimating lens, the second collimating lens, the first collimating lens and the aperture diaphragm are coaxial, this double telecentric light machine structure is used in coal quality analysis optical path system, so that the system can stably collect the spectral signal of coal powder when carrying out continuous coal quality analysis, overcome the problem of coal quality acquisition signal drift.

Description

Technical Field

[0001] The present invention relates to the field of measurement technology, and in particular to a double-telecentric optical-mechanical structure and an optical path system for coal quality analysis. Background Art

[0002] In coal-fired power plants, the quality of the coal entering the combustion furnace needs to be tested. This testing method primarily involves on-site sampling, followed by sample preparation and offline analysis in the laboratory. This long and inefficient testing process has made it difficult to meet the requirements for optimizing boiler operation based on rapid online coal testing results. In recent years, laser-induced breakdown spectroscopy (LIBS) has been widely used to directly measure pulverized coal in a particle flow state. LIBS directly measures particle flows by focusing a pulsed laser beam onto the center of a freely falling stream of pulverized coal particles, ablating them within a certain range and generating a plasma. A spectrometer then detects the spectral signals emitted by the plasma during its decay and cooling process. By analyzing spectra with specific wavelengths and intensities, the species and concentrations of the pulverized coal are determined.

[0003] While LIBS offers the advantage of directly measuring particle flow without sample preparation for coal pulverization, numerous studies have found that this measurement scheme suffers from poor spectral signal stability. The random variations in the number, size, and spatial distribution of particles near the laser focal point create a complex interaction between the laser and particles. This results in not only significant morphological variations in the generated plasma, but also drifting of the plasma center relative to the laser focal point.

[0004] Patent application CN112334484A discloses a method and apparatus for rapid online testing of coal quality composition in coal-fired power plants. The method involves extracting pulverized coal from the power plant's pulverized coal pipeline, separating and capturing the pulverized coal particles using a cyclone separator, and then mixing and dividing the pulverized coal into two fractions. The moisture, ash, volatile matter, and fixed carbon content of one fraction are measured using industrial analysis based on programmed temperature ramping and weighing. Furthermore, the concentrations of C, H, O, N, and S in the other fraction are measured using elemental analysis based on laser-induced breakdown spectroscopy. This method, which measures dynamically flowing pulverized coal, has a limited sampling range and cannot compensate for signal fluctuations caused by drift in the center position of the particle flow plasma, resulting in data drift and limited accuracy.

[0005] Another patent application, CN104931299A, discloses a uniform and continuous industrial powder sampling device and method for laser-induced detection. This device addresses the challenge of uniform and continuous sampling when laser-induced detection technology is applied to online solid powder testing in industrial production. The device includes a sampling pipeline, a jet valve, a gas vibrator, a measurement chamber, a dust control system, and a powder concentration variation measurement and compensation device. However, this device and method also suffer from limited sampling range and data drift, presenting certain limitations. Summary of the Invention

[0006] One of the purposes of the present invention is to provide a dual-telecentric optical machine structure, which solves the problem that the collected light rays deviate within a certain range and cause the optical signals to interfere with each other.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0008] A double-telecentric optical machine structure includes a dichroic mirror and a collimating lens group, the collimating lens group is aligned with the reflective surface of the dichroic mirror, the collimating lens group includes a first collimating lens, a second collimating lens and an aperture stop, the first collimating lens is configured to align with the reflective surface of the dichroic mirror, and the second collimating lens is arranged on a side of the first collimating lens away from the dichroic mirror, the aperture stop is arranged on a side of the second collimating lens away from the first collimating lens, and the second collimating lens, the first collimating lens and the aperture stop are coaxial.

[0009] Preferably, the first collimating lens is a quartz meniscus concave-convex lens, and the second collimating lens is a quartz single convex lens, which can deflect and collimate the light away from the axis of the collimating lens group.

[0010] Preferably, a focusing lens is further included, and the focusing lens includes a first focusing lens and a second focusing lens, the first focusing lens is configured to align with the transmission surface of the dichroic mirror, and the second focusing lens is configured between the first focusing lens and the dichroic mirror. The first focusing lens adopts a quartz meniscus concave-convex lens, and the second focusing lens adopts a quartz plano-convex lens, which are used to converge parallel light and control the position of the focus.

[0011] Preferably, a receiving lens is further included, which is arranged on a side of the collimating lens group away from the dichroic mirror and is used to receive light and converge it into a stable light spot.

[0012] Preferably, the receiving lens is configured as a plano-convex lens, which has a good light-convexity effect.

[0013] Preferably, a right-angle prism is further included, and the right-angle prism is arranged on a side of the aperture stop away from the second collimating lens, and is used to vertically deflect the light, change the direction of light transmission, and reduce the volume of the optical-mechanical structure.

[0014] Preferably, a protective lens is further included, wherein the protective lens is arranged to align with the reflective surface of the dichroic mirror and is used to protect the dichroic mirror from being affected by the external environment when reflecting light.

[0015] Preferably, the receiving lens is configured as a plano-convex lens to converge the transmitted light into a light spot and then transmit it.

[0016] As a better option, it also includes a chassis, which is used to protect the dichroic mirror, the collimating lens group, the receiving lens and the reflector, prevent the external environment from contaminating the optical-mechanical structure, increase its service life and reduce the failure rate.

[0017] The second object of the present invention is to provide an optical path system for coal quality analysis, which solves the problem of plasma light drifting within a certain range in continuous coal powder detection and improves the stability and accuracy of signal acquisition.

[0018] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0019] An optical path system for coal quality analysis includes a double-telecentric optical structure, a first incident light, a second incident light, and a spectrometer. The first incident light is incident perpendicular to a reflected light axis collinear with the axis of the collimating lens group, and then passes through the transmission surface of the dichroic mirror and the protective lens. The focus of the first incident light is projected outside the protective lens. The second incident light is emitted from the focus of the first incident light, passes through the protective lens and enters the chassis. The second incident light passes through the reflective surface of the dichroic mirror, is reflected and enters the collimating lens group, is collimated when passing through the first collimating lens and the second collimating lens, and is then partially filtered by the aperture stop. The remaining part at the center is reflected by the right-angle prism into the receiving lens, focused by the receiving lens into convergent light, and finally incident on the receiving end of the spectrometer.

[0020] Preferably, the angle between the dichroic mirror and the first incident light is 45°, the first incident light is emitted by a pulsed laser generator, and the second incident light is plasma light formed by ablating coal powder particles. The appropriate reflection angle can reduce the volume of the optical path system and increase its scope of application.

[0021] The beneficial effects of the present invention are:

[0022] (1) The double-telecentric optical machine structure has a double-telecentric optical structure consisting of a receiving lens and a collimating lens group. The coal powder plasma will drift, and only the main light part of the plasma radiation light will propagate in parallel, while the rest of the light has a certain angle with the parallel light. When the position of the plasma light changes, the angle of this part of the light changes, and the size of the final light spot will also change. The double-telecentric optical structure can collimate and converge the main light part of the plasma and block the rest of the non-parallel light parts, so that the plasma light whose center position drifts within a certain range can be stably and clearly collected.

[0023] (2) The collimating lens group of the double-telecentric optical machine structure is equipped with an aperture diaphragm that can filter the coal powder plasma light, reduce the penetration of other interfering light, and improve the accuracy of spectral acquisition.

[0024] (3) The incident light of the optical path system is coaxial with the collected plasma light signal, and the plasma light signal is reflected twice at 90 degrees, which reduces the structural volume of the entire optical path system and improves the scope of application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A structural diagram of a dual-telecentric optical machine provided by the present invention;

[0026] Figure 2 Diagram of the optical path system for coal quality analysis provided by the present invention.

[0027] Reference numerals:

[0028] 1. Focusing lens; 11. First focusing lens; 12. Second focusing lens; 2. Dichroic mirror; 3. Collimating lens group; 31. First collimating lens; 32. Second collimating lens; 33. Aperture stop; 4. Right-angle prism; 5. Chassis; 6. Receiving lens; 7. Fiber coupler; 8. Protective lens; 9. Powder feeding device; R1, first incident light; R2, second incident light; R3, converging light; A1, incident optical axis; A2, reflected optical axis; A3, output optical axis; 101, laser; 102, spectrometer. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] like Figure 1-2As shown, an optical path system for coal quality analysis is mainly used for coal quality component detection, which includes a double telecentric optical machine structure, a laser 101, a spectrometer 102 and a powder feeding device 9. The double telecentric optical machine structure includes a dichroic mirror 2 and a collimating lens group 3. The collimating lens group 3 is aligned with the reflection surface of the dichroic mirror 2. The collimating lens group 3 includes a first collimating lens 31, a second collimating lens 32 and an aperture stop 33. The first collimating lens 31 is arranged to align with the reflection surface of the dichroic mirror 2, and the second collimating lens 32 is arranged at the first collimating lens 31. The lens 31 is located on a side away from the dichroic mirror 2, and the aperture diaphragm 33 is arranged on a side of the second collimating lens 32 away from the first collimating lens 31. The second collimating lens 32, the first collimating lens 31 and the aperture diaphragm 33 are coaxial. A powder drop port is provided on the powder feeding device 9. The laser emitted by the laser 101 is aimed at the powder drop port and is perpendicular to the powder discharge direction of the coal powder. The dichroic mirror 2 is located between the laser 101 and the powder feeding device 9. The spectrometer 102 is used to receive the plasma light generated by the ablated coal powder particles passing through the collimating lens group 3.

[0031] Preferably, the first incident light R1 is incident perpendicular to the reflected optical axis A2, and passes through the transmission surface of the dichroic mirror 2 and the protective lens 8 in sequence. The focus of the first incident light R1 is projected outside the protective lens 8. The second incident light R2 is emitted from the focus of the first incident light R1, passes through the protective lens 8 and enters the chassis 5. The second incident light R2 passes through the reflecting surface of the dichroic mirror 2, is reflected at 90° and enters the collimating lens group 3. It is collimated when passing through the first collimating lens 31 and the second collimating lens 32, and then a part is filtered by the aperture stop 33. The remaining part in the center is reflected by the right-angle prism 4 into the receiving lens 6, and is gathered by the receiving lens 6 into the convergent light R3, and finally incident on the receiving end of the spectrometer 102.

[0032] Preferably, the angle between one side of the dichroic mirror 2 and the incident light axis A1 is 45°, and the angle between the other side of the dichroic mirror 2 and the reflected light axis A2 is 45°. The surface of the dichroic mirror 2 is coated, which can completely reflect light within a specific wavelength range, and at the same time almost completely transmit light of a certain wavelength. When used here, the transmission surface of the dichroic mirror 2 can transmit the laser emitted by the laser 101, and the reflection surface of the dichroic mirror 2 can completely reflect the plasma light formed by the ablation of coal powder. The laser and the plasma light are on the same axis, which ensures the accuracy of spectral sampling and simplifies the system structure.

[0033] Preferably, the powder feeding device 9 is composed of a vibrating feeder to spray the coal powder particles from the powder drop port. The particle diameter of the coal powder is less than 200 μm. The coal powder is transported to the powder drop port under high-frequency vibration and forms a cylindrical coal powder particle flow beam with a diameter of about 4 mm after free fall. The flow beam has a fixed central axis, and the stable coal powder particle flow beam makes the analysis results faster and more accurate.

[0034] Preferably, the first collimating lens 31 adopts a quartz concave-convex lens, and the second collimating lens 32 adopts a quartz single convex lens. The quartz glass lens has high light transmittance and good transmittance in the ultraviolet to infrared band. Experimental tests show that the parameters of the first collimating lens 31 are r1=204.921mm; r2=140.425mm; f=886.953mm and the parameters of the second collimating lens are r1=122.061mm; r2=297.481mm; f=175.557mm, which have the best effect.

[0035] Preferably, the optical path system is further provided with a chassis 5 and a protective lens 8. The dichroic mirror 2, the collimating lens group 3 and the right-angle prism 4 are all installed in the chassis 5. The protective lens 8 is a flat fused quartz glass lens and is embedded on the side wall of the chassis 5 near the powder feeding device 9. It is located between the powder feeding device 9 and the dichroic mirror 2. It is used to protect the precision optical devices in the chassis 5 from being affected by coal dust when receiving coal powder particle plasma light, thereby ensuring the stability and service life of the received signal.

[0036] Preferably, the spectrometer 102 adopts a polychromatic spectrometer, which consists of an incident slit, a dispersion system, an imaging system and one or more exit slits. The dispersion element is used to separate the electromagnetic radiation of the radiation source into the required wavelength or wavelength region, and the intensity is measured at the selected wavelength. The device uses a photomultiplier tube or other light detector to measure the intensity of the spectral line at different wavelength positions, and the material type analysis and determination of the coal powder is realized according to the different wavelengths of different substances.

[0037] Furthermore, the coal optical path system is also provided with a focusing lens 1, which is located between the laser 101 and the dichroic mirror 2. It is used to converge the light emitted by the laser and project the focus of the laser to the rear half of the coal powder particle flow beam where the central axis is away from the laser 101. The axis of the focusing lens 1 coincides with the incident light axis A1. The focusing lens 1 consists of a first focusing lens 11 and a second focusing lens 12. The first focusing lens 11 is configured to align with the transmission surface of the dichroic mirror 2, and the second focusing lens 12 is configured between the first focusing lens 11 and the dichroic mirror 2. The first focusing lens 11 adopts a quartz concave-convex lens, and the second focusing lens 12 adopts a quartz single convex lens. Its function is to converge the laser energy to a space with a size of ~100 μm around the focus, which is called the focal volume. The energy density in the focal volume exceeds the breakdown threshold of the coal powder particle flow, and the coal powder particles are broken down and ablated to generate plasma.

[0038] Preferably, the laser 101 adopts a pulse laser, which refers to a laser whose single laser pulse width is less than 0.25 seconds and which works only once per certain time interval, and has the characteristics of large output power. The laser used here has a wavelength of 1064 nm, a pulse width of 8 ns, and a Gaussian laser beam with a spot diameter. The laser beam is parallel to the focusing lens 1 composed of the first focusing lens 11 and the second focusing lens 12, and changes from a parallel state to a focused state. During the focusing process, the laser beam first penetrates through the dichroic mirror 2 and then passes through the protective lens 8, and finally forms a theoretical laser focus point in the rear half of the coal particle flow beam center axis away from the laser 101, so as to realize sufficient ablation of the coal particles in a short time and form a plasma. The theoretical laser focus point of the focusing lens 1 is located behind the center axis of the coal particle flow beam, that is, the coal particles are broken down and ablated in the defocusing area of the laser beam, the interaction space of the expanded beam and the particle flow is increased, the number of particles ablated by the laser is increased, and the probability of serious drift of the plasma center position is also reduced.

[0039] Preferably, the center of the circular light-emitting window of the laser 101, the laser focusing lens 1, the dichroic mirror 2, and the protective lens 8 should be strictly coaxial with the laser focus point, that is, the centers of the above-mentioned elements are located on the laser incident optical axis A1, and the incident optical axis is perpendicular to the center axis of the coal particle flow, so that the laser can be focused vertically to the center axis of the coal particle flow beam.

[0040] Preferably, the light path system also has a right-angle prism 4, which is a triangular reflector arranged between the collimating lens group 3 and the spectrometer 102. The collimated first incident light ray R1 is used to adjust the angle of the collected light and reduce the volume of the light path system.

[0041] Preferably, the centers of the right-angle prism 4, the collimating lens group 3, and the dichroic mirror 2 are coaxial with the reflected optical axis A2, and the right-angle prism 4, the fiber coupler 7, and the receiving lens 6 also need to be coaxial, that is, the centers of the above-mentioned elements are coincident with the exit optical axis A3. In addition, the coal plasma light is reflected by 90° twice before being collected to the receiving lens 6, the angle between the dichroic mirror 2 and the laser incident optical axis A1 and the collimating lens group axis is kept at 45°, and the angle between the inclined surface of the right-angle prism 4 and the collimating lens group axis and the exit optical axis A3 is strictly kept at 45°, so that the plasma light can be collected to the receiving end of the spectrometer 102.

[0042] Preferably, the receiving lens 6 is arranged on the side of the collimating lens group 3 away from the dichroic mirror 2. The receiving lens 6 is connected to the spectrometer 102 through an optical fiber. The spectral signal collected by the receiving lens 6 is transmitted to the spectrometer 102 to achieve uniform transmission of the optical signal and reduce the attenuation of the optical signal transmission. The receiving lens 6 adopts a plano-convex lens made of quartz. When used here, it can receive the reflected light from the right-angle prism 4 and converge it to form a light spot. The size of the light spot after passing through the collimating lens group 3 is stable, and the size of the light spot after being converged by the receiving lens 6 also remains unchanged. The plasma light convergence axis A3 falls on the center of the receiving lens 6 and is projected to the receiving end of the spectrometer 102 through the optical fiber for analysis.

[0043] Preferably, the fiber optic coupler 7 connects the receiving lens 6 and the optical fiber. The fiber optic coupler 7 realizes a detachable connection between the optical fibers and precisely connects the two end faces of the optical fibers, so that the light energy output by the transmitting optical fiber can be coupled to the receiving optical fiber to the maximum extent, and the impact of its intervention in the optical link on the system is minimized. The fiber optic coupler 7 is installed on the optical fiber installation and adjustment frame, which can adjust the position of the optical fiber connection line, facilitating the placement of the spectrometer 102 and the operator's observation.

[0044] The specific process of coal quality testing is as follows:

[0045] Powder discharge: The powder supply device 9 discharges coal powder at a constant flow rate and flow velocity, and the flow cross-section of the coal powder particle flow is a regular shape; laser focusing: The laser focus is aligned to the side of the coal powder beam axis away from the laser 101; the positive and negative defocus areas of the laser cover the coal powder beam; Spectral acquisition: The laser 101 is started to ablate the coal powder particle flow, and the spectral information of the coal powder plasma is collected from the incident direction of the laser; the laser ablates the coal powder particle flow in a pulsed manner; the coal powder plasma light is reflected by the dichroic mirror 2 and separated from the laser; Information transmission: The spectral information is sent to the spectrometer 102 after the depth of field is expanded by the collimating lens group 3; Information processing: The spectrometer 102 processes the spectral information to obtain the material composition and proportion data in the coal powder.

[0046] The transmission process of plasma light is as follows:

[0047] The laser emitted by the laser 101 passes through the focusing lens 1 along the direction of the incident light axis A1, passes through the transmission surface of the dichroic mirror 2, converges on the coal powder particle flow and ablates it, and the strong light of the coal powder particle flow plasma radiation first passes through the protective lens 8 into the cabinet 5, and then is deflected by 90 degrees by the reflection surface of the dichroic mirror 2 into the collimating lens group 3, and the drifting plasma light only has the light in a certain range in the center parallel to the reflection light axis A2, and the rest has a certain angle with the reflection light axis A2, when the position of the coal powder plasma light changes, the angle also changes, and the spot size also changes, and the collimating lens group 3 converts all the plasma light into light parallel to the reflection light axis A2, and the parallel plasma light is reflected by 90 degrees by the right-angle prism 4 to the receiving lens 6, and then converges on the optical fiber coupler 7, and the plasma light is transmitted to the multi-channel spectrometer 102 through the optical fiber for light splitting, photoelectric conversion processing, and finally the characteristic spectrum of the coal powder particle flow is obtained through calculation.

[0048] The effects of the present application are as follows:

[0049] The coal quality optical path system adopts a double-telecentric optical structure composed of the receiving lens 6 and the collimating lens group 3, which can collimate, converge and filter the coal powder plasma light, and the coal powder plasma drifts in a certain range along the reflection light axis A2 in the direction of the laser incident light axis A1, after collimation, the double-telecentric optical structure can still stably and clearly converge the coal powder plasma light to the multi-core optical fiber, and the spot diameter after convergence does not change significantly, and the double-telecentric optical structure can well adapt to the situation that the coal powder particle flow plasma drifts before and after the focal point, and when the drift range of the plasma light in the laser incident light axis A1 is ±3mm, the double-telecentric optical detection structure can ensure that the size of the converged spot at the receiving end of the optical fiber does not change, thereby effectively overcoming the problem that the intensity of the plasma light received by the optical fiber changes significantly with the drift of the center position of the plasma, and improving the stability of the spectral signal.

[0050] The double-telecentric optical machine structure in the present application reduces the spherical aberration of the focusing lens 1 and excites the coal powder particles in the laser defocusing area, reduces the drift range of the center position of the coal powder particle flow plasma, and the double-telecentric optical machine structure can be used for on-line composition detection of solid powder, aerosol, liquid jet and other materials without stable surface and moving state.

[0051] According to the disclosure and teaching of the above description, those skilled in the art can also make changes and modifications to the above embodiments. Therefore, the present application is not limited to the specific embodiments disclosed and described above, and some modifications and changes of the application should fall within the protection scope of the claims of the present application. In addition, although some specific terms are used in the present specification, these terms are only for convenience of description and do not constitute any limitation on the application.

Claims

1. A double telecentric optical machine structure, comprising a dichroic mirror (2) and a collimating lens group (3), wherein the collimating lens group (3) is aligned with the reflecting surface of the dichroic mirror (2), characterized in that: The collimating lens group (3) comprises a first collimating lens (31), a second collimating lens (32) and an aperture stop (33); the first collimating lens (31) is arranged to align with the reflection surface of the dichroic mirror (2); the second collimating lens (32) is arranged on a side of the first collimating lens (31) away from the dichroic mirror (2); the aperture stop (33) is arranged on a side of the second collimating lens (32) away from the first collimating lens (31); the second collimating lens (32), the first collimating lens (31) and the aperture stop (33) are coaxial; The first collimating lens (31) is a quartz meniscus concave-convex lens, and the second collimating lens (32) is a quartz single convex lens; The invention also includes a focusing lens (1), wherein the focusing lens (1) includes a first focusing lens (11) and a second focusing lens (12), wherein the first focusing lens (11) is arranged to align with the transmission surface of the dichroic mirror (2), and the second focusing lens (12) is arranged between the first focusing lens (11) and the dichroic mirror (2), wherein the first focusing lens (11) is a quartz meniscus concave-convex lens, and the second focusing lens (12) is a quartz plano-convex lens; The surface of the dichroic mirror (2) is coated, the transmission surface of the dichroic mirror (2) can transmit the laser light emitted by the laser (101), and the reflection surface of the dichroic mirror (2) can completely reflect the plasma light formed by the ablation of the coal powder; It also includes a receiving lens (6), which is arranged on a side of the collimating lens group (3) away from the dichroic mirror (2).

2. The double telecentric optical machine structure according to claim 1, characterized in that: The receiving lens (6) is configured as a plano-convex lens.

3. The double telecentric optical machine structure according to claim 1, characterized in that: It also includes a right-angle prism (4), which is arranged on a side of the aperture stop (33) away from the second collimating lens (32).

4. The double-telecentric optical machine structure according to claim 3, characterized in that: It also comprises a protective lens (8), which is arranged to align with the reflecting surface of the dichroic mirror (2).

5. The double telecentric optical machine structure according to claim 4, characterized in that: It also includes a chassis (5), which is used to protect the dichroic mirror (2), the collimating lens group (3), the receiving lens (6) and the right-angle prism (4).

6. An optical path system for coal quality analysis, comprising a double-telecentric optical-mechanical structure, a first incident light (R1), a second incident light (R2) and a spectrometer (102), characterized in that: The double telecentric optical machine structure is the double telecentric optical machine structure according to claim 5, wherein the first incident light (R1) is incident perpendicularly to the reflected light axis (A2) collinear with the axis of the collimating lens group (3), and then passes through the transmission surface of the dichroic mirror (2) and the protective lens (8), the focus of the first incident light (R1) is projected outside the protective lens (8), and the second incident light (R2) is emitted from the focus of the first incident light (R1), passes through the protective lens (8) and enters the chassis In (5), the second incident light (R2) passes through the reflecting surface of the dichroic mirror (2), is reflected into the collimating lens group (3), is collimated when passing through the first collimating lens (31) and the second collimating lens (32), and is partially filtered by the aperture stop (33). The remaining central part is reflected by the right-angle prism (4) into the receiving lens (6), and is gathered by the receiving lens (6) into convergent light (R3), and finally is incident on the receiving end of the spectrometer (102).

7. The optical path system for coal quality analysis according to claim 6, characterized in that: The angle between the dichroic mirror (2) and the first incident light (R1) is 45 degrees. The first incident light (R1) is emitted by a pulse laser generator, and the second incident light (R2) is plasma light formed by ablating coal powder particles.

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