Near-infrared spectroscopy system and method for carbonaceous analysis

Abstract

The present invention provides a near-infrared spectral system and a carbonaceous analysis method for carbonaceous analysis. The near-infrared spectral system includes a light source, a coaxial optical path, an integrating sphere, and a spectrometer. The integrating sphere includes a light source inlet, a sample reflector, and a diffuse reflection outlet. The coaxial optical path is positioned between the light source and the integrating sphere and is coaxial with the integrating sphere. The distance between the coaxial optical path and the light source and the distance between the coaxial optical path and the integrating sphere are set so that light emitted from the light source enters the light source inlet and first irradiates the sample at the sample reflector without being directly diffusely reflected by the integrating sphere. The relative position of the sample reflector and the diffuse reflection outlet of the integrating sphere is set so that the reflected light from the sample is diffusely reflected multiple times within the integrating sphere before passing through the diffuse reflection outlet and entering the spectrometer. The spectrometer is used to generate spectral data of the sample. The spectrometer of the present invention is positioned at the rear, allows for easy replacement of different light sources depending on the signal intensity of the sample, has a compact and small structure, high light intensity, and a high signal-to-noise ratio.

Description

Technical Field

[0001] The present invention relates to the technical field of carbonaceous analysis, and specifically, to a near-infrared spectrum system for carbonaceous analysis and a carbonaceous analysis method.

Background Art

[0002] Near-infrared spectrum technology has been increasingly widely regarded in many fields as a rapid and non-destructive inspection technology. As shown in FIG. 1, the two types of near-infrared spectrometers commonly used in the prior art are: one is a near-infrared spectrometer based on a diffraction grating. After the light emitted from the light source is absorbed by the sample, the remaining light is spectro-diffracted through the diffraction grating in the spectrometer, and after being received by the detector, the spectrum is obtained through data processing. The near-infrared spectrometer based on a diffraction grating has good anti-interference ability, but low accuracy, low signal-to-noise ratio, and between the light source and the diffraction grating, and between the diffraction grating and the detector, optical fibers are usually used for optical propagation, resulting in optical signal attenuation. The other is a near-infrared spectrometer based on Fourier transform. The light emitted from the light source is split into two beams by the beam splitter of the interferometer. One beam reaches the moving mirror of the interferometer through transmission, and the other is reflected to reach the fixed mirror of the interferometer. After being reflected by the fixed mirror and the moving mirror respectively, they return to the beam splitter. Since the moving mirror moves linearly at a constant speed, the two beams split by the beam splitter form an optical path difference and interfere. The interference light converges at the beam splitter and then passes through the sample cell. After passing through the sample, the interference light containing sample information reaches the detector, and the signal is processed by Fourier transform. Finally, a near-infrared absorption spectrum of transmittance or absorbance corresponding to the wavenumber or wavelength is obtained.

[0003] The conventional technology based on the Fourier transform near-infrared spectrometer has the following problems.

[0004] Firstly, the light source and interferometer are integrated, and the light emitted from the light source passes through the interferometer before passing through the sample. The light source and interferometer are fixed in place, and if the signal intensity of the sample is too low, the light source cannot be replaced with a high-power light source. Therefore, to change the light source, it is necessary to adjust the position between the lenses of the interferometer or replace the lenses with lenses of other parameters.

[0005] Secondly, because off-axis parabolic mirrors are used to convert the optical path between the light source and the interferometer, and between the interferometer and the detector, the optical conversion efficiency is low and the volume is large. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] To address one or more of the problems present in the prior art, the present invention provides a near-infrared spectral system for carbonaceous analysis, comprising a light source, a coaxial optical path, an integrating sphere, and a spectrometer, wherein the integrating sphere includes a light source inlet, a sample reflector, and a diffuse reflection outlet, the coaxial optical path is positioned between the light source and the integrating sphere and is coaxial with the integrating sphere, the distance between the coaxial optical path and the light source and the distance between the coaxial optical path and the integrating sphere are set so that light emitted from the light source enters the light source inlet and first irradiates the sample at the sample reflector without being directly diffusely reflected by the integrating sphere, the relative position of the sample reflector and the diffuse reflection outlet of the integrating sphere is set so that the reflected light from the sample is diffusely reflected multiple times within the integrating sphere before passing through the diffuse reflection outlet and entering the spectrometer, the spectrometer is used to generate spectral data of the sample. [Means for solving the problem]

[0007] According to one aspect of the present invention, the coaxial optical path includes a first collimating lens and a first focusing lens, wherein the first collimating lens converts light emitted from a light source into a parallel beam, and the first focusing lens is used to focus the parallel beam emitted from the first collimating lens directly onto the sample reflecting aperture through the light source entrance. Preferably, the smaller the collimation focal length of the first collimating lens, the smaller the distance between the first collimating lens and the light source 1, and the higher the light intensity of the parallel beam that has passed through the first collimating lens. Preferably, the distance between the first focusing lens and the first collimating lens is set such that the parallel beam collimated through the first collimating lens completely passes through the light source entrance of the integrating sphere and fills the sample reflection opening. More preferably, the first focusing lens is located at the light source entrance of the integrating sphere.

[0008] According to one aspect of the present invention, the diameters of the light source inlet, sample reflection port, and diffuse reflection outlet of the integrating sphere are progressively reduced, and the smaller the light source inlet of the integrating sphere, the higher the uniformity of the integrating sphere, and the smaller the diameter of the integrating sphere, the higher the optical efficiency of the integrating sphere. Preferably, the diameter of the integrating sphere is three times the diameter of the light source entrance. Preferably, the inner wall of the integrating sphere is gold-plated, more preferably the thickness of the gold plating is 2 to 12 microns, and even more preferably the thickness of the gold plating is 10 microns.

[0009] According to one aspect of the present invention, the integrating sphere further includes a light-shielding plate for increasing the number of times reflected light from a sample is diffusely reflected within the integrating sphere, Preferably, one end of the light-shielding plate is fixed to the inner wall of the integrating sphere, where the diffusely reflected light outlet faces the sample reflection port, and the other end of the light-shielding plate is inclined with respect to the inner wall of the integrating sphere and exhibits an acute angle along the optical axis direction of the diffusely reflected light outlet.

[0010] According to one aspect of the present invention, the other end of the light-shielding plate has a concave arc, and the arc of the concave arc is set such that the reflected light from one end of the sample reflection port near the diffuse reflection outlet does not exit the diffuse reflection outlet, and the reflected light from the other end of the sample reflection port away from the diffuse reflection outlet is reflected directly to the inner wall of the integrating sphere below the diffuse reflection outlet without passing through the light-shielding plate.

[0011] According to one aspect of the present invention, the spectrometer includes an interferometer, a detector, and a data processing module, wherein the interferometer corresponds to the diffusely reflected light outlet of the integrating sphere, the diffusely reflected light emitted from the integrating sphere undergoes diffraction by the interferometer, the detector is used to convert the diffraction into an electrical signal, and the data processing module is used to convert the electrical signal into spectral data.

[0012] Preferably, the spectrometer further includes a second collimating lens, and the interferometer includes a moving mirror, a beam splitter, and a fixed mirror, wherein the second collimating lens is used to convert the diffusely reflected light emitted from the diffusely reflected light outlet of the integrating sphere into a parallel beam, the beam splitter is used to split the parallel beam into two beams, the light from the two beams is reflected by the fixed mirror and the moving mirror and then returns to the beam splitter to meet again, forming an interference beam, the interference beam is focused to a detector, the movement of the moving mirror in the direction of incident light changes the optical path difference between the reflected beams of two different paths, a time-series interference signal is generated, the detector receives the interference signal and converts it into an electrical signal for output.

[0013] According to one aspect of the present invention, the invention further includes a second focusing lens, which is positioned between the diffusely reflected light outlet of the integrating sphere and the inlet of the spectrometer, for focusing the diffusely reflected light emitted from the diffusely reflected light outlet of the integrator towards the inlet of the spectrometer.

[0014] According to one aspect of the present invention, the invention further includes a window sheet installed above the sample reflection port.

[0015] According to another aspect of the present invention, a method for carbon analysis is provided, which is, Light emitted from the light source enters the integrating sphere via a coaxial optical path, directly irradiating the sample without diffuse reflection from the inner wall of the integrating sphere. This includes the process of the light reflected from the sample being diffusely reflected multiple times through an integrating sphere before entering the spectrometer, causing interference, and generating spectral data. [Effects of the Invention]

[0016] The optical path of the present invention sequentially passes through the light source, the light source inlet of the integrating sphere, the sample reflection port of the integrating sphere, and the diffusely reflected light outlet of the integrating sphere. Light emitted from the light source undergoes sequential reflection from the sample and multiple diffuse reflections within the integrating sphere before being diffracted by the spectrometer. Compared to conventional techniques, this offers the following advantages: The light source and spectrometer are separated, making it easy to switch between different light sources depending on the signal intensity of the sample. An off-axis beam mirror is not required, and the volume is reduced. Compared to incidence to the spectrometer via an optical fiber, the spatial light is more stable, and the spatial light enters the spectrometer directly through the integrating sphere, improving the signal-to-noise ratio. By preventing the situation where light emitted from the light source undergoes diffuse reflection in the integrating sphere and then reflects off the sample, and further diffuse reflection in the integrating sphere before directly entering the spectrometer without reflection off the sample, the influence of stray light on the spectral data generated in the above situation is eliminated, improving the signal-to-noise ratio. [Brief explanation of the drawing]

[0017] The accompanying drawings are provided for further understanding of the present invention, constitute part of the specification, and illustrate the present invention together with the embodiments of the present invention, and do not constitute limitations on the present invention. [Figure 1] This is a schematic diagram of a conventional near-infrared spectrometer. [Figure 2] This is a schematic diagram of one embodiment of a near-infrared spectroscopy system for carbonaceous analysis described in the present invention. [Figure 3] This is a schematic diagram of the three-dimensional structure of one embodiment of the near-infrared spectral system for carbonaceous analysis described in the present invention. [Figure 4] This is a schematic three-dimensional view of one embodiment of the integrating sphere described in the present invention. [Figure 5] This is a schematic diagram showing the installation position of the light-shielding plate in the integrating sphere described in the present invention. [Figure 6] This is a schematic diagram of one embodiment of the light-shielding plate described in the present invention. [Figure 7] This is a coordinate comparison diagram of the integrating sphere of the present invention and the integrating sphere of the conventional technology. [Modes for carrying out the invention]

[0018] Hereinafter, only some exemplary embodiments will be briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the accompanying drawings and description are considered to be illustrative in nature and not restrictive.

[0019] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. Of course, these are merely illustrative and do not limit the present invention. Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings, but it should be understood that the preferred embodiments described herein are only used for the description and interpretation of the present invention and not for limiting the present invention.

[0020] FIG. 2 is a schematic diagram of an embodiment of a near-infrared spectral system for carbonaceous analysis of the present invention. FIG. 3 is a three-dimensional schematic diagram of an embodiment of the near-infrared spectral system for carbonaceous analysis described in the present invention. As shown in FIGS. 2 and 3, the near-infrared spectral system for carbonaceous analysis includes a light source 1, a coaxial optical path 2, an integrating sphere 3, and a spectroscope 6. The integrating sphere 3 includes a light source inlet 31, a sample reflection port 32, and a diffuse reflection light outlet 33. The coaxial optical path 2 is installed between the light source 1 and the integrating sphere 3 and is coaxial with the integrating sphere 3. The distance between the coaxial optical path 2 and the light source 1 and the distance between the coaxial optical path 2 and the integrating sphere 3 are set such that the light emitted from the light source 1 first irradiates the sample at the sample reflection port 32 without directly diffusely reflecting in the integrating sphere 3 after entering through the light source inlet 31. The relative positions of the sample reflection port 32 and the diffuse reflection light outlet 33 of the integrating sphere 3 are set such that the reflected light of the sample enters the spectroscope 6 through the diffuse reflection light outlet 33 after diffusely reflecting multiple times inside the integrating sphere 3. The spectroscope 6 is used to generate spectral data of the sample.

[0021] The above spectral data includes the wave number or wavelength and the absorbance of the corresponding sample.

[0022] The light source 1 of the near-infrared spectroscopy system for carbonaceous analysis described above first passes through the coaxial optical path 2 to the integrating sphere 3, where it is reflected by the sample, then diffusely reflected multiple times by the inner wall of the integrating sphere 3 before being received by the spectrometer 6. The light source 1 and the spectrometer 6 are separated, making it easy to switch between different light sources depending on the difference in the signal intensity of the sample. For example, a high-power light source 1 is used when analyzing a sample with a low sample signal, and a low-power light source 1 is used when analyzing a sample with a strong sample signal.

[0023] Since the light from the near-infrared spectroscopy system described above, after being diffusely reflected by the integrating sphere 3, enters the spectrometer 6 directly, the spatial light is more stable and the signal-to-noise ratio is higher compared to when the light enters the spectrometer 6 via an optical fiber.

[0024] The light emitted from the light source 1 of the near-infrared spectral system for carbonaceous analysis passes through the coaxial optical path 2 and is focused onto the sample at the sample reflection port 32. The reflected light from the sample is diffusely reflected multiple times within the integrating sphere 3 before entering the spectrometer 6. By preventing the situation in which the light emitted from the light source 1 is diffusely reflected by the integrating sphere 3 and then reflected by the sample, and further diffusely reflected by the integrating sphere 3 and then enters the spectrometer 6 directly without being reflected by the sample, the influence of stray light on the spectral data generated in the above situation is eliminated, and the signal-to-noise ratio is improved.

[0025] In this invention, the light source 1 is connected to a coaxial optical path 2, the coaxial optical path 2 is connected to the lower end of an integrating sphere 3, the upper end of the integrating sphere 3 is connected to a sample, and the side end of the integrating sphere 3 is connected to a spectrometer 6, resulting in a compact structure and small volume.

[0026] In one embodiment, as shown in Figure 2, the near-infrared spectral system further includes a second focusing lens 5, which is positioned between the diffuse reflection outlet 33 of the integrating sphere 3 and the inlet of the spectrometer 6, for focusing the reflected light emitted from the diffuse reflection outlet 33 of the integrator towards the inlet of the spectrometer 6.

[0027] The smaller the focal length of the second condensing lens 5, the more preferable it is. The smaller the focal length of the second condensing lens 5, and the closer the distance between the second condensing lens 5 and the spectrometer 6, the more advantageous it is for miniaturizing the near-infrared spectral system.

[0028] In one embodiment, the near-infrared spectral system further includes a window sheet 4 positioned above the sample reflector 32, which projects a light beam focused by the light source 1 through the coaxial optical path 2 onto the sample.

[0029] Preferably, the window sheet 4 is rotatably attached to the sample reflection port 32.

[0030] As shown in Figure 2, the coaxial optical path 2 described in the present invention includes a first collimating lens 21 and a first focusing lens 22, wherein the first collimating lens 21 is used to convert light emitted from the light source 1 into a parallel beam, and the first focusing lens 22 is used to directly focus the parallel beam emitted from the first collimating lens 21 onto the sample reflection port 32 via the light source inlet 31.

[0031] The smaller the collimation focal length of the first collimating lens 21, the smaller the distance between the first collimating lens 21 and the light source 1, and the higher the light intensity of the parallel beam that has passed through the first collimating lens 21.

[0032] In one embodiment, the distance between the first focusing lens 22 and the first collimating lens 21 is set such that the parallel beam collimated through the first collimating lens 21 completely passes through the light source inlet 31 of the integrating sphere 3 and fills the sample reflection opening 32. Preferably, the first focusing lens 22 is located at the light source entrance 31 of the integrating sphere 3.

[0033] Figure 4 is a schematic three-dimensional view of one embodiment of the integrating sphere 3 described in the present invention. As shown in Figure 4, the integrating sphere 3 has three light openings: a light source inlet 31, a sample reflection opening 32, and a diffusely reflected light outlet 33. Key indicators of the integrating sphere 3 are light efficiency, reflectance, and uniformity. The size of the light openings is closely related to uniformity; the larger the diameter of the light openings, the lower the uniformity. The diameter of the integrating sphere 3 is related to light efficiency; the larger the diameter of the integrating sphere 3, the lower the light efficiency, and the smaller the diameter of the integrating sphere 3, the higher the light efficiency.

[0034] In addition to ensuring good uniformity, the signal intensity of the sample is also ensured. In one preferred embodiment, the diameter of the light source inlet 31 is within the range of the focal length of the first focusing lens 22 minus (0 to 0.5 mm), the diameter of the sample reflection port 32 is within the range of the diameter of the light source inlet 31 minus (1 to 5 mm), the diameter of the diffusely reflected light outlet 33 is within the range of 0.4 to 0.6 times the diameter of the sample reflection port 32, and the diameter of the integrating sphere 3 is 3 to 4 times the diameter of the light source inlet 31.

[0035] Preferably, when used for carbon analysis, the first focusing lens 22 is located at the light source inlet 31 of the integrating sphere 3, the diameter of the light source inlet 31 is the focal length of the first focusing lens 22, which is 0.4 mm, the diameter of the sample reflection port 32 is 5 mm, the diameter of the diffusely reflected light outlet 33 is 0.5 times the diameter of the sample reflection port 32, and the diameter of the integrating sphere 3 is 3 times the diameter of the light source inlet 31, so that the light signal from the light source 1 is strongest, the signal intensity of coal is strongest, and the uniformity of the integrating sphere 3 is highest.

[0036] As shown in Figure 5, the integrating sphere 3 is positioned above the diffuse reflection light outlet 33 and further includes a light-shielding plate 34 to increase the number of diffuse reflections of the sample's reflected light within the integrating sphere 3.

[0037] In one embodiment, one end of the light-shielding plate 34 is fixed to the inner wall of the integrating sphere 3, where the diffusely reflected light outlet 33 faces the sample reflection port 32, and the other end of the light-shielding plate 34 is inclined with respect to the inner wall of the integrating sphere 3 to form an acute angle along the optical axis direction of the diffusely reflected light outlet 33.

[0038] In one embodiment, as shown in Figures 5 and 6, the other end of the light-shielding plate 34 has a concave arc, and the arc of the concave arc is set such that the reflected light from one end of the sample reflection port 32 that is close to the diffuse reflection light outlet 33 does not exit the diffuse reflection light outlet 33, and the reflected light from the other end of the sample reflection port 32 that is farther from the diffuse reflection light outlet 33 does not pass through the light-shielding plate 34 but is directly reflected to the inner wall of the integrating sphere 3 below the diffuse reflection light outlet 33.

[0039] The reflectivity of an integrating sphere is related to the coating material and coating thickness. Conventional integrating spheres have an inner wall coated with polytetrafluoroethylene or barium sulfate. As shown in Figure 7, these two materials are absorbed in the 2000-2500 nm range. However, the carbonaceous spectral characteristic information peaks are mainly located in the 1600-2500 nm range. Therefore, by applying gold plating to the inner wall of the integrating sphere described in the present invention, carbonaceous spectral information can be represented more accurately, contributing to improved detection and analysis accuracy.

[0040] In one embodiment, the integrating sphere 3 is a copper sphere, and its inner wall is gold-plated. The gold plating must be uniform on the inner wall of the copper sphere and must not be too thick. If the gold plating is too thick, the cost is high and the reflectivity cannot be improved. If the gold plating is too thin, the uniformity of the integrating sphere is low and the reflectivity is low. Preferably, the thickness of the gold plating is 2 to 12 microns, and more preferably, the thickness of the gold plating is 10 microns.

[0041] In one embodiment, as shown in Figure 2, the spectrometer 6 includes an interferometer 62, a detector 63, and a data processing module 64. The interferometer 62 corresponds to the diffuse reflected light outlet 33 of the integrating sphere 3. Diffraction occurs in the diffuse reflected light emitted from the integrating sphere 3 by the interferometer 62. The detector 63 is used to convert the diffraction into an electrical signal, and the data processing module 64 is used to convert the electrical signal into spectral data.

[0042] The above spectral data includes wavenumber or wavelength and the corresponding absorbance of the sample. The data processing module 64 can also convert the spectral data into a spectrum, for example, a molecular spectrum with wavelength as the x-coordinate and absorbance as the y-coordinate. The molecular spectrum is used for carbon analysis, and parameters characteristic of carbon (such as calorific value, volatile matter, fixed carbon, moisture content, ash content, sulfur content, and particle size) can be analyzed. The more accurate the molecular spectrum, the more accurate the carbon analysis.

[0043] Preferably, the spectrometer 6 further includes a data interface 65 for transmitting spectral data to an external source.

[0044] In one embodiment, the spectrometer 6 further includes a second collimating lens 61, and the interferometer 62 includes a moving mirror 622, a beam splitter 621, and a fixed mirror 623. The second collimating lens 61 is used to convert the reflected light emitted from the diffusely reflected light outlet 33 by the integrating sphere 3 into a parallel beam. The beam splitter 621 is used to split the parallel beam into two beams. The light from the two beams is reflected by the fixed mirror 623 and the moving mirror 622, then returns to the beam splitter and meets again to form an interference beam. The interference beam is focused to a detector 63. The movement of the moving mirror 622 in the direction of the incident light changes the optical path difference between the reflected beams of two different paths, generating a time-series interference signal. The detector 63 receives the interference signal and converts it into an electrical signal for output.

[0045] Light emitted from the light source 1 of this invention first passes through the coaxial optical path 2 to the integrating sphere 3, is reflected by the sample, and then undergoes multiple diffuse reflections from the integrating sphere 3 before entering the interferometer 62. The light source 1 and the interferometer 62 are completely separated, making it easy to adjust the light source power according to differences in the signal intensity of the sample.

[0046] The interferometer 62 of the present invention is positioned at the rear, and light emitted from the light source 1 is reflected by the sample, then diffusely reflected multiple times by the integrating sphere 3, before directly entering the interferometer 62. Off-axis parabolic mirrors are not required between the light source 1 and the interferometer 62, and between the interferometer 62 and the detector 63, thus reducing the volume.

[0047] This invention further provides a method for analyzing carbonaceous properties, which is: Light emitted from the light source enters the integrating sphere via a coaxial optical path, directly irradiating the sample without diffuse reflection from the inner wall of the integrating sphere. This includes the process of the light reflected from the sample being diffusely reflected multiple times through an integrating sphere before entering the spectrometer, causing interference, and generating spectral data.

[0048] The above are preferred embodiments of the present invention and are not intended to limit it. While the present invention has been described in detail with reference to the above embodiments, those skilled in the art can modify the technical proposals described in each of the above embodiments or replace some of the technical features with equivalents. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. [Explanation of symbols]

[0049] 1-Light source, 2-Coaxial optical path, 21-First collimating lens, 22-First focusing lens, 3-Integrating sphere, 31-Light source inlet, 32-Sample reflection port, 33-Diffuse reflection outlet, 34-Shading plate, 4-Window sheet, 5-Second focusing lens, 6-Spectrometer, 61-Second collimating lens, 62-Interferometer, 621-Beam splitter, 622-Moving mirror, 623-Fixed mirror, 63-Detector, 64-Data processing module, 65-Data interface.

Claims

1. A near-infrared spectroscopy system for carbonaceous analysis, comprising a light source, a coaxial optical path, an integrating sphere, a second focusing lens, and a spectrometer, wherein the second focusing lens is positioned between the diffuse reflection outlet of the integrating sphere and the inlet of the spectrometer, the integrating sphere comprises a light source inlet, a sample reflector, and a diffuse reflection outlet, the coaxial optical path is positioned between the light source and the integrating sphere and is coaxial with the integrating sphere, the coaxial optical path comprises a first collimating lens and a first focusing lens, the first collimating lens is used to convert light emitted from the light source into a parallel beam, the first focusing lens is used to focus the parallel beam emitted from the first collimating lens directly through the light source inlet to the sample reflector, and the distance between the coaxial optical path and the light source and the distance between the coaxial optical path and the integrating sphere are relative to the light source. The light emitted from the light source is set to first irradiate the sample at the sample reflection port without being directly diffusely reflected by the integrating sphere after entering from the light source inlet. The relative position of the sample reflection port and the diffusely reflected light outlet of the integrating sphere is set so that the light reflected from the sample is diffusely reflected multiple times within the integrating sphere before passing through the diffusely reflected light outlet and being focused into a spectrometer via a second focusing lens. The spectrometer is used to generate spectral data of the sample. The spectrometer includes an interferometer, a detector, and a data processing module. The interferometer corresponds to the diffusely reflected light outlet of the integrating sphere and is positioned behind it. The diffusely reflected light emitted from the integrating sphere undergoes interference by the interferometer. The detector is used to convert the interference into an electrical signal, and the data processing module is used to convert the electrical signal into spectral data. Herein, the diameters of the light source inlet, sample reflection port, and diffuse reflection outlet of the integrating sphere decrease in sequence, the diameter of the light source inlet is within the range of 0 to 0.5 mm of the focal length of the first focusing lens, the diameter of the sample reflection port is within the range of 1 to 5 mm of the diameter of the light source inlet, the diameter of the diffuse reflection outlet is within the range of 0.4 to 0.6 times the diameter of the sample reflection port, and the diameter of the integrating sphere is 3 to 4 times the diameter of the light source inlet, characterized in that, a near-infrared spectral system for carbonaceous analysis.

2. The near-infrared spectral system for carbonaceous analysis according to claim 1, characterized in that the distance between the first focusing lens and the first collimating lens is set such that the parallel beam collimated through the first collimating lens completely passes through the light source entrance of the integrating sphere and fills the sample reflection opening.

3. The near-infrared spectral system for carbonaceous analysis according to claim 1, characterized in that the first focusing lens is located at the light source entrance of the integrating sphere.

4. The near-infrared spectral system for carbonaceous analysis according to claim 1, further comprising a light-shielding plate for increasing the number of times reflected light from a sample is diffusely reflected within the integrating sphere.

5. The near-infrared spectral system for carbonaceous analysis according to claim 4, characterized in that one end of the light-shielding plate is fixed to the inner wall of an integrating sphere extending from the diffusely reflected light outlet toward the sample reflection port, and the other end of the light-shielding plate is inclined with respect to the inner wall of the integrating sphere and exhibits an acute angle along the optical axis direction of the diffusely reflected light outlet.

6. The near-infrared spectral system for carbonaceous analysis according to claim 5, characterized in that the other end of the light-shielding plate has a concave arc, and the arc of the concave arc is set such that the reflected light from one end of the sample reflection port near the diffuse reflection port does not exit the diffuse reflection port, and the reflected light from the other end of the sample reflection port away from the diffuse reflection port does not pass through the light-shielding plate but is directly reflected to the inner wall of the integrating sphere below the diffuse reflection port.

7. The near-infrared spectral system for carbonaceous analysis according to claim 1, wherein the spectrometer further includes a second collimating lens, the interferometer includes a moving mirror, a beam splitter and a fixed mirror, the second collimating lens is used to convert diffusely reflected light emitted from a diffusely reflected light outlet into a parallel beam by an integrating sphere, the beam splitter is used to split the parallel beam into two beams, the light from the two beams is reflected by a fixed mirror and a moving mirror and then returns to the beam splitter to meet again, forming an interference beam, the interference beam is focused to a detector, the movement of the moving mirror in the direction of incident light changes the optical path difference between the reflected beams of two different paths, a time-series interference signal is generated, the detector receives the interference signal and converts it into an electrical signal for output.

8. The near-infrared spectral system for carbonaceous analysis according to claim 1, further comprising a window sheet installed above the sample reflector.

9. A method for performing carbonaceous analysis using a near-infrared spectral system according to any one of claims 1 to 8, Light emitted from the light source enters the integrating sphere via a coaxial optical path, directly irradiating the sample without diffuse reflection from the inner wall of the integrating sphere. A method characterized by comprising the following steps: the reflected light from a sample is diffusely reflected multiple times through an integrating sphere before entering a spectrometer, causing interference and generating spectral data.

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