Raman sampling device

Abstract

The embodiment of the invention discloses a Raman sampling device, which comprises a Raman laser used for outputting a first parallel light beam; the negative lens unit is used for diverging the first parallel light beam output by the Raman laser; the positive lens unit is used for converging the diverged first parallel light beams and integrating the diverged first parallel light beams into second parallel light beams; and the included angle between the axis of the light guide rod and the second parallel light beam is smaller than or equal to 5 degrees, so that the second parallel light beam is reflected in the light guide rod for more than 5 times. The Raman sampling device disclosed by the invention has the beneficial effects that the Raman sampling device realizes uniform distribution of exciting light of large light spots through the beam expanding and light uniformizing structure; a multi-point optical fiber collection structure is adopted, so that the scattered light collection efficiency is improved, and the detection repeatability and representativeness are ensured; the combination of the annular multiple optical fibers and the diffusion film is adopted at the receiving end, the multi-angle collection capacity of Raman scattering light is improved, the Raman sampling device is suitable for rapid detection of heterogeneous samples, and the problem of poor spectrum reproducibility is solved.

Description

Technical Field

[0001] The present invention relates to the field of optical and spectral detection methods, and in particular to a Raman sampling device. Background Art

[0002] Traditional Raman sampling heads mostly use a small, focused spot, suitable for micro-area analysis. For example, existing Raman sampling heads use a convex lens as a collimator. Because the laser spot is small, typically under 1mm, the spot size is very small, resulting in a relatively concentrated energy source. Summary of the Invention

[0003] However, for heterogeneous or coarse-grained samples (such as pharmaceutical powders, food, and fabrics), traditional Raman sampling devices are often insufficiently representative due to the small sampling area, and the spectral model fails. Simply amplifying the spot size will reduce the power density, resulting in a significant decrease in the Raman signal-to-noise ratio.

[0004] In order to overcome the above shortcomings, the purpose of the present invention is to provide a Raman sampling device that can output a large-diameter uniform light spot and improve the detection repeatability of Raman spectroscopy in complex mixed systems.

[0005] The present application discloses a Raman sampling device, comprising:

[0006] a Raman laser configured to output a first parallel light beam;

[0007] a negative lens unit, configured to diverge the first parallel light beam output by the Raman laser;

[0008] a positive lens unit, configured to converge the diverged first parallel light beams into a second parallel light beam;

[0009] A light guide rod, wherein the angle between the axis of the light guide rod and the second parallel light beam is less than or equal to 5°, so that the second parallel light beam is reflected more than 5 times in the light guide rod.

[0010] Preferably, the negative lens unit includes two convex lenses arranged along the light transmission direction, and the convex parts of the two convex lenses are arranged opposite to each other.

[0011] Preferably, the positive lens unit includes a plano-convex lens and a biconvex lens arranged along light transmission, wherein the convex portion of the plano-convex lens is arranged toward the biconvex lens.

[0012] Preferably, it is characterized in that the expansion ratio of the second parallel light beam compared with the first parallel light beam is greater than or equal to 8, the divergence angle is less than or equal to 0.5 mrad, and the beam wavefront error is less than λ / 4.

[0013] Preferably, the cross-sectional side length of the light guide rod is 5-8 mm, the length-to-diameter ratio L / D is 15, and the surface roughness Ra is ≤ 0.3 μm.

[0014] Preferably, the refractive index of the material of the light guide rod is greater than 1.4.

[0015] Preferably, the light guide rod is made of one or more of fused quartz, BK7 optical glass, sapphire, zinc sulfide, calcium fluoride and synthetic quartz.

[0016] Preferably, the light spot after passing through the light guide rod is between 5-10 mm.

[0017] Preferably, the Raman sampling device is used to sample heterogeneous or coarse particle samples.

[0018] Preferably, the Raman sampling device includes an optical diffusion film and a plurality of annular optical fibers, the optical diffusion film is used to receive light after passing through the sample, and the optical fibers are used to receive light output by the optical diffusion film, and the low haze of the optical diffusion film is between 8% and 12%.

[0019] The beneficial effects of the present invention are:

[0020] 1. The Raman sampling device achieves uniform distribution of excitation light in a large spot through beam expansion and light homogenization structure;

[0021] 2. Adopting a multi-point optical fiber collection structure to improve the scattered light collection efficiency, ensure the detection repeatability and representativeness, especially improve the detection repeatability of Raman spectroscopy in complex mixed systems;

[0022] 3. This Raman sampling device is suitable for rapid detection of heterogeneous samples, solving the problem of poor spectral reproducibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the components in the drawings are only schematic and are used to help understand the present invention, and do not specifically limit the shapes and proportional dimensions of the components of the present invention. Those skilled in the art can select various possible shapes and proportional dimensions to implement the present invention according to the specific circumstances under the guidance of the present invention. In the drawings:

[0024] Figure 1 Schematic diagram of the Raman sampling device in the present invention.

[0025] Figure 2 Schematic diagram of the principle of the negative lens unit and the positive lens unit in the present invention.

[0026] In the figure: 1. Raman laser; 2. Light guide rod; 3. Detection object; 4. Optical diffusion film; 5. Optical fiber; 6. Spectrometer; 7. Negative lens unit; 71. Convex lens; 8. Positive lens unit; 81. Plano-convex lens; 82. Biconvex lens; A. First parallel light beam; B. Second parallel light beam. DETAILED DESCRIPTION

[0027] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0028] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The following describes an embodiment of the present invention based on its overall structure.

[0029] The present application discloses a Raman sampling device, comprising:

[0030] A Raman laser 1, configured to output a first parallel light beam;

[0031] a negative lens unit 7, the negative lens unit 7 being used to diverge the first parallel light beam A output by the Raman laser 1;

[0032] a positive lens unit 8, the positive lens unit 8 being used to converge the divergent first parallel light beam A into a second parallel light beam B;

[0033] The light guide rod 2 has an included angle between the axis of the light guide rod 2 and the second parallel light beam B that is less than or equal to 5°, so that the second parallel light beam B is reflected more than 5 times in the light guide rod 2 .

[0034] With the above structure, the device achieves uniform distribution of excitation light through beam expansion and light homogenization structure, thus having the ability of large spot excitation and uniform sampling.

[0035] Specifically, the Raman laser 1 is used to output a first parallel light beam A (laser) outward.

[0036] In this embodiment, the negative lens unit 7 includes two convex lenses 71 arranged along the light transmission line, with the convex portions of the two convex lenses 71 facing each other. The two optically coupled convex lenses 71 can produce a negative focal length effect by adjusting the curvature radius and the refractive index of the material, which is beneficial for chromatic aberration and spherical aberration.

[0037] In this embodiment, the positive lens unit 8 includes a plano-convex lens 81 and a biconvex lens 82 arranged along the light transmission direction, wherein the convex portion of the plano-convex lens 81 is arranged toward the biconvex lens 82 .

[0038] After being processed by the negative lens unit 7 and the positive lens unit 8, the focal length ratio of the second parallel light beam B relative to the first parallel light beam A is the beam expansion ratio of the second parallel light beam B relative to the first parallel light beam A. Generally, the beam expansion ratio may be greater than or equal to 8. In an optional embodiment, the beam expansion ratio may be 10. Preferably, the output beam divergence angle of the second parallel light beam B relative to the first parallel light beam A is ≤0.5 mrad, and the beam wavefront error is less than λ / 4.

[0039] In this embodiment, the cross-section of the light guide rod 2 is square or hexagonal, which has better output uniformity. It is placed after the beam expander to improve the uniformity of the light spot. The cross-sectional side length is 5-8mm, the length-to-diameter ratio L / D=15 (the length-to-diameter ratio (L / D) of the light guide rod refers to the ratio of the axial length (L) of the light guide rod to the cross-sectional diameter (D). The larger the L / D value, the more times the light beam is totally reflected in the light guide rod, and the better the homogenization effect.), and the surface roughness Ra≤0.3μm. The light guide rod 2 is the key to light spot homogenization. It is a hollow or solid cylindrical structure made of high-refractive-index optical material (such as fused quartz). After the light beam enters, it is totally reflected on the side wall. After multiple reflections, light rays of different incident angles are mixed at the output end to achieve energy homogenization. At the same time, the low-haze diffusion film ensures the homogenization of the Raman scattered light of the sample, avoiding the difference in light information at different angles due to the surface state of the sample. Preferably, the refractive index of the optical material of the light guide rod 2 is greater than 1.4. The light guide rod 2 is made of one or more of fused quartz, BK7 optical glass, sapphire, zinc sulfide, calcium fluoride and synthetic quartz.

[0040] Preferably, the central optical axes of the negative lens unit 7 and the positive lens unit 8 are aligned in a straight line. This straight line is aligned with the axial direction of the light guide rod 2, and the angle between the second parallel light beam B and the axis of the light guide rod 2 is ≤5°, to ensure that the light beam is reflected more than 5 times within the light guide rod 2 and is fully homogenized, thereby outputting a uniform light spot with a diameter of 5-10 mm.

[0041] Preferably, the distance between the two convex lenses 71 in the negative lens unit 7 is between 1.3-1.7 mm. The distance between the plano-convex lens 81 and the biconvex lens 82 in the positive lens unit 8 is between 0.4-0.6 mm. The distance between the negative lens unit 7 and the positive lens unit 8 is between 80-100 mm.

[0042] In this embodiment, the Raman sampling device includes an optical diffusion film 4 and a plurality of annular optical fibers 5. The optical diffusion film 4 is used to receive light after passing through the sample. The optical diffusion film 4 is wavy. The input end of each optical fiber 5 is arranged adjacent to the optical diffusion film 4, so as to receive the light output by the optical diffusion film 4. A combination of annular multi-fibers and optical diffusion films is used at the receiving end to enhance the multi-angle collection capability of Raman scattered light. The output end of each optical fiber 5 is connected to a spectrometer 6. Preferably, the low haze of the optical diffusion film 4 is between 8% and 12%. The transmittance of the optical diffusion film 4 is greater than 85%, which uniformly collects the spatial information of the scattered light and finally transmits the multi-directional Raman light to the optical fiber 5 spectrometer 6.

[0043] The Raman spectroscopy sampling device in the embodiment of the present application achieves uniform distribution of the excitation light through a beam expansion and light homogenization structure. The multi-point optical fiber 5 collection structure improves the efficiency of scattered light collection, ensuring detection repeatability and representativeness. It is particularly suitable for rapid detection of heterogeneous test samples 3. Heterogeneous test samples 3 can be pharmaceutical powders, food, fabrics, etc.

[0044] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A Raman sampling device, characterized in that: include: a Raman laser configured to output a first parallel light beam; a negative lens unit, configured to diverge the first parallel light beam output by the Raman laser; a positive lens unit, configured to converge the diverged first parallel light beams into a second parallel light beam; A light guide rod, wherein the angle between the axis of the light guide rod and the second parallel light beam is less than or equal to 5°, so that the second parallel light beam is reflected more than 5 times in the light guide rod.

2. The Raman sampling device according to claim 1, characterized in that: The negative lens unit includes two convex lenses arranged along the light transmission line, and the convex parts of the two convex lenses are arranged opposite to each other.

3. The Raman sampling device according to claim 1, characterized in that: The positive lens unit includes a plano-convex lens and a biconvex lens arranged along light transmission, wherein the convex portion of the plano-convex lens is arranged toward the biconvex lens.

4. The Raman sampling device according to claim 1, characterized in that: Compared with the first parallel beam, the beam expansion ratio of the second parallel beam is greater than or equal to 8, the divergence angle is less than or equal to 0.5 mrad, and the beam wavefront error is less than λ / 4.

5. The Raman sampling device according to claim 1, characterized in that: The cross-sectional side length of the light guide rod is 5-8 mm, the length to diameter ratio L / D is 15, and the surface roughness Ra is ≤ 0.3 μm.

6. The Raman sampling device according to claim 1, characterized in that: The refractive index of the material of the light guide rod is greater than 1.

4.

7. The Raman sampling device according to claim 1, characterized in that: The light guide rod is made of one or more of fused quartz, BK7 optical glass, sapphire, zinc sulfide, calcium fluoride and synthetic quartz.

8. The Raman sampling device according to claim 1, characterized in that: The light spot after passing through the light guide rod is between 5-10mm.

9. The Raman sampling device according to claim 1, characterized in that: The Raman sampling device is used to sample heterogeneous or coarse particle samples.

10. The Raman sampling device according to claim 1, characterized in that: The Raman sampling device includes an optical diffusion film and multiple ring-shaped optical fibers. The optical diffusion film is used to receive light after passing through the sample, and the optical fibers are used to receive light output by the optical diffusion film. The low haze of the optical diffusion film is between 8% and 12%.

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