A material detection optical system based on Raman spectrometer

Abstract

The present invention relates to a material detection optical system based on a Raman spectrometer, comprising a laser excitation group, a converging lens group, an incident slit, and a spectroscope group. The laser excitation group comprises a plane reflector and a converging lens, the converging lens group comprises a first lens, a second lens, and a filter, a slit is provided at the incident portion of the spectroscope group, and the spectroscope group comprises a collimating lens, a diffraction grating, a third lens, a fourth lens, and a fifth lens. The laser excitation group directs laser light onto a sample, and the light reflected from the sample is converged by the converging lens group, then split by the spectroscope group, and finally detected by a detector. The material detection optical system based on a Raman spectrometer of the present invention can be applied over a wide spectral range while having the advantages of being miniaturized and lightweight.

Description

Technical Field

[0001] The present invention relates to the field of spectral analysis systems, and in particular to a material detection optical system based on a Raman spectrometer. Background Art

[0002] A Raman spectrometer is an analytical instrument based on the Raman scattering effect, used to study the molecular structure and chemical composition of substances. It is widely used in fields such as chemistry and materials, biomedicine, and the environment and food industry. Lasers are commonly used as excitation light sources due to their high monochromaticity and concentrated energy. When the laser is irradiated onto a sample, the incident light interacts with the sample, and some of the photon energy is absorbed or emitted by energy level changes caused by molecular vibrations, rotations, or electronic transitions, resulting in a change in the frequency of the scattered light. This frequency change is called a Raman shift, which reflects information about the molecular structure and chemical bonds. Raman scattering spectra typically contain information about the sample's structure, composition, and chemical bonds, and possess high resolution and chemical specificity.

[0003] Traditional Raman spectrometers have complex structures, are difficult to calibrate, and have high manufacturing costs, which reduces the flexibility of the system and makes it difficult to meet the needs of modern applications for miniaturization and portability. Summary of the Invention

[0004] In order to address the shortcomings of the existing technology, the present invention provides a material detection optical system based on a Raman spectrometer, which can cover a wide spectral range of 400nm to 700nm and achieve high-quality optical imaging effects while ensuring miniaturization and lightweight.

[0005] The present invention specifically relates to a material detection optical system based on a Raman spectrometer, comprising: a laser excitation group (1) composed of a plane reflector (11) and a first lens (12) arranged in sequence along an optical path, a converging lens group (2) composed of a second lens (21), a third lens (22) and a filter (23), an incident slit (3), and a spectroscope group (4) composed of a collimating lens (41), a diffraction grating (42), a fourth lens (43), a fifth lens (44) and a sixth lens (45); the laser excitation group (1) is used to converge a light beam emitted by a laser and incident on a sample surface, the converging lens group (2) is used to filter out Rayleigh scattering, and the spectroscope group (4) is used to split the light beam incident from the incident slit; The emitted light beam passes through the laser excitation group (1), is converged by the plane reflector (11) and the first lens (12) in sequence, and is incident on the surface of the sample to be tested. The light beam reflected back from the sample surface is converged by the converging lens group (2), filtered by the filter, and then incident on the incident slit (3). After being collimated and split by the spectroscope group (4), it is finally detected. The optical path of the light from the sample through the converging lens group (2) to the incident slit (3) is L1, and the optical path of the light from the sample to the detector is L, which satisfies the following relationship: 0.15≤L1 / L≤0.25; the optical focal length of the converging lens group (2) is Φ2, and the optical focal length of the material detection optical system is Φ, which satisfies the following relationship: 0.21≤Φ2 / Φ≤0.48.

[0006] Furthermore, the tilt angle θ1 of the plane reflector (11) satisfies 30°≤θ1≤50°, the optical focal length of the laser excitation group (1) is Φ1, and the optical focal length of the material detection optical system is Φ, which satisfies the following relationship: 0.16≤Φ1 / Φ≤0.35.

[0007] Furthermore, the focal power Φ of the second lens (21) is 21 , the focal power Φ of the third lens (22) 22 , which satisfies the following relationship: 0.5≤Φ 21 / Φ 22 ≤1.

[0008] Furthermore, the width w of the incident slit (3) satisfies w<0.02 mm.

[0009] Furthermore, the optical focal length of the beam splitter group (4) is Φ4, and the optical focal length of the collimating lens (41) is Φ 41 , the optical power of the fourth lens (43) is Φ 43 , the optical power of the fifth lens (44) is Φ 44 , the optical power of the sixth lens (45) is Φ 45 , which satisfies the following relationship: 0.02≤Φ 43 =Φ44 =Φ 45 ≤0.15,(Φ 43 +Φ 44 +Φ 45 ) / Φ4≤2, the optical focal length of the material detection optical system is Φ, which satisfies the following relationship: 0.36≤Φ4 / Φ≤0.52, the grating constant d of the diffraction grating (42) satisfies 0.8μm≤d≤2μm, and the tilt angle θ2 satisfies 19°≤θ2≤25°.

[0010] Furthermore, the distance between the fourth lens (43) and the fifth lens (44) is m1, and the distance between the fifth lens (44) and the sixth lens (45) is m2, which satisfy the following relationship: 0.34≤m2 / m1≤0.5.

[0011] Furthermore, the curvature radii of the fourth lens (43) are R1 and R2, the curvature radii of the fifth lens (44) are R3 and R4, and the curvature radii of the sixth lens (45) are R5 and R6, which satisfy the following relationship: 0.034≤R1=-R2=R3=-R4=R5=-R6≤0.08.

[0012] The Raman spectrometer-based material detection optical system provided by the present invention features a high degree of system stability through optimized component design. By employing a dual-module system for simultaneous laser excitation and spectral detection, it effectively eliminates stray light interference from the excitation light source, improving the reliability and accuracy of measurement data. Furthermore, the optical system utilizes only a simple spherical mirror, resulting in a simple structure and low cost, making it widely applicable. The present invention also features a simple detection optical path structure, utilizing only the simplest spherical mirror. This simplified optical path results in a smaller instrument, making it suitable for rapid testing in laboratories or on-site where space is limited.

[0013] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0015] Figure 1 The structure and optical path diagram of a material detection optical system based on a Raman spectrometer according to one embodiment of the present invention are shown;

[0016] Figure 2 A schematic diagram showing a display of diffuse spots corresponding to a material detection optical system based on a Raman spectrometer according to one embodiment of the present invention is shown;

[0017] Figure 3 A schematic diagram of a curve of a modulation transfer function corresponding to a material detection optical system based on a Raman spectrometer according to an embodiment of the present invention is shown.

[0018] Figure numerals: 1-laser excitation group, 11-plane mirror, 12-first lens, 2-converging lens group, 21-second lens, 22-third lens, 23-filter, 3-incident slit, 4-beam splitter group, 41-collimating lens, 42-diffraction grating, 43-fourth lens, 44-fifth lens, 45-sixth lens. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below with reference to the accompanying drawings: the described embodiments are only part of the embodiments of the present invention, not all of them. The following embodiments are only for more clearly illustrating the technical solutions of the present invention and cannot be used to limit the scope of protection of the present invention.

[0020] It should be noted that the unit of optical power in the present invention is mm⁻¹, the unit of curvature radius is mm, and the unit of eccentricity is mm.

[0021] In the embodiment disclosed in the present invention, a material detection optical system based on a Raman spectrometer includes, in order of the optical path, a laser excitation group 1 consisting of a plane mirror 11 and a first lens 12 arranged in sequence along the optical path, a converging lens group 2 consisting of a second lens 21 and a third lens 22, an entrance slit 3, and a beam splitter group 4 consisting of a collimating lens 41, a diffraction grating 42, a fourth lens 43, a fifth lens 44, and a sixth lens 45.

[0022] The laser excitation group 1 is used to converge the laser emitted by the laser; the converging lens group 2 converges the light beam reflected back from the sample surface, and then emits it after filtering out the Rayleigh scattering through the filter 23; the incident slit 3 is set on the output light axis of the converging lens group 2, which can improve the spectral resolution, suppress stray light, and improve the signal-to-noise ratio; the spectroscope group 4 is set on the other side of the incident slit 3, which is used for spectral splitting of the system.

[0023] The excitation light beam passes through the laser excitation group 1, is converged by the plane reflector 11 and the first lens 12 in sequence, and is incident on the surface of the sample to be measured. The light beam reflected back from the sample surface is converged by the converging lens group 2, filtered by the filter 23, and then incident on the incident slit 3. After being collimated and split by the spectrometer group 4, it is finally detected.

[0024] In one embodiment, the optical path of light from the sample through the converging lens group 2 to the incident slit 3 is L1, and the optical path of light from the sample to the detector is L, which satisfies the following relationship: 0.15≤L1 / L≤0.25; the optical focal length of the converging lens group 2 is Φ2, and the optical focal length of the material detection optical system is Φ, which satisfies the following relationship: 0.21≤Φ2 / Φ≤0.48.

[0025] In a preferred embodiment, the tilt angle θ1 of the plane mirror 11 satisfies 30°≤θ1≤50°, the optical focal length of the laser excitation group 1 is Φ1, and the optical focal length of the material detection optical system is Φ, which satisfies the following relationship: 0.16≤Φ1 / Φ≤0.35.

[0026] In a preferred embodiment, Figure 1 As shown, the optical power Φ of the second lens 21 is 21 , the focal power Φ of the third lens 22 22 , which satisfies the following relationship: 0.5≤Φ 21 / Φ 22 ≤1.

[0027] In a preferred embodiment, Figure 1 As shown, the width w of the incident slit 3 satisfies w<0.02 mm.

[0028] In a preferred embodiment, Figure 1 As shown, the focal length of the beam splitter group 4 is Φ4, and the focal length of the collimating lens 41 is Φ 41 , the focal length of the fourth lens 43 is Φ 43 , the optical power of the fifth lens 44 is Φ 44 , the optical power of the sixth lens 45 is Φ 45 , which satisfies the following relationship: 0.02≤Φ 43 =Φ 44 =Φ 45 ≤0.15,(Φ 43 +Φ 44 +Φ 45 ) / Φ4≤2, the optical focal length of the material detection optical system is Φ, which satisfies the following relationship: 0.36≤Φ4 / Φ≤0.52, the grating constant d of the diffraction grating 42 satisfies 0.8μm≤d≤2μm, and the inclination angle θ2 satisfies 19°≤θ2≤25°.

[0029] In a preferred embodiment, Figure 1 As shown, the distance between the fourth lens 43 and the fifth lens 44 is m1, and the distance between the fifth lens 44 and the sixth lens 45 is m2, which satisfies the following relationship: 0.34≤m2 / m1≤0.5.

[0030] In a preferred embodiment, Figure 1 As shown, the curvature radii of the fourth lens 43 are R1 and R2, the curvature radii of the fourth lens 44 are R3 and R4, and the curvature radii of the sixth lens 45 are R5 and R6, which satisfy the following relationship: 0.034≤R1=-R2=R3=-R4=R5=-R6≤0.08.

[0031] The present invention selects components based on the convergence and spectral characteristics of the optical system and optimizes the parameter design of the optical components. It can cover a wide spectral range of 400nm to 700nm and achieve high-quality optical imaging effects while ensuring miniaturization and lightweight.

[0032] It is particularly important to note that the present invention, through the design of the optical path between the converging lens group 2, the entrance slit 3 and the beam splitter group 4, as well as the design of the ratio between the optical focal length of the beam splitter group 4 and the optical focal length of the entire optical system, can further ensure the miniaturization of the overall detection system and achieve high-quality optical imaging effects over a wide spectral range of 400nm to 700nm.

[0033] The following provides a specific embodiment of the present invention and its performance effects for exemplary description:

[0034] See also Figure 1 In the material detection optical system based on Raman spectrometer, the optical power Φ of the material detection optical system is 0.1, the optical power Φ1 of the laser excitation group 1 is 0.03, and the optical system is composed of a plane reflector 11 and a first lens 12. The tilt angle θ1 of the plane reflector 11 is 45°, and the optical power Φ of the first lens 12 is 0.1. 12 is 0.03; the length (along the direction of the incident light axis) of the entire laser excitation group 1 (including the plane mirror 11, the first lens 12 and the component for fixing the plane mirror 11 and the first lens 12) is 40 mm. This design reduces the aberration of the system and obtains a lighter total weight than using a single-piece converging lens.

[0035] The focal length Φ2 of the converging lens group 2 is 0.025, and it is composed of a second lens 21, a third lens 22 and a filter 23. The focal length Φ2 of the second lens 21 is 0.025. 21 is 0.05, and the focal length of the third lens 22 is Φ 22 is 0.1; the length (along the direction of the incident light axis) of the entire converging lens group 2 (including the second lens 21, the second lens 22 and the filter 23, and the component for fixing the first lens 21 and the second lens 22) is 22 mm, the optical path L1 of the light from the sample through the converging lens group 2 to the incident slit 3 is 26 mm, and the optical path L2 of the light from the sample to the detector is 156 mm.

[0036] The incident slit 3 is located on the output optical axis of the converging lens assembly 2, 10 mm away from the filter 23. A slit is provided on the incident slit, intersecting with and perpendicular to the extended line of the incident optical axis. This slit allows only light reflected by the concave reflector 3 to pass through. The slit is 4.5 mm long and 0.01 mm wide, allowing light in the wavelength range of 400 nm to pass through.

[0037] The optical focal length Φ4 of the beam splitter group 4 is 0.05, and it is composed of a collimating lens 41, a diffraction grating 42, a fourth lens 43, a fifth lens 44, and a sixth lens 45. The optical focal length Φ4 of the collimating lens 41 is 0.05. 41 is 0.03, the grating constant of the diffraction grating 42 is 2 μm, the tilt angle θ2 is 19.5°, and the focal power Φ of the fourth lens 43 is 43 is 0.03, and the optical power Φ of the fifth lens 44 is 44 is 0.03, and the focal power Φ of the sixth lens 45 45 The length (along the incident optical axis) of the entire beamsplitter assembly 4 (comprising the collimating lens 41, diffraction grating 42, fourth lens 43, fifth lens 44, and sixth lens 45, as well as the assembly for securing these elements) is 132 mm. The spacing between the fourth lens 43 and the fifth lens 44 is 0.5 mm, and the spacing between the fifth lens 44 and the sixth lens 45 is 0.18 mm. The curvature radii R1 and R2 of the fourth lens 43, R3 and R4 of the fifth lens 44, and R5 and R6 of the sixth lens 45 are: R1 = -R2 = R3 = -R4 = R5 = -R6 = 0.05 mm.

[0038] The imaging effect of this specific embodiment can be seen in Figure 2 , Figure 2 The diagram shows the diffuse spots corresponding to the material detection optical system in this embodiment: at different lateral positions of the object plane (-0.1000mm, 0.000mm, -0.100mm) and corresponding image plane positions, visible light spots with wavelengths of 400nm (approximately purple light), 550nm (approximately green light), and 700nm (approximately red light) are gathered and imaged from bottom to top at the corresponding image plane according to their wavelengths. It can be seen that on the lateral scale, the distribution of all visible light spots is relatively concentrated, and the distribution of all visible light spots on the image plane is concentrated in the middle part of the image; the position and size of the diffuse spots vary slightly at different angles, but there is no obvious diffusion; from short wave to long wave, the distribution of the diffuse spots is highly concentrated; this shows that the optical system proposed in the present invention has high imaging accuracy for light of different wavelengths, good aberration control effect, high imaging stability, and can achieve good imaging quality over a wide spectrum.

[0039] Figure 3A schematic diagram of the modulation transfer function (MTF) of the material detection optical system of the present invention is shown. The dashed line at the top, which is close to a straight line, represents the diffraction limit, which is the theoretical maximum resolving power of the lens assembly. The other curves are schematic diagrams of the modulation transfer function (MTF) of the spectrophotometer optical system of the present invention at various field angles. It can be seen that these MTF curves are all close to the diffraction limit, and the closer they are to the diffraction limit, the higher the resolving power of the lens. The figure shows that the MTF of the spectrophotometer optical system proposed by the present invention is greater than 0.3 at a spatial frequency of 150 lp / mm across the entire field of view, demonstrating excellent resolving power.

[0040] Therefore, the material detection optical system based on Raman spectrometer provided by the present invention has a high system stability after optimizing the component design; by adopting the laser excitation-spectral detection dual module synchronous measurement, the stray light interference of the excitation light source can be effectively eliminated, and the reliability and accuracy of the measurement data can be improved. In addition, the optical system only uses a simple spherical mirror, has a simple structure and low cost, and can be widely promoted and used.

[0041] In addition, the material detection optical system based on the Raman spectrometer provided by the present invention can cover a wide spectral range of 400nm to 700nm, and can achieve high-quality optical imaging effects while ensuring miniaturization and lightweight.

[0042] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention is not limited to the embodiments described in the specific implementation methods. Any other implementation methods derived by those skilled in the art based on the technical solutions of the present invention also fall within the scope of protection of the present invention.

Claims

1. A material detection optical system based on Raman spectrometer, characterized in that: It includes: Arranged in sequence along the optical path are a laser excitation group (1) consisting of a plane reflector (11) and a first lens (12), a converging lens group (2) consisting of a second lens (21), a third lens (22) and a filter (23), an entrance slit (3), and a beam splitter group (4) consisting of a collimating lens (41), a diffraction grating (42), a fourth lens (43), a fifth lens (44) and a sixth lens (45); The laser excitation group (1) is used to converge the light beam emitted by the laser and incident on the sample surface, the converging mirror group (2) is used to filter out Rayleigh scattering, and the beam splitter group (4) is used to split the light beam incident from the incident slit; The excitation light beam passes through the laser excitation group (1), is converged by the plane reflector (11) and the first lens (12) in sequence, and is incident on the surface of the sample to be measured. The light beam reflected back from the sample surface is converged by the convergent lens group (2), filtered by the filter, and then incident on the incident slit (3). After being collimated and split by the spectroscope group (4), it is finally detected. The optical path of the light from the sample through the converging lens group (2) to the incident slit (3) is L1, and the optical path of the light from the sample to the detector is L, which satisfies the following relationship: 0.15≤L1 / L≤0.25; the focal length of the converging lens group (2) is Φ2, and the focal length of the material detection optical system is Φ, which satisfies the following relationship: 0.21≤Φ2 / Φ≤0.48; The optical focal length of the beam splitter group (4) is Φ4, and the optical focal length of the collimating lens (41) is Φ 41 , the optical power of the fourth lens (43) is Φ 43 , the optical power of the fifth lens (44) is Φ 44 , the optical power of the sixth lens (45) is Φ 45 , which satisfies the following relationship: 0.02≤Φ 43 =Φ 44 =Φ 45 ≤0.15,(Φ 43 +Φ 44 +Φ 45 ) / Φ4≤2, the optical power of the material detection optical system is Φ, which satisfies the following relationship: 0.36≤Φ4 / Φ≤0.52; The optical focal length of the laser excitation group (1) is Φ1, and the optical focal length of the material detection optical system is Φ, which satisfies the following relationship: 0.16≤Φ1 / Φ≤0.35; The optical power Φ of the second lens (21) 21 , the focal power Φ of the third lens (22) 22 , which satisfies the following relationship: 0.5≤Φ 21 / Φ 22 ≤1; The distance between the fourth lens (43) and the fifth lens (44) is m1, and the distance between the fifth lens (44) and the sixth lens (45) is m2, which satisfy the following relationship: 0.34≤m2 / m1≤0.5; The curvature radii of the fourth lens (43) are R1 and R2, the curvature radii of the fifth lens (44) are R3 and R4, and the curvature radii of the sixth lens (45) are R5 and R6, which satisfy the following relationship: 0.034≤R1=-R2=R3=-R4=R5=-R6≤0.

08.

2. The material detection optical system based on Raman spectrometer according to claim 1, characterized in that: The inclination angle θ1 of the plane reflector (11) satisfies 30°≤θ1≤50°.

3. The material detection optical system based on Raman spectrometer according to claim 1, characterized in that: The width of the incident slit (3) is w, which satisfies the following relationship: w<0.02 mm.

4. The material detection optical system based on Raman spectrometer according to claim 1, characterized in that: The grating constant d of the diffraction grating (42) satisfies 0.8 μm≤d≤2 μm, and the tilt angle θ2 satisfies 19°≤θ2≤25°.

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