Material detection optical system based on Raman spectrometer

Abstract

The invention relates to a Raman spectrometer-based material detection optical system, which comprises a laser excitation group, a convergent lens group, an entrance slit and a spectroscope group, the laser excitation group comprises a plane mirror and a convergent lens, the convergent lens group comprises a first lens, a second lens and an optical filter, the entrance position of the spectroscope group is provided with the slit, and the entrance slit is provided with a second lens. The spectroscope group comprises a collimating lens, a diffraction grating, a third lens, a fourth lens and a fifth lens. The laser excitation group emits laser to a sample, and light reflected by the sample is converged by the convergent mirror group, then is split by the spectroscope group, and finally is detected by the detector. The material detection optical system based on the Raman spectrometer can realize wide spectral range application, and has the advantages of miniaturization and light weight.

Description

Technical Field

[0001] The present invention relates to the field of spectral analysis systems, and particularly 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, and is widely applied in multiple fields such as chemistry and materials, biomedicine, and environment and food. Due to the good monochromaticity and concentrated energy of laser, laser is usually used as the excitation light source. When the laser irradiates the sample, the incident light interacts with the sample, and the energy of some photons is absorbed or emitted due to the energy level changes caused by molecular vibration, rotation, or electronic transition, resulting in a change in the frequency of the scattered light. This frequency change is called Raman frequency shift, which reflects the information of the molecular structure and chemical bond. The Raman scattering spectrum usually contains information about the sample structure, composition, and chemical bond, and has high resolution and chemical specificity.

[0003] The structure of traditional Raman spectrometers is complex, difficult to calibrate, and has a high manufacturing cost, reducing the flexibility of the system and making it difficult to meet the requirements of modern applications for miniaturization and portability. Summary of the Invention

[0004] To solve the deficiencies of the existing technology, the present invention provides a material detection optical system based on a Raman spectrometer, which can achieve a wide spectral range covering 400 nm to 700 nm, and can achieve a high-quality optical imaging effect on the basis of ensuring miniaturization and light weight.

[0005] The present invention specifically relates to a material detection optical system based on a Raman spectrometer, which includes: a laser excitation group (1) composed of a plane mirror (11) and a first lens (12) arranged in sequence along the optical path, a converging lens group (2) composed of a second lens (21), a third lens (22) and a filter (23), an entrance 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 the beam emitted by the laser and incident on the surface of the sample, the converging lens group (2) is used to filter out Rayleigh scattering, and the spectroscope group (4) is used to split the beam incident on the entrance slit; the excitation beam passes through the laser excitation group (1), and after being converged in sequence by the plane mirror (11) and the first lens (12), it is incident on the surface of the sample to be measured. The beam reflected back from the surface of the sample is converged by the converging lens group (2), and after being filtered by the filter, it is incident on the entrance slit (3). After being collimated and split by the spectroscope group (4), it is finally detected; wherein, the optical path of the light from the sample through the converging lens group (2) to the entrance slit (3) is L1, and the optical path of the light from the sample incident on the detector is L, and they satisfy the following relationship: 0.15 ≤ L1 / L ≤ 0.25; the optical power of the converging lens group (2) is Φ2, and the optical power of the material detection optical system is Φ, and they satisfy the following relationship: 0.21 ≤ Φ2 / Φ ≤ 0.48 Further, the tilt angle θ1 of the plane mirror (11) satisfies 30° ≤ θ1 ≤ 50°, the optical power of the laser excitation group (1) is Φ1, and the optical power of the material detection optical system is Φ, and they satisfy the following relationship: 0.16 ≤ Φ1 / Φ ≤ 0.35.

[0006] Further, the optical power Φ 21 of the second lens (21) and the optical power Φ 22 of the third lens (22) satisfy the following relationship: 0.5 ≤ Φ 21 / Φ 22 ≤ 1.

[0007] Further, the width w of the entrance slit (3) satisfies w < 0.02 mm.

[0008] Further, the optical power of the spectroscope group (4) is Φ4, the optical power 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 , and the optical power of the sixth lens (45) is Φ 45 , and they satisfy the following relationship: 0.02 ≤ Φ 43 = Φ 44 = Φ45 ≤0.15, (Φ 43 + Φ 44 + Φ 45 ) / Φ4 ≤ 2, where the optical power of the material detection optical system is Φ, and it satisfies the following relationship: 0.36 ≤ Φ4 / Φ ≤ 0.52. 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°.

[0009] 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, and they satisfy the following relationship: 0.34 ≤ m2 / m1 ≤ 0.5.

[0010] Furthermore, the radii of curvature of the fourth lens (43) are R1 and R2 respectively, the radii of curvature of the fifth lens (44) are R3 and R4 respectively, and the radii of curvature of the sixth lens (45) are R5 and R6 respectively, and they satisfy the following relationship: 0.034 ≤ R1 = -R2 = R3 = -R4 = R5 = -R6 ≤ 0.08.

[0011] The material detection optical system based on a Raman spectrometer provided by the present invention has high system stability after optimizing the component design; by adopting the synchronous measurement of the laser excitation - spectral detection dual module, the stray light interference of the excitation light source can be effectively eliminated, the reliability and accuracy of the measurement data can be improved, and the optical system only uses simple spherical mirrors, with a simple structure and low cost, and can be widely promoted and used. The detection optical path structure of the present invention is simple, only using the simplest spherical mirrors, and the simplified optical path makes the instrument smaller in volume, suitable for laboratories or on - site rapid detection with limited space.

[0012] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. Brief Description of the Drawings

[0013] The accompanying drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present invention, and are used together with the specification to explain the principles of the present invention.

[0014] Figure 1 Shows the structure and optical path schematic diagram of the spectrophotometer optical system according to an embodiment of the present invention; Figure 2 Shows the display schematic diagram of the spot diagram corresponding to the spectrophotometer optical system according to an embodiment of the present invention; Figure 3 Shows the curve schematic diagram of the modulation transfer function corresponding to the spectrophotometer optical system according to an embodiment of the present invention.

[0015] Reference numerals: 1 - laser excitation group, 11 - plane mirror, 12 - first lens, 2 - converging lens group, 21 - second lens, 22 - third lens, 23 - filter, 3 - entrance slit, 4 - spectroscope group, 41 - collimating lens, 42 - diffraction grating, 43 - fourth lens, 44 - fifth lens, 45 - sixth lens. Detailed implementation

[0016] The present invention will be further described in detail below with reference to the accompanying drawings: The described embodiments are only a 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 protection scope of the present invention.

[0017] It should be noted that in the present invention, the unit of optical power is mm, the unit of radius of curvature is mm, and the unit of decentration is mm.

[0018] In the embodiments disclosed in the present invention, in the order of the optical path, a material detection optical system based on a photoluminescence spectrometer includes: a laser excitation group 1 composed of a plane mirror 11 and a first lens 12 arranged in sequence along the optical path, a converging lens group 2 composed of a second lens 21 and a third lens 22, an entrance 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.

[0019] 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 Rayleigh scattering through the filter 23; the entrance slit 3 is arranged on the exit optical axis of the converging lens group 2, and its function can improve the spectral resolution, suppress stray light, and improve the signal-to-noise ratio; the spectroscope group 4 is arranged on the other side of the entrance slit 3 and is used for spectral splitting of the system.

[0020] The excitation light beam passes through the laser excitation group 1, is sequentially converged by the plane mirror 11 and the first lens 12, and then enters 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 through the filter 23, and then enters the entrance slit 3. After being collimated and split by the spectroscope group 4, it is finally detected.

[0021] In one embodiment, the optical path from the sample through the converging lens group 2 to the entrance slit 3 is L1, and the optical path from the sample to the detector is L, which satisfies the following relationship: 0.15 ≤ L1 / L ≤ 0.25; the optical power of the converging lens group 2 is Φ2, and the optical power of the material detection optical system is Φ, which satisfies the following relationship: 0.21 ≤ Φ2 / Φ ≤ 0.48.

[0022] In a preferred embodiment, the tilt angle θ1 of the planar mirror 11 satisfies 30° ≤ θ1 ≤ 50°, the optical power of the laser excitation group 1 is Φ1, and the optical power of the material detection optical system is Φ, and they satisfy the following relationship: 0.16 ≤ Φ1 / Φ ≤ 0.35.

[0023] In a preferred embodiment, as Figure 1 shown, the optical power Φ 21 of the second lens 21 and the optical power Φ 22 of the third lens 22 satisfy the following relationship: 0.5 ≤ Φ 21 / Φ 22 ≤ 1.

[0024] In a preferred embodiment, as Figure 1 shown, the width w of the incident slit 3 satisfies w < 0.02 mm.

[0025] In a preferred embodiment, as Figure 1 shown, the optical power of the beam splitter group 4 is Φ4, the optical power 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 , and they satisfy 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, and they satisfy the following relationship: 0.36 ≤ Φ4 / Φ ≤ 0.52. 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°.

[0026] In a preferred embodiment, as Figure 1 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, and they satisfy the following relationship: 0.34 ≤ m2 / m1 ≤ 0.5.

[0027] In a preferred embodiment, as Figure 1 shown, the radii of curvature of the fourth lens 43 are R1 and R2 respectively, the radii of curvature of the fourth lens 44 are R3 and R4 respectively, and the radii of curvature of the sixth lens 45 are R5 and R6 respectively, and they satisfy the following relationship: 0.034 ≤ R1 = -R2 = R3 = -R4 = R5 = -R6 ≤ 0.08.

[0028] By selecting components through the converging and spectral splitting characteristics of the optical system and optimizing the parameter design of the optical assembly, the present invention can cover a wide spectral range from 400 nm to 700 nm, and can achieve high-quality optical imaging effects on the basis of ensuring miniaturization and light weight.

[0029] It should be particularly noted that through the design of the optical path between the converging lens group 2, the incident slit 3 and the spectral splitting lens group 4, and the ratio design between the optical power of the spectral splitting lens group 4 and the optical power of the entire optical system, the miniaturization of the overall detection system can be further ensured, and high-quality optical imaging effects can be achieved in the wide spectral range from 400 nm to 700 nm.

[0030] The following provides a specific embodiment of the present invention and its performance effects for exemplary illustration: See Figure 1 , in the material detection optical system based on a 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, which consists of a plane mirror 11 and a first lens 12, the tilt angle θ1 of the plane mirror 11 is 45°, and the optical power Φ 12 of the first lens 12 is 0.03; the length (along the incident optical axis direction) of the entire laser excitation group 1 (including the plane mirror 11, the first lens 12 and the components for fixedly connecting the plane mirror 11 and the first lens 12) is 40 mm, this design reduces the aberration of the system and obtains a total weight lighter than that using a single-piece converging lens.

[0031] The optical power Φ2 of the converging lens group 2 is 0.025, which consists of a second lens 21, a third lens 22 and a filter 23, the optical power Φ 21 of the second lens 21 is 0.05, and the optical power Φ 22 of the third lens 22 is 0.1; the length (along the incident optical axis direction) of the entire converging lens group 2 (including the second lens 21, the second lens 22, the filter 23 and the components for fixedly connecting the first lens 21 and the second lens 22) is 22 mm, the optical path L1 of the light from the sample passing 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 incident on the detector is 156 mm.

[0032] The incident slit 3 is located on the exit optical axis of the converging lens group 2, at a distance of 10 mm from the filter 23, and there is a slit on it that intersects and is perpendicular to the extension line of the incident optical axis, allowing only the light reflected by the concave mirror 3 to pass through, and the length of the slit is 4.5 mm and the width is 0.01 mm to allow the light within the wavelength range of 400 nm - 700 nm to pass through.

[0033] The optical power Φ4 of the spectroscope group 4 is 0.05, which 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 power Φ 41 of the collimating lens 41 is 0.03, the grating constant of the diffraction grating 42 is 2 μm, the tilt angle θ2 is 19.5°, and the optical power Φ 43 of the fourth lens 43 is 0.03, the optical power Φ 44 of the fifth lens 44 is 0.03, and the optical power Φ 45 of the sixth lens 45 is 0.03; the overall length (along the direction of the incident optical axis) of the entire spectroscope group 4 (including the collimating lens 41, the diffraction grating 42, the fourth lens 43, the fifth lens 44, and the sixth lens 45, as well as the components for fixedly connecting the collimating lens 41, the diffraction grating 42, the fourth lens 43, the fifth lens 44, and the sixth lens 45) is 132 mm. The distance between the fourth lens 43 and the fifth lens 44 is 0.5, and the distance between the fifth lens 44 and the sixth lens 45 is 0.18. The radius of curvature R1 and R2 of the fourth lens 43, the radius of curvature R3 and R4 of the fifth lens 44, and the radius of curvature R5 and R6 of the sixth lens 45, where R1 = -R2 = R3 = -R4 = R5 = -R6 = 0.05 mm.

[0034] For the imaging effect of this specific embodiment, refer to Figure 2 , Figure 2 which shows the blur spot corresponding to the optical system of the spectrophotometer in this embodiment: at different lateral positions of the object plane (-0.1000 mm, 0.000 mm, -0.100 mm) and corresponding image plane positions, visible light spots with wavelengths of 400 nm (approximately purple light), 550 nm (approximately green light), and 700 nm (approximately red light) are imaged by wavelength from bottom to top at the corresponding image plane. It can be seen that in the lateral scale, the distributions of all visible light spots are relatively concentrated, and the distributions of all visible light spots on the image plane are concentrated in the middle part of the image; at different angles, the positions and sizes of the blur spots change slightly, but there is no obvious diffusion; within the range from short wavelength to long wavelength, the distribution of the blur spots is highly concentrated; indicating that the optical system proposed by the present invention has high imaging accuracy for light rays of different wavelengths, good aberration control effect, high imaging stability, and can achieve good imaging quality within a broad spectrum range.

[0035] Figure 3The figure shows a schematic curve of the modulation transfer function of the optical system of the spectrophotometer of the present invention. The dotted line at the top and close to the straight line in the figure represents the diffraction limit, which is the theoretically maximum resolution ability of the lens assembly. The other curves are schematic curves of the modulation transfer function of the optical system of the spectrophotometer of the present invention at multiple field angles. It can be seen that these curves of the modulation transfer function are all close to the diffraction limit, and the closer to the diffraction limit, the higher the resolution ability of the lens. It can be seen from the figure that the MTF of the optical system of the spectrophotometer proposed by the present invention at a spatial frequency of 150 lp / mm in the full field of view is greater than 0.3, having excellent resolution ability.

[0036] Therefore, the material detection optical system based on the Raman spectrometer provided by the present invention has high system stability after optimizing the component design; by adopting the synchronous measurement of the laser excitation-spectral detection dual module, the stray light interference of the excitation light source can be effectively eliminated, the reliability and accuracy of the measurement data can be improved, and the optical system only uses simple spherical mirrors, with a simple structure and low cost, and can be widely promoted and used.

[0037] In addition, the material detection optical system based on the Raman spectrometer provided by the present invention can cover a wide spectral range from 400 nm to 700 nm, and can achieve high-quality optical imaging effects on the basis of ensuring miniaturization and light weight.

[0038] 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 embodiments. Any other embodiments obtained by those skilled in the art according to the technical solutions of the present invention also belong to the scope of protection of the present invention.

Claims

1. A material detection optical system based on Raman spectrometer, characterized in that: It includes: A laser excitation group (1) composed of a plane reflector (11) and a first lens (12), a converging lens group (2) composed of a second lens (21), a third lens (22) and a filter (23), an entrance slit (3), and a beam splitter 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) are arranged in sequence along the optical path; The laser excitation group (1) is used to converge the light beam emitted by the laser and make it 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 mirror group (2), filtered by the filter, and then incident on the incident slit (3). After being collimated and split by the beam splitter group (4), detection is finally performed. 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.

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°, the focal length of the laser excitation group (1) is Φ1, and the focal length of the material detection optical system is Φ, which satisfies the following relationship: 0.16≤Φ1 / Φ≤0.

35.

3. The material detection optical system based on Raman spectrometer according to claim 1, characterized in that: 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.

4. 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.

5. The material detection optical system based on Raman spectrometer according to claim 1, characterized in that: The focal length of the beam splitter group (4) is Φ4, and the 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 focal 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°.

6. The material detection optical system based on Raman spectrometer according to claim 5, characterized in that: 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.

7. The material detection optical system based on Raman spectrometer according to claim 6, characterized in that: The curvature radii of the fourth lens (43) are R1 and R2, respectively; the curvature radii of the fifth lens (44) are R3 and R4, respectively; and the curvature radii of the sixth lens (45) are R5 and R6, respectively, which satisfy the following relationship: 0.034≤R1=- R2=R3=- R4= R5=- R6≤0.08.

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