Raman spectrometer

Abstract

The invention relates to the field of optics, in particular to a Raman spectrometer, and a laser light source of the Raman spectrometer is used for emitting laser beams. The laser beam is focused on the surface of a to-be-detected sample through the Raman probe and excites the to-be-detected sample to generate Raman scattering light, and the Raman scattering light can be collected through the Raman probe and output through the output optical fiber. The beam splitter prism is located on an output optical path of the output optical fiber. And the beam splitter prism is used for splitting the Raman scattering light into two vertical light beams. The first light beam of the two light beams passes through one interference arm and then returns to the beam splitter prism, and the second light beam passes through the other interference arm and then returns to the beam splitter prism. The interference arm comprises a blazed grating and a reflector, the blazed grating is located on a light path between the beam splitter prism and the reflector, light beams are subjected to primary dispersion through the blazed grating, incident to the reflector and reflected back to the blazed grating through the reflector to be subjected to secondary dispersion, and the light beams subjected to secondary dispersion can return to the beam splitter prism. Therefore, the spectral resolution of the Raman spectrometer can be improved.

Description

Technical Field

[0001] The present invention belongs to the field of optics, and particularly relates to a Raman spectrometer. Background Art

[0002] Raman scattering spectroscopy is a phenomenon of inelastic light scattering, which reflects the vibration, rotation and other low-frequency mode information of molecules or lattices. It was discovered by a research team led by the Indian physicist C.V. Raman in 1928. Fourier Raman spectrometers are a type of spectrometers specifically used to detect Raman spectroscopy signals. Due to their ability to effectively reduce the interference of fluorescence on Raman spectra, improve the signal-to-noise ratio, and achieve high-speed data acquisition, they have received extensive attention in the scientific community. The core of this type of instrument is a Michelson interferometer, which consists of a collimating mirror, a beam splitter, a compensating plate, a fixed plane mirror, and a moving plane mirror. Through the uniform reciprocating linear motion of the moving plane mirror, the incident Raman spectroscopy signal is modulated into interference fringes and received by a detector, and then the computer performs a Fourier transform on the interference fringes to demodulate the Raman spectroscopy signal. Since Fourier Raman spectrometers have moving parts, it is difficult to achieve spectral transient measurement, and a very high number of detector sampling points are required to restore the original interference fringes. To overcome the above disadvantages, by replacing the two aforementioned plane mirrors with gratings, the frequency of the interferogram is reduced, and the spectral curve is moved to near zero wavenumber, which can achieve higher spectral resolution with the same number of detector sampling points, and at the same time, there are no moving parts in the system, realizing spectral transient measurement.

[0003] With the rapid development of Raman spectroscopy technology, it is widely used in many fields such as chemical composition analysis, food detection, and mineral exploration. In order to be able to detect Raman spectroscopy signals more precisely and study the essence of substances in depth, researchers have higher and higher requirements for the spectral resolution of Raman spectrometers. Summary of the Invention

[0004] In view of this, the present invention aims to provide a Raman spectrometer that can improve the spectral resolution of the Raman spectrometer. To achieve the above object, the technical solution of the present invention is realized as follows: A Raman spectrometer, comprising: A laser light source for emitting a laser beam; A Raman probe, through which the laser beam is focused on the surface of the sample to be measured, and the Raman probe excites the sample to be measured to generate Raman scattered light, and the Raman scattered light can be collected by the Raman probe and output through an output optical fiber; A beam splitting prism located on the output optical path of the output optical fiber; the beam splitting prism is used to split the Raman scattered light into two perpendicular beams of light; Two interference arms, the first beam in the two beams of light returns to the beam splitter prism after passing through one interference arm, and the second beam of light returns to the beam splitter prism after passing through the other interference arm; the interference arm includes a blazed grating and a mirror, the blazed grating is located on the optical path between the beam splitter prism and the mirror, the beam of light is dispersed once by the blazed grating and is incident on the mirror, and is reflected back to the blazed grating by the mirror for secondary dispersion, and the beam of light after secondary dispersion will return to the beam splitter prism; A detector, the two beams of light return to the beam splitter prism for beam combination and are incident on the detector; the detector is used to capture multiple sets of interference fringes formed by the interference of the first beam of light and the second beam of light.

[0005] Further, it further includes a collimating mirror group, and the collimating mirror group is located on the optical path from the output optical fiber to the beam splitter prism, and is used to collimate the Raman scattered light into a parallel beam of light.

[0006] Further, the two interference arms include a first interference arm and a second interference arm, the first beam of light returns to the beam splitter prism after passing through the first interference arm; the second beam of light returns to the beam splitter prism after passing through the second interference arm; The first interference arm includes a first blazed grating and a first mirror, and the second interference arm includes a second blazed grating and a second mirror; the first blazed grating and the second blazed grating are symmetrically arranged with respect to the diagonal of the beam splitter prism.

[0007] Further, the distance between the surface of the beam splitter prism on the side close to the first blazed grating and the center of the first blazed grating is 100 mm to 120 mm.

[0008] Further, the angle between the normal of the first blazed grating and the optical axis of the collimating mirror group The formula is:

[0009] Among them, is the wavelength of the laser beam emitted by the laser light source, is the grating constant of the first blazed grating, is the angle between the incident light and the diffracted light of the first blazed grating.

[0010] Further, the distance between the center of the first mirror and the center of the first blazed grating in the first direction is and the distance in the second direction is ; the angle between the normal of the first mirror and the normal of the first blazed grating The formula is:

[0011] Among them, is the distance between the surface of the beam splitter prism on the side close to the first blazed grating and the center of the first blazed grating, is the wavelength of the laser beam emitted by the laser light source, is the grating constant of the first blazed grating, is the angle between the incident light and the diffracted light of the first blazed grating.

[0012] Furthermore, the distance between the surface of the beam splitting prism close to the second blazed grating and the center of the second blazed grating is 100 mm to 120 mm.

[0013] Furthermore, the angle between the grating plane of the second blazed grating and the optical axis of the collimating mirror group

[0014] wherein, is the wavelength of the laser beam emitted by the laser light source, is the grating constant of the second blazed grating, is the angle between the incident light and the diffracted light of the second blazed grating.

[0015] Furthermore, the distance between the center of the second reflector and the center of the second blazed grating in the first direction is and the distance in the second direction is ; the angle between the normal of the second reflector and the normal of the second blazed grating

[0016] wherein, is the distance between the surface of the beam splitting prism close to the second blazed grating and the center of the second blazed grating, is the wavelength of the laser beam emitted by the laser light source, is the grating constant of the second blazed grating, is the angle between the incident light and the diffracted light of the second blazed grating.

[0017] Furthermore, it further includes an imaging mirror group, and the imaging mirror group is located on the optical path from the beam splitting prism to the detector.

[0018] Compared with the prior art, the present invention can achieve the following beneficial effects: The Raman spectrometer according to the embodiment of the present invention includes two interference arms. The beam splitter prism is used to divide the Raman scattered light into two perpendicular beams of light. The first beam of light in the two beams of light returns to the beam splitter prism after passing through one interference arm, and the second beam of light returns to the beam splitter prism after passing through the other interference arm. The interference arm includes a blazed grating and a mirror. The beam of light is dispersed once by the blazed grating and is incident on the mirror, and is reflected back to the blazed grating by the mirror for secondary dispersion. In this way, the beam of light can be dispersed twice by the blazed grating in the interference arm, thereby improving the spectral resolution of the Raman spectrometer. Description of the Drawings

[0019] The drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 It is a schematic structural diagram of the Raman spectrometer according to the embodiment of the present invention.

[0020] Description of the Reference Numerals: 10. Raman spectrometer; 11. Laser light source; 12. Raman probe; 13. Beam splitter prism; 14. Interference arm; 15. Detector; 16. Input optical fiber; 17. Output optical fiber; 18. Blazed grating; 19. Mirror; 20. Collimating lens group; 21. Sample to be measured; 22. First interference arm; 23. Second interference arm; 24. First blazed grating; 25. First mirror; 26. Second blazed grating; 27. Second mirror; 28. Imaging lens group. Detailed Embodiments

[0021] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention. Similar elements in different embodiments are labeled with related similar element numbers. In the following embodiments, many details are described to make the present invention better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present invention are not shown or described in the specification, in order to avoid the core part of the present invention being overwhelmed by excessive description. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0022] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other to form various implementation manners. At the same time, the steps or actions in the method description can also be reordered or adjusted in an obvious manner by those skilled in the art. Therefore, the various sequences in the specification and drawings are only for clearly describing a certain embodiment and do not mean that they are the necessary sequences, unless it is stated that a certain sequence must be followed.

[0023] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the 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 should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0024] In the description of the present invention, it should be noted that, unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0025] The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0026] See Figure 1 As shown, an embodiment of the present invention provides a Raman spectrometer 10, and the Raman spectrometer 10 includes a laser light source 11, a Raman probe 12, a beam splitting prism 13, two interference arms 14, and a detector 15.

[0027] The laser light source 11 is used to emit a laser beam. In this embodiment, the laser light source 11 can be used to emit a laser beam with a wavelength of 532 nm. The laser light source 11 can be connected to the Raman probe 12 through the input optical fiber 16, and the laser beam can be transmitted to the Raman probe 12 through the input optical fiber 16. The laser beam is focused on the surface of the sample to be measured 21 through the Raman probe 12, and the Raman scattered light generated by the sample to be measured 21 is excited. The Raman scattered light can be collected by the Raman probe 12 and output through the output optical fiber 17.

[0028] The beam splitting prism 13 is located on the output optical path of the output optical fiber 17. The beam splitting prism 13 is used to split the Raman scattered light into two perpendicular beams. The first beam of the two beams returns to the beam splitting prism 13 after passing through an interference arm 14, and the second beam returns to the beam splitting prism 13 after passing through another interference arm 14. The light transmitted through the beam splitting prism 13 in the Raman scattered light is used as the first beam, which is incident on an interference arm 14 and then returns to the beam splitting prism 13. The light reflected by the beam splitting prism 13 in the Raman scattered light is used as the second beam, which is incident on another interference arm 14 and then returns to the beam splitting prism 13. The transmission-reflection ratio of the beam splitting prism 13 is 50 / 50. The interference arm 14 includes a blazed grating 18 and a mirror 19. Among them, the blazed grating 18 is a planar blazed grating. The mirror 19 is a planar mirror. The blazed grating 18 is located on the optical path between the beam splitting prism 13 and the mirror 19. The beam undergoes one dispersion through the blazed grating 18, is incident on the mirror 19, is reflected by the mirror 19 and returns to the blazed grating 18 for secondary dispersion, and the beam after secondary dispersion will return to the beam splitting prism 13. The two beams return to the beam splitting prism 13 for beam combination and are incident on the detector 15. The detector 15 is used to capture multiple groups of interference fringes formed by the interference of the first beam and the second beam. Among them, the detector 15 is a area array detector.

[0029] The Raman spectrometer 10 of the embodiment of the present invention includes two interference arms 14, and the beam splitting prism 13 is used to split the Raman scattered light into two perpendicular beams. The first beam of the two beams returns to the beam splitting prism 13 after passing through an interference arm 14, and the second beam returns to the beam splitting prism 13 after passing through another interference arm 14. The interference arm 14 includes a blazed grating 18 and a mirror 19. The beam undergoes one dispersion through the blazed grating 18 and is incident on the mirror 19, and is reflected by the mirror 19 and returns to the blazed grating 18 for secondary dispersion. In this way, the beam can undergo secondary dispersion through the blazed grating 18 in the interference arm 14, thereby improving the spectral resolution of the Raman spectrometer 10.

[0030] In one embodiment, the Raman spectrometer 10 further includes a collimating mirror group 20, which is located on the optical path from the output optical fiber 17 to the beam splitting prism 13 and is used to collimate the Raman scattered light into a parallel light beam. The collimating mirror group 20 is coaxially arranged with the beam splitting prism 13. The Raman scattered light is output through the output optical fiber 17 and incident on the collimating mirror group 20. The collimating mirror group 20 can collimate the Raman scattered light into a parallel light beam, and the collimated parallel Raman scattered light is incident on the beam splitting prism 13 and is split into two perpendicular light beams by the beam splitting prism 13.

[0031] In one embodiment, the two interference arms 14 include a first interference arm 22 and a second interference arm 23. The first light beam returns to the beam splitting prism 13 after passing through the first interference arm 22. The second light beam returns to the beam splitting prism 13 after passing through the second interference arm 23. The first interference arm 22 includes a first blazed grating 24 and a first reflector 25, and the second interference arm 23 includes a second blazed grating 26 and a second reflector 27. The first blazed grating 24 and the second blazed grating 26 are symmetrically arranged with respect to the diagonal of the beam splitting prism 13.

[0032] In one embodiment, the distance between the surface of the beam splitting prism 13 on the side close to the first blazed grating 24 and the center of the first blazed grating 24 is 100 mm to 120 mm. In this embodiment, the distance between the surface of the beam splitting prism 13 on the side close to the first blazed grating 24 and the center of the first blazed grating 24 is 100 mm.

[0033] In one embodiment, the included angle between the normal of the first blazed grating 24 and the optical axis of the collimating mirror group 20 is given by the formula:

[0034] where is the wavelength of the laser beam emitted by the laser light source 11, is the grating constant of the first blazed grating 24, is the included angle between the incident light and the diffracted light of the first blazed grating 24, and the included angle is 20° to 40°, that is, 20° < < 40°.

[0035] In this embodiment, the wavelength of the laser beam emitted by the laser light source 11 is 532 nm. The included angle between the incident light and the diffracted light of the first blazed grating 24 is 24°. The grating constant of the first blazed grating 24 is 3.3 μm. Thus, the included angle between the normal of the first blazed grating 24 and the optical axis of the collimating mirror group 20 is 16.68°.

[0036] In one embodiment, the distance between the center of the first reflector 25 and the center of the first blazed grating 24 in the first direction X is , and the distance in the second direction Y is . The angle between the normal of the first reflector 25 and the normal of the first blazed grating 24 is given by the formula:

[0037] where is the distance between the surface of the beam splitter prism 13 close to the first blazed grating 24 and the center of the first blazed grating 24, is the wavelength of the laser beam emitted by the laser light source 11, is the grating constant of the first blazed grating 24, is the angle between the incident light and the diffracted light of the first blazed grating 24.

[0038] In this embodiment, the first reflector 25 is located at the lower left side of the first blazed grating 24. The distance between the center of the first reflector 25 and the center of the first blazed grating 24 in the first direction X is 50 mm, and the distance in the second direction Y is 22.26 mm. The angle between the normal of the first reflector 25 and the normal of the first blazed grating 24 is 7.32°. In this way, the first beam of light can be dispersed once by the first blazed grating 24, and then incident on the first reflector 25. After being reflected by the first reflector 25, it returns to the first blazed grating 24 for secondary dispersion, and the beam of light after secondary dispersion returns to the beam splitter prism 13.

[0039] In one embodiment, the distance between the surface of the beam splitter prism 13 close to the second blazed grating 26 and the center of the second blazed grating 26 is 100 mm to 120 mm. In this embodiment, the distance between the surface of the beam splitter prism 13 close to the second blazed grating 26 and the center of the second blazed grating 26 is 100 mm.

[0040] In one embodiment, the angle between the grating plane of the second blazed grating 26 and the optical axis of the collimating lens group 20 is given by the formula:

[0041] where is the wavelength of the laser beam emitted by the laser light source 11, is the grating constant of the second blazed grating 26, is the angle between the incident light and the diffracted light of the second blazed grating 26.

[0042] In this embodiment, the wavelength of the laser beam emitted by the laser light source 11 is 532 nm. The angle between the incident light and the diffracted light of the second blazed grating 26 is 24°. The grating constant of the second blazed grating 26 is 3.3 μm. Thus, the angle between the grating plane of the second blazed grating 26 and the optical axis of the collimating lens group 20 is 16.68°.

[0043] In one embodiment, the distance between the center of the second reflector 27 and the center of the second blazed grating 26 in the first direction X is , and the distance in the second direction Y is . The angle between the normal of the second reflector 27 and the normal of the second blazed grating 26 is given by the formula:

[0044] where, is the distance between the surface of the beam splitting prism 13 close to the second blazed grating 26 and the center of the second blazed grating 26, is the wavelength of the laser beam emitted by the laser light source 11, is the grating constant of the second blazed grating 26, is the angle between the incident light and the diffracted light of the second blazed grating 26.

[0045] In this embodiment, the second reflector 27 is located at the lower right side of the second blazed grating 26. The distance between the center of the second reflector 27 and the center of the second blazed grating 26 in the first direction X is 22.26 mm, and the distance in the second direction Y is 50 mm. The angle between the normal of the second reflector 27 and the normal of the second blazed grating 26 is 7.32°. Thus, the second beam of light can be dispersed once by the second blazed grating 26, incident on the second reflector 27, reflected back by the second reflector 27 to the second blazed grating 26 for secondary dispersion, and the beam of light after secondary dispersion will return to the beam splitting prism 13.

[0046] In one embodiment, the Raman spectrometer 10 further includes an imaging lens group 28, and the imaging lens group 28 is located on the optical path from the beam splitting prism to the detector 15. The two beams of light return to the beam splitting prism 13 for beam combination, and after passing through the imaging lens group 28, are incident on the detector 15 to form an image on the detector 15. The detector 15 can output multiple sets of interference fringes. The multiple sets of interference fringes can be inverse-transformed through Fourier transform to obtain Raman spectral data.

[0047] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps recited in the disclosure of the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and no limitation is imposed herein.

[0048] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A Raman spectrometer, characterized in that, Comprising: A laser light source for emitting a laser beam; A Raman probe through which the laser beam is focused onto the surface of a sample to be measured, and the Raman probe excites the sample to be measured to generate Raman scattered light, and the Raman scattered light can be collected by the Raman probe and output through an output optical fiber; A beam splitting prism located on the optical path of the output light of the output optical fiber; the beam splitting prism is used to split the Raman scattered light into two perpendicular beams; Two interference arms, the first beam of the two beams returns to the beam splitting prism after passing through one of the interference arms, and the second beam returns to the beam splitting prism after passing through the other interference arm; the interference arm includes a blazed grating and a mirror, the blazed grating is located on the optical path between the beam splitting prism and the mirror, the beam undergoes first-order dispersion through the blazed grating and is incident on the mirror, and after being reflected by the mirror, it returns to the blazed grating for second-order dispersion, and the beam after second-order dispersion returns to the beam splitting prism; A detector, the two beams return to the beam splitting prism for beam combination and are incident on the detector; The detector is used to capture multiple sets of interference fringes formed by the interference of the first beam and the second beam.

2. The Raman spectrometer according to claim 1, wherein It further includes a collimating lens group located on the optical path from the output optical fiber to the beam splitting prism for collimating the Raman scattered light into a parallel beam.

3. The Raman spectrometer according to claim 2, characterized in that, The two interference arms include a first interference arm and a second interference arm, the first beam returns to the beam splitting prism after passing through the first interference arm; the second beam returns to the beam splitting prism after passing through the second interference arm; The first interference arm includes a first blazed grating and a first mirror, and the second interference arm includes a second blazed grating and a second mirror; the first blazed grating and the second blazed grating are symmetrically arranged with respect to the diagonal of the beam splitting prism.

4. The Raman spectrometer according to claim 3, characterized in that, The distance between the surface of the beam splitting prism near the first blazed grating and the center of the first blazed grating is 100 mm to 120 mm.

5. The Raman spectrometer according to claim 3, wherein, The included angle between the normal of the first blazed grating and the optical axis of the collimating mirror group is given by the formula: Among them, is the wavelength of the laser beam emitted by the laser light source, is the grating constant of the first blazed grating, is the angle between the incident light and the diffracted light of the first blazed grating.

6. The Raman spectrometer according to claim 3, characterized in that, The distance between the center of the first reflector and the center of the first blazed grating in the first direction is , and the distance in the second direction is ; the formula for the angle between the normal of the first reflector and the normal of the first blazed grating is: Wherein, is the distance between the surface of the beam splitting prism close to the first blazed grating and the center of the first blazed grating, is the wavelength of the laser beam emitted by the laser light source, is the grating constant of the first blazed grating, is the angle between the incident light and the diffracted light of the first blazed grating.

7. The Raman spectrometer according to claim 3, characterized in that, The distance between the surface of the beam splitting prism near the second blazed grating and the center of the second blazed grating is 100 mm to 120 mm.

8. The Raman spectrometer according to claim 3, wherein The included angle between the grating plane of the second blazed grating and the optical axis of the collimating mirror group is given by the formula: Wherein, is the wavelength of the laser beam emitted by the laser light source, is the grating constant of the second blazed grating, is the angle between the incident light and the diffracted light of the second blazed grating.

9. The Raman spectrometer according to claim 3, characterized in that, The distance between the center of the second reflector and the center of the second blazed grating in the first direction is , and the distance in the second direction is ; The formula for the angle between the normal of the second reflector and the normal of the second blazed grating is: Wherein, is the distance between the surface of the beam splitting prism close to the second blazed grating and the center of the second blazed grating, is the wavelength of the laser beam emitted by the laser light source, is the grating constant of the second blazed grating, is the angle between the incident light and the diffracted light of the second blazed grating.

10. The Raman spectrometer according to claim 1, wherein It further includes an imaging lens group located on the optical path from the beam splitting prism to the detector.

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