A dual-wheel N-point excited Raman scattering light reverse collection device

Abstract

This invention relates to a dual-wheel N-point excited Raman scattering light reverse collection device, comprising a laser, a collimating lens, a converging lens, and a spectrometer, as well as an N-point excitation lens assembly and two parallel short-reflection long-pass optical elements. The laser beam passes through the two short-reflection long-pass optical elements and then enters the N-point excitation lens assembly in parallel. The N-point excitation lens assembly is used to converge the laser beam multiple times to generate multiple excitation points, thereby exciting Raman scattering light and collecting the reverse Raman scattering light at each excitation point, which propagates towards the front end of the optical path. This invention improves laser power utilization several times through dual-wheel multi-point excitation, while also possessing the function of reverse Raman scattering light transmission and collection, thereby significantly increasing the sensitivity of the Raman spectrometer and reducing laser power consumption. All main optical elements are linearly arranged, offering advantages such as convenient optical path adjustment, simple manufacturing process, and low cost, facilitating widespread use.

Description

Technical Field

[0001] This invention relates to the field of Raman detection technology, specifically to a dual-wheel N-point excited Raman scattering light reverse collection device. Background Technology

[0002] The Raman probe, as a fundamental detection component of a Raman spectrometer, is used to collect Raman scattered light. Lasers, due to their high energy density, are an essential light source for Raman scattering. However, Raman scattered light excited by an unfocused laser beam remains very weak, posing a significant challenge to its detection. Therefore, it is necessary to converge or focus the laser beam to obtain a higher intensity and more easily measurable Raman scattered light signal. For example, when the effective spot diameter of the incident laser is 2 mm, and the spot diameter is reduced to 0.1 mm after convergence, the light intensity at the convergence point is four hundred times that before convergence, thus increasing the Raman scattering signal intensity by 399 times.

[0003] In many detection scenarios, the limitation of optical collection space is a prominent engineering challenge. For example, in in-situ gas detection in industrial flues, Raman probes need to be inserted into the gas flow channel through a single flange interface. The laser is emitted forward into the open space to excite gas molecules flowing through the front of the probe. At this time, the front is a high-temperature, high-speed flue gas field, making it impossible to place any collection optical elements. In such single-window gas detection scenarios, reverse collection becomes the only feasible method for Raman signal acquisition.

[0004] Furthermore, most existing Raman probes on the market employ a single-point excitation mode, meaning the laser excites Raman scattering light only at a single convergence point. A significant amount of unused laser energy continues to propagate along the optical path after passing through this convergence point, resulting in low laser power utilization. Since gas Raman signals are already extremely weak, this further waste of laser energy severely limits the sensitivity and detection limit of gas detection. To address this issue, patent CN117277048A proposes a method and signal excitation device for multi-laser beam confocal excitation of Raman spectroscopy. This method uses multiple low-power lasers to emit multiple laser beams, which are then focused and excited in the same area by an optical system to generate a Raman signal. This low-power laser confocalization creates a high-power spot in the test area, enhancing the Raman signal intensity. However, this method requires multiple lasers, significantly increasing the overall system cost and hindering its large-scale application in gas detection.

[0005] Furthermore, the patent with authorization announcement number CN207850923U proposes a light scattering confocal excitation and collection system, which repeatedly reflects the excitation light source through several optical devices to the same focal point to improve the utilization efficiency of the excitation light source. However, the precision debugging of each optical device in this system is extremely difficult, facing high manufacturing process barriers, and the optical loss during multiple reflections cannot be ignored, thus limiting its practicality in the pursuit of miniaturization and low cost of gas detection systems.

[0006] In summary, in the reverse collection scenario of single-window gas detection, how to double the laser utilization rate and significantly improve the intensity of the reverse-collected Raman scattered light signal under the dual disadvantages of extremely weak gas Raman signal and only reverse collection, without increasing the laser power, is a technical problem that urgently needs to be solved. Summary of the Invention

[0007] To overcome the shortcomings of traditional single-point excitation lasers in single-window gas detection reverse collection scenarios, such as low utilization rate, waste of residual light energy, weak Raman signal intensity, and limited detection performance, as well as the high cost, difficult debugging, high optical loss, and poor practicality of existing improved solutions, this invention provides a dual-wheel N-point excitation Raman scattering light reverse collection device.

[0008] The technical solution of this invention is as follows: A dual-wheel N-point excited Raman scattering light reverse collection device includes a laser input component, a first short-reflection long-pass optical element or a total reflection mirror, a second short-reflection long-pass optical element parallel to the first short-reflection long-pass optical element, an N-point excitation lens assembly, a third short-reflection long-pass optical element, and a Raman scattering light receiving component; the upper surface normals of the first and second short-reflection long-pass optical elements are at 45° to the horizontal axis; the third short-reflection long-pass optical element is perpendicular to the lens central axis of the N-point excitation lens assembly, and its surface normal is at 0° to the horizontal axis; the forward laser light from the laser input component passes sequentially through the first short-reflection long-pass optical element. The element or total reflection mirror and the second short-reflection long-pass optical element are input to the N-point excitation lens assembly; the N-point excitation lens assembly includes multiple convex lenses arranged coaxially, used to receive the forward laser and converge it multiple times on the coaxial line to form N excitation points to generate the first round of reverse Raman scattered light, where N is a positive integer greater than 1; the N-point excitation lens assembly is also used to receive the reverse laser reflected by the third short-reflection long-pass optical element and converge it multiple times on the coaxial line to form N excitation points to generate the second round of reverse Raman scattered light; the reverse Raman scattered light generated by the dual excitation is collected by the convex lenses and transmitted to the Raman scattered light receiving assembly.

[0009] It should be noted that the front end of an optical element refers to its input end, and the rear end refers to its output end. Reverse Raman scattering includes backscattering from the forward-propagating laser and forward Raman scattering from the reverse-propagating laser. Forward Raman scattering refers to the direction in which the excitation laser propagates, and backward Raman scattering refers to the direction in which the excitation laser propagates. The forward-propagating laser comes from the laser input component, and the reverse-propagating laser comes from the laser reflected back by the third short-reflection long-pass optical element.

[0010] As a preferred embodiment of the present invention, the laser input component includes a laser, a collimating lens, and a narrow-bandpass filter. The laser is used to emit a laser source, the collimating lens is used to collimate the laser, and the narrow-bandpass filter is used to filter out extraneous spectral lines in the laser.

[0011] As a preferred embodiment of the present invention, the Raman scattering light receiving assembly includes a fourth short-reflection long-pass optical element, a converging lens, and a spectrometer. The fourth short-reflection long-pass optical element has a surface normal at 0° to the horizontal axis and is used to block excess laser light from entering the spectrometer. The converging lens is used to converge the reverse Raman scattered light and transmit it to the spectrometer.

[0012] As a preferred embodiment of the present invention, multiple convex lenses arranged coaxially form N groups of confocal lenses. In each group of confocal lenses, the two convex lenses are confocal, and the common focal point is the excitation point. The two confocal convex lenses have equal focal lengths, and the distance between the two convex lenses is equal to the sum of their focal lengths.

[0013] Furthermore, during the initial excitation process, the N sets of confocal lenses have convex lenses at odd-numbered positions used to converge the forward laser from the laser input component to generate the excitation point; convex lenses at even-numbered positions are used to collimate and transmit the laser; and convex lenses at odd-numbered positions are also used to collect and transmit the reverse Raman scattered light. During the secondary excitation process, the N sets of confocal lenses have convex lenses at even-numbered positions used to converge the reverse laser from the third short-reflector long-pass optical element to generate the excitation point; and convex lenses at odd-numbered positions are used to collimate and transmit the laser, and also to collect and transmit the reverse Raman scattered light.

[0014] In a preferred embodiment of the present invention, in the N-point excitation lens assembly, the distance between any two adjacent convex lenses is greater than the sum of the focal lengths of the two convex lenses, and the converging image point of the preceding convex lens is used as the object point of the following convex lens, so that the first convex lens is used to converge the laser to form an excitation point, and the subsequent multiple convex lenses are used to re-convex the light transmitted from the excitation point in front of them to form a new excitation point, but the last convex lens in the N-point excitation lens assembly is used to collimate the light.

[0015] Furthermore, the ratio of the focal lengths of any two adjacent convex lenses is between 0.2 and 5.

[0016] Preferably, the focal lengths of the multiple convex lenses arranged coaxially are equal, all being f.

[0017] Preferably, the distance between the first convex lens and the second convex lens, and the distance between the last convex lens and the penultimate convex lens are both equal to 3f, and among the multiple convex lenses from the second convex lens to the penultimate convex lens, the distance between two adjacent convex lenses is equal to 4f.

[0018] Furthermore, during the initial excitation process, the first convex lens of the N-point excitation lens assembly is used to converge the forward laser from the laser input component to generate the excitation point and to collect and transmit the forward and reverse Raman scattered light generated by the excitation point at the rear end. The middle convex lenses are used to converge the laser from the previous convex lens and simultaneously collect and transmit the forward and reverse Raman scattered light generated by the excitation point at the rear end. The last convex lens is used to collimate and transmit the forward laser to the third short-reflection long-pass optical element to achieve laser reflection. During the secondary excitation process, the last to the second convex lenses of the N-point excitation lens assembly are used to converge the reverse laser from the third short-reflection long-pass optical element to generate the excitation point. Except for the last convex lens, the remaining convex lenses are used to collect and transmit the forward and reverse Raman scattered light generated by the excitation point at the rear end.

[0019] As a preferred embodiment of the present invention, both the first short-wavelength anti-long-wavelength optical element and the second short-wavelength anti-long-wavelength optical element are short-wavelength anti-long-wavelength filters or short-wavelength anti-long-wavelength dichroic mirrors.

[0020] As a preferred embodiment of the present invention, both the third short-reflection long-pass optical element and the fourth short-reflection long-pass optical element are 0° short-reflection long-pass filters or 0° short-reflection long-pass dichroic mirrors.

[0021] As a preferred embodiment of the present invention, the convex lens used to collect and transmit reverse Raman scattered light in the N-point excitation lens assembly is an ultra-wide-angle lens.

[0022] According to the above-described solution, the beneficial effects of this invention are as follows: This invention adds an N-point excitation lens assembly to the optical path. This assembly is used to converge the laser multiple times, generating multiple excitation points. Each excitation point emits strong Raman scattered light. Furthermore, a third short-reflection long-pass optical element located at the rear end of the N-point excitation lens assembly reverses the laser's transmission direction, and the light is then re-converged within the N-point excitation lens assembly to form N excitation points, thus achieving a second round of Raman scattering excitation. The N-point excitation lens assembly also collects the reverse Raman scattered light from each excitation point during the dual-round excitation and propagates it sequentially to the front end of the optical path to the port of the spectrometer receiver.

[0023] In reverse-collection scenarios for single-window gas detection, this device utilizes dual-excitation technology to reflect the laser light emitted after passing through the optical excitation path back, allowing it to re-excite gas molecules through N excitation points in the reverse direction for a second round of Raman excitation. The backscattered Raman light excited by the first round of forward laser light at N excitation points and the forward scattered Raman light excited by the second round of reverse laser light at N excitation points both propagate in opposite directions, thus both can be received by the reverse-collection system. This achieves a significant increase in the intensity of the gas reverse Raman scattered light signal without adding any optical window. This has significant practical value for gas detection scenarios such as in-situ flue gas detection and headspace analysis of storage tanks, where only reverse collection is possible.

[0024] Specifically, ignoring lens attenuation, the laser power utilization rate increases by 2 times for each additional focusing point; with the input laser power remaining constant, the Raman scattered light intensity increases by 2 times for each additional focusing point; compared to the traditional single-excitation-point unidirectional Raman scattering collection method, the Raman scattered light collected by the device of this invention is increased by (2N-1) times.

[0025] Therefore, in the reverse collection scenario of single-window gas detection, the device of this invention doubles the laser utilization rate without increasing the laser power through dual-wheel excitation technology, significantly improving the signal intensity of reverse Raman scattered light under the strict constraint of only one optical channel. With the same laser incident power, it can increase the sensitivity of the Raman spectrometer several times, or reduce the laser power consumption several times while keeping the spectrometer sensitivity unchanged. Furthermore, the N-point excitation lens assembly is linearly arranged, offering advantages such as convenient optical path adjustment, simple manufacturing process, and cost savings, facilitating widespread application. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the optical path structure of the N-point excitation lens assembly in Example 1; Figure 4 This is a schematic diagram of the structure of Embodiment 3 of the present invention; Figure 5 This is a schematic diagram of the optical path structure of the N-point excitation lens assembly in Example 3; Figure 6 This is a schematic diagram of the structure of Example 4; Figure 7 This is a schematic diagram of the structure of Example 5.

[0027] In the diagram, 1 is the laser; 2 is the collimating lens; 3 is the narrow-bandpass filter; 41 is the first short-reflection long-pass optical element; 42 is the second short-reflection long-pass optical element; 43 is the total reflection mirror; 5 is the N-point excitation lens assembly; 51 is the convex lens A; 52 is the convex lens B; 53 is the convex lens C; 54 is the convex lens D; 55 is the convex lens E; 56 is the convex lens F; 57 is the convex lens G; 58 is the convex lens H; 61 is the third short-reflection long-pass optical element; 62 is the fourth short-reflection long-pass optical element; 7 is the converging lens; and 8 is the spectrometer receiver. Detailed Implementation

[0028] To better understand the purpose, technical solution, and technical effects of this invention, the invention will be further explained and described below in conjunction with the accompanying drawings and embodiments. It should be noted that similar reference numerals and letters in the following drawings indicate similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. It is also stated that the embodiments described below are only for explaining this invention and are not intended to limit this invention.

[0029] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intermediate component. When a component is referred to as "connected to" another component, it can be directly connected to the other component or there may be an intermediate component.

[0030] The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product is usually placed when in use, or the orientation or positional relationship in which a person skilled in the art would normally understand it, or the orientation or positional relationship in which the product is usually placed when in use. It is only for the purpose of facilitating the description of this application and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0031] The terms “first,” “second,” “third,” and “fourth” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or specifying the number of technical features. “Multiple” and “several” mean two or more, unless otherwise explicitly specified. Example 1

[0032] like Figure 1 and Figure 3As shown, a dual-wheel N-point excited Raman scattering light reverse collection device includes a laser input component, a first short-reflection long-pass optical element 41 and a second short-reflection long-pass optical element 42 arranged in parallel, an N-point excitation lens component 5, a third short-reflection long-pass optical element 61, and a Raman scattering light receiving component. The laser input component includes a laser 1, a collimating lens 2, and a narrow-bandpass filter 3. The laser 1 emits a high-energy-density laser beam, providing the necessary light source conditions for Raman scattering. The collimating lens 2 collimates the laser beam, forming a collimated beam that propagates towards the rear end of the optical path of the device system. The narrow-bandpass filter 3 filters out redundant spectral lines in the laser beam. Redundant spectral lines refer to spectral lines outside the desired wavelength range, thereby reducing interference from redundant spectral lines in the laser 1 to the device. The first short-wavelength-pass optical element 41 and the second short-wavelength-pass optical element 42 are both short-wavelength-pass filters or short-wavelength-pass dichroic mirrors, and the normal of the upper surface of the short-wavelength-pass filter or short-wavelength-pass dichroic mirror is at 45° to the horizontal axis. The first short-wavelength-pass optical element 41 and the second short-wavelength-pass optical element 42 are used to reflect the positive laser emitted by the laser 1 so as to input the laser into the N-point excitation lens assembly 5.

[0033] The Raman scattering light receiving assembly includes a fourth short-reflection long-pass optical element 62, a converging lens 7, and a spectrometer 8. The fourth short-reflection long-pass optical element 62 is used to block excess laser light from entering the spectrometer 8, and the surface normal of the fourth short-reflection long-pass optical element 62 forms a 0° angle with the horizontal axis. The converging lens 7 is used to converge, collect, and transmit the reverse Raman scattered light propagating from multiple sets of confocal lenses to the spectrometer 8, thereby improving the coupling efficiency of the Raman scattered light to the spectrometer 8. The spectrometer 8 is used to receive the reverse Raman scattered light and form a Raman spectrum based on the intensity distribution of the Raman scattered light. This Raman spectrum can show intensity peaks at different wavelengths, and the intensity peaks correspond to different vibrational modes of molecules in the sample, thereby determining the chemical composition and structural characteristics of the sample.

[0034] The N-point excitation lens assembly 5 includes at least two sets of confocal lens groups, with all convex lenses in the multiple sets of confocal lens groups arranged coaxially. Each confocal lens group consists of two coaxial convex lenses with the same focal length, and the distance between the two lenses is equal to the sum of their focal lengths. A focal point is formed between the two convex lenses, which is the excitation point for Raman scattering light, thereby achieving laser focusing at the focal point and generating strong Raman scattering light.

[0035] The detailed working principle of this embodiment is as follows: Laser 1 emits laser light, which is collimated by collimating lens 2 to form a collimated laser beam. The beam first passes through narrow-bandpass filter 3 to remove unwanted spectral lines, and then enters a multi-group confocal lens array for focusing. At each focal point, the laser beam converges to create an excitation point, generating non-directional Raman scattered light, i.e., forward Raman scattered light, back Raman scattered light, and side Raman scattered light. The multi-group confocal lens array collects the back Raman scattered light, which is opposite to the forward laser direction. The back Raman scattered light sequentially passes through the second short-reflector long-pass optical element 42, the fourth short-reflector long-pass optical element 62, and the converging lens 7, finally entering the spectrometer receiver 8.

[0036] After the forward laser passes through multiple sets of confocal lenses, it is reflected by the third short-reflecting long-pass optical element 61 and re-enters multiple sets of confocal lenses. The secondary excitation also generates forward, backward, and lateral Raman scattered light. The multiple sets of confocal lenses can collect the forward Raman scattered light in the same direction as the reverse laser. That is, the forward Raman scattered light generated by the secondary excitation passes sequentially through the second short-reflecting long-pass optical element 42, the fourth short-reflecting long-pass optical element 62, and the converging lens 7, and finally enters the spectrometer receiver 8; thus realizing dual-wheel excitation and two collections of Raman scattered light.

[0037] It should be noted that the direction in which laser 1 emits laser light is positive (e.g., ...). Figure 1 The positive direction shown is the opposite direction (as shown in the diagram). Figure 1 (As shown in the diagram, the laser light originating from the laser source is defined as forward laser light, and the laser light reflected from the third short-reflecting long-pass optical element 61 is defined as reverse laser light.) The backscattered Raman light generated by forward-propagating laser excitation and the forward-propagating Raman light generated by reverse-propagating laser excitation both propagate in opposite directions, therefore both are reverse Raman scattered light. The front end of an optical element refers to its input end, and the rear end of an optical element refers to its output end.

[0038] like Figure 3 As shown, in this embodiment, the N-point excitation lens assembly 5 includes two sets of confocal lens groups. Each set of confocal lens groups includes two convex lenses with the same focal length f. The structures of the two sets of confocal lens groups are: convex lens A51 + convex lens B52, and convex lens C53 + convex lens D54. The distance between convex lens A51 and convex lens B52 is equal to the sum of their focal lengths, 2f. The distance between convex lens C53 and convex lens D54 is also equal to the sum of their focal lengths, 2f. Therefore, the two sets of confocal lens groups are confocal in pairs, i.e., convex lens A51 and convex lens B52 are confocal, and convex lens C53 and convex lens D54 are confocal. The two confocal points correspond to two Raman scattering excitation points: excitation point 1 and excitation point 2. At these two excitation points, the laser converges and generates strong Raman scattering light.

[0039] The specific process and principle of the two sets of confocal lenses for double-wheel excitation and double-collection of reverse Raman scattered light are as follows.

[0040] The initial stimulation process includes: The forward laser emitted by laser 1 passes through the first short-reflection long-pass optical element 41 and the second short-reflection long-pass optical element 42 before entering the N-point excitation lens assembly 5, generating excitation point 1 and excitation point 2 to the right of convex lens A51 and convex lens C53, respectively. The backscattered Raman light excited at excitation point 1 to the right of convex lens A51 is collected by convex lens A51 and propagated collimated to the left; the backscattered Raman light excited at excitation point 2 to the right of convex lens C53 is collected by convex lens C53 and propagated collimated to the left, then converged by convex lens B52 at the common focal point of convex lens A51 and convex lens B52, i.e., excitation point 1, and then collected by convex lens A51 and propagated collimated to the left. The backscattered Raman light obtained from these two parts of forward laser excitation passes sequentially through the second short-reflection long-pass optical element 42, the fourth short-reflection long-pass optical element 62, and the converging lens 7 before being converged into the spectrometer receiver 8.

[0041] The secondary excitation process includes: The forward laser beam is reflected by the third short-reflecting long-pass optical element 61, while the reverse laser beam generates excitation points 2 and 1 to the left of convex lenses D54 and B52, respectively. The forward Raman scattered light excited at excitation point 2 to the left of convex lens D54 is collected by convex lens C53, collimated, and propagates to the left. It is then converged by convex lens B52 at the common focal point of convex lenses A51 and B52, i.e., excitation point 1, and then collected by convex lens A51 and collimated to the left. The forward Raman scattered light excited at excitation point 1 to the left of convex lens B52 is collected by convex lens A51 and collimated to the left. The forward Raman scattered light obtained from these two reverse laser beams passes sequentially through the second short-reflecting long-pass optical element 42, the fourth short-reflecting long-pass optical element 62, and the converging lens 7 before being converged into the spectrometer receiver 8.

[0042] As can be seen, during the initial excitation process, the convex lenses at odd-numbered positions in the N-group confocal lens system are used to converge the forward laser light from the laser to generate the excitation point; the convex lenses at even-numbered positions are used to collimate and transmit the laser light; and the convex lenses at odd-numbered positions are also used to collect and transmit the reverse Raman scattered light. During the secondary excitation process, the convex lenses at even-numbered positions are used to converge the reverse laser light from the third short-reflector long-pass optical element 61 to generate the excitation point, and the convex lenses at odd-numbered positions are used to collimate and transmit the laser light, and also to collect and transmit the reverse Raman scattered light.

[0043] The device of this invention realizes dual-wheel excitation of N laser convergence points. With negligible attenuation of convex lenses, each additional set of confocal lenses adds one excitation point, and the laser power utilization rate is increased by 2 times. Therefore, it is possible to increase the Raman scattering intensity by 2 times for each additional excitation point while keeping the input laser power constant.

[0044] In a preferred embodiment, the convex lens used to collect and transmit the reverse Raman scattered light in each confocal lens group is an ultra-wide-angle lens, which is beneficial for improving the collection of reverse Raman scattered light. Example 2

[0045] like Figure 2 As shown, a dual-wheel N-point excited Raman scattering light reverse collection device has the same structure as Embodiment 1, except that the first short-reflection long-pass optical element 41 is replaced with a total reflection mirror 43. The laser output from laser 1 passes sequentially through collimating lens 2 and narrow-bandpass filter 3, and is then reflected by total reflection mirror 43 to the second short-reflection long-pass optical element 42. The second short-reflection long-pass optical element 42 inputs the forward laser into the N-point excitation lens assembly 5, realizing the first round of excitation and generating the first reverse Raman scattering light (this is the back-scattering light generated by the forward laser). After the forward laser passes through the N-point excitation lens assembly 5, it is reflected back to the N-point excitation lens assembly 5 by the third short-reflection long-pass optical element 61, resulting in a second excitation and generating the second reverse Raman scattering light (this is the forward Raman scattering light generated by the reverse laser). Both reverse Raman scattering lights generated pass through the second short-reflection long-pass optical element 42 and enter the spectrum receiver 8. The specific principle process is the same as in Embodiment 1 and will not be repeated here. Example 3

[0046] like Figure 4 and Figure 5 As shown, a dual-wheel N-point excited Raman scattering light reverse collection device has the same structure as Embodiment 1, including a laser 1, a collimating lens 2, a narrow bandpass filter 3, a first short-reflection long-pass optical element 41 and a second short-reflection long-pass optical element 42 arranged in parallel, an N-point excitation lens assembly 5, a third short-reflection long-pass optical element 61, a converging lens 7, and a spectrum receiver 8. The difference is that the structure of the N-point excitation lens assembly 5 is different from that in Embodiment 1.

[0047] In this embodiment, the N-point excitation lens assembly includes several convex lenses arranged coaxially. The distance between any two adjacent convex lenses is greater than the sum of the focal lengths of these two convex lenses. The converging image point of the preceding convex lens is used as the object point of the following convex lens, so that the first convex lens is used to converge the laser to form an excitation point, and the subsequent multiple convex lenses are used to re-convex the light transmitted from the excitation point in front of them to form a new excitation point. However, the last convex lens in the N-point excitation lens assembly is used to collimate the light.

[0048] For example, consider five convex lenses: A51, B52, C53, D54, and E55. The incident laser light is converged by convex lens A51, forming excitation point 1 between A51 and B52. This excitation point 1 serves as the image object of convex lens B52. Convex lens B52 converges the light emitted from excitation point 1, forming excitation point 2 between B52 and C53. This excitation point 2 serves as the image object of convex lens C53. This process continues sequentially, with convex lens C53 converging with convex lens D54 to form excitation point 3, and convex lens D54 converging with convex lens E55 to form excitation point 4. Strong Raman scattering light can be generated at all four excitation points. The convex lens E55 at the very end of the assembly receives the light emitted from excitation point 4, collimates it into a parallel ray, and then propagates it backward. The laser beam is directed parallel to the third short-reflection long-pass optical element 61 and then returns. The reverse laser beam is then used to excite Raman scattered light again at excitation point 4, excitation point 3, excitation point 2, and excitation point 1 in sequence.

[0049] In this embodiment, in the N-point excitation lens assembly, the ratio of the focal lengths of any two adjacent convex lenses is 0.2 to 5; and by adjusting each convex lens of the N-point excitation lens assembly so that the distance between adjacent convex lenses is greater than the sum of the focal lengths of the two convex lenses, a laser focusing point can be generated between any two adjacent convex lenses.

[0050] Preferably, the focal lengths of the convex lenses are all equal, f, and the distances between the first and second convex lenses, and between the last and previous convex lenses, are all equal to 3f. The distances between adjacent convex lenses from the second to the penultimate convex lens are equal to 4f. This is illustrated using the above five convex lenses as an example: The distance between convex lens A51 and convex lens B52 is 3f, the distance between convex lens B52 and convex lens C53 is 4f, the distance between convex lens C53 and convex lens D54 is 4f, and the distance between convex lens D54 and convex lens E55 is 3f.

[0051] The specific process and principle of four convex lenses and a double-wheel excitation and collection of reverse Raman scattered light are as follows: The initial stimulation process includes: The forward laser emitted by laser 1 is input into the N-point excitation lens assembly 5 after passing through the first short-reflection long-pass optical element 41 and the second short-reflection long-pass optical element 42. The forward laser beam is focused between convex lens A51 and convex lens B52 to form excitation point 1. Convex lens A51 collects the back-scattered Raman light excited by excitation point 1. The forward laser beam is focused between convex lens B52 and convex lens C53 to form excitation point 2. Convex lens B52 collects the back-scattered Raman light excited by excitation point 2, and then the back-scattered light is collected and transmitted in the opposite direction by convex lens A51. The forward laser beam is focused between convex lens C53 and convex lens C52. The light rays converge between lens C53 and convex lens D54 to form excitation point 3. Convex lens C53 collects the back Raman scattered light excited by excitation point 3, and then transmits it in the reverse direction through convex lens B52 and convex lens A51. The forward laser light converges between convex lens D54 and convex lens E55 to form excitation point 4. Convex lens D54 collects the back Raman scattered light excited by excitation point 4, and then transmits it in the reverse direction through convex lens C53, convex lens B52 and convex lens A51. Thus, the merging, propagation and collection of the reverse Raman scattered light excited by the forward laser at excitation points 1 to 4 are completed.

[0052] The secondary excitation process includes: The forward laser beam is reflected by the third short-reflection long-pass optical element 61. The reverse laser beam is focused between convex lens E55 and convex lens D54 to form excitation point 4. Convex lens D54 collects the forward Raman scattered light excited by excitation point 4, and then it is transmitted in reverse through convex lens C53, convex lens B52, and convex lens A51 in sequence. The reverse laser beam is focused between convex lens D54 and convex lens C53 to form excitation point 3. Convex lens C53 collects the forward Raman scattered light excited by excitation point 3, and then it is transmitted in reverse through convex lens B52 and convex lens A51 in sequence. Mirror A51 performs reverse transmission; the reverse laser beam converges between convex lens C53 and convex lens B52 to form excitation point 2. Convex lens B52 collects the forward Raman scattered light excited by excitation point 2, and then performs reverse collection and transmission through convex lens A51; the reverse laser beam converges between convex lens B52 and convex lens A51 to form excitation point 1. Convex lens A51 collects the forward Raman scattered light excited by excitation point 1; thus, the merging, propagation and collection of the reverse Raman scattered light excited by the reverse laser at excitation points 4 to 1 are completed.

[0053] As can be seen, in the initial excitation process of the N-point excitation lens assembly, the first convex lens is used to converge the forward laser from the laser input component to generate the excitation point, and to collect and transmit the reverse Raman scattered light generated by the excitation point at the rear end. The middle convex lenses are used to converge the laser from the previous convex lens and simultaneously collect and transmit the reverse Raman scattered light generated by the excitation point at the rear end. The last convex lens is used to collimate and transmit the forward laser to the third short-reflection long-pass optical element 61 to achieve laser reflection. In the secondary excitation process of the N-point excitation lens assembly, the last to the second convex lenses are used to converge the reverse laser from the third short-reflection long-pass optical element 61 to generate the excitation point; and except for the last convex lens, the remaining convex lenses are used to collect and transmit the reverse Raman scattered light generated by the excitation point at the rear end.

[0054] In this embodiment, the N-point excitation lens assembly has N+1 convex lenses arranged coaxially, generating N excitation points on the coaxial line. The convex lenses used to collect and transmit the reverse Raman scattered light are all ultra-wide-angle lenses to achieve maximum collection of Raman scattered light. Any number of convex lenses can be added to the right of the last convex lens, and the positional relationship of these added convex lenses is such that the image point of the previous convex lens serves as the object point of the next convex lens; this further improves the utilization rate of laser power and energy.

[0055] In an optional embodiment, the N-point excitation lens assembly can be combined with Embodiment 1 and Embodiment 3. For example, first set several groups of confocal lens groups with the structure shown in Embodiment 1, and then set several convex lenses with the structure shown in Embodiment 3, with all convex lenses being coaxial. Example 4

[0056] like Figure 6 As shown, a dual-wheel N-point excited Raman scattering light reverse collection device includes a laser 1, a collimating lens 2, a narrow bandpass filter 3, a first short-reflection long-pass optical element 41 and a second short-reflection long-pass optical element 42 arranged in parallel, an N-point excitation lens assembly 5, a third short-reflection long-pass optical element 61, a converging lens 7, and a spectrum receiver 8. The arrangement structure of the plurality of convex lenses in the N-point excitation lens assembly 5 can adopt the structure of Embodiment 1 or the structure of Embodiment 3.

[0057] In this embodiment, the N-point excitation lens assembly 5 includes six convex lenses with the same focal length f: convex lens A51, convex lens B52, convex lens C53, convex lens D54, convex lens E55, and convex lens F56. When the layout structure is the same as in Embodiment 1, the distance between convex lens A51 and convex lens B52 is equal to the sum of their focal lengths, 2f; the distance between convex lens C53 and convex lens D54 is equal to the sum of their focal lengths, 2f; and the distance between convex lens E55 and convex lens F56 is equal to the sum of their focal lengths, 2f. This generates a total of three Raman scattering excitation points: excitation point 1 located between convex lens A51 and convex lens B52; excitation point 2 located between convex lens C53 and convex lens D54; and excitation point 3 located between convex lens E55 and convex lens F56. In this layout, a convex lens G (not shown in the figure) can be added behind the convex lens F56, and another excitation point can be added.

[0058] When the layout structure is the same as in Example 3, we have: Convex lenses A51, B52, C53, D54, E55, and F56 are used, with the image point of the previous convex lens serving as the object point of the next convex lens. These lenses converge multiple times to form an excitation point, with one excitation point formed on the right side of each convex lens. There are a total of five Raman scattering excitation points: excitation point 1 located to the right of convex lens A51, excitation point 2 located to the right of convex lens B52, excitation point 3 located to the right of convex lens C53, excitation point 4 located to the right of convex lens D54, and excitation point 5 located to the right of convex lens E55. Example 5

[0059] like Figure 7 As shown, a dual-wheel N-point excited Raman scattering light reverse collection device includes a laser 1, a collimating lens 2, a narrow bandpass filter 3, a first short-reflection long-pass optical element 41 and a second short-reflection long-pass optical element 42 arranged in parallel, an N-point excitation lens assembly 5, a third short-reflection long-pass optical element 61, a converging lens 7, and a spectrum receiver 8. The arrangement structure of the plurality of convex lenses in the N-point excitation lens assembly 5 can adopt the structure of Embodiment 1 or the structure of Embodiment 3.

[0060] Based on Embodiment 4, the N-point excitation lens assembly 5 of this embodiment adds two more convex lenses (i.e., including convex lens A51, convex lens B52, convex lens C53, convex lens D54, convex lens E55, convex lens F56, convex lens G57, and convex lens H58), for a total of eight convex lenses, thus having: a. When the lens layout structure of Example 1 is used, four excitation points can be generated; b. When the lens layout structure of Example 3 is used, seven excitation points can be generated.

[0061] In summary, this invention employs multiple laser focusing points for excitation, thereby significantly improving the utilization rate of laser power. It also features reverse Raman scattering light transmission and collection capabilities, thus multiplying the Raman scattering light signal intensity and enhancing the sensitivity of the Raman scattering spectrometer. Specifically, neglecting lens attenuation, each additional focusing point doubles the laser power utilization rate. With the input laser power remaining constant, each additional focusing point doubles the Raman scattering light intensity. Compared to the traditional single-excitation-point forward Raman scattering collection method, the device of this invention collects (2N-1) times more Raman scattering light.

[0062] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A dual-wheel N-point excited Raman scattering light reverse collection device, characterized in that, It includes a laser input component, a first short-reflection long-pass optical element or a total reflection mirror, a second short-reflection long-pass optical element parallel to the first short-reflection long-pass optical element or the total reflection mirror, an N-point excitation lens component, a third short-reflection long-pass optical element, and a Raman scattering light receiving component; The upper surface normals of the first short-reflection long-pass optical element and the second short-reflection long-pass optical element are at 45° to the horizontal axis; the third short-reflection long-pass optical element is perpendicular to the lens central axis of the N-point excitation lens assembly, and its surface normal is at 0° to the horizontal axis. The forward laser from the laser input component is sequentially input to the N-point excitation lens assembly via a first short-reflection long-pass optical element or a total reflection mirror and a second short-reflection long-pass optical element. The N-point excitation lens assembly includes multiple convex lenses arranged coaxially to receive the forward laser and converge it multiple times on the coaxial line to form N excitation points to generate the first round of reverse Raman scattering light, where N is a positive integer greater than 1. The N-point excitation lens assembly is also used to receive the reverse laser reflected by the third short-reflection long-pass optical element and to converge multiple times on the coaxial line to form N excitation points to generate a second round of reverse Raman scattering light. The reverse Raman scattered light generated by the dual-wheel excitation is collected by a convex lens and transmitted to the Raman scattered light receiving component.

2. The dual-wheel N-point excited Raman scattering light reverse collection device according to claim 1, characterized in that, The laser input component includes a laser, a collimating lens, and a narrow-bandpass filter. The laser is used to emit a laser source, the collimating lens is used to collimate the laser, and the narrow-bandpass filter is used to filter out extraneous spectral lines in the laser.

3. The dual-wheel N-point excited Raman scattering light reverse collection device according to claim 1, characterized in that, The Raman scattering light receiving assembly includes a fourth short-reflection long-pass optical element, a converging lens, and a spectrometer. The fourth short-reflection long-pass optical element has a surface normal at 0° to the horizontal axis and is used to block excess laser light from entering the spectrometer. The converging lens is used to converge the reverse Raman scattered light and transmit it to the spectrometer.

4. The dual-wheel N-point excited Raman scattering light reverse collection device according to claim 1, characterized in that, Multiple convex lenses arranged linearly along the same axis form N groups of confocal lenses. In each group of confocal lenses, the two convex lenses are confocal, and the common focal point is the excitation point. The two confocal convex lenses have the same focal length, and the distance between the two convex lenses is equal to the sum of their focal lengths.

5. The dual-wheel N-point excited Raman scattering light reverse collection device according to claim 4, characterized in that, In the initial excitation process, the N sets of confocal lenses are used to converge the positive laser from the laser input component to generate the excitation point; the convex lenses at even-numbered positions are used to collimate and transmit the laser; and the convex lenses at odd-numbered positions are also used to collect and transmit the reverse Raman scattered light. In the secondary excitation process, the N-group confocal lens system uses even-numbered convex lenses to converge the reverse laser light from the third short-reflector long-pass optical element to generate the excitation point, and odd-numbered convex lenses to collimate and transmit the laser light, as well as to collect and transmit the reverse Raman scattered light.

6. The dual-wheel N-point excited Raman scattering light reverse collection device according to claim 1, characterized in that, In the N-point excitation lens assembly, the distance between any two adjacent convex lenses is greater than the sum of the focal lengths of these two convex lenses, and the converging image point of the preceding convex lens is used as the object point of the following convex lens, so that the first convex lens is used to converge the laser to form an excitation point, and the subsequent multiple convex lenses are used to re-convex the light transmitted from the excitation point in front of it to form a new excitation point, but the last convex lens in the N-point excitation lens assembly is used to collimate the light.

7. The dual-wheel N-point excited Raman scattering light reverse collection device according to claim 6, characterized in that, The ratio of the focal lengths of any two adjacent convex lenses is between 0.2 and 5.

8. The dual-wheel N-point excited Raman scattering light reverse collection device according to claim 6, characterized in that, During the initial excitation process, the N-point excitation lens assembly has a first convex lens used to converge the positive laser from the laser input component to generate the excitation point, and to collect and transmit the reverse Raman scattered light generated by the excitation point at the rear end. The middle convex lenses are used to converge the laser from the previous convex lens and collect and transmit the reverse Raman scattered light generated by the excitation point at the rear end. The last convex lens is used to collimate and transmit the positive laser to the third short-reflection long-pass optical element to achieve laser reflection. During the secondary excitation process, the last to the second convex lens of the N-point excitation lens assembly are used to converge the reverse laser light from the third short-reflection long-pass optical element to generate the excitation point; and except for the last convex lens, the other convex lenses are used to collect and transmit the reverse Raman scattered light generated by the excitation point at the rear end.

9. The dual-wheel N-point excited Raman scattering light reverse collection device according to claim 1, characterized in that, Both the first short-wavelength-pass optical element and the second short-wavelength-pass optical element are short-wavelength-pass filters or short-wavelength-pass dichroic mirrors.

10. The dual-wheel N-point excited Raman scattering light reverse collection device according to claim 3, characterized in that, Both the third short-reflection long-pass optical element and the fourth short-reflection long-pass optical element are 0° short-reflection long-pass filters or 0° short-reflection long-pass dichroic mirrors.

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