Miniature probe, optical fiber type LIBS (Laser-induced Breakdown Spectroscopy) system and detection method

Abstract

The invention discloses a miniature probe, an optical fiber type LIBS (Laser-induced Breakdown Spectroscopy) system and a detection method. The miniature probe comprises an illumination optical fiber, a laser transmission optical fiber interface, a laser collimation light path, a camera imaging light path, a CMOS (Complementary Metal-Oxide-Semiconductor Transistor) imaging sensor and a CMOS overturning control module. The probe is integrated with an optical fiber type LIBS (laser-induced breakdown spectroscopy) system and can go deep into narrow pipeline gaps of a nuclear power station to carry out element quantitative analysis and material identification traceability on foreign matters. According to the optical fiber laser-induced breakdown spectroscopy probe, the optical fiber laser-induced breakdown spectroscopy (LIBS) miniature probe with the same optical path for laser focusing and spectrum collection is realized, and the detection process of target aiming by the camera, sensor lifting, laser targeting and spectrum returning is realized in a mode of sharing the optical path and turning over the CMOS sensor.

Description

Technical Field

[0001] The present application belongs to the technical field of laser induced breakdown spectroscopy and relates to a microprobe, an optical fiber LIBS system and a detection method. Background Art

[0002] Laser induced breakdown spectroscopy (LIBS) is an atomic optical emission spectroscopy technique mainly used for elemental analysis. It uses laser to excite plasma on the surface of a substance, identifies the spectral lines of the elements contained in the substance through the plasma emission spectrum, and then quantitatively measures the element content. The current LIBS technology is mainly divided into traditional, fiber-optic, telescope, handheld, etc. The fiber laser induced breakdown spectroscopy (FO-LIBS) system simplifies the optical system of laser transmission and plasma spectrum collection through optical fiber, which is used to replace the open optical configuration in traditional LIBS. Due to the long-distance optical transmission and spatial flexibility of optical fiber, FO-LIBS provides a more feasible solution for rapid analysis of material composition in narrow spaces, obstructions, radiation or underwater scenes. FO-LIBS is particularly suitable for harsh environments such as nuclear power plants and offshore wind power platforms.

[0003] In nuclear power plants, radioactive foreign bodies of unknown composition exist between narrow gaps (millimeter level) in steam pipes and other pipelines. Such foreign bodies will affect the normal operation of the nuclear power system and need to be manually removed for chemical composition inspection after shutdown, resulting in reduced efficiency and economic losses. FO-LIBS can be used for in-situ, non-stop, and real-time element detection of radioactive foreign bodies, and then provide information such as the brand and source of the foreign bodies. However, due to the narrow gap, the current FO-LIBS probe size cannot penetrate into narrow areas for detection. At present, most FO-LIBS probes do not consider size limitations, in which the optical paths of the focused laser and the spectrum collection are separated, occupying a large volume. In addition, most FO-LIBS probes do not consider that cameras and lighting fibers are needed to assist in locating the target to be measured during the detection process. If cameras and lighting fibers are added to the current FO-LIBS probes, the size of the slits will inevitably exceed the size of the slits. Traditional endoscopes can meet the process of entering the slit for monitoring, but cannot be combined with LIBS systems for element detection. The first reason is that the optical system used is mainly used for imaging, and it is unable to collimate and refocus the laser transmitted by multimode optical fiber; secondly, the LIBS return spectrum requires the optical system to transmit a wide wavelength range, which most endoscope lenses cannot meet; thirdly, the laser used in LIBS is a nanosecond pulse laser with high power, which will damage the optical lens of the endoscope. At present, even if there is a combination of endoscope and LIBS in medicine, the two optical path systems are separated, and the optical path is not shared and the size is not reduced. Summary of the invention

[0004] The purpose of the present application is to solve the problems in the prior art and to provide a microprobe, a fiber-optic LIBS system and a detection method.

[0005] In order to achieve the above objectives, this application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a miniature probe, comprising:

[0007] A housing, wherein a lighting optical fiber window and a common lens are disposed at the front end of the housing, and an optical fiber cable interface is disposed at the end of the housing;

[0008] An optical fiber cable interface, at the end of which an illumination optical fiber and a signal cable are bundled and a laser-spectrum transmission optical fiber is arranged;

[0009] The illumination optical fiber and the signal cable are bundled together, wherein the illumination optical fiber and the signal cable are provided with an illumination optical fiber and a signal cable, wherein the illumination optical fiber is used to emit the illumination light beam through the illumination optical fiber window; and the signal cable is used to receive the spectrum incident from the common lens and output the spectrum information to the spectrometer;

[0010] Laser-spectrum transmission optical fiber, the laser-spectrum transmission optical fiber is used to collimate the outgoing laser through an optical component and then emit it through a common lens.

[0011] In a second aspect, the present application provides a fiber-optic LIBS system, comprising:

[0012] A miniature probe, wherein the optical fiber cable interface of the miniature probe is connected to the laser and the spectrometer respectively through optical fibers;

[0013] A display unit, wherein a signal input end of the display unit is connected to a signal cable of the miniature probe.

[0014] In a third aspect, the present application provides a detection method of a fiber-optic LIBS system, comprising the following steps:

[0015] Step 1: Turn on the lighting fiber, lift the reflector, insert it into the slit of the pipe and other scenes to locate foreign objects, observe the environment around the probe through the display, and look for foreign objects;

[0016] Step 2: After locating the foreign object, place the position where the foreign object needs to be detected at the center mark of the screen and adjust the focus distance;

[0017] Step 3: After confirmation, adjust the system parameters, click the detection button, the reflector falls, and the laser is focused on the sample surface to generate laser-induced plasma;

[0018] Step 4, the laser stops after the previously set number of shots, the spectrum is collected and displayed on the display, and the relevant material information is also displayed in the corresponding position of the software;

[0019] Step 5, lift the reflector to check the state of the foreign matter micro-ablation pit at this time;

[0020] Step 6: End the test and pull the probe and optical fiber out of the test scene.

[0021] Compared with the prior art, this application has the following beneficial effects:

[0022] This application adopts a shared optical path arrangement for camera imaging, laser focusing and targeting, and plasma spectrum backhaul collection to solve the problem that the fiber LIBS equipment cannot penetrate into the narrow pipe gaps of nuclear power plants to detect foreign objects, and to perform elemental quantitative analysis and material identification and tracing of foreign objects. This application implements a fiber LIBS microprobe with the same optical path for laser focusing and spectrum collection, and by sharing the optical path and flipping the CMOS sensor, it realizes the detection process of camera aiming at the target - sensor lifting - laser targeting and spectrum backhaul. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 This is a schematic diagram of the structure of the probe of this application.

[0025] Figure 2 A cross-sectional view of the probe for this application.

[0026] Figure 3 Schematic diagram of the LIBS system combined with the probe for this application.

[0027] Figure 4 This is a schematic diagram of the actual usage scenario of this application.

[0028] Among them: 1 is the illumination fiber window, 2 is the common lens, 3 is the illumination fiber, 4 is the bundle of the illumination fiber and the signal cable, 5 is the laser-spectrum transmission fiber, 6 is the fiber cable interface, 7 is the collimating lens, 8 is the CMOS sensor, 9 is the laser, 10 is the digital delay generator, 11 is the spectrometer, 12 is the display unit, 13 is the multimode fiber, 14 is the micro probe, 15 is the laser-induced plasma, and 16 is the sample. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0031] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0032] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the invented product is usually placed when used. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0033] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0034] In the description of the embodiments of the present application, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0035] The present application is further described in detail below with reference to the accompanying drawings:

[0036] See also Figure 1 The embodiment of the present application discloses a miniature probe, including a housing, an optical fiber cable interface 6, an illumination optical fiber and signal cable bundle 4, and a laser-spectrum transmission optical fiber 5. An illumination optical fiber window 1 and a common lens 2 are arranged at the front end of the housing, and the common lens 2 is a focusing lens. An optical fiber cable interface 6 is arranged at the end of the housing; an illumination optical fiber and signal cable bundle 4 and a laser-spectrum transmission optical fiber 5 are arranged at the end of the optical fiber cable interface 6; an illumination optical fiber 3 and a signal cable are arranged in the illumination optical fiber and signal cable bundle 4, and the illumination optical fiber 3 is used to emit an illumination light beam through the illumination optical fiber window 1; the signal cable is used to receive the spectrum incident from the common lens 2, and output the spectrum information to the spectrometer; the laser-spectrum transmission optical fiber 5 is used to collimate the emitted laser through an optical component and then emit it from the common lens 2.

[0037] It should be noted that the optical component includes a collimating lens 7 disposed on the exit optical path of the laser-spectrum transmission optical fiber 5, and the exiting laser is focused by the common lens 2 to the surface of the sample 16 to be tested through the collimating lens 7, thereby generating a laser-induced plasma 15. A flippable reflector is also disposed on the optical path between the optical component and the common lens 2; when the reflector is lifted, the optical fiber or spectrum incident from the common lens 2 can be reflected to the CMOS sensor 8, and the signal output end of the CMOS sensor 8 is connected to a spectrometer or a display unit.

[0038] like Figure 3 As shown, the embodiment of the present application provides a fiber-optic LIBS system, including a microprobe 14 and a display unit 12. The optical fiber cable interface 6 of the microprobe is connected to the laser 9 and the spectrometer 11 respectively through optical fibers; the signal input end of the display unit 12 is connected to the signal cable of the microprobe. The laser 9, the spectrometer 11 and the display unit 12 are respectively connected to the digital delay generator 10, and the timing of the laser 9, the spectrometer 11 and the display unit 12 are all controlled by the digital delay generator 10. The optical fiber is a multimode optical fiber 13.

[0039] The structural principle of this application: like Figures 1 to 4 As shown, the present application is connected to the illumination fiber and signal cable bundle 4 and the laser-spectrum transmission fiber 5 at the optical fiber cable interface 6. The illumination fiber 3 continues to transmit the illumination light beam from the illumination fiber 3 to the illumination fiber window 1 to emit light. When the flip CMOS sensor 8 falls, the laser emitted by the laser-spectrum transmission fiber 5 is collimated by the collimating lens 7, and then the front-end focusing lens outputs the focused laser from the focusing / returning / videoing common lens 2 to penetrate the surface of the sample 16. In the normal state, the flip CMOS sensor 8 is kept lifted up, receiving the wide-angle picture transmitted from the focusing / returning / videoing common lens 2, and the signal line in the illumination fiber and signal cable bundle 4 is output to the electronic device screen.

[0041] The probe size is 5mm in diameter and 15mm in length. The focusing / returning / videoing common lens 2, collimating lens 7 and other optical lenses need to transmit light in the wavelength range of 185nm-1100nm to meet the 1064nm Nd:YAG laser transmission and full-band spectrum transmission. The optical fiber interface in the optical fiber cable interface 6 is an SMA-905 interface. To ensure that the diameter is less than 5mm, the optical fiber should adopt armoring solutions such as plastic sheath. The collimating lens 7 should be coordinated with the laser-spectrum transmission optical fiber 5, the focusing / returning / videoing common lens 2, and the focusing lens to achieve a smaller focused spot (<500 microns) when the laser is 15mm outside the probe. In addition, the focusing lens and the exit window should be designed as equivalent wide-angle lenses to meet the imaging requirements of the detection camera.

[0042] During actual measurement, the device should determine the focus distance based on the image transmitted by the camera. A target auxiliary bracket can also be installed in front of the probe to fix the distance between the sample 16 and the probe.

[0043] According to this application, a small LIBS probe equipped with a camera is designed, including a probe housing, an optical fiber interface, an illumination optical fiber 3, a lens group, a reflector, a CMOS sensor, a microcontroller, an actuating connector, etc. The characteristics of the probe are that the probe is small in size, with a diameter of only 4-6 mm; it is equipped with a CMOS sensor and a camera, which can image and locate the foreign object to be detected; when the laser is shooting, the reflector falls, and the laser focusing and spectrum collection share the camera imaging optical path.

[0044] When the probe and the optical fiber are extended into a slit or other scene, the illumination optical fiber 3 is started, and the environmental conditions in the slit are transmitted to the CMOS sensor through the camera optical path, and then presented on the screen, so that the user can find the location of the foreign object. After finding the foreign object, aim and focus according to the camera. When ready, click the detection button, the CMOS sensor is lifted, the laser passes through the probe and focuses on the surface of the foreign object to generate plasma, and the plasma spectrum is transmitted back to the optical fiber along the same optical path, and then transmitted to the spectrometer 11 for analysis. At the end of the detection, the CMOS sensor returns to its original position.

[0045] The lenses in this application are made of UV fused silica as much as possible.

[0046] In the present application, the flipping solution of the CMOS sensor can also be implemented by flipping the reflector, which can prevent the precision sensor from moving.

[0047] The microprobe of the present application needs to be used in a fiber-optic LIBS system. The 1064nm nanosecond laser pulse generated by the laser 9 enters the specially designed multimode optical fiber 13 through the fiber coupling module, and the SMA905 interface at the other end of the multimode optical fiber 13 is connected to the interface of the microprobe 14 to achieve laser pulse focusing on the surface of the sample 16. Since the optical path is reversible, the spontaneous light emission of the laser-induced plasma 15 will be recovered by the microprobe 14 along the same optical path, and input into the connected spectrometer 11 through the same multimode optical fiber 13, and then presented on the computer screen 12 for spectral analysis and data processing. The timing of all devices is controlled by a digital delay generator 10.

[0048] The working process of the probe proposed in this application is as follows:

[0049] (1) Before using the probe, check the connection of the optical fiber and signal line, check that the illumination optical fiber 3 emits light normally, the camera images normally when the reflector is raised, the laser focuses normally when the reflector is lowered, and the spectrometer 11 collects signals normally;

[0050] (2) The illumination fiber 3 is turned on, the reflector is raised, and the probe is inserted into a pipe slit or other scene to locate foreign objects. The environment around the probe is observed through the display to find foreign objects;

[0051] (3) After locating the foreign object, place the position where the foreign object needs to be detected at the center mark of the screen and adjust the focus distance;

[0052] (4) After confirmation, adjust the system parameters, click the detection button, the reflector falls, and the laser is focused on the surface of the sample 16 to generate laser-induced plasma 15;

[0053] (5) The laser stops after the previously set number of shots, the spectrum is collected and displayed on the display, and the relevant material information is also displayed in the corresponding position of the software;

[0054] (6) The reflector is raised to check the state of the foreign matter micro-ablation pit;

[0055] (7) After the test is completed, the probe and optical fiber are pulled out of the pipeline slit or other test scenarios.

[0056] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A miniature probe, characterized in that: include: A housing, wherein a lighting optical fiber window (1) and a common lens (2) are arranged at the front end of the housing, and an optical fiber cable interface (6) is arranged at the end of the housing; An optical fiber cable interface (6), wherein an illumination optical fiber and signal cable bundle (4) and a laser-spectrum transmission optical fiber (5) are arranged at the end of the optical fiber cable interface (6); The illumination optical fiber and signal cable are combined into a bundle (4), wherein the illumination optical fiber and signal cable bundle (4) is provided with an illumination optical fiber (3) and a signal cable, wherein the illumination optical fiber (3) is used to emit an illumination light beam through an illumination optical fiber window (1); and the signal cable is used to receive a spectrum incident from a common lens (2) and output the spectrum information to a spectrometer; A laser-spectrum transmission optical fiber (5) is used to collimate the emitted laser light through an optical component and then emit the laser light through a common lens (2).

2. The microprobe according to claim 1, characterized in that: The optical component comprises a collimating lens (7) arranged on the exit optical path of the laser-spectral transmission optical fiber (5); the exiting laser passes through the collimating lens (7) and is focused by a common lens (2) onto the surface of a sample to be tested (16), thereby generating laser-induced plasma (15).

3. The microprobe according to claim 1, characterized in that: A flippable reflector is also provided on the optical path between the optical component and the common lens (2); when the reflector is lifted up, the optical fiber or spectrum incident from the common lens (2) can be reflected to the CMOS sensor (8); the signal output end of the CMOS sensor (8) is connected to a spectrometer or a display unit.

4. The microprobe according to claim 1, characterized in that: The common lens (2) is a focusing lens.

5. A fiber-optic LIBS system, characterized in that: include: The microprobe (14) according to any one of claims 1 to 4, wherein the optical fiber cable interface (6) of the microprobe (14) is connected to the laser (9) and the spectrometer (11) respectively through optical fibers; A display unit (12), wherein a signal input end of the display unit (12) is connected to a signal cable of the miniature probe.

6. The optical fiber LIBS system according to claim 5, characterized in that: The laser (9), spectrometer (11) and display unit (12) are respectively connected to a digital delay generator (10), and the timing of the laser (9), spectrometer (11) and display unit (12) is controlled by the digital delay generator (10).

7. The optical fiber LIBS system according to claim 5, characterized in that: The optical fiber is a multimode optical fiber (13).

8. A detection method using the fiber-optic LIBS system according to any one of claims 5 to 7, characterized in that: The following steps are involved: Step 1, turn on the illumination fiber (3), lift the reflector, insert it into the slit of the pipe and other scenes to locate the foreign object, observe the environment around the probe through the display, and look for the foreign object; Step 2: After locating the foreign object, place the position where the foreign object needs to be detected at the center mark of the screen and adjust the focus distance; Step 3, after confirmation, adjust the system parameters, click the detection button, the reflector falls, and the laser is focused on the surface of the sample (16) to generate laser-induced plasma (15); Step 4, the laser stops after the previously set number of shots, the spectrum is collected and displayed on the display, and the relevant material information is also displayed in the corresponding position of the software; Step 5, lift the reflector to check the state of the foreign matter micro-ablation pit at this time; Step 6: End the test and pull the probe and optical fiber out of the test scene.

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