Laser induced breakdown spectroscopy acquisition device and method

Abstract

The present invention relates to a laser induced breakdown spectrum acquisition device and method. The translation stage in the laser induced breakdown spectrum acquisition device of the present invention is located above the sample to be tested, and is used to carry the first objective lens assembly and the second objective lens assembly, and drive the first objective lens assembly and the second objective lens assembly to move, so that the first objective lens assembly or the second objective lens assembly is located above the sample to be tested, thereby operating a preset area located on the sample to be tested, realizing rapid switching between the first objective lens assembly and the second objective lens assembly, and thus improving the test efficiency. In addition, the system illumination observation unit and the laser excitation unit of the present invention use different objective lenses, so that the objective lens magnification can be adjusted separately, and the objective lens magnification can be selected according to the actual application scenario, thereby expanding the use scenario.

Description

Technical Field

[0001] The present invention relates to the technical field of sample detection, and in particular to a laser induced breakdown spectrum acquisition device and method. Background Art

[0002] Laser Induced Breakdown Spectroscopy (LIBS) generates plasma through the interaction of pulsed laser and matter, and analyzes the spectrum in the plasma to achieve qualitative and quantitative analysis of the substance to be tested. Laser induced breakdown spectroscopy technology is also developing rapidly. Compared with other material identification technologies, laser induced breakdown spectroscopy technology has the advantages of fast and contactless measurement, so its application field is gradually expanding.

[0003] The existing commercialized laser induced breakdown spectroscopy technology equipment can be found in Chinese patent CN 210571951 U, which provides a multi-mode scanning microscope imaging system based on laser induced photothermal effect. The system uses the same objective lens for bright field imaging and laser excitation, and realizes function switching through a filter device, resulting in complex optical path structure, high equipment cost, and large equipment volume. In addition, it is impossible to quickly switch between the microscope objective lens and the laser induced breakdown spectroscopy technology objective lens, resulting in low efficiency of testing samples. At the same time, due to the sharing of the same objective lens, it is impossible to select an objective lens with a specific magnification to observe a specific sample during bright field imaging, and the imaging is greatly restricted. The limitation is that a small magnification objective lens cannot observe samples of smaller size, and it is necessary to switch to a large magnification objective lens. In this patent, a modulated pump laser is used to irradiate the surface of the material. Since the surface of the sample to be tested is often rough and uneven, the defocus amount changes, which causes the collected spectral information to fluctuate, which will seriously affect the stability and accuracy of the laser induced breakdown spectroscopy technology analysis. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a laser induced breakdown spectroscopy acquisition device and method.

[0005] A laser induced breakdown spectroscopy acquisition device, comprising:

[0006] An illumination observation unit, used to provide a field of view for laser-induced breakdown spectroscopy acquisition;

[0007] A laser excitation unit, used for irradiating a preset area on the surface of the sample to be tested and exciting and generating a sample plasma beam;

[0008] A spectrum collection unit, used for collecting spectrum data of the sample plasma beam excited by the laser excitation unit;

[0009] A translation stage, located above the sample to be tested, for carrying the first objective lens assembly and the second objective lens assembly and driving the first objective lens assembly and the second objective lens assembly to move above the sample to be tested, so that the illumination observation unit or the laser excitation unit acts on the preset area;

[0010] The computing unit is used to coordinately control the plasma excitation, plasma spectrum collection, excitation process observation and movement of the translation stage of the entire device, and to process and analyze the spectrum data of the collected sample plasma beam.

[0011] Preferably, the lighting observation unit comprises:

[0012] LED, the LED is used to provide an illumination beam;

[0013] A collimating lens group, wherein the collimating lens group is used to collimate the illumination light beam to obtain a collimated illumination light beam;

[0014] A beam splitter, which reflects the collimated illumination light beam once;

[0015] a first reflector, wherein the first reflector performs secondary reflection on the collimated illumination light beam;

[0016] A first objective lens assembly, the first objective lens assembly is used to focus the collimated illumination light beam on a preset area on the surface of the sample to be tested;

[0017] A first lens, wherein the light scattered by the surface of the sample to be tested is sequentially collimated by the first objective lens assembly and reflected by the first reflector and then transmitted by the beam splitter, and the first lens is used to focus the light transmitted by the beam splitter;

[0018] A camera receives the light beam focused by the first lens.

[0019] Preferably, the collimating lens group includes a second lens and a third lens, the focal length of the third lens is twice that of the second lens, and the second lens is confocal with the third lens to form a 4f imaging system.

[0020] Preferably, the first objective lens assembly comprises a third reflector and an imaging objective lens, the third reflector is used to direct the collimated illumination light beam reflected by the first reflector into the imaging objective lens; the imaging objective lens is used to focus the collimated illumination light beam onto the surface of the sample to be tested.

[0021] Preferably, the laser excitation unit comprises:

[0022] A nanosecond pulse laser, which emits nanosecond pulse laser;

[0023] Axicon lens group, the nanosecond pulse laser emits a collimated Bessel beam after passing through the axicon lens group;

[0024] a second reflector, the second reflector being used to change a transmission direction of the collimated Bessel light beam;

[0025] The second objective lens assembly focuses the collimated Bessel light beam on a preset area on the surface of the sample to be tested, and excites the sample plasma beam.

[0026] Preferably, the conical lens group includes a first conical lens and a second conical lens, the vertex angle of the first conical lens is arranged relative to the vertex angle of the second conical lens, the conical angle range of the first conical lens and the second conical lens is 10°-30°, the conical angles of the first conical lens and the second conical lens are the same, and the aperture of the second conical lens is twice the aperture of the first conical lens.

[0027] Preferably, the second objective lens assembly comprises a fourth reflector and an ultraviolet objective lens, the fourth reflector is used to direct the collimated Bessel light beam reflected by the second reflector into the ultraviolet objective lens; the ultraviolet objective lens is used to focus the collimated Bessel light beam onto the surface of the sample to be tested.

[0028] Preferably, the spectrum acquisition unit comprises:

[0029] An open-loop reflector, the open-loop reflector is disposed between the axicon lens group and the second reflector, the open-loop reflector has an open-loop area and a non-open-loop area, the open-loop area can accommodate the collimated Bessel light beam emitted by the axicon lens group to pass through, and the non-open-loop area reflects the sample plasma light beam excited by the surface of the sample to be tested;

[0030] A slit, wherein the slit is used to shape the sample plasma beam reflected by the open-loop reflector to obtain a linear sample plasma beam;

[0031] A chirped reflective volume Bragg grating, wherein the chirped reflective volume Bragg grating is used to perform narrow-band spectroscopy on the linear sample plasma beam to obtain spectra in multiple different bands;

[0032] A microlens array, wherein the microlens array focuses the spectra of the plurality of different wavebands respectively;

[0033] A linear array CCD receives intensity information of different wavelengths focused by the microlens array, wherein the intensity information of different wavelengths is spectral data.

[0034] Preferably, the inner diameter D1 of the open-loop region of the open-loop reflector is not larger than the inner diameter R1 of the collimated Bessel beam emitted by the axle lens group, and the outer diameter D2 of the open-loop region of the open-loop reflector is not smaller than the outer diameter R2 of the collimated Bessel beam emitted by the axle lens group.

[0035] Preferably, the chirped reflective volume Bragg grating has a grating diffraction angle θ=10°-40°.

[0036] Preferably, the radius of curvature of the microlens array is 50-200 mm.

[0037] A laser induced breakdown spectroscopy acquisition method is implemented using the laser induced breakdown spectroscopy acquisition device as described above, comprising the following steps:

[0038] S1: Control the translation stage so that the first objective lens assembly is located above the sample to be tested;

[0039] S2: Turn on the LED, and the illumination light beam emitted by the LED passes through the collimating lens group and is reflected by the beam splitter to the first reflector. After being reflected by the first reflector, it is focused on the sample to be tested by the first objective lens assembly, and the irradiated area on the sample to be tested is marked as a preset area;

[0040] S3: The light scattered by the preset area passes through the first objective lens assembly and the first reflector in sequence, and is then transmitted by the beam splitter. After transmission, the light is focused on the camera by the first lens to form an image;

[0041] S4: controlling the translation stage to move the second objective lens assembly to above the sample to be tested, and allowing the light emitted by the second objective lens assembly to irradiate a preset area;

[0042] S5: Turn on the nanosecond pulse laser, and the nanosecond pulse laser emitted by the nanosecond pulse laser emits a collimated Bessel beam after passing through the axle lens group. The collimated Bessel beam is reflected by the second reflector and irradiated by the second objective lens assembly to a preset area of ​​the sample to be tested;

[0043] S6: The material in the preset area is ablated and peeled off, and a cloud of nanoparticles is formed above the sample, inducing plasma luminescence to obtain a sample plasma beam;

[0044] S7: the sample plasma beam passes through the second objective lens assembly and the first reflector in sequence and is reflected by the non-open-loop region of the open-loop reflector. The reflected sample plasma beam is beam shaped by the slit to obtain a linear sample plasma beam.

[0045] S8: the linear sample plasma beam is reflected by the chirped reflective volume Bragg grating and then focused on the linear array CCD by the microlens array;

[0046] S9: the linear array CCD collects intensity information of different wavelengths of the linear sample plasma beam after being focused by the microlens array, the intensity information of different wavelengths being spectral data, and transmits the spectral data to a computing unit;

[0047] S10: The computing unit processes and analyzes the spectral data, thereby achieving qualitative and quantitative analysis of the sample to be tested.

[0048] The above technical solution of the present invention has the following advantages compared with the prior art:

[0049] 1. The translation stage of the present invention is located above the sample to be tested, and is used to carry the first objective lens assembly and the second objective lens assembly, and drive the first objective lens assembly and the second objective lens assembly to move, so that the first objective lens assembly or the second objective lens assembly is located above the sample to be tested, thereby operating a preset area located on the sample to be tested, realizing rapid switching between the first objective lens assembly and the second objective lens assembly, and thereby improving test efficiency.

[0050] 2. The illumination observation unit and the laser excitation unit of the present invention use different objective lenses, which can achieve separate adjustment of the objective lens magnification and can select the objective lens magnification according to the actual application scenario, thereby expanding the usage scenario.

[0051] 3. In the laser induced breakdown spectroscopy acquisition device provided by the present invention, an open-loop reflector is used to greatly reduce the attenuation of the intensity of the nanosecond pulse laser used to induce plasma luminescence of the sample to be tested during the transmission process, which is beneficial to induce the plasma luminescence signal of the sample to be tested to enhance; compared with the existing laser induced breakdown spectroscopy equipment using a dichroic mirror, it not only simplifies the light rate, but also can realize the full-band collection of the plasma spectrum.

[0052] 4. The laser induced breakdown spectroscopy acquisition device of the present invention uses a pair of conical lenses with opposite apex angles to construct a collimated Bessel beam and focus it on the surface of the sample to be tested. Since the Bessel beam has the characteristics of small main lobe diameter, long focal depth, and controllable annular spot, it can improve the tolerance of laser induced breakdown spectroscopy technology to changes in defocus, reduce spectral fluctuations caused by uneven sample surfaces, and the annular light source is more conducive to adapting the open-loop reflector of this system, reducing laser energy loss, thereby improving the accuracy of laser induced breakdown spectroscopy analysis.

[0053] 5. In the laser induced breakdown spectroscopy acquisition device of the present invention, a chirped reflective volume Bragg grating is used to replace the complex multi-channel spectrometer structure. Compared with ordinary surface gratings, the chirped reflective volume Bragg grating has higher resolution and higher diffraction efficiency, which can reach 99%, which is beneficial to improve signal strength. In addition, the inclination angle of the light beam emitted by the chirped reflective volume Bragg grating is the same, and no additional collimation is required. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0055] Figure 1 It is a schematic diagram of the laser induced breakdown spectroscopy acquisition device of the present invention.

[0056] Figure 2 Schematic diagram of the conical lens assembly of the present invention.

[0057] Figure 3 Schematic diagram of the open-loop reflector of the present invention.

[0058] Figure 4 It is a schematic diagram of the chirped reflective volume Bragg grating of the present invention.

[0059] Figure 5 Schematic diagram of the microlens array of the present invention.

[0060] Description of the reference numerals in the specification: 1. illumination observation unit; 101. LED; 102. collimating lens group; 1021. second lens; 1022. third lens; 103. beam splitter; 104. first reflector; 105. first objective lens assembly; 1051. third reflector; 1052. imaging objective lens; 106. first lens; 107. camera; 2. laser excitation unit; 201. nanosecond pulse laser; 202. conical lens group; 2021 , first conical lens; 2022, second conical lens; 203, second reflector; 204, second objective lens assembly; 2041, fourth reflector; 2042, ultraviolet objective lens; 3, spectrum acquisition unit; 301, open-loop reflector; 3011, open-loop area; 3012, non-open-loop area; 302, slit; 303, chirped reflective volume Bragg grating; 304, microlens array; 305, linear array CCD; 4, translation stage; 5, sample to be tested. DETAILED DESCRIPTION

[0061] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0062] Reference Figure 1 As shown, the present invention provides a laser induced breakdown spectrum acquisition device, comprising: an illumination observation unit 1, a laser excitation unit 2, a spectrum acquisition unit 3, a translation stage 4 and a calculation unit.

[0063] The illumination observation unit 1 is used to provide a field of view for laser induced breakdown spectroscopy acquisition, and includes an LED 101, a collimating lens group 102, a beam splitter 103, a first reflector 104, a first objective lens assembly 105, a first lens 106 and a camera 107; the LED 101 is used to provide an illumination beam; the collimating lens group 102 is used to collimate the illumination beam to obtain a collimated illumination beam; the beam splitter 103 reflects the collimated illumination beam once; the first reflector 104 reflects the collimated illumination beam twice; the first objective lens assembly 105 is used to focus the collimated illumination beam on a preset area on the surface of the sample to be tested 5; the light scattered from the surface of the sample to be tested 5 is collimated by the first objective lens assembly 105 and the first reflector 104 in turn and then transmitted by the beam splitter 103; the first lens 106 is used to focus the light transmitted by the beam splitter 103; the camera 107 receives the light beam focused by the first lens 106.

[0064] In a specific embodiment, the first objective lens assembly 105 includes a third reflector 1051 and an imaging objective lens 1052, wherein the third reflector 1051 is used to direct the collimated illumination beam reflected by the first reflector 104 into the imaging objective lens 1052; and the imaging objective lens 1052 is used to focus the collimated illumination beam onto the surface of the sample 5 to be tested.

[0065] In a specific embodiment, the collimating lens group 102 includes a second lens 1021 and a third lens 1022, the focal length of the third lens 1022 is twice that of the second lens 1021, and the second lens 1021 and the third lens 1022 are confocal to form a 4f imaging system; it is used to expand the illumination light beam emitted by the LED 101 by twice; preferably, the collimating lens group 102 includes a second lens 1021 with a focal length of 50nm and a third lens 1022 with a focal length of 100nm.

[0066] The laser excitation unit 2 is used to irradiate a preset area on the surface of the sample to be tested and excite to generate a plasma beam, and includes a nanosecond pulse laser 201, an axle group 202, a second reflector 203 and a second objective lens assembly 204; the nanosecond pulse laser 201 emits nanosecond pulse laser; the nanosecond pulse laser emits a collimated Bessel beam after passing through the axle group 202; the second reflector 203 is used to change the transmission direction of the collimated Bessel beam; the second objective lens assembly 204 focuses the collimated Bessel beam on a preset area on the surface of the sample to be tested, so as to induce the plasma of the sample to be tested to emit light and obtain a sample plasma beam.

[0067] The conical lens group 202 includes a first conical lens 2021 and a second conical lens 2022. The cone angles of the first conical lens 2021 and the second conical lens 2022 are the same, and the cone angles of the first conical lens 2021 and the second conical lens 2022 range from 10° to 30°. The vertex angle of the first conical lens 2021 is arranged relative to the vertex angle of the second conical lens 2022. The conical surfaces of the first conical lens 2021 and the second conical lens 2022 are both odd-order aspherical surfaces, and there are only first-order terms. The first-order coefficients of the conical surfaces of the first conical lens 2021 and the second conical lens 2022 are the same, and the first-order coefficients are between -1 and -0.2. The aperture d2 of the second conical lens 2022 is twice the aperture d1 of the first conical lens 2021. Such an arrangement can prevent the light beam from being cut when passing through the second conical lens. Figure 2 As shown, the inner diameter R1 and the outer diameter R2 of the collimated Bessel light beam emitted by the axicon lens group 202 are related to the cone angle α of the first axicon lens 2021 and the second axicon lens 2022, the distance x between the vertex of the first axicon lens 2021 and the vertex of the second axicon lens 2022, and the diameter r of the incident light beam. Specifically, the smaller the cone angle α, the larger the inner diameter R1 and the outer diameter R2 of the collimated Bessel light beam emitted by the axicon lens group 202; the larger the distance x between the vertex of the first axicon lens 2021 and the vertex of the second axicon lens 2022, the larger the inner diameter R1 and the outer diameter R2 of the collimated Bessel light beam emitted by the axicon lens group 202.

[0068] In a specific embodiment, the cone angle α of the first conical lens 2021 is 20°, and the cone angle α of the second conical lens 2022 is 20°; the distance x between the vertex of the first conical lens 2021 and the vertex of the second conical lens 2022 is 20 mm. The first-order coefficient of the odd-order aspheric surface of the conical surface of the first conical lens 2021 is -0.364, and the first-order coefficient of the odd-order aspheric surface of the conical surface of the second conical lens 2022 is -0.364. The aperture d1 of the first conical lens 2021 is 12.7 mm, and the aperture d2 of the second conical lens 2022 is 25.4 mm. When the incident light beam is a collimated light beam with a diameter of r=2 mm, the inner diameter R1 of the collimated Bessel light beam emitted by the conical lens group 202 is 5.5 mm, and the outer diameter R2 is 7.44 mm.

[0069] Laser-induced breakdown spectroscopy uses a high peak power pulsed laser to irradiate the sample, and the beam is focused to a very small analysis point (usually 10-400 microns in diameter). In the laser irradiation spot area, the material in the sample is ablated and peeled off, and a cloud of nanoparticles is formed above the sample. Since the peak energy of the laser beam is quite high, its absorption and multiphoton ionization effect increase the opacity of the gas and aerosol cloud generated above the sample, even if it is only a very short laser pulse excitation. Since the energy of the laser is significantly absorbed by the cloud, a plasma gradually forms. The high-energy plasma melts the nanoparticles, excites the atoms in them and emits light. The light emitted by the atoms can be captured by the detector and recorded as a spectrum. By analyzing the spectrum, information about what elements are present in the sample can be obtained. The spectrum can be further qualitatively analyzed (such as material identification) and quantitatively analyzed (such as the content of a certain element in the sample) by software algorithms. In actual industrial inspection sites, the surface of the sample to be tested is often rough and uneven, which causes the defocus amount to change and thus causes the collected spectral information to fluctuate, which seriously affects the stability and accuracy of the laser-induced breakdown spectroscopy analysis.

[0070] In a specific embodiment, the second objective lens assembly 204 includes a fourth reflector 2041 and an ultraviolet objective lens 2042, wherein the fourth reflector 2041 is used to direct the collimated Bessel light beam reflected by the second reflector 203 to the ultraviolet objective lens 2042; and the ultraviolet objective lens 2042 is used to focus the collimated Bessel light beam onto the surface of the sample 5 to be tested.

[0071] The laser induced breakdown spectroscopy acquisition device of the present invention uses a pair of conical lenses with opposite apex angles to construct a collimated Bessel beam and focus it on the surface of the sample to be tested. Since the Bessel beam has the characteristics of small main lobe diameter, long focal depth, controllable annular spot, etc., it can improve the tolerance of laser induced breakdown spectroscopy technology to changes in defocus, reduce spectral fluctuations caused by uneven sample surfaces, and thus improve the accuracy of laser induced breakdown spectroscopy technology analysis.

[0072] The spectrum acquisition unit 3 is used to collect spectrum data of the sample plasma beam excited by the laser excitation unit, and includes an open-loop reflector 301, a slit 302, a chirped reflective volume Bragg grating 303, a microlens array 304 and a linear array CCD 305; Figure 3 As shown, Figure 3 (a) is the top view of the open-loop reflector. Figure 3(b) is a cross-sectional view of an open-loop reflector, wherein the open-loop reflector 301 is disposed between the axle lens group 202 and the second reflector 203, and the open-loop reflector 301 has an open-loop region 3011 and a non-open-loop region 3012, wherein the open-loop region 3011 can accommodate the collimated Bessel light beam emitted by the axle lens group 202, and the non-open-loop region 3012 reflects the sample plasma light beam excited by the surface of the sample 5 to be tested; the slit 302 is used to reflect the sample plasma light beam emitted by the open-loop reflector 3011. The sample plasma beam reflected by the mirror 301 is shaped to obtain a linear sample plasma beam; the chirped reflective volume Bragg grating 303 is used to perform narrow-band spectroscopy on the linear sample plasma beam to obtain spectra of multiple different bands; the microlens array 304 focuses the spectra of multiple different bands onto the linear array CCD 305 respectively; the linear array CCD 305 receives intensity information of different wavelengths focused by the microlens array, and the intensity information of different wavelengths is spectral data.

[0073] In a specific embodiment, the radius of the open-loop reflector 301 is D3, and there is an open-loop region with an inner radius of D1 and an outer radius of D2; the thickness of the open-loop reflector 301 is 3 mm.

[0074] Since the width of the halo of the Bessel beam generated by the aconic lens increases with the increase of the transmission distance, it is necessary to adjust the Bessel beam parameters or the optical device parameters according to the position of the optical device when using it in the laser induced breakdown spectroscopy acquisition device of the present system. In order to reduce the difficulty of building the optical path and maintain the stability of the device, the present invention uses a pair of aconic lenses with opposite vertex angles to construct a collimated Bessel beam. It is only necessary to control the width of the Bessel beam so that it matches the width of the open-loop area of ​​the open-loop reflector and is not greater than the entrance pupil diameter of the second objective lens assembly. In the subsequent optical path adjustment process, it is not necessary to make a secondary adjustment.

[0075] In an optional embodiment, the inner diameter D1 of the open-loop region 3011 of the open-loop reflector 301 is not greater than the inner diameter R1 of the collimated Bessel beam emitted by the axle lens group 202, and the outer diameter D2 of the open-loop region 3011 of the open-loop reflector 301 is not less than the outer diameter R2 of the collimated Bessel beam emitted by the axle lens group 202. Preferably, the inner diameter D1 of the open-loop region 3011 of the open-loop reflector 301 is equal to the inner diameter R1 of the collimated Bessel beam emitted by the axle lens group 202, and the outer diameter D2 of the open-loop region 3011 of the open-loop reflector 301 is equal to the outer diameter R2 of the collimated Bessel beam emitted by the axle lens group 202. Such an arrangement can reduce the optical energy loss of the sample plasma beam reflected by the open-loop reflector 301 to a minimum, so that the plasma spectrum utilization efficiency can be improved, thereby improving the signal-to-noise ratio of the entire system.

[0076] Existing laser-induced breakdown spectroscopy equipment usually uses a dichroic mirror with a notch of 355nm, which is used to transmit light near the 355nm bandwidth and reflect the plasma spectrum outside the 355nm wavelength. The dichroic mirror needs to be customized. Due to the process limitations of the dichroic mirror coating with such a large bandwidth of 200-800nm, it is difficult to achieve and the cost is high. In addition, light near the 355nm bandwidth cannot be collected when collecting the plasma spectrum.

[0077] In the laser induced breakdown spectroscopy acquisition device provided by the present invention, an open-loop reflector is used to greatly reduce the attenuation of the intensity of the nanosecond pulse laser used to induce plasma luminescence of the sample to be tested during the transmission process, which is beneficial to inducing plasma luminescence of the sample to be tested; compared with the existing laser induced breakdown spectroscopy equipment using a dichroic mirror, not only the optical path is simplified, but also the full-band collection of the plasma spectrum can be achieved.

[0078] In a specific embodiment, the width of the slit 302 is 10 μm. The present invention adds a slit 302 in front of the chirped reflective volume Bragg grating 303, so that the sample plasma beam reflected by the open-loop reflector 301 becomes linear, thereby matching with the linear array CCD 305 to achieve spectral analysis.

[0079] like Figure 4 As shown, Figure 4 (a) is a side view of the chirped reflective volume Bragg grating 303. Figure 4 (b) is a front view of the chirped reflective volume Bragg grating 303. In a specific embodiment, the chirped reflective volume Bragg grating 303 has a grating diffraction angle of θ, with ∧1, ∧2, ∧3...∧ n Gradual cycle.

[0080] In the present application, the excited plasma spectrum is a wide-band light, and its wavelength ranges from ultraviolet to near infrared. According to the formula λ / ncosθ=2Λ, in this formula, λ is the central wavelength of the incident light, Λ is the grating period, n is the refractive index of the photothermal sensitive refracting glass used to make the chirped reflective volume Bragg grating 303, and θ is the grating diffraction angle.

[0081] For the same incident light wave, the grating periods in different areas are different, and their Bragg angles are also different, which can achieve multi-angle selection; and for multi-wavelength light beams, at the same incident angle, the wavelength selectivity of different areas of the grating is different. A specific area of ​​the grating can only pass a specific wavelength, which can achieve wavelength selection, and the wavelength selection bandwidth is related to the period of the volume Bragg grating. The smaller the period, the smaller the wavelength selection bandwidth, which can be used for narrowband spectroscopy of wide-band light.

[0082] Since the grating period Λ is limited by the process and cannot be reduced to make the splitting bandwidth meet the needs of this application, in order to achieve a smaller bandwidth selection, the present invention increases the grating diffraction angle θ. The grating diffraction angle θ of the present invention is 10°-40°, preferably, the grating diffraction angle θ=30°. It can be seen from the above formula that when the grating period Λ and the refractive index n remain unchanged, the larger θ is, the smaller λ is.

[0083] The existing laser induced breakdown spectroscopy acquisition device uses a spectrometer for spectral analysis. The ordinary spectrometer uses a surface grating, and the outgoing light beam has different inclination angles, resulting in large divergence, requiring multiple concave mirrors for collimation, and a complex structure. In the laser induced breakdown spectroscopy acquisition device of the present invention, a chirped reflective volume Bragg grating 303 is used to replace the complex multi-channel spectrometer structure. The chirped reflective volume Bragg grating 303 has a higher resolution than an ordinary surface grating, and a higher diffraction efficiency, which can reach 99%, which is conducive to improving the signal strength, and the light beams emitted by the chirped reflective volume Bragg grating 303 have the same inclination angle, and no additional collimation is required.

[0084] like Figure 5 As shown, Figure 5 (a) is the front view of the microlens array. Figure 5 (b) is a side view of the microlens array. In a specific embodiment, the radius of curvature of the microlens array is R=50-200 mm. The number of microlenses in the microlens array 304 is 2048-4096. Preferably, the number of microlenses in the microlens array 304 is 2048. The microlens array 304 can be processed by laser direct writing.

[0085] The translation stage 4 of the microlens array is located above the sample to be tested 5, and is used to carry the first objective lens assembly 105 and the second objective lens assembly 204, and drive the first objective lens assembly 105 and the second objective lens assembly 204 to move, so that the first objective lens assembly 105 or the second objective lens assembly 204 is located above the sample to be tested 5, so as to operate the preset area located on the sample to be tested 5, and realize the rapid switching between the first objective lens assembly 105 and the second objective lens assembly 204, thereby improving the test efficiency. In addition, the illumination observation unit and the laser excitation unit of the present invention use different objective lenses, so that the objective lens magnification can be adjusted separately, and the objective lens magnification can be selected according to the actual application scenario. For example, when a wide viewing angle is required to observe the entire sample surface, a lower magnification objective lens is selected; when high resolution is required, a high magnification objective lens is selected; thereby expanding the use scenario.

[0086] The computing unit is used to coordinately control the plasma excitation, plasma spectrum collection, excitation process observation and movement of the translation stage 4 of the entire device, and to process and analyze the collected spectrum data of the sample plasma beam.

[0087] The present invention also provides a laser induced breakdown spectrum acquisition method, which is implemented using the laser induced breakdown spectrum acquisition device as described above, and includes the following steps:

[0088] S1: Control the translation stage so that the first objective lens assembly is located above the sample to be tested.

[0089] S2: Turn on the LED, and the illumination light beam emitted by the LED passes through the collimating lens group and is reflected by the beam splitter to the first reflector. After being reflected by the first reflector, it is focused on the sample to be tested by the first objective lens assembly, and the irradiated area on the sample to be tested is marked as a preset area.

[0090] S3: The light scattered by the preset area passes through the first objective lens assembly and the first reflector in sequence and is then transmitted by the beam splitter. After transmission, the light is focused on the camera by the first lens to form an image.

[0091] S4: Control the translation stage to move the second objective lens assembly above the sample to be tested, and make the light emitted by the second objective lens assembly illuminate a preset area.

[0092] S5: Turn on the nanosecond pulse laser, and the nanosecond pulse laser emitted by the nanosecond pulse laser emits a collimated Bessel beam after passing through the conical lens group. The collimated Bessel beam is reflected by the second reflector and irradiated by the second objective lens assembly to a preset area of ​​the sample to be tested.

[0093] S6: The material in the preset area is ablated and peeled off, and a cloud of nanoparticles is formed above the sample, inducing the plasma therein to emit light, thereby obtaining a sample plasma beam.

[0094] S7: The sample plasma beam passes through the second objective lens assembly and the first reflector in sequence and is reflected by the non-open-loop area of ​​the open-loop reflector. The reflected sample plasma beam is beam shaped by the slit to obtain a linear sample plasma beam.

[0095] S8: The linear sample plasma beam is reflected by the chirped reflective volume Bragg grating and then focused on the linear array CCD by the microlens array.

[0096] S9: The linear array CCD collects the intensity information of different wavelengths of the linear sample plasma beam after being focused by the microlens array, the intensity information of different wavelengths is spectral data, and transmits the spectral data to the calculation unit.

[0097] S10: The computing unit processes and analyzes the spectral data, thereby achieving qualitative and quantitative analysis of the sample to be tested.

[0098] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A laser induced breakdown spectroscopy acquisition device, characterized in that: include: An illumination observation unit, used to provide a field of view for laser-induced breakdown spectroscopy acquisition; The illumination observation unit comprises a first objective lens assembly, and the first objective lens assembly is used to image the field of view; A laser excitation unit, used for irradiating a preset area on the surface of the sample to be tested and exciting and generating a sample plasma beam; the laser excitation unit comprises a nanosecond pulse laser, an aconical lens group, a second reflector and a second objective lens assembly; The nanosecond pulse laser emits nanosecond pulse laser, and the nanosecond pulse laser emits a collimated Bessel beam after passing through the axle lens group. The second reflector is used to change the transmission direction of the collimated Bessel beam. The second objective lens assembly focuses the collimated Bessel beam on a preset area on the surface of the sample to be tested, and excites a sample plasma beam. A spectrum acquisition unit is used to collect spectrum data of the sample plasma beam excited by the laser excitation unit; the spectrum acquisition unit includes an open-loop reflector, a slit, a chirped reflective volume Bragg grating, a microlens array and a linear array CCD; the open-loop reflector is arranged between the axle lens group and the second reflector, the open-loop reflector has an open-loop area and a non-open-loop area, the open-loop area can accommodate the collimated Bessel beam emitted by the axle lens group to pass through, the non-open-loop area reflects the sample plasma beam excited by the surface of the sample to be tested, the slit is used to shape the sample plasma beam reflected by the open-loop reflector to obtain a linear sample plasma beam, the chirped reflective volume Bragg grating is used to perform narrow-band spectroscopy on the linear sample plasma beam to obtain multiple spectra of different wavelengths, the microlens array focuses the multiple spectra of different wavelengths respectively, the linear array CCD receives intensity information of different wavelengths focused by the microlens array, and the intensity information of different wavelengths is spectrum data; A translation stage, located above the sample to be tested, for carrying the first objective lens assembly and the second objective lens assembly and driving the first objective lens assembly and the second objective lens assembly to move above the sample to be tested, so that the illumination observation unit or the laser excitation unit acts on the preset area; The computing unit is used to coordinately control the plasma excitation, plasma spectrum collection, excitation process observation and movement of the translation stage of the entire device, and to process and analyze the spectrum data of the collected sample plasma beam.

2. The laser induced breakdown spectroscopy acquisition device according to claim 1, characterized in that: The lighting observation unit comprises: LED, the LED is used to provide an illumination beam; A collimating lens group, wherein the collimating lens group is used to collimate the illumination light beam to obtain a collimated illumination light beam; A beam splitter, which reflects the collimated illumination light beam once; a first reflector, wherein the first reflector performs secondary reflection on the collimated illumination light beam; A first objective lens assembly, the first objective lens assembly is used to focus the collimated illumination light beam on a preset area on the surface of the sample to be tested; A first lens, wherein the light scattered by the surface of the sample to be tested is sequentially collimated by the first objective lens assembly and reflected by the first reflector and then transmitted by the beam splitter, and the first lens is used to focus the light transmitted by the beam splitter; A camera receives the light beam focused by the first lens.

3. The laser induced breakdown spectroscopy acquisition device according to claim 2, characterized in that: The collimating lens group includes a second lens and a third lens, the focal length of the third lens is twice that of the second lens, and the second lens and the third lens are co-focal to form a 4f imaging system.

4. The laser induced breakdown spectroscopy acquisition device according to claim 2, characterized in that: The first objective lens assembly includes a third reflector and an imaging objective lens. The third reflector is used to direct the collimated illumination light beam reflected by the first reflector into the imaging objective lens. The imaging objective lens is used to focus the collimated illumination light beam onto the surface of the sample to be tested.

5. The laser induced breakdown spectroscopy acquisition device according to claim 1, characterized in that: The conical lens group includes a first conical lens and a second conical lens, the vertex angle of the first conical lens is arranged opposite to the vertex angle of the second conical lens, the conical angle range of the first conical lens and the second conical lens is 10°-30°, the conical angles of the first conical lens and the second conical lens are the same, and the aperture of the second conical lens is twice the aperture of the first conical lens.

6. The laser induced breakdown spectroscopy acquisition device according to claim 1, characterized in that: The second objective lens assembly includes a fourth reflector and an ultraviolet objective lens. The fourth reflector is used to allow the collimated Bessel light beam reflected by the second reflector to be incident on the ultraviolet objective lens. The ultraviolet objective lens is used to focus the collimated Bessel light beam on the surface of the sample to be tested.

7. The laser induced breakdown spectroscopy acquisition device according to claim 1, characterized in that: The inner diameter D1 of the open-loop region of the open-loop reflector is not larger than the inner diameter R1 of the collimated Bessel beam emitted by the axle lens group, and the outer diameter D2 of the open-loop region of the open-loop reflector is not smaller than the outer diameter R2 of the collimated Bessel beam emitted by the axle lens group.

8. The laser induced breakdown spectroscopy acquisition device according to claim 1, characterized in that: The grating diffraction angle of the chirped reflective volume Bragg grating is θ=10°-40°.

9. The laser induced breakdown spectroscopy acquisition device according to claim 1, characterized in that: The curvature radius of the microlens array is 50-200 mm.

10. A method for collecting laser induced breakdown spectroscopy, characterized in that: The method is implemented by using the laser induced breakdown spectroscopy acquisition device as described in any one of claims 2 to 9, comprising the following steps: S1: Control the translation stage so that the first objective lens assembly is located above the sample to be tested; S2: Turn on the LED, and the illumination light beam emitted by the LED passes through the collimating lens group and is reflected by the beam splitter to the first reflector. After being reflected by the first reflector, it is focused on the sample to be tested by the first objective lens assembly, and the irradiated area on the sample to be tested is marked as a preset area; S3: The light scattered by the preset area passes through the first objective lens assembly and the first reflector in sequence, and is then transmitted by the beam splitter. After transmission, the light is focused on the camera by the first lens to form an image; S4: controlling the translation stage to move the second objective lens assembly to above the sample to be tested, and allowing the light emitted by the second objective lens assembly to irradiate a preset area; S5: Turn on the nanosecond pulse laser, and the nanosecond pulse laser emitted by the nanosecond pulse laser emits a collimated Bessel beam after passing through the axle lens group. The collimated Bessel beam is reflected by the second reflector and irradiated by the second objective lens assembly to a preset area of ​​the sample to be tested; S6: The material in the preset area is ablated and peeled off, and a cloud of nanoparticles is formed above the sample, inducing plasma luminescence to obtain a sample plasma beam; S7: the sample plasma beam passes through the second objective lens assembly and the first reflector in sequence and is reflected by the non-open-loop region of the open-loop reflector. The reflected sample plasma beam is beam shaped by the slit to obtain a linear sample plasma beam. S8: the linear sample plasma beam is reflected by the chirped reflective volume Bragg grating and then focused on the linear array CCD by the microlens array; S9: the linear array CCD collects intensity information of different wavelengths of the linear sample plasma beam after being focused by the microlens array, the intensity information of different wavelengths being spectral data, and transmits the spectral data to a computing unit; S10: The computing unit processes and analyzes the spectral data, thereby achieving qualitative and quantitative analysis of the sample to be tested.

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