CN107884339B - Adaptive laser spectrum suitable for deep space micro-area analysis and imaging method - Google Patents

Abstract

The invention discloses an adaptive laser spectrum and imaging method suitable for deep space micro-area analysis. The method is realized on an adaptive laser spectrum and imaging detection system, and the method includes the expected focal spot adaptive focusing calibration, There are five steps: single-point tight focusing of the detection object, Raman fluorescence and imaging information acquisition, Raman fluorescence imaging scanning micro-area analysis, LIBS scanning micro-area analysis and information fusion. The beneficial effect of the present invention is to provide an adaptive laser spectrum and imaging detection method, which can adaptively adjust the diameter of the focusing spot during micro-area analysis; It meets the requirements of self-focusing and wide-spectrum scanning imaging; it can simultaneously realize three-dimensional space LIBS elemental analysis, active laser Raman molecular analysis, hyperspectral fluorescence, and visible wide-spectrum scanning imaging, providing a variety of information for fine detection of micro-area.

Description

An adaptive laser spectroscopy and imaging method suitable for deep space micro-analysis

technical field

The invention relates to a substance detection method, in particular to a substance detection method using scanning laser-induced plasma LIBS, laser Raman imaging, laser-induced fluorescence imaging and laser illumination surface array wide-spectrum scanning imaging, which is suitable for deep space exploration of planets Material detection in an open environment belongs to the field of planetary in-situ detection.

Background technique

For future deep space exploration, higher requirements are put forward for the detection technology and method of material composition. Fine detection requires a smaller laser focus point, a small amount of material to be analyzed, a richer variety of elements and molecules, and a more accurate quantification, while monitoring with extremely high spatial resolution imaging.

Laser Induced Plasma Spectroscopy (LIBS), Laser Raman (Raman) and UV Laser Induced Fluorescence are important means of material composition analysis. Among them, LIBS can realize the analysis of material composition elements, laser Raman can realize the analysis of material molecular composition, and UV laser can realize the analysis of material composition elements. Besides imaging, induced fluorescence can also be used for the analysis of some elements, especially rare earth elements. LIBS and Raman material analysis in deep space micro-area detection have higher requirements than conventional laser spectroscopy applications. The main challenges and technical difficulties are that due to the complex composition of minerals contained in the rocks and soils of the test objects, the same mineral particles Diameter is very small. Therefore, in micro-area analysis, the laser focusing spot is required to be on the order of 1 micron, in order to carry out accurate micro-area analysis of minerals, and the requirements for the microscopic optical path are extremely high. The conventional Raman probe is affected by the optical fiber transmission mode, its focusing The light spot is affected by the degradation of the laser mode and the diffraction limit, so the focusing spot is often larger than 5 microns, which cannot meet the requirements; the combination of free light path, short wavelength laser and high magnification and high numerical aperture microscope objective can theoretically obtain extremely Small focusing spot, but because the focusing depth of field is extremely small, it is necessary to find a suitable self-focusing solution for micro-analysis 3D structure analysis, and ensure that the focusing spot size of each point is consistent and consistent with the design value. At the same time, if the self-focusing time long, the scanning imaging speed will be affected. Therefore, a simple and fast Raman self-focusing and wide-spectrum scanning imaging method is required. In addition, for the compact optical path of the system, LIBS and Raman detection must also reuse most of the optical components.

In view of the above requirements for laser spectral detection and imaging in micro-area in deep space, the present invention proposes a substance detection method using scanning LIBS, scanning laser Raman imaging, scanning laser-induced fluorescence imaging and area array broad-spectrum scanning imaging, which is suitable for deep space detection The micro-area material detection in the open environment of the planet can obtain the three-dimensional morphology of the micro-area and the corresponding distribution of atoms, molecules and rare earth fluorescent substances.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a deep space micro-area adaptive laser spectrum and imaging detection method, which can accurately obtain the required constant focusing spot size, and obtain the microscopic image of the detection object at the same time as the LIBS and Raman fluorescence spectral distribution detection. The three-dimensional morphology of the micro-area can meet the needs of in-situ material analysis in the micro-area.

The adaptive laser spectrum and imaging detection method proposed by the present invention is realized on the adaptive laser spectrum and imaging detection system. device and optical head;

The optical head consists of LIBS laser, LIBS cut-in total mirror, cut-in controller, ultraviolet Raman laser, ultraviolet interference filter, secondary motor driver, secondary linear motorized stage, low magnification ultraviolet microscope objective lens, dichroic mirror, Long working distance high magnification UV microscope objective lens, main motor driver, main linear motor stage, UV Rayleigh filter, proportional beam splitter, microscope objective lens, tube lens and electronic eyepiece; the electronic eyepiece has imaging lens and image sensor;

The pulsed LIBS laser beam emitted by the LIBS laser along the LIBS optical axis has the same initial beam diameter and the same extremely small divergence angle as the continuous laser beam emitted by the ultraviolet Raman laser along the main optical axis; when in the non-LIBS working mode, the switch-in control The controller cuts the LIBS into the total reflection mirror and cuts out the main optical axis; when in the LIBS working mode, the switch-in controller cuts the LIBS into the total reflection mirror into the main optical axis. At this time, the output ports of the LIBS laser and the ultraviolet Raman laser are sent to the LIBS The distances cut into the total reflection mirror are equal, and the pulsed LIBS laser beam emitted by the LIBS laser along the LIBS optical axis is cut into the total reflection mirror by the LIBS, and then enters the main optical axis for transmission, forming a cylindrical nearly collimated laser beam passing through the low magnification ultraviolet display. Micro-objective lens, after forming a cone-shaped laser beam and passing through the dichroic mirror, it is focused to the detection target by the long working distance high-power ultraviolet microscope objective lens, and the LIBS echo signal passes through the long working distance high-power ultraviolet microscope objective lens along the main optical axis in the reverse direction. After mirror reflection, it travels along the receiving optical axis, and reaches the proportional beam splitter and divides into two orthogonal paths: one path travels along the imaging optical axis after reflection, and this signal is not used in LIBS mode; the other path passes through the proportional beam splitter and passes through the ultraviolet The Rayleigh filter filters out the Rayleigh scattering at the wavelength of the LIBS laser, and then is focused on the incident end face of the optical fiber by the microscope objective lens, and then enters the spectrometer for analysis; the digital pulse delay controller has two control ends, which are respectively connected to the LIBS laser The external trigger port of the spectrometer; the digital pulse delay controller is used to set the operating frequency of the LIBS laser and the opening delay between the LIBS laser and the spectrometer;

The laser beam emitted by the UV Raman laser along the main optical axis passes through the UV interference filter, which can filter out the frequency division harmonic interference of the UV laser emitted by the UV Raman laser, so that the Raman signal excited by it has a higher signal-to-noise ratio. ; The formed cylindrical near-collimated laser beam passes through the low-power UV microscope objective to form a cone-shaped laser beam; after the cone-shaped laser beam passes through the dichroic mirror, it reaches the entrance pupil of the long-working distance high-power UV microscope objective. At the position of the pupil, the diameter of the conical laser beam will be larger than the diameter of the entrance pupil. Since the cone angle of the conical laser beam is a fixed value, the farther the distance between the low-power UV microscope objective and the long working distance high-power UV microscope objective is , the larger the diameter of the cone laser beam is than the diameter of the entrance pupil, the weaker the laser energy passing through the long working distance high magnification UV microscope objective, but the smaller the focused spot; therefore, by adjusting the low magnification UV microscope objective and the The distance of the long working distance high power UV microscope objective lens is a trade-off between the laser energy passing through the long working distance high power UV microscope objective lens and the size of the focused spot, that is, a large spot with large energy, a small spot with small energy; the echo signal is reversed It passes through the long working distance high-power ultraviolet microscope objective along the main optical axis, travels along the receiving optical axis after being reflected by the dichroic mirror, and then divides into two orthogonal paths after reaching the proportional beam splitter: one travels along the imaging optical axis after reflection, and is focused by the tube lens to Between one and two times the focal length of the imaging lens in the electronic eyepiece, an enlarged real image is sent to the image sensor through the imaging lens; after the other way passes through the proportional beam splitter, the ultraviolet Rayleigh filter converts the wavelength of the ultraviolet Raman laser. After the Rayleigh scattering is filtered out, it is focused to the incident end face of the optical fiber by the microscope objective lens, and then enters the spectrometer for analysis; The main optical axis performs one-dimensional precision translation; the long working distance high-power ultraviolet microscope objective lens is installed on the main linear motorized stage, which can be driven by the main motor driver for one-dimensional precision translation along the main optical axis; the secondary linear motorized stage The translation is mainly used to change the distance between the low-power UV microscope objective and the long working distance high-power UV microscope objective; the translation of the main linear motorized stage is mainly used to make the long working distance high-power UV microscope objective focus accurately; LIBS optical axis , the main optical axis, the imaging optical axis, and the receiving optical axis are coplanar; the main optical axis is parallel to the imaging optical axis, and perpendicular to the LIBS optical axis and the receiving optical axis;

The optical head is installed on the 3D precision electric platform, and the 3D precision electric platform can perform sub-micron 3D precision motion under the drive of the 3D motor driver;

The main controller can send control commands to the cut-in controller, digital pulse delay controller, three-dimensional motor driver, main motor driver, secondary motor driver, ultraviolet Raman laser, image sensor, and spectrometer; the main controller also sets the exposure time of the spectrometer , and can receive the output digital image of the image sensor and the output spectral information of the spectrometer;

The adaptive laser spectrum and imaging detection method proposed by the present invention includes the following steps:

(1) Adaptive focus calibration of expected focal spot

In the in situ detection of deep space matter, different scales of Raman focal points are required for different detection objects, that is, the expected focal spot. For example, for minerals with a relatively uniform distribution, a slightly larger expected focal spot can be used; A large amount of minerals can be used with an expected focal spot of extremely small size to achieve extremely fine micro-analysis;

First, set the diameter of the expected focal spot according to the basic properties of the detection object in the test area; place the measurement reticle in the test area under the long working distance high-power UV microscope objective; the measurement reticle has uniform scribe lines;

The main controller controls to turn on the ultraviolet Raman laser, and the ultraviolet laser beam emitted by it passes through the ultraviolet interference filter, the low-power ultraviolet microscope objective lens, the dichroic mirror in turn, and then is illuminated by the long working distance high-power ultraviolet microscope objective lens and focused to the measurement The reticle forms a real-time focal spot; the reflected light from the measurement reticle passes through the long working distance high-power ultraviolet microscope objective lens along the main optical axis in the reverse direction, is reflected by the dichroic mirror, and then is reflected by the proportional beam splitter, and is focused by the tube lens. Then real-time microscopic imaging to the image sensor through the imaging lens;

The main controller receives the microscopic digital image output by the image sensor and performs real-time image processing; the edge extraction algorithm is used to obtain the outer circle outline of the real-time focal spot, so as to determine the imaging area of the real-time focal spot, and calculate the average gray level of all pixels in the imaging area. value G;

The main controller sends an instruction to the main motor driver to drive the main linear electric platform to move down by one step; the main controller receives the microscopic digital image output by the image sensor, determines the imaging area of the real-time focal spot, and calculates the imaging area of all pixels in the imaging area. Average the gray value G, and compare whether the G value increases or decreases: if the G value increases, it means that the downward movement is in the direction of approaching the focus; if the G value decreases, it means that the upward movement is in the direction of approaching the focus;

The main controller sends an instruction to the main motor driver to drive the main linear electric platform to move in the direction close to the focus, and at the same time calculate the average gray value G of all pixels in the imaging area of the real-time focal spot until the G value reaches the maximum value. In the tight focusing state, the main controller sends an instruction to the main motor driver to stop the movement;

In the tight focus state, the main controller uses the edge extraction algorithm to obtain the straight line position of the reticle of the measurement reticle and the real-time outer circle outline of the focal spot, and then calculates the distance between the adjacent reticle. The number of pixels and the number of pixels of the diameter of the outer circle of the real-time focal spot, so as to calculate the diameter of the real-time focal spot according to the spacing of the reticle;

If the diameter of the real-time focal spot is larger than that of the expected focal spot, the main controller sends an instruction to the secondary motor driver to drive the secondary linear motor platform to move upward, adding a low-power UV microscope objective lens and a long working distance high-power UV microscope objective lens At this time, the laser energy passing through the long working distance high-power ultraviolet microscope objective lens is weakened, but the real-time focal spot is reduced until the diameter of the real-time focal spot is equal to the diameter of the expected focal spot, and the main controller sends an instruction to the secondary motor. The driver stops the movement of the secondary linear electric platform;

Similarly, if the diameter of the real-time focal spot is smaller than the diameter of the expected focal spot, the main controller sends an instruction to the secondary motor driver to drive the secondary linear motor stage to move down, reducing the low-power UV microscope objective and the long working distance. The distance of the high-power ultraviolet microscope objective lens, at this time, the laser energy passing through the long working distance high-power ultraviolet microscope objective lens increases, and the real-time focal spot increases until the diameter of the real-time focal spot is equal to the diameter of the expected focal spot, and the main controller sends out Instruct the secondary motor driver to stop the movement of the secondary linear electric platform;

(2) Single-point tight focusing of the detection object

Remove the measuring reticle, and move the adaptive Raman fluorescence imaging combined system into the actual test area. At this time, the detection object is located under the optical head, and the distance from the long working distance high-power ultraviolet microscope objective lens is much greater than its focal length;

The main controller controls to turn on the ultraviolet Raman laser, and the ultraviolet laser beam emitted by it passes through the ultraviolet interference filter, the low-power ultraviolet microscope objective lens and the dichroic mirror in turn, and then defocuses to the detection object through the long working distance high-power ultraviolet microscope objective lens. On the surface, the reflected light passes through the long working distance high-power ultraviolet microscope objective lens along the main optical axis in the reverse direction, is reflected by the dichroic mirror, then reflected by the proportional beam splitter, focused by the tube lens, and then imaged by the imaging lens to the image sensor in real time; The main controller receives the microscopic digital image output by the image sensor, and performs fast Fourier transform to extract its high-frequency component H;

The main controller sends an instruction to the 3D motor driver to drive the optical head on the 3D precision electric platform to move down along the Z axis. At this time, the distance between the detection object and the long working distance high-power ultraviolet microscope objective lens decreases. The main controller continuously performs fast Fourier transform on the microscopic digital image output by the image sensor in real time, and continuously extracts its high-frequency component H until H reaches the maximum value. The spot size is equal to the expected focal spot size, and it is in a tight focus state;

(3) Raman fluorescence and imaging information acquisition

In this tight focusing state, the main controller records the three-dimensional displacement of the three-dimensional precision motorized stage and sets it as the initial three-dimensional coordinates (x ₁ , y ₁ , z ₁ ); the main controller receives the microscopic digital output from the image sensor image, using edge extraction algorithm to obtain the outer circle contour of real-time focal spot, so as to determine the imaging area of real-time focal spot, and calculate the average gray value g ₁ of all pixels in the imaging area; The upward scattering passes through the long working distance high-power ultraviolet microscope objective along the main optical axis, is reflected by the dichroic mirror, and after passing through the proportional beam splitter, the Rayleigh scattering at the wavelength of the ultraviolet Raman laser is filtered out by the ultraviolet Rayleigh filter. Then it is focused to the incident end face of the optical fiber through the microscope objective lens, and then enters the spectrometer. The spectrometer outputs the spectral signal to the main controller for analysis; the main controller first extracts n discrete Raman spectral lines λ ₁ , λ ₂ of the spectral signal, _{λ 3 , . _ _} Fluorescence spectrum mean intensity J ₁₁ , J ₁₂ , J ₁₃ , ..., J _1m ;

(4) Micro-area analysis of Raman fluorescence imaging scanning

The main controller determines the number of scanning points A and B in the XY direction of the micro-area analysis, and the scanning step lengths C and D; the main controller sends an instruction to the 3D motor driver to drive the optical head on the 3D precision electric platform to make an S shape on the XY plane Scan, for each point on the XY plane, move up and down along the Z axis, and perform the single-point tight focusing of step (2);

For each scanning point i (i is greater than or equal to 2, until i is equal to A×B), in the tight focusing state of this point, the main controller records the three-dimensional displacement of the three-dimensional precision electric platform, and determines its three-dimensional coordinates (x _i , y _i , z _i ); the main controller receives the microscopic digital image output by the image sensor, adopts the edge extraction algorithm to obtain the real-time focal spot outer circle contour, thereby determines the real-time focal spot imaging area, and calculates the average gray value of all pixels in the imaging area. Degree value g _i ; the main controller records the spectral line intensities Ι _i1 , Ι _i2 , Ι _i3 ,..., Ι _in of n discrete Raman spectral lines λ ₁ , λ ₂ , λ ₃ ,..., λ _n ; And record the average intensity of fluorescence spectrum J _i1 , J _i2 , J _i3 ,...,J _im of each segment of the m-segment fluorescence spectrum;

The main controller first integrates the three-dimensional coordinates of the A×B scanning points, and draws the three-dimensional geometry of the surface of the detection object in the scanning area; then, integrates the g ₁ , g ₂ ,..., _gi ,... , the grayscale image of the three-dimensional geometry of the surface of the detection object can be obtained; then, by synthesizing the I ₁₁ , I ₂₁ ,...,I _i1 ,... of each scanning point, the wavelength of the surface of the detection object is λ ₁ Similarly, I ₁₂ , I ₂₂ ,...,I _i2 ,... of each scanning point are integrated to obtain a Raman image with a wavelength of λ ₂ on the surface of the detection object,..., until the The Raman image with wavelength λ _n of the surface of the detection object is obtained; finally, J ₁₁ , J ₂₁ ,...,J _i1 ,... of each scanning point are integrated to obtain the fluorescence image of the first spectral band of the surface of the detection object , similarly, combine J ₁₂ , J ₂₂ ,...,J _i2 ,... of each scanning point to obtain the fluorescence image of the second spectral band on the surface of the detection object,..., until the surface of the detection object is obtained The fluorescence image of the mth spectral band;

(5) LIBS scanning micro-area analysis and information fusion

The main controller sends an instruction to the cut-in controller to cut the LIBS into the total mirror into the main optical axis; the main controller sends an instruction to set the exposure time of the spectrometer; the main controller sends an instruction to the digital pulse delay controller to set the LIBS laser The operating frequency of the LIBS laser and the turn-on delay between the LIBS laser and the spectrometer;

The main controller sends an instruction to the 3D motor driver to drive the optical head on the 3D precision electric platform to scan in the opposite direction to step (4) according to the recorded 3D coordinates of the A×B scanning points, that is, reverse S-shaped scanning, and reverse scanning. To complete the scan points A × B;

For each scanning point, carry out LIBS detection for a single point for 1 second, the main controller receives the output LIBS spectral information of the spectrometer, and analyzes the element composition and content of the point qualitatively and quantitatively according to the relationship between the spectral line position and intensity, until the completion Micro-LIBS analysis of the entire A×B point;

Fusion with step (4) information to complete the micro-area laser spectrum and imaging analysis, that is, to obtain the three-dimensional topography distribution of the micro-area, the broad-spectrum image of A×B scanning points on the three-dimensional topography distribution, and the ultraviolet light of n wavelengths. Laser Raman images, UV laser-induced fluorescence hyperspectral images of m spectral bands, and element distribution images.

The beneficial effect of the present invention is to provide an adaptive laser spectrum and imaging detection method, which can adaptively adjust the diameter of the focusing spot during micro-area analysis; It meets the requirements of self-focusing and wide-spectrum scanning imaging; it can simultaneously realize three-dimensional space LIBS elemental analysis, active laser Raman molecular analysis, hyperspectral fluorescence, and visible wide-spectrum scanning imaging, providing a variety of information for fine detection of micro-area.

Description of drawings

1 is a schematic diagram of the system structure of the present invention, in the figure: 1—three-dimensional motor driver; 2—optical head; 3—ultraviolet Raman laser; 4—main optical axis; 5—ultraviolet interference filter; 6—secondary motor driver; 7—main controller; 8—low power ultraviolet microscope objective lens; 9—secondary linear motorized stage; 10—imaging optical axis; 11—electronic eyepiece; 12— Spectrometer; 13—fiber; 14—microscopic objective lens; 15—receiving optical axis; 16—ultraviolet Rayleigh filter; 17—proportional beam splitter; 18—real-time focal spot; 19—expected focus Spot; 20—scribed line; 21—main motor driver; 22—main linear motorized stage; 23—detection object; 24—measurement reticle; 25—long working distance high power ultraviolet microscope objective lens; 26 - entrance pupil; 27 - dichroic mirror; 28 - cone laser beam; 29 - three-dimensional precision motorized platform; 30 - cylindrical near-collimated laser beam; 31 - image sensor; 32 - imaging lens; 33 - tube lens; 34 - LIBS cut-in total mirror; 35 - LIBS laser beam; 36 - cut-in controller; 37 - LIBS optical axis; 38 - LIBS laser; 39 - digital pulse delay controller .

Note: LIBS, laser-induced spectroscopy, laser-induced breakdown spectroscopy.

Detailed ways

The specific embodiment of the present invention is shown in FIG. 1 .

The adaptive laser spectrum and imaging detection method proposed by the present invention is implemented on an adaptive laser spectrum and imaging detection system, which consists of a main controller 7 , a spectrometer 12 , an optical fiber 13 , a three-dimensional motor driver 1 , and a three-dimensional precision electric platform 29 . The digital pulse delay controller 39 is composed of the optical head 2;

The optical head 2 consists of a LIBS laser 38, a LIBS cut-in total mirror 34, a cut-in controller 36, an ultraviolet Raman laser 3, an ultraviolet interference filter 5, a secondary motor driver 6, a secondary linear motor stage 9, and a low magnification UV microscope objective 8, dichroic mirror 27, long working distance high magnification UV microscope objective 25, main motor driver 21, main linear motor stage 22, UV Rayleigh filter 16, proportional beam splitter 17, microscope objective 14, tube The lens 33 is composed of the electronic eyepiece 11; the electronic eyepiece 11 has an imaging lens 32 and an image sensor 31;

The pulsed LIBS laser beam 35 emitted by the LIBS laser 38 along the LIBS optical axis 37 and the ultraviolet Raman laser 3 (this embodiment is a 360nm, 50mW continuous laser) the continuous laser along the main optical axis 4 has the same initial beam diameter and the same extremely small divergence angle; The cut-in total reflection mirror 34 cuts out the main optical axis 4; when in the LIBS working mode, the cut-in controller 36 cuts the LIBS into the total reflection mirror 34 into the main optical axis 4, at this time, the LIBS laser 38 and the ultraviolet Raman laser 3 are connected. The distances from the output port to the LIBS cut-in total reflection mirror 34 are equal, and the pulsed LIBS laser beam 35 emitted by the LIBS laser 38 along the LIBS optical axis 37 is completely reversed by the LIBS cut-in total reflection mirror 34, and then enters the main optical axis 4 for transmission, forming a cylindrical shape. The collimated laser beam 30 passes through the low-power ultraviolet microscope objective lens 8 to form a cone-shaped laser beam 28 and passes through the dichroic mirror 27 (in this embodiment, 355-360nm high transmission, 220-350 and 364nm-900nm high reflection), The long working distance high magnification ultraviolet microscope objective lens 25 (this embodiment adopts the infinite compound plan aberration ultraviolet 100X microscope objective lens, the ultra-long working distance is 11mm) is focused to the detection target, and the LIBS echo signal is reversed along the main optical axis 4. After passing through the long working distance high-power ultraviolet microscope objective lens 25, the dichroic mirror 27 travels along the receiving optical axis 15 after reflection, and reaches the proportional beam splitter 17 (this embodiment is a 9 to 1 proportional beam splitter, that is, through 9 to 1) and then divided into Two orthogonal paths: one path travels along the imaging optical axis 10 by reflection, and the signal of this path is not used in LIBS mode; the other path passes through the proportional beam splitter 17 and passes through the ultraviolet Rayleigh filter 16 (in this embodiment, the wavelength is 355 -360nm band-stop Rayleigh filter) to filter out the Rayleigh scattering at 38 wavelengths of the LIBS laser, then focus to the incident end face of the optical fiber 13 through the microscope objective lens 14, and then enter the spectrometer 12 (the spectrometer in this embodiment is divided into two The first channel is 220-350nm, the optical resolution is 0.1nm, and the effective pixels are 1000 points; the detection spectral range of the second channel is 360-750nm, the optical resolution is 0.1nm, and the number of effective pixels is 2000 points; LIBS mode Both channels are used, and only the second channel is used for Raman and fluorescence detection) for analysis; the digital pulse delay controller 39 has two control terminals, which are respectively connected to the external trigger ports of the LIBS laser 38 and the spectrometer 12; digital pulse delay control The device 39 is used to set the operating frequency of the LIBS laser 38 and the delay time between the LIBS laser 38 and the spectrometer 12 being turned on;

The laser beam emitted by the ultraviolet Raman laser 3 along the main optical axis 4 passes through the ultraviolet interference filter 5 (the ultraviolet interference filter 5 is an ultraviolet narrow-band filter, this embodiment is 360nm, and the bandwidth is a bandpass filter of 1nm. It can filter out the frequency division harmonic interference of the ultraviolet laser emitted by the ultraviolet Raman laser 3, so that the Raman signal excited by it has a higher signal-to-noise ratio, and the formed cylindrical nearly collimated laser beam 30 passes through the low magnification The ultraviolet microscope objective lens 8 forms a cone-shaped laser beam 28; after the cone-shaped laser beam 28 passes through the dichroic mirror 27, it reaches the entrance pupil 26 of the long working distance high-power ultraviolet microscope objective lens 25. The diameter of the laser beam 28 will be greater than the diameter of the entrance pupil 26. Since the cone angle of the conical laser beam 28 is a fixed value, the farther the distance between the low-power ultraviolet microscope objective 8 and the long working distance high-power ultraviolet microscope objective 25, the greater the cone angle. The larger the diameter of the shaped laser beam 28 is than the diameter of the entrance pupil 26, the weaker the laser energy passing through the long working distance high-power ultraviolet microscope objective 25, but the smaller the focused spot; therefore, the low-power ultraviolet microscope objective can be adjusted by adjusting 8. The distance from the long working distance high power ultraviolet microscope objective lens 25 is a trade-off between the laser energy passing through the long working distance high power ultraviolet microscope objective lens 25 and the size of the focusing spot, that is, the large energy spot is large, and the small energy small spot; The wave signal reversely passes through the long working distance high-power ultraviolet microscope objective lens 25 along the main optical axis 4, and travels along the receiving optical axis 15 after being reflected by the dichroic mirror 27 to reach the proportional beam splitter 17 (this embodiment is a 9 to 1 proportional beam splitter, That is, it is divided into two orthogonal paths after penetrating 9 inverse 1): one path travels along the imaging optical axis 10 through reflection, and is focused by the tube lens 33 to between one to two times the focal length of the imaging lens 32 in the electronic eyepiece 11, and then passes through the imaging lens. 32. The enlarged real image is sent to the image sensor 31 (this embodiment uses a black and white area array sensor, and its response band is 350 to 800 nanometers); after the other way passes through the proportional beam splitter 17, the ultraviolet rays are pulled by the ultraviolet Rayleigh filter 16. After the Rayleigh scattering of the wavelength of the Mann laser 3 is filtered out, it is then focused to the incident end face of the optical fiber 13 by the microscope objective lens 14, and then enters the spectrometer 12 for analysis; the low-power ultraviolet microscope objective lens 8 is installed on the secondary linear motorized stage 9, One-dimensional precision translation can be made along the main optical axis 4 under the driving of the secondary motor driver 6; The main optical axis 4 performs one-dimensional precise translation; the translation of the secondary linear electric stage 9 is mainly used to change the distance between the low-power ultraviolet microscope objective 8 and the long working distance high-power ultraviolet microscope objective 25; The translation is mainly used to make the long working distance high power ultraviolet microscope objective lens 25 focus accurately; the LIBS optical axis 37, the main optical axis 4, the imaging optical axis 10, and the receiving optical axis 15 are coplanar; the main optical axis 4 and the imaging optical axis are coplanar 10 is parallel and perpendicular to the LIBS optical axis 37 and the receiving optical axis 15;

The optical head 2 is installed on the three-dimensional precision electric platform 29, and the three-dimensional precision electric platform 29 can perform sub-micron three-dimensional precision motion under the drive of the three-dimensional motor driver 1;

The main controller 7 can send control commands to the cut-in controller 36, the digital pulse delay controller 39, the three-dimensional motor driver 1, the main motor driver 21, the secondary motor driver 6, the ultraviolet Raman laser 3, the image sensor 31, and the spectrometer 12; The main controller 7 also sets the exposure time of the spectrometer 12, and can receive the output digital image of the image sensor 31 and the output spectral information of the spectrometer 12;

The adaptive laser spectrum and imaging detection method proposed by the present invention includes the following steps:

(1) Adaptive focus calibration of expected focal spot

In the in-situ detection of deep space matter, different scales of Raman focal points are required for different detection objects 23, that is, the expected focal spot 19. For example, for minerals with a relatively uniform distribution, a slightly larger size of the expected focal spot 19 can be used; For more variable minerals, a very small expected focal spot19 can be used to enable very fine microanalysis;

First, for the basic properties of the detection object 23 according to the test area, set the diameter of the expected focal spot 19 (in this embodiment, for olivine minerals, the diameter of the expected focal spot 19 is set to be 1.7 microns); the reticle 24 will be measured Placed in the test area below the long working distance high-power ultraviolet microscope objective lens 25; there is a uniform scribe line 20 on the measurement reticle 24 (the reticle spacing used in this embodiment is 10 microns);

The main controller 7 controls to turn on the ultraviolet Raman laser 3, and the ultraviolet laser beam emitted by it passes through the ultraviolet interference filter 5, the low-power ultraviolet microscope objective lens 8, the dichroic mirror 27 in turn, and then passes through the long working distance high-power ultraviolet microscope objective lens 25. Illuminate and focus on the measurement reticle 24 to form a real-time focal spot 18; the reflected light from the measurement reticle 24 passes through the long working distance high-power ultraviolet microscope objective lens 25 along the main optical axis 4 in the reverse direction, and is reflected by the dichroic mirror 27 , and then reflected by the proportional beam splitter 17, focused by the tube lens 33, and then imaged by the imaging lens 32 to the image sensor 31 in real-time microscopic imaging;

The main controller 7 receives the microscopic digital image output by the image sensor 31, and performs real-time image processing; adopts the edge extraction algorithm to obtain the outer circle contour of the real-time focal spot 18, thereby determining the imaging area of the real-time focal spot 18, and calculating all the pixels in the imaging area. The average gray value G of ;

The main controller 7 sends an instruction to the main motor driver 21 to drive the main linear electric platform 22 to move down by one step; the main controller 7 receives the microscopic digital image output by the image sensor 31, determines the imaging area of the real-time focal spot 18, and calculates The average gray value G of all pixels in the imaging area, and compare whether the G value increases or decreases: if the G value increases, it means that the downward movement is in the direction of approaching the focus; if the G value decreases, it means that the upward movement is the direction of approaching the focus;

The main controller 7 sends an instruction to the main motor driver 21 to drive the main linear electric platform 22 to move in the direction close to the focus, and at the same time calculates the average gray value G of all pixels in the imaging area of the real-time focal spot 18 in real time, until the G value reaches the maximum At this time, it is in a tight focus state, and the main controller 7 sends an instruction to the main motor driver 21 to stop the movement;

In the tight focus state, the main controller 7 uses the edge extraction algorithm to obtain the linear position of the scribe line 20 of the measurement reticle 24 and the outer circle contour of the focal spot 18 in real time by using the edge extraction algorithm on the microscopic digital image output by the image sensor 31, and then calculates the phase The number of pixels at the interval of the adjacent reticle 20 and the number of pixels of the outer circle contour diameter of the real-time focal spot 18, thereby calculating the diameter of the real-time focal spot 18 according to the spacing of the reticle 20;

If the diameter of the real-time focal spot 18 is larger than the diameter of the expected focal spot 19, the main controller 7 sends an instruction to the secondary motor driver 6 to drive the secondary linear motorized stage 9 to move upward, increasing the low-power ultraviolet microscope objective lens 8 and the long working The distance from the high-power ultraviolet microscope objective lens 25, at this time, the laser energy passing through the long working distance high-power ultraviolet microscope objective lens 25 is weakened, but the real-time focal spot 18 is reduced until the diameter of the real-time focal spot 18 and the expected focal spot 19 diameter equal, the main controller 7 sends an instruction to the secondary motor driver 6 to stop the movement of the secondary linear electric platform 9;

Similarly, if the diameter of the real-time focal spot 18 is smaller than the diameter of the expected focal spot 19, the main controller 7 sends an instruction to the secondary motor driver 6 to drive the secondary linear motor stage 9 to move downward, reducing the size of the low-power UV microscope. The distance between the objective lens 8 and the long working distance high-power ultraviolet microscope objective lens 25, the laser energy passing through the long working distance high-power ultraviolet microscope objective lens 25 at this time increases, and the real-time focal spot 18 increases until the real-time focal spot 18 The diameter is the same as expected The diameter of the focal spot 19 is equal, and the main controller 7 sends an instruction to the secondary motor driver 6 to stop the movement of the secondary linear electric platform 9;

(2) Single-point tight focusing of the detection object

Remove the measuring reticle 24, and move the adaptive Raman fluorescence imaging combined system into the actual test area. At this time, the detection object 23 is located below the optical head 2, and the distance from the long working distance high power ultraviolet microscope objective lens 25 is much greater than its focal length;

The main controller 7 controls to turn on the ultraviolet Raman laser 3, and the ultraviolet laser beam emitted by it passes through the ultraviolet interference filter 5, the low-power ultraviolet microscope objective lens 8, the dichroic mirror 27 in turn, and then passes through the long working distance high-power ultraviolet microscope objective lens 25. Defocused to the surface of the detection object 23, the reflected light passes through the long working distance high-power ultraviolet microscope objective lens 25 along the main optical axis 4 in the reverse direction, is reflected by the dichroic mirror 27, and then is reflected by the proportional beam splitter 17, and is focused by the tube lens 33. Then, the microscopic imaging is carried out to the image sensor 31 in real time through the imaging lens 32; the main controller 7 receives the microscopic digital image output by the image sensor 31, and performs fast Fourier transform to extract its high-frequency component H;

The main controller 7 sends an instruction to the three-dimensional motor driver 1 to drive the optical head 2 on the three-dimensional precision electric platform 29 to move downward along the Z axis. At this time, the distance between the detection object 23 and the long working distance high-power ultraviolet microscope objective lens 25 decreases During the movement, the main controller 7 continuously performs fast Fourier transform on the microscopic digital image output by the image sensor 31 in real time, and continuously extracts its high-frequency component H until H reaches the maximum value. At this time, the laser will be tightly focused to detect A point on the surface of the object 23, the size of the real-time focal spot 18 is equal to the size of the expected focal spot 19, and it is in a tight focus state at this time;

(3) Raman fluorescence and imaging information acquisition

In this tight focusing state, the main controller 7 records the three-dimensional displacement of the three-dimensional precision electric stage 29 and sets it as the initial three-dimensional coordinates (x ₁ , y ₁ , z ₁ ); the main controller 7 receives the output of the image sensor 31 The microscopic digital image is obtained by using the edge extraction algorithm to obtain the outer circle contour of the real-time focal spot 18, thereby determining the imaging area of the real-time focal spot 18, and calculating the average gray value g ₁ of all pixels in the imaging area; the real-time focal spot on the surface of the detection object 23 The Raman and fluorescence backscattering at the 18th position passes through the long working distance high-power ultraviolet microscope objective lens 25 along the main optical axis 4, is reflected by the dichroic mirror 27, passes through the proportional beam splitter 17, and is passed through the ultraviolet Rayleigh filter 16. After the Rayleigh scattering of 3 wavelengths of the ultraviolet Raman laser is filtered out, it is focused to the incident end face of the optical fiber 13 through the microscope objective lens 14, and then enters the spectrometer 12, and the spectrometer 12 outputs the spectral signal to the main controller 7 for analysis; the main controller 7. First extract _n discrete Raman spectral lines _{λ 1} , _{λ 2} , λ ₃ , . _{13 , . _ _} .., J _1m ;

(4) Micro-area analysis of Raman fluorescence imaging scanning

The main controller 7 determines the number of scanning points A and B in the XY direction of the micro-area analysis, as well as the scanning step lengths C and D; S-shaped scanning of the XY plane (that is, after scanning to A points along the X-axis according to the scanning step C, the Y-axis is moved forward by a step D, and then the X-axis is scanned in the reverse direction for A points, and then the Y-axis is moved forward by one step Length D, then scan A points in the positive direction of the X axis, then move the Y axis forward by one step D, and then scan A points in the reverse direction along the X axis, ..., until the predetermined scanning area size is completed, the total number of scan points Multiply A by B, that is, A×B), for each point on the XY plane, move up and down along the Z axis, and perform the single-point tight focusing of step (2);

For each scanning point i (i is greater than or equal to 2, until i is equal to A×B), in the tight focusing state of this point, the main controller 7 records the three-dimensional displacement of the three-dimensional precision electric platform 29, and determines its three-dimensional coordinates (x). _i , y _i , z _i ); the main controller 7 receives the microscopic digital image output by the image sensor 31, adopts the edge extraction algorithm to obtain the outer circle contour of the real-time focal spot 18, thereby determines the imaging area of the real-time focal spot 18, and calculates the imaging area The average gray value g _i of all the pixels in the interior; the main controller 7 records the spectral line intensities Ι _i1 , Ι _i2 , Ι _i3 of n discrete Raman spectral lines λ ₁ , λ ₂ , λ ₃ , . . . , λ _{n , . _ _ _}

The main controller 7 first integrates the three-dimensional coordinates of the A×B scan points to draw the three-dimensional geometry of the surface of the detection object 23 in the scan area; then, integrates the g ₁ , g ₂ ,..., g _i ,. .., the grayscale image of the three-dimensional geometry of the surface of the detection object ₂₃ can be obtained (this embodiment is a broad-spectrum image with a response band of 350 to 800 nanometers ₎ ; ...,I _i1 ,..., a Raman image with a wavelength of λ ₁ on the surface of the detection object 23 is obtained. Similarly, I ₁₂ ,I ₂₂ ,...,I _i2 ,... , obtain a Raman image with a wavelength of _{λ 2 on} the surface of the detection object ₂₃ , . ..,J _i1 ,..., to obtain the fluorescence image of the first spectral segment on the surface of the detection object 23, similarly, synthesize the J ₁₂ ,J ₂₂ ,...,J _i2 ,..., obtaining the fluorescence image of the second spectral section on the surface of the detection object 23, . . . , until the fluorescence image of the mth spectral section on the surface of the detection object 23 is obtained;

(5) LIBS scanning micro-area analysis and information fusion

The main controller 7 sends an instruction to the cut-in controller 36 to cut the LIBS into the total reflection mirror 34 into the main optical axis 4; the main controller 7 sends an instruction to set the exposure time of the spectrometer 12 (1 millisecond in this embodiment); the main control The device 7 sends an instruction to the digital pulse delay controller 39 to set the operating frequency of the LIBS laser 38 (3 Hz in this embodiment), and the delay time between the LIBS laser 38 and the spectrometer 12 being turned on (10 in this embodiment). microseconds);

The main controller 7 sends an instruction to the three-dimensional motor driver 1 to drive the optical head 2 on the three-dimensional precision electric platform 29 to perform the scan opposite to step (4) according to the recorded three-dimensional coordinates of the A×B scan points, that is, the reverse S Shape scanning, complete scanning points A×B in reverse;

For each scanning point, LIBS detection is performed for a single point for 1 second, and the main controller 7 receives the output LIBS spectrum information of the spectrometer 12 (this embodiment averages the 3 LIBS spectra obtained in 1 second, and then makes an analysis) , according to the relationship between spectral line position and intensity, qualitatively and quantitatively analyze the element composition and content of this point, until the micro-LIBS analysis of the entire A×B point is completed;

Fusion with step (4) information to complete the micro-area laser spectrum and imaging analysis, that is, to obtain the three-dimensional topography distribution of the micro-area, the broad-spectrum image of A×B scanning points on the three-dimensional topography distribution, and the ultraviolet light of n wavelengths. Laser Raman images, UV laser-induced fluorescence hyperspectral images of m spectral bands, and element distribution images.

Claims (1)

1. A self-adaptive laser spectrum and imaging method suitable for deep space micro-area analysis is realized on a self-adaptive laser spectrum and imaging detection system, wherein the system consists of a main controller (7), a spectrometer (12), an optical fiber (13), a three-dimensional motor driver (1), a three-dimensional precise electric platform (29), a digital pulse delay controller (39) and an optical head (2); the optical head (2) consists of an LIBS laser (38), an LIBS cut-in total reflection mirror (34), a cut-in controller (36), an ultraviolet Raman laser (3), an ultraviolet interference filter (5), a secondary motor driver (6), a secondary linear electric platform (9), a low-power ultraviolet microscope objective (8), a dichroic mirror (27), a long-working-distance high-power ultraviolet microscope objective (25), a main motor driver (21), a main linear electric platform (22), an ultraviolet Rayleigh filter (16), a proportion beam splitter (17), a microscope objective (14), a tube lens (33) and an electronic eyepiece (11); an imaging lens (32) and an image sensor (31) are arranged in the electronic eyepiece (11);

the pulsed LIBS laser beam (35) emitted by the LIBS laser (38) along the LIBS optical axis (37) and the continuous laser emitted by the ultraviolet Raman laser (3) along the main optical axis (4) have the same initial beam diameter and the same minimum divergence angle; when in the non-LIBS working mode, the cut-in controller (36) cuts the LIBS into the total reflection mirror (34) and cuts out the main optical axis (4); when the laser is in an LIBS working mode, the cut-in controller (36) cuts the LIBS cut-in total reflection mirror (34) into the main optical axis (4), at the moment, the distance from the output ports of the LIBS laser (38) and the ultraviolet Raman laser (3) to the LIBS cut-in total reflection mirror (34) is equal, after a pulse LIBS laser beam (35) emitted by the LIBS laser (38) along the LIBS optical axis (37) is cut into the total reflection mirror (34) through the LIBS for total reflection, enters a main optical axis (4) for transmission, forms a cylindrical near-collimation laser beam (30) which passes through a low-power ultraviolet microscope objective (8), forms a conical laser beam (28) which passes through a dichroic mirror (27), the LIBS echo signal reversely passes through the long working distance high-power ultraviolet microscope objective (25) along the main optical axis (4) and travels along the receiving optical axis (15) after being reflected by the dichroic mirror (27), and is divided into two orthogonal paths after reaching the proportional beam splitter (17): one path of the signal travels along an imaging optical axis (10) through reflection, and the signal is not used in an LIBS mode; the other path of light passes through the proportional beam splitter (17), then passes through an ultraviolet Rayleigh filter (16) to filter out Rayleigh scattering of the LIBS laser (38) wavelength, then passes through a microscope objective (14) to be focused to the incident end face of the optical fiber (13), and then enters the spectrometer (12) for analysis; the digital pulse delay controller (39) is provided with two control ends which are respectively connected with an LIBS laser (38) and an external trigger port of the spectrometer (12); the digital pulse delay controller (39) is used for setting the working frequency of the LIBS laser (38) and the time delay of the opening between the LIBS laser (38) and the spectrometer (12);

laser beams emitted by the ultraviolet Raman laser (3) along the main optical axis (4) pass through the ultraviolet interference filter (5), so that frequency division harmonic interference of the ultraviolet laser emitted by the ultraviolet Raman laser (3) can be filtered, and the signal-to-noise ratio of Raman signals excited by the ultraviolet Raman laser is higher; the formed cylindrical near-collimation laser beam (30) passes through a low-power ultraviolet microscope objective (8) to form a conical laser beam (28); the conical laser beam (28) passes through the dichroic mirror (27) and then reaches an entrance pupil (26) of the long-working-distance high-power ultraviolet microscope objective (25), the diameter of the conical laser beam (28) is larger than that of the entrance pupil (26) at the position of the entrance pupil (26), and the farther the distance between the low-power ultraviolet microscope objective (8) and the long-working-distance high-power ultraviolet microscope objective (25) is, the larger the diameter of the conical laser beam (28) is than that of the entrance pupil (26) because the cone angle of the conical laser beam (28) is a fixed value, the weaker the laser energy passing through the long-working-distance high-power ultraviolet microscope objective (25) is, and the smaller the focused light spot is; therefore, by adjusting the distance between the low-power ultraviolet microscope objective (8) and the long-working-distance high-power ultraviolet microscope objective (25), the selection is made between the laser energy passing through the long-working-distance high-power ultraviolet microscope objective (25) and the size of a focused light spot, namely a large-energy large light spot and a small-energy small light spot; echo signals reversely pass through a long working distance high-power ultraviolet microscope objective (25) along a main optical axis (4), and travel along a receiving optical axis (15) after being reflected by a dichroic mirror (27) and reach a proportional beam splitter (17) and then are divided into two orthogonal paths: one path of light is reflected and travels along an imaging optical axis (10), is focused between one time and two times of focal length of an imaging lens (32) in the electronic eyepiece (11) through a tube lens (33), and is amplified to form a real image to an image sensor (31) through the imaging lens (32); the other path of light passes through the proportional beam splitter (17), then passes through an ultraviolet Rayleigh filter (16) to filter Rayleigh scattering of the wavelength of the ultraviolet Raman laser (3), and then is focused to the incident end face of the optical fiber (13) through a microscope objective (14), and then enters a spectrometer (12) for analysis; the low-power ultraviolet microscope objective (8) is arranged on a secondary linear electric platform (9) and can do one-dimensional precise translation along the main optical axis (4) under the driving of a secondary motor driver (6); the long working distance high power ultraviolet microscope objective (25) is arranged on the main linear electric platform (22) and can do one-dimensional precise translation along the main optical axis (4) under the drive of the main motor driver (21); the translation of the secondary linear electric platform (9) is mainly used for changing the distance between the low-power ultraviolet microscope objective (8) and the long-working-distance high-power ultraviolet microscope objective (25); the translation of the main linear electric platform (22) is mainly used for accurately focusing the long-working-distance high-power ultraviolet microscope objective (25); the LIBS optical axis (37), the main optical axis (4), the imaging optical axis (10) and the receiving optical axis (15) are coplanar; the main optical axis (4) is parallel to the imaging optical axis (10) and is vertical to the LIBS optical axis (37) and the receiving optical axis (15);

the optical head (2) is arranged on a three-dimensional precise electric platform (29), and the three-dimensional precise electric platform (29) can do submicron three-dimensional precise motion under the driving of a three-dimensional motor driver (1);

the main controller (7) can send control instructions to the switching-in controller (36), the digital pulse delay controller (39), the three-dimensional motor driver (1), the main motor driver (21), the secondary motor driver (6), the ultraviolet Raman laser (3), the image sensor (31) and the spectrometer (12); the main controller (7) also sets the exposure time of the spectrometer (12), and can receive the output digital image of the image sensor (31) and the output spectrum information of the spectrometer (12);

the method is characterized in that the self-adaptive laser spectrum and imaging method comprises the following steps:

1) prospective focal spot adaptive focus calibration

In the in-situ detection of deep space materials, Raman focusing points with different scales are needed for different detection objects, namely expected focal spots;

firstly, setting the diameter of an expected focal spot according to the basic properties of a detection object in a test region; placing a measuring reticle in a test area below a long-working-distance high-power ultraviolet microscope objective; uniform scribed lines are arranged on the measuring reticle;

the main controller controls to start the ultraviolet Raman laser, and an ultraviolet laser beam emitted by the ultraviolet Raman laser sequentially passes through the ultraviolet interference optical filter, the low-power ultraviolet microscope objective and the dichroic mirror, is illuminated and focused to the measurement reticle through the long-working-distance high-power ultraviolet microscope objective, and forms a real-time focal spot; the reflected light of the measuring reticle passes through the long-working-distance high-power ultraviolet microscope objective along the main optical axis in the reverse direction, is reflected by the dichroic mirror, is reflected by the proportional beam splitter, is focused by the tube lens, and is subjected to real-time microscopic imaging by the imaging lens to the image sensor;

the main controller receives the microscopic digital image output by the image sensor and performs real-time image processing; acquiring the excircle profile of the real-time focal spot by adopting an edge extraction algorithm, thereby determining an imaging region of the real-time focal spot and calculating the average gray value G of all pixels in the imaging region;

the main controller sends an instruction to the main motor driver to drive the main linear electric platform to move downwards by a step length; the main controller receives the microscopic digital image output by the image sensor, determines the imaging area of the real-time focal spot, calculates the average gray value G of all pixels in the imaging area, and compares whether the G value is increased or decreased: if the value of G is increased, it indicates that the downward motion is in a direction close to the focal point; if the value of G is decreased, it indicates that the upward movement is in a direction close to the focal point;

the main controller sends an instruction to the main motor driver to drive the main linear electric platform to move towards the direction close to the focal point, and simultaneously calculates the average gray value G of all pixels in the imaging area of the real-time focal spot in real time until the G value reaches the maximum value, and at the moment, the main controller is in a tight focusing state and sends an instruction to the main motor driver to stop moving;

in a tight focusing state, the main controller adopts an edge extraction algorithm to obtain the linear position of the scribed lines of the measuring reticle and the real-time focal spot excircle outline of the microscopic digital image output by the image sensor, and then calculates the number of pixels at the interval of adjacent scribed lines and the number of pixels of the real-time focal spot excircle outline diameter, so as to calculate the real-time focal spot diameter according to the distance of the scribed lines;

if the diameter of the real-time focal spot is larger than that of the expected focal spot, the main controller sends an instruction to the secondary motor driver to drive the secondary linear electric platform to move upwards, the distance between the low-power ultraviolet microscope objective and the long-working-distance high-power ultraviolet microscope objective is increased, the laser energy passing through the long-working-distance high-power ultraviolet microscope objective is weakened, the real-time focal spot is reduced until the diameter of the real-time focal spot is equal to that of the expected focal spot, and the main controller sends an instruction to the secondary motor driver to stop the movement of the secondary linear electric platform;

if the diameter of the real-time focal spot is smaller than that of the expected focal spot, the main controller sends an instruction to the secondary motor driver to drive the secondary linear electric platform to move downwards, the distance between the low-power ultraviolet microscope objective and the long-working-distance high-power ultraviolet microscope objective is reduced, the laser energy passing through the long-working-distance high-power ultraviolet microscope objective is increased, the real-time focal spot is increased until the diameter of the real-time focal spot is equal to that of the expected focal spot, and the main controller sends an instruction to the secondary motor driver to stop the movement of the secondary linear electric platform;

2) single point tight focus of detection object

Removing the measuring reticle, and moving the self-adaptive Raman fluorescence imaging combination system into an actual test area, wherein the detection object is positioned below the optical head, and the distance from the long working distance to the high-power ultraviolet microscope objective is far larger than the focal length of the high-power ultraviolet microscope objective;

the main controller controls and starts the ultraviolet Raman laser, an ultraviolet laser beam emitted by the ultraviolet Raman laser sequentially passes through an ultraviolet interference optical filter, a low-power ultraviolet microscope objective and a dichroic mirror, is defocused to the surface of a detection object through a long-working-distance high-power ultraviolet microscope objective, reflected light passes through the long-working-distance high-power ultraviolet microscope objective along a main optical axis in the reverse direction, is reflected by the dichroic mirror, is reflected by a proportional beam splitter, is focused through a tube lens, and is microimaged to an image sensor in real time through an imaging lens; the main controller receives the microscopic digital image output by the image sensor, and performs fast Fourier transform to extract a high-frequency component H of the microscopic digital image;

the main controller sends an instruction to a three-dimensional motor driver to drive an optical head on the three-dimensional precise electric platform to move downwards along the Z-axis, at the moment, the distance between a detected object and a long working distance high-power ultraviolet microscope objective is reduced, in the moving process, the main controller continuously carries out fast Fourier transform on a microscopic digital image output by an image sensor in real time, and continuously extracts a high-frequency component H of the microscopic digital image until the H reaches the maximum value, at the moment, laser is tightly focused to one point on the surface of the detected object, the size of a real-time focal spot is equal to that of an expected focal spot, and the laser is in a;

3) raman fluorescence and imaging information acquisition

In this tight focus state, the master controller records the three-dimensional displacement of the three-dimensional precision motorized stage, setting it to the initial three-dimensional coordinates (x)₁,y₁,z₁) (ii) a The main controller receives the microscopic digital image output by the image sensor, and the edge extraction algorithm is adopted to obtain the excircle outline of the real-time focal spot, so that the imaging area of the real-time focal spot is determined, and the average gray value g of all pixels in the imaging area is calculated₁(ii) a Detecting Raman and fluorescence backscattering of a real-time focal spot position on the surface of an object, penetrating through a long working distance high-power ultraviolet microscope objective along a main optical axis, reflecting through a dichroic mirror, transmitting through a proportional beam splitter, filtering out Rayleigh scattering of the wavelength of an ultraviolet Raman laser through an ultraviolet Rayleigh filter, focusing to an incident end face of an optical fiber through the microscope objective, then entering a spectrometer, and outputting a spectrum signal to a main controller by the spectrometer for analysis; the main controller firstly extracts n discrete Raman spectral lines lambda of the spectral signal₁，λ₂，λ₃，...，λ_nRecording the spectral line intensity I₁₁，Ι₁₂，Ι₁₃，...，Ι_1n(ii) a Then dividing the continuous fluorescence spectral line into m sections with equal spectral intervals; and recording the mean intensity J of the fluorescence spectrum of each segment₁₁，J₁₂，J₁₃，...，J_1m；

4) Raman fluorescence imaging scanning micro-area analysis

The main controller determines A, B scanning points in the XY direction of the micro-area analysis and C, D scanning step length; the main controller sends an instruction to the three-dimensional motor driver to drive the optical head on the three-dimensional precise electric platform to perform S-shaped scanning on an XY plane, and then moves up and down along a Z axis for each point on the XY plane to execute single-point tight focusing in the step 2);

for each scanning point i, i is more than or equal to 2 until i is equal to A multiplied by B, and under the tight focusing state of the point, the main controller records the three-dimensional displacement of the three-dimensional precision electric platform and determines the three-dimensional coordinate (x) of the three-dimensional precision electric platform_i,y_i,z_i) (ii) a The main controller receives the microscopic digital image output by the image sensor, and the edge extraction algorithm is adopted to obtain the excircle outline of the real-time focal spot, so that the imaging area of the real-time focal spot is determined, and the average gray value g of all pixels in the imaging area is calculated_i(ii) a The main controller records n discrete Raman spectral lines lambda₁，λ₂，λ₃，...，λ_nSpectral line intensity I_i1，Ι_i2，Ι_i3，...，Ι_in(ii) a And recording the average intensity J of the fluorescence spectrum of each section of the m sections of the fluorescence spectrum_i1,J_i2,J_i3,...,J_im；

The main controller firstly integrates the three-dimensional coordinates of A multiplied by B scanning points and draws the three-dimensional geometric appearance of the surface of the detection object in the scanning area; then, g of each scanning point is integrated₁,g₂,...,g_i,., obtaining a gray level image of the three-dimensional geometric shape of the surface of the detection object; then, the I of each scanning point is integrated₁₁,I₂₁,...,I_i1,., obtaining the wavelength of the surface of the detection object as lambda₁Raman image of (2), integrating I of each scanning point₁₂,I₂₂,...,I_i2,., obtaining the wavelength of the surface of the detection object as lambda₂Until the wavelength of the surface of the detected object is obtained as lambda_n(ii) a raman image of; finally, the J of each scanning point is integrated₁₁,J₂₁,...,J_i1,., obtaining a fluorescence image of the first spectrum of the surface of the detected object, and integrating J of each scanning point₁₂,J₂₂,...,J_i2,., obtaining a fluorescence image of the second spectrum band of the surface of the detection object until obtaining a fluorescence image of the m spectrum band of the surface of the detection object;

5) LIBS scanning micro-area analysis and information fusion

The main controller sends a command to the cut-in controller to cut the LIBS cut-in total reflection mirror into the main optical axis; the main controller sends out an instruction to set the exposure time of the spectrometer; the main controller sends an instruction to the digital pulse delay controller, and sets the working frequency of the LIBS laser and the time delay of the opening between the LIBS laser and the spectrometer;

the main controller sends an instruction to the three-dimensional motor driver to drive the optical head on the three-dimensional precise electric platform to perform scanning opposite to the step 4) according to the recorded three-dimensional coordinates of A multiplied by B scanning points, namely reverse S-shaped scanning, and reversely finishing the number A multiplied by B of the scanning points;

for each scanning point, performing LIBS detection with a single point of 1 second, receiving the output LIBS spectrum information of the spectrometer by the main controller, and qualitatively and quantitatively analyzing the element composition and content of the point according to the relation between the spectral line position and the intensity until the micro-area LIBS analysis of the whole A multiplied by B point is completed;

and 4) information fusion is carried out with the step 4) to complete the laser spectrum and imaging analysis of the micro-area, namely, the three-dimensional shape distribution of the micro-area, the wide spectrum image of A multiplied by B scanning points on the three-dimensional shape distribution, the ultraviolet laser Raman image of n wavelengths, the ultraviolet laser induced fluorescence hyperspectral image of m spectral bands and the element distribution image are obtained.

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