Three-dimensional imaging system and method based on ultra-short pulse laser and chromaticity confocal

Abstract

The invention relates to a three-dimensional imaging system and method based on ultra-short pulse laser and chromaticity confocal, and belongs to the technical field of optical imaging. The system comprises an ultra-short pulse laser, a chromaticity dispersion lens element, a confocal microscopic optical path structure, a displacement platform and a dispersion Fourier transform module; through fusion of an ultrashort pulse laser technology, a chromaticity confocal principle and dispersion Fourier transform, a large-field-of-view, high-resolution and ultrafast scanning three-dimensional imaging system is constructed, longitudinal fast sampling with pulse repetition frequency as a refresh rate is realized, full three-dimensional reconstruction is completed through transverse mechanical scanning, and the full-field-of-view, high-resolution and ultrafast scanning three-dimensional imaging is realized. Therefore, a brand new technical means is provided for precise observation of an ultrafast dynamic process, and the problems of low imaging speed, low detection bandwidth, low signal-to-noise ratio, insufficient time resolution and the like generally existing in a confocal and chromaticity confocal three-dimensional imaging technology in the prior art can be solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of optical imaging technology, and particularly relates to a three-dimensional imaging system and method based on ultrashort pulse laser and chromatic confocal. BACKGROUND

[0002] In high-energy laser systems, the surface of optical elements or thin film layers long withstands high-intensity laser irradiation, and are extremely prone to micron-level deformation or even local damage due to instantaneous heat accumulation. Such a dynamic damage process can last for several microseconds in a continuous wave laser system, and can be as short as nanoseconds or even picoseconds in a pulsed laser system. This rapidly evolving surface shape distortion not only introduces significant wavefront aberration, affecting the beam quality, but also can cause a chain reaction of damage to downstream optical components through a cascade effect. Therefore, it is a key requirement to ensure the stable operation of large laser devices to realize high spatial and temporal resolution, real-time online three-dimensional monitoring of the surface topography of optical elements.

[0003] As a mature three-dimensional optical imaging technology, confocal laser scanning microscopy (CLSM) has been widely used in biomedical, material science and precision detection fields since it was proposed in the 1970s. Its core principle is to use a spatial pinhole to filter out out-of-focus light, and only collect the reflected or fluorescent signals at the focal point, thereby obtaining optical slice images with high lateral and axial resolution. By scanning point by point and layer by layer, CLSM can reconstruct the three-dimensional topography of the sample, and performs excellent performance in the measurement of static or slowly varying processes.

[0004] However, the traditional CLSM relies on mechanical scanning mechanisms to complete three-dimensional scanning in the X-Y plane and Z-axis direction, and its imaging speed is limited by factors such as the response time of the galvanometer, the motion accuracy of the piezoelectric displacement table, and the integration time of the detector, making it difficult to meet the observation needs of microsecond to nanosecond dynamic processes. To improve the axial scanning efficiency, chromatic confocal technology (Chromatic Confocal Technology) emerged as the times require. This technology uses a specific dispersive lens to focus different wavelength components of a broadband light source at different axial depth positions, and by detecting the wavelength with the strongest reflected light, the height of the measured point can be determined, thereby replacing the Z-direction mechanical scanning with a "wavelength-encoding-depth" method, significantly improving the axial measurement speed.

[0005] However, there are still some bottlenecks in the existing chromatic confocal system: first, most systems use white light or wide-spectrum LED as light source, which has poor spatial coherence, resulting in poor ability of confocal pinhole to suppress stray light and low signal-to-noise ratio; second, spectral information usually needs to be detected by spectrometer, and the acquisition rate of spectrometer is limited by the readout speed of CCD or linear array detector, which becomes the bottleneck of overall frame rate improvement; third, the spectral characteristics of conventional multi-color light source are difficult to support high-precision measurement in ultrafast and single pulse scale, limiting its application in ultrafast dynamic process monitoring. SUMMARY

[0006] In view of the various deficiencies of the prior art, a three-dimensional imaging system and method based on ultra-short pulse laser and chromatic confocal are proposed to solve the problems of slow imaging speed, low detection bandwidth, low signal-to-noise ratio and insufficient time resolution in the prior art.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions: In a first aspect, the present application provides a three-dimensional imaging system based on ultra-short pulse laser and chromatic confocal, comprising: an ultra-short pulse laser for outputting ultra-short pulse laser with wide spectral characteristics; a chromatic dispersion lens element configured to focus different wavelength components of the ultra-short pulse laser to different longitudinal positions in the direction of its optical axis, forming longitudinal focal spots distributed along the optical axis; a confocal microscopic optical structure configured to form a detection focal point conjugated with a measured focal point, so that the reflected light from the measured focal point converges to the detection focal point after returning along the original path, the measured focal point being a focal spot formed on the surface of the measured object after the ultra-short pulse laser is focused by the chromatic dispersion lens element; a displacement platform for driving the measured object to move in a transverse plane perpendicular to the optical axis to realize three-dimensional scanning of the measured object; and a dispersion Fourier transform module for converting the spectral information of the reflected light into a time-domain pulse waveform.

[0008] The technical solution further provides that the confocal microscopic optical structure comprises: a collimating lens for collimating the ultra-short pulse laser and converging the reflected light; and a fiber optic circulator, the first port of which is connected to the ultra-short pulse laser, the second port of which is connected to the collimating lens, and the third port of which outputs the reflected light reflected by the measured focal point, the reflected light being transmitted to the dispersion Fourier transform module, and the detection focal point being located at the end of the optical fiber connected to the second port of the fiber optic circulator.

[0009] The technical solution is further configured such that the chromatic dispersion lens element is a Fresnel zone plate, a four-phase diffraction lens, an eight-phase diffraction lens, a dispersive lens, or a metasurface lens.

[0010] The technical solution is further configured such that the dispersion Fourier transform module includes a transmission medium with group velocity dispersion, wherein the transmission medium is configured as a single-mode optical fiber, a dispersion-compensating optical fiber, a few-mode optical waveguide, or a chirped Bragg fiber grating.

[0011] This technical solution is further configured to include a time lens module and a photodetector; The time lens module is connected to the output of the dispersive Fourier transform module and is used to stretch and amplify the converted time-domain pulse waveform. The photodetector is used to convert the stretched and amplified optical signal into an electrical signal.

[0012] The technical solution is further configured to include an oscilloscope, which is connected to the output terminal of the photodetector and is used to acquire and display the time-domain waveform of the electrical signal.

[0013] Secondly, the present invention provides an ultrafast scanning three-dimensional imaging method based on ultrashort pulse laser and chromatic confocal imaging, characterized by comprising the following steps: S100: Ultrashort pulse laser with broadband spectral characteristics is generated by an ultrashort pulse laser. S200: By using a chromatic dispersive lens element, different wavelength components of the ultrashort pulse laser are focused to different longitudinal positions along its optical axis to form a longitudinal focal spot; S300: The object under test is moved in the horizontal plane by a displacement platform, and the reflected light is collected by a confocal microscopic optical path structure. S400: The spectral information of the reflected light is converted into a time-domain pulse waveform using a dispersive Fourier transform module, and a three-dimensional shape image of the object under test is reconstructed based on the time-domain pulse waveform.

[0014] The technical solution is further configured such that the longitudinal focal spot is distributed along the Z-axis, and the displacement platform drives the object under test to move in the XY plane, so that the test points on the object under test pass through the longitudinal focal spot area in sequence, thereby realizing lateral spatial sampling.

[0015] This technical solution is further configured such that, in S400, the reconstruction process of the three-dimensional topography image includes: The time-domain pulse waveform is demodulated to obtain reflectivity information of different wavelength components; The reflection intensity of each depth layer is determined based on the pre-defined mapping relationship between wavelength and longitudinal depth. By combining the lateral position information of the displacement platform, the three-dimensional topographic data of the surface of the measured object are reconstructed. The beneficial effects of this invention are: By innovatively integrating ultrashort pulse laser technology, the principle of chromatic confocal microscopy, and dispersive Fourier transform, a novel large field-of-view, high-resolution, ultrafast scanning 3D imaging system has been constructed. This system enables rapid longitudinal sampling with a refresh rate based on the pulse repetition frequency and completes full 3D reconstruction through lateral mechanical scanning. This provides a new technical means for the precise observation of ultrafast dynamic processes, fundamentally breaking through the physical bottleneck of imaging speed in traditional confocal microscopy. It not only achieves a leap from "slow layer-by-layer scanning" to "ultrafast parallel detection," but also achieves comprehensive improvements in signal-to-noise ratio, stability, and practicality. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a three-dimensional imaging system based on ultrashort pulse laser and chromatic confocal imaging in an embodiment of the present invention; Figure 2 This is a schematic diagram of the confocal microscopy optical path structure in an embodiment of the present invention; Figure 3 This is a flowchart of an ultrafast scanning three-dimensional imaging method based on ultrashort pulse laser and chromatic confocal imaging in an embodiment of the present invention; In the attached figures: 100, ultrashort pulse laser; 200, confocal microscopic optical path structure; 201, fiber optic circulator; 202, collimating lens; 300, chromatic dispersion lens element; 400, object under test; 500, displacement platform; 600, dispersive Fourier transform module; 700, time lens module; 800, photodetector; 900, oscilloscope; Appendix Figure 2 In the diagram, 1 represents the first port of the fiber optic circulator; 2 represents the second port of the fiber optic circulator; and 3 represents the third port of the fiber optic circulator. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application. Furthermore, directional terms mentioned in the following embodiments, such as "up," "down," "left," and "right," are only for reference to the directions in the accompanying drawings; therefore, the directional terms used are for illustrative purposes and not for limiting the invention.

[0018] Example 1: According to an embodiment of the present invention, a three-dimensional imaging system based on ultrashort pulse laser and chromatic confocal imaging is provided. Please refer to [link to relevant documentation]. Figures 1 to 2 ,include: An ultrashort pulse laser 100 is used to output ultrashort pulse lasers with wide spectral characteristics; The chromatic dispersion lens element 300 is configured to focus different wavelength components of the ultrashort pulse laser to different longitudinal positions along its optical axis, forming longitudinal focal spots distributed along the optical axis. The confocal microscopic optical path structure 200 is configured to form a detection focus conjugate with the focus to be measured, so that the reflected light from the focus to be measured returns along the original path and converges to the detection focus. The focus to be measured is the spot formed on the surface of the object to be measured 400 after the ultrashort pulse laser is focused by the chromatic dispersive lens element 300. The displacement platform 500 is used to drive the object under test 400 to move in a transverse plane perpendicular to the optical axis, so as to realize the three-dimensional scanning of the object under test 400. And a dispersive Fourier transform module 600, used to convert the spectral information of the reflected light into a time-domain pulse waveform.

[0019] Specifically, ultrashort pulse lasers are used as illumination light, continuously illuminating the object under test 400 in the form of light pulse trains in a single frame. The spectral characteristics of ultrashort pulse lasers are a flat-top spectrum with a width of tens of nanometers. On the one hand, it has a repetition frequency of MHz, enabling simultaneous measurement of a large number of pulses at the same location, and averaging can obtain more accurate imaging information. On the other hand, it has good coherence, which improves the intensity of reflected light and overcomes the low signal-to-noise ratio of the detection signal caused by poor coherence of ordinary white light sources and other light sources, effectively improving the signal-to-noise ratio and obtaining higher spatial resolution.

[0020] Understandably, through the innovative integration of ultrashort pulse laser technology, the principle of chromatic confocal microscopy, and dispersive Fourier transform, a novel large field-of-view, high-resolution, ultrafast scanning 3D imaging system has been constructed. This system enables rapid longitudinal sampling with a refresh rate based on the pulse repetition frequency and completes full 3D reconstruction through lateral mechanical scanning. This provides a new technical means for the precise observation of ultrafast dynamic processes, fundamentally breaking through the physical bottleneck of imaging speed in traditional confocal microscopy. It not only achieves a leap from "slow layer-by-layer scanning" to "ultrafast parallel detection," but also achieves comprehensive improvements in signal-to-noise ratio, stability, and practicality.

[0021] In this embodiment, a three-dimensional imaging system based on ultrashort pulse laser and chromatic confocal imaging is described. Please refer to [link to relevant documentation]. Figures 1 to 2 The confocal microscopy optical path structure 200 includes: Collimating lens 202 is used to collimate ultrashort pulse lasers and converge reflected light; And an optical fiber circulator 201, whose first port is connected to the ultrashort pulse laser 100, whose second port is connected to the collimating lens 202, and whose third port outputs the reflected light reflected from the measured focal point. The reflected light is transmitted to the dispersive Fourier transform module 600, and the detection focal point is located at the end of the optical fiber connected to the second port of the optical fiber circulator.

[0022] Specifically, the fiber optic circulator 201 enables unidirectional circular transmission of the optical path. Light output from the ultrashort pulse laser 100 is introduced through the first port 1 and output through the second port 2 to the subsequent optical path. Reflected light from the object under test 400 is then input through the second port 2 and output through the third port 3 to the dispersive Fourier transform module 600. As the "traffic hub" of the optical path, the fiber optic circulator 201 separates the incident illumination light and the returning reflected light, making it a key device for achieving common-path interference and signal acquisition.

[0023] Specifically, the collimating lens 202 collimates the diverging laser beam output from the fiber optic circulator 201 to form a parallel beam; at the same time, it focuses the reflected light reflected from the object under test 400 and returned after passing through the chromatic dispersive lens element 300, so that it is efficiently coupled back to the fiber, ensuring beam quality, reducing chromatic aberration, ensuring that light of different wavelengths can be effectively transmitted and focused, and maintaining the high resolution of the system.

[0024] Specifically, the fiber optic end is located at the connection between the second port 2 of the fiber optic circulator and the collimating lens 202. It serves as both the output surface for illumination light and the receiving surface for reflected light. As the carrier of the detection focus, it ensures that only the light from the measured focus is efficiently collected through positional conjugate relationships, making it a key structure for improving system resolution and signal-to-noise ratio.

[0025] In this embodiment, a three-dimensional imaging system based on ultrashort pulse laser and chromatic confocal imaging is described. Please refer to [link to relevant documentation]. Figures 1 to 2 The chromatic dispersion lens element 300 is configured as a Fresnel zone plate, a four-phase diffraction lens, an eight-phase diffraction lens, a dispersive lens, or a metasurface lens.

[0026] It is understandable that ultrashort pulse lasers are broadband light with a certain spectral range. The chromatic dispersive lens element 300 itself is a focusing element with a designed center wavelength and a designed focal length. Due to dispersion, the focal length of light of different wavelengths passing through the chromatic dispersive lens element 300 is different. The relationship between focal length and wavelength is approximately linear near the center wavelength. Therefore, the focal position of broadband ultrashort pulse lasers emitted from the same point after passing through the chromatic dispersive lens element 300 is linearly related to the laser wavelength.

[0027] In this embodiment, a three-dimensional imaging system based on ultrashort pulse laser and chromatic confocal imaging is described. Please refer to [link to relevant documentation]. Figures 1 to 2The dispersion Fourier transform module 600 includes a transmission medium with group velocity dispersion, wherein the transmission medium is configured as a single-mode fiber, a dispersion-compensating fiber, a few-mode waveguide, or a chirped Bragg fiber grating.

[0028] In this embodiment, a three-dimensional imaging system based on ultrashort pulse laser and chromatic confocal imaging is described. Please refer to [link to relevant documentation]. Figures 1 to 2 It also includes a time lens module 700 and a photodetector 800; The time lens module 700 is connected to the output of the dispersive Fourier transform module 600 and is used to stretch and amplify the converted time-domain pulse waveform. The photodetector 800 is used to convert the stretched and amplified optical signal into an electrical signal.

[0029] Specifically, the time lens module 700 can be implemented using, but is not limited to, schemes based on electro-optic modulation, acousto-optic modulation, or optical nonlinearity. Its core is to apply secondary phase modulation to the light pulse and combine it with dispersion to complete the time domain transformation.

[0030] In this embodiment, a three-dimensional imaging system based on ultrashort pulse laser and chromatic confocal imaging is described. Please refer to [link to relevant documentation]. Figures 1 to 2 It also includes an oscilloscope 900, which is connected to the output terminal of the photodetector 800 and is used to acquire and display the time-domain waveform of the electrical signal.

[0031] Example 2: According to embodiments of the present invention, an ultrafast scanning three-dimensional imaging method based on ultrashort pulse laser and chromatic confocal imaging is provided. Please refer to [link to relevant documentation]. Figures 1 to 3 This includes the following steps: S100, an ultrashort pulse laser with broadband spectral characteristics is generated by an ultrashort pulse laser 100; S200: The chromatic dispersive lens element 300 focuses different wavelength components of the ultrashort pulse laser to different longitudinal positions along its optical axis, forming a longitudinal focal spot; S300: The displacement platform 500 moves the object under test 400 in the horizontal plane. At the same time, the confocal microscopic optical path structure 200 collects the reflected light and uses the conjugate relationship between the end of the optical fiber and the focal point under test to filter out stray light. S400: The spectral information of the reflected light is converted into a time-domain pulse waveform using the dispersive Fourier transform module 600, and a three-dimensional shape image of the object under test is reconstructed based on the time-domain pulse waveform.

[0032] Furthermore, the longitudinal focal spot is distributed along the Z-axis, and the displacement platform 500 drives the object under test 400 to move in the XY plane, so that the test points on the object under test 400 pass through the longitudinal focal spot area in sequence, thereby realizing lateral spatial sampling.

[0033] Specifically, the displacement platform 500 is operated to move the object under test 400 within a plane perpendicular to the optical axis (i.e., the XOY plane). By precisely controlling the lateral (X and Y directions) position of the displacement platform 500, the test points on the surface of the object under test 400 are sequentially moved into the axial measurement area of ​​the longitudinal focal spot formed by the ultrashort pulse laser after passing through the chromatic dispersive lens element 300, ensuring that the reflected light signal at that point can be effectively collected. The lateral scanning of the displacement platform 500, combined with the high repetition rate of the ultrashort pulse laser, achieves "three-dimensional imaging with a period of one horizontal scan time," meeting the real-time requirements of online monitoring of optical components.

[0034] Furthermore, in S400, the reconstruction process of the three-dimensional topography image includes: S401. Demodulate the time-domain pulse waveform to obtain reflectivity information of different wavelength components.

[0035] Specifically, the dispersive Fourier transform technique is used to "map" the reflection spectrum carrying 400 information about the object being measured to the time domain. When the reflected light passes through a transmission medium with strong group velocity dispersion, light components of different frequencies (wavelengths) experience a "walk-away" effect due to their different propagation speeds. The spectral components that originally coexisted in the frequency domain are "stretched" into a time-varying pulse waveform in the time domain, and the envelope shape of the pulse waveform corresponds to the intensity distribution of the original spectrum.

[0036] The photodetector 800 converts the time-domain pulse waveform into a voltage signal, and the oscilloscope 900 acquires the voltage signal at a high sampling rate to obtain a digitized time-domain waveform. The spectral intensity distribution of the reflected light is recovered from the time-domain waveform by using an envelope extraction algorithm (such as Hilbert transform, square-law detection, etc.) or by directly performing an inverse Fourier transform.

[0037] Since different time points correspond to different wavelengths, the time axis can be calibrated as the wavelength axis, thereby obtaining the reflection intensity of each wavelength component, i.e., "reflectivity information of different wavelength components". This enables high-speed spectral demodulation without the need for traditional spectrometers. The detection speed is determined by the oscilloscope's 900 sampling rate (up to the GHz level), which is far higher than that of CCD spectrometers (kHz level), laying the foundation for ultrafast imaging.

[0038] S402. Determine the reflection intensity of each depth layer based on the pre-calibrated mapping relationship between wavelength and longitudinal depth.

[0039] Specifically, the chromatic dispersive lens element 300 exhibits strong wavelength-dependent focal length characteristics, meaning that shorter wavelengths focus at farther positions, while longer wavelengths focus at closer positions. Therefore, the system design establishes a one-to-one correspondence between wavelength λ and longitudinal depth z, i.e., the "wavelength-depth mapping function z(λ)". The "reflectivity of each wavelength" data obtained in S401 is converted into "reflection intensity of each depth layer" according to the calibrated λ-z mapping relationship. In this way, a single pulse measurement can obtain one-dimensional profile information of the measured point along the depth direction (Z-axis), equivalent to an "optical slice". Replacing the traditional Z-axis mechanical scanning with "wavelength-encoded depth" enables "single illumination, full-depth parallel detection," significantly improving axial scanning speed.

[0040] S403. Combining the lateral position information of the displacement platform 500, the three-dimensional morphological data of the surface of the measured object 400 is reconstructed.

[0041] Specifically, the displacement platform 500 precisely moves the object under test 400 in the XY plane, allowing the longitudinal focal spot of the ultrashort pulse laser to sequentially scan every lateral position (x, y) on the surface of the object under test 400. For each lateral point scanned, the system completes the aforementioned "spectral → temporal → depth profile" demodulation, obtaining the Z-axis topographic data at that point. For each lateral coordinate (x, y), the system records its corresponding depth profile (z), organizing the reflection intensity at all (x, y, z) positions into a three-dimensional data cube. Using image processing algorithms (such as peak detection, threshold segmentation, surface tracking, etc.), the z-value with the strongest reflection at each (x, y) position is extracted, which is the surface depth of that point. Finally, a three-dimensional point cloud map or digital elevation model of the object under test 400 is generated and visualized as a three-dimensional topographic image.

[0042] Example 3: According to an embodiment of the present invention, a three-dimensional imaging system based on ultrashort pulse laser and chromatic confocal imaging is provided. Please refer to [link to relevant documentation]. Figures 1 to 3 .

[0043] The ultrashort pulse laser output from the ultrashort pulse laser 100 enters the first port 1 of the fiber optic circulator 201 through an optical fiber, and is output from the second port 2 of the fiber optic circulator 201 to an achromatic doublet lens for collimation. The collimated beam passes through a Fresnel zone plate and converges into a longitudinal focal spot at a focal length linearly related to the wavelength. The displacement platform 500 positions the object under test 400 at the longitudinal focal spot. The object under test 400 reflects a divergent beam of emitted light. The divergent reflected light is reflected back through the Fresnel zone plate and converged into parallel light, which is injected into the achromatic doublet lens, converged again into the optical fiber, input to the second port 2 of the fiber optic circulator 201, and output from the third port 3 of the fiber optic circulator 201. Each pulse of light is measured repeatedly. The reflectivity of different wavelength components in the reflected light can be calculated to obtain reflectivity information at different longitudinal depth positions. The photodetector 800 collects light signals (light intensity) and converts them into electrical signals (voltage). The oscilloscope 900 samples, stores, and displays the electrical signals (in digital form) as waveforms in the time domain. The signal processing module converts the collected signals into longitudinal image information of the object under test 400 and displays it. After the displacement platform 500 scans the horizontal plane, it reconstructs and displays the three-dimensional image information of the object under test 400, thus realizing ultrafast one-dimensional longitudinal imaging with the pulse repetition frequency as the measurement refresh frame rate and three-dimensional imaging with the time of a single horizontal scan as the period.

[0044] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0045] Optionally, specific examples in this embodiment can refer to the examples described in the above embodiments, and will not be repeated here.

[0046] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0047] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0048] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A three-dimensional imaging system based on ultra-short pulsed laser and chromatic confocal, characterized in that, The application relates to a three-dimensional scanning system and a three-dimensional scanning method. The application comprises: a super-short pulse laser for outputting super-short pulse laser with wide spectrum characteristics; a chromatic dispersion lens element configured to focus different wavelength components of the super-short pulse laser to different longitudinal positions in the direction of the optical axis, forming longitudinal focal spots distributed along the optical axis; a confocal microscopic light path structure configured to form a detection focal point conjugated with a measured focal point, so that reflected light from the measured focal point converges to the detection focal point after returning along the original path, the measured focal point being a light spot formed on the surface of a measured object after the super-short pulse laser is focused by the chromatic dispersion lens element; a displacement platform for driving the measured object to move in a transverse plane perpendicular to the optical axis, so as to realize three-dimensional scanning of the measured object; and 2. The three-dimensional imaging system based on ultra-short pulse laser and chromatic confocal according to claim 1, characterized in that, a dispersion Fourier transform module for converting the spectral information of the reflected light into a time-domain pulse waveform. The confocal microscopic light path structure comprises: a collimating lens for collimating the super-short pulse laser and converging the reflected light; and 3. The three-dimensional imaging system based on ultra-short pulse laser and chromatic confocal according to claim 1, characterized in that, a fiber optic circulator, a first port of which is connected to the super-short pulse laser, a second port of which is connected to the collimating lens, and a third port of which outputs the reflected light reflected by the measured focal point, the reflected light being transmitted to the dispersion Fourier transform module, and the detection focal point being located at the end of the optical fiber connected to the second port of the fiber optic circulator.

4. The three-dimensional imaging system based on ultra-short pulse laser and chromatic confocal according to claim 1, characterized in that, The chromatic dispersion lens element is a Fresnel zone plate, a four-phase level diffraction lens, an eight-phase level diffraction lens, a dispersion lens or a metasurface lens.

5. The three-dimensional imaging system based on ultra-short pulse laser and chromatic confocal according to claim 1, characterized in that, The dispersion Fourier transform module comprises a transmission medium with group velocity dispersion, and the transmission medium is a single-mode optical fiber, a dispersion compensation optical fiber, a few-mode optical waveguide or a chirped Bragg fiber grating. The application further comprises a time lens module and a photodetector. The time lens module is connected to the output end of the dispersion Fourier transform module and is used for stretching and amplifying the converted time-domain pulse waveform.

6. The three-dimensional imaging system based on ultra-short pulse laser and chromatic confocal according to claim 5, characterized in that, The photodetector is used for converting the stretched and amplified optical signal into an electrical signal.

7. A method for three-dimensional imaging based on the chromatic confocal system of any one of claims 1-6, characterized in that, The application further comprises an oscilloscope connected to the output end of the photodetector and used for collecting and displaying the time-domain waveform of the electrical signal. The application comprises the following steps: S100. Generating super-short pulse laser with wide spectrum characteristics by a super-short pulse laser; S200. Focusing different wavelength components of the super-short pulse laser to different longitudinal positions in the direction of the optical axis by a chromatic dispersion lens element, to form longitudinal focal spots; S300. Driving a measured object to move in a transverse plane by a displacement platform, and collecting reflected light by a confocal microscopic light path structure; 8. The method of claim 7, wherein, S400. Converting the spectral information of the reflected light into a time-domain pulse waveform by a dispersion Fourier transform module, and reconstructing a three-dimensional topographic image of the measured object based on the time-domain pulse waveform.

9. The method of claim 7, wherein, The longitudinal focal spots are distributed along the Z axis, and the displacement platform drives the measured object to move in the X-Y plane, so that the to-be-measured points on the measured object pass through the longitudinal focal spot region in sequence, to realize transverse spatial sampling. In S400, the reconstruction process of the three-dimensional topographic image comprises: demodulating the time-domain pulse waveform to obtain reflectivity information of different wavelength components; According to the pre-calibrated mapping relationship between the wavelength and the longitudinal depth, the reflection intensity of each depth layer is determined; Combined with the lateral position information of the displacement platform, the three-dimensional topography data of the measured object surface is reconstructed.

Images