Surface morphology detection method and system based on dual-comb surface frequency scanning

Abstract

The present application discloses a surface morphology detection method and system based on dual-comb surface frequency sweeping, which relates to the technical field of surface morphology detection. In the present application, surface frequency sweeping is used to enable the dual-comb to realize the frequency sweeping function, thereby making it possible for the dual-comb light source capable of high-precision ranging to be applied in the interference optical path to realize area array ranging. In this way, the use of dual-comb frequency sweeping replaces the traditional light source frequency sweeping, and the use of dual-comb multi-heterodyne interference combined with surface frequency sweeping greatly improves the measurement accuracy of the longitudinal depth, thereby improving the accuracy of three-dimensional reconstruction based on the longitudinal depth, achieving ultra-high resolution that breaks through the micron level and reaches the sub-nanometer level. In fact, atomic-level surface morphology detection with a longitudinal resolution of ≤0.1nm can be achieved.

Description

Technical Field

[0001] The present application relates to the technical field of surface morphology detection, and in particular to a surface morphology detection method based on dual-optical comb surface frequency sweeping, and a surface morphology detection system based on dual-optical comb surface frequency sweeping. Background Art

[0002] Swept-source coherence tomography (SS-OCT) is a widely used atomic-scale surface topography detection technology. It relies on mechanical sweeping or spectral domain detection. While it enables non-contact measurement, its resolution is limited: SS-OCT's axial resolution is limited by the light source bandwidth and system noise, making it difficult to break through the micron level and achieve sub-nanometer resolution.

[0003] The above content is only used to assist in understanding the technical solution of this application and does not constitute an admission that the above content is prior art. Summary of the Invention

[0004] The main purpose of this application is to provide a surface morphology detection method based on dual-comb surface scanning and a surface morphology detection system based on dual-comb surface scanning, aiming to solve the technical problem of insufficient detection resolution of swept source coherence tomography (SS-OCT).

[0005] To achieve the above objectives, the present application proposes a surface topography detection method based on dual-comb surface frequency sweeping, the surface topography detection method based on dual-comb surface frequency sweeping comprising:

[0006] A first light beam is obtained by coupling the respective light beams of the dual-comb light source;

[0007] Dynamically adjusting the wavelength of the first light beam through a surface frequency sweep module to obtain a second light beam;

[0008] Performing area array detection on the sample to be measured based on the second light beam to obtain a dual-comb multi-heterodyne interference signal;

[0009] Based on the dual-comb multi-heterodyne interference signal, the surface morphology of the sample to be measured is detected.

[0010] In one embodiment, the step of performing area array detection on the sample to be measured based on the second light beam to obtain a dual-comb multi-heterodyne interference signal includes:

[0011] The second light beam is polarized and split into a reference beam and a sample beam. The return light of the sample beam after being simultaneously focused to the sample to be measured by a microlens array is combined with the reference beam to form a combined beam. The combined beam is detected by a photodetector to obtain a dual-comb multi-heterodyne interference signal.

[0012] In one embodiment, the step of detecting the surface morphology of the sample to be tested based on the dual-comb multi-heterodyne interference signal includes:

[0013] Determining a distance measurement of the sample to be measured based on the dual-comb multi-heterodyne interference signal, wherein the distance measurement is the distance between the surface of the sample to be measured and a preset standard plane;

[0014] The measured distance is used as one-dimensional depth information of the sample to be measured, and the surface morphology of the sample to be measured is detected based on the one-dimensional depth information.

[0015] In one embodiment, the step of dynamically adjusting the wavelength of the first light beam by using a surface frequency sweep module to obtain the second light beam includes:

[0016] The swept beam obtained by dynamically adjusting the wavelength of the first beam through the surface sweep module is sequentially passed through the spatial light modulation module for light wave modulation and the beam shaping module for adjusting the light intensity distribution to form an ideal output beam, and the ideal output beam is used as the second beam.

[0017] In one embodiment, the step of obtaining the first light beam by coupling the light beams of the dual-comb light sources includes:

[0018] The third semi-transparent and semi-reflective mirror is used as a polarization beam combiner, and the light beams of the dual comb light sources pass through the third semi-transparent and semi-reflective mirror, so that the light beams of the dual comb light sources have orthogonal polarization states, thereby obtaining first light beams with orthogonal polarization states.

[0019] In addition, to achieve the above-mentioned purpose, the present application also proposes a surface topography detection system based on dual-comb surface frequency sweeping, the surface topography detection system based on dual-comb surface frequency sweeping comprising: a dual-comb light source, a surface frequency sweeping module, an interferometry module, and a signal processing module;

[0020] The surface frequency sweeping module is used to dynamically adjust the wavelength of the first light beam obtained by coupling the respective light beams of the dual-comb light source to obtain the second light beam, wherein dynamically adjusting the wavelength of the first light beam is called frequency sweeping;

[0021] The interferometry module is configured to polarization-split the second light beam into a reference beam and a sample beam, wherein the return light of the sample beam after being simultaneously focused onto the sample to be measured by a microlens array is combined with the reference beam to form a combined beam, and the combined beam is detected by a photodetector to obtain a dual-comb multi-heterodyne interference signal, wherein the dual-comb multi-heterodyne interference signal is the interference signal corresponding to each of the dual combs;

[0022] The signal processing module is used to detect the surface morphology of the sample to be tested based on the dual-comb multi-heterodyne interference signal.

[0023] In one embodiment, the interferometry module includes: a first semi-transparent and semi-reflective mirror, a reference mirror, a second reflective mirror, a microlens array, a projection objective lens, a second semi-transparent and semi-reflective mirror, and a photodetector; wherein the photodetector includes a first ultra-high-speed area array detector and a second ultra-high-speed area array detector;

[0024] The first semi-transparent and semi-reflective mirror is used for polarization-splitting the second light beam into a reference beam and a sample beam;

[0025] The first optical path of the sample light beam is: the second reflector, the microlens array, the projection objective lens, the sample to be measured, the projection objective lens, the microlens array, the second reflector, and the first semi-transparent and semi-reflective mirror;

[0026] The second optical path of the reference beam is: a reference mirror and a first semi-transparent and semi-reflective mirror;

[0027] The first semi-transparent and semi-reflective mirror is further used to combine the sample beam after passing through the first optical path and the reference beam after passing through the second optical path to form a combined beam;

[0028] The second semi-transparent and semi-reflective mirror is used to split the combined light beam into a first ultra-high-speed area array detector and a second ultra-high-speed area array detector respectively, so as to obtain a dual-comb multi-heterodyne interference signal.

[0029] In one embodiment, a surface morphology detection system based on dual-comb surface frequency sweeping further includes: a spatial light modulation module and a beam shaping module; wherein the swept light beam obtained by dynamically adjusting the wavelength of the first light beam through the surface frequency sweeping module sequentially passes through the spatial light modulation module for light wave modulation and the beam shaping module for adjusting the light intensity distribution to form an ideal output light beam, and the ideal output light beam is used as the second light beam.

[0030] In one embodiment, the surface morphology detection system based on dual-comb surface scanning also includes: a polarization semi-transparent and semi-reflective mirror; and a third semi-transparent and semi-reflective mirror is used as a polarization beam combiner to pass the respective light beams of the dual-comb light sources through the third semi-transparent and semi-reflective mirror, so that the respective light beams of the dual-comb light sources have orthogonal polarization states, thereby obtaining a first light beam with an orthogonal polarization state.

[0031] In addition, to achieve the above-mentioned purpose, the present application also proposes a storage medium, which is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by the processor, the steps of the surface morphology detection method based on dual-comb surface frequency scanning as described above are implemented.

[0032] In addition, to achieve the above-mentioned purpose, the present application also provides a computer program product, which includes a computer program, and when the computer program is executed by a processor, it implements the steps of the surface morphology detection method based on dual-comb surface frequency scanning as described above.

[0033] One or more technical solutions proposed in this application have at least the following technical effects:

[0034] In this application, surface frequency sweeping is used to enable a dual-comb system to achieve frequency sweeping, thereby enabling the application of a dual-comb light source capable of high-precision distance measurement in an interferometric optical path to achieve area array distance measurement. Thus, by replacing traditional light source frequency sweeping with dual-comb frequency sweeping and combining dual-comb multi-heterodyne interferometry with surface frequency sweeping, the measurement accuracy of longitudinal depth is greatly improved, thereby further improving the accuracy of 3D reconstruction based on longitudinal depth, achieving ultra-high resolution beyond the micron level and reaching the sub-nanometer level. In fact, atomic-level surface topography detection with a longitudinal resolution of ≤0.1nm is achievable. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0036] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0037] Figure 1 A schematic diagram of a surface topography detection system based on dual-comb surface frequency scanning according to an embodiment of the present application;

[0038] Figure 2 A schematic diagram of the method flow provided in an embodiment of the surface morphology detection method based on dual-comb surface frequency scanning of the present application.

[0039] Among them, A1, the first optical comb light source; A2, the second optical comb light source; U, the dual optical comb light source; F1, the first reflector; H1, the first HWP half-wave plate; H2, the second HWP half-wave plate; P1, the first semi-transparent and semi-reflective mirror; T, the surface frequency scanning module; P2, the second semi-transparent and semi-reflective mirror; C, the reference mirror; F2, the second reflector; Z, the microlens array; W, the projection objective; Y, the high-precision motion stage; N, the sample to be measured; P3, the third semi-transparent and semi-reflective mirror; Q1, the first ultra-high-speed area array detector; Q2, the second ultra-high-speed area array detector; H, the spatial light modulation module; G, the beam shaping module; S, the synchronous clock module; K1, the first data acquisition card; K2, the second data acquisition card; X, the signal processing module; J, the computer.

[0040] The purpose, features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0041] It should be understood that the specific embodiments described herein are merely used to explain the technical solutions of the present application and are not intended to limit the present application.

[0042] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0043] The present invention provides a surface topography detection system based on dual-comb surface frequency sweeping. Figure 1 , Figure 1 A schematic diagram of a surface topography detection system based on dual-comb surface scanning is provided for an embodiment of the present application. In this embodiment, the surface topography detection system based on dual-comb surface scanning includes: a dual-comb light source U, a surface scanning module T, an interferometry module, and a signal processing module X;

[0044] The first optical comb source A1 (repetition frequency frip = 201.2 MHz) and the second optical comb source A2 (frip + Δf) pass through their respective first and second HWP half-wave plates H1 and H2, respectively, before being coupled by a polarization beam combiner (third semi-transparent, semi-reflective mirror P3), producing a sequence of orthogonally polarized pulses, the first beam. The second optical comb source A2 passes through the first reflector F1, then the first HWP half-wave plate H1, and finally the third semi-transparent, semi-reflective mirror P3, where it is coupled. VCSEL technology is used to stabilize the carrier-envelope phase (CEP), achieving a frequency accuracy of 10 kHz (traceable to an atomic clock). The VCSEL outputs continuous light, which is modulated to generate mode-locked pulses. The frequency comb's frip and fCEO are compared with an atomic clock reference signal. Error signals are fed back to the VCSEL driver circuit to adjust the current to correct for frequency offset. Under closed-loop control, the carrier-envelope phase (CEP) is stabilized within 10 kHz, achieving strict synchronization with the atomic clock. frep is locked to the harmonics of the atomic clock, such as through a frequency division / multiplication chain; fCEO is reset to zero or a fixed value through the tuning control of the VCSEL.

[0045] The surface frequency sweeping module T is used to dynamically adjust the wavelength of the first light beam obtained by coupling the respective light beams of the dual-comb light source U to obtain the second light beam, wherein the dynamic adjustment of the wavelength of the first light beam is called frequency sweeping;

[0046] The surface frequency sweep module T can be an optoacoustic tuner (AOTF) or an electro-optical modulator (EOM). In this embodiment, the components and methods for implementing the surface frequency sweep are not limited. For example, an optoacoustic tuner (AOTF) drives the surface frequency sweep: when incident light strikes the grating, Bragg diffraction is generated. The wavelength of the diffracted light has a one-to-one correspondence with the frequency of the high-frequency drive signal. Therefore, simply changing the frequency of the RF drive signal can change the wavelength of the diffracted light, thereby achieving the purpose of frequency sweeping.

[0047] The interference measurement module is used to perform area array detection on the sample to be measured N based on the second light beam to obtain a dual-comb multi-heterodyne interference signal; specifically, the second light beam is polarization-split into a reference beam and a sample beam, wherein the return light of the sample beam after being simultaneously focused to the sample to be measured N through the microlens array Z is combined with the reference beam to form a combined beam, and the combined beam is detected by a photodetector to obtain a dual-comb multi-heterodyne interference signal, which is the interference signal corresponding to each of the dual combs.

[0048] The signal processing module X is used to detect the surface morphology of the sample N to be tested based on the dual-comb multi-heterodyne interference signal.

[0049] In one embodiment, the dual-comb light source U passes through a third semi-transparent mirror P3, so that the first and second comb light sources A1 and A2 have orthogonal polarization states. Next, the area frequency sweep synchronization is performed: the AOTF sweeps at a rate of 1 MHz. The swept light source, i.e., the second light beam, passes through the spatial light modulation module H and the beam shaping module G to form an ideal output light. After the ideal output light passes through the first semi-transparent mirror P1, the reflected light reaches the reference mirror C. The transmitted light passes through the second reflector F2, the microlens array Z, and the projection objective lens W to reach the sample to be measured N. The return light of the two passes through the first semi-transparent mirror P1 and is combined. After passing through the second semi-transparent mirror P2, the combined light is detected by two photodetectors, i.e., the first ultra-high-speed area array detector Q1 and the second ultra-high-speed area array detector Q2, respectively, to obtain a dual-comb multi-heterodyne interference signal. Finally, in the area of signal processing and imaging, machine learning models (such as convolutional neural networks) are introduced to optimize deconvolution algorithms, improving the efficiency of complex surface reconstruction. Specifically, when constructing 3D models, points that are calculated incorrectly or even illogically incorrectly can be identified using the optimized deconvolution algorithm and can be deleted or their credibility and weight can be reduced. For example, the ID-OCTA algorithm can be used to generate atomic-level 3D topography images.

[0050] In a feasible embodiment, the surface morphology detection system based on dual-comb surface scanning also includes: a third semi-transparent and semi-reflective mirror P3; the third semi-transparent and semi-reflective mirror P3 is used as a polarization beam combiner to pass the respective light beams of the dual-comb light source U through the third semi-transparent and semi-reflective mirror P3, so that the respective light beams of the dual-comb light source U have orthogonal polarization states, thereby obtaining a first light beam with orthogonal polarization states.

[0051] In another feasible embodiment, the surface morphology detection system based on dual-comb surface frequency scanning also includes: a spatial light modulation module H and a beam shaping module G; wherein, the swept light beam obtained by dynamically adjusting the wavelength of the first light beam through the surface frequency scanning module T passes through the spatial light modulation module H for light wave modulation and the beam shaping module G for adjusting the light intensity distribution in sequence to form an ideal output light beam, and the ideal output light beam is used as the second light beam.

[0052] A spatial light modulation module (SLM) is an optical device used to dynamically modulate the spatial distribution of light waves. This precise control is achieved by changing the amplitude, phase, polarization, or wavelength of light. Specifically, amplitude modulation: By varying the intensity of light, an SLM can control the amplitude distribution of light waves, for example, generating specific intensity patterns in optical imaging. Phase modulation: By changing the phase distribution of light waves, complex interference patterns or holograms can be generated, enabling three-dimensional displays or wavefront shaping. Polarization modulation: By adjusting the polarization state of light, an SLM can be used for polarization imaging or polarization-encoded communications. Wavelength modulation: By changing the wavelength of light, multispectral imaging or spectral analysis can be achieved. For example, an acousto-optic modulator (AOM) can be used to exploit the periodic refractive index changes induced by acoustic waves in a crystal to induce Bragg diffraction of the incident light, achieving intensity and frequency modulation. Alternatively, a liquid crystal spatial light modulator (LC-SLM) can be used to control the alignment of liquid crystal molecules using voltage to alter the phase or amplitude distribution of light waves.

[0053] Among them, the core goal of the beam shaping module is to convert a non-uniform light beam (such as a Gaussian beam) into a light field distribution of a specific shape (such as a flat-top beam, annular light, multi-focal array, etc.) to improve the uniformity of the light field. This can be achieved based on specially designed lenses, polarizers and gratings to meet detection requirements.

[0054] In another feasible embodiment, the interferometry module includes: a first semi-transparent and semi-reflective mirror P1, a reference mirror C, a second reflective mirror F2, a microlens array Z, a projection objective lens W, a second semi-transparent and semi-reflective mirror P2, and a photodetector; wherein the photodetector includes a first ultra-high-speed array detector Q1 and a second ultra-high-speed array detector Q2;

[0055] The first semi-transparent and semi-reflective mirror P1 is used for polarization-splitting the second light beam into a reference beam and a sample beam;

[0056] The first optical path of the sample beam is: the second reflector F2, the microlens array Z, the projection objective lens W, the sample N to be measured, the projection objective lens W, the microlens array Z, the second reflector F2, and the first semi-transparent mirror P1;

[0057] The second optical path of the reference beam is: reference mirror C, first semi-transparent and semi-reflective mirror P1;

[0058] The first semi-transparent and semi-reflective mirror P1 is further used to combine the sample beam after passing through the first optical path and the reference beam after passing through the second optical path to form a combined beam;

[0059] The second semi-transparent and semi-reflective mirror P2 is used to split the combined light beam into the first ultra-high-speed area array detector Q1 and the second ultra-high-speed area array detector Q2 respectively, to obtain a dual-comb multi-heterodyne interference signal.

[0060] The first ultra-high-speed area array detector Q1 is controlled by the first data acquisition card K1, while the second ultra-high-speed area array detector Q2 is controlled by the second data acquisition card K2. The synchronized acquisition clocks of the two acquisition cards are calculated by comparing the frequency difference between the two optical combs' temporal consistency Δt using the dual-comb light source U. This is then delivered to both acquisition cards simultaneously by the synchronization clock module S. Simultaneously, computer J controls the high-precision motion stage Y to coordinate the movement of the sample N under test and issues processing instructions to the signal processing module X to obtain the surface topography of the sample N under test.

[0061] In current atomic-level surface morphology detection technologies, such as swept-source coherence tomography (SS-OCT), a wide-bandwidth laser is often used to sweep a single light source. Through the interference of the single light source itself, the Z-direction, or axial depth, of the sample N to be tested is calculated, thereby forming the surface morphology of the sample N to be tested and further performing its surface morphology detection.

[0062] It should be noted that dual-comb ranging technology and surface topography detection technology represented by swept-source coherence tomography (SS-OCT) belong to two independent technical fields. Dual-comb ranging technology is often used for ranging, while swept-source interferometry is often used for detecting three-dimensional surface topography. When implementing their respective functions, they do not easily consider the technical content of the other (dual-comb ranging technology is difficult to think of for surface topography detection, and surface topography detection technology is difficult to think of using dual-comb ranging technology). The reasons are as follows:

[0063] 1. It is difficult for a dual-comb light source to output a single frequency for ranging or topography measurement.

[0064] 2. When the accuracy of current atomic-level surface morphology detection technologies, such as swept-source coherence tomography (SS-OCT), is limited and cannot meet higher precision requirements, the reason for this is generally easy to think of as being related to the central wavelength and bandwidth of the single-frequency laser. Under the influence of these two parameters, the central wavelength and bandwidth of the laser are often optimized.

[0065] Therefore, when seeking breakthroughs in surface morphology detection, it is difficult to think of replacing the light source. People are not even aware of the existence of dual-comb light sources, let alone replacing the light source with a dual-comb light source.

[0066] On this basis, in an embodiment of the present application, 1. Taking into account the accuracy advantage of the dual-comb light source in ranging, its point ranging is extended to the ranging of each point in the array. Thus, the ranging distance of each point of the N array of samples to be measured obtained by determining the dual-comb multi-heterodyne interference signal is used as the one-dimensional depth information of the sample N to be measured, and the surface morphology of the sample N to be measured is determined based on the one-dimensional depth information.

[0067] Furthermore, surface topography detection technologies, such as swept-source coherence tomography (SS-OCT), suffer from slow detection speeds and low efficiency, making high-efficiency detection difficult to achieve. Furthermore, simply replacing the light source with a dual-comb source presents a new problem: a dual-comb source uses broadband, multi-frequency light and cannot achieve frequency sweeping. Consequently, high-precision acquisition of one-dimensional depth information of the sample N under test using a dual-comb source is impossible.

[0068] On this basis, to address the aforementioned issues of surface topography detection efficiency and the inability to achieve frequency sweeping after replacing the light source with a dual-comb light source, in an embodiment of the present application, 2. To achieve the frequency sweeping function of the dual-comb light source, a surface frequency sweeping module T, such as an optical acoustic tuner (AOTF) or an electro-optical modulator (EOM), is employed to output a single frequency from the light source. 3. Furthermore, a spatial light modulation module H, which cooperates with the dual-comb light source, and a beam shaping module G, which cooperates with the surface frequency sweeping module T, are added to output an ideal output beam. 4. Furthermore, a microlens array Z, such as a 1000*1000 microlens array, and a projection objective W are employed to achieve area array detection. The parallel light emitted by the second reflector F2 is simultaneously focused onto the sample N to be tested. A single measurement can achieve simultaneous one-dimensional depth information measurement at millions of acquisition points, greatly improving detection efficiency. 5. Finally, a first semi-transparent mirror P1 and an ultra-high-speed area array detector array (a first ultra-high-speed area array detector Q1 and a second ultra-high-speed area array detector Q2) are added to the optical path to capture the photoelectric signal.

[0069] The above-mentioned 1 and 2 methods combine dual-comb light sources and area array scanning to achieve surface topography detection. Dual-comb scanning replaces traditional light source scanning, significantly improving vertical depth measurement accuracy. Building on 1 and 2, 3, 4, and 5 further enhance detection accuracy. Using a microlens array Z and projection objective W for area array detection allows for the acquisition of millions of points of vertical depth data in a single measurement, significantly improving detection efficiency.

[0070] The present invention provides a surface topography detection method based on dual-comb surface frequency sweeping. Figure 1 , Figure 1 This is a flow chart of an embodiment of a surface topography detection method based on dual-comb surface sweep frequency in this application. In this embodiment, the surface topography detection method based on dual-comb surface sweep frequency includes steps S10 to S40:

[0071] Step S10, obtaining a first light beam by coupling the respective light beams of the dual-comb light source;

[0072] In a feasible implementation, step S10 may include:

[0073] The third semi-transparent and semi-reflective mirror is used as a polarization beam combiner, and the light beams of the dual comb light sources are passed through the third semi-transparent and semi-reflective mirror, so that the light beams of the dual comb light sources have orthogonal polarization states, thereby obtaining first light beams with orthogonal polarization states.

[0074] Step S20, dynamically adjusting the wavelength of the first light beam through the area frequency sweep module to obtain a second light beam;

[0075] In another feasible implementation, step S20 may include:

[0076] The swept beam obtained by dynamically adjusting the wavelength of the first beam through the surface sweep module is sequentially passed through the spatial light modulation module for light wave modulation and the beam shaping module for adjusting the light intensity distribution to form an ideal output beam, and the ideal output beam is used as the second beam.

[0077] Step S30, performing area array detection on the sample to be tested based on the second light beam to obtain a dual-comb multi-heterodyne interference signal;

[0078] In another feasible implementation, step S30 may include:

[0079] The second light beam is polarization-split into a reference beam and a sample beam. The return light of the sample beam after being simultaneously focused onto the sample to be measured by the microlens array is combined with the reference beam to form a combined beam, and the combined beam is detected by a photodetector to obtain a dual-comb multi-heterodyne interference signal.

[0080] Step S40: detecting the surface morphology of the sample to be tested based on the dual-comb multi-heterodyne interference signal.

[0081] In another feasible implementation, step S40 may include:

[0082] Determine the distance between the sample to be measured and the preset standard plane based on the dual-comb multi-heterodyne interference signal;

[0083] The distance between the surface of the sample to be measured and a preset standard plane is used as the one-dimensional depth information of the sample to be measured, and the surface topography of the sample to be measured is detected based on this one-dimensional depth information. The preset standard plane can be the upper or lower surface of a microlens array or a projection objective lens. For example, in extreme cases, the optical path length of the sample beam can be directly used as the distance measurement distance.

[0084] The 3D reconstruction algorithm combines signal processing and image generation techniques to integrate one-dimensional depth information (A-scan) and two-dimensional lateral scans (B-scan) into 3D volume data, achieving the conversion from raw signals to high-precision 3D volume data. During data preprocessing, the one-dimensional depth signal obtained by the A-scan often contains noise. Time-frequency filtering techniques such as wavelet transform or fast Fourier transform (FFT) are used to reduce noise and ensure signal purity. For B-scan image sequences, multi-frame alignment is achieved through feature matching or mutual information maximization to eliminate artifacts caused by object movement. The iterative closest point (ICP) algorithm is used to accurately align multi-view images and unify these data into a global coordinate system. During the multimodal data fusion and interpolation stage, the TSDF (Truncated Signed Distance Function) algorithm is used to fuse the 3D point cloud generated by the A-scan depth information with the spatial distribution constraints provided by the B-scan to construct a continuous surface model. This effectively fills potential data gaps and enhances the continuity and integrity of the terrain or object surface. Finally, by converting the point cloud data into a voxel grid and applying the Marching Cubes surface reconstruction algorithm, a detailed 3D model is generated, integrating the scattered information into 3D volume data with high detail and accuracy.

[0085] Specifically in this embodiment, the one-dimensional depth information of the A-scan is replaced by the ranging distance of each point of the sample array to be measured obtained by dual-comb frequency sweep ranging.

[0086] The depth information calculation formula of A-scan is:

[0087]

[0088] In the above formula, h represents the one-dimensional depth of A-scan, c represents the speed of light in vacuum, and n grepresents the group refractive index of air (the group refractive index of air is a parameter that describes the degree to which the group velocity of light waves propagating in air slows down relative to the speed of light in a vacuum), Δt represents the peak interval of the frequency-doubled signal after asynchronous optical sampling and amplification to curve fitting, Δf represents the fixed repetition frequency difference between the signal comb and the local oscillator comb, and this frequency difference Δf is the frequency difference between the dual-comb multi-heterodyne interference signals. Referring to the introduction of the dual-comb light source mentioned above, we can see that the first comb light source A1 (repetition frequency frep) and the second comb light source A2 (frep+Δf).

[0089] The two optical comb light sources overlap in time, meaning different times correspond to different frequencies. For example, the first optical comb light source A1 sweeps its visible light wavelength from 380nm to 780nm, and the first ultra-high-speed area array detector detects its beam. The second optical comb light source A2 sweeps its wavelength from 381nm to 781nm, and the second ultra-high-speed area array detector detects its beam. At one moment, when the first optical comb light source A1 is at 380nm, there is no light source signal from the second optical comb light source A2. At another moment, when the first optical comb light source A1 is at 381nm, there is a 381nm light source signal from the second optical comb light source A2. At yet another moment, when the second optical comb light source A2 is at 781nm, there is no light source signal from the first optical comb light source A1. Therefore, in a waveform graph with frequency on the horizontal axis and light intensity (amplitude) on the vertical axis, a single detection by the area array detector can only detect one point in the waveform, namely, the amplitude corresponding to a specific frequency. Thus, by frequency sweeping, the response of the first optical comb light source A1 between 380nm and 780nm and the response of the second optical comb light source A2 between 381nm and 781nm, i.e., all points, are combined into response curves and frequency sweep curves. The difference between the response curves of the two optical comb light sources in the waveform diagram, namely Δf and Δt, can be used to calculate the distance measured at each point on the sample array.

[0090] In one application scenario, an atomic-level morphology detection system based on dual-comb interferometry and surface frequency scanning technology is provided. The dual-comb light source consists of two Yb-doped fiber combs with a repetition frequency difference of Δf = 5.4 kHz (source A has a repetition frequency fr of 201.2 MHz, and source B has a repetition frequency fr + Δf). Polarization combining is used to output orthogonally polarized pulse trains. VCSEL technology is used to stabilize the carrier-envelope phase (CEP) to a precision of 10 kHz (traceable to an atomic clock), ensuring that the frequency combs f rep and f CEO are strictly synchronized with the atomic clock through closed-loop control. The area frequency sweep module T uses an acousto-optic modulator (AOTF) to dynamically adjust the wavelength of the diffracted light at a rate of 1 MHz, achieving continuous frequency sweeping. The interferometry module uses polarization beam splitting to split the light source into reference and sample light, generating multi-heterodyne signals in the interferometer, which are captured by a photodetector array. The signal processing module X uses the ID-OCTA algorithm to eliminate artifacts in low-signal-to-noise regions and combines it with a convolutional neural network to optimize the deconvolution algorithm. Ultimately, it generates atomic-level 3D topography images, achieving detection accuracy of <1 μm in the lateral direction and <10 nm in the axial direction.

[0091] In another application scenario, an extended detection system based on dual-comb interferometry and surface frequency scanning technology is provided. By extending the central wavelength of the dual-comb light source to 1550nm (bandwidth >150nm, power stability <0.05dB), and employing an electro-optical modulator (EOM) to achieve dynamic frequency sweeping at a 2MHz rate, the system, combined with a PID control algorithm, compensates for frequency drift caused by ambient temperature (accuracy ±0.1%). Its core modules include: The dual-comb light source uses VCSEL technology to lock the repetition rate to the second harmonic of an atomic clock (402.4MHz), with the carrier-envelope phase (fCEO) fixed to zero to improve stability; the area-sweeping module (T) replaces the AOTF with an EOM and works with a high-speed InP detector array (response time <10ns) to capture multi-heterodyne signals; and the signal processing module (X) uses a multi-wavelength fusion algorithm combined with a Transformer network to fuse 1050nm and 1550nm dual-wavelength data to eliminate the effects of material dispersion. The Transformer network also optimizes global feature matching for 3D reconstruction, ultimately generating atomic-level 3D topography with a lateral resolution <0.5μm and an axial resolution <5nm.

[0092] In another application scenario, a portable atomic-level morphology detection system based on a simplified dual-comb light source and a miniaturized scanning module is provided. The system utilizes a monolithic integrated fiber comb (central wavelength 1050nm, bandwidth 50nm, and power stability <0.2dB), directly locking the repetition frequency (frep) and carrier envelope phase (fCEO) to a commercial rubidium atomic clock. The VCSEL modulator is omitted to reduce complexity. The area-sweeping frequency module (T) replaces the AOTF with a MEMS modulator, achieving a 0.5MHz frequency sweep rate with a drive voltage <5V and power consumption <1W, reducing the size to 1 / 10 of traditional solutions. The interferometry module captures multi-heterodyne signals using a folded interferometer (40% smaller). The signal processing module (X) uses a lightweight CNN algorithm (such as MobileNet) and an embedded GPU chip for real-time deconvolution, achieving a computational latency of <0.1s and supporting in-situ defect marking. The resulting 3D topography image has an axial resolution of <20nm. The system measures just 20×20×10cm³ and weighs <5kg, with a single scan time of ≤2s. This reduces costs by 40% compared to traditional solutions and is suitable for on-site rapid inspection scenarios such as real-time defect screening in semiconductor wafer production lines.

[0093] It should be noted that the above examples are only used to understand the present application and do not constitute a limitation on the surface morphology detection method based on dual-comb surface scanning in the present application. More simple transformations based on this technical concept are all within the scope of protection of the present application.

[0094] The present application provides a surface morphology detection system based on dual-comb surface scanning, and the surface morphology detection system based on dual-comb surface scanning includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the surface morphology detection method based on dual-comb surface scanning in the above-mentioned embodiment one.

[0095] The dual-comb surface sweep-based surface topography detection system may include a processing device 1001 (e.g., a central processing unit, a graphics processing unit, etc.), which can perform various appropriate actions and processes based on programs stored in a read-only memory 1002 or loaded from a storage device 1003 into a random access memory 1004. The random access memory 1004 also stores various programs and data required for the operation of the dual-comb surface sweep-based surface topography detection system. The processing device 1001, the read-only memory 1002, and the random access memory 1004 are interconnected via a bus 1005. An input / output interface 1006 is also connected to the bus. Typically, the following systems may be connected to the input / output interface 1006: an input device 1007 including, for example, a touchscreen, touchpad, keyboard, mouse, image sensor, microphone, accelerometer, gyroscope, etc.; an output device 1008 including, for example, a liquid crystal display (LCD), speaker, vibrator, etc.; a storage device 1003 including, for example, a magnetic tape or hard disk; and a communication device 1009. The communication device 1009 can allow the dual-comb surface sweep-based surface topography detection system to communicate wirelessly or wired with other devices to exchange data. Although the figure shows a dual-comb surface sweep-based surface topography detection system with various systems, it should be understood that it is not required to implement or have all of the systems shown. More or fewer systems may be implemented or have alternatively.

[0096] In particular, according to the embodiments disclosed in the present application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, the embodiments disclosed in the present application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program comprising program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network via a communication device, or installed from a storage device 1003, or installed from a read-only memory 1002. When the computer program is executed by the processing device 1001, the above-mentioned functions defined in the method of the embodiment disclosed in the present application are performed.

[0097] The dual-comb surface sweep-based surface topography detection system provided in this application utilizes the dual-comb surface sweep-based surface topography detection method described in the aforementioned embodiment, resolving the technical issue of insufficient resolution in swept-source coherence tomography (SS-OCT). Compared to the prior art, the dual-comb surface sweep-based surface topography detection system provided in this application achieves the same beneficial effects as the dual-comb surface sweep-based surface topography detection method described in the aforementioned embodiment. Other technical features of this dual-comb surface sweep-based surface topography detection system are the same as those disclosed in the aforementioned embodiment and are not further elaborated upon here.

[0098] It should be understood that the various parts disclosed in this application can be implemented using hardware, software, firmware, or a combination thereof. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0099] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

[0100] The present application provides a computer-readable storage medium having computer-readable program instructions (i.e., a computer program) stored thereon, and the computer-readable program instructions are used to execute the surface morphology detection method based on dual-comb surface frequency scanning in the above embodiment.

[0101] The computer-readable storage medium provided in this application may be, for example, a USB flash drive, but is not limited to electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems or devices, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In this embodiment, the computer-readable storage medium may be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system or device. The program code contained on the computer-readable storage medium may be transmitted using any suitable medium, including but not limited to: wires, optical cables, RF (Radio Frequency), etc., or any suitable combination thereof.

[0102] The computer-readable storage medium may be included in the surface topography detection system based on dual-comb surface frequency sweeping, or may exist independently without being assembled into the surface topography detection system based on dual-comb surface frequency sweeping.

[0103] The computer-readable storage medium carries one or more programs. When the one or more programs are executed by a surface morphology detection system based on dual-comb surface frequency sweeping, the surface morphology detection system based on dual-comb surface frequency sweeping: obtains a first light beam by coupling the respective light beams of the dual-comb light sources; dynamically adjusts the wavelength of the first light beam through the surface frequency sweeping module to obtain a second light beam; performs area array detection on a sample to be tested based on the second light beam to obtain a dual-comb multi-heterodyne interference signal; and detects the surface morphology of the sample to be tested based on the dual-comb multi-heterodyne interference signal.

[0104] Computer program code for performing the operations of the present application may be written in one or more programming languages, or a combination thereof, including object-oriented programming languages such as Java, Smalltalk, C++, and conventional procedural programming languages such as "C" or similar programming languages. The program code may be executed entirely on the user's computer, partially on the user's computer, as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0105] The flow charts and block diagrams in the accompanying drawings illustrate the possible architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present application. In this regard, each box in the flow chart or block diagram can represent a module, program segment or a part of code, and the module, program segment or a part of code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order than that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flow chart, and the combination of the boxes in the block diagram and / or flow chart can be implemented by a dedicated hardware-based system that performs the specified function or operation, or can be implemented by a combination of dedicated hardware and computer instructions.

[0106] The modules described in the embodiments of the present application may be implemented in software or hardware, wherein the name of a module does not necessarily limit the unit itself.

[0107] The computer-readable storage medium provided in this application stores computer-readable program instructions (i.e., a computer program) for executing the aforementioned surface topography detection method based on dual-comb surface sweeping. This computer-readable storage medium can address the technical issue of insufficient resolution in swept-source coherence tomography (SS-OCT). Compared to the prior art, the beneficial effects of the computer-readable storage medium provided in this application are similar to those of the surface topography detection method based on dual-comb surface sweeping provided in the aforementioned embodiments, and are not further elaborated here.

[0108] The present application also provides a computer program product, including a computer program, which implements the steps of the surface morphology detection method based on dual-comb surface frequency scanning when executed by a processor.

[0109] The computer program product provided in this application can address the technical issue of insufficient resolution in swept-source coherence tomography (SS-OCT). Compared to existing technologies, the computer program product provided in this application offers the same beneficial effects as the surface topography detection method based on dual-comb surface sweeping provided in the aforementioned embodiments, and therefore will not be further elaborated here.

[0110] The above description is only part of the embodiments of the present application and does not limit the patent scope of the present application. All equivalent structural transformations made by using the contents of the present application specification and drawings under the technical concept of the present application, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A surface topography detection method based on dual-comb surface frequency sweeping, characterized in that: The surface topography detection method based on dual-comb surface frequency sweeping includes: The third semi-transparent and semi-reflective mirror is used as a polarization beam combiner, and the light beams of the dual comb light sources are passed through the third semi-transparent and semi-reflective mirror, so that the light beams of the dual comb light sources have orthogonal polarization states, thereby obtaining first light beams with orthogonal polarization states; The swept beam obtained by dynamically adjusting the wavelength of the first light beam through the area sweeping module is sequentially passed through a spatial light modulation module for light wave modulation and a beam shaping module for adjusting the light intensity distribution to form an ideal output beam, and the ideal output beam is used as the second light beam, wherein dynamically adjusting the wavelength of the first light beam is called sweeping. Polarization-splitting the second light beam into a reference beam and a sample beam, wherein the return light of the sample beam after being simultaneously focused onto the sample to be measured by a microlens array is combined with the reference beam to form a combined beam, and the combined beam is detected by a photodetector to obtain a dual-comb multi-heterodyne interference signal, wherein the dual-comb multi-heterodyne interference signal is the interference signal corresponding to each of the dual combs; Determining a distance measurement of the sample to be measured based on the dual-comb multi-heterodyne interference signal, wherein the distance measurement is the distance between the surface of the sample to be measured and a preset standard plane; The measured distance is used as one-dimensional depth information of the sample to be measured, and the surface morphology of the sample to be measured is detected based on the one-dimensional depth information.

2. A surface topography detection system based on dual-comb surface frequency sweeping, characterized in that: The surface topography detection system based on dual-comb surface frequency sweeping includes: a dual-comb light source, a surface frequency sweeping module, an interferometric measurement module and a signal processing module; The surface frequency sweeping module is used to dynamically adjust the wavelength of the first light beam obtained by coupling the respective light beams of the dual-comb light source to obtain the second light beam, wherein dynamically adjusting the wavelength of the first light beam is called frequency sweeping; The interferometry module is configured to polarization-split the second light beam into a reference beam and a sample beam, wherein the return light of the sample beam after being simultaneously focused onto the sample to be measured by a microlens array is combined with the reference beam to form a combined beam, and the combined beam is detected by a photodetector to obtain a dual-comb multi-heterodyne interference signal, wherein the dual-comb multi-heterodyne interference signal is the interference signal corresponding to each of the dual combs; The signal processing module is configured to determine a ranging distance of the sample to be measured based on the dual-comb multi-heterodyne interference signal, where the ranging distance is the distance between the surface of the sample to be measured and a preset standard plane; use the ranging distance as one-dimensional depth information of the sample to be measured, and detect the surface morphology of the sample to be measured based on the one-dimensional depth information; The surface topography detection system based on dual-comb surface frequency sweeping further includes: a spatial light modulation module and a beam shaping module; wherein a swept beam obtained by dynamically adjusting the wavelength of the first light beam by the surface frequency sweeping module sequentially passes through the spatial light modulation module for light wave modulation and the beam shaping module for adjusting light intensity distribution to form an ideal output beam, and the ideal output beam is used as the second light beam; The surface morphology detection system based on dual-comb surface scanning also includes: a third semi-transparent and semi-reflective mirror; the third semi-transparent and semi-reflective mirror is used as a polarization beam combiner, which is used to pass the light beams of the dual-comb light sources through the third semi-transparent and semi-reflective mirror so that the light beams of the dual-comb light sources have orthogonal polarization states, thereby obtaining a first light beam with orthogonal polarization states.

3. The surface topography detection system based on dual-comb surface frequency sweeping according to claim 2, characterized in that: The interferometry module includes: a first semi-transparent and semi-reflective mirror, a reference mirror, a second reflective mirror, a microlens array, a projection objective lens, a second semi-transparent and semi-reflective mirror, and a photoelectric detector; wherein the photoelectric detector includes a first ultra-high-speed area array detector and a second ultra-high-speed area array detector; The first semi-transparent and semi-reflective mirror is used for polarization-splitting the second light beam into a reference beam and a sample beam; The first optical path of the sample light beam is: the second reflector, the microlens array, the projection objective lens, the sample to be measured, the projection objective lens, the microlens array, the second reflector, and the first semi-transparent and semi-reflective mirror; The second optical path of the reference beam is: a reference mirror and a first semi-transparent and semi-reflective mirror; The first semi-transparent and semi-reflective mirror is further used to combine the sample beam after passing through the first optical path and the reference beam after passing through the second optical path to form a combined beam; The second semi-transparent and semi-reflective mirror is used to split the combined light beam into a first ultra-high-speed area array detector and a second ultra-high-speed area array detector respectively, so as to obtain a dual-comb multi-heterodyne interference signal.

Images