Surface topography detection method and system based on double-optical-comb surface domain frequency sweeping

Abstract

The invention discloses a surface topography detection method and system based on double optical comb surface domain frequency sweeping, and relates to the technical field of surface topography detection. According to the method and the device, the frequency sweeping function of the double optical combs is realized by utilizing the area domain frequency sweeping, so that the double optical comb light source capable of realizing high-precision distance measurement can be applied to an interference light path to realize area array distance measurement. Therefore, double-optical-comb frequency sweeping is used for replacing traditional light source frequency sweeping, double-optical-comb multi-heterodyne interference is combined with surface domain frequency sweeping, the measurement precision of the longitudinal depth is greatly improved, then the precision of three-dimensional reconstruction based on the longitudinal depth is improved, the ultra-high resolution ratio which breaks through the micron level and reaches the sub-nanometer level is achieved, and actually, the measurement precision of the longitudinal depth is improved. The atomic-scale surface topography detection with the longitudinal resolution being less than or equal to 0.1 nm can be realized.

Description

Technical Field

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

[0002] Currently, swept-source optical coherence tomography (SS-OCT) is widely used as an atomic-level surface topography detection technology, which is based on mechanical frequency sweeping or spectral domain detection. Although non-contact measurement can be achieved, its resolution is insufficient: the axial resolution of SS-OCT is limited by the light source bandwidth and system noise, and it is difficult to break through the micron level and reach sub-nanometer resolution.

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

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

[0005] To achieve the above object, the present application proposes a surface topography detection method based on dual-comb surface frequency sweeping, and the surface topography detection method based on dual-comb surface frequency sweeping includes: By coupling the respective beams of the dual-comb light sources, a first beam is obtained; The wavelength of the first beam is dynamically adjusted by a surface frequency sweeping module to obtain a second beam; Based on the second beam, a planar array detection is performed on the sample to be measured to obtain a dual-comb multi-heterodyne interference signal; Based on the dual-comb multi-heterodyne interference signal, the surface topography of the sample to be measured is detected.

[0006] In one embodiment, the step of performing a planar array detection on the sample to be measured based on the second beam to obtain a dual-comb multi-heterodyne interference signal includes: The second beam is polarization beam split into a reference beam and a sample beam. Among them, the sample beam is simultaneously focused by a microlens array onto the reflected light after the sample to be measured, and the combined beam is formed by combining with the reference beam, and the combined beam is detected by a photodetector to obtain a dual-comb multi-heterodyne interference signal.

[0007] In one embodiment, the step of detecting the surface topography of the sample to be measured based on the dual-comb multi-heterodyne interference signal includes: Determine the 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 the one-dimensional depth information of the sample to be measured, and detect the surface topography of the sample to be measured based on the one-dimensional depth information.

[0008] In one embodiment, the step of dynamically adjusting the wavelength of the first light beam through the area-scanning frequency modulation module to obtain a second light beam includes: The frequency-swept light beam obtained by dynamically adjusting the wavelength of the first light beam through the area-scanning frequency modulation module passes through a spatial light modulation module for optical wave modulation and a beam shaping module for adjusting the light intensity distribution in sequence to form an ideal output light beam, and use the ideal output light beam as the second light beam.

[0009] In one embodiment, the step of obtaining a first light beam by coupling the light beams of the dual-comb light sources includes: Use a third semi-transmissive semi-reflective mirror as a polarization beam combiner, and pass the light beams of the dual-comb light sources through the third semi-transmissive semi-reflective mirror so that the light beams of the dual-comb light sources have orthogonal polarization states, and obtain a first light beam with orthogonal polarization states.

[0010] In addition, to achieve the above object, the present application also proposes a surface topography detection system based on dual-comb area-scanning frequency modulation, and the surface topography detection system based on dual-comb area-scanning frequency modulation includes: a dual-comb light source, an area-scanning frequency modulation module, an interference measurement module, and a signal processing module; The area-scanning frequency modulation module is configured to dynamically adjust the wavelength of the first light beam obtained by coupling the light beams of the dual-comb light sources to obtain a second light beam, where dynamically adjusting the wavelength of the first light beam is frequency sweeping; The interference measurement module is configured to polarization beam split the second light beam into a reference light beam and a sample light beam, where the sample light beam is simultaneously focused by a microlens array onto the reflected light after the sample to be measured and combined with the reference light beam to form a combined light beam, and detect the combined light beam through a photodetector to obtain a dual-comb multi-heterodyne interference signal, and 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 detect the surface topography of the sample to be measured based on the dual-comb multi-heterodyne interference signal.

[0011] In one embodiment, the interference measurement module includes: a first semi-transmissive semi-reflective mirror, a reference mirror, a second reflector, a microlens array, a projection objective, a second semi-transmissive semi-reflective mirror, and a photodetector; where the photodetector includes a first ultra-high-speed area array detector and a second ultra-high-speed area array detector; The first semi-transmissive semi-reflective mirror is configured to polarization beam split the second light beam into a reference light beam and a sample light beam; The first optical path of the sample beam is: the second reflector, the microlens array, the projection objective, the sample to be measured, the projection objective, the microlens array, the second reflector, the first semi-transparent and semi-reflective mirror; The second optical path of the reference beam is: the reference mirror, the first semi-transparent and semi-reflective mirror; The first semi-transparent and semi-reflective mirror is also 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 beam into the first ultra-high-speed area array detector and the second ultra-high-speed area array detector respectively to obtain a dual optical comb multi-heterodyne interference signal.

[0012] In one embodiment, the surface topography detection system based on dual optical comb area frequency sweeping further includes: a spatial light modulation module and a beam shaping module; wherein, the frequency-swept beam obtained by dynamically adjusting the wavelength of the first beam through the area frequency sweeping module sequentially passes through the spatial light modulation module for optical 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.

[0013] In one embodiment, the surface topography detection system based on dual optical comb area frequency sweeping further includes: a polarization semi-transparent and semi-reflective mirror; the third semi-transparent and semi-reflective mirror is used as a polarization combiner to make the beams of the dual optical comb light sources pass through the third semi-transparent and semi-reflective mirror respectively, so that the beams of the dual optical comb light sources have orthogonal polarization states to obtain a first beam with orthogonal polarization states.

[0014] In addition, to achieve the above object, the present application also proposes a storage medium, the storage medium is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by a processor, the steps of the surface topography detection method based on dual optical comb area frequency sweeping as described above are implemented.

[0015] In addition, to achieve the above object, the present application also provides a computer program product, the computer program product includes a computer program, and when the computer program is executed by a processor, the steps of the surface topography detection method based on dual optical comb area frequency sweeping as described above are implemented.

[0016] One or more technical solutions proposed by the present application have at least the following technical effects: In this application, the frequency-sweeping function of the dual optical frequency combs is realized by means of area frequency-sweeping, so that it becomes possible to apply the dual optical frequency comb light source capable of high-precision ranging to the interference optical path to realize area array ranging. Thus, the frequency-sweeping of the dual optical frequency combs is used to replace the frequency-sweeping of the traditional light source, and the multi-heterodyne interference of the dual optical frequency combs is combined with area frequency-sweeping to greatly improve the measurement accuracy of the longitudinal depth, and further improve the accuracy in three-dimensional reconstruction based on the longitudinal depth, achieving an ultra-high resolution that breaks through the micron level and reaches the sub-nanometer level. In fact, atomic-level surface topography detection with a longitudinal resolution ≤ 0.1 nm can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with this application, and are used together with the specification to explain the principles of this application.

[0018] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a schematic diagram of the system provided for the embodiment of the surface topography detection system based on the area frequency-sweeping of the dual optical frequency combs of this application; Figure 2 It is a schematic diagram of the method flow provided for the embodiment of the surface topography detection method based on the area frequency-sweeping of the dual optical frequency combs of this application.

[0020] Among them, A1 is the first optical frequency comb light source; A2 is the second optical frequency comb light source; U is the dual optical frequency comb light source; F1 is the first reflector; H1 is the first HWP half-wave plate; H2 is the second HWP half-wave plate; P1 is the first semi-transparent and semi-reflective mirror; T is the area frequency-sweeping module; P2 is the second semi-transparent and semi-reflective mirror; C is the reference mirror; F2 is the second reflector; Z is the microlens array; W is the projection objective; Y is the high-precision moving stage; N is the sample to be measured; P3 is the third semi-transparent and semi-reflective mirror; Q1 is the first ultra-high-speed area array detector; Q2 is the second ultra-high-speed area array detector; H is the spatial light modulation module; G is the beam shaping module; S is the synchronous clock module; K1 is the first data acquisition card; K2 is the second data acquisition card; X is the signal processing module; J is the computer.

[0021] The realization of the purpose, functional features and advantages of this application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] It should be understood that the specific embodiments described here are only used to explain the technical solutions of this application and are not used to limit this application.

[0023] To better understand the technical solution of this application, the following will be described in detail in conjunction with the accompanying drawings of the specification and specific embodiments.

[0024] An embodiment of this application provides a surface topography detection system based on dual optical frequency comb area scanning. Refer to Figure 1 , Figure 1 which is a schematic diagram of the system provided for the embodiment of the surface topography detection system based on dual optical frequency comb area scanning of this application. In this embodiment, the surface topography detection system based on dual optical frequency comb area scanning includes: a dual optical frequency comb light source U, an area scanning module T, an interference measurement module, and a signal processing module X; Among them, the first optical frequency comb light source A1 (repetition frequency frep = 201.2 MHz) and the second optical frequency comb light source A2 (frep + Δf) pass through their respective first HWP half-wave plates H1 and second HWP half-wave plates H2, and then are coupled through a polarization beam combiner, that is, the third half-transmissive and half-reflective mirror P3, to output an orthogonally polarized pulse sequence, that is, the first light beam. Among them, the second optical frequency comb light source A2 passes through the first reflector F1 and then passes through the first HWP half-wave plate H1 until it participates in the coupling at the third half-transmissive and half-reflective mirror P3. The carrier-envelope phase is stabilized by using VCSEL technology, and the frequency accuracy reaches 10 kHz (traceable to an atomic clock). The VCSEL outputs continuous light, which is modulated to generate mode-locked pulses. The frep and fCEO of the frequency comb are respectively compared with the atomic clock reference signal. The error signal is fed back to the VCSEL drive circuit, and the current is adjusted to correct the frequency offset. Under closed-loop control, the carrier-envelope phase (CEP) is stabilized within an accuracy of 10 kHz, realizing 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 zeroed or fixed through the tuning control of the VCSEL.

[0025] The area scanning module T is used to dynamically adjust the wavelength of the first light beam obtained by coupling the respective light beams of the dual optical frequency comb light source U to obtain a second light beam. Among them, dynamically adjusting the wavelength of the first light beam is frequency scanning; The area scanning module T can be an acou-optic tunable filter (AOTF) or an electro-optic modulator (EOM). In this embodiment, the implementation components and implementation methods of area scanning are not limited. For example, the acou-optic tunable filter (AOTF) drives area scanning: when incident light irradiates this grating, Bragg diffraction will occur, and the wavelength of the diffracted light has a one-to-one correspondence with the frequency of the high-frequency driving electrical signal. Therefore, as long as the frequency of the RF driving signal is changed, the wavelength of the diffracted light can be changed, thereby achieving the purpose of frequency scanning.

[0026] The interferometric measurement module is used to perform area array detection on the sample N to be measured based on the second light beam, and obtain a dual-comb multi-heterodyne interference signal. Specifically, the second light beam is polarization beam-split into a reference light beam and a sample light beam. Among them, the sample light beam is simultaneously focused by the microlens array Z onto the back-reflected light of the sample N to be measured, and then combined with the reference light beam to form a combined light beam, and the combined light beam is detected by a photodetector to obtain a dual-comb multi-heterodyne interference signal. The dual-comb multi-heterodyne interference signal is the interference signal corresponding to each of the dual combs.

[0027] The signal processing module X is used to detect the surface topography of the sample N to be measured based on the dual-comb multi-heterodyne interference signal.

[0028] In one embodiment, the dual-comb light source U passes through the third semi-transmissive and semi-reflective mirror P3, so that the first comb light source A1 and the second comb light source A2 have orthogonal polarization states. Then, area-scanning frequency synchronization: The AOTF scans at a rate of 1 MHz. The frequency-scanned light source, that is, 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-transmissive and semi-reflective mirror P1, the reflected light reaches the reference mirror C, and the transmitted light passes through the second reflecting mirror F2, the microlens array Z, and the projection objective W to reach the sample N to be measured. The back-reflected lights of the two are combined after passing through the first semi-transmissive and semi-reflective mirror P1, and the combined light is detected by two photodetectors, namely the first ultra-high-speed area array detector Q1 and the second ultra-high-speed area array detector Q2, to obtain a dual-comb multi-heterodyne interference signal. Finally, signal processing and imaging: Introduce a machine learning model (such as a convolutional neural network) to optimize the deconvolution algorithm and improve the efficiency of complex surface reconstruction. Specifically, for the points used to form the surface with calculation errors or even illogical points used to form the surface during three-dimensional modeling, based on the optimized deconvolution algorithm, these points are found and can be deleted or the credibility and weight of these points can be reduced. For example, use a three-dimensional reconstruction algorithm: the ID-OCTA algorithm to generate an atomic-level three-dimensional topography map.

[0029] In a feasible implementation manner, the surface topography detection system based on dual-comb area-scanning frequency also includes: a third semi-transmissive and semi-reflective mirror P3; using the third semi-transmissive and semi-reflective mirror P3 as a polarization combiner, so that the respective light beams of the dual-comb light source U pass through the third semi-transmissive and semi-reflective mirror P3, so that the respective light beams of the dual-comb light source U have orthogonal polarization states, and a first light beam with orthogonal polarization states is obtained.

[0030] In another feasible implementation manner, the surface topography detection system based on dual-comb area-scanning frequency also includes: a spatial light modulation module H and a beam shaping module G; among them, the frequency-scanned light beam obtained by dynamically adjusting the wavelength of the first light beam through the area-scanning frequency module T passes through the spatial light modulation module H for optical 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.

[0031] Among them, the spatial light modulation module (SLM) is an optical device used to dynamically modulate the spatial distribution of light waves. It can achieve precise control of light waves by changing the amplitude, phase, polarization or wavelength of light. Specifically, amplitude modulation: by changing the intensity of light, SLM can control the amplitude distribution of light waves, such as generating specific intensity patterns in optical imaging. Phase modulation: changing the phase distribution of light waves to generate complex interference patterns or holograms, realize three-dimensional display or wavefront shaping. Polarization modulation: by adjusting the polarization state of light, SLM can be used for polarization imaging or polarization encoding communication. Wavelength modulation: changing the wavelength of light to achieve multi-spectral imaging or spectral analysis. For example, based on an acousto-optic modulator (AOM), the periodic refractive index changes generated by sound waves in the crystal can be used to cause Bragg diffraction of the incident light to achieve light intensity and frequency modulation. Alternatively, based on a liquid crystal spatial light modulator (LC-SLM), the arrangement of liquid crystal molecules can be controlled by voltage to change the phase or amplitude distribution of light waves.

[0032] 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.

[0033] In another feasible implementation, the interferometric measurement 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 photoelectric detector; wherein the photoelectric detector includes a first ultra-high-speed array detector Q1 and a second ultra-high-speed array detector Q2; The first semi-transparent and semi-reflective mirror P1 is used for polarization-splitting the second light beam into a reference light beam and a sample light beam; The first optical path of the sample light beam is: the second reflector F2, the microlens array Z, the projection lens W, the sample N to be measured, the projection lens W, the microlens array Z, the second reflector F2, and the first semi-transparent mirror P1; The second optical path of the reference beam is: reference mirror C, first semi-transparent semi-reflective mirror P1; The first semi-transparent and semi-reflective mirror P1 is also 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 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, so as to obtain a dual-comb multi-heterodyne interference signal.

[0034] The first ultra-high-speed area array detector Q1 is controlled by the first data acquisition card K1 for acquisition, and the second ultra-high-speed area array detector Q2 is controlled by the second data acquisition card K2 for acquisition. The synchronous acquisition clocks of the two data acquisition cards are given by the frequency difference comparison calculation of the dual optical frequency comb source U based on the time consistency Δt of the two optical frequency combs, and are simultaneously given to the two data acquisition cards by the synchronous clock module S. At the same time, the computer J controls the high-precision moving stage Y to move the sample N to be measured in cooperation, and issues a processing instruction to the signal processing module X to obtain the surface topography of the sample N to be measured.

[0035] In current atomic-level surface topography detection technologies such as swept-source optical coherence tomography (SS-OCT), a laser with a relatively wide bandwidth is often used to perform frequency sweeping with a single light source. Through the interference of the single light source itself, the Z-direction, i.e., the axial depth, of the sample N to be measured is calculated to form the surface topography of the sample N to be measured, and further surface topography detection is carried out.

[0036] It should be noted that the dual optical frequency comb source ranging technology and the surface topography detection technology represented by swept-source optical coherence tomography (SS-OCT) belong to two independent technical fields. Among them, dual optical frequency combs are commonly used for ranging, and swept-frequency interference is commonly used for detecting three-dimensional surface topography. When realizing their respective functions, neither of them will easily think of the technical content of the other (it is difficult to think of using the dual optical frequency comb source ranging technology for surface topography detection, and it is difficult to think of using the dual optical frequency comb source for ranging in surface topography detection technology). The reasons are as follows: 1. It is difficult for a dual optical frequency comb source to output a single frequency for ranging or topography measurement.

[0037] 2. In current atomic-level surface topography detection technologies such as swept-source optical coherence tomography (SS-OCT), when the accuracy is limited and cannot meet higher accuracy requirements, when analyzing the reasons, it is generally easy to think that it is related to the central wavelength and bandwidth of the single-frequency laser. Affected by these two parameters, it is often inclined to optimize the central wavelength and bandwidth of the laser.

[0038] Therefore, when seeking a breakthrough in surface topography detection, it is difficult to think of replacing the light source, and even do not know the existence of the dual optical frequency comb source, let alone think of replacing the light source with the dual optical frequency comb source.

[0039] On this basis, in the embodiments of the present application, 1. Considering the accuracy advantage of the dual optical frequency comb source in ranging, the ranging of points is extended to the ranging of each point of the area array. Thus, the ranging distance of each point of the area array of the sample N to be measured determined by the dual optical frequency comb multi-heterodyne interference signal is used as the one-dimensional depth information of the sample N to be measured, and the surface topography of the sample N to be measured is based on this one-dimensional depth information.

[0040] In addition, in surface topography detection techniques represented by swept-source optical coherence tomography (SS-OCT), the detection speed is slow and the detection efficiency is low, making it difficult to achieve high-efficiency detection. At the same time, if only the light source is replaced with a dual-comb light source, new problems will arise: the dual-comb light source is broadband and multi-frequency light, and the frequency-sweeping function cannot be realized. Therefore, it is impossible to further achieve high-precision acquisition of the one-dimensional depth information of the sample N to be measured based on the dual-comb light source.

[0041] On this basis, to solve the above problems of surface topography detection efficiency and the inability to achieve the frequency-sweeping function after replacing the light source with a dual-comb light source, in the embodiments of the present application: 2. To achieve the frequency-sweeping function of the dual-comb light source, a spatial domain frequency-sweeping module T such as an acou-optic tunable filter (AOTF) or an electro-optic modulator (EOM) is used to achieve the output of a single frequency of the light source. 3. Further, a spatial light modulation module H cooperating with the dual-comb light source and a beam shaping module G cooperating with the spatial domain 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 used to achieve area array detection, and the parallel light irradiated by the second mirror F2 is simultaneously focused on the sample N to be measured, and the synchronous measurement of the one-dimensional depth information of millions of acquisition points can be achieved in a single measurement, greatly improving the detection efficiency. 5. Finally, a first semi-transmissive semi-reflective mirror P1 and an ultra-high-speed area array detector array (the first ultra-high-speed area array detector Q1 and the second ultra-high-speed area array detector Q2) cooperating with the optical path are added to capture the optoelectronic signal.

[0042] As described above, through the above 1 and 2, the surface topography detection combining the dual-comb light source and area array frequency-sweeping is realized, and the traditional light source frequency-sweeping is replaced by the dual-comb frequency-sweeping, greatly improving the measurement accuracy of the longitudinal depth. On the basis of the above 1 and 2, further through the above 3, 4, and 5, while improving the detection accuracy, the area array detection is realized by using the microlens array Z + projection objective W, and the longitudinal depth data acquisition of millions of points can be achieved in a single measurement, greatly improving the detection efficiency.

[0043] The embodiments of the present application provide a surface topography detection method based on dual-comb spatial domain frequency-sweeping, referring to Figure 1 , Figure 1 is a schematic flowchart of an embodiment of the surface topography detection method based on dual-comb spatial domain frequency-sweeping of the present application. In this embodiment, the surface topography detection method based on dual-comb spatial domain frequency-sweeping includes steps S10 to S40: Step S10, obtaining a first beam by coupling the respective beams of the dual-comb light source; In a feasible implementation manner, step S10 may include: Take the third semi-transmissive and semi-reflective mirror as a polarization beam combiner, and pass the respective beams of the dual optical frequency comb light sources through the third semi-transmissive and semi-reflective mirror, so that the respective beams of the dual optical frequency comb light sources have orthogonal polarization states, and a first beam with orthogonal polarization states is obtained.

[0044] Step S20: Dynamically adjust the wavelength of the first beam through a planar frequency sweeping module to obtain a second beam. In another feasible implementation manner, step S20 may include: The frequency-swept beam obtained by dynamically adjusting the wavelength of the first beam through the planar frequency sweeping module passes through a spatial light modulation module for optical wave modulation and a beam shaping module for adjusting the light intensity distribution in sequence to form an ideal output beam, and the ideal output beam is used as the second beam.

[0045] Step S30: Perform a planar array detection on the sample to be measured based on the second beam to obtain a dual optical frequency comb multi-heterodyne interference signal. In another feasible implementation manner, step S30 may include: Polarization beam split the second beam into a reference beam and a sample beam. Among them, the sample beam is simultaneously focused onto the retroreflection after the sample to be measured through a microlens array and combined with the reference beam to form a combined beam, and the combined beam is detected by a photodetector to obtain a dual optical frequency comb multi-heterodyne interference signal.

[0046] Step S40: Detect the surface topography of the sample to be measured based on the dual optical frequency comb multi-heterodyne interference signal.

[0047] In another feasible implementation manner, step S40 may include: Determine the ranging distance of the sample to be measured based on the dual optical frequency comb multi-heterodyne interference signal. The ranging distance is the distance between the surface of the sample to be measured and a preset standard plane. Take the distance between the surface of the sample to be measured and the preset standard plane as the one-dimensional depth information of the sample to be measured, and detect the surface topography of the sample to be measured based on the one-dimensional depth information. Among them, the preset standard plane may be the upper surface or the lower surface of the microlens array or the projection objective. For example, in the extreme case, the optical path of the sample beam can be directly used as the ranging distance.

[0048] Regarding the 3D reconstruction algorithm, it combines signal processing and image generation techniques to integrate one-dimensional depth information (A-scan) and two-dimensional transverse scanning (B-scan) into 3D volume data, achieving the conversion from the original signal to high-precision 3D volume data. In the data preprocessing stage, the one-dimensional depth signal obtained by A-scan often contains noise, and time-frequency domain filtering techniques such as wavelet transform or fast Fourier transform (FFT) are used for noise reduction to ensure the purity of the signal. For the B-scan image sequence, multi-frame alignment is achieved through feature matching or maximizing mutual information to eliminate artifacts caused by object movement. At the same time, the iterative closest point (ICP) algorithm is used to complete the precise registration of multi-view images, and these data are unified into the global coordinate system. In the multi-modal data fusion and interpolation stage, the TSDF (truncated signed distance function) algorithm is used to fuse the 3D point cloud generated from the A-scan depth information and the spatial distribution constraints provided by B-scan to construct a continuous surface model, effectively filling potential data holes and enhancing 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 fine 3D model is generated, integrating the scattered information into 3D volume data with high detail and accuracy.

[0049] Specifically in this embodiment, the one-dimensional depth information of A-scan is replaced by the ranging distance of each point on the surface array of the sample to be measured obtained by dual-comb swept-frequency ranging.

[0050] Among them, the calculation formula for the depth information of A-scan is:

[0051] In the above formula, h represents the one-dimensional depth of A-scan, c represents the speed of light in vacuum, n g represents the group refractive index of air (the group refractive index of air is a parameter that describes the degree of slowdown of the group velocity of light waves relative to the speed of light in vacuum during propagation in air), Δt represents the peak interval of the frequency-doubled signal after being amplified and curve-fitted by asynchronous optical sampling, and Δf represents the fixed repetition frequency difference between the signal optical comb and the local oscillator optical comb. This frequency difference Δf is the frequency difference between the dual-comb multi-heterodyne interference signals. Referring to the introduction of the aforementioned dual-comb light source, the first optical comb light source A1 (repetition frequency frep), the second optical comb light source A2 (frep + Δf).

[0052] There is a temporal superposition between the two optical frequency comb light sources, that is, different frequencies correspond to different times. For example, the first optical frequency comb light source A1 is a swept frequency from 380 nm to 780 nm in the visible light wavelength range, and the beam of the first optical frequency comb light source A1 is detected by the first ultra-high-speed area array detector; the second optical frequency comb light source A2 is a swept frequency from 381 nm to 781 nm, and the beam of the second optical frequency comb light source A2 is detected by the second ultra-high-speed area array detector; at a certain moment when the first optical frequency comb light source A1 is 380 nm, there is no light source signal from the second optical frequency comb light source A2. At another moment when the first optical frequency comb light source A1 is 381 nm, there is the same 381 nm light source signal from the second optical frequency comb light source A2. At yet another moment when the second optical frequency comb light source A2 is 781 nm, there is no light source signal from the first optical frequency comb light source A1. Thus, in a waveform diagram with the abscissa being the frequency and the ordinate being the light intensity value, i.e., the amplitude, one detection by the area array detector can only obtain one point in the waveform diagram, that is, the amplitude corresponding to a certain frequency. Therefore, through frequency sweeping, the responses of the first optical frequency comb light source A1 in the range of 380 nm - 780 nm and the second optical frequency comb light source A2 in the range of 381 nm - 781 nm, that is, all the points are respectively formed into response curves and frequency-sweeping curves. By the difference between the respective response curves of the two optical frequency comb light sources in the waveform diagram, namely Δf and Δt, the ranging distance of each point on the area array of the sample to be measured can be calculated.

[0053] In an application scenario, an atomic-level topography detection system based on dual-comb interference and area-domain frequency-sweeping technology is provided. The dual-comb light source consists of two ytterbium-doped fiber frequency combs with a repetition frequency difference Δf = 5.4 kHz (the repetition frequency fr of light source A is 201.2 MHz, and that of light source B is fr + Δf). An orthogonally polarized pulse sequence is output through polarization beam combining. The carrier-envelope phase (CEP) is stabilized to an accuracy of 10 kHz (traceable to an atomic clock) using VCSEL technology to ensure that the frep and fCEO of the frequency comb are strictly synchronized with the atomic clock through closed-loop control respectively; the area-domain frequency-sweeping module T uses an acousto-optic tunable filter (AOTF) to dynamically adjust the diffraction light wavelength at a rate of 1 MHz to achieve continuous frequency sweeping; the interference measurement module divides the light source into a reference light and a sample light through polarization beam splitting, generates a multi-heterodyne signal in the interferometer, and is captured by an array of photodetectors; the signal processing module X eliminates artifacts in the low signal-to-noise region based on the ID-OCTA algorithm and combines a convolutional neural network to optimize the deconvolution algorithm, and finally generates an atomic-level three-dimensional topography map, achieving a detection accuracy of <1 μm in the lateral resolution and <10 nm in the axial resolution.

[0054] In another application scenario, an extended detection system based on dual-comb interferometry and area-scanning frequency-sweeping technology is provided. By extending the central wavelength of the dual-comb light source to 1550 nm (bandwidth > 150 nm, power stability < 0.05 dB), and using an electro-optic modulator (EOM) to achieve dynamic frequency sweeping at a rate of 2 MHz, while combining a PID control algorithm to compensate for the frequency drift caused by the ambient temperature (accuracy ±0.1%), its core modules include: The dual-comb light source locks the repetition frequency to the second harmonic of the atomic clock (402.4 MHz) through VCSEL technology, and the carrier-envelope phase (fCEO) is fixed at zero to improve stability; The area-scanning frequency-sweeping module T uses an EOM to replace the AOTF, and cooperates with a high-speed InP detector array (response time < 10 ns) to capture multi-heterodyne signals; The signal processing module X uses a multi-wavelength fusion algorithm combined with a Transformer network to fuse the dual-wavelength data of 1050 nm and 1550 nm to eliminate the influence of material dispersion, and optimizes the global feature matching of three-dimensional reconstruction through the Transformer network, and finally generates an atomic-level three-dimensional topography map with a lateral resolution < 0.5 μm and an axial resolution < 5 nm.

[0055] In yet another application scenario, a portable atomic-level topography detection system based on a simplified dual-comb light source and a miniaturized frequency-sweeping module is provided. A monolithic integrated fiber optic comb (central wavelength 1050 nm, bandwidth 50 nm, power stability < 0.2 dB) is adopted, and the repetition frequency (frep) and the carrier-envelope phase (fCEO) are directly locked by a commercial rubidium atomic clock, and the VCSEL modulator is omitted to reduce complexity; The area-scanning frequency-sweeping module T uses a MEMS modulator to replace the AOTF, and achieves frequency sweeping at a rate of 0.5 MHz, with a driving voltage < 5 V, a power consumption < 1 W, and the volume reduced to 1 / 10 of the traditional scheme; The interference measurement module captures multi-heterodyne signals through a folded interferometer (volume reduced by 40%); The signal processing module X realizes real-time deconvolution based on a lightweight CNN (such as MobileNet) algorithm and an embedded GPU chip, with a calculation delay < 0.1 second, and supports on-site defect marking; Finally, a three-dimensional topography map with an axial resolution < 20 nm is generated. The overall volume of the system is only 20×20×10 cm³, the weight < 5 kg, the single-scan time ≤ 2 seconds, and the cost is reduced by 40% compared with the traditional scheme, which is suitable for on-site rapid detection scenarios such as real-time defect screening in semiconductor wafer production lines.

[0056] It should be noted that the above examples are only for understanding this application and do not constitute a limitation to the surface topography detection method based on dual-comb area-scanning frequency-sweeping of this application. Any simple transformation in more forms based on this technical concept is within the protection scope of this application.

[0057] The present application provides a surface topography detection system based on dual-comb surface frequency sweeping. The surface topography detection system based on dual-comb surface frequency sweeping 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 to enable the at least one processor to execute the method for surface topography detection based on dual-comb surface frequency sweeping in the first embodiment above.

[0058] The surface topography detection system based on dual-comb surface frequency sweeping may include a processing device 1001 (such as a central processing unit, a graphics processing unit, etc.), which can perform various appropriate actions and processes according to a program stored in a read-only memory 1002 or a program loaded from a storage device 1003 into a random access memory 1004. In the random access memory 1004, various programs and data required for the operation of the surface topography detection system based on dual-comb surface frequency sweeping are also stored. The processing device 1001, the read-only memory 1002, and the random access memory 1004 are connected to each other through a bus 1005. An input / output interface 1006 is also connected to the bus. Generally, the following systems may be connected to the input / output interface 1006: an input device 1007 including, for example, a touch screen, a touchpad, a keyboard, a mouse, an image sensor, a microphone, an accelerometer, a gyroscope, etc.; an output device 1008 including, for example, a liquid crystal display (LCD: Liquid Crystal Display), a speaker, a vibrator, etc.; a storage device 1003 including, for example, a magnetic tape, a hard disk, etc.; and a communication device 1009. The communication device 1009 may allow the surface topography detection system based on dual-comb surface frequency sweeping to communicate with other devices wirelessly or wiredly to exchange data. Although the figure shows a surface topography detection system based on dual-comb surface frequency sweeping having various systems, it should be understood that it is not required to implement or have all the shown systems. More or fewer systems may be alternatively implemented or had.

[0059] Specifically, according to the embodiments disclosed in the present application, the process described above with reference to the flowchart can be implemented as a computer software program. For example, the embodiments disclosed in the present application include a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program contains program codes for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from the network through the communication device, or installed from the storage device 1003, or installed from the 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 embodiments disclosed in the present application are executed.

[0060] The surface topography detection system based on dual optical frequency comb area scanning provided by this application adopts the surface topography detection method based on dual optical frequency comb area scanning in the above-mentioned embodiment, and can solve the technical problem of insufficient detection resolution of swept source optical coherence tomography (SS-OCT). Compared with the prior art, the beneficial effects of the surface topography detection system based on dual optical frequency comb area scanning provided by this application are the same as those of the surface topography detection method based on dual optical frequency comb area scanning provided by the above-mentioned embodiment, and other technical features in the surface topography detection system based on dual optical frequency comb area scanning are the same as those disclosed in the method of the previous embodiment, and will not be elaborated here.

[0061] It should be understood that each part disclosed in this application can be implemented by hardware, software, firmware or a combination thereof. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in a suitable manner in any one or more embodiments or examples.

[0062] As mentioned above, the above are only specific embodiments of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application can easily think of changes or substitutions, which should be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

[0063] This application provides a computer-readable storage medium with computer-readable program instructions (i.e., computer programs) stored thereon, and the computer-readable program instructions are used to execute the surface topography detection method based on dual optical frequency comb area scanning in the above-mentioned embodiment.

[0064] The computer-readable storage medium provided by this application can 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 of the above. More specific examples of computer-readable storage media may include, but are not limited to: electrical connections with one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM) or flash memory, optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the above. In this embodiment, the computer-readable storage medium can be any tangible medium that contains or stores a program, and this program can be used by or in combination with an instruction execution system or device. The program code contained on the computer-readable storage medium can be transmitted by any suitable medium, including but not limited to: wires, optical cables, RF (Radio Frequency), etc., or any suitable combination of the above.

[0065] The above computer-readable storage medium can be included in a surface topography detection system based on dual optical frequency comb surface scanning; it can also exist independently and not be assembled into a surface topography detection system based on dual optical frequency comb surface scanning.

[0066] The above computer-readable storage medium carries one or more programs. When the above one or more programs are executed by a surface topography detection system based on dual optical frequency comb surface scanning, the surface topography detection system based on dual optical frequency comb surface scanning is enabled to: obtain a first beam by coupling the respective beams of the dual optical frequency comb light sources; obtain a second beam by dynamically adjusting the wavelength of the first beam through a surface scanning module; perform a matrix detection on the sample to be measured based on the second beam to obtain a dual optical frequency comb multi-heterodyne interference signal; and detect the surface topography of the sample to be measured based on the dual optical frequency comb multi-heterodyne interference signal.

[0067] Computer program code for performing the operations of this application can be written in one or more programming languages or combinations thereof. The above-mentioned programming languages include object-oriented programming languages such as Java, Smalltalk, C++, and also include conventional procedural programming languages such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, executed 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 can be connected to the user's computer through any kind of network, including a local area network (LAN: Local Area Network) or a wide area network (WAN: Wide Area Network), or it can be connected to an external computer (for example, by using an Internet service provider to connect through the Internet).

[0068] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code that contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than marked in the accompanying drawings. For example, two consecutively represented blocks may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and combinations of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or operations, or can be implemented by a combination of dedicated hardware and computer instructions.

[0069] The modules involved in the embodiments described in this application can be implemented in software or in hardware. Among them, the name of the module does not constitute a limitation on the unit itself in some cases.

[0070] The readable storage medium provided in this application is a computer-readable storage medium. The computer-readable storage medium stores computer-readable program instructions (i.e., computer programs) for performing the above-mentioned surface topography detection method based on dual optical frequency comb surface frequency sweeping, which can solve the technical problem of insufficient detection resolution of swept-source optical coherence tomography (SS-OCT). Compared with the prior art, the beneficial effects of the computer-readable storage medium provided in this application are the same as those of the surface topography detection method based on dual optical frequency comb surface frequency sweeping provided in the above embodiments, and will not be elaborated here.

[0071] The present application also provides a computer program product, including a computer program which, when executed by a processor, implements the steps of the surface topography detection method based on dual optical frequency comb surface domain frequency sweeping as described above.

[0072] The computer program product provided by the present application can solve the technical problem of insufficient detection resolution of swept source optical coherence tomography (SS-OCT). Compared with the prior art, the beneficial effects of the computer program product provided by the present application are the same as those of the surface topography detection method based on dual optical frequency comb surface domain frequency sweeping provided in the above embodiments, and will not be elaborated here.

[0073] The above are only partial embodiments of the present application, and thus do not limit the patent scope of the present application. Any equivalent structural transformation made under the technical concept of the present application by using the content of the specification and drawings of the present application, or any direct / indirect application in other related technical fields, is included in the patent protection scope of the present application.

Claims

1. A surface topography detection method based on dual optical frequency comb surface frequency sweeping, characterized in that The surface topography detection method based on dual-comb spectral domain sweeping includes the following steps: Couple the beams of the dual-comb light sources respectively to obtain a first beam; Dynamically adjust the wavelength of the first beam through a spectral domain sweeping module to obtain a second beam, where dynamically adjusting the wavelength of the first beam is spectral sweeping; Polarization beam split the second beam into a reference beam and a sample beam. The sample beam is simultaneously focused by a microlens array onto the reflected light after the sample to be measured, and then combined with the reference beam to form a combined beam. Detect the combined beam through a photodetector to obtain a dual-comb multi-heterodyne interference signal, and the dual-comb multi-heterodyne interference signal is the interference signal corresponding to each of the dual combs; Detect the surface topography of the sample to be measured based on the dual-comb multi-heterodyne interference signal.

2. The surface topography detection method based on dual optical frequency comb surface domain frequency sweeping according to claim 1, characterized in that, The step of detecting the surface topography of the sample to be measured based on the dual-comb multi-heterodyne interference signal includes: Determine the 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 the one-dimensional depth information of the sample to be measured, and detect the surface topography of the sample to be measured based on the one-dimensional depth information.

3. The surface topography detection method based on dual optical frequency comb surface domain frequency sweeping according to claim 1, wherein The step of dynamically adjusting the wavelength of the first beam through a spectral domain sweeping module to obtain a second beam includes: The swept-frequency beam obtained by dynamically adjusting the wavelength of the first beam through a spectral domain sweeping module passes through a spatial light modulation module for optical wave modulation and a beam shaping module for adjusting the light intensity distribution in sequence to form an ideal output beam, and use the ideal output beam as the second beam.

4. The surface topography detection method based on dual optical frequency comb surface scanning as described in claim 1, wherein, The step of coupling the beams of the dual-comb light sources respectively to obtain a first beam includes: Use a third semi-transparent semi-reflective mirror as a polarization beam combiner, and pass the beams of the dual-comb light sources through the third semi-transparent semi-reflective mirror, so that the beams of the dual-comb light sources have orthogonal polarization states to obtain a first beam with orthogonal polarization states.

5. A surface topography detection system based on dual optical frequency comb surface scanning, characterized in that, The surface topography detection system based on dual-comb spectral domain sweeping includes: dual-comb light sources, a spectral domain sweeping module, an interference measurement module, and a signal processing module; The spectral domain sweeping module is used to dynamically adjust the wavelength of the first beam obtained by coupling the beams of the dual-comb light sources respectively to obtain a second beam, where dynamically adjusting the wavelength of the first beam is spectral sweeping; The interference measurement module is used to polarization beam split the second beam into a reference beam and a sample beam. The sample beam is simultaneously focused by a microlens array onto the reflected light after the sample to be measured, and then combined with the reference beam to form a combined beam. Detect the combined beam through a photodetector to obtain a dual-comb multi-heterodyne interference signal, and the dual-comb multi-heterodyne interference signal is the interference signal corresponding to each of the dual combs; The signal processing module is used to detect the surface topography of the sample to be measured based on the dual-comb multi-heterodyne interference signal.

6. The surface topography detection system based on dual optical frequency comb surface frequency sweeping according to claim 5, characterized in that The interference measurement module includes: a first semi-transparent semi-reflective mirror, a reference mirror, a second reflector, a microlens array, a projection objective, a second semi-transparent semi-reflective mirror, and a photodetector; where the photodetector includes a first ultra-high-speed area array detector and a second ultra-high-speed area array detector; The first semi-transmissive and semi-reflective mirror is configured to polarize and split the second light beam into a reference light beam and a sample light 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, the first semi-transmissive and semi-reflective mirror; The second optical path of the reference light beam is: the reference mirror, the first semi-transmissive and semi-reflective mirror; The first semi-transmissive and semi-reflective mirror is further configured to combine the sample light beam that has passed through the first optical path and the reference light beam that has passed through the second optical path to form a combined light beam; The second semi-transmissive and semi-reflective mirror is configured to split the combined light beam into the first ultra-high-speed area array detector and the second ultra-high-speed area array detector respectively to obtain a dual-comb multi-heterodyne interference signal.

7. The surface topography detection system based on dual optical frequency comb surface domain frequency sweeping according to claim 5, characterized in that, The surface topography detection system based on dual-comb area scanning frequency sweeping further includes: a spatial light modulation module and a beam shaping module; wherein, the frequency-sweeping light beam obtained by dynamically adjusting the wavelength of the first light beam through the area scanning frequency sweeping module sequentially passes through the spatial light modulation module for optical 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.

8. The surface topography detection system based on dual optical frequency comb surface domain frequency sweeping according to claim 5, wherein The surface topography detection system based on dual-comb area scanning frequency sweeping further includes: a third semi-transmissive and semi-reflective mirror; using the third semi-transmissive and semi-reflective mirror as a polarization combiner, and passing the light beams of the dual-comb light sources through the third semi-transmissive and semi-reflective mirror respectively, so that the light beams of the dual-comb light sources have orthogonal polarization states to obtain a first light beam with orthogonal polarization states.

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