Light field distinguishing method and system

Abstract

The invention provides a light field resolution method and system, and relates to the technical field of ultrafast light field imaging. The light field resolution method comprises the following steps: carrying out delay processing on a reference light beam to obtain a delayed reference light beam; delaying the probe light beam to obtain a delayed probe light beam; enabling the delayed probe light beam to pass through an ultrafast event scene to obtain a modulated probe light beam; performing interference on the modulation probe light beam and the delay reference light beam to obtain an image formed by interference; and based on the image formed by interference, obtaining three-dimensional space distribution at different times in the ultrafast event scene. And under the condition that the three-dimensional space distribution is obtained, analyzing the physical characteristics of the ultrafast event scene. Through three-dimensional space distribution, the morphology and characteristics of an ultrafast event scene are analyzed from multiple dimensions of time, space and the like, and a specific relation between a laser parameter and a laser propulsion coupling coefficient can be established.

Description

Technical Field

[0001] The present application relates to the field of ultrafast light field imaging technology, and in particular to a light field resolution method and system. Background Art

[0002] In recent years, a variety of single-shot ultrafast light field imaging technologies have emerged, such as time-sequential plenoptical photography (STAMP) and single-shot time-frequency multiplexing holography (SS-TSFM).

[0003] Due to spatial scale limitations, these methods are often only suitable for continuous-time observations on the picosecond or even femtosecond scale. The duration of the plasma generated by the interaction between laser and matter often ranges from hundreds of nanoseconds to microseconds, requiring a very large spatial scale to achieve such long-term time resolution, which is unrealistic for the design of the overall experimental optical path.

[0004] At the same time, for ultrafast processes on irregular surfaces, two-dimensional planar observations cannot reflect their true physical conditions, requiring the collection and acquisition of more information from a three-dimensional perspective. In particular, for non-repeatable ultrafast processes on the nanometer scale, such as the generation and expansion of stimulated plasma plumes on irregular surfaces, a single four-dimensional spatiotemporal resolution method with high spatial resolution and a long time window is required. This method can be used to analyze the spatiotemporal characteristics of ultrafast event scenarios, providing precise four-dimensional data support for laser parameter optimization and impulse coupling coefficient correlation analysis, significantly improving the efficiency of laser ablation propulsion. Summary of the Invention

[0005] In view of this, the purpose of the embodiments of the present application is to provide a light field resolution method and device to establish a specific connection between laser parameters and coupling coefficients, and to analyze the morphology and characteristics of ultrafast event scenes from multiple dimensions such as time and space.

[0006] In a first aspect, the light field resolution method includes: delaying a reference beam to obtain a delayed reference beam; delaying a probe beam to obtain a delayed probe beam; passing the delayed probe beam through an ultrafast event scene to obtain a modulated probe beam; interfering the modulated probe beam with the delayed reference beam to obtain an interference-formed image; obtaining a three-dimensional spatial distribution of the ultrafast event scene based on the interference-formed image; and analyzing the physical characteristics of the ultrafast event scene after obtaining the three-dimensional spatial distribution.

[0007] In the above implementation, the reference beam and probe beam are each delayed, introducing a controllable and adjustable time delay to control the timing of the optical signal. This provides important temporal reference and support for the experiment, enabling the acquisition of information at different times during the ultrafast event. The probe beam is primarily used to detect physical quantities or material properties. The reference beam serves as a comparison or benchmark, compensating for the effects of environmental factors (such as intensity fluctuations and phase changes) on the measurement results. By analyzing the changes in the propagation characteristics (such as intensity, phase, and polarization) of the probe beam in the ultrafast event, the morphology and characteristics of the ultrafast event can be determined, potentially including dynamic characteristics such as electron density, temperature, and electromagnetic fields. In interferometry, the reference and probe beams propagate along separate optical paths before interfering with each other. By comparing information such as the interference fringes, parameters such as the optical path difference can be accurately measured, thereby obtaining information such as displacement and refractive index changes of the object being measured. The image formed by the interference reveals the three-dimensional spatial distribution of the ultrafast event, establishing a specific relationship between the laser parameters and the coupling coefficient, allowing the morphology and characteristics of the ultrafast event to be analyzed from multiple perspectives, including time and space.

[0008] In one embodiment of the present application, the delay processing of the reference beam to obtain the delayed reference beam includes: dividing the reference beam into multiple beams with different time delay scales to obtain the delayed reference beam, and outputting the multiple delayed reference beams in parallel to different optical paths.

[0009] During this implementation, many physical processes are transient, such as molecular vibrations, electron relaxation, chemical reactions, and carrier dynamics, occurring within extremely short timescales (femtoseconds to nanoseconds). To study these ultrafast events, it is necessary to observe the changes in the probe beam at different time points. By controlling the path lengths of different reference beam branches and introducing different time delays τ, these beams can be compared with the probe beam to observe the physical characteristics of these ultrafast events.

[0010] In one embodiment of the present application, the delay processing of the probe beam to obtain the delayed probe beam includes: dividing the probe beam into multiple beams with different time delay scales, combining the beams to obtain the delayed probe beam, and outputting them to the same optical path.

[0011] In this implementation, the probe beam is split into multiple beams with different time delay scales. This initial probe beam is then routed through optical paths of varying lengths, introducing different time delays in each branch. The resulting beams, each with a fixed, known, and varying time delay, are then recombined into the same spatial propagation direction. While the probe beam now appears to be a single beam in space, it internally contains multiple beams with different time delays, τ.

[0012] In one embodiment of the present application, the step of passing the probe beam through an ultrafast event scene to obtain a modulated probe beam comprises: performing a beam expansion process on the delayed probe beam to obtain an expanded probe beam; and performing a beam contraction process on the expanded probe beam when the expanded probe beam passes through the ultrafast event scene to obtain the modulated probe beam; wherein the ultrafast event scene comprises a plasma plume.

[0013] In the above implementation process, in order to make the delayed probe beam uniformly cover the entire target scene that needs to be imaged or detected, it needs to be expanded. The delayed probe beam after expansion (i.e., the expanded probe beam) does not change its delay information. When the expanded probe beam is irradiated to different positions of the target ultrafast event scene, the expanded probe beam will interact with the local characteristics of the sample, corresponding to different time delays at different spatial positions, and carrying different spatiotemporal information. For example, different absorption / scattering intensities in different regions will change the probe light amplitude, or different refractive indices / thicknesses in different regions can change the probe light phase. The probe light signal reflected or transmitted from the target scene is divergent, and the scattered light over a large area is re-converged into a small-sized beam for efficient coupling to the subsequent interference optical path or detector.

[0014] In one embodiment of the present application, interfering the modulated probe beam with the delayed reference beam to obtain an interference-formed image includes: superimposing the modulated probe beam with multiple delayed reference beams respectively; the delayed reference beam with corresponding time delay interferes with the modulated probe beam, and the remaining beams serve as background information.

[0015] In this implementation, the modulated probe beam is modulated by the target scene (carrying amplitude and phase variations). Each of the multiple delayed reference beams has a fixed and distinct time delay, matching the delay scale of the probe beam to a certain extent. When the delay of a reference beam matches the delay of the modulated probe beam at a certain position, constructive and destructive interference occurs. However, components of the reference and probe beams with mismatched delays coherently add (representing only background noise).

[0016] In one embodiment of the present application, the light field resolution method further includes: incident an initial light beam along a certain angle, and dividing the initial light beam into the reference light beam and the probe light beam.

[0017] In this implementation, the initial optical beam is split into a reference beam and a probe beam for subsequent optical signal processing. The reference beam serves as an optical path reference, unaffected by the ultrafast event, preserving its phase and amplitude information. The probe beam interacts with the ultrafast event (e.g., through reflection, scattering, or transmission). Subsequent interference between the two beams allows the phase and optical path changes caused by the ultrafast event to be extracted and measured.

[0018] In one embodiment of the present application, the image formed based on interference is used to obtain the three-dimensional spatial distribution of the ultrafast event scene, including: acquiring the image generated by the initial light beam incident at different angles; restoring the two-dimensional spatiotemporal distribution of the ultrafast event scene from the image; and reconstructing the three-dimensional spatial distribution of the ultrafast event scene through the two-dimensional spatiotemporal distribution. In this implementation, the process is repeated, with multiple initial beams incident simultaneously at different angles. Similarly, these beams are divided into reference and probe beams. Each probe beam records a 2D image of the ultrafast event at a different angle. By processing these multi-angle 2D ultrafast event images, the 3D spatial distribution of the ultrafast event scene is reconstructed.

[0019] In a second aspect, an embodiment of the present application further provides a light field resolution system, comprising: a delay control device, an ultrafast event generating device, a first beam splitting element, and a detection and analysis device; the delay control device is used to respectively delay the reference beam and the probe beam to obtain a delayed reference beam and a delayed probe beam; the ultrafast event generating device is used to establish an ultrafast event scene, and when the delayed probe beam passes through the ultrafast event scene, a modulated probe beam is obtained; the first beam splitting element is used to change the direction of the modulated probe beam, wherein, after adjusting the direction of the modulated probe beam, the modulated probe beam can interfere with the delayed reference beam; the detection and analysis device is used to record the image formed by the interference, and based on the image formed by the interference, obtain the three-dimensional spatial distribution of the ultrafast event scene.

[0020] In the above implementation process, the ultrafast event generation device is used to establish an ultrafast event scenario, while the delay control device is used to delay the reference beam and the probe beam, respectively, to obtain a delayed reference beam and a delayed probe beam. When the delayed probe beam undergoes beam expansion and passes through the ultrafast event scenario established by the ultrafast event generation device, it can carry the spatiotemporal information of the ultrafast event scenario. When the delayed probe beam passes through the ultrafast event scenario, a modulated probe beam is obtained. The modulated probe beam can interfere with the delayed reference beam. In the detection and analysis device, the recorded information is displayed, and the three-dimensional spatial distribution of the ultrafast event scenario is reconstructed based on this information.

[0021] In one embodiment of the present application, the light field resolution system further includes: a light source generating device and a second beam splitting element; the light source generating device is used to generate an initial light beam, and is incident on the second beam splitting element along a certain angle; the second beam splitting element splits the initial light beam into the reference beam and the probe beam.

[0022] In this implementation, a light source generator generates an initial beam, which is then split by a second beam splitter into a reference beam and a probe beam for subsequent optical signal processing. The reference beam serves as an optical path reference, unaffected by the ultrafast event, retaining its phase and amplitude information. The probe beam, on the other hand, interacts with the ultrafast event. For example, subsequent interference between the two beams can be used to extract the phase / optical path changes caused by the ultrafast event, enabling measurement.

[0023] In one embodiment of the present application, the light field resolution system further includes: a first imaging device and a second imaging device; the first imaging device is used to present the modulated probe beam to the detection and analysis device; the second imaging device is used to present the multiple delayed reference beams to the detection and analysis device respectively.

[0024] In the above implementation, the first imaging device and the second imaging device clearly present the modulated probe beam and the delayed reference beam, respectively, to the detection and analysis device. Ideal imaging can only be achieved under specific object and image distance conditions. If the object or image distance deviates from these relationships, the imaging effect will be affected, resulting in a blurred or unclear image. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 A first flow chart of the light field resolution method provided in an embodiment of the present application; Figure 2 A second flow chart of the light field resolution method provided in an embodiment of the present application; Figure 3 A third flow chart of the light field resolution method provided in an embodiment of the present application; Figure 4 A fourth flow chart of the light field resolution method provided in an embodiment of the present application; Figure 5 A first schematic diagram of a light field resolution system provided in an embodiment of the present application; Figure 6 A second schematic diagram of the light field resolution system provided in an embodiment of the present application; Figure 7 This is a third schematic diagram of the light field resolution system provided in an embodiment of the present application.

[0027] Icons: 01-first lens; 02-second lens; 03-third lens; 10-delay control device; 11-first delay controller; 12-second delay controller; 20-ultrafast event generating device; 21-beam expander; 22-beam shrinker; 31-first beam splitting element; 32-second beam splitting element; 40-detection and analysis device; 50-light source generating device; 61-first imaging device; 62-second imaging device. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of them. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the embodiments of the present application.

[0029] To facilitate understanding of this plan, the following terms are explained first: Ultrafast event: refers to the situation where the electronic system of a substance is instantly excited by an ultrashort laser pulse / beam, while the heavy ions (or lattice) have not yet responded, resulting in the system being in a non-equilibrium state with electron-ion temperature separation.

[0030] Ultrafast event scenarios: specifically refers to transient physical processes occurring on the femtosecond (fs) to nanosecond (ns) time scale. These processes exhibit unique non-equilibrium behaviors due to their extremely short time (even shorter than the molecular / atomic motion period).

[0031] On this basis, in order to establish a specific connection between laser parameters and coupling coefficients, a four-dimensional spatiotemporal resolution technology for single ultrafast events is urgently needed to analyze the morphology and characteristics of ultrafast event scenes from multiple perspectives, such as time and space. In view of this, the embodiments of the present application provide a light field resolution method and device.

[0032] First, see Figure 1 , Figure 1 This is a first flow chart of a light field resolution method provided in an embodiment of the present application. This embodiment of the present application provides a light field resolution method including: S100: Delaying the reference beam to obtain a delayed reference beam; S200: delaying the probe beam to obtain a delayed probe beam; S300: passing the delayed probe beam through an ultrafast event scene to obtain a modulated probe beam; S400: interfering the modulated probe beam with the delayed reference beam to obtain an interference image; S500: Based on the image formed by interference, the three-dimensional spatial distribution of the ultrafast event scene is obtained; S600: After obtaining the three-dimensional spatial distribution, analyzing physical characteristics of the ultrafast event scene.

[0033] In the above implementation, the reference beam serves as a comparison or benchmark, compensating for the effects of environmental factors (such as light intensity fluctuations and phase changes) on the measurement results. The probe beam is used to detect physical quantities or material properties. By analyzing the changes in the probe beam's propagation characteristics (such as light intensity, phase, and polarization) within the ultrafast event scene, the morphology and characteristics of the ultrafast event scene can be determined, potentially including dynamic characteristics such as electron density, temperature, and electromagnetic fields. The delayed probe beam passes through the ultrafast event scene. That is, when the delayed probe beam passes through the ultrafast event scene, the ultrafast event alters the absorptivity, refractive index, or phase distribution of the sample within the scene. The resulting modulated probe beam carries information about the spatial and temporal evolution of the ultrafast event. The modulated probe beam and the delayed reference beam are interfering to obtain an interference image. Analyzing the interference image reveals the three-dimensional spatial distribution of the ultrafast event scene. Once this three-dimensional spatial distribution is established, the morphology and characteristics of the ultrafast event scene can be analyzed from multiple perspectives, including temporal and spatial, establishing a specific relationship between laser parameters and coupling coefficients.

[0034] Specifically, assuming that the incident probe beam is a plane wave, its light field can be expressed as:

[0035] In one embodiment of the present application, plasma plume is used as the ultrafast event scenario. Due to the free electron density in the plasma This changes the refractive index of the medium, causing a phase delay in the delayed probe beam as it propagates through the plasma plume. .

[0036] In addition, the high-density plasma absorbs the laser energy through inverse bremsstrahlung, accompanied by partial scattering, which causes the intensity of the incident delayed probe beam to attenuate. The delayed probe beam is also modulated in intensity, which can be expressed as .

[0037] Therefore, after the probe beam interacts with the plasma, its complex amplitude distribution can be written as:

[0038] It can be considered that after the probe beam passes through the plasma plume, the change in its complex amplitude records the two-dimensional spatiotemporal distribution of the planar plasma plume.

[0039] In one embodiment of the present application, a reference beam is delayed to obtain a delayed reference beam, including: dividing the reference beam into multiple beams with different time delay scales to obtain a delayed reference beam, and outputting the multiple delayed reference beams in parallel to different optical paths.

[0040] In the above implementation process, the delay of the light beam needs to be changed according to the time scale of the ultrafast event scene being detected. The length of the optical fiber L used can be changed by the formula Calculate, where is the speed of light, is the time delay to be achieved, is the refractive index of the laser of this wavelength when propagating in the corresponding optical fiber.

[0041] Optionally, time delays of 10ns, 20ns, 30ns and other intervals can be achieved during the experiment; on this basis, for example, when studying the two-dimensional distribution of nanosecond laser-induced excitation aluminum plasma, a quartz optical fiber is used to achieve time delays of 10ns, 20ns, 30ns and other intervals for the 527nm probe laser, and its refractive index is , the required optical fiber length is approximately 2m, 4m, 6m, and so on.

[0042] In one embodiment of the present application, the probe beam is delayed to obtain a delayed probe beam, including: dividing the probe beam into multiple beams with different time delay scales, combining the beams to obtain a delayed probe beam, and outputting them to the same optical path.

[0043] In the above implementation process, the time evolution process is mapped to the spatial dimension by carrying different time delays through spatially separated optical paths. Splitting a single probe light into multiple beams of light with different delays is equivalent to creating multiple time observation points on the time axis. Specifically, if the light is split into N paths and the delay interval is Δt, the time range that can be covered by a single experiment is ‌(N-1)Δt‌, and it is possible to react with ultrafast event scenarios at each time observation point. Multiple light beams with different time delay scales are combined. After combining, not only can a single detector receive signals from all time channels, but it also carries all the spatiotemporal information of all ultrafast event scenarios.

[0044] In one embodiment of the present application, see Figure 2 , Figure 2 The second flow chart of the light field resolution method provided in the embodiment of the present application is as follows: The probe beam is passed through an ultrafast event scene to obtain a modulated probe beam, including: S310: performing beam expansion processing on the delayed probe beam to obtain an expanded probe beam; S320: When the expanded probe beam passes through an ultrafast event scene, performing a beam contraction process on the expanded probe beam to obtain a modulated probe beam; wherein the ultrafast event scene includes a plasma plume.

[0045] In the above implementation process, beam expansion is to adjust the size of the delayed probe beam so that the delayed probe beam can better match the size of the plasma plume or the requirements of other subsequent optical elements. After the probe beam is expanded, its beam diameter increases, which can improve the uniformity of the beam and reduce the beam edge effect to a certain extent, making the interaction area of the beam in the plasma plume more regular. For example, if the cross-section of the plasma plume is large, the expanded probe beam can more fully cover the plume area, thereby more effectively detecting the characteristics of the plasma. The delayed probe beam reflected or transmitted by the target ultrafast event scene is divergent, and the large-area scattered probe beam is re-converged into a small-size modulated probe beam for efficient coupling to the subsequent interference optical path or detector.

[0046] In one embodiment of the present application, see Figure 3 , Figure 3 The third flow chart of the light field resolution method provided in the embodiment of the present application. Interfering the modulated probe beam with the delayed reference beam to obtain an interference image includes: S410: Superimposing the modulated probe beam and the multiple delayed reference beams respectively; S420: The delayed reference beam corresponding to the time delay interferes with the modulated probe beam, and the remaining beams serve as background information.

[0047] In the above implementation process, the reference beam and probe beam propagate along different optical paths, obtaining a modulated probe beam and multiple delayed reference beams before interfering with each other. By comparing information such as interference fringes, parameters such as the optical path difference can be accurately measured, thereby obtaining information such as the displacement and refractive index change of the object being measured. The delayed reference beam is a beam with a known phase and a fixed time delay. It is used to provide a phase reference and carry a time delay scale (such as a fixed optical path difference controlled by a piezoelectric translation stage). The modulated probe beam is a time-varying signal whose phase is modulated by the ultrafast event and carries information about the dynamic response of the ultrafast event (such as refractive index / density changes). The delayed reference light and the modulated probe light meet the coherence condition, and the optical path difference is less than the coherence length of the light source. The two interfere to form spatiotemporal modulation fringes. The fixed delay of the reference beam can be used to resolve the phase of the ultrafast event and its temporal evolution.

[0048] Specifically, during the process of combining the probe beam and the reference beam, only the probe beam with the corresponding time delay interferes with the reference beam, and the remaining light field serves as background information.

[0049] It can be expressed as follows:

[0050] in, is the intensity distribution of the reference light beam on the recording medium; in, is the sum of the light intensity distributions of all probes on the recording medium; in, is the interference term between the reference beam and the mth object beam.

[0051] In one embodiment of the present application, the light field resolution method further includes: incident an initial light beam at a certain angle, and dividing the initial light beam into a reference light beam and a probe light beam.

[0052] In this implementation, the reference and probe beams, generated from the same beam incident at the same angle, maintain the same initial state, ensuring consistency during subsequent experiments. The reference beam serves as a comparison or benchmark, while the probe beam detects physical quantities or material properties, creating a clear and straightforward division of labor. Furthermore, varying the incident angle yields different interference results, enabling comprehensive analysis of the physical properties of ultrafast events.

[0053] In one embodiment of the present application, see Figure 4 , Figure 4 The fourth flow chart of the light field resolution method provided in the embodiment of the present application. Based on the image formed by interference, the three-dimensional spatial distribution of the ultrafast event scene is obtained, including: S510: Acquire images generated by initial light beams incident at different angles; S520: Restoring the two-dimensional spatiotemporal distribution of the ultrafast event scene from the image; S530: Reconstructing the three-dimensional spatial distribution of the ultrafast event scene through the two-dimensional spatiotemporal distribution. In this implementation, when the initial light beam is incident at different angles, the different angles of illumination significantly alter the imaging effect. Its interaction with matter produces an angle-dependent response, and the differences in deflection of the beam at different incident angles carry information about the refractive index gradient. The optical signal of the ultrafast event is presented as a single-frame image, mapping the spatiotemporal information onto two-dimensional spatial coordinates. From this two-dimensional spatiotemporal distribution, the three-dimensional spatial distribution of the ultrafast event scene can be reconstructed.

[0054] Specifically, the recorded image, or hologram, is first subjected to a two-dimensional Fourier transform in the spatial domain. This transform converts the hologram from the spatial domain to the spatial frequency domain (i.e., the spectral domain). The resulting hologram spectrum typically exhibits three prominent peaks: a central zero-order peak and two symmetrically distributed first-order peaks. The zero-order peak primarily corresponds to the DC background component and incoherent illumination in the holographic recording. The two first-order peaks, however, carry crucial information, originating from the interference terms generated by the probe and reference beams. To effectively extract the target information and suppress interference, a low-pass filter is applied to the resulting spectrum (i.e., the Fourier transform result). The filter's core function is to remove background noise and stray light components from the zero-order peak at the center of the spectrum and its surrounding region. This filtering step selectively isolates and retains one of the first-order peaks (typically the side containing the target information). The spectrum of the isolated first-order peak, obtained after the low-pass filter, is then converted back to the original spatial domain by performing an inverse two-dimensional Fourier transform. The output of this inverse transformation process is a two-dimensional distribution of complex values, known as a complex amplitude field. This complex amplitude field accurately reconstructs the optical field state of the original probe beam on the recording plane. Ultimately, by analyzing this recovered complex amplitude field (which contains both amplitude and phase information of the light), key information about the ultrafast dynamic event recorded by the probe beam can be decoded. Bandpass filtering can be used to remove the zero-order peak and other noise, extracting the interference term. The filtered first-order spectrum is then inversely transformed back into the spatial domain to obtain the complex amplitude field of the interference result. The phase difference of the complex amplitude is directly calculated using the inverse tangent function. To avoid phase jumps, phase unwrapping is required to restore the continuous phase distribution. In other words, the spatial distribution of this complex amplitude field and its evolution over time (corresponding to different probe beam delays) directly reflect the temporal and spatial evolution of the ultrafast process being detected, thereby enabling the acquisition of high-resolution information about the ultrafast event scene.

[0055] In one embodiment of the present application, in order to reconstruct the three-dimensional spatial distribution of an ultrafast event scene through a two-dimensional spatiotemporal distribution, the two-dimensional images taken from multiple angles are first calibrated to establish a mapping relationship between the image coordinate system and the world coordinate system; then, the feature points of each image are extracted, and matching points under different perspectives are screened through feature matching and extreme geometric constraints, and the initial position of the three-dimensional points is calculated based on these matching points. Then, the disparity is calculated pixel by pixel through a stereo matching algorithm and a depth map is generated. The multi-perspective depth data is fused to construct a dense point cloud or mesh model. Finally, the multi-perspective texture is projected onto a three-dimensional surface to eliminate seams and lighting differences, generating a textured three-dimensional model.

[0056] In another embodiment of the present application, first, a camera calibration operation is performed on a two-dimensional image sequence captured from different perspectives. This step is intended to accurately solve the intrinsic parameter matrix of each camera (including focal length fx, fy, principal point coordinates (cx, cy) and lens distortion coefficients and the extrinsic parameter matrix (i.e., the rotation matrix R and translation vector t of the camera in the world coordinate system). Through calibration, a nonlinear mapping model between the image pixel coordinate system and the world three-dimensional coordinate system is established to provide a mathematical basis for subsequent geometric calculations. In each perspective image, key feature points with significant local structural information are detected (such as Harris corner points, FAST corner points, SIFT / SURF scale-invariant features or ORB binary features). A high-resolution feature map is generated for each feature point. The algorithm uses feature descriptors (such as SIFT, SURF, or ORB) and performs initial feature matching across viewpoints based on descriptor similarity metrics (such as Euclidean distance or Hamming distance) to establish a set of candidate matching point pairs. It leverages multi-view geometric constraints to improve matching robustness: A robust estimation algorithm (such as RANSAC or its improved variants) is used to fit the fundamental matrix FF (for uncalibrated cameras) or the essential matrix EE (for calibrated cameras). Based on the epipolar constraints derived from this matrix, the initial matches are geometrically verified for consistency, eliminating mismatched point pairs that do not meet the constraints and outputting a set of geometrically consistent and reliable matches.

[0057] Based on the screened reliable matching point pairs and their corresponding camera projection matrices, the linear triangulation method or the reprojection error minimization method is used to calculate the initial 3D coordinates X of the matching points in the world coordinate system to form a sparse 3D point cloud.

[0058] Dense matching is performed in stereo pairs, corresponding points are searched in the epipolar direction, and pixel similarity costs (such as SAD, SSD, normalized cross-correlation (NCC), Census transform, or Rank transform) are calculated. Costs are aggregated using local window weighted averaging (such as Gaussian weighting) or global optimization methods (such as semi-global matching (SGM)). Disparity calculation and optimization: The optimal disparity is selected through a winner-takes-all (WTA) strategy, combined with sub-pixel interpolation (such as parabola fitting) to improve accuracy. Left-right consistency checks, occlusion area detection, and adaptive filling are performed to convert the optimized dense disparity map into a depth map through geometric relationships based on the camera baseline distance B and focal length f.

[0059] The depth map generated by each viewpoint is transformed into a unified world coordinate system based on its camera extrinsic parameters: the truncated signed distance function (TSDF) is used to weightedly fuse the depth observation values in the 3D grid, and the isosurface is extracted through the MarchingCubes algorithm to generate the grid; the transformed point cloud is directly fused, and a continuous surface is generated through Poisson surface reconstruction (Poisson Surface Reconstruction) or Delaunay triangulation to output a globally consistent dense 3D mesh model M.

[0060] The original image is projected onto the 3D mesh surface: a UV mapping is established based on the projection relationship between the mesh vertices / patches and the image pixels; for each surface point, the multi-view color values are fused based on the cosine of the viewing angle (to reduce perspective distortion), the distance from the image boundary to avoid edge blurring, and the image quality weight wq; histogram matching or a correction algorithm based on radiometric constraints (such as photometric calibration in MVS) is applied to eliminate lighting differences and seams between viewpoints, ultimately generating a 3D model with high-fidelity texture mapping.

[0061] In the second aspect, the present application also provides a light field resolution system, see Figure 5 , Figure 5 The first schematic diagram of the light field resolution system provided in an embodiment of the present application. The light field resolution system includes: a delay control device 10, an ultrafast event generating device 20, a first beam splitting element 31, and a detection and analysis device 40; the delay control device 10 is used to delay the reference beam and the probe beam respectively to obtain a delayed reference beam and a delayed probe beam; the ultrafast event generating device 20 is used to establish an ultrafast event scene, and when the delayed probe beam passes through the ultrafast event scene, a modulated probe beam is obtained; the first beam splitting element 31 is used to change the direction of the modulated probe beam, wherein after the direction of the modulated probe beam is adjusted, the modulated probe beam can interfere with the delayed reference beam; the detection and analysis device 40 is used to record an image formed by the interference and obtain a three-dimensional spatial distribution of the ultrafast event scene based on the image formed by the interference.

[0062] In the above implementation process, the delay control device 10 applies a controllable time delay to the reference beam and the probe beam respectively, generating a delayed reference beam and a delayed probe beam with a timing difference. The ultrafast event generating device 20 establishes an ultrafast event scene to be measured (such as a physical / chemical reaction of the femtosecond order). When the delayed probe beam passes through the scene, its wavefront is modulated by the spatiotemporal characteristics of the ultrafast event, forming a modulated probe beam carrying event information. The first beam splitting element 31 changes the propagation direction of the modulated probe beam by reflection or refraction, so that it and the delayed reference beam are on the same path in space, creating geometric conditions for subsequent interference. The modulated probe beam and the delayed reference beam with adjusted direction coherently interfere in the spatial overlapping area, forming an interference pattern containing phase and intensity information. The detection and analysis device 40 is used to record and capture the two-dimensional spatial image formed by the interference. Based on the phase distribution in the interference image, the three-dimensional spatial modulation field of the ultrafast event on the probe beam is inverted, and then the transient three-dimensional spatial distribution of the ultrafast event scene is reconstructed.

[0063] Optionally, the delay control device 10 includes a first delay controller 11 and a second delay controller 12. The first delay controller 11 is configured to split the reference beam into multiple beams with different time delay scales to obtain delayed reference beams, and output the multiple delayed reference beams in parallel to different optical paths. The second delay controller 12 is configured to split the probe beam into multiple beams with different time delay scales, combine the beams to obtain a delayed probe beam, and output the beams to the same optical path.

[0064] Optionally, the first delay controller 11 can be an optical delay line array, which includes multiple independent delay channels, each channel consisting of a group of movable reflectors or optical elements with fixed optical path difference. Using different optical delay elements, it is possible to detect different time scales of ultrafast processes and different moments under the same time scale, and the detection time dimension is flexibly adjustable. The input reference beam is first divided into multiple paths by a beam splitter, each of which enters a delay channel, and after experiencing different time delays, it is output in parallel from its respective output ports to different optical paths. It can also be a fiber delay line array, which uses a beam splitter to couple the input reference beam into multiple optical fibers of different lengths. The length of each optical fiber is precisely controlled to achieve a specific time delay. The output end of the optical fiber serves as a parallel output port, guiding the reference beams with different delays to different optical paths. Or other core functions are beam splitting and multi-path independent output. The implementation scheme focuses on generating multiple beams with different delay values and keeping them physically separated. The advantage of using optical fiber is that the length can be easily controlled to achieve time delays of different scales. If only the spatial propagation delay method is used, in order to achieve precise long-term window delay, the requirements for optical path construction and space are very high.

[0065] Optionally, the second delay controller 12 can be a continuously adjustable optical delay line, which is usually composed of a reflector group mounted on a precision translation stage. The probe beam is introduced into the delay line. By controlling the linear displacement of the reflector, the optical path of the probe beam is continuously changed, thereby achieving continuous adjustment of its time delay, and the output is a delayed probe beam adjusted through a single channel. It can also be a rotating optical delay line, which utilizes a rotating glass plate or a birefringent crystal. As the plate rotates or the crystal angle changes, the optical thickness through which the light beam passes changes periodically, thereby achieving continuous scanning of the delay time, and the output is a delayed beam of a single optical path. Or other core functions are to apply a continuously adjustable delay to a single beam with a single-path output. The implementation scheme focuses on continuously adjusting the optical path / delay of a single path, and the output is still a single beam of the same optical path (or after beam combining).

[0066] Alternatively, the detection and analysis device 40 can be a multi-channel spectrometer. The delayed reference beam and delayed probe beam (or their combined interference light) from different optical paths are coupled separately into different entrance slits or fiber optic inlets of the multi-channel spectrometer. Gratings are used within the spectrometer to disperse light of different wavelengths onto different pixels of an area array detector (e.g., CCD or sCMOS). This allows for simultaneous acquisition of spectral information from multiple optical paths.

[0067] In one embodiment of the present application, see Figure 6 , Figure 6 This is a second schematic diagram of the light field resolution system provided in an embodiment of the present application.

[0068] The light field resolution system further includes: a light source generating device 50 and a second beam splitting element 32; the light source generating device 50 is used to generate an initial light beam, which is incident on the second beam splitting element 32 along a certain angle; the second beam splitting element 32 splits the initial light beam into a reference beam and a probe beam.

[0069] In this implementation, the light source generator 50 generates an initial laser beam (typically a femtosecond pulsed laser) with high spatiotemporal coherence. Its beam parameters (pulse width, wavelength, and energy) must meet the temporal resolution and sensitivity requirements for ultrafast event detection. A second beam splitter 32 receives the initial beam and, acting at a specific angle of incidence, decomposes it into two beams via a beam splitting interface (a coated prism or polarization beam splitter): a probe beam that is subsequently injected into the detection carrier of the ultrafast event scene, and a reference beam that serves as a coherent reference unmodulated by the event.

[0070] In one embodiment of the present application, the light field resolution system further includes: a first imaging device 61 and a second imaging device 62; the first imaging device 61 is used to present the modulated probe beam to the detection and analysis device 40; the second imaging device 62 is used to present multiple delayed reference beams to the detection and analysis device 40 respectively.

[0071] In the above implementation, the first imaging device 61 is located in the optical path of the modulated probe beam. Its core function is to image the modulated probe beam carrying the spatial modulation information of the ultrafast event onto the target surface of the detection and analysis device 40 at a scaling factor that matches the detector resolution (e.g., a 4f system), compensating for wavefront distortion introduced by the ultrafast event device or beam splitting element to ensure the fidelity of the interference pattern. The second imaging device 62 is located in the optical path of the multi-delay reference beam. It couples reference beams of different delay states onto the same optical axis through time-division multiplexing or spatial multiplexing, and collimates and images them onto the target surface of the detection and analysis device 40. The optical path difference is controlled to be within the coherence length to ensure interference capability with the modulated probe beam.

[0072] Alternatively, the first imaging device 61 may be a combination of a prism group and an image receiving device, preferably forming a 4f system.

[0073] Alternatively, the second imaging device 62 may be a combination of a plurality of right-angle prisms and an image receiving device. The right-angle prisms may be used to fold the optical path and guide the reference beams in different delay states to the same optical axis.

[0074] See also Figure 7 , Figure 7 This is a third schematic diagram of the light field resolution system provided in an embodiment of the present application.

[0075] In one embodiment of the present application, a plasma plume is used in the ultrafast event scenario. The focal length of the first lens 01 is the distance from the first lens to the plasma plume, and the lens is used to image the plasma plume. The focal length of the second lens 02 is not specifically required; it is only used to maintain the same static curvature of the wavefront between the reference beam and the probe beam when they reach the recording plane of the detection and analysis device 40, thereby obtaining straight interference fringes. The first lens 01 and the third lens 03 form a 4F system. The focal length of the third lens 03 should be exactly equal to the distance from the third lens to the CCD or other image receiving device. Furthermore, the second beam splitter 32 uses a beam splitter (BS) to separate and reflect the different probe beams. The first beam splitter 31 in the final path uses a reflector (M) to prevent laser leakage. The reflector parameters are not specifically required. During optical path construction, to avoid excessive laser power, components with high damage thresholds should be used. A beam expander 21 is used to expand the delayed probe beam before it passes through the plasma plume, and a beam reducer 22 is used to reduce the delayed probe beam after it passes through the plasma plume.

[0076] In summary, the present application provides a light field resolution method and device, relating to the field of laser propulsion technology. The light field resolution method includes: delaying a reference beam to obtain a delayed reference beam; delaying a probe beam to obtain a delayed probe beam; passing the delayed probe beam through an ultrafast event scene to obtain a modulated probe beam; interfering the modulated probe beam with the delayed reference beam to obtain an interference-formed image; and obtaining a three-dimensional spatial distribution of the ultrafast event scene based on the interference-formed image. Through its three-dimensional spatial distribution, a specific connection between laser parameters and coupling coefficients can be established, allowing the morphology and characteristics of the ultrafast event scene to be analyzed from multiple perspectives, such as time and space.

[0077] In the several embodiments provided in this application, it should be understood that the disclosed devices can also be implemented in other ways. The device embodiments described above are merely schematic. For example, the block diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices according to the multiple embodiments of the present application. In this regard, each box in the block diagram can represent a module, a program segment or a part of a code, and the module, program segment or a part of the code contains one or more executable instructions for implementing the specified logical functions. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. For example, two consecutive boxes 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 the combination of the block diagrams, can be implemented with a dedicated hardware-based system that performs the specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0078] In addition, the functional modules in each embodiment of the present application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0079] The foregoing is merely an embodiment of the present application and is not intended to limit the scope of protection of the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application. It should be noted that similar reference numerals and letters represent similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined or explained in subsequent figures.

[0080] The above is only a specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed in this application, which should be covered by the scope of protection of the present application.

[0081] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, the elements defined by the phrase "comprising..." do not exclude the presence of other identical elements in the process, method, article, or device comprising the elements.

Claims

1. A light field resolution method, characterized in that: The light field resolution method comprises: Delaying the reference beam to obtain a delayed reference beam; Delaying the probe beam to obtain a delayed probe beam; Passing the delayed probe beam through an ultrafast event scene to obtain a modulated probe beam; interfering the modulated probe beam with the delayed reference beam to obtain an interference-formed image; Based on the image formed by interference, obtaining a three-dimensional spatial distribution of the ultrafast event scene; When the three-dimensional spatial distribution is obtained, the physical characteristics of the ultrafast event scene are analyzed.

2. The method according to claim 1, characterized in that The delaying of the reference beam to obtain a delayed reference beam includes: The reference beam is divided into a plurality of beams with different event delay scales to obtain the delayed reference beam, and the plurality of delayed reference beams are output in parallel to different optical paths.

3. The method according to claim 1, characterized in that The delaying of the probe beam to obtain the delayed probe beam comprises: The probe beam is divided into a plurality of beams with different time delay scales, and the delayed probe beam is obtained after beam combination and output to the same optical path.

4. The method according to claim 1, wherein The step of passing the probe beam through an ultrafast event scene to obtain a modulated probe beam comprises: Expanding the delayed probe beam to obtain an expanded probe beam; When the beam-expanded probe beam passes through the ultrafast event scene, the beam-expanded probe beam is subjected to beam-contraction processing to obtain the modulated probe beam; Wherein, the ultrafast event scene includes a plasma plume.

5. The method according to claim 2, characterized in that The interfering the modulated probe beam with the delayed reference beam to obtain an interference-formed image comprises: Superimposing the modulated probe beam and the plurality of delayed reference beams respectively; The delayed reference beam corresponding to the time delay interferes with the modulated probe beam, and the remaining beams serve as background information.

6. The method according to claim 1, characterized in that The light field resolution method further includes: An initial beam is incident along a certain angle, and the initial beam is divided into the reference beam and the probe beam.

7. The method according to claim 6, characterized in that The step of obtaining the three-dimensional spatial distribution of the ultrafast event scene based on the image formed by interference includes: acquiring the images generated by the initial light beams incident at different angles; restoring the two-dimensional spatiotemporal distribution of the ultrafast event scene from the image; The three-dimensional spatial distribution of the ultrafast event scene is reconstructed through the two-dimensional spatiotemporal distribution.

8. A light field resolution system, characterized in that: The light field resolution system includes: a time delay control device, an ultrafast event generation device, a first beam splitting element, and a detection and analysis device; The delay control device is used to delay the reference beam and the probe beam respectively to obtain a delayed reference beam and a delayed probe beam; The ultrafast event generating device is used to establish an ultrafast event scene, and when the delayed probe beam passes through the ultrafast event scene, a modulated probe beam is obtained; The first beam splitting element is used to change the direction of the modulated probe beam, wherein after the direction of the modulated probe beam is adjusted, the modulated probe beam interferes with the delayed reference beam; The detection and analysis device is used to record the image formed by interference, and obtain the three-dimensional spatial distribution of the ultrafast event scene based on the image formed by interference.

9. The system according to claim 8, characterized in that The light field resolution system further comprises: a light source generating device and a second beam splitting element; The light source generating device is used to generate an initial light beam, and the initial light beam is incident on the second beam splitting element along a certain angle; The second beam splitting element splits the initial beam into the reference beam and the probe beam.

10. The system according to claim 8, wherein: The light field resolution system further includes: a first imaging device and a second imaging device; The first imaging device is used to present the modulated probe beam to the detection and analysis device; The second imaging device is used to present the multiple delayed reference beams to the detection and analysis device respectively.

Images