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We investigate the dynamic excitation of surface plasmon polaritons (SPPs) using vector Laguerre–Gauss (LG) beams, which offer unique properties for manipulating the polarization and spatial distribution of light. Our study demonstrates the efficient coupling of SPPs with LG beams, characterized by their azimuthal and radial indices (m,p), as well as polarization distribution type. Numerical simulations reveal that the vector nature of LG beams enables selective excitation of SPPs, depending on the polarization type of the beam. Experimental verification of our simulations is achieved using a gold circular Bragg grating and a spatial light modulator that generates vector LG beams. Leakage radiation imaging demonstrates the potential of vector LG beams for dynamic SPP excitation and manipulation. This study opens novel ways for the control of SPPs in plasmonic devices, such as modulators, and nanophotonic circuits.

The recent discovery that linearly polarized light with a helical wavefront can exhibit vortex dichroism (also referred to as helical dichroism) has opened up new horizons in chiroptical spectroscopy with structured chiral light. Recent experiments have now pushed optical activity with vortex beams into the regime of nonlinear optics. Here the theory of two‐photon absorption (TPA) of focused optical vortices by chiral molecules: nonlinear vortex dichroism (NVD) is presented. It is discovered that highly distinct features arise in the case of TPA with focused vortex beams, including the ability to probe chiral molecular structure not accessible to current methods and that the differential rate of TPA is significantly influenced by the orientation of the state of linear polarization. This study provides strong evidence that combining nonlinear optical activity with structured light provides new and improved routes to studying molecular chirality. [ABSTRACT FROM AUTHOR]

To achieve high-precision 3D reconstruction, a comprehensive improvement has been made to the binocular structured light calibration method. During the calibration process, the calibration object's imaging quality and the camera parameters' nonlinear optimization effect directly affect the caibration accuracy. Firstly, to address the issue of poor imaging quality of the calibration object under tilted conditions, a pixel-level adaptive fill light method was designed using the programmable light intensity feature of the structured light projector, allowing the calibration object to receive uniform lighting and thus improve the quality of the captured images. Then, collaborative Particle Swarm Optimization was studied to optimize the camera parameters. Compared with other optimization algorithms, this algorithm has higher global search capability and can obtain more accurate camera parameters. Under comprehensive improvement, the 3D reconstruction accuracy of binocular structured light is 0.053 mm, showing a 36.33% improvement in reconstruction accuracy compared to mainstream calibration methods. [ABSTRACT FROM AUTHOR]

For achieving non-contact high-precision and rapid online measurement of the surface contour and key geometric dimensions of moving workpieces on a roll forming steel production line, the paper presents a roll-formed part online measurement system based on multi-view vision and structured light. Initially, the system achieves high-precision global calibration using a planar target and multi-objective calibration principles. And then the spatial pose relationship of multi-head measurement coordinate system space was calculated. Subsequently, second-order algorithms were employed for precise image projection correction to accomplish 3D reconstruction. Finally, the center of light stripes at sub-pixel level was extracted. Firstly, a pruning algorithm was utilized to eliminate random errors along the stripe center line, and then obtain precise point cloud data of the structured light, next reconstruct the workpiece's cross-sectional features and measurement of its bending angles and outer contour dimensions, and finally complete online monitoring of workpiece dimensions. Experimental results demonstrate that the measurement accuracy of this online measurement system is 0.05 mm, which indicates its high precision and accuracy. This system has promising applications in the roller-forming industry and significantly improving workpiece detection efficiency. [ABSTRACT FROM AUTHOR]

Material anisotropy and chirality produce polarization‐dependent light‐matter interactions. Absorption leads to linear and circular dichroism, whereas elastic forward scattering produces linear and circular birefringence. Here a form of dichroism and birefringence is highlighted whereby generic anisotropic media display locally different absorption and scattering of a focused vortex beam that depends upon the sign of the topological charge ℓ$\ell$. The light‐matter interactions described in this work manifest purely through dominant electric‐dipole coupling mechanisms and depend on the paraxial parameter to first‐order. Previous topological‐charge‐dependent light‐matter interactions require the significantly weaker higher‐order multipole moments and are proportional to the paraxial parameter to second‐order. The result represents a method of probing the nano‐optics of advanced materials and the topological properties of structured light. [ABSTRACT FROM AUTHOR]

A matrix formalism, denoted as ABCD, has been developed and experimentally implemented to describe structured transformations and the orbital angular momentum of structured Laguerre–Gaussian beams in an astigmatic optical system containing a single cylindrical lens. It is demonstrated that the matrix formalism not only aligns well with the method of integral astigmatic transformations but also significantly broadens the scope of its application. [ABSTRACT FROM AUTHOR]

We have shown theoretically and experimentally that for defining the orbital angular momentum (OAM) of structured Laguerre-Gaussian (sLG) beams with a broken symmetry, it is sufficient to measure the only element of the symplectic intensity moment matrix. It looks like an intertwining of two elements belonging to two submatrices of the general symplectic matrix of intensity moments under the condition when the amplitude parameter of the sLG beam is equal to unity. But once slightly to deviate the amplitude parameter from this value, as the intertwining at once unravels. Besides, we revealed that by measuring such a matrix element of the sLG beam in free space enables us to exactly predict the OAM behavior of the sLG beam in a first-order optical system with an astigmatic element, without any measuring in the astigmatic system itself. [ABSTRACT FROM AUTHOR]

The shape of a PCB surface, i.e., its topography, influences many functional properties of the designed circuit. In this paper, we propose the utilization of a non-contact, non-invasive, and non-destructive simplified microscopic fringe projection technique for the surface profiling of copper-clad PCBs. Here, a digital micromirror device (DMD) is used to project a high spatial fringe density at the surface of copper-clad PCBs to achieve high-speed profilometry, which can avoid disturbance due to in-field vibrations. Furthermore, the optimal spatial frequency of 70 µm pitch is selected empirically to minimize phase error by comparing the sample's surface phase map at different spatial frequencies. The experimentally calculated average height using optimal spatial frequency for the central portion of the antenna's surface is found to be 13.46 µm, and it is well in coordination with the height of 14.72 µm obtained using a standard roughness tester. The qualitative and quantitative experimental results verified the practical applicability of the fringe projection system for measuring the surface profiling of copper-clad PCB. [ABSTRACT FROM AUTHOR]

We investigate the dynamic excitation of surface plasmon polaritons (SPPs) using vector Laguerre–Gauss (LG) beams, which offer unique properties for manipulating the polarization and spatial distribution of light. Our study demonstrates the efficient coupling of SPPs with LG beams, characterized by their azimuthal and radial indices (m , p) , as well as polarization distribution type. Numerical simulations reveal that the vector nature of LG beams enables selective excitation of SPPs, depending on the polarization type of the beam. Experimental verification of our simulations is achieved using a gold circular Bragg grating and a spatial light modulator that generates vector LG beams. Leakage radiation imaging demonstrates the potential of vector LG beams for dynamic SPP excitation and manipulation. This study opens novel ways for the control of SPPs in plasmonic devices, such as modulators, and nanophotonic circuits. [ABSTRACT FROM AUTHOR]

Backflow, or retropropagation, is a counterintuitive phenomenon whereby for a forward-propagating wave the energy locally propagates backward. In the context of backflow, physically most interesting are the so-called unidirectional waves, which contain only forward-propagating plane wave constituents. Yet, very few such waves possessing closed-form analytic expressions for evaluation of the Poynting vector are known. In this study, we examine energy backflow in a novel (2+time)-dimensional unidirectional monochromatic wave and in a (2+1)D spatiotemporal wavepacket, analytic expressions which we succeeded to find. We also present a detailed study of the backflow in the "needle" pulse. This is an interesting model object because well-known superluminal non-diffracting space–time wave packets can be derived from its simple factored wave function. Finally, we study the backflow in an unidirectional version of the so-called focus wave mode—a pulse propagating luminally and without spread, which is the first and most studied representative of the (3+1)D non-diffracting space–time wave packets (also referred to as spatiotemporally localized waves). [ABSTRACT FROM AUTHOR]

Three‐dimensional (3D) reconstruction based on structured light (SL) has wide applications in fields such as artificial intelligence, surveying and mapping, and precision manufacturing. An ideal 3D reconstruction system features both wide field‐of‐views (FOV), high‐accuracy and high‐speed reconstruction and ultracompact volume. However, these criteria have been achieved only partially with conventional SL techniques like optical projector and differentiate optical element, which will substantially limit their practical applications. In this study, an ultracompact SL and its 3D reconstruction system is designed and experimentally demonstrated, which exhibits super‐large FOV angles up to 210° × 210°, only 3.8‰ reconstruction errors, real‐time processing speeds up to 30 fps and SL dimensions as small as 0.3 mm × 0.3 mm. Specifically, the SL is realized with a resonant geometric metasurface, which can produce tens of thousands of random dots and project them into the whole 4π free space. The metasurface enabled SL is collaborated with a binocular stereoscopic camera and advanced 3D reconstruction algorism to form a practical 3D reconstruction system, which can provide robust hardware and software support for high‐accuracy and real‐time 3D scene reconstruction. [ABSTRACT FROM AUTHOR]

Palaeolithic graphic activity documentation is essential not only for its preservation and dissemination but also for its scientific analysis. Nowadays, researchers can use advanced techniques such as photogrammetry, lidar, or structured light scanning to record this heritage. However, there is a lack of studies comparing these three technologies. Therefore, this article presents a comparison of these techniques based on three variables: namely, time employed, geometric reconstruction, and resolution. The study examines how these factors affect the final result of the digital recording of rock art. A mold of Rock 11 from Domingo García (Segovia, Spain) and the archaeological panel S.4 from La Salud (Salamanca, Spain) have been used as test control examples. The results indicate that photogrammetry using a DSLR camera is the most efficient technique, providing the necessary reconstruction to obtain scientific data. [ABSTRACT FROM AUTHOR]

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An analogy with the polarization Stokes parameters and symplectic methods of the second-order intensity moment matrix allowed us to develop a simple technique for measuring the orbital Stokes parameters followed by mapping the structured beam states onto the orbital Poincaré sphere. The measurement process involves only two shots of the beam intensity patterns in front of a cylindrical lens and in its double focus. Such a simple measurement approach is based on the reciprocity effect between the experimentally measured cross-intensity element W x y and the orbital angular momentum of the intensity moment matrix. For experiments, we chose two types of two-parameter structured beams, namely, structured Laguerre–Gaussian beams and binomial beams. We obtained a good agreement between our theoretical background and the experiments, as well as the results of other authors. [ABSTRACT FROM AUTHOR]

This study introduces a technique for determining surface orientations by projecting a monochrome, spatial pixel-encoded pattern and calculating the surface normals from single-shot measurement. Our method differs from traditional methods, such as shape from shading and shape from texture, in that it does not require relating the local surface orientations of adjacent points. We propose a multi-resolution system incorporating symbols varying in sizes from 8 × 8, 10 × 10, 12 × 12, 14 × 14, and 16 × 16 pixels. Compared to previous methods, we have achieved a denser reconstruction and obtained a 5.2 mm resolution using an 8 × 8 pattern at a depth of 110 cm. Unlike previous methods, which used local point orientations of grid intersection and multiple colors, we have used the monochrome pattern and deterministic centroid positions to compute the unit vector or direction vector between the neighboring symbols. The light plane intersections are used to calculate the tangent vectors on the surface. Surface normals are determined by the cross-product of two tangent vectors on the surface. A real experiment was conducted to measure simple plane surfaces, circular surfaces, and complex sculptures. The results show that the process of calculating surface normals is fast and reliable, and we have computed 1654 surface normals in 29.4 milliseconds for complex surfaces such as sculptures. [ABSTRACT FROM AUTHOR]

Structured light refers to the light field tailored by various degrees of freedom including intensity, phase, and polarization states in both spatial and temporal domains, which may greatly vitalize the technologies in both optics, such as the next‐generation optical communication as well as subwavelength imaging and the materials science in both fabrication and characterization. The structured characteristics of the structure light need materials also with structured optical properties that can generate or manipulate structured light in a straightforward way, which can be well satisfied by liquid crystals, a soft mater that can self‐assemble into tunable ordered structures through external stimuli. This review summarizes the research progress of the liquid crystal‐based devices used in structured light generations and modulations, including the well‐established techniques in the market, like the spatial light modulator, q‐plate and the liquid crystal integrated optical metasurfaces. Especially, light‐matter interactions are discussed from the topological view of both the structured light and the liquid crystal structures. Such a perfect matching in topology makes the liquid crystal a promising star together with structured light in future optic and photonic technologies. [ABSTRACT FROM AUTHOR]

Progress in the semiconductor industry relies on the development of increasingly compact devices consisting of complex geometries made from diverse materials. Precise, label‐free, and real‐time metrology is needed for the characterization and quality control of such structures in both scientific research and industry. However, optical metrology of 2D sub‐wavelength structures with nanometer resolution remains a major challenge. Here, a single‐shot and label‐free optical metrology approach that determines 2D features of nanostructures, is introduced. Accurate experimental measurements with a random statistical error of 18 nm (λ/27) are demonstrated, while simulations suggest that 6 nm (λ/81) may be possible. This is far beyond the diffraction limit that affects conventional metrology. This metrology employs neural network processing of images of the 2D nano‐objects interacting with a phase singularity of the incident topologically structured superoscillatory light. A comparison between conventional and topologically structured illuminations shows that the presence of a singularity with a giant phase gradient substantially improves the retrieval of object information in such an optical metrology. This non‐invasive nano‐metrology opens a range of application opportunities for smart manufacturing processes, quality control, and advanced materials characterization. [ABSTRACT FROM AUTHOR]

We interpret the intrinsic mechanism of the transition from geometric modes to eigenmodes in the Gaussian wave-packet representation based on numerical simulation. We then construct multiaxial super-geometric modes and polygonal vortex modes based on Gaussian wave packets. We highlight that the superposition of Gaussian wave packets can build the geometric modes described by Hermite polynomials and that the eigenmodes are the result of the interference of Gaussian wave packets. We conclude that Gaussian wave packets might serve as a complete basis for constructing structured light generated in solid-state laser cavities. Our study may provide meaningful insight into Gaussian wave packets for laser transverse modes. [ABSTRACT FROM AUTHOR]

Orbital angular momentums (OAMs) greatly enhance the channel capacity in free-space optical communication. However, demodulation of superposed OAM to recognize them separately is always difficult, especially upon multiplexing more OAMs. In this work, we report a directly recognition of multiplexed fractional OAM modes, without separating them, at a resolution of 0.1 with high accuracy, using a multi-task deep learning (MTDL) model, which has not been reported before. Namely, two-mode, four-mode, and eight-mode superposed OAM beams, experimentally generated with a hologram carrying both phase and amplitude information, are well recognized by the suitable MTDL model. Two applications in information transmission are presented: the first is for 256-ary OAM shift keying via multiplexed fractional OAMs; the second is for OAM division multiplexed information transmission in an eightfold speed. The encouraging results will expand the capacity in future free-space optical communication. [ABSTRACT FROM AUTHOR]

Structured-light scanning is a fast and efficient technique for the acquisition of 3D point clouds. However, the extensive and daily application of this class of scanners can be challenging because of the technical know-how necessary to validate the low-cost instrumentation. This challenge is worth accepting because of the large amount of data that can be collected accurately with the aid of specific technical protocols. This work is a preliminary study of the development of an acquisition protocol for anthropological remains performing tests in two opposite and extreme contexts: one characterised by a dark environment and one located in an open area and characterised by a very bright environment. This second context showed the influence of sunlight in the acquisition process, resulting in a colourless point cloud. It is a first step towards the development of a technical protocol for the acquisition of anthropological remains, based on the research of limits and problems associated with an instrument.

Dynamic and responsive structural color devices present promising opportunities for sensing and display technologies, with applications including point‐of‐care diagnostics, portable/wearable sensors, and low‐power full‐color displays. However, it is often difficult to generate a large and quantitatively meaningful colorimetric response especially toward weak stimuli. Here, dual‐band hyperchromatic structural color (HSC) is presented as an approach to overcome these challenges. Within this framework, a dual‐band mesoporous silicon rugate filter metamaterial co‐designed is experimentally realized for use with a dichromatic (red/green) illuminant. This is shown to enable an amplified red‐to‐green color transition with a substantially smaller wavelength shift than conventional structural color devices, Δλ ≪ |λG – λR|, as well as a direct quantitative mapping between the observed chromaticity and the input stimulus. This approach is experimentally demonstrated for the spatiotemporally resolved sensing of refractometric stimuli including small‐molecules and volatile organic compounds (VOCs) with a ≈0.08 nm equivalent spectral resolution. This approach is entirely scanning‐free, enabled by simple color imaging, and does not require advanced spectroscopic (hyperspectral) imaging or interferometric imaging to obtain meaningful quantitative and spatiotemporally resolved information pertaining to the sensor's attributes. These results demonstrate dual‐band HSC as a promising approach for realizing low‐cost and high performance dynamic structural color devices and sensors. [ABSTRACT FROM AUTHOR]

Optical skyrmions are topologically stable quasiparticles that can be constructed with electric field, spin angular momentum, polarization Stokes vector, pseudospin, etc. In this letter, both theoretical and experimental studies are carried out to reveal the role of Gouy phase in the topology transformation during the tight focusing of Stokes skyrmions. The Stokes skyrmionic beam can be constructed by superposing two orthogonally polarized components with orthogonal spatial modes. The Gouy phase produced in the focused field depends on the orbital angular momentum carried by the high order mode component of the incident Stokes skyrmionic beam. While the beam size of the focused field is diffraction limited, the variation of the Stokes vectors in the skyrmion topology is in the sub‐diffraction limited scale. The presented results shed light on the understanding of the topology transformation between the incident and the tightly focused fields, paving the way for engineering the optical skyrmions in micro‐nano scale and their applications in information processing, quantum technology, metrology, etc. [ABSTRACT FROM AUTHOR]

At present, the commonly used three-dimensional shape measurement technology of large-sized workpieces has the problems of poor robustness, low measurement efficiency and high cost. In order to solve the above problems, we propose a new measurement method which combines linear structured light and stereoscopic tracking. This paper mainly describes the linear structured light measurement system. A secondary extraction algorithm is designed based on the normal direction according to the commonly used laser stripe center line extraction algorithm. The algorithm improves the Gaussian curve fitting method. By combining the fine state refinement method, Hessian matrix method, Gaussian curve fitting and light plane calibration, the fast extraction of the center line of the laser stripe is completed, and the mapping relationship between the two-dimensional coordinates of the points on the laser center line and the three-dimensional coordinates in the camera coordinate system is obtained. We conducted feasibility experiments, and the preliminary experimental results indicate that this approach is valid, with measurement errors controlled within 0.44%. [ABSTRACT FROM AUTHOR]

A theoretical analysis is presented on the photoexcitation of a macroscopic atomic target by a Hermite–Gaussian (HG) beam within the framework of density matrix theory. Special emphasis is paid to the influence of the incoming HG mode on the population of an excited state and the emitted fluorescence radiation. In particular, a general expression for the alignment parameter of the excited state is derived, which depends on the beam parameters of the HG mode. Although the developed theory can be applied to any atomic system, here the electric dipole transition 3s2S1/2→3p2P3/2$3s\; {}^{2}S_{1/2}\nobreakspace \rightarrow \nobreakspace 3p \; {}^{2}P_{3/2}$ in neutral sodium atoms is investigated when driven by three HG10${\rm HG}_{10}$, HG01,${\rm HG}_{01,}$ and HG11${\rm HG}_{11}$ modes. For this optical (valence‐shell) excitation, it is demonstrated that the population of the excited state is sensitive to the beam waist and the mode index of the HG beam. Furthermore, the influence of beam parameters on the angular distribution and linear polarization of the emitted fluorescence radiation is discussed. [ABSTRACT FROM AUTHOR]

Structured-light scanning is a fast and efficient technique for the acquisition of 3D point clouds. However, the extensive and daily application of this class of scanners can be challenging because of the technical know-how necessary to validate the low-cost instrumentation. This challenge is worth accepting because of the large amount of data that can be collected accurately with the aid of specific technical protocols. This work is a preliminary study of the development of an acquisition protocol for anthropological remains performing tests in two opposite and extreme contexts: one characterised by a dark environment and one located in an open area and characterised by a very bright environment. This second context showed the influence of sunlight in the acquisition process, resulting in a colourless point cloud. It is a first step towards the development of a technical protocol for the acquisition of anthropological remains, based on the research of limits and problems associated with an instrument. [ABSTRACT FROM AUTHOR]

Parts with a large depth-to-diameter ratio play a critical role in the military, aerospace, and automotive industries. However, accurately measuring their inner surface profile remains challenging owing to the lack of adequate and accurate sensors. We developed a multi-ring structured light system to obtain three-dimensional data of inner contours, such as inner diameters, which are crucial for ensuring component performance and safety. In this study, we proposed three simple yet effective techniques to improve the multi-ring beam structured measurement system. First, we designed a distortion correction method to calibrate the imaging system. Second, a two-step calibration approach was used to calibrate the multi-ring projection. Meanwhile, we benchmarked the effects of different light sources on image speckles. The calibration results demonstrated that the coefficient of determination (R-2) used for line fitting exceeded 0.999. Moreover, the measurement experimental results show that the uncertainty of less than 10 µm and the smallest measurable pipe inner diameter can reach 15 mm, demonstrating that our methods are promising for improving the accuracy of structured light optical sensing systems. This system satisfies the measurement requirements and can be immediately utilized to meet the high demand for inner contour measurements in industrial applications. [ABSTRACT FROM AUTHOR]

A thick-lens, structured-light measurement model is introduced to overcome the oversights in traditional models, which often disregard the impact of lens thickness. This oversight can lead to inaccuracies in Scheimpflug camera calculations, causing systematic errors and diminished measurement precision. By geometrical optics, the model treats the camera as a thick lens, factoring in the locations of its principal points and the spatial shifts due to image plane tilting. The model deduces the positional relationship of the thick lens with a tilted optical axis and establishes a linear-structured-light measurement model. Simulations confirm that the model can precisely calculate the 3D coordinates of subjects from image light strip data, markedly reducing systematic errors across the measurement spectrum. Moreover, experimental results suggest that the refined sensor model offers enhanced accuracy and lower standard deviation. [ABSTRACT FROM AUTHOR]

Most optical phenomena result from the interaction of electromagnetic waves with matter. However, the light structure can be eminently more complex than plane waves, with many degrees of freedom and dimensions involved, yielding intricate configurations. Light transcends the conventional landscape of electromagnetism, offering the possibility to tailor light in three dimensions (intermixing all three electric field components), in four-dimensional spacetime (for fields manifesting both temporal and spatial patterns), and, beyond that, to make structured quantum light, tuning its characteristics at an unprecedented new level of control. This article addresses the physical foundations of structured light, its interactions with matter, including the nonlinear regime and probing chirality, its classical benefits with holography as a specific highlight, and quantum mechanical applications. It describes the various applications connecting structured light with material physics, quantum information, and technology. Notably, we discuss weak measurements with structured light acting as the meter with connections to probing structured-light beam shifts at interfaces. Ultimately, revealing the interplay between structured light and matter opens attractive avenues for different new technologies and applications, covering both the classical and the quantum realms. [ABSTRACT FROM AUTHOR]

In 3D optical metrology, single-shot deep learning-based structured light profilometry (SS-DL-SLP) has gained attention because of its measurement speed, simplicity of optical setup, and robustness to noise and motion artefacts. However, gathering a sufficiently large training dataset for these techniques remains challenging because of practical limitations. This paper presents a comprehensive DL-SLP dataset of over 10,000 physical data couples. The dataset was constructed by 3D-printing a calibration target featuring randomly varying surface profiles and storing the height profiles and the corresponding deformed fringe patterns. Our dataset aims to serve as a benchmark for evaluating and comparing different models and network architectures in DL-SLP. We performed an analysis of several established neural networks, demonstrating high accuracy in obtaining full-field height information from previously unseen fringe patterns. In addition, the network was validated on unique objects to test the overall robustness of the trained model. To facilitate further research and promote reproducibility, all code and the dataset are made publicly available. This dataset will enable researchers to explore, develop, and benchmark novel DL-based approaches for SS-DL-SLP. [ABSTRACT FROM AUTHOR]

We describe a family of paraxial and quasi-monochromatic optical wave packets with finite energy and smoothly shaped amplitude in space and time that develops a singularity in the intensity when spatio-temporally focused by imparting a converging spherical wavefront and a negative temporal chirp. This singular behavior upon ideal focusing is manifested in actual focusing with finite apertures and in media with high-order dispersion with "exploding" behavior featuring an indefinitely increasing concentration of the energy when opening the aperture radius, thus exercising continuous control on the focal intensity and spatial and temporal resolution. These wave packets offer a new way of focusing that outperforms what can be achieved with standard Gaussian wave packets in terms of focal intensity and resolution, providing new possibilities in applications where energy concentration and its control are crucial. [ABSTRACT FROM AUTHOR]

Purpose: Arthroscopic surgery, with its inherent difficulties on visibility and maneuverability inside the joint, poses significant challenges to surgeons. Video-based surgical navigation (VBSN) has proven to have clinical benefits in arthroscopy but relies on a time-consuming and challenging surface digitization using a touch probe to accomplish registration of intraoperative data with preoperative anatomical models. This paper presents an off-the-shelf laser scanner for noninvasive registration that enables an increased area of reachable region. Methods: Our solution uses a standard arthroscope and a light projector with visual markers for real-time extrinsic calibration. Nevertheless, the shift from a touch probe to a laser scanner introduces a new challenge—the presence of a significant amount of outliers resulting from the reconstruction of nonrigid structures. To address this issue, we propose to identify the structures of interest prior to reconstruction using a deep learning-based semantic segmentation technique. Results: Experimental validation using knee and hip phantoms, as well as ex-vivo data, assesses the laser scanner's effectiveness. The integration of the segmentation model improves results in ex-vivo experiments by mitigating outliers. Specifically, the laser scanner with the segmentation model achieves registration errors below 2.2 mm, with the intercondylar region exhibiting errors below 1 mm. In experiments with phantoms, the errors are always below 1 mm. Conclusion: The results show the viability of integrating the laser scanner with VBSN as a noninvasive and potential alternative to traditional methods by overcoming surface digitization challenges and expanding the reachable region. Future efforts aim to improve hardware to further optimize performance and applicability in complex procedures. [ABSTRACT FROM AUTHOR]