Optical Scanning System Research Articles

The KERATO Biomechanics Study 1: A Comparative Evaluation Using Brillouin Microscopy and Dynamic Scheimpflug Imaging.

To assess the corneal biomechanical properties in normal individuals and patients with keratoconus using the Brillouin optical scanning system (Intelon Optics) (BOSS) and compare them with ultra-high-speed Scheimpflug imaging (Corvis ST; Oculus Optikgeräte GmbH). Sixty eyes from 60 patients (30 normal and 30 keratoconus) were included in this prospective, single-center, comparative, non-interventional study. Corneal biomechanics were evaluated using the Corvis ST and the BOSS. With the BOSS, each corneal image was acquired three times, measuring 10 locations within an 8-mm diameter. Parameters extracted included mean, maximum, and minimum Brillouin shift. These 10 points were also grouped into superior, central, and inferior regions. BOSS repeatability was assessed using the coefficient of repeatability and coefficient of variation. Furthermore, normal individuals and patients with keratoconus were compared using the Corvis ST and BOSS. The BOSS exhibited good repeatability, with coefficient of repeatability ranging from 0.098 to 0.138 GHz for single points in normal individuals and 0.096 to 0.149 GHz for patients with keratoconus. Statistical analysis revealed significant differences between normal individuals and patients with keratoconus, indicating softer corneas in keratoconus, observed with both the Corvis ST and BOSS. Specifically, the BOSS showed significant differences in mean, inferior, and superior mean, maximum, and minimum Brillouin frequency shift (all P < .05), whereas the Corvis ST displayed highly significant differences in stiffness parameter at first applanation, stress strain index, deformation amplitude ratio, and inverse integrated radius (all P < .001). Corneal biomechanical measurements proved highly repeatable and effectively demonstrated significant differences between normal individuals and patients with keratoconus using both the BOSS and the Corvis ST. [J Refract Surg. 2024;40(8):e569-e578.].

Innovative high degree of freedom single-multipoint incremental forming system for manufacturing curved thin-walled components

This study proposed a new design and control framework for a novel high degree of freedom single-multipoint incremental forming (HDoF-SMIF) system to manufacture curved thin-walled components. First, a novel HDoF-SMIF system was designed based on the principles of HDoF-SMIF technology (including the description of the mechanical structure and network topology). Following that, to realize the process control of the HDoF-SMIF process, this study introduced a novel control strategy for the tool deflection angle specific to robotic incremental forming. It also developed a synergistic motion control approach for the lifting platform and an accelerated computation method to determine the forming parameters for a multipoint reconfigurable die. Then, a novel HDoF-SMIF principle prototype and control program were built for the designed HDoF-SMIF system structure and control method. Finally, the feasibility of the HDoF-SMIF system was verified with the forming test on the domed component, and the geometrical accuracy and wall thickness distribution of the samples were measured using a 3D optical scanner system to evaluate the forming quality of the established HDoF-SMIF system. The results showed that compared to the conventional single-point incremental forming (SPIF) process, the developed HDoF-SMIF system can provide a more uniform thickness distribution of the formed part with a lower overall thickness thinning rate. Furthermore, by increasing the tool deflection angle with a 1 mm elastomeric interpolator, the overall part's forming accuracy and surface quality can be effectively improved.

An overview of the different digital facebow methods for transferring the maxillary cast into the virtual articulator.

The purposes of this study were to classify the described digital facebow techniques for transferring the maxillary cast into the semi-adjustable virtual articulator based on the digital data acquisition technology used and to review the reported accuracy values of the different digital facebow methods described. Digital data acquisition technologies, including digital photographs, facial scanners, cone beam computed tomography (CBCT) imaging, and jaw tracking systems, can be used to transfer the maxillary cast into the virtual articulator. The reported techniques are reviewed, as well as the reported accuracy values of the different digital facebow methods. Digital photographs can be used to transfer the maxillary cast into the virtual articulator using the true horizontal reference plane, but limited studies have assessed the accuracy of this method. Facial scanning and CBCT techniques can be used to transfer the maxillary cast into the virtual articulator, in which the most frequently selected references planes are the Frankfort horizontal, axis orbital, and true horizontal planes. Studies analyzing the accuracy of the maxillary cast transfer by using facial scanning and CBCT techniques are restricted. Lastly, optical jaw trackers can be selected for transferring the maxillary cast into the virtual articulator by using the axis orbital or true horizontal planes, yet the accuracy of these systems is unknown. Digital data acquisition technologies, including digital photographs, facial scanning methods, CBCTs, and optical jaw tracking systems, can be used to transfer the maxillary cast into the virtual articulator. Studies are needed to assess the accuracy of these digital data acquisition technologies for transferring the maxillary cast into the virtual articulator.

Feasibility Study of Scanning Spectral Imaging Based on a Birefringence Flat Plate.

Hyper-spectral imaging (HSI) systems can be divided into two main types as follows: a group of systems that includes a dedicated dispersion/filtering component whose role is to physically separate the different wavelengths and a group of systems that sample all wavelengths in parallel, so that the separation into wavelengths is performed by signal processing (interferometric method). There is a significant advantage to systems of the second type in terms of the integration time required to obtain a signal with a high signal-to-noise ratio since the signal-to-noise ratio of methods based on scanning interferometry (Windowing method) is better compared to methods based on dispersion. The current research deals with the feasibility study of a new concept for an HSI system that is based on scanning interferometry using the "push-broom" method. In this study, we investigated the viability of incorporating a simple birefringent plate into a scanning optical system. By exploiting the motion of the platform on which the system is mounted, we extracted the spectral information of the scanned region. This approach combines the benefits of scanning interferometry with the simplicity of the setup. According to the theory, a chirped cosine-shaped interferogram is obtained for each wavelength due to the nonlinear behavior of the optical path difference of light in the birefringent plate as a function of the angle. An algorithm converts the signal from a superposition of chirped cosine signals to a scaled interferogram such that Fourier transforming (FT) the interferogram retrieves the spectral information. This innovative idea can turn a simple monochrome camera into a hyperspectral camera by adding a relief lens and a birefringent plate.

The applicability of a commercial 3DO body scanner in measuring body composition in Chinese adults with overweight and obesity: a secondary analysis based on a weight-loss clinical trial.

A commercial three-dimensional optical (3DO) scanning system was reported to be used in body composition assessment. However, the applicability in Chinese adults has yet to be well-studied. This secondary analysis was based on a 16-week weight-loss clinical trial with an optional extension to 24 weeks. Waist and hip circumference and body composition were measured by 3DO scanning at each follow-up visit during the study. Bioelectrical impedance analysis (BIA) was also performed to confirm the reliability of 3DO scanning at each visit. We used Lin's concordance correlation coefficients (CCC) to evaluate the correlation between the two methods above-mentioned. Bland-Altman analysis was also performed to evaluate the agreement and potential bias between different methods. A total number of 70 Chinese adults overweight and obese (23 men and 47 women, aged 31.8 ± 5.8 years) were included in the analysis, which resulted in 350 3DO scans and corresponding 350 BIA measurements. The percent body fat, fat mass, and fat-free mass were 33.9 ± 5.4%, 26.7 ± 4.6 kg, and 50.3 ± 8.7 kg before the trial by 3DO scanning. And they were 30.5 ± 5.8%, 22.5 ± 4.7 kg, and 49.4 ± 8.3 kg after 16 weeks of the trial. Compared with BIA, 3DO scanning performed best in the assessment of fat-free mass (CCC = 0.89, 95%CI: 0.86, 0.90), then followed by fat mass (CCC = 0.76, 95%CI: 0.71, 0.80) and percent body fat (CCC = 0.70, 95%CI: 0.64, 0.75). Subgroup analysis showed that 3DO scanning and BIA correlated better in women than that in men, and correlated better in measuring fat-free mass in participants with larger body weight (BMI ≥28.0 kg/m2) than those with smaller body weight (<28.0 kg/m2). 3DO scanning is an effective technology to monitor changes in body composition in Chinese adults overweight and obese. However its accuracy and reliability in different ethnicities needs further exploration.

An Iterative High-Precision Algorithm for Multi-Beam Array Stitching Method Based on Scanning Hartmann

The multi-beam array stitching test system (MASTS) based on the Hartmann principle is employed to measure the aberrations in large-aperture optical systems. As each small-aperture and ideal parallel beam traverses the optical system, it is converged into a spot at the focal plane of the optical system. The centroid position of the spot contains the information about the wavefront slope of the sub-aperture at that specific location in the optical system. Scanning the optical system with this small-aperture beam across the entire aperture of the optical system, we can yield the aberration information to be tested. To mitigate pointing errors induced by scanning motion and accurately obtain the aberration signals of the optical system, nine beams are integrated into a 3 × 3 multi-beam array system, and their directions are aligned to be identical. However, achieving complete alignment in the same direction for all nine beams is a challenging task, resulting in errors due to their pointing differences within the array. This paper introduces an iterative algorithm designed to obtain high-precision multi-beam pointing errors and to reconstruct the wavefront of the optical system under test. This enables a more accurate measurement of wavefront aberrations in the optical system to be tested. Firstly, simulation models were implemented to validate the algorithm’s feasibility. Additionally, a scanning optical measurement system with a multi-beam array was developed in our lab, and the iterative algorithm was applied to process our experimental data. The results were then compared with interferometer data, demonstrating that our algorithm is feasible for MASTS to measure aberrations in large-aperture optical systems with high accuracy.

Polarization modulation scanning optical microscopy method

Since the discovery of monolayer graphene, the novel physical properties of two-dimensional (2D) materials, particularly those with fewer layers that often exhibit unique properties different from bulk materials, have received significant attention. Therefore, accurately determining the layer number or obtaining the microscopic surface morphology is crucial in the laboratory fabrication and during device manufacturing. However, traditional detection methods have numerous drawbacks. There is an urgent need for a convenient, accurate, and non-destructive scientific method to characterize the layer number and surface microstructure of 2D materials. By combining the experimental setup of laser scanning photocurrent spectroscopy, we develop a polarization-modulated scanning optical microscope based on the principle of reflectance difference spectroscopy. By monitoring the reflectivity of the samples, we can observe changes in the reflection signal strength of MoS&lt;sub&gt;2&lt;/sub&gt; with different layer numbers. The intensity of the reflectance differential spectral signal reflects changes in the layer count within the sample. We can characterize the changes in the number of layers of 2D materials in a non-contact manner by using polarization-modulated scanning optical microscopy. Through the study of the reflectance differential spectra of two typical 2D layered materials, MoS&lt;sub&gt;2&lt;/sub&gt; and ReSe&lt;sub&gt;2&lt;/sub&gt;, we find that our polarization-modulated scanning optical microscope system is also more sensitive to the characteristics of the stacking anisotropy of the 2D materials than the conventional reflection microscope. This indicates that our research contributes to a better understanding of the layer number characteristics and anisotropic properties of layered 2D materials. Furthermore, our research also provides a non-contact optical method to characterize the number of layers and optical anisotropy of two-dimensional layered material.

Design of Bessel Beam Scanning Optical System for Laser Beam Machining

Design of Bessel Beam Scanning Optical System for Laser Beam Machining

Relating metric crown dimensions to underlying internal daily secretion rates in antimeric premolars

ObjectivesThe underlying cause for metric differences in antimeric tooth pairs is an important question for understanding dental variation. We hypothesize that localized variation in crown dimensions will be reflected in localized variation in daily enamel secretion rate. DesignCasts of pairs of human premolars from a tissue bank were 3D scanned using an optical scanning system (n = 32). Histological slides were created, and daily secretion rates (DSRs) were recorded in two areas of enamel that corresponded to scanner measurements. Antimeres were compared for both metric measurements and DSRs. Outliers for scanner measures were compared to significant differences in DSRs measurements in right and left teeth in corresponding areas. ResultsThirteen of the 16 individuals differed significantly in antimeric metric measurements, but only ten of those also differed in the underlying DSR. Fifteen of the 16 total individuals differed significantly in at least one DSR area. DiscussionWhile some individuals were outliers for metric measurements and had multiple areas of DSR differences, the majority of individuals had antimeric DSR differences regardless of metric differences. While there was no conclusive correlation between 3D metric analysis and underlying DSR differences, the most important result of this study is that DSR differences between antimeres are common.

Application of optical scanning systems and 3D modeling algorithms as a method to control the depth of teeth preparation for fixed orthopedic structures

Background. In orthopedic dentistry at the present stage of its development, a chemical technique for preparing teeth for fixed structures of dentures has been developed; however, the state of the pulp in response to preparation is not taken into account. As a result, medical tactics for preserving or extirpating the pulp of abutment teeth, depending on the clinical case, are unreasonable. Given the generally accepted rules for preparing teeth for fixed orthopedic structures, there is a significant percentage of complications. Controlling the depth of tooth preparation makes it possible to carry out this manipulation as rationally as possible, and as a result to ensure the effectiveness of procedure, based on the state of vitality of the prepared teeth. The aim of the study is to determine and control the depth of the studied teeth preparation using digital volumetric scanning technology and algorithms of a digital graphic 3D editor in the CAD/CAM system. Materials and methods. The article presents the results of using digital volumetric scanning of the CAD/CAM system and an integrated algorithm for digital 3D modeling to determine and control the depth of teeth preparation for fixed orthopedic structures. Results. Based on the results of digital volumetric scanning, the working thickness of the tooth preparation in the area of the tooth neck was determined with the formation of various types of chamfer in different study groups. In order to determine the depth of the preparation of hard dental tissues, an artificial crown was modeled in the CAD system — digital volumetric scanner NeWay (Open Technologies) and data on its thickness in the area of the ledge were obtained. Conclusions. Method of digital volumetric scanning to determine and control the depth of preparation of hard dental tissues makes it possible to prevent the development of irreversible morpho-functional changes in the tissues of teeth caused by odontoreparation.

Minimal Required Resolution to Capture the 3D Shape of the Human Back-A Practical Approach.

Adolescent idiopathic scoliosis (AIS) is a prevalent musculoskeletal disorder that causes abnormal spinal deformities. The early screening of children and adolescents is crucial to identify and prevent the further progression of AIS. In clinical examinations, scoliometers are often used to noninvasively estimate the primary Cobb angle, and optical 3D scanning systems have also emerged as alternative noninvasive approaches for this purpose. The recent advances in low-cost 3D scanners have led to their use in several studies to estimate the primary Cobb angle or even internal spinal alignment. However, none of these studies demonstrate whether such a low-cost scanner satisfies the minimal requirements for capturing the relevant deformities of the human back. To practically quantify the minimal required spatial resolution and camera resolution to capture the geometry and shape of the deformities of the human back, we used multiple 3D scanning methodologies and systems. The results from an evaluation of 30 captures of AIS patients and 76 captures of healthy subjects showed that the minimal required spatial resolution is between 2 mm and 5 mm, depending on the chosen error tolerance. Therefore, a minimal camera resolution of 640 × 480 pixels is recommended for use in future studies.

Development of an optical coherence tomographic surface profiling system with a wide scanning area based on telecentric F–θ imaging optics

This study was conducted to develop an in situ tomographic profiling system that can detect surface defects over a wide area by applying a telecentric F–θ scanning optical system, with an effective measurement width of 200 mm, to a spectral domain optical coherence tomography (SD-OCT) system. A telecentric F–θ scanning optical system with an effective scanning length of up to 210 mm was designed. A focal depth up to 32 mm without loss of resolution was predicted when the entrance pupil diameter (EPD) was set to 4.0 mm. The obtained three-dimensional tomographic images of tire treads and scientific calculators confirmed the possibility of surface profiling for areas with a width of up to 200 mm and depth over 7 mm. Combining a large-area telecentric lens with an SD-OCT system made it possible to perform deep 3D profiling simultaneously with a large-area surface inspection. The developed surface tomographic profiling system can adjust the size of the EPD to achieve a resolution of less than 50 µm. It can thus provide axial and lateral resolutions equivalent to those of a conventional OCT system as well as a wide effective measurement area.

Single-photon splitting by polymeric submicropillars structures

Optical splitters are one of the most important interconnects in the optical chips of future optical quantum computers. Here, we introduce novel quantum photonic splitters based on polymeric submicropillars that split the single-photon signal generated by a colloidal quantum dot (QD) into multiple outputs, which can be easily accessed through a conventional confocal scanning optical system. Using a single continuous-wave laser with a low absorption wavelength for both polymer material and QDs, we were able to first deterministically place a single-photon emitter (SPE) within one of the submicropillars and then characterize the single-photon guiding effect of the fabricated structures. The submicropillars, with their size and position which are comprehensively optimized by numerical simulations, act as single-mode directional coupler guiding both the laser excitation and the single-photon emission thanks to the evanescent wave coupling effect. With one-step fabrication, we can create a well-distributed array of “imaginary” SPEs from an original SPE. Our method opens various applications in integrated devices based on solid-state quantum emitters.

Experimental and numerical study on the microstructure and chloride ion transport behavior of concrete-to-concrete interface

Concrete-to-concrete interfaces present both in new and existing construction, are commonly regarded as the weak link. Durability research of interfaces is a vital prerequisite for structural rehabilitation and strengthening applications under marine and coastal environments. Hence, to clarify the chloride ion transport behavior between the new-old concrete composite system and its constituents, microstructural characteristics of the interfaces with various preparation methods were determined via field emission scanning electron microscopy. Then, the time-dependent diffusion chloride ion penetration together with its steady-state concentration distribution evaluated by using AgNO3 chromogenic, electron microprobe, and energy spectrum methods, as well as the numerical simulation based on the real interface roughness from the 3D laser scanning optical system. Results show that microcracks and a large amount of CaCO3 precipitations were formed in the concrete-to-concrete interface, where its porosity was higher compared to that of the matrix and interface transition zone around coarse aggregate; Therefore, the interface regions have higher tortuosity of water transport channel and strengthen the solution absorption rate, resulting in the internal chloride ions not only diffuse deeper perpendicular to the exposed surface but also ingress into the concrete on both sides as the concentration gradient simultaneously, leading to a “diffusion peak” formation. Furthermore, the effects of groove characteristics (such as orientations, clearance, width, and depth) on chloride transport were modeling evaluated in this study, in which the interfacial relationship could be optimized setting the reasonable groove and achieving the goal of durability equivalent to the cast-in-place structure.

Performance Analysis of Scanning Optical System with Microlens Array Based on Fill Factor

Performance Analysis of Scanning Optical System with Microlens Array Based on Fill Factor

Dynamic temperature-strain discrimination using a hybrid distributed fiber sensor based on Brillouin and Rayleigh scattering.

We present a distributed fiber sensor capable of discriminating between temperature and strain while performing low-noise, dynamic measurements. This was achieved by leveraging recent advances in Brillouin and Rayleigh based fiber sensors. In particular, we designed a hybrid sensor that combines a slope-assisted Brillouin optical time domain analysis system with a Rayleigh-scattering-based frequency scanning optical time domain reflectometry system. These sub-systems combine state-of-the-art sensitivity with the ability to perform both dynamic and quasi-static measurements. This enabled a hybrid system capable of temperature/strain discrimination with a quasi-static temperature resolution of 16 m°C and a strain resolution of 140 nɛ along 500 m of single mode fiber with 5 m spatial resolution. In contrast to previously reported techniques, this approach also enabled dynamic measurements with a bandwidth of 1.7 kHz and temperature (strain) noise spectral density of 0.54 m°C/√Hz (4.5 nɛ/√Hz) while temperature/strain cross-sensitivity was suppressed by at least 25 dB. This represents a dramatic improvement in measurement speed and sensitivity compared with existing techniques capable of temperature/strain discrimination in standard single mode fiber.

A MEMS-Based Optical Scanning System for Precise, High-Speed Neural Interfacing

Optical scanning is a prevalent technique for optical neural interfaces where light delivery with high spatial and temporal precisions is desired. However, due to the sequential nature of point-scanning techniques, the settling time of optical modulators is a major bottleneck for throughput and limits random access targeting capabilities. While fast lateral scanners exist, commercially available varifocal elements are constrained to 3-ms settling times, limiting the speed of the overall system to hundreds of hertz. Faster focusing methods exist but cannot combine fast operation and dwelling capability with electrical and optical efficiency. Here, we present a varifocal mirror comprised of an array of piston-motion micro-electromechanical systems (MEMS) micromirrors and a custom driver application specific integrated circuit (ASIC), offering fast operation with dwelling capability while maintaining high diffraction efficiency. The ASIC features a reconfigurable nonlinear digital-to-analog converter (DAC) to simultaneously compensate for the built-in nonlinearity of electrostatic actuators and the global process variations in MEMS mirrors. Experimental results demonstrate a wide continuous sweeping range that spans 22 distinctly resolvable depth planes with refresh rates greater than 12 kHz.

Calcaneofibular ligament may act as a tensioner of peroneal tendons as revealed by a contactless three-dimensional scan system on cadavers

The ligaments are believed to have a role in stabilizing joints and regulating joint motion. Here, we propose a novel function of the calcaneofibular ligament (CFL), which stabilizes the ankle joint. In human bipedal locomotion, the peroneal muscles maintain mediolateral stability and prevent involuntary ankle inversion. To investigate the functional relationship between the peroneal longus tendon (PLT), brevis tendon (PBT), and CFL, we quantitatively analyzed the positional changes of the tendons by using a contactless three-dimensional optical scan system. Eighteen cadaveric specimens were included in the study. Interestingly, with increased tension of the CFL, the tendons significantly moved toward the lateral direction (P < 0.001), compared with their position when the CFL was detached. The actual lift amount reached 2.0 ± 0.8 mm for the PLT and 1.9 ± 1.0 mm for the PBT. These results strongly suggest that a tensed CFL can lift the peroneal tendons and may act as a “tensioner” for the effective transmission of muscle contraction. This phenomenon contributes to postural control, especially in regaining balance on uneven terrain, and provides a new perspective for the exercise methods or understanding the ankle joint instability due to sprains.

Simulation and compensation of thermal lensing in optical systems.

High-power optical systems are used in a number of industrial applications. One difficulty in designing such systems is that the beam itself is a significant source of heat, which changes the optical properties of the system. To reduce this effect, we propose a new thermal lensing compensation technique based on a detailed analysis of the optical properties of the high-power optical system. To this end, we have developed a new ray tracing simulation technique that accurately models optical propagation through inhomogeneous, anisotropic, and deformed media. This model enables the performance of systems in physically realistic situations to be evaluated efficiently. Experimental comparisons were conducted to validate the simulation. We found excellent agreement between the simulation and the measured data. We have validated the simulation technique for a single lens setup and a complex optical scanner system.

Tensile mechanical properties and AE characteristics of shale in triaxial Brazilian splitting tests

Under the high temperature and high stress geological environment, how the physical and mechanical properties of deep shale reservoirs will change has become a hot research issue. Based on the Confined Brazilian Test, this paper improves a test method for the tensile strength of shale under triaxial conditions with a simple specimen fixture and convenient specimen preparation and performs a high confining pressure (0–60 MPa) Brazilian splitting test on Longmaxi Formation shales. The stress-displacement curve records the deformation and failure of shale. Acoustic emission technology (AET) detects the evolution process of fractures and further identifies failure modes. 3D optical scanning system reconstructs the fracture morphology. The results show that the maximum tensile strength of the shale specimens in the triaxial condition is increased by 58.5% relative to direct tensile strength. As the confining pressure gradually increases to 60 MPa, the specimen enters the stress state of compressed in three directions, the tensile failure mode gradually transitions to shear failure mode via tensile-shear composite failure mode, and the fracture angle gradually increases. The AE signal in triaxial conditions mainly shows a leap trend. The appearance of AE signal with high peak frequency can be used as a reference for micro-fracture initiation. The presence of shear fractures increases the roughness of the shale main fracture surface, and this effect diminishes as the confining pressure increases. This study can provide a reliable theoretical basis for the optimal design of hydraulic fracturing in deep shale gas reservoirs.