Sag Height Research Articles

An integrative predictive model for orthokeratology lens decentration based on diverse metrics.

To develop a predictive model for orthokeratology (Ortho-K) lens decentration 1 month after wear. This study included myopic children who were fitted with Ortho-K lenses at Fujian Provincial Hospital between December 2022 and May 2024. Corneal topography parameters and other relevant metrics were collected pre- and post-treatment. Feature selection was conducted using univariate logistic regression and Lasso regression analysis. A machine learning approach was used to develop multiple predictive models, including Decision Tree, Logistic Regression, Multilayer Perceptron, Random Forest, and Support Vector Machine. Model performance was evaluated using accuracy, sensitivity, specificity, ROC curves, DCA curves, and calibration curves. SHAP values were employed to interpret the models. The Logistic Regression model demonstrated the best predictive performance, with an AUC of 0.82 (95% CI: 0.69-0.95), accuracy of 77.59%, sensitivity of 85%, and specificity of 61.11%. The most significant predictors identified were age, 8 mm sag height difference, 5 mm Kx1, and 7 mm Kx2. SHAP analysis confirmed the importance of these features, particularly the 8 mm sag height difference. The Logistic Regression model successfully predicted the risk of Ortho-K lens decentration using key corneal morphological metrics and age. This model provides valuable support for clinicians in optimizing Ortho-K lens fitting strategies, potentially reducing the risk of adverse outcomes and improving the quality of vision for patients. Further validation in clinical settings is recommended.

Surface roughness prediction model and surface topography analysis of 2.5D-Cf/SiC in two-dimensional ultrasonic assisted grinding based on GA-BP neural network

Because of the anisotropy and non-uniformity, the grinding surface quality of Cf/SiC composites is difficult to be accurately predicted. The quality of the surface directly determines the assembly accuracy. To better predict the surface quality of 2.5D-Cf/SiC composites, the BP neural network was optimized by genetic algorithm (GA), and the surface roughness prediction model of fiber orientation, ultrasonic amplitude, and machining parameters was established. The empirical formula prediction model of surface roughness was established by the method of multiple linear regression analysis. The results show that the prediction accuracy of GA optimized BP neural network is the best, followed by the empirical formula, and the prediction effect of the BP neural network is the worst. The average absolute percentage error of these three models is 10.045%, 16.912% and 26.6245% respectively. The kinematic models of conventional and two-dimensional ultrasonic-assisted grinding of single particles were established respectively. Based on the kinematic model, the reasons for the reduction of surface roughness by 2D ultrasonic-assisted grinding are explained. According to the orthogonal test results, the surface roughness decreases the most when vs is 0.66m/s, vw is 100mm/min, ap is 150μm along the fiber orientation of 0°, and the maximum percentage of reduction is 53.18%. Increasing the linear speed, reducing the feed speed, reducing the grinding depth, and applying ultrasound can reduce the extrusion pressure along the axis of 0° fiber, and then reduce the length and depth of cracks and thus reduce the surface defects. The axial shear force of the 90° oriented abrasive particles on the fiber is reduced, thus reducing the surface damage caused by torsional deformation. Reduce 3D surface profile and improve surface quality. The maximum percentage reduction of each parameter index is as follows: root mean square height decreased by 28.8%, skew decreased by 88.61%, kurtosis decreased by 48.97%, maximum crest height decreased by 48.55%, maximum sag height decreased by 40.09%, maximum height decreased by 43.93%, and arithmetic mean height decreased by 26.06%.

Optimization of Cabin Virus Transmission Suppression Technology Based on Hanging Curtain Physical Isolation

This study presents an innovative physical isolation measure for commercial scenarios, namely, hanging curtains, to prevent the spread of respiratory infections. Using computational fluid dynamics simulation techniques, the closed spaces within cruise cabins were modeled and numerically analyzed, focusing on the dispersion characteristics of droplets. Additionally, orthogonal methods were employed to investigate various arrangements of hanging curtains and their effects on droplet dispersion based on spatial positioning. The research findings indicated that hanging curtains can effectively alter the airflow within a space, realizing the innovative concept of localized pollutant containment. It was found that the spatial partitioning method based on the location of individuals contributes more to reducing droplet dispersion than other methods. Moreover, the sag height of curtains emerges as the most influential factor on individual infection risk, while the scheme for hanging curtain positions has the least impact. Finally, the optimal configuration recommendation is provided: a curtain bottom coordinate of Z = 2.3 m and a top coordinate of Z = 2.8 m when the infection source was positioned at the center of the space. This configuration has also been validated by varying the location of the infection source. The research findings provide valuable insights for formulating preventive measures for passengers on cruise ships and for pandemic control in similar scenarios.

Wettability and Frictional Studies of PEEK Composites against Co-Cr Alloys with Surface Textures.

With the aim of promoting the qualities for total hip joint replacement, the wettability and tribological behaviors of PEEK composites pins with two sets of different fillers (PEEK/CF or PEEK/CF/PTFE/graphite) against Co-Cr alloy discs with five categories of surface textures (polished, orthogonal, spiral, r-θ, and orthogonal combined with spiral) were explored. It is revealed that the existence of CF in PEEK matrix increases the hydrophilicity in addition to the strength of PEEK, while the addition of PTFE increases the hydrophobicity of PEEK. The Co-Cr alloy discs with hydrophilic properties can be adjusted as hydrophobic, with the depth of textured grooves exceeding the critical sag height determined by the contact angle and the groove width. It can be concluded that PEEK/CF/PTFE/graphite composite has a lower wear rate than PEEK only reinforced with CF against Co-Cr alloy, both without surface texture and with shallow or deep grooves. The existence of shallow grooves on the disc surface could help the PEEK blends to achieve a steady friction against Co-Cr alloy in addition to collecting the worn debris. PEEK blend pins with 10 vol% CF, 10 vol% PTFE and 10 vol% graphite can achieve a lower friction coefficient of no more than 0.2 against Co-Cr alloy discs with shallow grooves around 3.5 μm in orthogonal or spiral textures.

Random spherical microlens array fabricated by elliptical vibration diamond cutting and molding.

Microlens arrays (MLAs) are widely used in homogenized laser beams due to excellent optical properties. However, the interference effect generated in traditional MLA (tMLA) homogenization will reduce the quality of the homogenized spot. Hence, the random MLA (rMLA) was proposed to reduce the interference effect in the homogenization process. To achieve mass production of these high-quality optical homogenization components, the rMLA with randomness in both period and sag height was proposed first. Subsequently, MLA molds were ultra-precision machined on S316 molding steel by elliptical vibration diamond cutting. Furthermore, the rMLA components were precisely fabricated by applying molding technology. Finally, Zemax simulation and homogenization experiments were carried out to verify the advantage of the designed rMLA.

A design analysis method and its application in the cover arch of cut-and-cover tunnels

It is very important to improve the design of supports because the cut and cover method of layered backfill after construction is the primary method used to construct shallow buried sections of mountain tunnels. The Dujuan Valley Tunnel in Fenghua City is the subject of this research. First, a geometric model of a shallow buried section of a mountain tunnel and its construction parameters were used to develop the simplified bearing capacity analysis model for the covered arch. Second, a simplified method to calculate the internal force of the cover arch supporting structure was established by using the method of structural mechanics. Thus, a method was established to determine the safe thickness of the cover arch and to analyze the bearing capacity and stability of the enlarged foundation of the arch foot. Third, the influence of the tunnel burial depth, cap arch sag height, central angle, radius and arch foot width on the bearing characteristics of the cover arch support structure was discussed, and the optimal design principle of excavation in shallow buried sections of mountain tunnels was obtained. Finally, the calculation and evaluation of the design in an example case were used to determine the rationality of the method to design and optimize shallow buried sections of mountain tunnels with the cut and cover method.

Rapid fabrication of highly integrated and high numerical aperture chalcogenide glass microlens arrays

The fast growing of infrared imaging system for non-contact thermography, night surveillance and night driving assistance demands highly integrated optical lenses with miniaturization feature for performance improvement. Herein, we fabricated refractive type of microlens arrays (MLAs) with high numerical aperture (NA) and high integration on commercial chalcogenide glass (As2Se3) by combining photoresist thermal reflow and soft mold imprinting process. PDMS-type concave MLAs (PDMS-MLAs) soft mold is prepared by transfer printing process on photoresist (PR) MLAs fabricated by standard UV exposure and thermal reflow. The microlens on PDMS-MLAs could be further transferred to the surface of As2Se3 glass through the hot imprinting technique, forming chalcogenide glass-based MLAs (ChG-MLAs). Morphology detection reveals that microlens in the MLAs has an average aperture and sag height of approximately 13.4 and 1.7 μm. Moreover, the optical performance investigation demonstrated that the ChG-MLAs with 700 × 700 array size (10.5 × 10.5 mm) showed good structure uniformity and focusing capability, and through the FDTD simulation, it further evidenced that focal lengths of 6.3–8.1 µm with high numerical aperture of 0.64–0.73 (wavelength range: 3–5 μm) was achieved.

Chalcogenide Glass IR Artificial Compound Eyes Based on Femtosecond Laser Microfabrication

AbstractThe compact and lightweight infrared (IR) optics devices are highly demanded in booming applications. However, fabrication of IR optics devices with high efficiency is still technically challenging, especially artificial compound eyes (ACE) with low aberration imaging and large field of view. In this work, a method of femtosecond laser wet etching combining with the “two‐step” precision glass molding based on chalcogenide glass is proposed to fabricate glass IR ACE. The as‐prepared consists of 6000 ommatidia (diameter of 88 µm and the sag height of 11 µm) arranged in a hexagonal manner with perfect parabolic morphology and high uniformity. The chalcogenide glass IR ACE exhibits excellent optical performance both in IR active imaging and IR passive imaging with high transmittance (60–70%) ranging from 2.5 to 15 µm. The ommatidia have a high resolution up to 20.16 lp mm−1, and imaging with large field of view up to 60° and low aberration can be achieved. Furthermore, the proposed technology shows advantages to fabricate glass IR ACE with low cost and high efficiency, and glass IR ACE shows great potential in IR imaging, robot vision, IR 3D motion tracking, and so on.

Parametric study of microlens array fabricated on polymer substrate through hot embossing with a micro-EDM mould and its optical characterisation

ABSTRACTThe surface topography of embossed micro-patterns relies on hot embossing (HE) parameters and micro-patterns over the mould. Traditionally, moulds were made using photolithography (X-ray/UV/E-beam) followed by wet etching or reactive ion etching. This technique is costlier, time-consuming, and expensive. To resolve these issues, researchers are shifting to micromachining to make HE moulds. In this investigation, a mould fabricated by μ-electric discharge machining (μ-EDM) was employed in an in-house developed HE set-up. In this work, embossing temperature (Te), embossing pressure (Pe), embossing time (te), and deembossing temperature (Tde) were used as operational factors and their influence on micro (μ)-lens surface profile was evaluated. Te, Pe, and te increases the sag height (hsag) of μ-lens array. As hsag increases, radius-of-curvature (R) and focal length (f) of the embossed μ-lens array decrease, which enables the production of μ-lenses with different diameters by modifying HE parameters. The maximum percentile change in hsag is 292.49% with Te. The maximum percentile drop in calculated R and f values were observed in case of Tde, i.e. 70.89% followed by Pe (54.18%) and te (49.52%). Hemispherical shaped μ-lens array was obtained at Te of 140°C, Pe of 50 kg/cm2, te of 20 min, and Tde of 40°C.

Fabrication of Microlens Arrays with High Quality and High Fill Factor by Inkjet Printing

AbstractMicrolens arrays (MLAs) have a variety of applications in, e.g., display systems, projection optics, and sensors. They can be manufactured by various fabrication methods. Among all, inkjet printing stands out because it offers a straightforward, versatile, and low‐cost fabrication route. However, extra manufacturing steps such as photolithography are so far involved to pre‐structure the substrate in order to improve the uniformity of the printed MLAs and achieve a high fill factor (FF). In this study, the fabrication of MLAs is reported on unstructured substrates by inkjet printing using an optimized UV‐curable ink on top of self‐assembled monolayers (SAMs). The latter allows for tuning the surface free energy and thus the aspect ratio of the microlenses. The high uniformity of the printed MLAs is demonstrated by the automatic quantitative evaluations, where the standard deviations of the radii are below 2.5% and of the sag heights are less than 3.9%. An unprecedented FF of 88% amongst all inkjet‐printed MLAs on unstructured substrates is achieved. Digitally controlled large area fabrication is demonstrated, both, on rigid as well as on flexible substrates, opening a pathway for customized microoptics by additive manufacturing.

Microlens array through induction-aided hot embossing: fabrication, optimization, and characterization

ABSTRACT In the present work, an induction-aided hot embossing (IHE) setup was developed in-house, to reduce the time required for embossing. Using the setup, a micro-lens array was successfully fabricated over PMMA substrate using laser engraved mold in less than half the time required compared to traditional hot embossing. The operating parameters were optimized through composite desirability (CD) method and teaching learning-based optimization (TLBO) to enhance the replication accuracy of the embossed microlens array. IHE experiments were designed as per rotatable central composite design (R-CCD). Embossing temperature (Te), embossing pressure, embossing time, de-embossing temperature were selected as control parameters, and deviation in diameter of the embossed microlens array was chosen as performance factor. A first-order linear model was employed for mathematical modeling. ANOVA result reveals that the developed model is adequate and Te has an impact of 44.63% on the replication accuracy. It was observed that the deviation in diameter decreases from 27.12 μm to 23.63 μm as Te increases from 120ᵒC to 130ᵒC. Final optimization result reveals that TLBO performs better than the CD. Deviation in diameter predicted by TLBO method at optimum condition is 15.83 μm which closely matches the experimental findings at optimum condition, that is, 16.57 μm. Abbreviations HE: Hot embossing; PMMA: Polymethyl methacrylate; ROC: Radius of curvature; RSM: Response surface methodology; TLBO: Teaching learning-based optimization; CD: Composite desirability; ANOVA: Analysis of variance; To: room temperature; Tg: Glass transition temperature; Te: Embossing temperature; Pe: embossing pressure; te: embossing time; Tde: deembossing temperature; tc: Cycle time; μ: Micro; Ffrictional: Frictional force; RIE: Reactive ion etching; EDM: Electric discharge machining; : sag height; IP: Input; OP: Output; IHE: Induction-aided hot embossing; CHE: Conventional hot embossing; WEDM: Wire electric discharge machining

Development of Microlens Arrays With Large Focal Number and High Fill Factor for Wavefront Sensing Applications

Microlens arrays find many useful applications in sensing devices though their fabrication is challenging due to rigorous requirement of clean-room processing and equipments thereof. In this context, herein a method for fabrication of large focal number (F#) and high fill factor microlens arrays is presented. These microlens arrays have well-defined boundaries and can be used for wavefront sensing applications. This method of fabrication is robust and can be used for achieving hexagonal as well as square aperture and also it is well suited for mass production. The presence of chrome pedestals below the pillars of photoresist prevents the lenses from merging while reflow and leads to nice and well defined lens boundaries with high fill factor. Main advantage of this method is that it does not require the reactive ion etching and multiple layer lithography and thereby it can be a very inexpensive method of fabrication of large F# (>25) and high fill factor (>95%) microlens arrays. The fabricated microlens arrays have been quantitatively characterized for pitch, aperture size, sag height, surface profile, roughness and 2-D point spread function. Experiments have been carried out to validate these microlens arrays in wavefront sensing for optical metrology applications.

Ultradeep microaxicons in lithium niobate by focused Xe ion beam milling

Refractive axicons are conically shaped optical devices that are capable of generating nondiffracting Bessel-like beams over extended depths-of-focus (DOFs). In addition to the substantially longer DOF compared to those produced by parabolic focusing lenses, the axicons can generate beams with better resolution for the same form-factor of the optical element, e.g., its diameter and sag height. These properties make the axicons useful in numerous applications in imaging, particle trapping, and many others. Miniaturized refractive axicons or microaxicons are challenging to realize in hard substrates due to the lack of sufficiently precise and rapid fabrication technologies. Here, we report on the rapid fabrication of ultradeep microaxicons in lithium niobate using high-current focused Xe ion beam milling. Microaxicons with 230-μm diameter with ultradeep sag heights between 21 and 48 μm were milled using 200 nA of beam current. Furthermore, the microaxicons were milled in single-crystal lithium niobate—a material with a high refractive index of >2.2 but which inertness makes it a challenging material in microfabrication. The performance of the lenses was characterized by mapping the transmitted intensity at different positions. The measured spot sizes of the produced beams are in excellent agreement with the theoretical expectations and range from 750 down to 250 nm (∼λ/2) beam spot size for the shallowest and the deepest microaxicons in this study, respectively. The corresponding DOFs are from 500 down to ∼50 μm for the ultradeep microaxicon. The results verify the applicability of high-current milling with a focused Xe ion beam for the fabrication of high-performance optical elements.

Automated quality assessment of inkjet-printed microlens arrays

Abstract Recently, inkjet-printed microoptics, such as microlens arrays, have become popular in scientific research as well as industrial applications due to the fast prototyping and production. Naturally, the process parameters have a strong influence on the printed end results. However, optimization of these parameters requires expert knowledge and manual quality control which is subjective and error-prone. To overcome these limitations, we propose an automated evaluation pipeline utilizing both light and confocal microscope images as well as multiple quality measures to quantitatively evaluate the quality of the printed microlens arrays, including the individual microlens radii, sag heights, and focal lengths, as well as the array’s grid parameters.

Fabrication of microlenses with continuously variable numerical aperture through a temporally shaped femtosecond laser

We developed a novel method for fabricating microlenses and microlens arrays by controlling numerical aperture (NA) through temporally shaped femtosecond laser on fused silica. The modification area was controlled through the pulse delay of temporally shaped femtosecond laser. The final radius and sag height were obtained through subsequent hydrofluoric acid etching. Electron density was controlled by the temporally shaped femtosecond laser, and the maximum NA value (0.65) of a microlens was obtained in the relevant studies with femtosecond laser fabrication. Furthermore, the NA can be continuously adjusted from 0.1 to 0.65 by this method. Compared with the traditional methods, this method exhibited high flexibility and yielded microlenses with various NAs and microlens arrays to meet the different demands for microlens applications.

Tunable microlens array fabricated by a silicone oil-induced swelled polydimethylsiloxane (PDMS) membrane bonded to a micro-milled microfluidic chip.

Microlens arrays (MLAs) nowadays are critical micro-optical components and they can be applied in many application fields, such as optical communication systems and flat panel display modules. This article describes a novel approach to the fabrication of tunable, highly reliable, and uniform polydimethylsiloxane (PDMS) MLAs. A polydimethylsiloxane (PDMS) membrane is bonded to a micro-milled poly(methyl methacrylate) (PMMA) microfluidic chip and exposed to silicone oil of a specific viscosity. Molecules in the oil insert themselves into the molecular structure of the PDMS membrane, causing it to swell and subsequently form dome-shaped MLAs. From our experiments, we derived the following conclusions. First, the homogeneous swelling of the PDMS resulted in MLAs with a high numerical aperture (0.5), high uniformity illumination (CV of the illumination intensity is between 2.5%∼5.1%), and high uniformity (CV of sag height of MLAs is less than 0.05). Second, the shorter molecular chains in low-viscosity oils diffused more readily into the PDMS membrane, which increased the effects on swelling, resulting in MLAs with higher sag height and higher numerical aperture. For example, the 5 cst silicone oil resulted in sag height of 191 µm with NA of 0.50, whereas the 100 cst silicone oil resulted in sag height of 86 µm with numerical aperture of 0.33. Finally, the integrated mixer module enabled the simultaneous tuning of the 7 × 7 MLAs simply by adjusting the injection flow rates of the constituent silicone oils.

IR Artificial Compound Eye

AbstractIn this work, a 3D IR artificial compound eye (ACE) optical component is fabricated using thermoplastic IR polymer material. The femtosecond laser‐assisted wet etching and the 3D nano‐imprinting techniques are proposed for fabricating this thin shell multi‐aperture component. The prepared component is close‐packed with over 1000 high‐quality micro‐facet‐lenslets (ommatidia) on the semispherical thin shell dome with base radius of 2.7 mm and sag height of 2.1 mm, enabling enlarged field of view to 148°. The ommatidia with diameter of 150 µm and numerical aperture of 0.35 are demonstrated to have a practical spatial resolution up to 160 lp mm−1. IR imaging experiments (both in passive and active scenarios) confirm its outstanding optical properties and uniformity, and demonstrate the probability of thermal target imaging with such component in the near‐infrared band. The proposed fabrication strategy shows remarkable efficiency and advantage in massive replication, and such ACE component predicts its potential in emerging applications, such as IR imaging, target tracking, and so on.

Sag and Tension of 275 kV Transmission Line using Catenary

This research will develop a catenary method to determine the sag and tension analysis on the 275 kV transmission line conductors. The catenary method is dependent on the equation of the weight of the conductor, the maximum tensile stress of the conducting wire, the length of the span, and the maximum sag of the conductor. The method will be used in determining the value of sag and tension with the design of the model using software AutoCAD. The results of research for the same tower sag height of 6.86 m, with a tension of 4610.83 kg and a conductor length of 401.06 m, while sag for the tower is not the same height of 8.14 m, with a tension of 4612.84 kg, and changes in conductor length 401.06 m. The increase in current causes the sag value to increase, when the minimum current sag value is 6.9828 m, and the maximum current sag value increases to 8.44 m. While the tension will decrease along so that temperature is increased the current minimum pressure of 4531.27kg, and at the time of maximum tension of 3749.728kg. Sag and tension are also affected by ambient temperature when the minimum temperature is 20 ℃ sags are 6.8621 m and when the maximum temperature is 40 ℃ sag increases to 7.793492 m. Tension will decrease with each increase in temperature when the minimum temperature is 20 ℃ tension 4610.538 kg when the maximum temperature is 40 ℃ the tension is reduced to 4062.345 kg.

Finite Element Analysis of PGM Process for Wafer Based Lens Array

In order to study the PGM process for wafer based lens array, we established a 3D finite element model of glass wafer with lens array by using the submodel technique in ABAQUS. Then assessment criteria of the molded lens and influence of different PGM process parameters were investigated thoroughly. The obtained results show that during the molding stage, proper molding pressure can help the lens fill better and decrease the sag height deviation significantly. While during the annealing stage, holding pressure is essential for keeping the molded lens’ structure and position, but residual stress must be considered at the same time.

Modelling and Structural Design for Parallel Umbrella-Shaped Cable-Strut Structures Based on Stationary Potential Energy Principles

A method for the modelling and structural design of a parallel umbrella-shaped cable-strut structure (PUSC) is presented. First, simplified calculation models of a PUSC are built. Next, based on the principle of stationary potential energy, the relationships among the cable sectional areas, prestress forces, vector height, sag height, overall displacement, and local deformation are proposed. Then, the static responses of the PUSC under vertical loads and wind loads are put forward. Finally, a calculation model of a 100 m-span PUSC is developed and optimized to verify the feasibility of the proposed method. The results show that when the combinations of the loading, variation ranges of the vector height and sag height, and material properties of the components are given, the sectional areas of the cables, dimensions of the inner strut, and prestress forces of these components can be obtained. A greater external load requires a corresponding increase in vector height and sag height to increase the overall stiffness, leading to larger sectional dimensions of the components and a greater prestress of the entire structure. Therefore, the total weight of the cables and inner struts are determined. Moreover, because the weight of the cables decreases and the weight of the inner struts increases as the vector height and sag height increase, the total weight of the cables and struts decreases sharply during the initial stage, decreases gradually during the second stage, and increases slowly during the last stage after reaching the minimum value. For the optimal design of the calculation model, using the vector height and sag height as design variables provides an adequate geometric stiffness and a suitable prestress for the PUSC to fulfill the requirements of all the loading combinations.