Traditional Lens Research Articles

Design of an optimized Alvarez lens based on the fifth-order polynomial combination

This paper proposes an optimized design of the Alvarez lens by utilizing a combination of three fifth-order X-Y polynomials. It can effectively minimize the curvature of the lens surface to meet the manufacturing requirements. The phase modulation function and aberration of the proposed lens are evaluated by using first-order optical analysis. Simulations compare the proposed lens with the traditional Alvarez lens in terms of surface curvature, zoom capability, and imaging quality. The results demonstrate the exceptional performance of the proposed lens, achieving a remarkable 26.36% reduction in the maximum curvature of the Alvarez lens (with a coefficient A value of 4×10−4 and a diameter of 26 mm) while preserving its original zoom capability and imaging quality.

Enhancing Tandem Solar Cell's efficiency through convolutional neural network-based optimization of metasurfaces

Tandem Solar cells are composed of multiple layers with varying bandgap materials to facilitate the absorption of a wider range of solar energy. However, their performance is hampered by interface losses leading to current mismatching. To overcome these limitations, tandem solar cells often require the use of mirrors and lenses to concentrate and trap light to achieve optimal efficiency. Recently, the use of nanoscale 2D meta-materials has emerged as a promising alternative to traditional lenses. However, the optical optimization of these meta-materials can be both time-consuming, resources, and space-intensive, posing a challenge to their implementation. This study explores the use of deep learning to predict the optimal optical design for the top cell in tandem solar cells to maximize power conversion efficiency. Computational techniques are used to analyze the optical responses of metasurfaces. 2D-Convolutional Neural Networks (CNN) are used to train a dataset of 10,578 TiO2/CH3NH3PBr3/ZnO metasurfaces. Nine different CNN models were used with different architectures to identify the best hyperparameters that give the low mean square error. CNN displayed fast high prediction accuracy taking an average of 0.3 ± 0.05 seconds per prediction. The Deep SHapley Additive Explanations (SHAP) algorithm was used to gain insights into CNN's predictions and understand the behavior of complex metasurfaces integrated into a typical reference tandem solar cell architecture. The proposed metasurfaces can significantly enhance the efficiency of tandem solar cells. The active layer comprises of near 90% absorption of the solar spectrum. The average absorption of the top cell increased in the UV-vis region (650-800nm) up to 93.4%.

Evolution of Scleral Fixation, Haptic Externalization and Tucking Techniques

Phakic rehabilitation poses challenges for patients without capsular support, making traditional intraocular lens (IOL) implantation difficult. In such cases, an Anterior Chamber (AC) IOL or a scleral-fixated posterior chamber IOL (SF-PC IOL) can be considered as options. To ensure a well-centered IOL, haptics should be away from the ciliary processes, iris, and oraserrata, with sufficient distance from the iris to prevent capture. Delayed IOL dislocation can occur due to suture breakage, but it can be prevented by proper IOL size and snugly opposing the stitched haptics into the ciliary sulcus.

Mechanical Characterization of Broadband Achromatic Optical Vortex Metalens

Metalenses, which may effectively manipulate the wavefront of incident light, have been proposed and extensively utilized in the development of various planar optical devices for specialized purposes. However, similar to traditional lenses, the metalens suffers from chromatic aberration problems due to the significant phase dispersion in each unit structure and the limited operational bandwidth. To mitigate the impact of chromatic aberration, we integrate a phase compensation approach with a novel utilization of a phase shift function to define the adjusted phase criterion satisfied by each α-Si resonance unit. This approach may lead to development of an innovative optical tweezer known as an achromatic optical vortex metalens (AOVM), offering reliable focusing capabilities across the 1300 nm and 1600 nm incident light range. Numerical simulations are conducted to investigate the optical properties of 200 nm diameter SiO2 particles at the focal plane of the AOVM. The trapping ability of the AOVM is successfully validated, exhibiting favorable characteristics including constant optical force, stable kinematic state of trapped particles, and consistent capture positions, surpassing those of the optical vortex metalens.

Liquid-phase Integrated 3d Printed Biological Lenses for Lamellar Corneal Substitute.

Compared to traditional biological lenses that are used to correct and repair optical systems, such as contact lenses, vision correction surgery, and corneal and lens replacement, three-dimensional (3D) printed biological lenses can be customized according to user needs. However, the layer-by-layer principle of 3D printing leads to a staircase effect, which cannot meet the critical requirements of surface quality during the manufacturing process of biological lens, particularly with soft materials. Here, a liquid-phase printing strategy and a surface tension-dependent (STD) post-processing method are proposed that use the surface tension of the liquid to reconstruct the air-liquid interface. This eliminates the staircase effect caused by the stacking of units during 3D printing. The coordinates of integrated printing enable high-accuracy shape control of soft materials. Based on this method, using a typical biological lenses as an example, the surface quality of printed lamellar corneal substitute (LCS) was improved from ±20.0μm to ±0.2μm, and the thickness feature size was reduced from ±500μm to ±150μm. It can be used to fit the curvature and thickness of the human cornea. The visible light transmittance reaches the level of the natural cornea (∼85%) and is biocompatible. Liquid-phase 3D printed biological lenses performed better in vivo in rabbit eyes than the molded group. This method can potentially boost research on artificial biological lens printing technology and has good potential for use in future clinical applications. This article is protected by copyright. All rights reserved.

Changes in Expression in BMP2 and Two Closely Related Genes in Guinea Pig Retinal Pigment Epithelium during Induction and Recovery from Myopia.

We previously reported differential gene expression of the bone morphogenetic protein 2 (Bmp2) in guinea pig retinal pigment epithelium (RPE) after 1 day of hyperopic defocus, imposed with a negative contact lens (CLs). The study reported here sought to obtain insights into the temporal profiles of gene expression changes in Bmp2, as well as those of two closely related genes, the inhibitor of DNA binding 3 (Id3) and Noggin (Nog), both during myopia induction and when the CL treatment was terminated to allow recovery from induced myopia. To induce myopia, 2-week-old pigmented guinea pigs (New Zealand strain, n = 8) wore monocular -10 diopter (D) rigid gas-permeable (RGP) CLs for one week, while the other eye served as a control. Ocular measurements were made at baseline, 3 days, and 7 days after the initiation of CL wear, with treatment then being terminated and additional measurements being made after a further 3 days, 1 week, and 2 weeks. Spherical equivalent refractive errors (SERs), axial length (AL), choroidal thickness (ChT), and scleral thickness (ScT) data were collected using retinoscopy, optical biometry (Lenstar), and spectral domain optical coherence tomography (SD-OCT), respectively. RPE samples were collected from both eyes of the guinea pigs after either 1 day or 1 week of CL wear or 1 day or 2 weeks after its termination, and RNA was subsequently isolated and subjected to quantitative real-time PCR (qRT-PCR) analyses, targeting the Bmp2, Id3, and Nog genes. Mean interocular differences (treated-control) in AL and SER were significantly different from baseline after 3 and 7 days of CL wear, consistent with induced myopia (p < 0.001 for all cases). Termination of CL wear resulted in the normalization (i.e., recovery) of the ALs and SERs of the treated eyes within 7 days, and the earlier significant ChT thinning with CL wear (p = 0004, day 7) was replaced by rapid thickening, which remained significant on day 7 (p = 0.009) but had normalized by day 14. The ChT changes were much smaller in magnitude than the AL changes in both phases. Interocular differences in the ScT showed no significant changes. The Bmp2 and Id3 genes were both significantly downregulated with CL wear, after 1 day (p = 0.012 and 0.016) and 7 days (p = 0.002 and 0.005), while Bmp2 gene expression increased and Nog gene expression decreased after the termination of CL wear, albeit transiently, which was significant on 1 day (p = 0.004 and 0.04) but not 2 weeks later. No change in Id3 gene expression was observed over the latter period. Conclusions: The above patterns of myopia induction and recovery validate this negative RGP-CL model as an alternative to traditional spectacle lens models for guinea pigs. The defocus-driven, sign-dependent changes in the expression of the Bmp2 gene in guinea pig RPE are consistent with observations in chicks and demonstrate the important role of BMP2 in eye growth regulation.

Dielectrophoretic liquid lens driven by interdigitated sidewall electrodes.

This paper proposes a dielectrophoretic (DEP) liquid lens that is driven by interdigitated electrodes distributed on the sidewalls and has a structure similar to that of the electrowetting one produced by the company Corning. The interdigital electrodes are formed by winding double flexible wire electrodes wrapped in dielectric layers on the sidewall. Compared with the traditional planar electrode DEP lens, the proposed model ensures the stability of the optical axis of the liquid lens, simplifies the construction process of the interdigital electrode, realizes a continuous change in the focus from negative to positive, and reduces the response time. A truncated conical cavity dielectrophoretic liquid lens with an aperture of 5 mm is fabricated. When the voltage is 0-260 Vrms, it can reach shortest negative and positive focal lengths of -100 mm and 100 mm with a driving time of 190 ms and a relaxation time of 133 ms.

Accuracy of Traditional and Modern Formulas for Intraocular Lens Power Calculation After Radial Keratotomy Using Standard Keratometry.

To compare the accuracy of multiple traditional and modern intraocular lens (IOL) power calculation formulas in post-radial keratotomy (RK) patients undergoing cataract surgery. This retrospective case series included 50 eyes with prior RK who underwent routine phacoemulsification surgery with single-piece acrylic IOL implantation (A constant = 118.8). Outcomes of multiple formulas were calculated. Included formulas were SRK/T, Holladay 1, Holladay 2, Haigis, Barrett True-K, Haigis and Barrett True-K (target refraction of 0.50 D), Barrett Universal II, Kane, PEARL-DGS, Shammas no history, DK SRK/T, DK SRK/T (target refraction of 0.50 D), Double K (DK) Holladay 1, and DK Holladay 1 (target refraction of 0.50 D). Averages of multiple combinations of best-performing single formulas were calculated. Primary outcome is mean absolute error (MAE). Haigis (with -0.50 D target refraction) and DK SRK/T showed the lowest mean and median absolute errors (MedAE) followed by Haigis, Barrett True-K, and Barrett True-K (with -0.50 D target refraction). Combinations of 3, 4, or 5 of best performing single formulas yielded good results with >60% of cases within +0.50 D of intended refraction and MAE around 0.50 D. The best performing formulas with flatter K readings were PEARL-DGS and Haigis (with additional -0.50 D target refraction) with MAE of 0.72 + 0.71 D and 0.70 + 0.70 D, respectively, followed by Barrett True-K (with intended -0.50 D target refraction) with MAE of 0.75 + 0.63 D. Using an average of three or more Haigis (with -0.50 D target refraction), the Barrett True-K, DK Holladay 1, and DK SRK/T formulas showed better outcomes than using a single formula for IOLMaster 700 standard K readings. The PEARL-DGS formula showed better accuracy in eyes with flatter K readings (<38 D).

Raman Spectroscopy Fiber Probe Based on Metalens and Multimode Fiber for Malachite Green Determination

The limit of Raman spectroscopy probe based on the traditional objective lens, such as integration difficulties, is the primary motivation to find better alternatives. Due to the potential of vertical integration and significant flexible design, a Raman spectroscopy fiber probe based on metalens at the fiber end facet is demonstrated. Using the "contact and separate" method, we successfully transferred the metalens to the end face of multimode fiber (MMF) to construct the Raman fiber probe with an ultrahigh numerical aperture (NA) of up to 0.66@air. In the case of the surface-enhanced Raman scattering (SERS) substrate composed of Au-plated anodic aluminum oxide (AAO) membrane with the same dry malachite green (MG), compared with the commercial Raman scattering light acquisition system based on an objective lens, our Raman signal intensity increases by at least 2.7 times at the Raman characteristic peak for MG. In the MG aqueous solution, the measurement with a limit of detection (LOD) of 10-9 mol/L@1616 cm-1 is realized. The proposed SERS sensing configuration based on the proposed Raman fiber probe and Au-covered AAO membrane also shows a broad application potential of real-time monitoring for other markers in the fields of food safety and environment detection.

Compact Sub‐Semicircular Axial Gradient Index Lens Synthesized by Metasurfaces: A Promising Solution for Miniaturized Antenna and Subwavelength Focusing Systems

AbstractWe present the design, fabrication, and experimental measurements of an Axial Gradient‐index (AGRIN) flat lens synthesized by 2D periodic metallic patches on a grounded dielectric slab, known as metasurfaces. Metasurfaces can be considered as artificial materials that possess unique characteristics, which mainly revolve around the two‐dimensional distribution of the structure. By manipulating the phase and amplitude of the near‐fields over the surface of the metasurface, specific values of the effective permittivity and permeability can be achieved, thereby regulating the overall field behavior by gaining control of the refractive index that is related to the aforementioned two material parameters. By configuring the refractive index, metasurfaces enable the manipulation of the direction in which electromagnetic waves propagate, as dictated by Snell's law. By varying the geometric dimensions of unit cells in each segment that compose the lens, the gradient refractive index profile required for our AGRIN lens can be achieved. A primary feature of this lens lies with its semicircular structure, in contrast to conventional circular ones. Its perimeter comprises a convex boundary and a straight one. In comparison to traditional circular lenses like the Luneburg lens and Maxwell fisheye lens, our proposed AGRIN lens offers the advantage of being more compact. Despite its smaller area, the AGRIN lens maintains its focusing ability. The AGRIN lens is capable of focusing over 71.75% of the energy from the incident wave onto the focal point. This efficient focusing ability, combined with its reduced size, makes the AGRIN lens highly advantageous for various applications.

Split-Lohmann Multifocal Displays

This work provides the design of a multifocal display that can create a dense stack of focal planes in a single shot. We achieve this using a novel computational lens that provides spatial selectivity in its focal length, i.e, the lens appears to have different focal lengths across points on a display behind it. This enables a multifocal display via an appropriate selection of the spatially-varying focal length, thereby avoiding time multiplexing techniques that are associated with traditional focus tunable lenses. The idea central to this design is a modification of a Lohmann lens, a focus tunable lens created with two cubic phase plates that translate relative to each other. Using optical relays and a phase spatial light modulator, we replace the physical translation of the cubic plates with an optical one, while simultaneously allowing for different pixels on the display to undergo different amounts of translations and, consequently, different focal lengths. We refer to this design as a Split-Lohmann multifocal display. Split-Lohmann displays provide a large étendue as well as high spatial and depth resolutions; the absence of time multiplexing and the extremely light computational footprint for content processing makes it suitable for video and interactive experiences. Using a lab prototype, we show results over a wide range of static, dynamic, and interactive 3D scenes, showcasing high visual quality over a large working range.

Large field-of-view thermal imaging via all-silicon meta-optics.

A broad range of imaging and sensing technologies in the infrared require large field-of-view (FoV) operation. To achieve this, traditional refractive systems often employ multiple elements to compensate for aberrations, which leads to excess size, weight, and cost. For many applications, including night vision eye-wear, air-borne surveillance, and autonomous navigation for unmanned aerial vehicles, size and weight are highly constrained. Sub-wavelength diffractive optics, also known as meta-optics, can dramatically reduce the size, weight, and cost of these imaging systems, as meta-optics are significantly thinner and lighter than traditional refractive lenses. Here, we demonstrate 80° FoV thermal imaging in the long-wavelength infrared regime (8-12µm) using an all-silicon meta-optic with an entrance aperture and lens focal length of 1cm.

Reconfigurable Terahertz Spatial Deflection Varifocal Metamirror.

A traditional optical lens usually has a fixed focus, and its focus controlling relies on a bulky lens component, which makes integration difficult. In this study, we propose a kind of terahertz spatial varifocal metamirror with a consistent metal-graphene unit structure whose focus can be flexibly adjusted. The focus deflection angle can be theoretically defined by superimposing certain encoded sequence on it according to Fourier convolution theorem. The configurable metamirror allows for the deflection of the focus position in space. The proposed configuration approach presents a design concept and offers potential advancements in the field of developing novel terahertz devices.

Http://journal-spqeo.org.ua/n2_2023/P180-187abstr.html

An algorithm has been developed for modeling the parameters of micro-prismatic specialized plane-focusing Fresnel lenses. Such lenses are more effective for application in photovoltaic modules for concentration of sunlight compare to the traditional point-focusing Fresnel lenses. The technical parameters of photovoltaic modules with these lenses were investigated. The method for manufacturing above lenses by diamond cutting technique and subsequent thermal pressing of silicone blanks is proposed. Some samples of specialized plane-focusing microprisms, which are made using our simulation results, have been experimentally investigated.

Lean Production for Reducing Wastes in Convex Lens Production Process

This research aimed to investigate the waste generated during the production of traditional convex lens. The study proposed a method to eliminate such waste by utilizing value stream mapping (VSM) as a tool for data collection and waste identification throughout the entire production process. Through the analysis of data using VSM, three specific types of waste were identified. These included losses resulting from ineffective utilization of the oven machine during the polymerization process, inefficiencies in personnel performance, and inappropriate working procedures. To address these waste issues, the task employed the work study method to optimize machine utilization, develop efficient work processes for personnel, and improve inappropriate procedures to enhance overall efficiency. The ECRS method was utilized to improve the process of waste elimination. The research findings demonstrated substantial reductions in waste within the production process. Specifically, the total throughput time decreased from 661.07 minutes to 480.68 minutes, representing a reduction of 27.29%. Furthermore, the total production lead time decreased from 1.20 days to 0.94 days, indicating a reduction of 21.67%. In terms of personnel, the workforce decreased from 42 employees per shift to 29 employees, reflecting a decrease of 30.95%. Finally, the number of oven machinery units required for all three shifts decreased from 3 ovens to 2 ovens, resulting in a reduction of 33.33%.

The effects of household water insecurity on child health and well‐being

AbstractWe extend the conceptualization of the social and health burdens of household water insecurity on children beyond the traditional narrow lens of microbiological pathogens and diarrhea. The global burden of disease associated with water insecurity has traditionally focused on diarrheal disease as the most significant driver of infant and child mortality. However, there are many other pathways through which children experience adverse health and social consequences from inadequate or unsafe household water. We synthesize evidence of a broad range of health impacts, affecting children from infancy to late adolescence, across four domains: exposure to unsafe water; interruptions to growth and development through poor nutrition and hydration; negative social effects such as school absenteeism and interpersonal violence; and other non‐communicable health issues such as mental health, injuries, and reproductive health. The growing burden and urgency of these issues is implicated by forecasted increases in climate‐ and conflict‐induced water scarcity, human displacement, and environmental contamination in the decades ahead.This article is categorized under: Engineering Water &gt; Water, Health, and Sanitation Human Water &gt; Rights to Water

Assessing smallholders’ heterogeneity towards sustainable agrifood value chain in developing countries

PurposeAgrifood value chains in developing countries are transforming into higher value markets which require sustainable practices, with smallholders playing a critical role. However, smallholders are a heterogeneous group which may have discrepancies in outcomes to meet sustainability standards. This paper aims to empirically investigate smallholders' heterogeneity towards sustainable value chain practice in developing countries.Design/methodology/approachEight key enabling factors of sustainable value chain transformation were used to explore smallholders' typology, then profiled, based on their socio-economic status and current practices. A quantitative method was applied in Indonesia's cashew sector with 159 respondents from the primary producer area on Madura Island. A combination of descriptive analysis, cluster analysis, cross-tab analysis and one-way ANOVA analysis was used in this study.FindingsFour types of groups were identified, each with distinct characteristics and arranged in priority order as follows: accelerator, progressor, inattentive and conservative groups. Interventions can be implemented on per clusters basis or based on potential similarities among clusters, depending on priority. It is noted that the pursuit of sustainable value chain practices by smallholders is not necessarily associated with high socio-economic status, as those with low socio-economic status may have a stronger inclination towards them.Practical implicationsThe paper enhances awareness of practitioners and policymakers regarding smallholders' heterogeneity in sustainable value chain practice. It enables more effective and focused interventions to support smallholders who require assistance in sustainable production and value-adding activities. Different smallholders' characteristics call for different assistance/intervention. Practitioners can recognise smallholders' characteristics that are more compatible with higher value markets and sustainability requirements to better integrate their practices. Policymakers must carefully develop short-term and long-term interventions based on the activities prioritised by particular traits to “hit the right button” for smallholders' practice development.Originality/valueThis study investigates the typology of smallholders towards sustainable value chain practices by using eight enabling factors and profiling them based on their socio-economic condition and current practices. Additionally, this study shifts the focus of typology exploration away from the traditional lens of farm sustainability to a larger perspective which encompasses sustainable value chain activities.

Terahertz super-resolution imaging based on a confocal waveguide and a slider-crank scanning mechanism.

Due to the limitation of Abbe diffraction limit, the traditional terahertz (THz) continuous wave imaging methods based on lenses or mirrors are difficult to achieve super-resolution. Here we present a confocal waveguide scanning method for THz reflective super-resolution imaging. In the method, a low loss THz hollow waveguide is used to replace the traditional terahertz lens or parabolic mirror. Through optimizing the size of the waveguide, we can achieve far field subwavelength focusing at 0.1THz and achieve super-resolution terahertz imaging. In addition, a slider-crank high-speed scanning mechanism is used in the scanning system, and the imaging speed is more than 10 times faster than the traditional step scanning system based on linear guides.

A Review of Optical Tweezers with Metasurfaces

Optical tweezers (OTs) have made significant progress in recent years, realizing the non-contact optical manipulation of target objects through the interaction between light and matter. In addition to trapping particles with the intensity gradient of the beam, a series of complex optical elements are required to properly modulate the beams to expand the operation of optical manipulation. The development of metasurfaces alleviates this problem. Due to the merits of miniaturization, planarization, multi-function, and integration of metasurfaces, these kinds of novel devices have been applied in OT systems. Metasurface devices have been used to replace traditional objective lenses, achieving device integration and even obtaining multi-function of OTs with unique optical properties in applications. OTs with metasurfaces have developed rapidly, and a great deal of work has been carried out on OTs with metasurfaces, as well as discussions on their practical applications. In this review, we regard the latest progress in the field of OTs with metasurfaces. We classify OTs with metasurface and summarize the new impetus brought by metasurfaces for the development of OTs.

Design of refractive–diffractive hybrid lenses for space–time focusing ultrashort laser pulses

We propose a simple formulation for the baseline design of a hybrid lens, consisting of refractive and diffractive elements, intended for focusing ultrashort laser pulses. Lens dispersions up to the second order are considered to obtain easy-to-use formulas. Using this formulation, we designed a refractive–diffractive triplet for near-infrared femtosecond laser pulses and observed that once radius-dependent temporal distortions are removed, chromatic distortions are removed as well, and vice versa. Furthermore, we found that the derived equations for removal of pulse distortions can be readily transformed to traditional lens design equations for optical imaging. This finding facilitates the design of hybridized triplets for ultrafast focusing optics.