Spherical Lens Research Articles

Corneal asymmetry contributes decentration in both sphericaland toric orthokeratology lenses.

To discuss the characteristics of anterior corneal elevation asymmetry in myopic eyes and clarify which kind of asymmetry most influenced lens position. In this retrospective study of 199 consecutive myopic participants, corneal topography was used to analyse asymmetry in anterior corneal elevation. Amongst them, 65 participants (65 eyes) who underwent orthokeratology (31 and 34 with spherical and toric lenses, respectively) were re-evaluated. Stepwise multiple linear regression analysis was used to identify the contributing factors that influenced lens decentration. Receiver operating characteristic curve (ROC) analysis was employed to assess how the corneal asymmetry vector could predict decentration. There were no significant differences in treatment zone decentration (TZDec) between participants wearing toric and spherical lenses (p = 0.60 and 0.64 for 1 week and 1 month of wear, respectively). Amongst the underlying factors, the magnitude of TZDec was only correlated with the amount of corneal asymmetry vector (standardised β = 0.44, 0.48, p < 0.001 for all) after 1 week and 1 month of wear, and the direction of TZDec after 1 month of lens wear was associated with the angle of the asymmetry vector (r = 0.25, p = 0.04). ROC analysis showed that the magnitude of corneal asymmetry vector produced accurate discrimination between non-severe and severe decentration for 1 week and 1 month of wear (area under the curve was 0.93 ± 0.04 and 0.89 ± 0.05, respectively, p < 0.001). Amongst participants whose corneal asymmetry vector exceeded 41.06 μm and was oriented inferiorly, 35.29% showed severe decentration after 1 month of lens wear. In myopic participants, corneal asymmetry existed in the 8.0 mm chord diameter. If the asymmetry vector >41.06 μm and the direction was oriented inferiorly, then practitioners must be vigilant about severe decentration which would not be alleviated by a toric design.

Design strategy for an automotive lens with a wide field of view

To solve the problems in designing a wide field of view (FOV) automotive lens, such as the complicated initial structure solution when using aberration theory and the limited scaling method, a novel design strategy, to the best of our knowledge, based on the compression ratio of field angle is proposed. The wide-FOV automotive lens is first divided into two groups, front and rear lenses, and each group is designed with several parallel plates as starting points using SYNOPSYS software. Then, the two groups are connected as a whole initial optical system. Finally, an iterative process is applied to improve the performance of the initial structure. A wide-FOV automotive lens is designed to verify the feasibility and effectiveness of the design method proposed in this paper. The wide-FOV automotive lens has the characteristics of good imaging quality, large aperture, and small size and consists of six spherical lenses. The result of the design indicates that this method based on the compression ratio of field angle is simple, effective, fast in convergence, and provides a good starting point for the design of a wide-FOV automotive lens.

Ultracompact optical microscopes made of liquid crystal Pancharatnam–Berry optical elements

Ultracompact optical systems are increasingly sought after for applications such as consumer electronics and medical imaging. Here, we present a design and manufacturing approach for ultracompact bright- and dark-field optical microscopes entirely made of flat liquid crystal optical elements. Both systems utilize liquid crystal PB lenses as objective and tube lenses, while the dark-field optical microscope incorporates an additional Q-plate with a +1 topological defect to filter zero-order light. We demonstrate two optical microscopic systems with a numerical aperture of 0.25 and overall thickness of just 5 mm. The system can achieve high imaging performance with a resolution better than 7 µm. We further demonstrate an exemplary application in biological imaging to effectively enhance edge contrast in imaging onion epidermal cells. This work presents an example in exploiting the flatness and high quality of liquid crystal optical elements to achieve compactness and high-quality imaging promising for various applications.

Electrically tunable graded photonic crystal lens based on graphene plasmons.

Controlling the nonlinear relationship between surface plasmon polariton (SPP) mode index and chemical potential of graphene can be used in the field of active transformation optics. Here, we propose an electrically tunable 2D Graded Photonic Crystal (GPC) lens based on graphene SPP platform. Our platform comprises a graphene monolayer integrated into a back-gated structure with nano-patterned gate insulators. When the chemical potential of the graphene surface is designed to operate in the nonlinear region, the designed GPC lens can be continuously transformed between a Maxwell's fish-eye lens and a Luneburg lens by tuning the gate voltage. The range of the lens background chemical potential for allowing this transformation is systematically studied. To compensate for the significant errors inherent in the conventional effective medium theory (EMT) during the homogenization of photonic crystals (PCs), we propose a generalized effective medium theory (GEMT). The validity and accuracy of this approach are verified through comparisons with true values (based on rigorous eigenvalue solutions) and EMT values. Due to its advantages of on-site controls and easy fabrication characteristics, the proposed graphene GPC provides a new way for practical on-chip light manipulation.

A time-division achromatic imaging method for liquid crystal lens

A time-division achromatic imaging method for liquid crystal lens

Electrically Tunable Liquid Crystal Lens with Varifocal Capability

Electrically Tunable Liquid Crystal Lens with Varifocal Capability

Gravitational lens system as a long baseline detector of extremely low frequency primordial gravitational wave

ABSTRACT The effect of extremely low frequency primordial gravitational wave with arbitrary direction of propagation on a gravitational lens system in expanding universe is investigated. From the point of view of real astrophysical lens model, singular isothermal sphere lens model is adopted in the gravitational lens system. The results show that, under the perturbation from extremely low frequency primordial gravitational wave, time delay in the gravitational lens system is very sensitive to extremely low frequency primordial gravitational wave and could strongly deviate from that deduced from theoretical model. This means that the strongly deviated time delay could be the imprint of extremely low frequency primordial gravitational wave on gravitational lens system, indicating that gravitational lens system could be used as a long baseline detector to detect extremely low frequency primordial gravitational wave.

Cost-effectiveness of low-astigmatism correction with toric or spherical intraocular lenses combined with corneal incisions: an economic evaluation.

To assess the cost-effectiveness of the treatment of low corneal astigmatism (≤1.5 diopters) at the moment of cataract surgery. Qvision, Ophthalmology Department, VITHAS Almería Hospital, Spain. Economic evaluation. A decision tree was used to assess the cost-effectiveness of implanting spherical vs toric intraocular lenses (IOLs) or spherical lens combined with the following corneal incisions: limbal-relaxing incisions conducted manually (M-LRI) or assisted by femtosecond laser (F-LRI), arcuate keratotomies conducted manually (M-AK) or assisted by femtosecond laser (F-AK), and intrastromal arcuate keratotomies (F-iAK). Outcomes of cost were selected from a patient perspective considering the gross cost of each one of the surgeries at European centers, and the effectiveness variable was the probability of achieving a visual acuity of 20/20 postoperatively. A sensitivity analysis was conducted to assess the uncertainty considering the evidence retrieved from the transition probabilities of the model, effectiveness, and cost. F-AK or toric IOLs were the most effective treatments, increasing an 16% or 9%, respectively, in the percentage of eyes attaining 20/20 vision. The M-LRI, F-iAK, and F-LRI procedures were strongly dominated while the M-AK and toric IOL were weakly dominated by the F-AK. A patient with low corneal astigmatism would need to be willing to pay 360€ (95% CI, 231-1224) with F-AK and 472€ (95% CI, 149-4490) with toric IOLs for a 10% increase in the probability of achieving 20/20 vision. From patient perspective, F-AK was generally the most cost-effective treatment, although toric IOLs can dominate in some countries.

Design of a tunable microlens based on hybrid single-wall carbon nanotube and liquid crystal

: Tunable liquid crystal (LC) lenses have garnered significant interest in recent years for their lightweight, cost-effectiveness, and versatility in applications like augmented reality, ophthalmic devices, and astronomy. Despite numerous proposed structures to enhance LC lens performance, achieving a minimal focal length while preserving image quality and balancing cost and complexity remains a daunting challenge. Adaptive microlenses encounter these obstacles due to physical constraints and diffraction effects. One promising solution lies in using adaptive LC-carbon nanotubes (CNTs) lenses. By adjusting external stimuli like electric or magnetic fields, it is possible to modify the refractive index distribution of the LC medium, thus changing the focal length of the microlens. When paired with CNTs, the LC molecules' orientation and control of focal length can be even more precise. Our research findings suggest that to achieve the shortest focal length in a microlens with a thickness of 22.5 μm, it is recommended that the diameter of the CNT should not exceed 10 nm, and the height of CNT should fall within the range of 10 to 20 μm considering the presence of screening effect. Conversely, for a microlens with low full width at half maximum (FWHM), narrower light spot, it is advisable to use CNT with a diameter larger than 100 nm and a height greater than 13 μm. Additionally, for a microlens with an efficient Fresnel number in the range of 1 to 10, the microlens should have CNT with widths from 100 to 200 nm. Therefore, based on the importance of each factor (focal length, FWHM, and Fresnel number), the dimensions of the carbon nanotube can be selected to suit the desired application.

3D Optical Wedge and Movable Optical Axis LC Lens

Current liquid crystal (LC) lenses cannot achieve lossless arbitrary movement of the optical axis without mechanical movement. This article designs a novel bottom electrode through simulation and optimization, which forms a special LC lens with an Archimedean spiral electrode, realizing a 3D LC wedge and an arbitrarily movable LC lens. When only the bottom electrode is controlled, it achieves a maximum beam steering angle of 0.164°, which is nearly an order of magnitude larger than the current design. When the top and bottom electrodes are controlled jointly, a 0.164° movement of the lens optical axis is achieved. With focal length varies, the movement of the optical axis ranges from zero to infinity, and the lens surface remains unchanged during movement. The focus can move in a 3D conical area. When the thickness of the LC layer is 30 μm, the fastest response time reaches only 0.635 s, much faster than now.

A simple way to achieve planar excitation of arc-shaped array feeds in two-dimensional beam-steerable spherical lens antenna

In this article, a simple technique for achieving planar excitation positions of arc-shaped array feeds in a two-dimensional (2D) beam-steerable spherical lens antenna (SLA) is proposed. Specifically, a cuboid solder model is introduced to connect the feedlines of the feeds with the coaxial probe. An equivalent circuit model of the bowtie feed unit with solder is proposed to illustrate the impact of the introduced solder on the port matching. Additionally, the excitation position is altered by extending the microstrip feedline, which does not change the radiation structure of the feed nor affect its phase center. Subsequently, a homogeneous dielectric SLA with a 139-element bowtie-shaped dipole feed array is constructed to verify the planar excitation position scheme for the arc-shaped array feeds, which facilitates system integration. The theoretical calculation formulas for the beam pointing angles of numerous beams are also proposed. In the fabricated prototype, all feeds exhibit an overlapping bandwidth of 31–36.7 GHz for reflection coefficients, with the coupling less than -20 dB. The 139 switched beams cover a 2D continuous beam space of [−33°, 33°], with adjacent beam crossover levels around -4 dB. The measured peak gain is 28.7 dBi at 34.5 GHz, with an aperture efficiency of 57%.

Multifunctional multifocal lens for simultaneous edge and polarisation imaging

ABSTRACT The method of inserting ultrathin devices in the Fourier plane of the 4F imaging system can achieve multifunctional imaging. However, such a method generally requires precise alignment in the system, which also makes the system more complex. Here, we present an imaging system that incorporates a multifocal Pancharatnam–Berry (PB) phase liquid crystal (LC) lens capable of achieving simultaneous edge and polarisation imaging. Without placing optical elements in the Fourier plane of the 4F system, the proposed imaging system replace a refracted lens in 4F system by multifocal LC lens, which integrates edge and polarisation imaging modes. The phase distribution of multifocal lens is obtained through manipulating the positions and polarisation states of four foci with holographic principles. Furthermore, the imaging system based on the proposed multifocal lens has been shown to be effective in simultaneously achieving polarisation and edge imaging with broadband characteristics. The proposed optical system effectively reduces the complexity of the imaging system, which is expected to be applied in the fields of biomedical imaging, optical interconnection and microscopic imaging.

You've got to hide your myopia away: John Lennon's contactlenses.

John Lennon has an enduring, instantly recognisable, iconic, spectacle look. However, prior to 1966, he was rarely seen wearing glasses in public. From ages 7 to 26, he effectively hid his myopia away, including a period of unsuccessful contact lens wear during Beatlemania. This narrative review examines John's experience with contact lenses from 1963 to 1966 when he wore corneal rigid lenses made from polymethylmethacrylate, which regularly fell out. This frequent lens ejection was most likely due to the interaction between his upper eyelid and a spherical back surface rigid lens fitted to his right eye, which had a moderate degree of with-the-rule corneal astigmatism. John's recollection that his contact lenses stayed in place while 'stoned' supports this hypothesis, as a cannabis-induced upper eyelid ptosis would reduce the likelihood of lens ejection.

Developmental characteristics and control effects of myopia and eye diseases in children and adolescents: a school-based retrospective cohort study in Southwest China

ObjectivesTo characterise the prevalence of myopia and eye diseases among school adolescents and children in Southwest China, and to evaluate the effectiveness of myopia control tools.DesignRetrospective cohort study.SettingAcross 95 basic...

Switching in microseconds: design of a 5 × 5 non-blocking free space optical switch at 1550nm with a piezo-actuator and beam-steering lens system

Modern data center networks (DCNs) require optical switches with ultra-low loss, ultra-fast reconfiguration speed, high throughput, and high extinction ratio performances. In this work, we propose the design of a 5 × 5 optical switch at 1550 nm based on a piezo-actuator serving as a translating input optical source, and a beam-steering system built of spherical lenses to complete the switching behaviour. An ultra-fast actuator switching speed is estimated as 1.55 μs latency for a single connection with a demo circuit. We further simulate the beam-steering system end-to-end in a commercial optical design software CODE V and demonstrate a theoretical 2.16 dB insertion loss for a single connection in the switch at optimum alignment.

Lens height paraments comparison according to ciliary sulcus width (CSW): a pilot study of the predictive role of CLR and STSL for vault after ICL implantation

BackgroundTo assess the relationship between postoperative implantable collamer lens (ICL) vault and lens height obtained from two different measurements.MethodsA retrospective case series study enrolled eyes with horizontally implanted ICL. Crystal lens rise (CLR) and the distance between STS plane and anterior crystalline lens surface (STSL) were measured in the horizontal and vertical directions using ultrasound biomicroscopy (UBM). We compared the differences in the parameters measured in both horizontal and vertical directions. The participants were categorized into three groups according to ciliary sulcus width (CSW) which is defined as the distance between the posterior angle of the iris and the anterior angle of the ciliary process: narrow CSW group (NSG); medium CSW group (MSG); and wide CSW group (WSG). The correlations between CLR/STSL and vault were examined in each of the three groups. Biased correlation analysis was used further to contrast the correlation between CLR/STSL and vault.ResultsThis retrospective study included 223 myopic eyes. Vertical STSL (VSTSL) and vertical CLR (VCLR) exhibited significantly greater values compared to their horizontal counterparts (both P < 0.05). None of the indicators were statistically different between the three groups. In both NSG and MSG, STSL/CLR correlated with vault, while in WSG, only STSL correlated with vault (r=-0.316, P = 0.013). In contrast to HCLR, the correlation between HSTSL and vault remained after controlling for HCLR (r=-0.162, P = 0.015).ConclusionsSTSL should deserve more attention in the preoperative evaluation of ICL compared to CLR especially when CSW is large.

Evaluation of beam convergence driven by spherical gradient refractive index lenses based on nonparaxial beam propagation

Evaluation of beam convergence driven by spherical gradient refractive index lenses based on nonparaxial beam propagation

Optical configurations for applying antireflective nanotexture on spherical lenses by ultrashort laser structuring

This paper focuses on minimizing the optical reflection on spherical fused silica lenses using femtosecond (fs) laser nanostructuring. A unique type of nanopillar formation has been observed on SiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{SiO}_2$$\\end{document} surfaces possessing antireflective properties when irradiated with a specific number of overlapping pulses, polarization, and fluence levels. Maintaining precise control over these sensitive technological parameters such as defocus and incident angle during the processing of geometrically complex shapes presents a significant challenge. This study proposes a theoretical optical arrangement to address this limitation by the design of a custom scanner system optimized for curved surfaces. The paper details the optimization process of such a bent image space (inverse-hypercentric) optical system using Zemax OpticStudio. Although the practical realization of the arrangement has not been performed, simulations are conducted to prove the functionality of the concept. Furthermore, we propose a practical method for segmented structuring of spherical surfaces based on consecutive repositioning and irradiation using an industrial robotic arm. By constructing the optical model, the necessary resolution of the segmentation has been calculated for a typical F-Theta scanner system and experimental verification has been performed.

Comparing reading performance in toric vs. spherical contact lens correction of patients with astigmatism: Preliminary results

Comparing reading performance in toric vs. spherical contact lens correction of patients with astigmatism: Preliminary results

Design, modeling, fabrication, and characterization of 50 mm diameter focus tunable liquid crystal lens with enhanced optical performance

Design, modeling, fabrication, and characterization of 50 mm diameter focus tunable liquid crystal lens with enhanced optical performance