Asymmetric Lens Research Articles

Broadband integrative acoustic asymmetric focusing lens based on mode-conversion meta-atoms

Acoustic asymmetric focusing (AAF) has a great potential application in medical ultrasound imaging, focused ultrasound therapy, and nondestructive testing. The advancement of acoustic metamaterials and metasurfaces has provided various mechanisms to design AAF lenses. However, due to the existence of a certain difficulty in realizing sound focusing and asymmetric transmission simultaneously, the realization of the AAF lens with a broad bandwidth and an integrative planar structure still remains a challenge. Here, we theoretically propose and experimentally demonstrate an integrative planar AAF lens based on a type of mode-conversion meta-atom composed of two types of phased unit cells with a phase difference of π and a step waveguide. The meta-atom can realize the conversion between the zero-order and first-order waves and asymmetric sound transmission, which arises from the phase modulation and the cutoff frequency of the first-order wave, respectively. Based on the proposed mode-conversion meta-atoms, we design a broadband AAF lens with high performance, in which its fractional bandwidth can reach about 0.19 and the focus size is only about 0.38λ. The proposed mode-conversion meta-atom and its associated AAF lens provide diverse routes for designing asymmetric multi-functional sound devices with promising applications.

Aberration-Based Quality Metrics in Holographic Lenses.

Aberrations and the image quality of holographic lenses were evaluated by a Hartmann–Shack (HS) wavefront sensor. Two lenses, one recorded with a symmetrical configuration and the other with an asymmetrical one, were stored in a photopolymer called Biophotopol. Each was reconstructed with two different wavelengths, 473 nm and 633 nm. Different metrics were applied to determine and quantify the aberration of the lenses (Zernike coefficients, Seidel coefficients, Marechal tolerances, root-mean-square (RMS), peak to valley, critical fraction of the pupil), and the quality of the image they provided (Strehl ratio, entropy, cutoff frequency, modulation transfer function (MTF), and area under the MTF). Good agreement between the metrics related to optical quality was obtained. The negative asymmetric holographic lenses had less aberration than the positive symmetric ones.

Symmetric and asymmetric freeform lens to produce uniform illumination

We propose two energy-mapping methods to produce a uniformly illuminated area for a nontilted (straight) and a tilted light source toward a target plane. These energy-mapping methods define the positions of the desired points (the destination points of the refracted rays of a light source) on an illuminated area. The surface of the lenses can then be formed through the position of the desired points. Based on these design methods, two freeform lenses, (i) a symmetric lens and (ii) an asymmetric lens, were designed to provide uniformity within a rectangular illumination footprint for a nontilted and a tilted light source, respectively. This method can produce uniformity for a tilted light source within 0 deg to 45 deg toward the normal vector on the target plane. Two freeform lenses for 0 deg and 20 deg tilted toward a target plane were designed. The illumination footprint of the symmetric and asymmetric freeform lenses was evaluated through ray-tracing simulations and experiments. Both models produce over 90% uniformity within an illuminated area.

Morse lens [Invited

In this Letter, we find that Morse potential (proposed about 90 years ago) could be connected to Coulomb potential (or Newton potential) and harmonic potential (or Hooke potential) by conformal mappings. We thereby design a new conformal lens from Morse potential, Eaton lens, and Luneburg lens and propose a series of generalized Eaton/Luneburg lenses. We find that this Morse lens is a perfect self-focusing asymmetric lens that differs from a Mikaelian lens. Our theory provides a new insight to Morse potential and other traditional potentials, and revisits their classical applications on designing lenses.

The hybrid lighting system with natural light and LED for tunnel lighting

The traditional tunnel lighting has the problem of poor lighting environment and huge energy consumption. This study uses natural light and LED as the light source to design two different lenses. When the natural light is sufficient, the natural light illumination system is used in the threshold zone and the exit zone, give tunnel lighting to reduce the number of LEDs used. When the natural light is insufficient, the sensor will detect the natural light level of the collimator exit to control the LED to compensate for the light or to illuminate the tunnel alone. In the two designs, the linear Fresnel lens is established by the Fresnel structure, and the free-form asymmetric lens of the LED is established by the catadioptric method. Finally, the model of the Hsueh-Shan tunnel was established by DIALux, and the two lenses were used simultaneously for mixed illumination to simulate average luminance, total uniformity, and longitudinal uniformity. The lens design reduces the influence of glare, and the design of the lamp spacing reduces the zebra pattern on the road surface. Combined with natural light and artificial light source, the tunnel light does not need to be 24 h of operation can save energy.

Efficacy of the standardized asymmetric soft contact lens with a decentered optic zone design for correcting visual performance in patients with keratoconus

Efficacy of the standardized asymmetric soft contact lens with a decentered optic zone design for correcting visual performance in patients with keratoconus

Progressive Multifocal Liquid Lenses Based on Asymmetric Freeform Surface Structure of Nonuniform Thickness Elastic Membranes with Different Constraints

For a progressive multifocal liquid lens with an elastic membrane deformed by liquid pressure, to realize a reasonably power distribution, asymmetric deformation characteristics of the membrane surface are needed. Based on the asymmetric freeform surface structure, this paper proposed progressive multifocal liquid lenses focused by liquid with nonuniform thickness membranes. The structure and mathematical model of power distribution for the lens are introduced. The membrane deformation and the corresponding power distribution of the lenses with asymmetric freeform surface are predicted and compared under uniform pressure load and different boundary conditions using the finite element method. An optical testing system is constructed to analyze the optical characteristics of the fabricated lenses through observing the focusing performance of the F target image at different regions of the lenses. Experimental results show that the liquid lenses can realize as asymmetrical progressive multifocal liquid lenses after liquid accommodation; meanwhile, the trends of power distribution of the lenses generally agree well with simulations.

Optical measurement of concentration-dependent diffusion coefficients of binary solution using an asymmetric liquid-core cylindrical lens

An optical method for measuring concentration-dependent diffusion coefficients of binary solution is introduced in this paper. The concentration spatial and temporal profiles (Ce(z, t)s) are obtained from a single experiment using an asymmetric liquid-core cylindrical lens. The concentration-dependent diffusion coefficient is assumed to be a polynomial D(C) = D0 × (1 + α1C + α2C2 + α3C3 + …), where D0 is diffusion coefficient in infinite dilute solution, α1, α2 and α3 are under-determined parameters. The finite difference method (FDM) is applied to solve numerically Fick diffusion equation, the calculated concentration profiles (Cn(z, t)s) by varying the under-determined parameters are compared with the profile Ce(z, t), the parameters(α1, α2, α3, …) corresponding the minimum concentration standard deviation are selected to determine D(C). To verify the proposed method, we have carried out the diffusion experiment of ethylene glycol aqueous solution, the obtained concentration-dependent diffusion coefficients are in good agreement with literature values. On the other hand, the obtained polynomial D(C) has been used to calculate refractive index profiles (nn(z, t)s). Based on the nn(z, t)s, ray tracing method has been applied to simulate the diffusion images, which fit the experimental images very well over a wider range of diffusion time, demonstrating that the proposed method is reliable in rapidly measuring concentration-dependent liquid diffusion coefficients with high accuracy and stability.

Modeling the Evolution of a Freshwater Lens under Highly Dynamic Conditions on a Currently Developing Barrier Island

The drinking water supply on barrier islands largely depends on freshwater lenses, which are also highly relevant for island ecosystems. The freshwater lens presented in this study is currently developing (since the 1970s) below the very young eastern part of the North Sea barrier island Spiekeroog, the so-called “Ostplate.” Due to the absence of coastal protection measures, formation, shape, and extent of the freshwater lens below the Ostplate are unaffected by human activities but exposed to dynamic changes, e.g., geomorphological variations and storm tides. The main aim of this paper was to reconstruct the evolution of the freshwater lens over several decades in order to explain the present-day groundwater salinity distribution. In addition, the study assessed the impact of geomorphological variations and storm tides on the freshwater lens formation. Detailed field observations were combined with a transient 2-D density-dependent modeling approach. Both field observations and simulations show an asymmetric freshwater lens after ~42 years of formation, whereby the horizontal extent is limited by the elevated dune area. The simulations indicate that the young freshwater lens has nearly reached quasi-steady-state conditions mainly due to the continuous mixing with seawater infiltrating during storm tides, which inhibits further growth of the freshwater lens on the narrow island. The findings further show that (i) a neglection of storm tides results in a significant overestimation of the freshwater lens extent, and (ii) the modeled present groundwater salinity distribution and shape of the freshwater lens are predominantly determined by the position and extent of the elevated dune area at the past ~20 years. Hence, annual storm tides have to be directly implemented into numerical models to explain the groundwater salinity distribution and the extent of young freshwater lenses located in highly dynamic tidal environments.

Synthesis of Asymmetrical Charged Particle Lens Using Analytical Potential Model

In the present work, the optimization by synthesis approach in the field of charged particle optics has been followed, where a modified analytical function has been proposed to represent the axial magnetic scalar potential distribution of the charged particle lens. Thereby, the corresponding axial field distribution can be deduced which is necessary to determine the paraxial ray trajectories and the aberration coefficients. Indeed, the present work deals with asymmetrical distributions of the lens field, accordingly, the first order properties and third order aberrations of the charged particle lens have been evaluated under zero and infinite magnification modes taken into account the effect of some geometrical parameters. The present work aims to reconstruct the shape of the pole piece of the magnetic lens that produced the proposed target function. The results have shown that, the pole piece shape of the lens and the field distributions have new irregular configurations as well as the objective properties of the lens are of acceptable values, according to the constraints that are imposed in the design process.

Presbyopic lens exchange (PRELEX) cataract surgery outcomes with implantation of a rotationally asymmetric refractive multifocal intraocular lens: femtosecond laser-assisted versus manual phacoemulsification.

To compare the visual and refractive outcomes obtained with the implantation of a rotationally asymmetric refractive multifocal IOL after femtosecond laser-assisted cataract surgery (FLACS) and conventional lens extraction (CLE). A total of 78 eyes of 58 patients that had undergone conventional phacoemulsification (36 eyes, CLE group) or FLACS (37 eyes, FLACS group) with the implantation of the toric multifocal IOL LU-313 MF30T (Oculentis, Germany) were enrolled in this retrospective study. Mean age was 57.0years at the time of surgery, ranging from 44 to 69years. Visual and refractive outcomes were evaluated during a 12-month follow-up. Likewise, contrast sensitivity was assessed at the end of the follow-up. Significant improvements were observed in both groups in uncorrected distance (UDVA) and near visual acuity (UNVA) at 1month postoperatively (p < 0.001). Differences between groups in these parameters as well as in sphere and cylinder did not reach statistical significance during the whole follow-up (p ≥ 0.079), except for UNVA only at 12months postoperatively (p = 0.018). Concerning corrected near visual acuity, only significant differences between groups were found preoperatively (p = 0.020). Furthermore, only a minimal but significant difference between groups was found at 12months postoperatively in contrast sensitivity for the spatial frequency of 18 cycles/° (p = 0.029). The rotationally asymmetric toric multifocal IOL LU-313 MF 30T provides good visual rehabilitation for near and distance vision after presbyopic lens extraction in eyes with preexisting astigmatism, independently whether the cataract surgery is performed with the FLACS or conventional technique.

Uniform Illumination for Nonplanar Surface Based on Freeform Surfaces

The shapes of target surfaces are nonplanar on many occasions such as undulating road and roof of the tunnel, while the lighting quality generated by traditional nonimaging optical lenses still needs to be further improved. As a result, a novel method is proposed for the design of optical elements generating uniform irradiance distribution on nonplanar target surfaces. A matrix is introduced instead of a single height parameter for improving the mathematical model of asymmetrical lenses, hence a modified mathematical model based on single LED chip and desired irradiance distribution of the nonplanar target surface is established. By solving the equations with the iterative method, the asymmetrical lenses can be obtained through commercial CAD tools. Three different nonplanar surfaces are used to verify the validity of the proposed method, including an inner-spherical surface, undulating surface and arched surface. The results show that the illumination uniformity of the target surface can reach over 70%, and the light efficiency is more than 83%, which are much better than that generated by traditional methods.

How far has the integrated care come? Applying an asymmetric lens to inter-organisation trust amongst health and social care organisations

The extant literature on interpersonal and inter-organisational trust reveals there are many factors that can influence an organisations’ services to integrate and exchange. While these studies have enhanced our understanding of organisational collaboration, we propose an asymmetric perspective that concentrates on factors that eventually lead to the loss of inter-organisational trust in the context of the (National Health Services) NHS and local government by seeking to join-up health and care services. This paper explores trust and asymmetry factors that undermine collaborative spirits towards successful service integration among health and care players. Based on interviews with 42 subjects in the NHS England Better Care Fund (BCF) programme, we present a model that distinguishes between asymmetric factors and affected health and care service integration. Our findings contribute to a scholarly understanding of asymmetry in the public sector and the role of trust in overcoming divisions and facilitating joint-up services among health and care organisations.

Improvement of the Optical Performance of the Geometrical Parameters of Snorkel Magnetic Lens

Two models of asymmetrical magnetic objective lens geometries have been designed and studied. These two models are called Pinhole and Snorkel lenses. The comparison between these models was realized by the aid of simulation EOD program (Electron Optical Design), using the finite element method to analyze the magnetic flux density and optical properties at constant excitation (NI=2000A-t). The optimal model (Snorkel Lens) gives the best characteristics that were compatible with the research purposes in details, such as the changing of air gap and the axial polepiece bore diameter on the optical performance of the snorkel magnetic lens. This type of lens was used in low energies scanning electron microscope (SEM), which achieved the lowest values of the aberrations coefficient at long working distance.

Partial positive refraction in asymmetric Veselago lenses of uniaxially strained graphene

Asymmetric Veselago lenses (AVLs) can be created from ballistic $p\text{\ensuremath{-}}n$ and $n\text{\ensuremath{-}}p\text{\ensuremath{-}}n$ homojunctions of uniaxially strained graphene. This atypical converging electron flow emerges by applying uniaxial tension out of the device's symmetry axes. Part of the electron flow needs to be positively refracted to focus on an asymmetric spot, whose location is tunable with the strain. In AVLs, Klein tunneling is angularly shifted with regard to the normal incidence. This perfect transmission occurs in the straight line that connects the point source and focus, which is unaffected by variation of the Fermi level and voltage gate. Moreover, the mirror symmetry breaking by the strain also causes the asymmetry in Fabry-P\'erot interference. The novel electron optical laws allow us to evidence that reflected and refracted electrons in AVLs lie on the same straight line with opposite group velocities and pseudospins. Unlike isotropic graphene, electrons under normal incidence present backscattering, angles of reflection, and refraction different from zero. The average particle transmission is higher (lower) than the isotropic case when the tensile strain is increased near (far away from) the normal direction. These results may be useful for designing strain-bendable probing tips in scanning tunneling microscopes.

Design of high-efficient TIR lens for tailored illumination with high contrast

In order to achieve a desired irradiance distribution on target plane, we proposed an approach for the design of an asymmetrical TIR lens generating special facula in an area with a large height-diameter ratio, which can reach 1: 12. A mathematical model of a total internal reflection surface based on single LED chip and desired irradiance distribution of the target plane is established, by solving the equations, several 2-D curves are obtained, then combined these 2-D curves into asymmetrical surface by using modeling tools. The results show that this method can be used to produce different irradiance distribution, including polygon, ellipses, pentagram, heart-shaped and lots of different irregular shapes. In particular, the normal vector of luminous surface and target plane are equal, the contrast of boundary region can reach 10000:1 and its efficiency can reach more than 93%.

The impact of microlensing on the standardization of strongly lensed Type Ia supernovae

We investigate the effect of microlensing on the standardisation of strongly lensed Type Ia supernovae (GLSNe Ia). We present predictions for the amount of scatter induced by microlensing across a range of plausible strong lens macromodels. We find that lensed images in regions of low convergence, shear and stellar density are standardisable, where the microlensing scatter is < 0.15 magnitudes, comparable to the intrinsic dispersion of for a typical SN Ia. These standardisable configurations correspond to asymmetric lenses with an image located far outside the Einstein radius of the lens. Symmetric and small Einstein radius lenses (< 0.5 arcsec) are not standardisable. We apply our model to the recently discovered GLSN Ia iPTF16geu and find that the large discrepancy between the observed flux and the macromodel predictions from More et al. (2017) cannot be explained by microlensing alone. Using the mock GLSNe Ia catalogue of Goldstein et al. (2017), we predict that ~ 22% of GLSNe Ia discovered by LSST will be standardisable, with a median Einstein radius of 0.9 arcseconds and a median time-delay of 41 days. By breaking the mass-sheet degeneracy the full LSST GLSNe Ia sample will be able to detect systematics in H0 at the 0.5% level.

The Effect of Coils Area's Ratio and their Separated Distance on the Optical Performance of the Condenser-Objective Magnetic Lens

The work handles the design of an asymmetric double polepiece magnetic lens for the condenser-objective mode having optimum properties through the change of coils area's ratio and their separated distance, which leads to a highest flux density peak of the magnetic field with a lowest spherical aberration coefficient, at the relativistic corrected voltage (Vr=200 kV) and excitation of (NI=10.5 kA-t). The calculation has been made for the magnetic flux lines trajectories and optical properties to limit the defects in the lens and consequently improve the optical performance of the condenser-objective magnetic lens

An axiomatic basis for bidirectional programming

Among the frameworks of bidirectional transformations proposed for addressing various synchronisation (consistency maintenance) problems, Foster et al.’s [2007] asymmetric lenses have influenced the design of a generation of bidirectional programming languages. Most of these languages are based on a declarative programming model, and only allow the programmer to describe a consistency specification with ad hoc and/or awkward control over the consistency restoration behaviour. However, synchronisation problems are diverse and require vastly different consistency restoration strategies, and to cope with the diversity, the programmer must have the ability to fully control and reason about the consistency restoration behaviour. The putback-based approach to bidirectional programming aims to provide exactly this ability, and this paper strengthens the putback-based position by proposing the first fully fledged reasoning framework for a bidirectional language — a Hoare-style logic for Ko et al.’s [2016] putback-based language BiGUL. The Hoare-style logic lets the BiGUL programmer precisely characterise the bidirectional behaviour of their programs by reasoning solely in the putback direction, thereby offering a unidirectional programming abstraction that is reasonably straightforward to work with and yet provides full control not achieved by previous approaches. The theory has been formalised and checked in Agda, but this paper presents the Hoare-style logic in a semi-formal way to make it easily understood and usable by the working BiGUL programmer.

Visual Performance and Optical Quality of Standardized Asymmetric Soft Contact Lenses in Patients With Keratoconus.

To evaluate the visual performance and optical quality of a standardized asymmetric soft contact lens (SCL) used for correction of higher-order aberrations (HOAs) in eyes with keratoconus. We included 30 eyes (26 patients) with keratoconus (average K: 45.7 ± 2.3 diopters [D]). The patients were subjected to corneal tomography, aberrometry, measurements of manifest refraction and visual acuity (VA), and visual analog scale (VAS) assessments. The study lenses were made using a molding method and consisted of six standardized types, in which an asymmetric power distribution of approximately 2 to 12 D (2-D step) was used to correct HOAs. The lens type suitable for each eye was selected based on the corneal tomography and aberrometry data. The on-eye performance of the lens was evaluated using aberrometry (4-mm pupil), over refraction, VA, and VAS. The standardized asymmetric SCL improved the best spectacle-corrected VA from -0.07 ± 0.09 to -0.11 ± 0.08 logMAR (P < 0.05) and the mean VAS score from 66.2 ± 21.8 to 75.4 ± 20.5 (P < 0.05). Vertical coma decreased significantly (-0.50 ± 0.36 μm without SCL; -0.36 ± 0.34 μm with SCL; P < 0.01). In subgroup analysis, subjects in the high VAS group (score ≥ 75) accounted for 70% of all subjects, and this was the group in which the vertical coma decreased significantly from the level without the lens. A standardized asymmetric SCL can reduce HOAs and improve vision quality when compared with spectacles in patients with keratoconus who wear rigid gas-permeable lenses.