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Here we analyzed the intensity profile properties of the Laguerre-Gaussian (LG) mode laser beams, to facilitate the intracavity intensity modulation for high-order LG mode laser output. The commonly used definitions of ring-like beam size are discussed, including the second moment of light intensity, power in the bucket, and the peak intensity radius of the ring-like beam. The differences between these methods underscore the importance of selecting appropriate beam size definitions when estimating the mode order, which is particularly worthy of attention when employing certain mode-selection techniques, such as using a defect spot, an aperture, or inducing spherical aberration (SA), to achieve high-order mode outputs. In the experiment, high-order mode LG 0,± m output were obtained by utilizing the SA of a short-focal lens in the cavity of an end-pumped Nd:YVO 4 laser at 1064 nm. The highest angular indices m reached 355, which is the highest order of LG mode output obtained directly from a laser cavity. The experimental relationship between the mode-order and cavity parameters matched well with the theoretical results, validating the analysis of the intensity profile properties. [ABSTRACT FROM AUTHOR]

• Mie theory and multipole expansion approach for interaction of beam with nanoparticles. • Scattering of tightly focused beams under spherical aberration through nanoparticles. • Results on the spherical aberration and defocusing in a balancing condition. • Analysis of radial and tangential components of near-field intensity enhancement. The plasmonic response of a spherically symmetric nanoparticle is theoretically analysed using the Mie theory and multipole expansion for a tightly focused beam under the spherical aberration and defocusing. It is observed that the spherical aberrations present in the system amend the absorption and scattering efficiency of the nanoparticles, and the electromagnetic field around the nanoparticle. An enhancement in the near-field intensity appears due to excitement of plasmons on the surface of a nanoparticle and this is further increased for a beam under spherical aberration. In contrast to the aberration free case where radial component was dominating in the near field intensity enhancement, presence of spherical aberration in the focusing system significantly enhances the contribution of the tangential component in addition to the radial component. Defocusing aberration is also introduced to compensate the effect of spherical aberration and results are presented for the balancing condition. [ABSTRACT FROM AUTHOR]

To assess accommodation and spherical aberration changes during one year of orthokeratology lens wear and one month after lens cessation. A prospective, randomized, longitudinal study was conducted on forty-seven young healthy subjects at the Optometry Clinic of the Complutense University of Madrid (Spain). Non-cycloplegic refraction, high and low uncorrected visual acuity, high and low best corrected visual acuity, accommodative lag, horizontal near phoria, corneal topography, and high-order aberrations were performed at baseline, 1-day, 1-week, 1-, 6- and 12-months of lens wear and after one month of wash out period. p < 0.05 was considered as statistically significant. Spherical equivalent refraction (SE) was −3.23 ± 1.57D at baseline and –0.36 ± 0.64D after 12-months of lens wear, while accommodative lag changed from 0.53 ± 0.39D to 0.15 ± 0.29D after one year of lens wear. No significant differences were found when comparing SE at baseline and after one month of lens cessation (p > 0.05). A high correlation was found between the accommodative lag at baseline and after 12 M of lens wear. 22 out of 25 subjects with exophoria at baseline showed a significant reduction in the deviation at 12-months (p < 0.05). Total spherical aberration increased during all visits due to the lens wear (p < 0.05) although internal spherical aberration showed a significant decrease for 1-week, 1-month and 12-month visits (p < 0,05). Orthokeratology lenses may change the accommodative response of the patient as a reduction on accommodative lag on exophoric patients and an overall increase on the internal spherical aberrations was found during treatment but return to nearly baseline values when cessation. [ABSTRACT FROM AUTHOR]

The purpose of this review is to evaluate the usefulness of corneal topography to select premium intraocular lenses (IOLs), including aspherical IOLs, toric IOLs, and multifocal IOLs, in refractive cataract surgery. Corneal topography can detect corneal regular astigmatism, corneal irregular astigmatism (higher-order aberrations [HOAs]) including spherical aberration, and corneal shape abnormalities after corneal refractive surgery. Surgeons can explain to the patients with significant corneal HOAs about its effect on postoperative visual function before surgery. Multifocal IOLs should not be selected for such eyes. For eyes with abnormal corneal shape, appropriate IOL power calculation formulae can be applied. In the case of toric IOLs, regular astigmatism and corneal HOAs should be checked. Before implanting an aspheric IOL, it is ideal to confirm spherical aberration of the cornea is not below the normal range. Because corneal HOAs, abnormal corneal shape after corneal refractive surgery, corneal regular astigmatism, and corneal spherical aberration increase postoperative refractive errors and poor vision quality with premium IOLs, corneal topography before cataract surgery is helpful in screening patients who are not appropriate candidates for premium IOLs. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Optometry is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Holographic beam modulation is widely applied in optical tweezers, hard-brittle material marking, high-density storage, etc. To generate high-fidelity arbitrary 3-dimensional (3D) parallel multifoci inside the material, the spherical aberration compensated automatic differentiation (SACAD) algorithm is presented. All polarization components are included and the spherical aberration compensation is embedded in the physical model. The technique of automatic differentiation is used in the error backpropagation procedure, ensuring efficient parallel computing of pixel-by-pixel gradients. In several simulation tests, the root mean square errors of the generated 3D multifoci distributions are all less than 0.01 and the diffraction efficiencies are all beyond 90%, outperforming the results of the established algorithms. In the experiments, we have verified the advantage of SACAD algorithm in complicated 3D internal marking with spherical aberration compensation. Since the SACAD algorithm can achieve high fidelity and efficiency phase retrieval with a straightforward procedure, it has the potential to become a well-received solution for internal parallel beam modulation. • Comprehensive algorithm for beam modulation with built-in aberration compensation. • Surpassing the GSW algorithm in diffraction efficiency and fidelity. • Compatible with high efficiency parallel computing using automatic differentiation. • High fidelity and low interlayer crosstalk in internal laser direct writing. [ABSTRACT FROM AUTHOR]

In this paper, we propose and experimentally demonstrate a tunable liquid lens integrated with an aspherical surface for spherical aberration and distortion compensation. Through optimizing the aspherical surface's morphology, the spherical aberration and distortion can be significantly reduced. The root mean square spot size at focus is distinctly reduced from 55. 7 μ m to 2. 095 μ m after performing optimum optimization. The tunable liquid lens is integrated with the aspheric surface with 6 mm clear aperture and 19.2 mm minimum focal length and demonstrate the improvement in optical performance over the conventional lens without an aspheric surface over a focal length range. Its applications in microscope system and tunable-focus eyeglasses are foreseeable. [ABSTRACT FROM AUTHOR]

Based on the peripheral refractive theory, this study designed a contact lens which can change the peripheral refraction of the retina, and established a retinal image system that can analysis the refractive state of the eyeball. The Monte-Carlo ray trace modeling was used to analyze the retinal images under different refractive conditions. The calculation of the power vector of refractive state was optimized for judging the corrective effect. The purpose of this study is to control the development of myopia for suppress the change of axis oculi when the eyeball supported in relative peripheral myopia or emmetropia by using contact lens. The results show that the model of peripheral refractive lenses with fourth-order spherical aberration constructed in this study can be used to control myopia and can achieve excellent corrective effect. [ABSTRACT FROM AUTHOR]

Highlights • Quantum electron microscopy (QEM) could reduce sample radiation damage. • QEM exploits an interaction-free measurement scheme in an electron cavity. • A linear electron cavity design is presented and characterized through simulation. • Approaches to correct spherical aberrations inside the cavity are proposed and validated through simulation. Abstract Quantum electron microscopy (QEM) is a measurement approach that could reduce sample radiation damage, which represents the main obstacle to sub-nanometer direct imaging of molecules in conventional electron microscopes. This method is based on the exploitation of interaction-free measurements in an electron resonator. In this work, we present the design of a linear resonant electron cavity, which is at the core of QEM. We assess its stability and optical properties during resonance using ray-tracing electron optical simulations. Moreover, we analyze the issue of spherical aberrations inside the cavity and we propose and verify through simulation two possible approaches to the problem. Finally, we discuss some of the important design parameters and constraints, such as conservation of temporal coherence and effect of alignment fields. [ABSTRACT FROM AUTHOR]

Highlights • Ptychography provides much stronger robustness to temporal incoherence than HRTEM. • For a given aperture size, ptychography provides double the resolution of HRTEM. • The bandpass contrast transfer function of ptychography facilitates interpretability. • Under equivalent conditions ptychographic imaging is much clearer than HRTEM imaging. Abstract Radiation damage places a fundamental limitation on the ability of microscopy to resolve many types of materials at high resolution. Here we evaluate the dose efficiency of phase contrast imaging with electron ptychography. The method is found to be far more resilient to temporal incoherence than conventional and spherical aberration optimized phase contrast imaging, resulting in significantly greater clarity at a given dose. This robustness is explained by the presence of achromatic lines in the four dimensional ptychographic dataset. [ABSTRACT FROM AUTHOR]

Abstract The annular differential phase contrast (ADPC) mode in a third-order spherical aberration-corrected scanning transmission electron microscope (STEM) has recently been realized at an operating voltage of 300 kV by inserting a physical Fresnel phase plate in front of the objective lens and by using a detector geometry which matches that of the Fresnel phase plate [1]. By image calculation we explore the feasibility of this mode for the voltage range of 20–80kV. Alternatively, we mimic the Fresnel phase plate material-free with the help of the adjustable aberrations of the corrector. The additional correction of chromatic aberration, fifth-order spherical aberration and image spread improves significantly the resolution and contrast. Under these advanced conditions it is possible to achieve optical sectioning in the ADPC mode with atomic resolution and a depth of field shorter than 3 Å for an accelerating voltage of 30 kV. Moreover, we show that the contrast obtained in the ADPC mode is clearly superior over the contrast in incoherent bright-field (IBF) and high-angle annular dark-field (HAADF), the two other common methods in STEM. We propose that with the advanced ADPC method applied in STEM, the investigation of the inner structure of thick samples will be possible without slicing. [ABSTRACT FROM AUTHOR]

To investigate by using computational simulations the optical impact of the change in the vault of two geometries of scleral contact lenses (SCLs). Ray-tracing simulations were performed using specialized software in three eye models with different levels of primary SA (6 mm pupil). Two different geometries of SCL were used in such simulations characterized by the conic constants of the anterior surface of the lens (K1, −0.1 and −0.3). Likewise, the fitting of the SCL was simulated for different vaults (50–250 µm). The impact on the quality of the images through the eye models was assessed by analyzing the modulation transfer function (MTF) at different spatial frequencies (10 Lp/mm, 30 Lp/mm, and 50 Lp/mm). This impact was not only simulated for a distant object, but also for intermediate and near objects (vergence demands from 0.00 to 3.00 D). All these optical simulations were performed assuming a centered SCL, but also assuming a downward vertical decentration of 0.5 mm. The thinnest vault (50 µm) provided the best ocular optical quality in all three eye models for low vergence demands. For medium and high vergence demands, Lens 1 (K1 = −0.3, K2 = −0.4) resulted in a considerable improvement in optical quality in Eye 2 (C 4 0 = −0.078 µm), while for eyes 1 (C 4 0 = 0.408 µm) and 3 (C 4 0 = −0.195 µm), this improvement only tended to happen for medium vergence demands. Overall, all the aberrations increased after lens fitting. Lens decentration did not cause significant variations in the results obtained with the well-centered lenses. Changes in the vault of a SCL have an impact on the optical quality achieved for different vergence demands independently on the level of SA of the eye in which it is fitted. The clinical relevance of such impact should be investigated further. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Optometry is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nearly eighty years ago, Scherzer showed that rotationally symmetric, charge-free, static electron lenses are limited by an unavoidable, positive spherical aberration. Following a long struggle, a major breakthrough in the spatial resolution of electron microscopes was reached two decades ago by abandoning the first of these conditions, with the successful development of multipole aberration correctors. Here, we use a refractive silicon nitride thin film to tackle the second of Scherzer's constraints and demonstrate an alternative method for correcting spherical aberration in a scanning transmission electron microscope. We reveal features in Si and Cu samples that cannot be resolved in an uncorrected microscope. Our thin film corrector can be implemented as an immediate low cost upgrade to existing electron microscopes without re-engineering of the electron column or complicated operation protocols and can be extended to the correction of additional aberrations. [ABSTRACT FROM AUTHOR]

In our previous works, we have proposed N -SYLC ( N -fold sy mmetric l ine c urrents) models for aberration correction. In this paper, we propose “in-lens N -SYLC” model, where N -SYLC overlaps rotationally symmetric lens. Such overlap is possible because N -SYLC is free of magnetic materials. We analytically prove that, if certain parameters of the model are optimized, an in-lens 3-SYLC ( N  = 3) doublet can correct 3rd order spherical aberration. By computer simulation, we show that the required excitation current for correction is less than 0.25 AT for beam energy 5 keV, and the beam size after correction is smaller than 1 nm at the corrector image plane for initial slope less than 4 mrad. [ABSTRACT FROM AUTHOR]

A laser focal intensity profiling method based on the forward scattering from a nanoparticle is demonstrated for in situ measurements using a laser focusing system with six microscope objective lenses with different numerical apertures ranging from 0.15 to 1.4. The measured profiles showed Airy disc patterns although their rings showed some imperfections due to aberrations and misalignment of the test system. The dipole radiation model revealed that the artefact of this method was much smaller than the influence of the deterioration in the experimental system; a condition where no artefact appears was predicted based on proper selection of measurement angles. [ABSTRACT FROM AUTHOR]

The purpose of this work was to find plausible predictors among optical parameters that may explain the inter-individual differences in subjective amplitude of accommodation not explained by age. An exploratory multivariable regression analysis was carried out retrospectively on a dataset with 180 eyes from 97 subjects (ages ranged from 20 to 58years). Subjective amplitudes of accommodation were recorded with the use of a custom-made Badal system. A commercial aberrometer was used to obtain each eye's wavefront during the full range of accommodation. The plausible predictors under study were pupil diameter in the unaccommodated eye, its reduction with accommodation; fourth- and six-order Zernike spherical aberration, their reduction with accommodation, and subjective refraction. At a significance level of 0.05, only fourth- and sixth-order Zernike spherical aberration were found to be predictors of subjective amplitude of accommodation not explained by age, each explaining on their own less than 5% of the variance, and about 9% together. All other optical parameters explained less than 2%. Spherical aberration did not explain the greater variability for younger eyes than for older eyes. The remainder variability in amplitude of accommodation not explained by age or spherical aberration was about ±2.6D for 20year-old subjects, ±1.5D for 40year-old subjects, and about ±0.6D for 55year-old subjects. Optical factors do not seem to account for much of the inter-individual differences in subjective amplitude of accommodation. Most of the variability not explained by age must be due to anatomical differences and physiological, psychological, or other factors. [ABSTRACT FROM AUTHOR]

An aberration-free focusing reflector (AFR) for acoustic waves is proposed with the aim to eliminate spherical aberration and coma simultaneously. Meanwhile, the AFR can focus acoustic waves with low dispersion in a wide frequency range of 14–50 kHz. The broadband aberration-free focusing effect is originated from an elliptical reflection phase gradient profile, which is achieved by milling different depths of axisymmetric grooves on a planoconcave-like brass plate using the ray theory. Theoretical and numerical results are in good agreement. The designed AFR can find broad engineering, industrial and medical applications. [ABSTRACT FROM AUTHOR]

We present a high precision deflectometry system (DS) controlled deformable mirror (DM) solution for optical system. Different from wavefront and non-wavefront system, the DS and the DM are set to be an individual integrated DCDM unit and can be installed in one base plate. In the DCDM unit, the DS can directly provide the influence functions and surface shape of the DM to the industrial computer in any adaptive optics system. As an integrated adaptive unit, the DCDM unit could be put into various optical systems to realize aberration compensation. In this paper, the configuration and principle of the DCDM unit is introduced first. Theoretical simulation on the close-loop performance of the DCDM unit is carried out. Finally, a verification experiment is proposed to verify the compensation capability of the DCDM unit. [ABSTRACT FROM AUTHOR]

Subaperture stitching test in combination of the reconfigurable optical null we proposed recently provides flexible solutions to various surfaces including convex aspheres and even aspheres of large aperture. However it is challenging for the stitching optimization to get the real surface error because the surface error is strongly coupled with misalignment-induced aberrations in near-null subaperture measurements. Aiming at this challenge, we first figure out the property of aberrations induced by misalignment of optical null or test surface. It shows that identical misalignment of the optical null introduces nearly identical aberrations to subapertures with different off-axis distances, while misalignment of the test surface introduces little aberrations to the central subaperture. The stitching algorithm is then proposed with focus on decoupling surface error and induced aberrations. The major step is to calibrate out the effect of misaligned near-null optics before stitching optimization by using the central subaperture measurement. We also present the through-the-back null test for the purpose of cross test. The axial distance is precisely monitored by a low coherence interferometer, which enables accurate determination of the spherical aberration component of surface error. Final experimental results show consistent spherical aberration obtained by stitching test and by the through-the-back null test. It is a big step towards instrumentation of subaperture stitching test for aspheres with rather big amount of misalignments in surface metrology practice. [ABSTRACT FROM AUTHOR]

Scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDS) is a common technique for chemical mapping in thin samples. Obtaining high-resolution elemental maps in the STEM is jointly dependent on stepping the sharply focused electron probe in a precise raster, on collecting a significant number of characteristic X-rays over time, and on avoiding damage to the sample. In this work, 80 kV aberration-corrected STEM-EDS mapping was performed on ordered precipitates in aluminium alloys. Probe and sample instability problems are handled by acquiring series of annular dark-field (ADF) images and simultaneous EDS volumes, which are aligned and non-rigidly registered after acquisition. The summed EDS volumes yield elemental maps of Al, Mg, Si, and Cu, with sufficient resolution and signal-to-noise ratio to determine the elemental species of each atomic column in a periodic structure, and in some cases the species of single atomic columns. Within the uncertainty of the technique, S and β” phases were found to have pure elemental atomic columns with compositions Al 2 CuMg and Al 2 Mg 5 Si 4 , respectively. The Q’ phase showed some variation in chemistry across a single precipitate, although the majority of unit cells had a composition Al 6 Mg 6 Si 7.2 Cu 2 . [ABSTRACT FROM AUTHOR]

We designed a crystalline microstructure during cataract lesions and calculated the aberration value of the eye by using ray trace modeling to identify the corresponding spherical aberration, coma aberration, and trefoil aberration value under different pathological-change degrees. The mutual relationship between microstructure and aberration was then discussed using these values. Calculation results showed that with increased layer number of microstructure, the influence of aberration value on spherical aberration was the greatest. In addition, the influence of a relatively compact microstructure on spherical aberration and coma aberration was small, but that on trefoil aberration was great. [ABSTRACT FROM AUTHOR]

A novel doublet liquid variable-focus lens with simple structure was designed and fabricated for spherical aberration correction under the condition of small focal length, which was 11.8 mm to 25 mm. By changing the shape of the two PDMS membranes respectively, the focal length of the proposed lens was changed and the spherical aberration was corrected. The size of the entire lens was very small and overall structure of the proposed lens was presented, as well as the design process. The ZEMAX software was used to optimize the optical parameters of the proposed lens. The deformation of the PDMS membranes was measured and fitted by spherical curve. The longitudinal spherical aberration was measured in experiments and compared with the optimal design results. In order to weaken the gravity effect, we designed the shape of the rear PDMS membrane and presented the detailed description of the fabrication process. [ABSTRACT FROM AUTHOR]

Imaging characteristics of wavefront coding systems in the presence of spherical aberration are analyzed by using ray aberration approach. The analytical expressions for ray aberration, the boundary of ray map and the size of spot diagram of a wavefront coding system in the presence of defocus and spherical aberration are obtained by wave aberration theory. The effect of spherical aberration on imaging performance of wavefront coding systems with a cubic phase mask is presented by ray aberration and spot diagram. The results show that the wavefront coding systems have a high tolerance to spherical aberration through a given defocus range. [ABSTRACT FROM AUTHOR]

A novel compact focus tunable liquid-filled lens using electromagnetic actuation method is presented. It consists of a specially designed elastic membrane that incorporates an annular ridge structure and non-uniform thickness contour for actuator integration and dynamically improving optical quality over the whole focal length tuning range, respectively. Moreover, a custom-designed moving coil type electromagnetic actuator together with a refractive index matching strategy between the filling liquid and the membrane are adopted for providing bidirectional, wide-range focus tuning capability. For proof-of-concept demonstration, a new process combining injection molding with 3D printing is developed to fabricate the proposed lens with effective aperture size of 4 mm with high reliability and repeatability. Nearly symmetric focal length tuning from infinity to ± 40 mm and reduced spherical aberration characteristic are experimentally disclosed for the as-fabricated device, and its application in dynamic focusing imaging is also successfully performed. [Display omitted] • A customized electromagnetic actuation mechanism is designed. • A refractive index matching strategy is used for wide-range focus tuning. • A specially designed elastic membrane is used for improving dynamic optical quality. • Nearly symmetric focal length tuning from infinity to ± 40 mm is achieved. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this report was to compare corneal topographic measurements and anterior high order corneal aberrations in eyes with keratoconus and normal eyes by using Scheimpflug-Placido topography.Methods: Eighty cases diagnosed with mild (group 1), moderate (group 2), and advanced (group 3) stage keratoconus (KC) according to Amsler-Krumeich Classification and 81 healthy (control group) cases were retrospectively examined. The mean keratometric measurements (as both diopters (Kavg) and mm values (mmavg)), central corneal thickness values (CCT), high order aberration (HOA), total wavefront aberration (TWA), coma, trefoil, and spherical aberration measurements were performed using Sirius topography equipment. The topographic values were compared between the groups.Results: There were 25 cases in group 1 KC (15.5%), 34 cases in group 2 KC (21.1%), 21 cases in group 3 KC (13.1%), and 81 cases (50.3%) in the control group. In terms of mean age and gender distributions, there was no statistically significant difference between the groups (p>0.05). However, there was significant difference between the groups in terms of Kavg, CCT, HOA, TWA, coma, trefoil, and spherical aberration values (p<0.01). Mean HOA, TWA, coma, trefoil, and spherical aberration values were observed to increase with the severity of KC disease.Conclusions: Anterior high order corneal aberrations were significantly increased in eyes with moderate and advanced keratoconus. Anterior high order corneal aberration measurements are a useful tool to guide the physician in diagnosis and classification of keratoconus. [ABSTRACT FROM AUTHOR]

It has been shown that N -fold symmetric line current (henceforth denoted as N -SYLC) produces 2 N -pole magnetic fields. In this paper, a threefold symmetric line current (N3-SYLC in short) is proposed for correcting 3rd order spherical aberration of round lenses. N3-SYLC can be realized without using magnetic materials, which makes it free of the problems of hysteresis, inhomogeneity and saturation. We investigate theoretically the basic properties of an N3-SYLC configuration which can in principle be realized by simple wires. By optimizing the parameters of a system with beam energy of 5.5 keV, the required excitation current for correcting 3rd order spherical aberration coefficient of 400 mm is less than 1AT, and the residual higher order aberrations can be kept sufficiently small to obtain beam size of less than 1 nm for initial slopes up to 5 mrad. [ABSTRACT FROM AUTHOR]

In a medium energy beam transport line transverse rms emittance growth associated with spherical aberration is analysed. An analytical expression is derived for beam optics in a solenoid field considering terms up to the third order in the radial displacement. Two important phenomena: effect of spherical aberrations in axial-symmetric focusing lens and influence of nonlinear space charge forces on beam emittance growth are discussed for different beam distributions. In the second part nonlinear effect associated with chromatic aberration that describes the growth of emittance and distortion of phase space area is discussed. [ABSTRACT FROM AUTHOR]

We present theoretical estimates of the mean coefficients of spherical and chromatic aberration for low energy photoemission electron microscopy (PEEM). Using simple analytic models, we find that the aberration coefficients depend primarily on the difference between the photon energy and the photoemission threshold, as expected. However, the shape of the photoelectron spectral distribution impacts the coefficients by up to 30%. These estimates should allow more precise correction of aberration in PEEM in experimental situations where the aberration coefficients and precise electron energy distribution cannot be readily measured. [ABSTRACT FROM AUTHOR]

We here report a new design of a double air-slot or pole-gap type, axially thin, shielded solenoid with lower spherical aberration than conventional single pole-gap type solenoids. The net on-axis field from two optimally distanced pole gaps reduces the spherical aberration. The working principle of the model is also given by a pair of coaxial, in-air, identical current loops which can have lower spherical aberration than a single current loop. The new design is useful to achieve low spherical aberration in axially thin shielded solenoids. [ABSTRACT FROM AUTHOR]

In this study, an optimal contact lens design for myopia and astigmatism eyes was proposed. In addition to the optical parameters of the human eye, the physiologically relevant parameters of design have become the subject of increased focus. If we compacting overall volume size, the value of spherical aberration (SA) at wide radius of contact lens seems lower. If we corrected the design to improve the value of SA, modulation transfer function (MTF) and coma aberration (TCO) value would become lower relatively. Hence we integrated the optimal method of Taguchi method and mathematical analysis scheme of principal component analysis (PCA) to optimize the multiple quality characteristics (SA, TCO and MTF) of the contact lens. By combining Taguchi and PCA methods, a set of optimum design parameters was well selected to balance the values of SA, TCO and MTF that improve the SA 25.63%, TCO 91.88% and MTF 2.4% than commercial optical design software of CODE V. [ABSTRACT FROM AUTHOR]

The [1 1 0] cross-sectional samples of 3 C -SiC/Si (0 0 1) were observed with a spherical aberration-corrected 300 kV high-resolution transmission electron microscope. Two images taken not close to the Scherzer focus condition and not representing the projected structures intuitively were utilized for performing the deconvolution. The principle and procedure of image deconvolution and atomic sort recognition are summarized. The defect structure restoration together with the recognition of Si and C atoms from the experimental images has been illustrated. The structure maps of an intrinsic stacking fault in the area of SiC, and of Lomer and 60° shuffle dislocations at the interface have been obtained at atomic level. [ABSTRACT FROM AUTHOR]

Imaging of light atoms has always been a challenge in high-resolution electron microscopy. Image resolution is mainly limited by lens aberrations, especially the spherical aberration of the objective lens. Image deconvolution could correct for the image distortion by lens aberrations and restore the structure projection, the resolution of which is limited by the information limit of the microscope. Electron diffraction unrestricted by lens aberrations could overcome this resolution limit. Here we show a combination of electron diffraction and image deconvolution to reveal simultaneously the atomic columns of O and considerably heavier Sm at a very close distance (1.17 Å) in iron-based superconductor SmFeAsO 0.85 F 0.15 using a conventional 200 kV electron microscope. The approach used here, starting from an image and an electron diffraction pattern, has an advantage for those radiation-sensitive samples. Besides, it can be applied to simultaneously imaging light and heavy atoms, even though they have a big difference in atomic number and a much smaller atomic distance than the microscope resolution. [ABSTRACT FROM AUTHOR]

Aberration correction in scanning/transmission electron microscopy (S/TEM) owes much to the efforts of a small dedicated group of innovators. Leading that frontier has been Prof. Harald Rose. To date his leadership and dynamic personality has spearheaded our ability to leave behind many of the limitations imposed by spherical aberration ( C s ) in high resolution phase contrast imaging. Following shortly behind, has been the development of chromatic aberration correction ( C c ) which augments those accomplishments. In this paper we will review and summarize how the combination of C s / C c technology enhances our ability to conduct hyperspectral imaging and spectroscopy in today׳s and future computationally mediated experiments in both thin as well as realistic specimens in vacuo and during in-situ/environmental experiments. [ABSTRACT FROM AUTHOR]

Here, we present a numerical post-processing method for removing the effect of anti-symmetric residual aberrations in high-resolution transmission electron microscopy (HRTEM) images of weakly scattering 2D-objects. The method is based on applying the same aberrations with the opposite phase to the Fourier transform of the recorded image intensity and subsequently inverting the Fourier transform. We present the theoretical justification of the method, and its verification based on simulated images in the case of low-order anti-symmetric aberrations. Ultimately the method is applied to experimental hardware aberration-corrected HRTEM images of single-layer graphene and MoSe 2 resulting in images with strongly reduced residual low-order aberrations, and consequently improved interpretability. Alternatively, this method can be used to estimate by trial and error the residual anti-symmetric aberrations in HRTEM images of weakly scattering objects. [ABSTRACT FROM AUTHOR]

This paper lists simple closed-form expressions estimating aberration coefficients (defocus, astigmatism, three-fold astigmatism, coma / misalignment, spherical aberration) on the basis of image shift or diffractogram shape measurements as a function of injected beam tilt. Simple estimators are given for a large number of injected tilt configurations, optimal in the sense of least-squares fitting of all the measurements, and so better than most reported previously. Standard errors are given for most, allowing different approaches to be compared. Special attention is given to the measurement of the spherical aberration, for which several simple procedures are given, and the effect of foreknowledge of this on other aberration estimates is noted. Details and optimal expressions are also given for a new and simple method of analysis, requiring measurements of the diffractogram mirror axis direction only, which are simpler to make than the focus and astigmatism measurements otherwise required. [ABSTRACT FROM AUTHOR]

We demonstrate a method to achieve high efficiency phase contrast imaging in aberration corrected scanning transmission electron microscopy (STEM) with a pixelated detector. The pixelated detector is used to record the Ronchigram as a function of probe position which is then analyzed with ptychography. Ptychography has previously been used to provide super-resolution beyond the diffraction limit of the optics, alongside numerically correcting for spherical aberration. Here we rely on a hardware aberration corrector to eliminate aberrations, but use the pixelated detector data set to utilize the largest possible volume of Fourier space to create high efficiency phase contrast images. The use of ptychography to diagnose the effects of chromatic aberration is also demonstrated. Finally, the four dimensional dataset is used to compare different bright field detector configurations from the same scan for a sample of bilayer graphene. Our method of high efficiency ptychography produces the clearest images, while annular bright field produces almost no contrast for an in-focus aberration-corrected probe. [ABSTRACT FROM AUTHOR]

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Increasing evidences suggest that nanoscale zero-valent iron (nZVI) is an effective agent for treatment and removal of selenium from water. For example, 1.3 mM selenite was quickly removed from water within 3 min with 5 g/L nZVI. In this work, reaction mechanisms of selenite [Se(IV)] in a single core–shell structured nanoscale zero-valent iron (nZVI) particle were studied with the method of spherical aberration corrected scanning transmission electron microscopy (Cs-STEM) integrated with X-ray energy dispersive spectroscopy (XEDS). This method was utilized to visualize solid phase translocation and transformation of Se(IV) such as diffusion, reduction, deposition and the effect of surface defects in a single nanoparticle. Se(IV) was reduced to Se(-II) and Se(0), which then formed a 0.5 nm layer of selenium at the iron oxide-Fe(0) interface at a depth of 6 nm from the surface. The results provided near atomic-resolution proof on the intraparticle diffusion-reduction of Se(IV) induced by nZVI. The STEM mapping also discovered that defects on the surface layer accelerate the diffusion of selenium and increase the capacity of nZVI for selenium sequestration. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this study was to investigate the optical zone power profile of the most commonly prescribed soft contact lenses to assess their potential impact on peripheral refractive error and hence myopia progression. Methods The optical power profiles of six single vision and ten multifocal contact lenses of five manufacturers in the powers −1.00 D, −3.00 D, and −6.00 D were measured using the SHSOphthalmic (Optocraft GmbH, Erlangen, Germany). Instrument repeatability was also investigated. Results Instrument repeatability was dependent on the distance from the optical centre, manifesting unreliable data for the central 1 mm of the optic zone. Single vision contact lens measurements of −6.00 D lenses revealed omafilcon A having the most negative spherical aberration, lotrafilcon A having the least. Somofilcon A had the highest minus power and lotrafilcon A the biggest deviation in positive direction, relative to their respective labelled powers. Negative spherical aberration occurred for almost all of the multifocal contact lenses, including the centre-distance designs etafilcon A bifocal and omafilcon A multifocal. Lotrafilcon B and balafilcon A seem to rely predominantly on the spherical aberration component to provide multifocality. Conclusions Power profiles of single vision soft contact lenses varied greatly, many having a negative spherical aberration profile that would exacerbate myopia. Some lens types and powers are affected by large intra-batch variability or power offsets of more than 0.25 dioptres. Evaluation of power profiles of multifocal lenses was derived that provides helpful information for prescribing lenses for presbyopes and progressing myopes. [ABSTRACT FROM AUTHOR]

Objective To evaluate to what extent the modification of corneal asphericity to induce spherical aberration (SA) can improve the depth of focus and to determine whether preoperative adaptive optics assessment (Voptica SL) can predict an optimal SA value for each patient. Design Comparative, prospective clinical trial with paired eye control. Participants Patients ≥45 years old who are hyperopic from +1.00 to +2.50 diopters (D), with eyes suitable for LASIK surgery. Intervention Bilateral hyperopic LASIK surgery using a 200-Hz Allegretto excimer laser. The dominant eye was operated using a conventional profile. The nondominant eye was programmed with an aspheric ablation profile and −0.75 D monovision. Main Outcome Measures Primary outcome was the correlation between postoperative SA and depth of focus, defined as the pseudo-accommodation value (PAV = [1/reading distance {m}] – minimum addition [D]). Main secondary outcome was the comparison of depth of focus between patients with an induced SA close to the optimal one (group 1), patients with an induced SA far from the optimal one (group 2), and patients for whom SA induction did not increase the depth of focus (control group). Results We included 76 patients. Between preoperative and postoperative assessment, the mean increase of distance-corrected PAV for near vision was +0.25±0.64 D ( P < 0.001) for dominant eyes and +0.63±0.55 D ( P < 0.001) for nondominant eyes. As the level of negative or positive postoperative SA increased, PAV for intermediate and near vision increased. Among the 37 eyes that followed the preoperative adaptive optics assessment, the mean PAV increase at near was significantly higher ( P < 0.05) in group 1 (0.93±0.50 D) than in group 2 (0.46±0.42 D) and than in the control group (0.35±0.32 D). The mean optimal SA value determined by the dynamic simulation procedure to optimize the depth of focus was −0.18±0.13 μm at 4.5 mm. Conclusions Aspheric hyperopic LASIK can increase the depth of focus without impairing far vision, but this benefit would be maximal and reproducible if we could define and achieve an optimal SA value determined by preoperative assessment using an adaptive optics instrument. [ABSTRACT FROM AUTHOR]

In this paper attention is given to the effects of primary spherical aberration on the cylindrical polarized vortex beam based on the vector diffraction theory. It is observed that by properly choosing the polarization angle and topological charge one can obtain many novel focal patterns suitable for optical tweezers, laser printing and material process. However, it is observed that the focusing objective with spherical aberration generates structural modification and positional shift of the generated focal structure. [ABSTRACT FROM AUTHOR]

This paper focuses upon the development of an efficient method for design optimization of an imaging payload of a remote sensing satellite. In this paper, the design of the imaging payload is defined as a multi-objective optimization problem. In the formulation of the problem, the aperture diameter and quality factor are used as a design variable and constraints, respectively, with maximization of signal to noise ratio ( SNR ) and minimization of the spherical aberration values. This paper presents a new method of involving the above two contradictorily objective functions. The approach adapted in this paper achieves the prescribed degree of quality of images and design constraints, whilst minimizing the weight of the payload in comparison with the conventional experimental approaches. The optimization algorithm used to solved the problem based on the genetic algorithms. Results obtained in this study, show that the method introduced in this paper provides an effective way of improving imaging payload in the design of a space system. [ABSTRACT FROM AUTHOR]

Abstract: Trapping a single aerosol using optical tweezers could be of great importance for environmental sciences. Though a single nanoparticle as small as 10nm is successfully trapped in aqueous media using optical tweezers, due to spherical aberration only large clusters of nanoparticles were stably trapped in air. In this paper we provide our theoretical and experimental results on optimized trapping of aerosols as small as 400nm in radius by the introduction of an extra spherical aberration source in order to minimize the total spherical aberration of the system. Our method allows for trapping of high refractive index particles such as polystyrene beads in air. It also provides considerably large trappable depth range which endows in-depth trapping. Our theoretical and experimental results are in very good agreement. [Copyright &y& Elsevier]

Background Investigate the impact of natural N- or C-terminal post-translational truncations of lens mature fiber cell Aquaporin 0 (AQP0) on water permeability (Pw) and cell-to-cell adhesion (CTCA) functions. Methods The following deletions/truncations were created by site-directed mutagenesis (designations in parentheses): Amino acid residues (AA) 2-6 (AQP0-N-del-2-6), AA235-263 (AQP0-1-234), AA239-263 (AQP0-1-238), AA244-263 (AQP0-1-243), AA247-263 (AQP0-1-246), AA250-263 (AQP0-1-249) and AA260-263 (AQP0-1-259). Protein expression was studied using immunostaining, fluorescent tags and organelle-specific markers. Pw was tested by expressing the respective complementary ribonucleic acid (cRNA) in Xenopus oocytes and conducting osmotic swelling assay. CTCA was assessed by transfecting intact or mutant AQP0 into adhesion-deficient L-cells and performing cell aggregation and adhesion assays. Results AQP0-1-234 and AQP0-1-238 did not traffic to the plasma membrane. Trafficking of AQP0-N-del-2-6 and AQP0-1-243 was reduced causing decreased membrane Pw and CTCA. AQP0-1-246, AQP0-1-249 and AQP0-1-259 mutants trafficked properly and functioned normally. Pw and CTCA functions of the mutants were directly proportional to the respective amount of AQP0 expressed at the plasma membrane and remained comparable to those of intact AQP0 (AQP0-1-263). Conclusions Post-translational truncation of N- or C-terminal end amino acids does not alter the basal water permeability of AQP0 or its adhesive functions. AQP0 may play a role in adjusting the refractive index to prevent spherical aberration in the constantly growing lens. [ABSTRACT FROM AUTHOR]

Purpose: To compare postoperative visual acuity and higher-order aberrations (HOAs) after femtosecond lenticule extraction (FLEX) and after small-incision lenticule extraction (SMILE). Methods: Medical records of refractive lenticule extraction patients were retrospectively reviewed. Twenty patients were treated with FLEX. A comparable group of 20 SMILE patients were retrospectively identified. Only one eye of each patient was randomly chosen for the study. Visual acuity, subjective manifest refraction and corneal topography before and 6 months after the surgery were analyzed for both groups. Total HOAs, spherical aberrations, coma and trefoil were calculated from topography data over the 4- and 6-mm-diameter central corneal zone. Results: The mean preoperative SE was -4.03 ± 1.61 in the SMILE group and -4.46 ± 1.61 in the FLEX group. One year after surgery, the mean SE was -0.33 ± 0.25 in the SMILE group and -0.31 ± 0.41 in the FLEX group (p = 0.86). In the SMILE group a greater number of eyes were within ±0.50 D of the target refraction (95% versus 75%); however, the difference was not statistically significant (p = 0.18). Furthermore, 80% of FLEX eyes and 95% of SMILE eyes had an uncorrected distance visual acuity of 20/25 or better (p = 0.34). Total HOAs, spherical aberration, coma and trefoil increased postoperatively in both groups. However, there was no statistically significant difference between the groups preoperatively and postoperatively. Conclusion: FLEX and SMILE result in comparable refractive results. In addition, corneal aberrations induced by different techniques of lenticule extraction seemed similar to each other. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the efficacy of spherical aberration (SA) correction with aspheric contact lenses (aspheric lenses) based on lens power, and compare the results with those of spherical contact lenses (spherical lenses). Methods: Ocular higher-order aberrations were measured with a wavefront sensor, in 11 myopic subjects wearing an aspheric lens (Medalist Fresh fit (PUREVISION 2 HD); Bausch + Lomb) or a spherical lens (ACUVUE Oasys; Johnson & Johnson). Six different lens powers (-7.00 diopters (D), -5.00 D, -3.00 D, -1.00 D, +1.00 D, +3.00 D) were used for all subjects. The amount of SA correction from the contact lens at each power was calculated as the difference between SA with the contact lens on-eye and SA of the eye alone. Results: For the spherical lenses, SA correction was close to 0.00 µm for the +1.00 D lens, became more positive as the labeled lens power increased and became more negative as the labeled lens power decreased. For the aspheric lenses, SA correction was consistent, from -0.15 to -0.05 µm, for all lens powers except for the -1.00 D lens. SA correction for the spherical and aspheric lenses was significantly different at -7.00 D (p = 0.040), -3.00 D (p = 0.015), -1.00 D (p < 0.001), +1.00 D (p = 0.006), and +3.00 D (p < 0.001) powers. Conclusion: An aspheric lens is capable of correcting SA at different lens powers, and has SA correction in the range of -0.15 to -0.05 µm over a 6 mm aperture. [ABSTRACT FROM AUTHOR]

A curved mesh electrode introduced into an electrostatic lens enables spherical aberration correction over a wide acceptance angle. This technique has great advantages in X-ray photoelectron spectroscopy and related techniques, allowing considerable increase in photoelectron intensity and efficient measurement of photoelectron angular distribution. However, the use of meshes severely limits spatial resolution, as the image produced through each mesh hole is blurred by the lens action of the hole. This feature is studied in detail in this paper, in order to determine the best possible resolution that can be attained in electrostatic mesh lenses with wide acceptance angles. A simple way to evaluate the mesh-hole effect is to use the Davisson–Calbick formula, which expresses the focal length of a single-aperture lens. To make this approach more feasible, we take into account the influence of the angle of incidence to a mesh hole. We characterize the image blur due to each mesh hole in two orthogonal directions, considering the discrepancy in focal length in tangential and sagittal planes. After the demonstration of the validity of our approach in a simple example, the mesh-hole effect of a wide-acceptance-angle electrostatic mesh lens is evaluated. [ABSTRACT FROM AUTHOR]

The effect of spherical aberration on scintillations of Gaussian beams in weak, moderate and strong turbulence is studied using numerical simulation method. It is found that the effect of the negative spherical aberration on the on-axis scintillation index is quite different from that of the positive spherical aberration. In weak turbulence, the positive spherical aberration results in a decrease of the on-axis scintillation index on propagation, but the negative spherical aberration results in an increase of the on-axis scintillation index when the propagation distance is not large. In particular, in weak turbulence the negative spherical aberration may cause peaks of the on-axis scintillation index, and the peaks disappear in moderate and strong turbulence, which is explained in physics. The strong turbulence leads to less discrepancy among scintillations of Gaussian beams with and without spherical aberration. [ABSTRACT FROM AUTHOR]

Abstract: We formulate the fourth order correction to a paraxial Gaussian beam propagated along the axis of symmetry of a parabolic index lens. First we examine the evolution of a complex-source-point spherical wave (equivalent paraxially to a Gaussian beam) through the lens in a two-dimensional xz plane. Taking into account the terms of up to fourth order in aperture variables, we find a ray-optical solution to the exit beam that is represented in terms of aberration function. We also analyze the effect of the lens aberration exerted on the degradation in the quality of a Gaussian beam. The fourth order-corrected wave function derived here may be used to evaluate the quality of a Gaussian beam focused with a parabolic index lens. Further it may be applied to the case of an orthogonal system in which the index variations are different in the xz and yz planes. [Copyright &y& Elsevier]