Spherical Lens Research Articles

Effects of the interlayer thickness on the optical characteristics of an ultrasound multilayered liquid crystal lens

Ultrasound multilayered variable-focus liquid crystal (LC) lenses have better optical performance compared to conventional ultrasound LC lenses. This paper investigates the effect of the distance between two LC layers on the optical characteristics of the lens. The LC molecular orientation in the lens was altered by the acoustic radiation force generated by the lens’ resonance flexural vibration mode, causing a change in the focal length. The focal length change was increased dramatically, and the electrical consumption was reduced in lenses with thinner interlayers.

Ocular lens morphology is influenced by ecology and metamorphosis in frogs and toads.

The shape and relative size of an ocular lens affect the focal length of the eye, with consequences for visual acuity and sensitivity. Lenses are typically spherical in aquatic animals with camera-type eyes and axially flattened in terrestrial species to facilitate vision in optical media with different refractive indices. Frogs and toads (Amphibia: Anura) are ecologically diverse, with many species shifting from aquatic to terrestrial ecologies during metamorphosis. We quantified lens shape and relative size using 179 micro X-ray computed tomography scans of 126 biphasic anuran species and tested for correlations with life stage, environmental transitions, adult habits and adult activity patterns. Across broad phylogenetic diversity, tadpole lenses are more spherical than those of adults. Biphasic species with aquatic larvae and terrestrial adults typically undergo ontogenetic changes in lens shape, whereas species that remain aquatic as adults tend to retain more spherical lenses after metamorphosis. Further, adult lens shape is influenced by adult habit; notably, fossorial adults tend to retain spherical lenses following metamorphosis. Finally, lens size relative to eye size is smaller in aquatic and semiaquatic species than other adult ecologies. Our study demonstrates how ecology shapes visual systems, and the power of non-invasive imaging of museum specimens for studying sensory evolution.

Vault differences in eyes implanted with spherical and toric implantable collamer lenses: an inter-eye analysis

PurposeTo determine the influence of implantable collamer lenses (ICL) geometry, i.e. spherical and toric on the vault, and report the refractive and visual outcomes of patients bilaterally implanted with the two ICL geometries.MethodsThis retrospective case series analysed 41 patients implanted with a spherical ICL (sICL) in one eye and an equal sized toric ICL (tICL) in the fellow eye. The anatomical and ICL-related parameters were assessed using anterior-segment optical coherence tomography (AS-OCT Visante, Zeiss Meditec AG) and optical tomography (Pentacam, OCULUS). The influence of the anatomical and ICL-related parameters on the vault was determined using generalised estimating equations (GEE) to incorporate inter-eye correlations.ResultsPostoperative spherical equivalent was within ± 0.50D in 66% and 83% of the eyes, respectively implanted with sICL and tICL. The efficacy index in the sICL group was 1.06 and 1.14 in the tICL group. The mean inter-eye vault difference was -1.46 µm, anatomical and ICL-related parameters showed similar associations with the vault for sICL and tICL. The GEE identified the ICL size minus the anterior chamber width, the ICL spherical power and ICL central thickness as significant factors influencing the vault.ConclusionsSpherical and toric ICL showed good efficacy for the correction of myopia and astigmatism. Patients implanted bilaterally with sICL and tICL tend to present similar vaults. The vault produced by both types of ICL was mainly regulated by the oversizing of the ICL. This suggests that the ICL geometry (spherical vs toric) is a factor with limited influence on the vault, thus the sizing method of a sICL and tICL should be similar.

Reduce spherical aberration of doublet of combined quadrupole lenses (rectangular model)

The optimization calculations are made to find the optimum properties of doublet of combined quadrupole lens consist of electrostatic and magnetic lenses to produce reduce spherical aberration lens. The rectangular model is used and finds the properties of lens as the magnification and aberration coefficient. To find the optimum value of spherical aberration coefficient, the effect of both the excitation parameter of the lens, distance between of lenses and the effective wave length of the lens as active parameter to get the optimization.

A Depth Sensor Based on Transient Property of Liquid Crystal Lens

The property of maintaining the lens state of the liquid crystal (LC) lens during the switching between positive and negative lens states is made use of in the fast acquirement of multi-focus images without magnification change. A depth from focus (DFF) pipeline that can generate a low-error depth map and an all-in-focus image is proposed. The depth of the scene is then obtained via DFF pipeline from the captured images. The depth sensor proposed in this paper has the advantages of simple structure, low cost, and long service life.

Cost-Effective Design of a Miniaturized Zoom Lens for a Capsule Endoscope.

This paper presents a miniaturized design of a 2× zoom lens for application to a one-megapixel image sensor in a capsule endoscope. The zoom lens is composed of four lenses, including three plastic aspheric lenses and one glass spherical lens, and adopts a three-lens group design. This capsule endoscope is mainly for observation of the small intestine, which has a radius of about 12.5 mm. The height of the object is thus set to 12.5 mm. The object surface is designed to be curved surface with a radius of curvature of 15 mm. The focal length of the zoom lens ranges from 1.064 mm to 2.039 mm, and the full angle of view ranges from 60° to 143°, the f-number is F/2.8-F/3.5, the zoom lens is 11.6 mm in length, and the maximum effective diameter of the zoom lens is 6 mm. The zoom lens design is divided into six segments, corresponding to the different magnifications from Zoom 1 to Zoom 6. The magnification ratios are -0.0845, -0.0984, -0.1150, -0.1317, -0.1482, and -0.1690, respectively. Comparing the positions from Zoom 1 to Zoom 6, the maximum optical distortion is -14.89% for the Zoom 1 and 1.45% for the Zoom 6. The maximum vertical video distortion is 8.19% for Zoom 1 and 1.00% for Zoom 6. At a 1.0 field of view, the minimum relative illuminance is 71.8% at a magnification of M = -0.1317. Finally, we perform the tolerance analysis and lens resolution analysis at different zooming positions. Our design can obtain high-quality images for capsule endoscope.

Experimental Research and Optimization of Ti-6Al-4V Alloy Microgroove Machining Based on Waterjet-Guided High-Power Laser.

In order to improve the tribological properties of Ti-6Al-4V alloy and further broaden the application scope of titanium alloy materials in the industrial field, a preparation method of a waterjet-guided high-power laser processing surface microgroove was studied. In this paper, a multifocus coupling lens was innovatively designed to replace the spherical lens in the traditional waterjet-guided laser coupling device, which avoids the gas explosion phenomenon in the coupling of the high-power laser and waterjet, and realizes the high-quality coupling of the high-power laser and water beam fiber. Then, with the microgroove morphology as the response target, the single-factor test and response surface test of the water-guided laser processing microgroove were carried out. Based on the experimental results, an approximate mathematical model of the response surface between the process parameters and the microgroove topography target was constructed, and the quantitative relationship between the waterjet-guided laser processing parameters and the target response was studied. At the same time, the optimal combination of process parameters was obtained by multiobjective optimization, so as to effectively improve the microgroove morphology. This technology provides method guidance and a decision-making reference for subsequent waterjet-guided laser processing of titanium alloy surface functional microstructures.

An integrated imaging sensor for aberration-corrected 3D photography

Planar digital image sensors facilitate broad applications in a wide range of areas1–5, and the number of pixels has scaled up rapidly in recent years2,6. However, the practical performance of imaging systems is fundamentally limited by spatially nonuniform optical aberrations originating from imperfect lenses or environmental disturbances7,8. Here we propose an integrated scanning light-field imaging sensor, termed a meta-imaging sensor, to achieve high-speed aberration-corrected three-dimensional photography for universal applications without additional hardware modifications. Instead of directly detecting a two-dimensional intensity projection, the meta-imaging sensor captures extra-fine four-dimensional light-field distributions through a vibrating coded microlens array, enabling flexible and precise synthesis of complex-field-modulated images in post-processing. Using the sensor, we achieve high-performance photography up to a gigapixel with a single spherical lens without a data prior, leading to orders-of-magnitude reductions in system capacity and costs for optical imaging. Even in the presence of dynamic atmosphere turbulence, the meta-imaging sensor enables multisite aberration correction across 1,000 arcseconds on an 80-centimetre ground-based telescope without reducing the acquisition speed, paving the way for high-resolution synoptic sky surveys. Moreover, high-density accurate depth maps can be retrieved simultaneously, facilitating diverse applications from autonomous driving to industrial inspections.

Performance improvement of focused acoustic-vortex tweezers constructed by a hyperboloidal acoustic lens and a circular array

Although the traditional focused acoustic-vortex (FAV) beams can be realized by a spherical acoustic lens, the manipulation performance still suffers from the incomplete focusing at a preassigned point. In the current study, by applying the Fermat’s principle to the phase-coded circular array of planar sectorial sources, a hyperboloidal concave acoustic lens determined by the refractive index and the focal length is designed to construct hyperboloidal-focused acoustic-vortex (H-FAV) tweezers to improve the manipulation capability in a minimized focal region. Compared with the FAV beam, the peak-pressure of the H-FAV tweezer is obviously enhanced in a smaller-sized focal region, and the trapping capability of the tweezer can be greatly improved by the strengthened acoustic gradient force due to the smaller vortex radius. With the established 16-channel system, H-FAV beams of different orders are built using a hyperboloidal lens manufactured by 3-D printing. The experimental acoustic fields of pressure and phase show good agreements with numerical results and attest to the improved performance of H-FAV tweezers. Moreover, benefiting from the flexible and controllable focusing, the H-FAV tweezers exhibits prosperous perspectives in high-precision application fields of acoustic focusing, ultrasonic therapy, acoustic levitation and particle manipulation.

Ray Optics for Gliders.

Control of self-propelled particles is central to the development of many microrobotic technologies, from dynamically reconfigurable materials to advanced lab-on-a-chip systems. However, there are few physical principles by which particle trajectories can be specified and can be used to generate a wide range of behaviors. Within the field of ray optics, a single principle for controlling the trajectory of light─Snell's law─yields an intuitive framework for engineering a broad range of devices, from microscopes to cameras and telescopes. Here we show that the motion of self-propelled particles gliding across a resistance discontinuity is governed by a variant of Snell's law, and develop a corresponding ray optics for gliders. Just as the ratio of refractive indexes sets the path of a light ray, the ratio of resistance coefficients is shown to determine the trajectories of gliders. The magnitude of refraction depends on the glider's shape, in particular its aspect ratio, which serves as an analogue to the wavelength of light. This enables the demixing of a polymorphic, many-shaped, beam of gliders into distinct monomorphic, single-shaped, beams through a friction prism. In turn, beams of monomorphic gliders can be focused by spherical and gradient friction lenses. Alternatively, the critical angle for total internal reflection can be used to create shape-selective glider traps. Overall our work suggests that furthering the analogy between light and microscopic gliders may be used for sorting, concentrating, and analyzing self-propelled particles.

Corneal RGP Contact Lens Fitting Software for Keratoconus Built-In Anterior Segment Optical Coherence Tomography.

To assess the performance of the contact lens fitting software built into anterior segment optical coherence tomography (AS-OCT). This retrospective study enrolled patients with keratoconus prescribed with spherical corneal rigid gas-permeable contact lenses based on a contact lens fitting software. Subjects were classified into four subgroups based on corneal morphology: nipple, oval, globus, and marginal type. Software performance was evaluated according to the correlation between the back optical zone radius (BOZR) calculated by the contact lens fitting program and the BOZR of the lens prescribed, and the number of trial lens replacements required.Results:A total of 340 eyes of 254 patients with a mean age of 40.4 ± 13.6 years were included. The oval type was the most common (61.8%), followed by the nipple type (26.2%). Linear regression analysis revealed a significant correlation between the prescribed and the calculated BOZR in all subgroups (R 2 = 0.92, P < 0.01 for the nipple type; R 2 = 0.76, P < 0.01 for the oval type; R 2 = 0.93, P < 0.01 for the globus type; and R 2 = 0.79, P < 0.01 for the marginal type). Furthermore, the globus type had the highest proportion of cases requiring at least one trial lens replacement (36.3%), followed by the nipple group (27.0%). There were no significant differences among the subgroups ( P = 0.14). In conclusion, our findings reveal that the contact lens fitting software built into AS-OCT may be useful for accurate contact lens prescription for any corneal shape.

Triple-layer spherical electrowetting liquid lens with large-aperture and high zoom ratio

We propose a triple-layer spherical electrowetting liquid lens with large-aperture and high zoom ratio. The chamber of the proposed lens is spherical, which can enlarge the apparent contact angle range. The triple-layer liquid consists of a conductive liquid, an insulating liquid and a conductive liquid in turn, which forms two independent liquid-liquid (L-L) interfaces. We simulated and analyzed the geometric location of the L-L interfaces to ensure that the two liquid-liquid interfaces do not fuse under the requirement of compact design. The two L-L interfaces are symmetrically distributed on the upper and lower hemispheres of the spherical chamber and can be changed the surface shapes at the same time. The experimental results show that the zoom ratio of our proposed lens is 4.12. And the focal length can be changed from −35.2 mm to 51.1 mm under 0–80 V applied voltage, and has two focal segments according to different working electrodes. 8 mm clear aperture and 6 mm total liquid thickness mean that the triple-layer spherical electrowetting liquid lens can be pretty compact and has a great application prospect in imaging systems, such as microscopic imaging system, etc.

A 3‐D ‐printed Luneburg lens antenna with consistent multibeams based on quasi‐pyramid structure

A wide-scanning dual-polarized Luneburg lens antenna based on the quasi-pyramid structure is proposed. To achieve beam consistency, 18 identical quasi-pyramid sections are employed to approximate a spherical lens antenna, and each section is divided into 12 layers. The 6-stepped gradient permittivity index is achieved by the diced ring-type periodic unit cells in accordance with the Effective Medium Theory. Each quasi-pyramid is incorporated with the same connecting structure to form an integrity. And a dielectric rod is penetrated parallelly to the center axis of the lens, thus improving the robustness of the overall structure. The radius of the whole lens is merely 0.88λ0. The spherical Luneberg lens antenna is fabricated and measured, with an impedance bandwidth of 45.5%, a measured peak gain of 15.4/15.1 dBi and a cross-polarization level of higher than 17/17.5 dB. Placing the feed antenna at different locations during the measurement, results attest that those beams possess an excellent consistency. The multibeams are able to achieve an ultra-wide beam coverage of 165°, promising it a serviceable candidate for mobile communication base stations and wireless networking.

P‐12.9: A Switchable Liquid Crystal Microlens Between 1D and 2D Arrays

P‐12.9: A Switchable Liquid Crystal Microlens Between 1D and 2D Arrays

54.3: Invited Paper: Surface Control of LC Alignment for Creation of Liquid Crystal Lenses Arrays

New photosensitive alignment materials, capable to obtain pretilt angle from 90 to 0 degree in single technological process of UV exposure, are developed. The novel technological method for fabrication LC lens and LC lenses arrays has been developed based on new pretilt angle gradient alignment materials. Laboratory samples of voltage tunable LC lens and LC lenses arrays are obtained and characterized. The developed low cost fabrication technology of tunable micro‐lenses arrays based on photosensitive alignment materials has low complexity and is perspective for light field technology applications.

Femtosecond inscription of chirped fiber Bragg gratings and fiber Bragg grating arrays using a single uniform phase-mask

Chirped fiber Bragg gratings (CFBGs) and arrays of fiber Bragg gratings (FBGs) are inscribed with femtosecond pulses and a single uniform phase-mask (PM). The inscription setup includes an 800 nm NIR femtosecond laser, a PM, a defocusing spherical lens and a cylindrical focusing lens. The wavelength tunability is achieved by a defocusing lens, and movement of the PM. A first FBG is inscribed, followed by nine cascading FBGs, where each one is inscribed only after the movement of the PM and a movement of the fiber, thus allowing inscription on a fresh fiber section without overlapping. The transmission and reflection spectra of these ten cascaded FBGs are measured showing a spectral shift of ∼0.9 nm between each one, and a total shift of ∼8 nm. The transmission dip of each FBG is roughly −10 dB. The CFBG is inscribed with the same single uniform PM and with the same setup, but with different movement increments of the PM and fiber. The transmission and reflection spectra of the resulting CFBG are measured with a strength of ∼20 dB and a continuous bandwidth of ∼4.7 nm at FWHM. This yields a chirp rate of ∼1 nm/cm, while the full length of the CFBG is ∼45 mm.

Effect of peripheral refractive errors on driving performance.

The effect of peripheral refractive errors on driving while performing secondary tasks at 40° of eccentricity was studied in thirty-one young drivers. They drove a driving simulator under 7 different induced peripheral refractive errors (baseline (0D), spherical lenses of +/- 2D, +/- 4D and cylindrical lenses of +2D and +4D). Peripheral visual acuity and contrast sensitivity were also evaluated at 40°. Driving performance was significantly impaired by the addition of myopic defocus (4D) and astigmatism (4D). Worse driving significantly correlated with worse contrast sensitivity for the route in general, but also with worse visual acuity when participants interacted with the secondary task. Induced peripheral refractive errors may negatively impact driving when performing secondary tasks.

Fast response electrically controlled liquid crystal lens array for high resolution 2D/3D switchable display.

A fast response electrically controlled liquid crystal (LC) lens array is revealed. In order to realize the fast response, a double LC layer structure is adopted. The fabricated LC lens array has a small pitch of 310µm and LC layer with a thickness of 50μm. Experimental results show that the focal length of the LC lens array can be continuously adjusted by low driving voltage (∼6.5Vrms), and the shortest focal length is 0.5mm. The switching between 2D display and 3D display is realized by controlling the voltage off and on state of the LC lens array. Experimental result shows that the 2D/3D switchable display has a fast response time of 16ms. The short pitch LC lens array is expected to be used in high-resolution 2D/3D switchable display.

Laguerre-Gaussian Beams with an Increased Dark Area and Autofocusing

We introduce and investigate a novel Laguerre-Gaussian (LG) beam, different from the conventional modal LG beams, which conserve the transverse intensity structure (up to scale) on propagation. The proposed beam does not conserve its structure on free space propagation but possesses some interesting properties. This beam is Fourier-invariant, and it has an increased dark area both in the initial (waist) plane and in the far field. Thus, without changing the topological charge of the beam, varying the radial (lower) index of the associated Laguerre polynomial allows increasing or decreasing the effective diameter of the central dark spot in the intensity pattern. In addition, the beam is autofocusing, i.e., the intensity distribution at the Rayleigh distance from the waist has a shape of the light ring (at any value of the radial index) with the minimal diameter and with the maximal on-ring intensity. Such a beam can be adopted for microparticle manipulation. Increasing the dark area in the focus of a high-aperture spherical lens allows the simultaneous trapping of several absorbing microparticles into this dark area.

Theoretical derivation and clinical validation of the resolution limit of human eye to spherical lens change: a self-controlled study

PurposeThe aim of this study was to deduce theoretically and verify the resolution limit of human eye to spherical lens change for more reasonable design of the trial lenses.MethodsA total of 119 normal subjects with different myopia (not more than − 6D) were included. First, the resolution limit of discernible change in spherical power was derived based on the optical model. Then, the subjects were observed to see if they could perceive the changes in spherical power as per the resolution limit and compare the difference in the best-corrected visual acuity obtained with the resolution limit and interval of 0.25D.ResultsAssuming that the cone cell diameter is 3 μm and the pupil diameter of 4 mm, the theoretically resolution limit was 0.05D. When the diopter of spherical power was increased, the ratios of ability to perceive 0.05D spherical lens change were 98.3% and 96.7% in right and left eyes. When the diopter of spherical power was decreased, the ratios of ability to perceive 0.05D spherical lens change were 78.9% and 83.2% in right and left eyes. The best-corrected visual acuity obtained with the 0.05 D interval trial lens was significantly better than in the 0.25 D interval on both eyes (Right eye − 0.04 ± 0.07 vs − 0.02 ± 0.06, p < 0.001; Left eye − 0.07 ± 0.06 vs − 0.04 ± 0.06, t = 8.825, p < 0.001).ConclusionThe resolution limit of human eye to spherical lens change was about 0.05D and the better corrected visual acuity can be obtained by adjusting the spherical power at an interval of 0.05D.Trial registration number: ChiCTR2100047074.Date of registration: 2021/6/7.