Large Lens Research Articles

Deep line-temporal focusing with high axial resolution and a large field-of-view using intracavity control and incoherent pulse shaping.

Line-temporal focusing has been recognized as an elegant strategy that provides two-photon microscopy with an effective means for fast imaging through parallelization, together with an improved resilience to scattering for deep imaging. However, the axial resolution remains sub-optimal, except when using high NA objectives and a small field-of-view. With the introduction of an intracavity control of the spectral width of the femtosecond laser to adaptively fill the back aperture of the objective lens, line-temporal focusing two-photon microscopy is demonstrated to reach near-diffraction-limited axial resolution with a large back-aperture objective lens, and improved immunity to sample scattering. In addition, a new incoherent flattop beam shaping method is proposed which provides a uniform contrast with little degradation of the axial resolution along the focus line, even deep in the sample. This is demonstrated in large volumetric imaging of mouse lung samples.

An optical fiber daylighting system with large Fresnel lens

Because of flexible installation and natural spectrum, the concentrated sunlight transmission systems via PMMA (Polymethyl methacrylate) fibers for indoor illumination are concerned widely in areas of building energy saving. Due to the long-term indoor work, the daily working population in cities lacks of natural light and is susceptible to various diseases. Therefore, from the health point of view, it is necessary to develop deep indoor daylighting. In this work, a sunlight concentration and transmission system was developed and tested, which uses a Fresnel lens with a diameter of 1m to achieve large flux collection. A reflection design of light path was adopted to resolve the problem of long focal length of the Fresnel lens. A hot mirror and a homogenizer were used to protect the optic fiber bundle from burned by high temperature. The results showed that the daylighting efficiency is about 11%-13%. The operability of the equipment was verified through experiments, proving that the equipment can be combined with buildings for daylighting. It is hoped that this research will be of some reference value to the design of optical fiber daylighting systems in buildings.

Contribution and acclimatization of the swarming tropical copepod Dioithona oculata (Farran, 1913) in a Mediterranean coastal ecosystem

In this study, tropical oithonid copepod Dioithona oculata was recorded for the first time in the Mediterranean Sea. This species is distinguished easily by its large ocular lenses and by the number of setae on the endopod of the maxillule. The study was conducted seasonally in the coastal area of Iskenderun Bay between April 2013 and December 2016. D. oculata was first observed in October 2013 in the study area (Station 4; 3.1 ind. m − 3 " role="presentation"> − 3 − 3 ^{-3} )); after this period, this species became an important contributor to zooplankton assemblages in October with the highest level seen in 2016 (Station 4, 834.5 ind. m − 3 " role="presentation"> − 3 − 3 ^{-3} ). The proportion of this species in the copepod community varied from 0.14% (2014) to 29.4% (2016), and the highest proportions, observed in October 2016, were at Stations 3 and 4 (51.1% and 65.3%, respectively). Females dominated the D. oculata population and the ratio of female to male was 5.6 ± 7 on average. Copepodit stages were also observed in the population. Altogether, these data indicate that the D. oculata population increased year after year. In addition, the presence of copepodits in the population suggests that this species was established and successfully acclimatized to the conditions, becoming an important component of the zooplankton community in the Iskenderun Bay ecosystem.

Confocal lens focused piezoelectric lithotripter

Usually, piezoelectric lithotripters consist of a high quantity of small flat piezoelectric discs tied to a spherical structure, where the focus is the geometric center of the sphere. The small diameter of the ceramics compared to the distance to the focus of the lithotripter means that only a fraction of the surface pressure will arrive to the focus, and also results in a very small focal diameter. This work focus on the evaluation of a new type of piezoelectric lithotripter with similar dimensions of a commercial lithotripter and composed of either 3 or 4 large lens focused piezoelectric transducers with focal pressure up to 25 MPa each, set either in a confocal C-shape or confocal ring-shape. Each transducer is made with a 92 mm diameter flat piezoelectric ceramic disc of 220, 300, or 400 kHz thickness frequency and the acoustic lens shape was calculated using finite element optimization in order to maximize its focusing capability. Comparison of artificial stone comminution efficiency depending on the frequency, pressure, and the setup of the piezoelectric transducers were made and compared to commercially available lithotripters. [Work supported by an industrial grant from EDAP-TMS.]

‘Upper-limit lensing’: constraining galaxy stellar masses with singly imaged background sources

Strong gravitational lensing can provide accurate measurements of the stellar mass-to-light ratio $\Upsilon$ in low-redshift ($z$ $\lesssim$ 0.05) early-type galaxies, and hence probe for possible variations in the stellar initial mass function (IMF). However, true multiple imaging lens systems are rare, hindering the construction of large nearby lens samples. Here, we present a method to derive upper limits on $\Upsilon$ in galaxies with single close-projected background sources, where no counter-image is detected, down to some relative flux limit. We present a proof-of-principle application to three galaxies with integral field observations from different instruments. In our first case study, only a weak constraint on $\Upsilon$ is obtained. In the second, the absence of a detectable counter-image excludes stellar masses higher than expected for a Salpeter IMF. In the third system, the current observations do not yield a useful limit, but our analysis indicates that deeper observations should reveal a counter-image if the stellar mass is any larger than expected for a Milky Way IMF. We discuss how our method can help enlarge the current samples of low-$z$ galaxies with lensing constraints, both by adding upper limits on $\Upsilon$ and by guiding follow-up of promising single-image systems in search of fainter counter-images.

Multiple timescale constraints for high-flux magma chamber assembly prior to the Late Bronze Age eruption of Santorini (Greece)

The rhyodacitic magma discharged during the 30–80 km3 DRE (dense rock equivalent) Late Bronze Age (LBA; also called ‘Minoan’) eruption of Santorini caldera is known from previous studies to have had a complex history of polybaric ascent and storage prior to eruption. We refine the timescales of these processes by modelling Mg–Fe diffusion profiles in orthopyroxene and clinopyroxene crystals. The data are integrated with previously published information on the LBA eruption (phase equilibria studies, melt inclusion volatile barometry, Mg-in-plagioclase diffusion chronometry), as well as new plagioclase crystal size distributions and the established pre-LBA history of the volcano, to reconstruct the events that led up to the assembly and discharge of the LBA magma chamber. Orthopyroxene, clinopyroxene and plagioclase crystals in the rhyodacite have compositionally distinct rims, overgrowing relict, probably source-derived, more magnesian (or calcic) cores, and record one or more crystallization (plag ≫ opx > cpx) events during the few centuries to years prior to eruption. The crystallization event(s) can be explained by the rapid transfer of rhyodacitic melt from a dioritic/gabbroic region of the subcaldera pluton (mostly in the 8–12 km depth range), followed by injection, cooling and mixing in a large melt lens at 4–6 km depth (the pre-eruptive magma chamber). Since crystals from all eruptive phases yield similar timescales, the melt transfer event(s), the last of which took place less than 2 years before the eruption, must have involved most of the magma that subsequently erupted. The data are consistent with a model in which prolonged generation, storage and segregation of silicic melts were followed by gravitational instability in the subcaldera pluton, causing the rapid interconnection and amalgamation of melt-rich domains. The melts then drained to the top of the pluton, at fluxes of up to 0.1–1 km3 year− 1, where steep vertical gradients of density and rheology probably caused them to inject laterally, forming a short-lived holding chamber prior to eruption. This interpretation is consistent with growing evidence that some large silicic magma chambers are transient features on geological timescales. A similar process preceded at least one earlier caldera-forming eruption on Santorini, suggesting that it may be a general feature of this rift-hosted magmatic system.

Fizeau interferometer with binary phase Fresnel-zone plate reference for precision measurement of large convex lens

A method of obtaining precision transmission wavefront of large convex lens interferometrically using binary Fresnel zone plate (FZP) was presented. We present the results from a set of experiments that demonstrate the accuracy, flexibility, and the simplicity of performing the FZP test. A direct comparison of the FZP measurement with results from a Fizeau interferometry method shows excellent agreement. Finally, measurement uncertainty of lens due to alignment error and FZP fabrication processes is analyzed. This resulting analysis shows less than λ/10 accuracy for measuring the transmission wavefront of a sphere lens with 31.25 m focal length and Φ410 mm clear aperture.

Nd:YAG laser Thomson scattering diagnostics for a laboratory magnetosphere

A new Nd:YAG laser Thomson scattering (TS) system has been developed to explore the mechanism of high-beta plasma formation in the RT-1 device. The TS system is designed to measure electron temperatures (Te) from 10 eV to 50 keV and electron densities (ne) of more than 1.0 × 1017 m-3. To measure at the low-density limit, the receiving optics views the long scattering length (60 mm) using a bright optical system with both a large collection window (260-mm diameter) and large collection lenses (300-mm diameter, a solid angle of ∼68 × 10-3 str). The scattered light of the 1.2-J Nd:YAG laser (repetition frequency: 10 Hz) is detected with a scattering angle of 90° and is transferred via a set of lenses and an optical fiber bundle to a polychromator. After Raman scattering measurement for the optical alignment and an absolute calibration, we successfully measured Te = 72.2 eV and ne = 0.43 × 1016 m-3 for the coil-supported case and Te = 79.2 eV and ne = 1.28 × 1016 m-3 for the coil-levitated case near the inner edge in the magnetospheric plasmas.

Optical imaging featuring both long working distance and high spatial resolution by correcting the aberration of a large aperture lens

High-resolution optical imaging within thick objects has been a challenging task due to the short working distance of conventional high numerical aperture (NA) objective lenses. Lenses with a large physical diameter and thus a large aperture, such as microscope condenser lenses, can feature both a large NA and a long working distance. However, such lenses suffer from strong aberrations. To overcome this problem, we present a method to correct the aberrations of a transmission-mode imaging system that is composed of two condensers. The proposed method separately identifies and corrects aberrations of illumination and collection lenses of up to 1.2 NA by iteratively optimizing the total intensity of the synthetic aperture images in the forward and phase-conjugation processes. At a source wavelength of 785 nm, we demonstrated a spatial resolution of 372 nm at extremely long working distances of up to 1.6 mm, an order of magnitude improvement in comparison to conventional objective lenses. Our method of converting microscope condensers to high-quality objectives may facilitate increases in the imaging depths of super-resolution and expansion microscopes.

Impact on gas-permeable contact lens parameters after storage in a non-neutralized hydrogen peroxide case during 1 to 30 days

Purpose: This study was conducted to evaluate the impact of storing large gas permeable lenses in a regular soft contact lens case, filled with non-neutralized hydrogen peroxide, during 1 to 30 days.

Adverse events and retention of children and teens in a large daily disposable contact lens registry

Purpose: To measure the annual adverse event rate (AEs) and determine factors that affected retention of children and teens while wearing one of two daily disposable contact lenses (DDCLs; etafilcon A or narafilcon B). Also, to describe stability of overall opinion of lenses, and average and comfortable wearing times, during that year.

Multi-slice ptychography with large numerical aperture multilayer Laue lenses

The highly convergent x-ray beam focused by multilayer Laue lenses with large numerical apertures is used as a three-dimensional (3D) probe to image layered structures with an axial separation larger than the depth of focus. Instead of collecting weakly scattered high-spatial-frequency signals, the depth-resolving power is provided purely by the intense central cone diverged from the focused beam. Using the multi-slice ptychography method combined with the on-the-fly scan scheme, two layers of nanoparticles separated by 10 μm are successfully reconstructed with 8.1 nm lateral resolution and with a dwell time as low as 0.05 s per scan point. This approach obtains high-resolution images with extended depth of field, which paves the way for multi-slice ptychography as a high throughput technique for high-resolution 3D imaging of thick samples.

Clinical comparison of optimum and large diameter soft contact lenses.

To compare the clinical performance of large diameter lenses with optimally fit lenses in the same material and monocurve back surface design. In a four-visit, randomised, bilateral, crossover, study, 25 myopic subjects wore optimum diameter lenses (control) and large diameter lenses (test) in random succession for 1 week each. Both study lenses were made of methafilcon A and of an identical design. Trial fittings with Frequency 55 (Coopervision) lenses modified with a design algorithm were used to determine the appropriate custom-made study lenses. The least squares mean scores (±SE) for overall comfort and end-of-day comfort (0-10 scale) were 7.57 ± 0.33 vs. 7.42 ± 0.33 (P = 0.59) and 7.00 ± 0.31 vs. 7.27 ± 0.32 (P > 0.05) for the optimum and large diameter lenses, respectively. There were no significant differences in mean (±SE) gradings for limbal hyperaemia (1.23 ± 0.11 vs. 1.19 ± 0.11, 0-4 scale, P = 0.60) and corneal staining (1.79 ± 0.25 vs. 2.04 ± 0.25, P = 0.39). Conjunctival staining was greater for the optimum lens: 1.80 ± 0.28 vs. 0.93 ± 0.28 (0-4 scale, P = 0.001). With regard to lens fit, the large diameter lenses showed significantly less post-blink movement (0.22 ± 0.01 vs. 0.16 ± 0.01 mm, P = 0.004), and greater total decentration (0.15 ± 0.02 vs. 0.21 ± 0.02 mm, P = 0.010). However, there was no significant difference in the key fit variable of tightness on push-up (46 ± 0.69% vs. 48 ± 0.69%, 0-100 scale, P = 0.12). The findings suggest that larger than optimal soft lenses may be worn without detriment to either comfort or ocular physiology, provided an optimal fit is otherwise maintained.

Scleral Lens Hygiene and Care

Scleral lenses (ScCLs) are developed using the same material as rigid gas permeable corneal lenses yet the care of scleral lenses differs from corneal lenses. These large diameter rigid gas permeable lenses necessitate hygiene, care and compliance protocol that is more complex compared with corneal lenses. Cleaning, disinfection, storing, rinsing and applying ScCL will be discussed. Practitioners will gain confidence in ScCL care which will provide patients with a better understanding of the steps involved in ScCL disinfection leading to increased patient compliance and increased success rates. In turn, patient education will lower the risk for infection and other complications associated with ScCL.

Towards High Productivity in Precision Grinding

Over the last century, substantial advances have been made, based on improved understanding of the requirements of grinding processes, machines, control systems, materials, abrasives, wheel preparation, coolants, lubricants, and coolant delivery. This paper reviews a selection of areas in which the application of scientific principles and engineering ingenuity has led to the development of new grinding processes, abrasives, tools, machines, and systems. Topics feature a selection of areas where relationships between scientific principles and new techniques are yielding improved productivity and better quality. These examples point towards further advances that can fruitfully be pursued. Applications in modern grinding technology range from high-precision kinematics for grinding very large lenses and reflectors through to medium size grinding machine processes and further down to grinding very small components used in micro electro-mechanical systems (MEMS) devices. The importance of material issues is emphasized for the range of conventional engineering steels, through to aerospace materials, ceramics, and composites. It is suggested that future advances in productivity will include the wider application of artificial intelligence and robotics to improve precision, process efficiency, and features required to integrate grinding processes into wider manufacturing systems.

Scalable, large area compound array refractive lens for hard X-rays

We demonstrate the fabrication of a 2D Compound Array Refractive Lens (CARL) for multi-contrast X-ray imaging. The CARL consists of six stacked polyimide foils with each displaying a 2D array of lenses with a 65 μm pitch aiming for a sensitivity on sub-micrometer structures with a (few-)micrometer resolution in sensing through phase and scattering contrast at multiple keV. The parabolic lenses are formed by indents in the foils by a paraboloid needle. The ability for fast single-exposure multi-contrast imaging is demonstrated by filming the kinetics of pulsed laser ablation in liquid. The three contrast channels, absorption, differential phase, and scattering, are imaged with a time resolution of 25 μs. By changing the sample-detector distance, it is possible to distinguish between nanoparticles and microbubbles.

A Metalens with a Near-Unity Numerical Aperture

The numerical aperture (NA) of a lens determines its ability to focus light and its resolving capability. Having a large NA is a very desirable quality for applications requiring small light-matter interaction volumes or large angular collections. Traditionally, a large NA lens based on light refraction requires precision bulk optics that ends up being expensive and is thus also a specialty item. In contrast, metasurfaces allow the lens designer to circumvent those issues producing high-NA lenses in an ultraflat fashion. However, so far, these have been limited to numerical apertures on the same order of magnitude as traditional optical components, with experimentally reported NA values of <0.9. Here we demonstrate, both numerically and experimentally, a new approach that results in a diffraction-limited flat lens with a near-unity numerical aperture (NA > 0.99) and subwavelength thickness (∼λ/3), operating with unpolarized light at 715 nm. To demonstrate its imaging capability, the designed lens is applied in a confocal configuration to map color centers in subdiffractive diamond nanocrystals. This work, based on diffractive elements that can efficiently bend light at angles as large as 82°, represents a step beyond traditional optical elements and existing flat optics, circumventing the efficiency drop associated with the standard, phase mapping approach.

Clinical findings and normative ocular data for free-living Anna's (Calypte anna) and Black-chinned (Archilochus alexandri) Hummingbirds.

To estimate the prevalence of ocular disease and obtain normative ocular data for free-living hummingbirds. Two hundred and sixty-three free-living, adult Hummingbirds from coastal and inland central California were studied, including Anna's (Calypte anna, n = 186) and Black-chinned (Archilochus alexandri; n = 77) hummingbirds. Slit lamp biomicroscopy and indirect ophthalmoscopy were performed on all individuals. Rebound tonometry, measurement of horizontal palpebral fissure length, and streak retinoscopy were performed on select individuals. Five conscious Anna's Hummingbirds underwent ocular imaging including fundus photography, digital slit lamp photography, and anterior segment and retinal optical coherence tomography. The prevalence of ocular disease in this population was 2.28%. Ocular imaging revealed a thin cornea, shallow anterior chamber, large lens, and a single central, deep convexiclivate fovea. Mean ± SD intraocular pressure was 11.21 ± 2.23 mm Hg. Mean ± SD eyelid length was 2.59 ± 0.19 mm. All eyes were emmetropic or mildly hyperopic with a mean (range) ± SD refractive error of +0.32 (-0.25 to +1) ± 0.33 diopters. Consistent with previous reports, these data suggest that hummingbirds have visual characteristics found in predatory and prey species, as well as a low prevalence of spontaneous ocular disease. This work provides a set of reference values and clinical findings that can be used in the future research on hummingbird vision and ocular disease. It also provides representative diagnostic images of normal birds and demonstrates that advanced ocular imaging can be performed on manually restrained hummingbirds without pharmacologic dilation.

Conversion of isotropic fluorescence into a long-range non-diverging beam

Fluorescent samples typically emit isotropically in all directions. Large lenses and other optical components are needed to capture a significant fraction of the emission, and complex confocal microscopes are required for high resolution focal-plane imaging. It is known that Bessel beams have remarkable properties of being able to travel over long distances, over 1000 times the wavelength, without diverging, and hence are called non-diffracting beams. In previous reports the Bessel beams were formed by an incident light source, typically with plane-wave illumination on a circular aperture. It was not known if Bessel beams could form from fluorescent light sources. We demonstrate transformation of the emission from fluorescent polystyrene spheres (FPS) into non-diverging beams which propagate up to 130 mm (13 cm) along the optical axis with a constant diameter. This is accomplished using a planar metal film, with no nanoscale features in the X–Y plane, using surface plasmon-coupled emission. Using samples which contain many FPS in the field-of-view, we demonstrate that an independent Bessel beam can be generated from any location on the metal film. The extremely long non-diffracted propagation distances, and self-healing properties of Bessel beams, offer new opportunities in fluorescence sensing and imaging.

Time multiplexing technique of holographic view and Maxwellian view using a liquid lens in the optical see-through head mounted display

We report a liquid lens based optical see-through head mounted display that can simultaneously display both a maxwellian view and a hologram. Holograms are reconstructed by an angular spectrum layer based synthesis method. A hologram and Maxwellian view are simultaneously displayed by focusing the liquid lens from 0 D to 20 D with 60 Hz. The hologram is reconstructed at a position 1.5 m from the eye, and it is confirmed that the Maxwellian view is clear, even if the focus of the eye changes from 50 cm to 1.7 m. In the proposed system, the liquid lens acts as a low-pass filter. Since the PSNR is about 23 dB in the currently used 10 mm diameter liquid lens, the image quality is not adequate. However, we successfully verify the feasibility of our proposed system. In addition, if a large diameter liquid lens of 30 mm or more is applied, excellent image quality of 30 dB or more can be realized.