Search results for "Lenses"
showing 10 items of 294 documents
3D printed diffractive terahertz lenses
2016
[EN] A 3D printer was used to realize custom-made diffractive THz lenses. After testing several materials, phase binary lenses with periodic and aperiodic radial profiles were designed and constructed in polyamide material to work at 0.625 THz. The nonconventional focusing properties of such lenses were assessed by computing and measuring their axial point spread function (PSF). Our results demonstrate that inexpensive 3D printed THz diffractive lenses can be reliably used in focusing and imaging THz systems. Diffractive THz lenses with unprecedented features, such as extended depth of focus or bifocalization, have been demonstrated.
Multiplexing THz Vortex Beams With a Single Diffractive 3-D Printed Lens
2019
[EN] We present a novel method for experimentally generating multiplexed THz vortex beams by using a single three-dimensional printed element that combines a set of radially distributed spiral phase plates, and a binary focusing Fresnel lens. With this element, we have experimentally demonstrated that THz multiplexing can be tailored to fit within a small space on an optical bench. Results are presented beside numerical simulations, demonstrating the robust nature of the experimental method.
Oxygen Transmissibility of Piggyback Systems With Conventional Soft and Silicone Hydrogel Contact Lenses
2006
To investigate the apparent oxygen transmissibility of various piggyback systems using conventional and silicone hydrogel soft contact lenses of different water content and permeability, rigid poly(methyl methacrylate), and rigid gas-permeable lenses of medium, high, and ultrahigh oxygen permeability. The aim of the study was to establish which material (rigid or hydrogel) is more representative of the resulting oxygen performance of piggyback systems. METHODS: The apparent oxygen transmissibility of 66 piggyback systems was measured with an electrochemical method. Eighteen of these combinations involved the use of silicone hydrogel contact lenses currently available. One hyperpermeable rig…
Recommendations for eye care during the alarm state by the coronavirus disease pandemic COVID-19.
2020
Abstract Objective Minimize exposure to the SARS-CoV-2, reduce the chances of cross-transmission between patients and healthcare personnel, and prevent the development of postoperative complications from the management of patients with eye diseases during the 2019 coronavirus disease pandemic (COVID-19). Methods COVID-19 literature review and consensus establishment between different Spanish ophthalmology societies in order to provide guidelines and recommendations of maximum resources primarily conditioned by the state of alert, confinement and social distancing that occurs in Spain since March 16, 2020. Results The recommendations will promote the adoption of action and protection measure…
Eye fluke infection and lens size reduction in fish: a quantitative analysis.
2008
Parasites have a variety of harmful effects on their hosts, some of which may be overlapping or complementary and thus easily overlooked but which are still important for the overall severity of infection. We investigated the effect of Diplostomum sp. eye fluke infection on the size of the eye lens in a range of wild and farmed fish species and those exposed to controlled parasite infection. We found that asymmetry in intensity of infection between the right and left lens of an individual fish affected lens size such that the lens with the higher intensity of infection was smaller. Interestingly, however, this was observed only in 3 of the 10 species studied (whitefish, smelt and sea trout)…
Diffractive optics for quasi-direct space-to-time pulse shaping.
2008
The strong chromatic behavior associated with a conventional diffractive lens is fully exploited to propose a novel optical device for pulse shaping in the femtosecond regime. This device consists of two optical elements: a spatially patterned circularly symmetric mask and a kinoform diffractive lens, which are facing each other. The system performs a mapping between the spatial position of the masking function expressed in the squared radial coordinate and the temporal position in the output waveform. This space-to-time conversion occurs at the chromatic focus of the diffractive lens, and makes it possible to tailor the output central wavelength along the axial location of the output point…
Material properties of various intraocular lenses in an experimental study.
2002
<i>Introduction:</i> With the recent introduction of small-incision cataract surgery, requirements for intraocular lens (IOL) flexibility, strength and hydrophilicity have rapidly evolved. The IOL surface, however, remains a critical factor influencing uveal biocompatibility. <i>Purpose:</i> To objectively quantify factors of material properties of various IOLs using contact angle measurements, differential scanning calorimetry, dynamic-mechanical measurements and scanning electron microscopy. <i>Material and Methods:</i> In our study, 17 currently available IOLs were investigated using contact angle measurements to assess hydrophilicity and biocompatibil…
Twin axial vortices generated by Fibonacci lenses.
2013
Optical vortex beams, generated by Diffractive Optical Elements (DOEs), are capable of creating optical traps and other multifunctional micromanipulators for very specific tasks in the microscopic scale. Using the Fibonacci sequence, we have discovered a new family of DOEs that inherently behave as bifocal vortex lenses, and where the ratio of the two focal distances approaches the golden mean. The disctintive optical properties of these Fibonacci vortex lenses are experimentally demonstrated. We believe that the versatility and potential scalability of these lenses may allow for new applications in micro and nanophotonics.
Individuālu mīksto kontaktlēcu pielietojums acs aberāciju kompensācijai
2017
Darbs uzrakstīts angļu valodā uz 63 lapām. Tas satur 46 attēlus, 1 tabulu un 53 atsauces uz literatūras avotiem. Mērķis. Novērtēt agstāko kārtu aberāciju (HOA) ietekmi uz redzes funkcijām un acs optisko kvalitāti FOOT kontaktlēcu (KL) nēsātājiem. Metodes. Tika izmērīts redzes asums gadījumos (RA), kad acī ievietotas FOOT KL un parastās gāzu caurlaidīgās KL. Tika izmērītas visas aberācijas (TA) un HOA gadījumā, kad ievietotas abu veidu lēcas. Rezultāti. FOOT KL gadījumā RA bija tāds pats kā parasto KL gadījumā, vai augstāks (p<.01). FOOT KL gadījumā TA un HOA līmenis bija tāds pats kā parasto KL gadījumā, vai mazāks (p-value < .01). Secinājumi. FOOT KL sniedz augstāku RA nekā parastās KL un …
Multiple-plane image formation by Walsh zone plates.
2018
[EN] A radial Walsh filter is a phase binary diffractive optical element characterized by a set of concentric rings that take the phase values 0 or ¿, corresponding to the values + 1 or ¿1 of a given radial Walsh function. Therefore, a Walsh filter can be re-interpreted as an aperiodic multifocal zone plate, capable to produce images of multiple planes simultaneously in a single output plane of an image forming system. In this paper, we experimentally demonstrate for the first time the focusing capabilities of these structures. Additionally, we report the first achievement of images of multiple-plane objects in a single image plane with these aperiodic diffractive lenses.