Search results for "Spherical aberration"
showing 10 items of 48 documents
Axial behaviour of Cantor ring diffractals
2003
Cantor ring diffractals describe rotationally symmetric pupils constructed from a one-dimensional polyadic Cantor set. The influence on the axial irradiance of several fractal descriptors of such pupils, including fractal dimension, number of gaps and lacunarity, are investigated. It is shown that, contrary to their transversal response, the axial behaviour of these pupils does not resemble the fractal structure of the aperture. The sensitivity of such pupils to the spherical aberration is also analysed.
Influencia del modelo de ojo teórico en la evaluación numérica de lentes intraoculares fractales
2020
In this work we present the numerical evaluation of a new design of fractal intraocular lens studied through a ray-tracing program. To determine the monochromatic and polychromatic performance of these lenses in different theoretical model eyes the Modulation Transfer Function (MTF) and the area above the MTF (AMTF) have been used. These merit functions show the same behavior for different values of asphericity (Q), independently from the theoretical model eye, even though there are differences due to the Spherical Aberration (SA) considered in each model.
Synthesis of filters for specified axial irradiance by use of phase–space tomography
2001
A procedure for designing pupil filters for applications where specified axial responses are required is developed. The method is based on the mathematical relationship between the axial impulse response of a system and the Wigner distribution function (WDF) associated to its pupil function. The desired axial irradiance, which can also have a predefined behavior depending on spherical aberration, is used to obtain this WDF by tomographic reconstruction. The synthetic pupil is retrieved from this distribution.
PEEM with high time resolution—imaging of transient processes and novel concepts of chromatic and spherical aberration correction
2006
The potential of time-resolved photoemission electron microscopy (PEEM) for imaging ultrafast processes and for aberration correction in full-field imaging is discussed. In particular, we focus on stroboscopic imaging of precessional magnetic excitations via XMCD-PEEM exploiting the time structure of synchrotron radiation (magnetic field pulse pump–X-ray probe). In a special bunch-compression mode at BESSY, a time resolution of about 15 ps has been obtained. Further, we discuss an all-optical pump–probe technique using femtosecond laser excitation. A highly promising alternative to stroboscopic imaging is an approach using time-resolved image detection. As a second application of time-resol…
Simple demonstration of the impact of spherical aberration on optical imaging
2008
We present an experiment, well adapted for students of introductory optics courses, for the visualization of the impact of spherical aberration in the point spread function of imaging systems. The demonstrations are based on the analogy between the point-spread function of spherically aberrated systems, and the defocused patterns of 1D slit-like screens.
Shaded-Mask Filtering for Extended Depth-of-Field Microscopy
2013
This paper proposes a new spatial filtering approach for increasing the depth-of-field (DOF) of imaging systems, which is very useful for obtaining sharp images for a wide range of axial positions of the object. Many different techniques have been reported to increase the depth of field. However the main advantage in our method is its simplicity, since we propose the use of purely absorbing beam-shaping elements, which allows a high focal depth with a minimum modification of the optical architecture. In the filter design, we have used the analogy between the axial behavior of a system with spherical aberration and the transverse impulse response of a 1D defocused system. This allowed us the…
New Analytical Tools for Evaluation of Spherical Aberration in Optical Microscopy
2010
The required tightly focused spots in three-dimensional (3D) scanning optical techniques are usually achieved by high-NA immersion lenses. The refractive index mismatch between the sample and the immersion medium introduces an important amount of spherical aberration when imaging deep inside the specimen, spreading out the focusing response. Since this aberration depends on the focalization depth, it is not possible to simultaneously achieve a global compensation for the whole scanned sample. In this way, the design of pupil elements that increase the tolerance to this aberration is of great interest. We present a new formalism for the evaluation and the design of filters that decrease the …
Temporal multiplexing with adaptive optics for simultaneous vision.
2016
We present and test a methodology for generating simultaneous vision with a deformable mirror that changed shape at 50 Hz between two vergences: 0 D (far vision) and −2.5 D (near vision). Different bifocal designs, including toric and combinations of spherical aberration, were simulated and assessed objectively. We found that typical corneal aberrations of a 60-year-old subject changes the shape of objective through-focus curves of a perfect bifocal lens. This methodology can be used to investigate subjective visual performance for different multifocal contact or intraocular lens designs.
Analysis of the possible benefits of aspheric intraocular lenses: review of the literature.
2008
We reviewed recently published studies that analyzed the visual and optical quality in eyes with different spherical and aspheric intraocular lenses (IOLs). Recent studies focused on visual quality metrics, such as visual acuity and contrast sensitivity, under photopic and mesopic lighting conditions and optical metrics, such as wavefront aberrations, especially spherical aberration. The results in this review were used in an attempt to understand whether there is a visual and/or optical benefit of implanting aspheric IOLs over implanting spherical IOLs.
In vitro optical performance of a new aberration-free intraocular lens
2014
To assess the optical performance of the new EnVista intraocular lens (IOL). Four aspheric IOLs were evaluated; the new EnVista is one amoung them. This IOL, similarly to the Z-Flex HB and the Bi-Flex 1.8 667AB ones, has a neutral aspheric design, whereas the fourth IOL under test (AcrySof IQ IOL SN60WF) presents a negative spherical aberration (SA). The IOL’s aberration patterns were measured in vitro, by setting them up on an optical bench. From these aberration-pattern data, the modulation transfer function (MTF), the average modulation values, and the points spread function (PSF) were calculated. Furthermore, in order to assess the potential optical quality that these IOLs would yield o…