نتایج جستجو برای: refractive surfaces

تعداد نتایج: 150251  

Journal: :iranian journal of medical physics 0
maryam abolmasoomi m.sc.in medical physics, tehran university medical sciences, tehran, iran keykhosro keshavarzi assistant professor, medical physics dept., tehran university medical sciences, tehran, iran mehran nikkhou eye specialist, ophthalmology dept., milad hospital ebrahim jafarzadeh poor associate professor, medical physics dept., tehran university medical sciences, tehran, iran

introduction: until now, many models have been presented for optical study of the human eye. in recent years, surgery on the anterior section of the eye (such as cataract and photo-refractive surgery) has increased, so a study on the optics of the eye and evaluation of vision quality has become more important. material and methods: in this article, some of these models are considered. they incl...

2016
Juno Kim Phillip J. Marlow

Specular surfaces and refractive media are difficult to distinguish from each other because they both generate distorted images of the surrounding lighting environment. Whereas convex refractive objects invert the orientation of the horizon so the sky appears beneath the ground plane, convex specular surfaces preserve the orientation of the horizon so the sky appears above the ground. Here, we ...

Journal: :Investigative ophthalmology & visual science 2010
David Borja Fabrice Manns Arthur Ho Noel M Ziebarth Ana Carolina Acosta Esdras Arrieta-Quintera Robert C Augusteyn Jean-Marie Parel

Purpose. To characterize the age dependence of shape, refractive power, and refractive index of isolated lenses from nonhuman primates. Methods. Measurements were performed on ex vivo lenses from cynomolgus monkeys (cyno: n = 120; age, 2.7-14.3 years), rhesus monkeys (n = 61; age, 0.7-13.3 years), and hamadryas baboons (baboon: n = 16; age, 1.7-27.3 years). Lens thickness, diameter, and surface...

Journal: :Journal of the Optical Society of America. A, Optics, image science, and vision 2015
Cristian E Gutiérrez Eric Stachura

We study the problem of constructing an optical surface separating two homogeneous, isotropic media, one of which has a negative refractive index. In doing so, we develop a vector form of Snell's law, which is used to study surfaces possessing a certain uniform refraction property, in both the near- and far-field cases. In the near-field problem, unlike the case when both materials have positiv...

Journal: :Investigative ophthalmology & visual science 2015
Judith Birkenfeld Alberto de Castro Susana Marcos

PURPOSE We estimated the contribution of the gradient refractive index (GRIN) and lens surfaces to lens astigmatism and lens astigmatic angle as a function of age in human donor lenses. METHODS Human lenses were imaged, ex vivo, with 3D-spectral optical coherence tomography (OCT) and their back focal length was measured using laser ray tracing. The contribution of lens surfaces and GRIN to le...

Journal: :Archives of ophthalmology 2007
Terri L Young Ravikanth Metlapally Amanda E Shay

Refractive errors (myopia, hyperopia, and astigmatism) are complex heterogeneous disorders of the human eye and are ideal for genetic investigation. Moderate to severe refractive errors can predispose individuals to poor visual development, various types of glaucoma, misshapen corneal surfaces, premature cataracts, and loss of retinal integrity, which can lead to detachment. Knowledge of geneti...

2012
Matthias Häfner René Reichle Christof Pruss Wolfgang Osten

Hybrid optical elements that combine refractive and diffractive functionality are versatile components for all kinds of applications in imaging or metrology. In the past those elements were composed of a flat diffractive and a curved refractive surface. Fusing both functions in a single surface will enhance the capabilities of these optical components further. The fabrication of such precision ...

Journal: :Optics express 2006
Carlos Dorronsoro Daniel Cano Jesús Merayo-Lloves Susana Marcos

Flat and spherical PMMA surfaces were ablated with a standard refractive surgery laser system. The ratio of profiles on flat to spherical PMMA surfaces was used to estimate experimentally the radial change in ablation efficiency for PMMA and cornea. Changes in ablation efficiency accounted for most of the asphericity increase found clinically, using the same laser system. This protocol is usefu...

2014
S. A. R. Horsley I. R. Hooper R. C. Mitchell–Thomas O. Quevedo–Teruel

The advent of Transformation Optics established the link between geometry and material properties, and has resulted in a degree of control over electromagnetic fields that was previously impossible. For waves confined to a surface it is known that there is a simpler, but related, geometrical equivalence between the surface shape and the refractive index, and here we demonstrate that conventiona...

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