Sergio Barbero

Spanish National Research Council | CSIC · Institute of Optics "Daza de Valdés"

PurposeTo propose geodesic curvature as a metric to characterise how an optical surface locally differs from axial symmetry. To derive equations to evaluate geodesic curvatures of arbitrary surfaces expressed in polar coordinates.Methods The concept of geodesic curvature is explained in detail as compared to other curvature-based metrics. Starting...

Blur and non-uniform magnification are two related undesired effects affecting vision when looking through eyeglasses. We propose a geometrical framework to study the relationship between both effects. Magnification and blur are locally characterized by dioptric and magnification matrices, respectively, which we compute here by using a novel two-ra...

https://editorial.csic.es/publicaciones/libros/12415/0/como-funcionan-nuestras-gafas.html

En 1947 se instaló en el Instituto de Óptica Daza de Valdés (IO), del CSIC, el primer microscopio electrónico de España: un modelo EMU-2A de la empresa estadounidense RCA. Aquel instrumento se convirtió en lo que se ha denominado «instrumento frontera», «inventor de disciplinas»; en este caso, la microscopía electrónica. Se analiza las actividades...

Although second-order surface analysis, mainly mean power and cylinder maps, are commonly used to characterize progressive addition surfaces (PAL), recently it has been suggested that third-order variations may also have relevancy in PAL optical and visual performance. This paper proposes a third-order smoothness metric, and its associated Riemanni...

Although second-order surface analysis, mainly mean power and cylinder maps, are commonly used to characterize progressive addition surfaces (PAL), recently it has been suggested that third-order variations may also have relevancy in PAL optical and visual performance. This paper proposes a third-order smoothness metric, and its associated Riemanni...

EL HURÓN Y EL AZOR en los predios del Monte del Pardo, el Bosque Viejo; en estas incursiones se jugaban la vida-sorteando a los bien armados guardas del monte-por la mera aspira-ción a poder mejorar la magra alimentación de los suyos con la carne tierna de algún gazapo o, con suerte, la de algún corcino. Huelga decir que Blasco Ibáñez acom-pañó a u...

El desarrollo científico-tecnológico de instrumentos ópticos en España tuvo una época de florecimiento en la década de los cuarenta y cincuenta del siglo XX. Esto fue debido al impulso de, primero, la Sección de Óptica del Instituto de Física Alonso de Santa Cruz, y, posteriormente, del Instituto de Óptica Daza de Valdés, fundado en 1946; ambas ins...

We survey some mathematical tools involved in the design of multifocal surfaces which are used in presbyopia Sergio Barbero is an optics researcher at Instituto deÓptica from CSIC (Spain). His email address is sergio.barbero@csic.es.

Designing extended-depth-of-focus wavefronts is required in multiple optical applications. Caustic location and structure analysis offer a powerful tool for designing such wavefronts. An intrinsic limitation of designing extended-depth-of-focus wavefronts is that any smooth surface, with a non-constant mean curvature, unavoidably introduces a separ...

Designing extended-depth-of-focus wavefronts is required in multiple optical applications. Caustic location and structure analysis offer a powerful tool to design such wavefronts. An intrinsic limitation of designing extended-depth-of-focus wavefronts is that any smooth surface, with a non-constant mean curvature, unavoidably introduces a separatio...

Designing extended-depth-of-focus wavefronts is required in multiple optical applications. Caustic location and structure analysis offer a powerful tool to design such wavefronts. An intrinsic limitation of designing extended-depth-of-focus wavefronts is that any smooth surface, with a non-constant mean curvature, unavoidably introduces a separatio...

María Egües (1917-2008) fue una investigadora y tecnóloga en el ámbito de los instrumentos ópticos; figura esencial para entender el desarrollo de la ingeniería óptica en las primeras décadas del franquismo. Partiendo de dos fotografías, hasta hace poco inéditas, que reflejan dos momentos cruciales de su vida profesional, este ensayo ofrece una ref...

There is a trend in optical system design toward explicitly considering real-world industrial demands in the metrics to be optimized, from which emerges a cost-performance trade-off. Another relevant recent tendency is the so-called end-to-end design, where the design metric is an expected quality index of the final image, after digital restoration...

The word iris comes from the ancient Greek [Ἶριν – Iris]. First, it was the name of the messenger God in the Illiad of Homer embodying the rainbow. Later, with the transit of the myth to the logos in the birth of Presocratic philosophy, the meaning turned into a meteorological phenomenon. Afterward, a crucial step occurred at some time around the 1...

La Sociedad Española de Óptica se fundó en el año 1968. Su constitución es la culminación de un largo proceso cuyos cimientos surgieron en la década de los años veinte y treinta del siglo XX, y cuyo antecesor inmediato fue el Comité Español de Óptica (CEO), creado en el año 1950. Un organismo internacional, la Comisión Internacional de Óptica (ICO)...

Resumen La ingeniería óptica, entendida como una rama de la ingeniería dedicada a los instrumentos ópticos, surgió en la Alemania de finales del siglo XIX. Los cimientos para el desarrollo de la ingeniería óptica en España tuvieron que esperar a la segunda década del siglo XX. La iniciativa coordinada de algunos ingenieros industriales civiles y té...

The Levi-Civita wavefront coupling problem consists of, given two prescribed wavefronts, obtaining a refractive or reflective surface coupling them. We propose a robust numerical method to solve Levi-Civita’s problem, whose rationale is to consider that Levi-Civita’s solutions are level surfaces of the point characteristic function established betw...

Monocular polyplopia (ghost or multiple images) is a serious visual impediment for some people who report seeing two (diplopia), three (triplopia) or even more images. Polyplopia is expected to appear if the point spread function (PSF) has multiple intensity cores (a dense concentration of a large portion of the radiant flux contained in the PSF) r...

Multifocal and/or extended depth-of-focus designs are widely used in many optical applications. In most of them, the optical configuration has axial symmetry. A usual design strategy consists of exploring the optimal wavefronts that emerging out of the optical system would provide the desired multifocal properties. Those properties are closely rela...

Multifocal lenses comprising progressive power surfaces are commonly used in contact and intraocular lens designs. Given a visual performance metric, a wavefront engineering approach to design such lenses is based on searching for the optimal wavefront at the exit pupil of the eye. Multifocal wavefronts distribute the energy along the different foc...

https://elpais.com/ciencia/2021-06-17/el-oftalmologo-que-utilizo-las-matematicas-para-entender-el-astigmatismo.html

The Point-Spread-Function (PSF) field characterizes the geometric and diffractive properties of most optical system designs for imaging applications. The conventional method of computing the PSF field is carried out in two steps: first, geometrical computation of the wave aberration function, and then, diffraction evaluation. That method usually ap...

Progressive addition lenses (PALs) contain a surface of spatially varying curvature, which supplies variable optical power for different viewing areas over the lens. We derive complete compatibility equations providing the exact magnitude of a cylinder along lines of curvature on any arbitrary PAL smooth surface. These equations reveal that, contra...

Progressive addition lenses contain a surface of spatially-varying curvature, which provides variable optical power for different viewing areas over the lens. We derive complete compatibility equations that provide the exact magnitude of cylinder along lines of curvatures on any arbitrary PAL smooth surface. These equations reveal that, contrary to...

Slides for the oral presentation at ICIP 2019.

Recently, some techniques for deblurring images having arbi- trarily shaped boundaries have been proposed. However, when we observe a blurry foreground (FG) object on a sharp background (BG) there is no abrupt transition between them. Because previous tech- niques are not designed to cop with a smooth transition area between FG and BG, they avoid i...

Arelevant problem in point-by-point scanning surface topography is to find scanning paths minimizing the overall measurement time.Weestablish a rigorous mathematical framework that allows us to state, for the first time, that circle involutes are the best candidates for such scanning paths maintaining a prescribed measurement accuracy condition.Wep...

We provide a method for efficiently computing the Point Spread Function field in axially symmetric optical systems tracing few rays. The method is based on the concept of effective object phase space and Chebyshev interpolations.

A relevant problem in point-by-point surface metrology is to find the set of points minimizing the overall measurement time. We show, through mathematical arguments, that selecting the sampling points along circle involutes is a good choice.

The Principle of Optics is definitely the most used optical book in the last sixty years and one of the great books of science of the twentieth century. It is, in fact, a reworking and extension of a book in German (Optik) previously written by Max Born. In this article, we intend to explain how the genesis of the Optik was and its subsequent trans...

Mi clásico favorito Pocas veces un científico es capaz de descubrir algo que haga temblar los mismos pilares sobre los que se asienta la física. Max Born (1882-1970) fue uno de estos privilegiados. A pesar de que por su humilde carácter él mismo no lo considerase como tal, su audaz interpretación estadística de la función de onda de Schrödinger sie...

Aspheres in optical design are frequently used to achieve high optical performance in imaging applications. However, manufacturing aspheres involves serious precision and cost issues that must be considered. We show that, by applying a hybrid digital-optical design approach, the amount of the asphericity cost in a single surface may be significantl...

Finding the optimal starting configuration in optical design, when image plane location is a design parameter, using a diapoint-based error function. ABSTRACT Typical error functions used in optical design (imaging applications) exhibit non-linear landscapes (with reference to the design parameters) with multiple minima. This makes optimization a c...

Purpose: Radial Refractive Gradient (RRG) spectacles are lenses specifically designed to minimize peripheral hyperopic defocus typically found in conventional spectacles. Our goals were: (1) to demonstrate a method to design such lenses; and (2) to quantify the exact foveal vision power errors induced by them. Methods: The design procedure was b...

La ciencia es una de las piezas culturales más relevantes de las so-ciedades contemporáneas. Aporta tres provechos esenciales para nuestro acer-vo civilizatorio: 1) acercamiento a la realidad, 2) resolución de problemas prác-ticos, y 3) pensamiento y praxis genuinamente humanizadores. Sin embargo, la ciencia no es la única manera legítima de acerca...

Phase space mapping, typically between an object and image plane, characterizes an optical system within a geometrical optics framework. We propose a novel conceptual frame to characterize the phase mapping in axially symmetric optical systems for arbitrary object locations, not restricted to a specific object plane. The idea is based on decomposin...

We address the problem of finding the optimal focus of an optical system with spherical aberration, under three optimization criteria: the classical optical root-mean-square second order moment minimization, the expected mean square error on the sensor, and the expected mean square error at the output of a Wiener restoration filter. We observe that...

We present a comprehensive procedure to simulate real-world scenes viewed through ophthalmic lenses. Such a method enables us to anticipate the effects on image formation of the following combined undesired optical defects typically found in ophthalmic lenses: blur, distortion, and chromatic aberration. Additionally, it helps in comparing the expec...

Resumen: La mirada artística puede servir como estímulo de la intuición creadora de conocimiento científico. Este trabajo pretende desarrollar esta premisa filosófica a través del ejemplo histórico de Leonardo da Vinci. Su estudio científico sobre la óptica y su creación artística pictórica pueden parecer, en primera instancia, inextricablemente un...

Purpose: Non-uniform magnification (distortion) and dioptric blur are two major undesired optical defects affecting vision when looking through progressive addition lenses (PALs) and studying them is potentially very valuable for PAL design. The major purpose of this paper is to analyse the relationship between dioptric power and magnification and...

When vision is affected simultaneously by presbyopia and myopia or hyperopia, a solution based on eyeglasses implies a surface with either segmented focal regions (e.g. bifocal lenses) or a progressive addition profile (PALs). However, both options have the drawback of reducing the field-of-view for each power position, which restricts the natural...

Max Born fue una figura clave en la revolución de la física cuántica del pasado siglo XX. Su vida, marcada por dos guerras mundiales, ejemplifica el despertar de la conciencia ética en la ciencia moderna. Así, según su pensamiento, la responsabilidad ética evita que la ciencia se convierta en "un simple instrumento de las industrias y de los gobier...

In a previous contribution [Appl. Opt. 51, 8599 (2012)10.1364/AO.51.008599APOPAI1559-128X], a coauthor of this work presented a method for reconstructing the wavefront aberration from tangential refractive power data measured using dynamic skiascopy. Here we propose a new regularized least squares method where the wavefront is reconstructed not onl...

The diopter power and magnification matrices characterize the first-order properties of ophthalmic lenses for different gaze directions. Therefore an efficient method to compute them is highly valuable in ophthalmic lens design and optical performance simulations. I present a novel method to numerically compute these matrices in ophthalmic lenses c...

A widespread type of multifocal intraocular lens (MIOL) is based on expanding the depth of focus with specific amounts of spherical aberration. However, knowing the optimal wavefront aberration for multifocality does not directly provide a MIOL geometry. To overcome this issue, we present a new strategy to design MIOLs. The method optimizes directl...

Aristotle was the first Greek author trying to give an explanation of the optical defects of vision. Within the framework of his theory of vision and with the help of numerous empirical observations of natural phenomena, he tried to explain why visual acuity is different from one subject to another and the existence of ametropias, differentiating b...

Presbyopia, understood as the age-related loss of ability to clearly see near objects, was known to ancient Greeks. However, few references to it can be found in ancient manuscripts. A relevant discussion on presbyopia appears in a book called Symposiacs written by Lucius Mestrius Plutarchus around 100 A.C. In this work, Plutarch provided four expl...

The need for affordable and sustainable ophthalmic systems for measurement and correction of refraction is well recognized. Power-adjustable spectacles based on the Alvarez principle (transversal lateral movement of two lenses) have emerged as an innovative technology for this purpose. Within this framework, our aim is to design a new power-adjusta...

The geometric point spread function (PSF) is an appropriate tool for modeling image degradation of an optical system, whenever the effect of diffraction is small compared to that of aberrations. The PSF is conventionally estimated by computing the density of ray intersections with the image plane (ray-counting method). We studied the effect of two...

The need for affordable and sustainable ophthalmic systems for measurement and correction of refraction is well-recognized. Power-adjustable spectacles based on the Alvarez principle (transversal lateral movement of two lenses) have emerged as an innovative technology for this purpose. Within this framework our aim is to design novel power-adjustab...

The aim of this work was to study, using numerical simulations, the attainable level of accuracy to reconstruct the wavefront aberrations from tangential refractive power data measured with dynamic skiascopy. Two mathematical methods have been implemented. The first one is based on curve integration of the curvature data, previously interpolated wi...

We present a comprehensive approach for the design of adjustable-focus lenses based on the Alvarez principle. The design methodology consists of dividing the lens into two parts: the inner, optical part, where the optical quality is optimized, and the outer, mechanical part, connecting the optical part to the frame. For the optical part, we present...

The accuracy of the reconstruction of the Gradient Refractive Index (GRIN) of the crystalline lens from optimization methods was evaluated. Different input data, including direction cosines of deflected rays, ray impacts obtained from ray tracing and optical path differences from Optical Coherence Tomography (OCT) were studied. Three different GRIN...

Power-adjustable spectacle lenses, based on the Alvarez-Lohmann principle, can be used to provide affordable spectacles for subjective refractive errors measurement and its correction. A new mechanical frame has been designed to maximize the advantages of this technology. The design includes a mechanism to match the interpupillary distance with tha...

A new and complete methodology of monofocal intraocular lens (IOL) design is presented aiming at isoplanatism, i.e. IOLs that provide the eye with optimized optical quality over a wide field of view (typically in a range of ten degrees). The methodology uses a merit function considering dimensional and biomechanical constraints, and a geometrical o...

Purpose: In a cataract procedure the crystalline lens is replaced by an Intraocular Lens (IOL), modifying the corneal (by the incision) and the internal aberration pattern (by the IOL). We studied ocular optical quality in patients with aspheric (Tecnis, Pharmacia) IOLs. We measured the change of corneal aberrations with cataract surgery and the ab...

Aspheric IOLs induce negative spherical aberration in order to emulate young crystalline lenses. We present optical aberrations in pseudophakic eyes, the effect of misalignment on optical performance, using customized eye models, and new aspheric designs.

The Hartmann-Shack wavefront sensor (HS) conventionally used in measuring the optical aberrations of the human eye estimates the slopes of the wavefront with a spatial resolution limited by the microlens size. We propose to use the HS sensor in a novel way to extend its accuracy for a given resolution by estimating the curvature of the wavefront ov...

Alvarez and Lohmann lenses are variable focus optical devices based on lateral shifts of two lenses with cubic-type surfaces. I analyzed the optical performance of these types of lenses computing the first order optical properties (applying wavefront refraction and propagation) without the restriction of the thin lens approximation, and the spot di...

Wave aberrations in the human eye are usually known with respect to the ideal spherical wavefront in the exit pupil. Using Kirchhoff’s diffraction theory, we have derived a diffraction integral to compute the optical field on the retina from the wave aberration data. We have proposed a numerical algorithm based on the Stamnes–Spjelkavik–Pedersen (S...

It is well known that the aberrations of the cornea are partially compensated by the aberrations of the internal optics of the eye (primarily the crystalline lens) in young subjects. This effect has been found not only for the spherical aberration, but also for horizontal coma. It has been debated whether the compensation of horizontal coma is the...

13 pages, 6 figures.-- To be submitted to "Óptica Pura y Aplicada". [ES] La óptica visual estudia al ojo humano como un sistema óptico especializado en formar imágenes. Se presenta una breve revisión del estado del arte de la óptica visual, resaltando los avances más importantes de los últimos años y enfatizando las cuestiones pendientes. También s...

We propose a complete methodology to develop custom monofocal Intraocular Lens (IOL) designs and evaluate their performance on-axis based on an analytical formulation. The analytical formulation was based on Gaussian and primary aberration theory applied to custom (individual biometric data) and realistic (multilayer cornea and thick IOL) pseudoaph...

We derive equations for defocus and primary spherical wave aberration coefficients caused by a shift in image plane of a perfect optical system. The spherical aberration equation is accurate at describing changes in the spherical aberration of an aberrated schematic eye.

Wavefront reconstruction from the transport-of-intensity equation (TIE) is a well-posed inverse problem given smooth signals and appropriate boundary conditions. However, in practice experimental errors lead to an ill-condition problem. A quantitative analysis of the effects of experimental errors is presented in simulations and experimental tests....

Optical models of the human cornea and tear film typically employ a single homogeneous cornea with an average refractive index. I propose to use a more realistic multilayer model based on morphological data from the literature. The mathematical methodology to derive the refractive power equation of this model is presented. Special attention is give...

A new wavefront sensing and reconstruction technique is presented. It is possible to measure Laplacian and gradient information of a wavefront with a Hartmann-Shack setup. By simultaneously using the Laplacian and gradient data we reconstruct the wavefront by sequentially solving two partial differential equations.