Fractal Light Vortices

Vortex lenses produce special wavefronts with zero-axial intensity, and helical phase structure. The variations of the phase and amplitude of the vortex produce a circular flow of energy that allows transmitting orbital angular momentum. This property is especially in optical trapping, because due to the orbital angular momentum of light, they have the ability to set the trapped particles into rotation. Vortex lenses engraved in diffractive optical elements have been proposed in the last few years. These lenses can be described mathematically as a two-dimensional (2D) function, which expressed in polar coordinates are the product of two different separable one-dimensional (1D) functions: One, depends only on the square of radial coordinate, and the other one depends linearly on the azimuthal coordinate and includes the topological charge. The 1D function that depends on the radial coordinate is known as a zone plate. Here, vortex lenses, constructed using different aperiodic zone plates, are reviewed. Their optical properties are studied numerically by computing the intensity distribution along the optical axis and the transverse diffraction patterns along the propagation direction. It is shown that these elements are able to create a chain of optical traps with a tunable separation, strength and transverse section

Influencia de los diferentes tipos de astigmatismo en la agudeza visual

[EN] Purpose To investigate the change in visual acuity (VA) produced by different types of astigmatism (on the basis of the refractive power and position of the principal meridians) on normal accommodating eyes. Methods The lens induced method was employed to simulate a set of 28 astigmatic blur conditions on different healthy emmetropic eyes. Additionally, 24 values of spherical defocus were also simulated on the same eyes for comparison. VA was measured in each case and the results, expressed in logMAR units, were represented against of the modulus of the dioptric power vector (blur strength). Results LogMAR VA varies in a linear fashion with increasing astigmatic blur, being the slope of the line dependent on the accommodative demand in each type of astigmatism. However, in each case, we found no statistically significant differences between the three axes investigated (0°, 45°, 90°). Non-statistically significant differences were found either for the VA achieved with spherical myopic defocus (MD) and mixed astigmatism (MA). VA with simple hyperopic astigmatism (SHA) was higher than with simple myopic astigmatism (SMA), however, in this case non conclusive results were obtained in terms of statistical significance. The VA achieved with imposed compound hyperopic astigmatism (CHA) was highly influenced by the eye's accommodative response. Conclusions VA is correlated with the blur strength in a different way for each type of astigmatism, depending on the accommodative demand. VA is better when one of the focal lines lie on the retina irrespective of the axis orientation; accommodation favors this situation.[ES] Objetivo Investigar el cambio en la agudeza visual (AV) producido por los diferentes tipos de astigmatismo (sobre la base del poder refractivo y la posición de los principales meridianos) en ojos con acomodación normal. Métodos Se utilizó el método de desenfoque inducido con lentes para simular un conjunto de veintiocho situaciones de desenfoque astigmático en diferentes ojos emetrópicos sanos. Además, se simularon veinticuatro valores de defecto esférico en los mismos ojos, a fines comparativos. Se midió la AV en cada caso, representándose los resultados, expresados en unidades logMAR, frente a los módulos del vector de potencia dióptrica (desenfoque). Resultados La escala LogMAR para AV varía de manera lineal, incrementando la distorsión astigmática, dependiendo la inclinación de la línea de la demanda acomodativa en cada tipo de astigmatismo. Sin embargo, en cada caso, no hallamos diferencias significativas entre los tres ejes analizados (0°, 45°, 90°). No se hallaron diferencias estadísticamente significativas en cuanto a la AV lograda con el defecto miópico esférico (MD) y astigmatismo mixto (MA). La AV con astigmatismo hipermetrópico simple (SHA) fue más elevada que con astigmatismo miópico simple (SMA). Sin embargo, en este caso se obtuvieron resultados no concluyentes en términos de significancia estadística. La AV lograda con astigmatismo hipermetrópico compuesto (CHA) se vio altamente influenciada por la respuesta acomodativa del ojo. Conclusiones La AV guarda relación con el desenfoque de modo diferente para cada tipo de astigmatismo, dependiendo de la demanda de acomodación. La AV es mejor cuando una de las líneas focales está en la retina con independencia de la orientación del eje; la acomodación favorece esta situación.This study was supported by the Ministerio de Economía y Competitividad and FEDER (Grant DPI2015-71256-R), and by the Generalitat Valenciana (Grant PROMETEOII-2014-072), Spain.Remón Martín, L.; Monsoriu Serra, JA.; Furlan, WD. (2017). Influence of different types of astigmatism on visual acuity. Journal of Optometry. 10(3):141-148. https://doi.org/10.1016/j.optom.2016.07.003S14114810

Fractal photon sieve

A novel focusing structure with fractal properties is presented. It is a photon sieve in which the pinholes are appropriately distributed over the zones of a fractal zone plate. The focusing properties of the fractal photon sieve are analyzed. The good performance of our proposal is demonstrated experimentally with a series of images obtained under white light illumination. It is shown that compared with a conventional photon sieve, the fractal photon sieve exhibits an extended depth of field and a reduced chromatic aberration.Comment: 6 pages, 5 figure

Diseño y desarrollo de un espectrómetro óptico versátil de bajo coste

[EN] In this work, the processes of designing, developing and prototyping an instrument to measure the visible spectrum is shown in detail. The objective is to obtain a low-cost device, reproducible and technically competitive with the commercial docent models. The obtained device is portable, adaptable, compact, economic and with high connectivity. The core of the project is the software, and its key point is the compatibility with any commercial camera and it can be run in different operative systems. For this prototype a commercial camera with USB connection has been considered in order to find a balance between price and resolution for the resulting device.[ES] En este trabajo se detalla el proceso de diseño, desarrollo y prototipado de un sistema de medida del espectro visible. El objetivo que hay que cumplir es la obtención de un dispositivo reproducible, competitivo en el aspecto técnico con modelos comerciales de docencia actuales, y económico. El dispositivo resultante reúne las características de ser portátil, versátil, compacto, económico y con alta conectividad. El centro del proyecto es el software, que como característica clave permite ser utilizado prácticamente con cualquier cámara comercial y ser ejecutado desde distintos sistemas operativos. El prototipado se ha realizado con una cámara comercial con conexión USB con el fin de encontrar un equilibrio entre asequibilidad y resolución del producto final. Tiene un precio 20 veces más económico y una resolución similar al espectrofotómetro comercial utilizado como referencia.Este trabajo ha sido financiado por el Ministerio de Economía y Competitividad y FEDER (Proyecto DPI2015-71256-R) y por la Generalitat Valenciana (Proyecto PROMETEOII-2014-072).Ferrando, V.; Monreal, J.; Furlan, WD.; Monsoriu Serra, JA. (2017). Diseño y desarrollo de un espectrómetro óptico versátil de bajo coste. Tecnica Industrial. (318):48-52. https://doi.org/10.23800/9984S485231

Proposal of a new diffractive corneal inlay to improve near vision in a presbyopic eye

[EN] A new class of diffraction-based corneal inlays for treatment of presbyopia is described. The inlay is intended to achieve an improvement of the near focus quality over previous designs. Our proposal is a two-zone hybrid device with separated amplitude and phase areas having a central aperture and no refractive power. An array of micro-holes is distributed on the surface of the inlay conforming a binary photon sieve. In this way, the central hole of the disk contributes to the zero order of diffraction, and the light diffracted by the micro-holes in the peripheral photon sieve produces a real focus for near vision. We employed ray-tracing software to study the performance of the new inlay in the Liou-Brennan model eye. The modulation transfer functions (MTFs) at the distance and near foci, and the area under the MTFs for different object vergences, were the merit functions used in the evaluation. The results were compared with those obtained with previous pure amplitude designs. Additionally, image simulations were performed with the inlays in the model eye to show the good performance of our proposal in improving the quality of the near vision. (C) 2020 Optical Society of AmericaMinisterio de Economia y Competitividad, Spain (2019/048, DPI 2015-71256-R); Conselleria d'Educacio, Investigacio, Cultura i Esport, Comunitat Valenciana, Spain (PROMETEO/2019/048). Portions of this work were presented at the Optics Meeting (RIAO), the Latinoamerican Meeting in Optics, Lasers and Applications (OPTILAS), and the Mexican Optics and Photonics Meeting (MOPM) in September 2019, Diffractive corneal inlays: ray tracing analysis in a model eye . D. Montagud Martinez and V. Ferrando acknowledge the financial support from the Universitat Politècnica de València, Spain (fellowships FPI 2016 and PAID 10 18, respectively).Montagud-Martínez, D.; Ferrando, V.; Monsoriu Serra, JA.; Furlan, WD. (2020). Proposal of a new diffractive corneal inlay to improve near vision in a presbyopic eye. Applied Optics. 59(13):D54-D58. https://doi.org/10.1364/AO.383581SD54D585913Lindstrom, R. L., MacRae, S. M., Pepose, J. S., & Hoopes, P. C. (2013). Corneal inlays for presbyopia correction. Current Opinion in Ophthalmology, 24(4), 281-287. doi:10.1097/icu.0b013e328362293eCharman, W. N. (2014). Developments in the correction of presbyopia II: surgical approaches. Ophthalmic and Physiological Optics, 34(4), 397-426. doi:10.1111/opo.12129Furlan, W. D., García-Delpech, S., Udaondo, P., Remón, L., Ferrando, V., & Monsoriu, J. A. (2017). Diffractive corneal inlay for presbyopia. Journal of Biophotonics, 10(9), 1110-1114. doi:10.1002/jbio.201600320Kipp, L., Skibowski, M., Johnson, R. L., Berndt, R., Adelung, R., Harm, S., & Seemann, R. (2001). Sharper images by focusing soft X-rays with photon sieves. Nature, 414(6860), 184-188. doi:10.1038/35102526Giménez, F., Monsoriu, J. A., Furlan, W. D., & Pons, A. (2006). Fractal photon sieve. Optics Express, 14(25), 11958. doi:10.1364/oe.14.011958Montagud-Martinez, D., Ferrando, V., Machado, F., Monsoriu, J. A., & Furlan, W. D. (2019). Imaging Performance of a Diffractive Corneal Inlay for Presbyopia in a Model Eye. IEEE Access, 7, 163933-163938. doi:10.1109/access.2019.2949223Montagud-Martínez, D., Ferrando, V., Monsoriu, J. A., & Furlan, W. D. (2019). Optical Evaluation of New Designs of Multifocal Diffractive Corneal Inlays. Journal of Ophthalmology, 2019, 1-6. doi:10.1155/2019/9382467Liou, H.-L., & Brennan, N. A. (1997). Anatomically accurate, finite model eye for optical modeling. Journal of the Optical Society of America A, 14(8), 1684. doi:10.1364/josaa.14.001684Alarcon, A., Canovas, C., Rosen, R., Weeber, H., Tsai, L., Hileman, K., & Piers, P. (2016). Preclinical metrics to predict through-focus visual acuity for pseudophakic patients. Biomedical Optics Express, 7(5), 1877. doi:10.1364/boe.7.00187

Optical Evaluation of New Designs of Multifocal Diffractive Corneal Inlays

[EN] Purpose. To assess the imaging properties of two different designs of a new concept of corneal inlays whose working principle is based on diffraction. Methods. The quality of the retinal images provided by Diffractive Corneal Inlays (DCIs) was evaluated theoretically in comparison with Small Aperture Corneal Inlay (SACI). ZEMAX OpticStudio software was employed for the simulations in an eye model with different pupil diameters (3.0 mm and 4.5 mm). The employed merit functions in the analysis were the Modulation Transfer Function (MTF), the area under the MTF (MTFa), and the Point Spread Function (PSF). Comparison was made with the SACI at different defocus conditions. Results. The bifocal nature of the DCIs was demonstrated in a model eye for the first time. It was shown that the intensity of the near focus depends on the radius of the central zone. Retinal image quality of the DCI was equal to or exceeded the SACI in the majority of visual conditions as was demonstrated with simulated images. Conclusions. A new customizable type of corneal inlays has been evaluated using objective numerical simulations. Improvements in imaging of near objects and in light throughput compared with the popular small aperture inlays were demonstrated. These findings open a new technical branch of minimally invasive surgical solutions for the treatment of presbyopia.D. Montagud-Martinez and V. Ferrando acknowledge the financial support from the Universitat Politècnica de València, Spain (fellowships FPI-2016 and PAID-10-18, respectively). This work was supported in part by the Ministerio de Economia y Competitividad, Spain, (grant DPI2015-71256-R) and by the Generalitat Valenciana (Grant PROMETEO/2019/048), Spain.Montagud-Martínez, D.; Ferrando, V.; Monsoriu Serra, JA.; Furlan, WD. (2019). Optical Evaluation of New Designs of Multifocal Diffractive Corneal Inlays. Journal of Ophthalmology. 2019:1-6. https://doi.org/10.1155/2019/9382467S162019Fricke, T. R., Tahhan, N., Resnikoff, S., Papas, E., Burnett, A., Ho, S. M., … Naidoo, K. S. (2018). Global Prevalence of Presbyopia and Vision Impairment from Uncorrected Presbyopia. Ophthalmology, 125(10), 1492-1499. doi:10.1016/j.ophtha.2018.04.013Furlan, W. D., García-Delpech, S., Udaondo, P., Remón, L., Ferrando, V., & Monsoriu, J. A. (2017). Diffractive corneal inlay for presbyopia. Journal of Biophotonics, 10(9), 1110-1114. doi:10.1002/jbio.201600320Kipp, L., Skibowski, M., Johnson, R. L., Berndt, R., Adelung, R., Harm, S., & Seemann, R. (2001). Sharper images by focusing soft X-rays with photon sieves. Nature, 414(6860), 184-188. doi:10.1038/3510252

Terahertz Sieves

[EN] Imaging at terahertz (THz) frequencies offers a great potential for applications including security screening, telecommunications biodetection, and spectroscopy. Some of these applications need specially designed lenses with customized characteristics that are not commercially available. In this letter, we present the THz sieves as a new kind of THz lenses. We demonstrate that these lenses improve the resolution of conventional zone plates constructed with the same level of detail. Amplitude and phase THz sieves were three-dimensional printed and tested experimentally. Excellent agreement was obtained between the experimental and calculated results.This work was supported in part by the Ministerio de Economia y Competitividad and FEDER, Spain, under Grant DPI2015-71256-R, in part by the Generalitat Valenciana under Grant PROMETEOII-2014-072, Spain, and in part by the National Center for Research and Development in Poland under Grant LIDER/020/319/L-5/13/NCBR/2014.Machado-Olivares, FJ.; Zagrajek, P.; Monsoriu Serra, JA.; Furlan, WD. (2018). Terahertz Sieves. IEEE Transactions on Terahertz Science and Technology. 8(1):140-143. https://doi.org/10.1109/TTHZ.2017.2762292S1401438

Perfiles de potencia de las lentes de contacto medidas con NIMO TR1504

This study was supported by the Ministerio de Economía y Competitividad and FEDER (Grant DPI2015-71256-R) and by the Generalitat Valenciana (Grant PROMETEOII-2014-072), Spain.Rodríguez-Vallejo, M.; Montagud-Martínez, D.; Monsoriu Serra, JA.; Furlan, WD. (2017). On the power profiles of contact lenses measured with NIMO TR1504. Journal of Optometry. 10(4):265-266. https://doi.org/10.1016/j.optom.2016.10.002S26526610

Diffractive Corneal Inlays: A New Concept for Correction of Presbyopia

A new class of corneal inlays for treatment of presbyopia is described, which uses diffraction as the working principle. The inlay consists of an opaque disk with a small central aperture surrounded by an array of micro-holes that are distributed following the order of a given Fresnel zone plate having N zones. In this way, the central hole of the disk produces an extension of the depth of focus of the eye for distance vision and contributes to the zero order of diffraction, and the light diffracted by the micro-holes in the periphery produces a real focus for near vision. In our general design, the number of zones and the diameter of the central hole are free parameters that can be used to design customized devices with different addition power and near-focus intensity. Two different designs are analyzed to show this property. In the analysis, we employed a ray tracing software to study the performance of the new inlays in the two different model eyes. The results are compared with those obtained with a model of the small-aperture inlay that is currently in the market. The different merit functions used in the comparison and the image simulations performed with the inlays in the model eyes show the excellent performance of our proposal