Detección del fenómeno de Bell previo al reflejo pupilar a la luz

Contribución como póster al Simposio de Ciencias de la Visión en la XI Reunión Nacional de ÓpticaEl desarrollo de un video-oculógrafo binocular con resolución 15 micras y 4 ms orientado a la caracterización de los reflejos pupilares ha revelado la existencia de un movimiento de elevación del globo ocular, conocido como fenómeno de Bell, previo al reflejo pupilar a la luz. Además, su uso para el análisis del reflejo pupilar a la luz ha confirmado que las respuestas pupilares directa y consensual no presentan ninguna diferencia temporal apreciabl

Targetless image-based method for measuring displacements and strains on concrete surfaces with a consumer camera

Measurement of concrete strain through non-invasive methods is of great importance in civil engineering and structural analysis. Traditional methods use laser speckle and high quality cameras that may result too expensive for many applications. Here we present a method for measuring concrete deformations with a standard reflex camera and image processing for tracking objects in the concretes surface. Two different approaches are presented here. In the first one, on-purpose objects are drawn on the surface, while on the second one we track small defects on the surface due to air bubbles in the hardening process. The method has been tested on a concrete sample under several loading/unloading cycles. A stop-motion sequence of the process has been captured and analyzed. Results have been successfully compared with the values given by a strain gauge. Accuracy of our methods in tracking objects is below 8 μm, in the order of more expensive commercial devices.The authors acknowledge the support of the Spanish Ministerio de Economía y Competitividad through the project BIA2011-22704, the Generalitat Valenciana through the project PROMETEO/2011/021 and GV/2013/009 and the University of Alicante through the project GRE13-10

Method for targetless tracking subpixel in-plane movements

We present a targetless motion tracking method for detecting planar movements with subpixel accuracy. This method is based on the computation and tracking of the intersection of two nonparallel straight-line segments in the image of a moving object in a scene. The method is simple and easy to implement because no complex structures have to be detected. It has been tested and validated using a lab experiment consisting of a vibrating object that was recorded with a high-speed camera working at 1000 fps. We managed to track displacements with an accuracy of hundredths of pixel or even of thousandths of pixel in the case of tracking harmonic vibrations. The method is widely applicable because it can be used for distance measuring amplitude and frequency of vibrations with a vision system.Generalitat Valenciana (Regional Government of Valencia) (PROMETEO/2011/021); Ministerio de Economía y Competitividad (Ministry of Economy and Competitiveness) (BIA2011-22704); Universidad de Alicante (GRE13-10)

High-speed video-oculography applied to assess pupil light reflex

Póster presentado en el VII European/ I World Meeting in Visual and Physiological OpticsEye response to light exposure is usually described through the pupillary light reflex, which controls the pupil diameter and allows for testing the sensory and motor functions of the eye. We have arranged an experimental setup and developed a procedure in order to improve the video-oculography experiment through high-speed imaging. The technique has been applied over eleven people distinguishing between consensual and direct pupillary light reflexes and analyzing the eye dominance. We found no significant differences. Moreover, obtained time parameters describing the pupil light reflex agree with those from literature.The authors acknowledge the projects BIA2011-22704, GV/2013/009 and PROMETEO/ 2011/021. A. B. Roig acknowledges a grant from Cajamurcia

A high-resolution binocular video-oculography system: assessment of pupillary light reflex and detection of an early incomplete blink and an upward eye movement

Background: The pupillary light reflex characterizes the direct and consensual response of the eye to the perceived brightness of a stimulus. It has been used as indicator of both neurological and optic nerve pathologies. As with other eye reflexes, this reflex constitutes an almost instantaneous movement and is linked to activation of the same midbrain area. The latency of the pupillary light reflex is around 200 ms, although the literature also indicates that the fastest eye reflexes last 20 ms. Therefore, a system with sufficiently high spatial and temporal resolutions is required for accurate assessment. In this study, we analyzed the pupillary light reflex to determine whether any small discrepancy exists between the direct and consensual responses, and to ascertain whether any other eye reflex occurs before the pupillary light reflex. Methods: We constructed a binocular video-oculography system two high-speed cameras that simultaneously focused on both eyes. This was then employed to assess the direct and consensual responses of each eye using our own algorithm based on Circular Hough Transform to detect and track the pupil. Time parameters describing the pupillary light reflex were obtained from the radius time-variation. Eight healthy subjects (4 women, 4 men, aged 24–45) participated in this experiment. Results: Our system, which has a resolution of 15 microns and 4 ms, obtained time parameters describing the pupillary light reflex that were similar to those reported in previous studies, with no significant differences between direct and consensual reflexes. Moreover, it revealed an incomplete reflex blink and an upward eye movement at around 100 ms that may correspond to Bell’s phenomenon. Conclusions: Direct and consensual pupillary responses do not any significant temporal differences. The system and method described here could prove useful for further assessment of pupillary and blink reflexes. The resolution obtained revealed the existence reported here of an early incomplete blink and an upward eye movement.The authors acknowledge the support of the Spanish Ministerio de Economía y Competitividad through the project BIA2011-22704 and the Generalitat Valenciana through the projects GV/2013/009 and PROMETEO/2011/021. A. B. Roig acknowledges a grant from Cajamurcia

Elementos de fase multifocales y de foco extenso programables bajo iluminación gaussiana

En este trabajo se presenta la propuesta y estudio teórico del comportamiento de nuevas máscaras de fase multifocales bajo incidencia gaussiana. Dichas máscaras pueden ser implementables en tiempo real sobre pantallas de cristal líquido en fase nemática (o de posible fabricación en lentes oftálmicas convencionales). Dichos elementos proporcionan un número de focos a elección entre dos posiciones fijas o una elevada profundidad de foco. Las aplicaciones de este tipo de elementos pueden ser diversas, desde su utilización en el campo oftalmológico como lentes intraoculares multifocales correctoras de ametropías esféricas y presbicia a su uso posible en técnicas de superresolución axial

Three-dimensional planar object tracking with sub-pixel accuracy

Subpixel techniques are commonly used to increase the spatial resolution in tracking tasks. Object tracking with targets of known shape permits obtaining information about object position and orientation in the three-dimensional space. A proper selection of the target shape allows us to determine its position inside a plane and its angular and azimuthal orientation under certain limits. Our proposal is demonstrated both numerical and experimentally and provides an increase the accuracy of more than one order of magnitude compared to the nominal resolution of the sensor. The experiment has been performed with a high-speed camera, which simultaneously provides high spatial and temporal resolution, so it may be interesting for some applications where this kind of targets can be attached, such as vibration monitoring and structural analysis.The authors acknowledge the support of the Spanish Ministerio de Economía y Competitividad through the project BIA2011-22704 and the Generalitat Valenciana through the projects GV/2013/009 and PROMETEO/ 2011/021. A. B. Roig acknowledges a grant from Cajamurcia

Effective focal length through a microscope

Póster presentado en el VII European/ I World Meeting in Visual and Physiological OpticsThe optical power of a thick spherical lens and its Coddington shape factor are essential magnitudes that characterize its image quality. We propose an experimental procedure and apparatus that allow accurate determination of those magnitudes for any spherical lens from geometrical measurements. It overcomes the drawbacks of other devices that need of the refractive index or may damage the lens surfaces, like spherometers, and provides similar results to commercial lensmeters.The authors acknowledge the projects BIA2011-22704, GV/2013/009 and PROMETEO/ 2011/021. J. Espinosa thanks R. Tomás the provisioning. A. B. Roig acknowledges a grant from Cajamurcia

Methods and algorithms for video-based multi-point frequency measuring and mapping

Software for video-based multi-point frequency measuring and mapping: http://hdl.handle.net/10045/53429Object vibrations and movements can be detected through changes in its luminance. In this paper, we demonstrate that we can obtain the vibration frequency of all vibrating targets in the sequence simultaneously through the analysis of local neighborhoods. The study is completed with a short-time Fourier analysis so that changes in the movement frequencies are also accounted. We also show that this information can be displayed like a color frequency map that can be superimposed to the video sequence providing a whole description of the analyzed sequence. The method can be used to analyze complex structures since their different vibrating parts can be visualized at a glance. The main algorithms, methods and some sequences are freely downloadable so that new applications and procedures can be implemented by the scientific community.The authors acknowledge the support of the Spanish Ministerio de Economía y Competitividad through the project BIA2011-22704

Correlation between the dioptric power, astigmatism and surface shape of the anterior and posterior corneal surfaces

A knowledge of the shape of the cornea is of major importance for the planning and monitoring of surgery, and for the correct diagnosis of corneal diseases. Many authors have studied the geometry of the second corneal surface in the central region and it has been stated that there is a high correlation between the central radii of curvature and asphericities of the two corneal surfaces. In this work we extend this study to a larger, central, 6 mm diameter of the cornea. Surface height data, obtained with an Oculus Pentacam from 42 eyes of 21 subjects, were analysed to yield surface power vectors. Corneal heights of both surfaces were also decomposed into low order Zernike polynomials and the correlations between each of the power vectors and low-order Zernike coefficients for the two surfaces were studied. There was not only a strong correlation between spherical powers and Zernike defocus coefficients, but also between the astigmatic components. The correspondence between the astigmatism in both surfaces found here can be of the utmost importance in planning optical surgery, since perfect spherical ablation of the first surface does not assure total correction of corneal astigmatism.This work has been partially supported by the Spanish Ministry of Education and Science through the project nr. FIS2005-05053. Julian Espinosa and Jorge Perez acknowledge financial support from the University of Alicante through the project GRE07-7P. Henryk Kasprzak acknowledges the University of Alicante for its economical support through the project Senior 08/07