Projeto de um transdutor binocular utilizando extensometria e aplicação na pesagem rodoviária

With the passage of time, the variety of companies from each branch has gradually grown throughout the country. As a consequence, the logistics to attend to such demand has grown in the same proportion. One factor to highlight about this rapid growth is the increase of freight vehicles roaming the roads, often carrying loads over the limit established by law. At first it may seem that this would not bring any problem, however, note that an excessive number of overloads ends up deteriorating the asphalt, causing ondulations, potholes and other imperfections on the roads, which can cause accidents. In addition, the money spent for the maintenance of the roads is high. Thinking about it, it was established by law a regulation that restricts the weight limit for these vehicles, through axle weighing, subject to a fine. With this control the road floor is preserved for longer, requiring less maintenance expenses. The weighing stations use load cells to display the inferred weight, these cells use strain gages in its construction. The following work presents a methodology to dimension a binocular load cell, its main elements and its dimensioning. Showing how different materials can affect the dimensioning, so that can work satisfactorily. It also presents an overview of how are the parameters for weighing, and fines

Effects of age and optical blur on real depth stereoacuity

Stereoscopic depth perception utilizes the disparity cues between the images that fall on the retinae of the two eyes. The purpose of this study was to determine what role aging and optical blur play in stereoscopic disparity sensitivity for real depth stimuli. Forty-six volunteers were tested ranging in age from 15 to 60 years. Crossed and uncrossed disparity thresholds were measured using white light under conditions of best optical correction. The uncrossed disparity thresholds were also measured with optical blur (from +1.0D to +5.0D added to the best correction). Stereothresholds were measured using the Frisby Stereo Test, which utilizes a four-alternative forced-choice staircase procedure. The threshold disparities measured for young adults were frequently lower than 10 arcsec, a value considerably lower than the clinical estimates commonly obtained using Random Dot Stereograms (20 arcsec) or Titmus Fly Test (40 arcsec) tests. Contrary to previous reports, disparity thresholds increased between the ages of 31 and 45 years. This finding should be taken into account in clinical evaluation of visual function of older patients. Optical blur degrades visual acuity and stereoacuity similarly under white-light conditions, indicating that both functions are affected proportionally by optical defocus.

Cataract surgery: emotional reactions of patients with monocular versus binocular vision

Purpose: To analyze emotional reactions related to cataract surgery in two groups of patients (monocular vision - Group 1; binocular vision - Group 2). Methods: A transversal comparative study was performed using a structured questionnaire from a previous exploratory study before cataract surgery. Results: 206 patients were enrolled in the study, 96 individuals in Group 1 (69.3 +/- 10.4 years) and 110 in Group 2 (68.2 +/- 10.2 years). Most patients in group 1 (40.6%) and 22.7% of group 2, reported fear of surgery (p<0.001). The most important causes of fear were: possibility of blindness, ocular complications and death during surgery. The most prevalent feelings among the groups were doubts about good results and nervousness. Conclusion: Patients with monocular vision reported more fear and doubts related to surgical outcomes. Thus, it is necessary that phisycians considers such emotional reactions and invest more time than usual explaining the risks and the benefits of cataract surgery. Ouvir

3-D geometry reconstruction using a color image stereo pair and partial differential equations

[EN] In this work, we present a new model for a dense disparity estimation and the 3-D geometry reconstruction using a color image stereo pair. First, we present a brief introduction to the 3-D Geometry of a camera system. Next, we propose a new model for the disparity estimation based on an energy functional. We look for the local minima of the energy using the associate Euler-Langrage partial differential equations. This model is a generalization to color image of the model developed in, with some changes in the strategy to avoid the irrelevant local minima. We present some numerical experiences of 3-D reconstruction, using this method some real stereo pairs.

Regularizing a set of unstructured 3D points from a sequence of stereo images

[EN] In this paper we present a method for the regularization of a set of unstructured 3D points obtained from a sequence of stereo images. This method takes into account the information supplied by the disparity maps computed between pairs of images to constraint the regularization of the set of 3D points. We propose a model based on an energy which is composed of two terms: an attachment term that minimizes the distance from 3D points to the projective lines of camera points, and a second term that allows for the regularization of the set of 3D points by preserving discontinuities presented on the disparity maps. We embed this energy in a 2D finite element method. After minimizing, this method results in a large system of equations that can be optimized for fast computations. We derive an efficient implicit numerical scheme which reduces the number of calculations and memory allocations.

Studio ed implementazione di algoritmi di stereo vision in ambito mobile: l'applicazione "SuperStereo"

L'analisi di un'immagine con strumenti automatici si è sviluppata in quella che oggi viene chiamata "computer vision", la materia di studio proveniente dal mondo informatico che si occupa, letteralmente, di "vedere oltre", di estrarre da una figura una serie di aspetti strutturali, sotto forma di dati numerici. Tra le tante aree di ricerca che ne derivano, una in particolare è dedicata alla comprensione di un dettaglio estremamente interessante, che si presta ad applicazioni di molteplici tipologie: la profondità. L'idea di poter recuperare ciò che, apparentemente, si era perso fermando una scena ed imprimendone l'istante in un piano a due dimensioni poteva sembrare, fino a non troppi anni fa, qualcosa di impossibile. Grazie alla cosiddetta "visione stereo", invece, oggi possiamo godere della "terza dimensione" in diversi ambiti, legati ad attività professionali piuttosto che di svago. Inoltre, si presta ad utilizzi ancora più interessanti quando gli strumenti possono vantare caratteristiche tecniche accessibili, come dimensioni ridotte e facilità d'uso. Proprio quest'ultimo aspetto ha catturato l'attenzione di un gruppo di lavoro, dal quale è nata l'idea di sviluppare una soluzione, chiamata "SuperStereo", capace di permettere la stereo vision usando uno strumento estremamente diffuso nel mercato tecnologico globale: uno smartphone e, più in generale, qualsiasi dispositivo mobile appartenente a questa categoria.

Callosal connections of primary visual cortex predict the spatial spreading of binocular rivalry across the visual hemifields

In binocular rivalry, presentation of different images to the separate eyes leads to conscious perception alternating between the two possible interpretations every few seconds. During perceptual transitions, a stimulus emerging into dominance can spread in a wave-like manner across the visual field. These traveling waves of rivalry dominance have been successfully related to the cortical magnification properties and functional activity of early visual areas, including the primary visual cortex (V1). Curiously however, these traveling waves undergo a delay when passing from one hemifield to another. In the current study, we used diffusion tensor imaging (DTI) to investigate whether the strength of interhemispheric connections between the left and right visual cortex might be related to the delay of traveling waves across hemifields. We measured the delay in traveling wave times (ΔTWT) in 19 participants and repeated this test 6 weeks later to evaluate the reliability of our behavioral measures. We found large interindividual variability but also good test-retest reliability for individual measures of ΔTWT. Using DTI in connection with fiber tractography, we identified parts of the corpus callosum connecting functionally defined visual areas V1-V3. We found that individual differences in ΔTWT was reliably predicted by the diffusion properties of transcallosal fibers connecting left and right V1, but observed no such effect for neighboring transcallosal visual fibers connecting V2 and V3. Our results demonstrate that the anatomical characteristics of topographically specific transcallosal connections predict the individual delay of interhemispheric traveling waves, providing further evidence that V1 is an important site for neural processes underlying binocular rivalry.