An approach to coded structured light to obtain three dimensional information

The human visual ability to perceive depth looks like a puzzle. We perceive three-dimensional spatial information quickly and efficiently by using the binocular stereopsis of our eyes and, what is mote important the learning of the most common objects which we achieved through living. Nowadays, modelling the behaviour of our brain is a fiction, that is why the huge problem of 3D perception and further, interpretation is split into a sequence of easier problems. A lot of research is involved in robot vision in order to obtain 3D information of the surrounded scene. Most of this research is based on modelling the stereopsis of humans by using two cameras as if they were two eyes. This method is known as stereo vision and has been widely studied in the past and is being studied at present, and a lot of work will be surely done in the future. This fact allows us to affirm that this topic is one of the most interesting ones in computer vision. The stereo vision principle is based on obtaining the three dimensional position of an object point from the position of its projective points in both camera image planes. However, before inferring 3D information, the mathematical models of both cameras have to be known. This step is known as camera calibration and is broadly describes in the thesis. Perhaps the most important problem in stereo vision is the determination of the pair of homologue points in the two images, known as the correspondence problem, and it is also one of the most difficult problems to be solved which is currently investigated by a lot of researchers. The epipolar geometry allows us to reduce the correspondence problem. An approach to the epipolar geometry is describes in the thesis. Nevertheless, it does not solve it at all as a lot of considerations have to be taken into account. As an example we have to consider points without correspondence due to a surface occlusion or simply due to a projection out of the camera scope. The interest of the thesis is focused on structured light which has been considered as one of the most frequently used techniques in order to reduce the problems related lo stereo vision. Structured light is based on the relationship between a projected light pattern its projection and an image sensor. The deformations between the pattern projected into the scene and the one captured by the camera, permits to obtain three dimensional information of the illuminated scene. This technique has been widely used in such applications as: 3D object reconstruction, robot navigation, quality control, and so on. Although the projection of regular patterns solve the problem of points without match, it does not solve the problem of multiple matching, which leads us to use hard computing algorithms in order to search the correct matches. In recent years, another structured light technique has increased in importance. This technique is based on the codification of the light projected on the scene in order to be used as a tool to obtain an unique match. Each token of light is imaged by the camera, we have to read the label (decode the pattern) in order to solve the correspondence problem. The advantages and disadvantages of stereo vision against structured light and a survey on coded structured light are related and discussed. The work carried out in the frame of this thesis has permitted to present a new coded structured light pattern which solves the correspondence problem uniquely and robust. Unique, as each token of light is coded by a different word which removes the problem of multiple matching. Robust, since the pattern has been coded using the position of each token of light with respect to both co-ordinate axis. Algorithms and experimental results are included in the thesis. The reader can see examples 3D measurement of static objects, and the more complicated measurement of moving objects. The technique can be used in both cases as the pattern is coded by a single projection shot. Then it can be used in several applications of robot vision. Our interest is focused on the mathematical study of the camera and pattern projector models. We are also interested in how these models can be obtained by calibration, and how they can be used to obtained three dimensional information from two correspondence points. Furthermore, we have studied structured light and coded structured light, and we have presented a new coded structured light pattern. However, in this thesis we started from the assumption that the correspondence points could be well-segmented from the captured image. Computer vision constitutes a huge problem and a lot of work is being done at all levels of human vision modelling, starting from a)image acquisition; b) further image enhancement, filtering and processing, c) image segmentation which involves thresholding, thinning, contour detection, texture and colour analysis, and so on. The interest of this thesis starts in the next step, usually known as depth perception or 3D measurement.

Una memoria, un testimonio: Alfredo Pareja Diezcanseco, el mecenas (Testimonios)

El texto es un testimonio de dimensiones poco abordadas de Alfredo Pareja: el lado humano del diplomático, del docente en el extranjero, de integrante del Grupo de Guayaquil. Principalmente reseña el nacimiento de un espacio clave de recuperación de la memoria: el Archivo Histórico y la biblioteca especializada del Ministerio de Relaciones Exteriores del Ecuador. Durante tres años, desde 1981, se trabajó en una pequeña oficina, elaborando fichas a partir de manuscritos, pergaminos y demás documentos que allí reposaban, Pareja veía necesario este rescate para la construcción de la historia del país. A partir de ésta y de otras fuentes -coloniales y del siglo XIX, hasta entonces desconocidas o interpretadas de diferente modo por los territorialistas ecuatorianos-, Pareja planteó una nueva interpretación del conflicto limítrofe con Perú, y sostuvo la necesidad de un acuerdo de paz, ello implicaba la aceptación del Protocolo de Río de Janeiro, situación que despertó en su contra muchos comentarios enconados, pero que formó parte de la tesis que prevaleció. El Archivo Histórico «Alfredo Pareja Diezcanseco» se inauguró en julio de 1996.

José Donoso: el escritor chileno en el laberinto de sus papeles íntimos (Crítica)

En este artículo se pasa revista a cierto desarrollo de la vida interna que tuvo José Donoso, gracias a manuscritos íntimos publicados y estudiados por su hija Pilar en el libro titulado Correr el tupido velo. Se ofrecen a las consideraciones de la crítica literaria perspectivas originales para entender el proceso creativo del autor de El obsceno pájaro de la noche, así como las tomas de posturas sentimentales de Donoso en relación con su esposa, sus opiniones en secreto respecto a la adopción de su hija Pilar, y sus diversas ideas en relación a su vida antes y después del golpe de Estado del general Augusto Pinochet en 1973. Se ponen de relieve también los criterios de la propia hija ante la lectura de estos interesantes materiales autobiográficos, con el fin de entender paranoias, neurosis y homosexualidad del propio José Donoso.

¿Trasplantes incaicos o etnogénesis poscolonial? El origen de los salasacas de la Sierra ecuatoriana (Estudios)

The salasacas are an indigenous group with a controversial history of origen. Many manuscripts state that they descend from an uprooted Inca population that traveled north from present Bolivia to their new settlement that is now Ecuador. The article presents an alternative narrative that identifies three separate migrations to Salasaca, by different indigenas groups, in the Sixteenth Century. It shows that the modern Salasacan nationality emerged during colonial and postcolonial transformations. It contends that the ethnic distinction of the salasacas is due to the fact that they opted to collectively unite as one solid ethnic group in order to remain as an Indigenas enclave in a region that was experiencing whitening or widespread emergence of half castes.

Do seed lists have a future?

In the 1960s Taxon published articles aimed at improving botanical Seed Lists. We compared suggestions made then with the situation in 2007. Sadly the majority of problems raised in the original manuscripts were still evident today. Botanic gardens must improve if this practice is to survive.

Attention disengagement in children with developmental coordination disorder

Purpose. Previous research has shown that children with Developmental Coordination Disorder (DCD) have poorly developed strategies for allocating attention. This study examines the allocation of attention and integration of visuo-spatial and motor systems in children with DCD in a motor (look+hit condition) and a motor-free (look condition) task. Method. Three groups of control children were used to compare the performance of a group of children with DCD. Children were seated in front of a central fixation point and six peripheral targets, and were asked to look at or hit targets when illuminated. Saccade/hand movement latencies were measured on gap trials (gap between fixation offset and target onset) and overlap trials (fixation offset and target onset overlapped). Results. DCD children were not slower than controls to disengage attention during the look condition. However, during the look+hit condition the DCD children showed a prolonged disengagement period, which was also seen in younger control children. Conclusions. The results suggest that DCD children may have deficits in the allocation of attention for action, in both the speed of onset of a movement and the accuracy of the movement. It is concluded that attention disengagement may contribute to problems of visuo-motor integration in DCD.

High frequency scattering by convex curvilinear polygons

We consider the scattering of a time-harmonic acoustic incident plane wave by a sound soft convex curvilinear polygon with Lipschitz boundary. For standard boundary or finite element methods, with a piecewise polynomial approximation space, the number of degrees of freedom required to achieve a prescribed level of accuracy grows at least linearly with respect to the frequency of the incident wave. Here we propose a novel Galerkin boundary element method with a hybrid approximation space, consisting of the products of plane wave basis functions with piecewise polynomials supported on several overlapping meshes; a uniform mesh on illuminated sides, and graded meshes refined towards the corners of the polygon on illuminated and shadow sides. Numerical experiments suggest that the number of degrees of freedom required to achieve a prescribed level of accuracy need only grow logarithmically as the frequency of the incident wave increases.

Entre moralité et politique: l’éducation de Louis XV et la question de l’instruction financière du prince sous l’Ancien Régime

Studies on princely education rarely focus on the training received by future kings to perform one of their key functions – supervising the finances of the monarchy. Failure to address this issue is all the more surprising than one of the major consequences of Louis XIV’s coronation was to grant the king the direction of finances until the French Revolution, thus raising the issue of the financial education of the prince. Based on a largely unpublished body of primary sources, especially several manuscripts specifically written for the financial education of Louis XV and princes in the XVIIIth century, this article explores the teaching approaches and programme of a highly technical nature that the king’s tutors considered essential to the monarch’s duties.

From hieroglyphics to Isotype: a visual autobiography (Otto Neurath)

Otto Neurath (1882–1945) wrote From hieroglyphics to Isotype during the last two years of his life and this is the first publication of the text in full, carefully edited from the original manuscripts. He called it a 'visual autobiography', in which he documents the importance of visual material to him from his earliest years to his professional activity with the picture language of Isotype. Neurath draws clear links between the stimulus he received as a boy from illustrated books, toys and exhibitions to the considered work in visual education that occupied him for the last two decades of his life. This engaging and informal account gives a rich picture of Central European culture around the turn of the twentieth century, seen through the eyes of Neurath's insatiable intelligence, as well as a detailed exposition of the technique of Isotype, a milestone of modern graphic design. This edition includes the numerous illustrations intended by Neurath to accompany his text, and is completed by an extensive appendix showing examples from the rich variety of graphic material that he collected.

Bioscience Horizons: the national journal of undergraduate research

Bioscience Horizons (BH)commenced publication in 2008 and features research papers and reviews written by graduating UK bioscience students. The journal is run by a consortium of UK universities (the Universities of Nottingham, Reading, Leeds and Chester) in association with Oxford University Press. Its submissions encompass the full range of subjects taught by UK bioscience departments, ranging from agronomy to zoology and including animal behaviour, cancer research, environmental biology, microbial sciences, molecular biology, pharmacolgy, primatology, taxonomy and other areas. BH receives manuscripts from recent graduates (with a bachelor of science or equivalent first degree) describing research carried out during their undergraduate studies, usually as a final-year research project. All submissions undergo expert review and have to meet strict criteria for scientific excellence and originality. Articles are written by a single author and published with the agreement of the graduate's home university department. The journal has an ISSN number and is open-access; articles are freely 'cite-able' contributions to the bioscience research literature.

The Clitherow manuscript of 'The Destruction of Hierusalem’

This essay discusses the never before seen early modern manuscript of an amateur play called 'The Destruction of Hierusalem' that the author discovered at the London Metropolitan Archives.