Combining sparse and dense methods in 6D Visual Odometry

13th International Conference on Autonomous Robot Systems (Robotica), 2013, Lisboa

Real-Time Visual Ground-Truth System for Indoor Robotic Applications

The robotics community is concerned with the ability to infer and compare the results from researchers in areas such as vision perception and multi-robot cooperative behavior. To accomplish that task, this paper proposes a real-time indoor visual ground truth system capable of providing accuracy with at least more magnitude than the precision of the algorithm to be evaluated. A multi-camera architecture is proposed under the ROS (Robot Operating System) framework to estimate the 3D position of objects and the implementation and results were contextualized to the Robocup Middle Size League scenario.

Alterações da função visual e da qualidade de vida relacionada com a saúde em indivíduos idosos

RESUMO: Introdução: A visão é um sentido fundamental na relação do indivíduo com os mais variados ambientes, sendo elemento central na funcionalidade e independência do idoso, qualquer perturbação da função visual provoca limitações na qualidade de vida. As alterações demográficas em curso caracterizam-se pelo envelhecimento progressivo da população, paralelamente constata-se um aumento da prevalência de perturbações do sistema visual com alteração da função e do funcionamento visual. Considerando que os indivíduos idosos são mais dependentes da visão, e que não existem para esta área estudos desenvolvidos em Portugal, esta investigação tem como fundamento analisar a influência que a perturbação da função visual em indivíduos com 65 ou mais anos tem na qualidade de vida relacionada com a saúde. Estudaram-se também as características sócio-demográficas dos indivíduos participantes, da saúde visual e a percepção da saúde geral, bem como identificaram se junto dos idosos participantes e de Médicos especialistas em Medicina Geral e Familiar perspectivas sobre perturbações da função visual e envelhecimento. Desenho de estudo: Estudo transversal, caso-controlo e descritivo-exploratório. Materiais e Métodos: A partir de uma população de 112 indivíduos com 65 ou mais anos, frequentadores de várias instituições de apoio social do Concelho de Loures e de idosos frequentadores/institucionalizados da Mansão de Santa Maria de Marvila, unidade orgânica da Fundação D. Pedro IV, foram incluídos no estudo 90 (80,4%). Após consentimento informado, procedeu-se à avaliação da função visual nos Laboratórios de Ortóptica da Escola Superior de Tecnologia de Saúde de Lisboa, onde também se aplicaram o Questionário de Funcionamento Visual VFQ-25 e uma questão aberta para o tipo de dificuldades de visão sentidas durante o último ano. Aplicou-se ainda, em ambiente virtual, uma pergunta aberta a Médicos especialistas em Medicina Geral e Familiar para aspectos relacionados com o diagnóstico/suspeita relativamente tardio de perturbações da função visual. Procedeu-se ao tratamento descritivo das características sócio-demográficas, da percepção de saúde geral e da saúde visual e das respostas dos idosos e dos médicos. Analisou-se a relação entre função visual e qualidade de vida relacionada com a saúde aplicando o teste não-paramétrico de Mann-Whitney. Resultados: Constatou-se que os indivíduos da amostra são maioritariamente do género feminino (71,1%), casados (41,1%), detentores de baixos níveis de escolaridade em que 63,3% apenas frequentou/concluiu o 1º ciclo do ensino básico e quase na sua totalidade reformados (88,9%). Verifica-se que 77,8% dos idosos percepciona a sua saúde geral como razoável ou boa. Da mesma forma, 86,7% dos indivíduos têm a função visual alterada devido principalmente à alteração da acuidade visual para longe (86,7%), registando-se que 65,5% dos olhos tinham uma acuidade visual igual ou superior a 5/10. Outras dimensões que contribuíram para a alteração da função visual contam-se a sensibilidade ao contraste (63,3%), estereopsia (51,1%), visão cromática (38,9%) e a motilidade ocular (25,6%). Obtiveram-se assim maiores pontuações para as diversas escalas do questionário VFQ-25 em indivíduos com função visual alterada exceptuando nas escalas actividades de perto, condução e dependência. Verificou-se portanto existir relação entre alteração da função visual e perturbação da qualidade de vida relacionada com a saúde. À questão colocada aos idosos, 42,6% não manifestou qualquer razão para que visse mal/sentisse dificuldades de visão durante o último ano. A diminuição da acuidade visual para longe/perto foi referida por 20,5% dos indivíduos, seguido pela deterioração do estado de saúde geral e ocular por 15%. As respostas do Médicos especialistas em Medicina Geral e Familiar sobre razões para a suspeita/diagnóstico relativamente tardia das perturbações da função visual, indicam a iliteracia dos idosos para a saúde da visão e semiologia ocular (34%), a baixa formação/informação dos Médicos de Medicina Geral e Familiar na área da saúde da visão (22%) e a pouca acessibilidade e resposta demorada/ineficaz dos serviços de oftalmologia do SNS (20%) como principais motivos para os assuntos questionados.Conclusões: As alterações do sistema visual com impacto na função e no funcionamento visual alteram a qualidade de vida relacionada com a saúde, devido principalmente à alteração da acuidade visual para longe. Os idosos do estudo não valorizam a saúde visual ao percepcionarem positivamente a saúde geral e a saúde visual relativamente à avaliação da função visual. É fundamental definir estratégias e programas de literacia para a saúde da visão para toda a população, não apenas destinados a idosos. Sugere-se repensar o modelo de formação base dos Médicos com especial incidência na área da saúde da visão, com necessidades sentidas de formação/informação. As respostas obtidas dos idosos e dos Médicos indicaram existir fragilidades na saúde da visão, necessário repensar o modelo de prestação de cuidados de saúde nesta área. Esta investigação permitiu ao autor uma reflexão sobre as temáticas relacionadas com o envelhecimento levando a uma mudança de atitudes e comportamento na abordagem profissional a indivíduos idosos, promovendo autonomia nas escolhas e decisões em questões de saúde, na criação de estratégias para lidar com o problema de visão e na adaptação à nova condição de saúde da visão.---------------ABSTRACT:Purpose: The vision is a fundamental sense in the individual's relationship with the most varied environments, a central element in the functionality and independence of the elderly, any disturbance of visual function causes limitations in quality of life. The current demographic changes are characterized by progressive aging of population, there has been a parallel increase in the prevalence of disorders of the visual system by changing the visual function and functioning. Whereas the elderly are more dependent on vision, and there are no studies in this area developed in Portugal, this research is based analyze the influence that the disturbance of visual function in subjects aged 65 years or more has on the health related quality of life. We studied also the socio-demographic characteristics of the subjects, the eye health and general health perception, and identified themselves with the elderly participants and medical specialists in Family General Medicine perspective on disorders of visual function and aging. Design: Cross-sectional study, case control, descriptive and exploratory. Methods: From a population of 112 people with 65 or more years, regulars of various social welfare institutions of the Municipality of Loures and elderly regulars/institutionalized the Mansion of Santa Maria de Marvila, organic unity of the Foundation D. Pedro IV, were included 90 (80.4%). After informed consent, proceeded to the assessment of visual function in the Laboratories of Orthopticsof the School of Health Technology of Lisbon, where he also applied the Visual Functioning Questionnaire VFQ-25 and an open question for the type of vision difficulties experienced during the last year. Was applied also in a virtual environment, an open question to Doctors specialists in family general medicine related to the diagnosis/suspected relatively late disturbance of visual function. We carried out the descriptive treatment of socio-demographic characteristics, perception of general health and eye health and the responses of older people and doctors. We analyzed the relationship between visual function and quality of life related to health by applying the nonparametric Mann-Whitney test. Results: We found that individuals in the sample are mostly female (71.1%), married (41.1%), holders of low levels of education in which only 63.3% frequented / completed the 1st cycle of primary and almost entirely retired (88.9%). It is found that 77.8% of the elderly perceive their general health as fair or good. Likewise, 86.7% of individuals have altered vision mainly due to the change in visual acuity away (86.7%),up to 65.5% of eyes had a visual acuity of 5/10 or greater. Other dimensions that contributed to the alteration of visual function include contrast sensitivity (63.3%), stereopsis (51.1%), color vision (38.9%) and ocular motility (25.6%). There was thus obtained the highest scores for different scales of the questionnaire VFQ-25 in patients with altered vision except for scales related to near activities, driving and dependence. It is therefore a relationship between alteration in visual function and disturbance of quality of life related to health. To question for the elderly, 42.6% expressed no reason to see evil/feel difficulty seeing over the last year. The decrease in visual acuity for distance/near was reported by 20.5% of subjects, followed by the deterioration of general health and eye for 15%. The responses of medical specialists in general practice about reasons for the suspicion/diagnosis relatively late disturbance of visual function, indicate the illiteracy of the elderly for healthy vision and ocular semiology (34%), low education/information for Doctors in the health of vision (22%) and poor accessibility and response timeconsuming/ inefficient NHS ophthalmology services (20%) as main reasons for the subjects questioned. Conclusion: Changes in the visual system with an impact on visual function and the functioning change the health related quality of life, mainly due to the change in distance visual acuity. Older people do not value the visual health perceiving the general health and eye health positively relatively of visual function. It is essential to define strategies and literacy programs for eye health for the entire population, not just for the elderly. It is suggested reconsider the model of basic training of Doctors with special focus on the health of the vision, with special needs sensed training/information. The responses of older people and doctors have indicated there is weakness in eye health, need to rethink the model of health care in this area. This research allowed the author to reflect on issues related to aging leading to a change in attitudes and behavior in professional approach to the elderly, promoting autonomy in choices and decisions in health issues, creating strategies to deal with the problem of vision and adaptation to new conditions of eye health.

A cross-cultural study on the effect of decimal separator on price perception

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics

Distance perception in immersive environments: the role of photorealism

Immersive environments (IE) are being increasingly used in order to perform psychophysical experiments. The versatility in terms of stimuli presentation and control and the less time-consuming procedures are their greatest strengths. However, to ensure that IE results can be generalized to real world scenarios we must first provide evidence that performance in IE is quantitatively indistinguishable from performance in real-world. Our goal was to perceptually validate distance perception for CAVE-like IEs. Participants performed a Frontal Matching Distance Task (Durgin & Li, 2011) in three different conditions: real-world scenario (RWS); photorealistic IE (IEPH) and non-photorealistic IE (IENPH). Underestimation of distance was found across all the conditions, with a significant difference between the three conditions (Wilks’ Lambda = .38, F(2,134)= 110.8, p<.01, significant pairwise differences with p<.01). We found a mean error of 2.3 meters for the RWS, 5 meters for the IEPH, and of 6 meters for the IENPH in a pooled data set of 5 participants. Results indicate that while having a photorealistic IE with perspective and stereoscopic depth cues might not be enough to elicit a real-world performance in distance judgment tasks, nevertheless this type of environment minimizes the discrepancy between simulation and real-world when compared with non-photorealistic IEs.

Percepción y uso de flora y fauna por parte de los pobladores del sistema Laguna Mar Chiquita - Bañados del Río Dulce y área de influencia: diagnóstico e implicaciones para la conservación. Perception and use of flora and fauna by people of the system "Laguna Mar Chiquita - Bañados del Río Dulce" and it influence area: diagnosis and conservation implications.

La percepción, consumo y manejo de recursos naturales forma parte del conocimiento tradicional de distintas poblaciones humanas e involucra diversidad de actividades (recolección de plantas, caza y pesca, etc). Entre los vegetales, el uso de plantas medicinales se destaca por su persistencia y ubicuidad. El recurso animal, a través de la caza y la pesca, es fundamental como fuente de alimento y empleo. El sistema Mar Chiquita-Bañados del Río Dulce se destaca por su biodiversidad y la existencia de prácticas tradicionales de uso. La presión por conversión de ambientes naturales a tierras dedicadas al cultivo es fuerte, afectando principalmente a los bosques autóctonos, y las especies animales que en él habitan. Además, la desaparición de ambientes naturales conlleva la pérdida de prácticas tradicionales de uso, con la consiguiente deculturación. El presente trabajo evaluará la percepción y utilización de recursos naturales por los pobladores del área de influencia de Bañados del Río Dulce y Laguna Mar Chiquita, centrándose en plantas medicinales, peces, aves y mamíferos, a la vez de indagar sobre la diversidad de percepciones y conductas de apropiación de los recursos, dado que en la región coexisten diferentes pautas socio-culturales de acuerdo al grupo de procedencia. Como metodología básica para la recolección de datos de percepción y uso se utilizarán encuestas semi-estructuradas. Sobre el origen étnico y lazos sociales se relevarán de fuentes escritas sobre procedencia, pautas de elección de pareja y formas de residencia. Los muestreos de fauna a campo se realizarán al azar estratificados en pastizal, bosque, y áreas relacionadas a humedales en busca de huellas, heces y señales de la presencia de especies animales focales, a la vez de prospección visual y auditiva. Los datos obtenidos acerca del conocimiento y uso del ambiente se presentarán y analizarán mediante técnicas específicas para análisis de datos antropológicos cualitativos y madiante ANOVA. Los datos sobre origen y lazos serán analizados según indicadores de endogamia geográfica e indicadores de endogamia reproductiva. Los datos de presencia de las especies se utilizarán para desarrollar modelos de distribución regional y de nicho ecológico. Se espera caracterizar en forma diferencial la percepción y uso del ambiente de acuerdo al origen o área de residencia, a la vez de generar mapas de distribución de especies focales. Asimismo, se propondrán acciones de conservación de la biodiversidad, tales como cartillas o talleres tendientes a reforzar y re-significar los conocimientos locales sobre el uso de flora y fauna.

Long-term fluctuation of relative afferent pupillary defect in subjects with normal visual function.

PURPOSE: To determine whether the relative afferent pupillary defect (RAPD) remains constant over time in normal subjects. METHODS: Seventeen normal subjects were tested with infrared pupillography and automated perimetry in four sessions over 3 years. The changes in RAPD and visual field asymmetry between testing sessions were compared. RESULTS: The range of RAPD was 0.0 to 0.3 log unit, and the difference in the mean deviation between the eyes on automated static perimetry was 0 to 3 dB. Eight subjects repeatedly had an RAPD in the same eye. There was no correlation between the RAPD and the visual field asymmetry at the same visit. Changes in the magnitude of the RAPD between any two sessions were typically small (median, 0.08 log unit; 25th percentile, 0.04 log unit; 75th percentile, 0.15 log unit). CONCLUSIONS: Some normal subjects may show a persistent but small RAPD in the absence of detectable pathologic disease. Therefore, an isolated RAPD in the range of 0.3 log unit that is not associated with any other significant historical or clinical finding should probably be considered benign.

Impaired early visual response modulations to spatial information in chronic schizophrenia.

Early visual processing stages have been demonstrated to be impaired in schizophrenia patients and their first-degree relatives. The amplitude and topography of the P1 component of the visual evoked potential (VEP) are both affected; the latter of which indicates alterations in active brain networks between populations. At least two issues remain unresolved. First, the specificity of this deficit (and suitability as an endophenotype) has yet to be established, with evidence for impaired P1 responses in other clinical populations. Second, it remains unknown whether schizophrenia patients exhibit intact functional modulation of the P1 VEP component; an aspect that may assist in distinguishing effects specific to schizophrenia. We applied electrical neuroimaging analyses to VEPs from chronic schizophrenia patients and healthy controls in response to variation in the parafoveal spatial extent of stimuli. Healthy controls demonstrated robust modulation of the VEP strength and topography as a function of the spatial extent of stimuli during the P1 component. By contrast, no such modulations were evident at early latencies in the responses from patients with schizophrenia. Source estimations localized these deficits to the left precuneus and medial inferior parietal cortex. These findings provide insights on potential underlying low-level impairments in schizophrenia.

Dynamic visual information plays a critical role for spatial navigation in water but not on solid ground.

In the Morris water maze (MWM) task, proprioceptive information is likely to have a poor accuracy due to movement inertia. Hence, in this condition, dynamic visual information providing information on linear and angular acceleration would play a critical role in spatial navigation. To investigate this assumption we compared rat's spatial performance in the MWM and in the homing hole board (HB) tasks using a 1.5 Hz stroboscopic illumination. In the MWM, rats trained in the stroboscopic condition needed more time than those trained in a continuous light condition to reach the hidden platform. They expressed also little accuracy during the probe trial. In the HB task, in contrast, place learning remained unaffected by the stroboscopic light condition. The deficit in the MWM was thus complete, affecting both escape latency and discrimination of the reinforced area, and was thus task specific. This dissociation confirms that dynamic visual information is crucial to spatial navigation in the MWM whereas spatial navigation on solid ground is mediated by a multisensory integration, and thus less dependent on visual information.

Visual search in spatial neglect studied with a preview paradigm.

Impaired visual search is a hallmark of spatial neglect. When searching for an unique feature (e.g., color) neglect patients often show only slight visual field asymmetries. In contrast, when the target is defined by a combination of features (e.g., color and form) they exhibit a severe deficit of contralesional search. This finding suggests a selective impairment of the serial deployment of spatial attention. Here, we examined this deficit with a preview paradigm. Neglect patients searched for a target defined by the conjunction of shape and color, presented together with varying numbers of distracters. The presentation time was varied such that on some trials participants previewed the target together with same-shape/different-color distracters, for 300 or 600 ms prior to the appearance of additional different-shape/same-color distracters. On the remaining trials the target and all distracters were shown simultaneously. Healthy participants exhibited a serial search strategy only when all items were presented simultaneously, whereas in both preview conditions a pop-out effect was observed. Neglect patients showed a similar pattern when the target was presented in the right hemifield. In contrast, when searching for a target in the left hemifield they showed serial search in the no-preview condition, as well as with a preview of 300 ms, and partly even at 600 ms. A control experiment suggested that the failure to fully benefit from item preview was probably independent of accurate perception of time. Our results, when viewed in the context of existing literature, lead us to conclude that the visual search deficit in neglect reflects two additive factors: a biased representation of attentional priority in favor of ipsilesional information and exaggerated capture of attention by ipsilesional abrupt onsets.

Copwatching et perception publique de la police. L'intervention policière comme performance sous surveillance

Envisagée comme une situation sociale de rassemblement en rue, l'intervention policière se caractérise par sa nature publique et observable. Le « copwatching », en tant que pratique amateur de captation vidéo des interventions de police, problématise la visibilité des agents sur la voie publique en les soumettant à une surveillance médiatique. M'appuyant sur des exemples vidéos, j'explore les dimensions visuelles et symboliques du travail policier. De la performance policière en rue à la figuration médiatique du policier, l'étude des médiations entre action et image permet d'interroger la perception publique de la police engagée dans les rassemblements. Abstract Cop-watching and the public perception of the police. Police intervention as performance under surveillance. This paper deals with police work as a public performance on the street. Cop-watching, a way of publicly observing and documenting police activities, reveals the complex relationship between public perceptions of law enforcement and the visual nature of much police work. Three methodological approaches to cop-watching videos allow us to highlight the visual dimensions of police work : the study of mass-media images of cops, the study of street performance by real cops, and the study of the ways people make sense of the visual symbolic environment present in everyday police work.

WMR navigation using local potential field corridors and narrow local occupancy grid perception

Path planning and control strategies applied to autonomous mobile robots should fulfil safety rules as well as achieve final goals. Trajectory planning applications should be fast and flexible to allow real time implementations as well as environment interactions. The methodology presented uses the on robot information as the meaningful data necessary to plan a narrow passage by using a corridor based on attraction potential fields that approaches the mobile robot to the final desired configuration. It employs local and dense occupancy grid perception to avoid collisions. The key goals of this research project are computational simplicity as well as the possibility of integrating this method with other methods reported by the research community. Another important aspect of this work consist in testing the proposed method by using a mobile robot with a perception system composed of a monocular camera and odometers placed on the two wheels of the differential driven motion system. Hence, visual data are used as a local horizon of perception in which trajectories without collisions are computed by satisfying final goal approaches and safety criteria

Robust decoupled visual servoing based on structured light

This paper focuses on the problem of realizing a plane-to-plane virtual link between a camera attached to the end-effector of a robot and a planar object. In order to do the system independent to the object surface appearance, a structured light emitter is linked to the camera so that 4 laser pointers are projected onto the object. In a previous paper we showed that such a system has good performance and nice characteristics like partial decoupling near the desired state and robustness against misalignment of the emitter and the camera (J. Pages et al., 2004). However, no analytical results concerning the global asymptotic stability of the system were obtained due to the high complexity of the visual features utilized. In this work we present a better set of visual features which improves the properties of the features in (J. Pages et al., 2004) and for which it is possible to prove the global asymptotic stability

Plane-to-plane positioning from image-based visual servoing and structured light

In this paper we face the problem of positioning a camera attached to the end-effector of a robotic manipulator so that it gets parallel to a planar object. Such problem has been treated for a long time in visual servoing. Our approach is based on linking to the camera several laser pointers so that its configuration is aimed to produce a suitable set of visual features. The aim of using structured light is not only for easing the image processing and to allow low-textured objects to be treated, but also for producing a control scheme with nice properties like decoupling, stability, well conditioning and good camera trajectory

Emotional attention as a modulatory system of perception

Report for the scientific sojourn carried out at the University Medical Center, Swiss, from 2010 to 2012. Abundant evidence suggests that negative emotional stimuli are prioritized in the perceptual systems, eliciting enhanced neural responses in early sensory regions as compared with neutral information. This facilitated detection is generally paralleled by larger neural responses in early sensory areas, relative to the processing of neutral information. In this sense, the amygdala and other limbic regions, such as the orbitofrontal cortex, may play a critical role by sending modulatory projections onto the sensory cortices via direct or indirect feedback.The present project aimed at investigating two important issues regarding these mechanisms of emotional attention, by means of functional magnetic resonance imaging. In Study I, we examined the modulatory effects of visual emotion signals on the processing of task-irrelevant visual, auditory, and somatosensory input, that is, the intramodal and crossmodal effects of emotional attention. We observed that brain responses to auditory and tactile stimulation were enhanced during the processing of visual emotional stimuli, as compared to neutral, in bilateral primary auditory and somatosensory cortices, respectively. However, brain responses to visual task-irrelevant stimulation were diminished in left primary and secondary visual cortices in the same conditions. The results also suggested the existence of a multimodal network associated with emotional attention, presumably involving mediofrontal, temporal and orbitofrontal regions Finally, Study II examined the different brain responses along the low-level visual pathways and limbic regions, as a function of the number of retinal spikes during visual emotional processing. The experiment used stimuli resulting from an algorithm that simulates how the visual system perceives a visual input after a given number of retinal spikes. The results validated the visual model in human subjects and suggested differential emotional responses in the amygdala and visual regions as a function of spike-levels. A list of publications resulting from work in the host laboratory is included in the report.