Investigations On Human Perceptual Maps Using A Stereo-Vision Mobile Robot

Spatial cognition is a branch of cognitive psychology concerning the acquisition, organization, utilization, and revision of knowledge about spatial environments. A new computational theory of human spatial cognitive mapping has been proposed in the literature, and analyzed using a laser-based mobile robot. In contrast with the well-established SLAM (Simultaneous Localization and Mapping) approach that creates a precise and complete map of the environment, the proposed human perceptual map building procedure is more representative of spatial cognitive mapping in the human brain, whereby an imprecise and incomplete perceptual map of an environment can be created easily. The key steps in the methodology are capturing stereo-vision images of the environment, creating the tracked reference objects (TROs), tracking the number of remaining TROs, and expanding the map when the limiting points of the environment are reached. The main contribution of this research is on the use of computer vision techniques and computational mapping algorithms on a stereo-vision mobile robot for formulating the human perceptual map systematically, and evaluating the resulting human perceptual maps pertaining to both indoor and outdoor environments comprehensively. Validating the human perceptual maps using vision-based techniques is important for two reasons. Firstly, vision plays an important role in the development of human spatial cognition; secondly, computer vision systems are less expensive and information-rich in representing an environment. Specifically, computer vision techniques are first developed for analyzing the associated stereo images and retrieving the displacement information of a mobile robot, as well ascreating the necessary tracked reference objects. A number of computational mapping algorithms are then employed to build a human perceptual map of the environment in this research. Four real-world environments, namely two large indoor and two large outdoor environments, are empirically evaluated. The spatial geometry of the test environments vary, and the environments are subject to various natural effects including reflection and noise. The reflection and noise occurrin many parts of the images. Therefore, additional algorithms are developed in order to remove the reflection and noise. The removal of reflection and noise significantly reduces the number of TROs createdfor every immediate view. The outcomes indicate that the proposed computer vision techniques and computational mapping algorithms for human perceptual map building are robust and useful. They are able to create imprecise and incomplete human perceptual maps with good spatial representation of the overall environments. The map is imprecise and incomplete in the sense that it is not accurate in metric terms and has perceived surfaces missing. It is shown that both vision-based and the laser-based systems are able to computer a reasonably accurate spatial geometry of the tested environment

Optimal measurement of visual motion across spatial and temporal scales

Sensory systems use limited resources to mediate the perception of a great variety of objects and events. Here a normative framework is presented for exploring how the problem of efficient allocation of resources can be solved in visual perception. Starting with a basic property of every measurement, captured by Gabor's uncertainty relation about the location and frequency content of signals, prescriptions are developed for optimal allocation of sensors for reliable perception of visual motion. This study reveals that a large-scale characteristic of human vision (the spatiotemporal contrast sensitivity function) is similar to the optimal prescription, and it suggests that some previously puzzling phenomena of visual sensitivity, adaptation, and perceptual organization have simple principled explanations.Comment: 28 pages, 10 figures, 2 appendices; in press in Favorskaya MN and Jain LC (Eds), Computer Vision in Advanced Control Systems using Conventional and Intelligent Paradigms, Intelligent Systems Reference Library, Springer-Verlag, Berli

On the Stability of Region Count in the Parameter Space of Image Analysis Methods

In this dissertation a novel bottom-up computer vision approach is proposed. This approach is based upon quantifying the stability of the number of regions or count in a multi-dimensional parameter scale-space. The stability analysis comes from the properties of flat areas in the region count space generated through bottom-up algorithms of thresholding and region growing, hysteresis thresholding, variance-based region growing. The parameters used can be threshold, region growth, intensity statistics and other low-level parameters. The advantages and disadvantages of top-down, bottom-up and hybrid computational models are discussed. The approaches of scale-space, perceptual organization and clustering methods in computer vision are also analyzed, and the difference between our approach and these approaches is clarified. An overview of our stable count idea and implementation of three algorithms derived from this idea are presented. The algorithms are applied to real-world images as well as simulated signals. We have developed three experiments based upon our framework of stable region count. The experiments are using flower detector, peak detector and retinal image lesion detector respectively to process images and signals. The results from these experiments all suggest that our computer vision framework can solve different image and signal problems and provide satisfactory solutions. In the end future research directions and improvements are proposed

Boundary Extraction in Images Using Hierarchical Clustering-based Segmentation

Hierarchical organization is one of the main characteristics of human segmentation. A human subject segments a natural image by identifying physical objects and marking their boundaries up to a certain level of detail [1]. Hierarchical clustering based segmentation (HCS) process mimics this capability of the human vision. The HCS process automatically generates a hierarchy of segmented images. The hierarchy represents the continuous merging of similar, spatially adjacent or disjoint, regions as the allowable threshold value of dissimilarity between regions, for merging, is gradually increased. HCS process is unsupervised and is completely data driven. This ensures that the segmentation process can be applied to any image, without any prior information about the image data and without any need for prior training of the segmentation process with the relevant image data. The implementation details of HCS process have been described elsewhere in the author's work [2]. The purpose of the current study is to demonstrate the performance of the HCS process in outlining boundaries in images and its possible application in processing medical images. [1] P. Arbelaez. Boundary Extraction in Natural Images Using Ultrametric Contour Maps. Proceedings 5th IEEE Workshop on Perceptual Organization in Computer Vision (POCV'06). June 2006. New York, USA. [2] A. N. Selvan. Highlighting Dissimilarity in Medical Images Using Hierarchical Clustering Based Segmentation (HCS). M. Phil. dissertation, Faculty of Arts Computing Engineering and Sciences Sheffield Hallam Univ., Sheffield, UK, 2007.</p

A Framework for Symmetric Part Detection in Cluttered Scenes

The role of symmetry in computer vision has waxed and waned in importance during the evolution of the field from its earliest days. At first figuring prominently in support of bottom-up indexing, it fell out of favor as shape gave way to appearance and recognition gave way to detection. With a strong prior in the form of a target object, the role of the weaker priors offered by perceptual grouping was greatly diminished. However, as the field returns to the problem of recognition from a large database, the bottom-up recovery of the parts that make up the objects in a cluttered scene is critical for their recognition. The medial axis community has long exploited the ubiquitous regularity of symmetry as a basis for the decomposition of a closed contour into medial parts. However, today's recognition systems are faced with cluttered scenes, and the assumption that a closed contour exists, i.e. that figure-ground segmentation has been solved, renders much of the medial axis community's work inapplicable. In this article, we review a computational framework, previously reported in Lee et al. (2013), Levinshtein et al. (2009, 2013), that bridges the representation power of the medial axis and the need to recover and group an object's parts in a cluttered scene. Our framework is rooted in the idea that a maximally inscribed disc, the building block of a medial axis, can be modeled as a compact superpixel in the image. We evaluate the method on images of cluttered scenes.Comment: 10 pages, 8 figure

The constitution of visual perceptual units in the functional architecture of V1

Scope of this paper is to consider a mean field neural model which takes into account the functional neurogeometry of the visual cortex modelled as a group of rotations and translations. The model generalizes well known results of Bressloff and Cowan which, in absence of input, accounts for hallucination patterns. The main result of our study consists in showing that in presence of a visual input, the eigenmodes of the linearized operator which become stable represent perceptual units present in the image. The result is strictly related to dimensionality reduction and clustering problems