The electrical stimulation of appropriate components of the human visual system can result in the perception of blobs of light (or phosphenes) in totally blind patients. By stimulating an array of closely aligned electrodes it is possible for a patient to perceive very low-resolution images from spatially aligned phosphenes. Using this approach, a number of international research groups are working toward developing multiple electrode systems (called Artificial Human Vision (AHV) systems or visual prostheses) to provide a phosphene-based substitute for normal human vision. Despite the great promise, there are currently a number of constraints with current AHV systems. These include limitations in the number of electrodes which can be implanted and the perceived spatial layout and display frequency of phosphenes. Therefore the development of computer vision techniques that can maximise the visualisation value of the limited number of phosphenes would be useful in compensating for these constraints. The lack of an objective method for comparing different AHV system displays, in addition to comparing AHV systems and other blind mobility aids (such as the long cane), has been a significant problem for AHV researchers. Finally, AHV research in Australia and many other countries relies strongly on theoretical models and animal experimentation due to the difficult of prototype human trials. Because of this constraint the experiments conducted in this thesis were limited to simulated AHV devices with normally sighted research participants and the true impact on blind people can only be regarded as approximated. In light of these constraints, this thesis has two general aims. The first aim is to investigate, evaluate and develop effective techniques for mobility assessment which will allow the objective comparison of different AHV system phosphene presentation methods. The second aim is to develop a useful display framework to guide the development of AHV information presentation, and use this framework to guide the development of an AHV simulation device. The first research contribution resulting from this work is a conceptual framework based on literature reviews of blind and low vision mobility, AHV technology, and computer vision. This framework incorporates a comprehensive number of factors which affect the effectiveness of information presentation in an AHV system. Experiments reported in this thesis have investigated a number of these factors using simulated AHV with human participants. It has been found that higher spatial resolution is associated with accurate walking (reduced veering), whereas higher display rate is associated with faster walking speeds. In this way it has been demonstrated that the conceptual framework supports and guides the development of an adaptive AHV system, with the dynamic adjustment of display properties in real-time. The second research contribution addresses mobility assessment which has been identified as an important issue in the AHV literature. This thesis presents the adaptation of a mobility assessment method from the blind and low vision literature to measure simulated AHV mobility performance using real-time computer based analysis. This method of mobility assessment (based on parameters for walking speed, obstacle contacts and veering) is demonstrated experimentally in two different indoor mobility courses. These experiments involved sixty-five participants wearing a head-mounted simulation device. The final research contribution in this thesis is the development and evaluation of an original real-time looming obstacle detector, based on coarse optical flow, and implemented on a Windows PocketPC based Personal Digital Assistant (PDA) using a CF card camera. PDA based processors are a preferred main processing platform for AHV systems due to their small size, light weight and ease of software development. However, PDA devices are currently constrained by restricted random access memory, lack of a floating point unit and slow internal bus speeds. Therefore any real-time software needs to maximise the use of integer calculations and minimise memory usage. This contribution was significant as the resulting device provided a selection of experimental results and subjective opinions.

[pt] A dificuldade de locomoção de pedestres cegos é um problema complexo constituído das dificuldades de percepção e de orientação. Parte da dificuldade de percepção é identificar pontos de referência, que é necessário para que indivíduos montem uma representação do espaço, orientem-se nesse espaço e definam trajetórias para se locomover. Nessa pesquisa, foram desenvolvidos e investigados wearables para apoiar indivíduos cegos a identificar pontos de referência. O primeiro Estudo de Caso foi realizado para investigar uma maneira de evitar o masking, problema causado pela tecnologia que consiste numa sobrecarga cognitiva e no prejuízo temporário da capacidade do indivíduo de sensoriar o ambiente com seus sentidos. Para investigar o masking, foram realizados Estudos de Caso com participantes cegos e wearables propostos nessa pesquisa. A partir dos estudos, conclui-se que o wearable dessa pesquisa foi bem sucedido em evitar o masking e essa abordagem foi considerada uma alternativa válida para pesquisadores que investigam esse problema em outros contextos. No segundo Estudo de Caso, já com o masking controlado, concluiu-se que o wearable proposto nessa pesquisa possibilita aos indivíduos cegos explorar mais pontos de referência em relação à exploração exclusivamente com a bengala. Essa pesquisa contribui também com um conjunto de recomendações para projetistas de wearables para mobilidade de cegos. / [en] The difficulty in the locomotion of blind pedestrians is a complex problem that comprises the difficulties of perception and orientation. Part of the difficulty of perception is the identification of landmarks, which is necessary for the orientation process and also the acquisition of a spatial representation. The spatial representation will be used later when orientating in this space and for defining paths to move from a given place to another. In this research, wearables were investigated aiming at supporting blind persons in the task of identifying of landmarks. The first step was to investigate a way to avoid masking, a problem caused by technology that is characterized by a cognitive overload and the harmful interference of technology in the wearer’s capabilities of sensing the environment through their senses. In order to investigate masking, a Case Study was designed and carried out with a group of blind subjects. As a result, the wearable succeeded in avoiding masking. The approach used is considered useful as an alternative for researchers that investigate this problem in other contexts. Besides avoiding the masking, the proposed wearable enabled blind individuals explore more landmarks when compared to the approach of exploring with a white cane. Furthermore, this research also contributes with a set of recommendations for designers of wearables for blind mobility.