Our eyes are horizontally separated in the head by approximately 6.5cm. As a result of this separation there are subtle differences in the position of corresponding image points within the two eyes. The horizontal component of this binocular positional difference is termed horizontal disparity. Horizontal disparity is an important visual cue as once scaled with an estimate of the viewing distance, it can theoretically provide full metric information about the structure of the world. This thesis will address the issue of how binocular visual cues are used by the human visual system for the estimation of three-dimensional (3-D) shape for perception and visuomotor control. The research presented is particularly focused on understanding why biases in the perception of 3-D shape from binocular cues are found, their importance for perception and visuomotor control and how these biases may be overcome by combining binocular cues with other sources of visual information.

The research presented in this thesis was designed to investigate whether and how the temporal synchrony and spatial congruence of non-visual cues with visual targets could work together to improve the discrimination and identification of visual targets in neurologically-healthy adult humans. The speed and accuracy of participants’ responses were compared following the presence or absence of temporally synchronous and/or spatially congruent or incongruent auditory, vibrotactile, and audiotactile cues in the context of dynamic visual search and rapidly-masked visual target identification. The understanding of the effects of auditory, vibrotactile, and audiotactile cues derived from these laboratory-based tasks was then applied to an air traffic control simulation involving the detection and resolution of potential conflicts (represented as visual targets amidst dynamic and cluttered visual stimuli). The results of the experiments reported in this thesis demonstrate that, in the laboratory-based setting, temporally synchronous and spatially informative non-visual cues both gave rise to significant improvements in participants’ performance, and the combination of temporal and spatial cuing gave rise to additional improvements in visual target identification performance. In the real-world setting, however, only the temporally synchronous unimodal auditory and bimodal audiotactile cues gave rise to a consistent facilitation of participants’ visual target detection performance. The mechanisms and accounts proposed to explain the effects of spatial and temporal cuing, namely multisensory integration and attention, are examined and discussed with respect to the observed improvements in participants’ visual target identification performance.

The human visual system gathers information about three-dimensional object shape from a wide range of sources. How effectively we can use these sources, and how they are combined to form a consistent and accurate percept of the 3D world is the focus of much research. In complex scenes inter-reflections of light between surfaces (mutual illumination) can occur, creating chromatic illumination gradients. These gradients provide a source of information about 3D object shape, but little research has been conducted into the capabilities of the visual system to use such information. The experiments described here were conducted with the aim of understanding the influence of chromatic gradients from mutual illumination on 3D shape perception. Psychophysical experiments are described that were designed to investigate: If the human visual system takes account of mutual illumination when estimating 3D object shape, and how this might occur; How colour shading cues are integrated with other shape cues; The relative influence on 3D shape perception of achromatic (luminance) shading and chromatic shading from mutual illumination. In addition, one chapter explores a selection of mathematical models of cue integration and their applicability in this case. The results of the experiments suggest that the human visual system is able to quickly assess and take account of colour mutual illuminations when estimating 3D object shape, and use chromatic gradients as an independent and effective cue. Finally, mathematical modelling reveals that the chromatic gradient cue is likely integrated with other shape cues in a way that is close to statistically optimal.

Diss. (sammanfattning) Linköping : Linköpings universitet, 2006. / Härtill 5 uppsatser.

Thesis (PhD)--Macquarie University, Division of Society, Culture, Media & Philosophy, Department of Critical and Cultural Studies, 2005. / "2004". Bibliography: p. 315-327.

<p>Predmet disertacije jeste optimizacija digitalne slike kada<br />ograničenje nije vezano za način reprodukcije već za samog posmatrača,<br />odnosno optimizacija opaženog kvaliteta digitalne slike od strane<br />osoba sa poremećajima viđenja boja. Predloženi model optimizacije<br />slike poboljšava distinkciju boja i opseg boja slike za korisnike sa<br />različitim težinama poremećaja viđenja boja uz očuvanje prirodnosti<br />slike. Metodološki okvir ispitivanja, koji uključuje kvantitativnu<br />analizu računarskih simulacija, analizu eye-tracking podataka i<br />subjektivno ocenjivanje poboljšanja opaženog kvaliteta test slika,<br />daje sistematičnu i pouzdanu verifikaciju efektnosti predloženih<br />metoda adaptacije boja slike.</p> / <p>The subject of the thesis was the digital image optimization when an<br />observer represents the main image reproduction limitation or, in other<br />words, the optimization of the perceived image quality by individuals with<br />colour vision deficiencies. The proposed image optimization model enhances<br />colour distinction and gamut for users with different severities of colourblindness<br />while preserving the image naturalness. The used methodological<br />framework, including a quantitative analysis of computer simulations, an<br />analysis of eye-tracking data and a subjective evaluation of the perceived<br />image quality, provides systematic and reliable effectiveness verification of<br />the proposed colour adaptation methods.</p>

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