Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 64-66). Also available in electronic version. Access restricted to campus users.

A tridimensional optical display is described which is capable of producing real images with no optics between the observer and the image. This display, which is called the Visually Integrated Volumetric Image (VIVID), was developed as a laboratory system designed to be used in vision research. Three dimensional Lissajous patterns were produced, whose rotational position and axial depth could be precisely controlled by a general purpose digital minicomputer. By reversing the direction of rotation of the pattern in a known manner, and recording a subject's ability to perceive the true rotational direction for various amounts of axial image depth, the transition between the kinetic depth effect and true depth perception could be investigated. This transition forms the basis for defining a depth perception threshold for this type of a dynamic three dimensional image. Two experiments were performed using this approach. In the first experiment, ten undergraduate and graduate students (both male and female) observed the pattern during 24 one-minute trials. Eight different axial depth values were used, with three trials at each depth. The patterns were made to reverse rotation direction in a pseudo-random manner which was different for each trial presented to a given subject. The subject indicated the perceived direction of rotation by controlling a two position rotary switch, which was monitored by the computer. The total time during which the subject correctly tracked the rotation was integrated by the computer. The ratio of this correct tracking time to the total trial time was taken as a measure of the subject's ability to perceive the axial depth of the image. Plots of this ratio as a function of image depth are presented and discussed. The results averaged over all subjects produce a remarkably smooth curve, yielding a depth perception threshold of 2 mm for the subject population under the given experimental conditions. The characteristics of the stimulus were: (a) 2 cm high by 2 cm wide pattern; (b) Lissajous pattern frequency ratio of 6:1; (c) Axial distance from observer of 55 cm; (d) Wavelength of 533 nm (green); (e) Horizontal rotation axis; (f) Rotation period of 7 seconds; (g) Neutral background field illumination over a 40° come angle; (h) Image line width of 0.5 mm. The second experiment was a pilot experiment designed to investigate the effect of wavelength variations on this form of depth perception. A single subject was presented with a total of 192 one-minute trials at four wavelengths spanning the visible region (i.e., 6 one-minute trials for each of eight depth values at each wavelength). No significant wavelength dependence was observed in this pilot experiment.

The traditional method of repairing damaged roads in Atlantic Canada has been to place a hot mix asphalt overlay over the existing road. Though this method provides a new, smooth wearing surface to drive on, it is merely a short term fix. With time, the cracks in the original pavement will reflect to the surface of the new pavement, resulting in failure of the overlay. An alternative option gaining more prominence is the use of a Full Depth Reclamation (FDR) technique, which involves pulverizing the flexible pavement, along with a portion of the underlying layer. This material is then stabilized and recompacted to produce a new base layer that is free of damage. Though FDR has been used for a number of years, there are still problems with variability in the strength of the materials in some projects. It is hypothesized that some of these problems are due to variability and poor quality in the reclaimed materials. It is believed that current pulverization methods contribute to the variability being observed in these materials. Two FDR projects employing different pulverization control methods were studied to examine how the consistency of the reclaimed materials can be improved through the use of a Ground Penetrating Radar (GPR) survey to map the variability in the depth of the pavement. Controlling the thickness ratio of asphalt concrete to granular base materials being pulverized was shown to improve the consistency of materials, properties, and performance. The second phase of this research project studied how improving the gradation of the reclaimed materials with the addition of a crusher dust might result in improved performance of stabilized base materials, in this case stabilized with expanded asphalt. The effect of construction variability on the improved materials was also studied by varying both the moisture content, and asphalt content from optimum conditions, as might be expected during construction. Results indicated that the quality of the stabilized FDR materials can be significantly improved by bringing the material gradation closer to the theoretical maximum density gradation. The performance of the stabilized materials can be affected by both the mixing moisture content, and the asphalt content used during stabilization. This suggests that effective quality control, and stricter specifications on the constructed product would result in more reliable, effective FDR pavements. / A study on the control of the consistency of pulverized FDR materials, as well as a study examining how to improve the performance of these pulverized materials.

This paper investigates two distinct, but related, topics in machine vision. The first is the effect of lighting on the performance of a 2D vision-based inspection system. The lighting component of machine vision has often been overlooked; an attempt was made to quantify the impact on existing machine vision algorithms. The second topic explores the applications of a data-rich 3D vision sensor that is capable of providing depth data in a wide range of ambient lightning conditions for industrial applications. A focus is placed on inspection systems with the depth data provided by the sensor. Three basic lighting geometries were compared quantitatively based on discriminant analysis in an inspection task that checked for the presence of J-clips on an aluminum carrier. Two different LabVIEW® machine vision algorithms were used to evaluate backlight, bright field and dark field illumination on their ability to minimize the span of the pass (clip present) and fail (clip absent) sample sets, as well as maximize the separation between these sample sets. Results showed that there were clear differences in performance with the different lighting geometries, with over a 30% change in performance. Although it has long been accepted that the choice of lighting for machine vision systems is not a trivial exercise, this paper provides a quantitative measure of the impact lighting has on the performance of feature-based machine vision. The Microsoft Kinect® is a commercial vision sensor that can simultaneously provide a colour video stream, comparable to current webcam technologies, in addition to a depth stream that provides three-dimensional information of the camera’s field of view and is invariant to environmental lighting. An experiment was carried out to characterize the sensor’s accuracy and precision, and to evaluate its performance as an inspection system to determine the orientation of a wheel. Tests were also conducted to determine the effect that changes in the physical environment had on performance. These changes included camera height, lighting and surface material. Results of the experiment have shown that the sensor has an average precision of ±0.12 cm and average accuracy of 0.5 cm, both with less than a 30% change when varying physical features. A discriminant analysis was performed to measure inspection performance, which showed less than 30% change with set separation, but not for set span. No trends were apparent with the change in set span relating to the change in physical features. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-02-29 18:33:20.505

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Snow is a common overlying surface during winter-time and the redistribution of snow by wind is a very important concept for any hydrological research project located within the cryosphere. Wind redistributes snow by eroding it from areas of high wind speed, such as ridge tops and windward slopes, and deposits it in areas of lower wind speeds, such as the lees of ridge tops, vegetation stands, and topographic depressions. The accurate modelling of blowing snow processes such as erosion, deposition, and sublimation have proven to be rather problematic. The largest issue that many modellers must deal with is the accurate collection of solid precipitation throughout the winter season. Without this, incorrect energy and mass balances can occur. This thesis makes use of a new method of acquiring solid precipitation values through the use of an SR50a ultrasonic snow depth sensor and then incorporates it into a version of the Cold Regions Hydrological Model (CRHM) which includes the Prairie Blowing Snow Model (PBSM) and the Minimal Snowmelt Model (MSM) modules. The model is used to simulate seasonal snow depth over an agricultural field in southern Ontario, Canada and is driven with half-hourly locally acquired meteorological data for 83 days during the 2008-2009 winter season. Semi-automated snow surveys are conducted throughout the winter season and the collected in situ snow depth values are compared to the simulated snow depth values at multiple scales. Two modelling approaches are taken to temporally and spatially test model performance. A lumped approach tests the model‟s ability to simulate snow depth from a small point scale and from a larger field scale. A distributed approach separates the entire field site into three hydrological response units (HRUs) and tests the model‟s ability to spatially discretize at the field scale. HRUs are differentiated by varying vegetation heights throughout the field site. Temporal analysis compares the simulated results to each day of snow survey and for the entire field season. Model performance is statistically analyzed through the use of a Root Mean Square Difference (RMSD), Nash-Sutcliffe coefficient (NS), and Model Bias (MB). Both the lumped and distributed modelling approaches fail to simulate the early on-set of snow but once the snow-holding capacities are reached within the field site the model does well to simulate the average snow depth during the latter few days of snow survey as well as throughout the entire field season. Several model limitations are present which prevent the model from incorporating the scaling effects of topography, vegetation, and man-made objects as well as the effects from certain energy fluxes. These limitations are discussed further.

It is commonly known that stereopsis is the primary way for humans to perceive depth. Although, with one eye, we can still interact very well with our environment and do very highly skillful tasks by using other visual cues such as occlusion and motion, the resultant e ect of the absence of stereopsis is that the relative depth information between objects is essentially lost (Frisby,1979). While humans fuse the images seen by the left and right eyes in a seemingly easy way, the major problem - the correspondence of features - that needs to be solved in all binocular stereo systems of machine vision is not trivial. In this thesis, line segments and corners are chosen to be the features to be matched because they typically occur at object boundaries, surface discontinuities, and across surface markings. Polygonal regions are also selected since they are known to be well-configured and are, very often, associated with salient structures in the image. The use of these high level features, although helping to diminish matching ambiguities, does not completely resolve the matching problem when the scene contains repetitive structures. The spatial relationships between the feature matching pairs enforced in the stereo matching process, as proposed in this thesis, are found to provide even stronger support for correct feature matching pairs and, as a result, incorrect matching pairs can be largely eliminated. Getting global and salient 3D structures has been an important prerequisite for environmental modelling and understanding. While research on postprocessing the 3D information obtained from stereo has been attempted (Ayache and Faugeras, 1991), the strategy presented in this thesis for retrieving salient 3D descriptions is propagating the prominent information extracted from the 2D images to the 3D scene. Thus, the matching of two prominent 2D polygonal regions yields a prominent 3D region, and the inter-relation between two 2D region matching pairs is passed on and taken as a relationship between two 3D regions. Humans, when observing and interacting with the environment do not confine themselves to the observation and then the analysis of a single image. Similarly stereopsis can be vastly improved with the introduction of additional stereo image pairs. Eye, head, and body movements provide essential mobility for an active change of viewpoints, the disocclusion of occluded objects, the avoidance of obstacles, and the performance of any necessary tasks on hand. This thesis presents a mobile stereo vision system that has its eye movements provided by a binocular head support and stepper motors, and its body movements provided by a mobile platform, the Labmate. With a viewer centred coordinate system proposed in this thesis the computation of the 3D information observed at each individual viewpoint, the merging of the 3D in formation at consecutive viewpoints for environmental reconstruction, and strategies for movement control are discussed in detail.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains iv, 64 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 31-32).

Thesis (Ph.D.). / Written for the School of Computer Science. Title from title page of PDF (viewed 2008/05/12). Includes bibliographical references.

Thesis (Ph. D.)--Carleton University, 2004. / Includes bibliographical references (p. 109-119). Also available in electronic format on the Internet.