Structured light based reconstruction under local spatial coherence assumption

3D scanning techniques based on structured light usually achieve robustness against outliers by performing multiple projections to simplify correspondence. However, for cases such as dynamic scenes, the number of frames captured from a certain view must be kept as low as possible, which makes it difficult to reconstruct complex scenes with high frequency shapes and inappropriate reflection properties. To tackle this problem, we present a novel set of color stripe patterns and a robust correspondence algorithm that assume local spatial coherence in the captured data. This assumption allows us to design our stripe sequences with globally unique neighborhood properties to effectively avoid wrong correspondences. The concept of local spatial coherence is further exploited to make the ensuing surface reconstruction practically insensitive to noise, outliers, and anisotropic sampling density. Thus, the recovery of a topologically consistent manifold surface can be drastically simplified. We have successfully generated high quality meshes of various colored objects using a minimalistic projector-camera system. In particular, the full sampling capabilities of our devices can be exhausted by taking only three shots. 1

Novel Approaches in Structured Light Illumination

Among the various approaches to 3-D imaging, structured light illumination (SLI) is widely spread. SLI employs a pair of digital projector and digital camera such that the correspondences can be found based upon the projecting and capturing of a group of designed light patterns. As an active sensing method, SLI is known for its robustness and high accuracy. In this dissertation, I study the phase shifting method (PSM), which is one of the most employed strategy in SLI. And, three novel approaches in PSM have been proposed in this dissertation. First, by regarding the design of patterns as placing points in an N-dimensional space, I take the phase measuring profilometry (PMP) as an example and propose the edge-pattern strategy which achieves maximum signal to noise ratio (SNR) for the projected patterns. Second, I develop a novel period information embedded pattern strategy for fast, reliable 3-D data acquisition and reconstruction. The proposed period coded phase shifting strategy removes the depth ambiguity associated with traditional phase shifting patterns without reducing phase accuracy or increasing the number of projected patterns. Thus, it can be employed for high accuracy realtime 3-D system. Then, I propose a hybrid approach for high quality 3-D reconstructions with only a small number of illumination patterns by maximizing the use of correspondence information from the phase, texture, and modulation data derived from multi-view, PMP-based, SLI images, without rigorously synchronizing the cameras and projectors and calibrating the device gammas. Experimental results demonstrate the advantages of the proposed novel strategies for 3-D SLI systems

The influence of skeletal size on age-related criteria from the pelvic joints in Portuguese and North American samples

Estimating age of death for adult skeletons with accuracy is still one of the chief predicaments in bioanthropology. It has been recognized that methods’ inaccurate results from the lack of a better understanding of the ageing process and associated confounding factors. In the present study was investigated if body size (measured by stature, body mass, robusticity and articulation size) affects age-related morphological criteria of the pubic symphysis, auricular surface of the iliac and acetabulum. Adult individuals of both sexes with age at death superior to 17 years old were analysed from the Identified Skeletal Collection from the University of Coimbra (Portugal), and the William Bass Donated Skeletal Collection (USA). Three levels of analysis were followed to evaluate joints degeneration: individual traits, components (weighted linear clustering of correlated traits) and a composite score (sum of all the scores across all characters). Furthermore, stature, body mass and robusticity were computed through femoral measurements, and the surface area of the pelvic joints were calculated from three-dimensional digital polygon objects created with a white light scanner. A logistic regression analysis was carried out, showing especially body mass, stature and joint surface area affect some of the morphological criteria at the pelvic joints. Robusticity has a minimum effect on the pelvic joints metamorphosis. Results suggest that smaller individuals tend to age slower, with the transition from a “younger” to an “older” stage occurring at an older age compared with bigger individuals. Different patterns were obtained between population samples, possibly due to body size and age distributions differences between collections, or due to the complex and variable effect body size has in bone degeneration. The present research shows that body size influences the pelvic joints age-related criteria, which is important to incorporate in future age at death estimation methods