2727051
Anomaly detection through registration
We study an application of image registration in the medical domain. Based on a 3-D hierarchical deformable registration algorithm, we have developed a prototype system which automatically aligns a standard atlas to a subject's data to create a customized atlas. Combined with domain knowledge, the registration algorithm can also detect asymmetries and abnormal variations in the subject's data that indicate the existence and location of pathologies. We have conducted tests on 106 MRI scans of normal brains, 3 MRI and 1 CT scan of brains with pathologies, with results qualitatively comparable to manual segmentation.
31729209
Recognizing upper face action units for facial expression analysis
We develop an automatic system to analyze subtle changes in upper face expressions based on both permanent facial features (brows, eyes, mouth) and transient facial features (deepening of facial furrows) in a nearly frontal image sequence. Our system recognizes fine-grained changes in facial expression based on Facial Action Coding System (FACS) action units (AUs). Multi-state facial component models are proposed for tracting and modeling different facial features, including eyes, brews, cheeks, and furrows. Then we convert the results of tracking to detailed parametric descriptions of the facial features. These feature parameters are fed to a neural network which recognizes 7 upper face action units. A recognition rate of 95% is obtained for the test data that include both single action units and AU combinations.
27173839
Constructing virtual worlds using dense stereo
We present Virtualized Reality, a technique to create virtual worlds out of dynamic events using densely distributed stereo views. The intensity image and depth map for each camera view at each time instant are combined to form a Visible Surface Model. Immersive interaction with the virtualized event is possible using a dense collection of such models. Additionally, a Complete Surface Model of each instant can be built by merging the depth maps from different cameras into a common volumetric space. The corresponding model is compatible with traditional virtual models and can be interacted with immersively using standard tools. Because both VSMs and CSMs are fully three-dimensional, virtualized models can also be combined and modified to build larger, more complex environments, an important capability for many non-trivial applications. We present results from 3D Dome, our facility to create virtualized models.
6728834
Robust full-motion recovery of head by dynamic templates and re-registration techniques
This paper presents a method to recover the full-motion (3 rotations and 3 translations) of the head using a cylindrical model. The robustness of the approach is achieved by a combination of three techniques. First, we use the iteratively re-weighted least squares (IRLS) technique in conjunction with the image gradient to deal with non-rigid motion and occlusion. Second, while tracking, the templates are dynamically updated to diminish the effects of self-occlusion and gradual lighting changes and keep tracking the head when most of the face is not visible. Third, because the dynamic templates may cause error accumulation, we re-register images to a reference frame when head pose is close to a reference pose. The performance of the real-time tracking program was evaluated in three separate experiments using image sequences (both synthetic and real) for which ground truth head motion is known. The real sequences included pitch and yaw of as large as 40/spl deg/ and 75/spl deg/ respectively. The average recovery accuracy of the 3D rotations was found to be about 3/spl deg/.
941787
Optical Navigation by the Method of Differences
The method of differences refers to a technique for image matching that uses the intensity gradient of the image to iteratively improve the match between the two images. Used in an iterative scheme combined with image smoothing, the method exhibits good accuracy and a wide convergence range. In this paper we show how the technique ran be used to directly solve for the parameters relating two cameras viewing the same scene. The resulting algorithm can be used for optical navigation, which has applications in robot arm guidance and autonomous roving vehicle navigation. Because of the regular structure of the algorithm, the prospects of carrying it out with specialpurpose hardware for real-time control of a robot seem good. We present experimental results demonstrating the accuracy and range of convergence that can be expected from the algorithm.
2442998
Image-consistent surface triangulation
Given a set of 3D points that we know lie on the surface of an object, we can define many possible surfaces that pass through all of these points. Even when we consider only surface triangulations, there are still an exponential number of valid triangulations that all fit the data. Each triangulation will produce a different faceted surface connecting the points. Our goal is to overcome this ambiguity and find the particular surface that is closest to the true object surface. We do not know the true surface but instead we assume that we have a set of images of the object. We propose selecting a triangulation based on its consistency with this set of images of the object. We present an algorithm that starts with an initial rough triangulation and refines the triangulation until it obtains a surface that best accounts for the images of the object. Our method is thus able to overcome the surface ambiguity problem and at the same time capture sharp corners and handle concave regions and occlusions. We show results for a few real objects.
17343403
Ambler: an autonomous rover for planetary exploration
The authors are building a prototype legged rover, called the Ambler (loosely an acronym for autonomous mobile exploration robot) and testing it on full-scale, rugged terrain of the sort that might be encountered on the Martian surface. They present an overview of their research program, focusing on locomotion, perception, planning, and control. They summarize some of the most important goals and requirements of a rover design and describe how locomotion, perception, and planning systems can satisfy these requirements. Since the program is relatively young (one year old at the time of writing) they identify issues and approaches and describe work in progress rather than report results. It is expected that many of the technologies developed will be applicable to other planetary bodies and to terrestrial concerns such as hazardous waste assessment and remediation, ocean floor exploration, and mining.<<ETX>>