Showing papers by "Sabry F. El-Hakim published in 1995"

Comparative evaluation of the performance of passive and active 3D vision systems

Abstract: Automated digital photogrammetric systems are considered to be passive three-dimensional vision systems since they obtain object coordinates from only the information contained in intensity images. Active 3-D vision systems, such as laser scanners and structured light systems obtain the object coordinates from external information such as scanning angle, time of flight, or shape of projected patterns. Passive systems provide high accuracy on well defined features, such as targets and edges however, unmarked surfaces are hard to measure. These systems may also be difficult to automate in unstructured environments since they are highly affected by the ambient light. Active systems provide their own illumination and the features to be measured so they can easily measure surfaces in most environments. However, they have difficulties with varying surface finish or sharp discontinuities such as edges. Therefore each type of sensor is more suited for a specific type of objects and features, and they are often complementary. This paper compares the measurement accuracy, as applied to various type of features, of some technologically-different 3-D vision systems: photogrammetry-based (passive) systems, a laser scanning system (active), and a range sensor using a mask with two apertures and structured light (active).

Configuration design for sensor integration

Abstract: Due to the nature of many applications, it is difficult with present technology to use a single type of sensor to automatically, accurately, reliably, and completely measure or map, in 3D, objects, sites, or scenes. Therefore, a combination of various sensor technologies is usually the obvious solution. There are several 3D technologies, two of which; digital photogrammetry and triangulation laser scanning, are dealt with in this paper. The final accuracy achieved by the combination of various sensors is a factor of many sensor parameters and the quality of the image coordinate measurements of each sensor. The effect of those parameters must be determined to maximize the overall quality within the constraints imposed by the requirements of the application. The parameters affecting the accuracy of measurement, the test laboratory, and test results using intensity and range data, are presented. The configuration design of intensity and range sensors is discussed based on the results presented here and in two previous papers.