The position of a substrate's edge is detected using a substrate alignment system that includes, in part, a light source, an optical module adapted to receive a light emanating from the light source to form a multi-dimensional light beam; and an array sensor positioned at a focal plane of the optical module and oriented substantially perpendicular to the sample's edge. The substrate alignment system detects the substrate's edge position as soon as the substrate is loaded and placed within the capture range of the linear array sensor. As long as the substrate's edge position is within the capture range, the substrate does not have to be moved to determine its position relative to the tool's coordinate space. The capture range is substantially larger than the position accuracy required. The sensor array includes a multitude of sensors disposed along one or more rows.