Abstract: A high-speed, 3-D method and system for optically measuring a geometric dimension of manufactured parts such as cartridge cases are provided. The method includes consecutively transferring the parts so that the parts travel along a path which extends to a vision station at which each part has a predetermined position and orientation for optical measuring. A line of radiation having a predetermined orientation is projected onto spaced apart end surfaces of the part to obtain reflected line segments of radiation from the end surfaces of the part. The reflected line segments of radiation are detected at one or more image planes to obtain electrical signals and the electrical signals are processed to determine the geometric dimension such as primer pocket depth.