Abstract
A microcomputer based measurement system of 3-D motion has been devised using a pair of position sensing detector (PSD) cameras, which monitors movements of LEDs attached to various places on a moving object. The system employs a novel method for determinations of camera parameters (position and orientation of each camera relative to the objective space) by displaying an LED moving along three lines of known orientations in the space in advance to measurements, which effects to exclude measurement errors due to inaccurate presetting of each camera at a specified position. It also enables to set cameras on any appropriate places so that they can monitor whole movements of LEDs without being hidden by other part of moving object. Resultant determination error of orientation of camera axis proved less than one third of a degree.
Other various techniques are employed to improve measurement accuracy and to reduce noise, including real time correction of spatial distortion of position outputs of the PSD cameras. Average measurement error and minimum detectable displacement (noise) proved less than 0.5mm over central cubic region (with 40cm edges) and less than 1.0mm over peripheral region (inside a cube with 60cm edges excluding the central region) with an inter axes angle of 60° between cameras and with a distance of 2m between an origine of the space and each camera. Time for measuring a point and calculating its position are 3.5msec and 230msec, respectively.
